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The analysis of isotope ratios in individual particles found in the environment is important to clarify the origins of the particles. In particular, the analysis of uranium particles in environmental samples from nuclear facilities is useful for detecting undeclared nuclear activities related to the production of nuclear weapons. Thermal ionization mass spectrometry (TIMS) combined with a fission track technique is an efficient method for determining the isotope ratios of individual uranium particles, but has a drawback called "particle-mixing". When some uranium particles are measured as a single particle and an average isotope ratiofor the particles is obtained, it is called "particle mixing". This may lead to erroneous conclusions in terms of the particle sources that are identified. In the present study, microsampling using a scanning electron microscope was added to the fission track-TIMS procedure. The analysis of a mixture of SRM 950a and CRM U100 reference materials containing uranium particles indicated that particle mixing was almost completely avoided using the proposed technique. The performance of the proposed method was sufficient for obtaining reliable data for the sources of individual particles to be identified reliably. [ABSTRACT FROM AUTHOR]

Able to detect known and unknown metabolites, untargeted metabolomics has shown great potential in identifying novel biomarkers. However, elucidating all possible liquid chromatography/time-of-flight mass spectrometry (LC/TOF-MS) ion signals in a complex biological sample remains challenging since many ions are not the products of metabolites. Methods of reducing ions not related to metabolites or simply directly detecting metabolite related (pure) ions are important. In this work, we describe PITracer, a novel algorithm that accurately detects the pure ions of a LC/TOF-MS profile to extract pure ion chromatograms and detect chromatographic peaks. PITracer estimates the relative mass difference tolerance of ions and calibrates the mass over charge (m/z) values for peak detection algorithms with an additional option tofurther mass correction with respect to a user-specified metabolite. PITracer was evaluated using two data sets containing 373 human metabolite standards, including 5 saturated standards considered to be split peaks resultant from huge m/z fluctuation, and 12 urine samples spiked with 50 forensic drugs of varying concentrations. Analysis of these data sets show that PITracer correctly outperformed existing state-of-art algorithm and extracted the pure ion chromatograms of the 5 saturated standards without generating split peaks and detected the forensic drugs with high recall, precision, and F-score and small mass error. [ABSTRACT FROM AUTHOR]

The cadre of protein complexes in cells performs an array of functions necessary for life. Their varied structures are foundational to their ability to perform biological functions, lending great import to the elucidation of complex composition and dynamics. Native separation techniques that are operative on low sample amounts and provide high resolution are necessary to gain valuable data on endogenous complexes. Here, we detail and optimize the use of tube gel separations to produce samples proven compatible with native, multistage mass spectrometry (nMS/MS). We find that a continuous system (i.e., no stacking gel) with a gradient in its extent of cross-linking and use of the clear native buffer system performs well for both fractionation and native mass spectrometry of heart extracts and a fungal secretome. This integrated advance in separations and nMS/MS offers the prospect of untargeted proteomics at the next hierarchical level of protein organization in biology. [ABSTRACT FROM AUTHOR]

A new, novel, rapid method to detect and direct readout of drugs in human urine has been developed using dynamic surface-enhanced Raman spectroscopy (D-SERS) with portable Raman spectrometer on gold nanorods (GNRs) and a classification algorithm called support vector machines (SVM). The high-performance GNRs can generate gigantic enhancement and the SERS signals obtained using D-SERS on it have high reproducibility. On the basis of this feature of DSERS, we have obtained SERS spectra of urine and urine containing methamphetamine (MAMP). SVM model was built using these data for fast identified and visual results. This general method was successfully applied to the detection of 3, 4-methylenedioxy methamphetamine (MDMA) in human urine. To verify the accuracy of the model, drug addicts' urine containing MAMP were detected and identified correctly and rapidly with accuracy more than 90%. The detection results were displayed direcdy without analysis of their SERS spectra manually. Compared with the conventional method in lab, the method only needs a 2 pL sample volume and takes no more than 2 min on the portable Raman spectrometer. It is anticipated that this method will enable rapid, convenient detection of drugs on site for the police. [ABSTRACT FROM AUTHOR]

Hair is one of the most common types of physical evidence found at a crime scene. Forensic examination may suggest a connection between a suspect and a crime scene or victim, or it may demonstrate an absence of such associations. Therefore, forensic analysis of hair evidence is invaluable to criminal investigations. Current hair forensic examinations are primarily based on a subjective microscopic comparison of hair found at the crime scene with a sample of suspect's hair. Since this is often inconclusive, the development of alternative and more-accurate hair analysis techniques is critical. In this study, we utilized surface-enhanced Raman spectroscopy (SERS) to demonstrate that artificial dyes can be directly detected on hair. This spectroscopic technique is capable of a confirmatory identification of analytes with single molecule resolution, requires minimal sample, and has the advantage of fluorescence quenching. Our study reveals that SERS can (1) identify whether hair was artificially dyed or not, (2) determine if a permanent or semipermanent colorants were used, and (3) distinguish the commercial brands that are utilized to dye hair. Such analysis is rapid, minimally destructive, and can be performed directly at the crime scene. This study provides a novel perspective of forensic investigations of hair evidence. [ABSTRACT FROM AUTHOR]

Characterization of enzymatic reactions occurring in untreated biological samples is of increasing interest Herein, the chemical conversion of alliin to allidn, catalyzed by allinase, in raw garlic cloves has been followed in vivo by internal extractive electrospray ionization mass spectrometry (iEESI-MS). Both precursors and products of the enzymatic reaction were instantaneously extracted by infosed solution running throughout the tissue and directly electrospray ionized on the edge of the bulk sample for online MS analysis. Compared to the room-temperature (+25 °C) scenario, the alliin conversion in garlic cloves decreased by (7.2 ± 1.4) times upon heating to +80 °C and by (5.9 ± 0.8) times upon cooling to -16 °C. Exposure of garlic to gentle ultrasound irradiation for 3 h accelerated the reaction by (1.2 ± 0.1) times. A 10 s microwave irradiation promoted alliin conversion by (1.6 ± 0.4) times, but longer exposure to microwave irradiation (90 s) slowed the reaction by (28.5 ± 7.5) times compared to the reference analysis. This method has been further employed to monitor the germination process of garlic. These data revealed that over a 2 day garlic sprouting, the allidn/alliin ratio increased by (2.2 ± 0.5) times, and the averaged degree of polymerization for the detected oligosaccharides/polysaccharides decreased from 11.6 to 9.4. Overall, these findings suggest the potential use of iEESI-MS for in vivo studies of enzymatic reactions in native biological matrices. [ABSTRACT FROM AUTHOR]

Chlorinated paraffins (CPs) are high production volume chemicals, but data about their environmental fate are scarce. CP mixtures composed of thousands of isomers represent a major challenge for quantification at low levels in environmental samples. Here, we present a novel analytical method for analysis of short-chain, medium-chain, and long-chain CPs in a single injection, that also yields information about congener group pattern. Our detection method is based on direct injection into an atmospheric pressure chemical ionization source operated in negative ion mode under chlorine-enhanced conditions, followed by quadrupole time-of-flight high-resolution mass spectrometry (APCI-qTOF-HRMS) operated in full-scan mode. A mathematical algorithm is applied to deconvolute the CP patterns in the analyzed samples into a linear combination of patterns of technical CP mixtures and to quantify CPs using technical mixtures as external calibration standards. For CP mixtures with known composition, the new method provided concentrations that were within a factor of 1.2 of the target value. Accuracies for CPs spiked to sediment and fish extracts were between 91% and 123%. Concentrations determined in unspiked field samples were within a factor of 5 for short-chain CPs and a factor of 16 for medium-chain CPs of results obtained with an independent method based on gas chromatography/electron capture negative ionization high-resolution mass spectrometry (GC/ECNI-HRMS). The presented APCI-qTOF-HRMS pattern deconvolution method is an interesting alternative for CP analysis in environmental samples. It is particularly sensitive for medium- and long-chain CPs and has the advantage of being extremely fast (instrumental analysis time, less than 1 min). [ABSTRACT FROM AUTHOR]

Extracting useful information from high dimensionality and large data sets is a major challenge for data-driven approaches. The present study was aimed at developing novel integrated analytical strategies for comprehensively characterizing seaweed similarities based on chemical diversity. The chemical compositions of 107 seaweed and 2 seagrass samples were analyzed using multiple techniques, including Fourier transform infrared (FT-IR) and solid- and solution-state nuclear magnetic resonance (NMR) spectroscopy, thermogravimetry-differential thermal analysis (TG-DTA), inductively coupled plasma-optical emission spectrometry (ICP-OES), CHNS/O total elemental analysis, and isotope ratio mass spectrometry (IR-MS). The spectral data were preprocessed using non-negative matrix factorization (NMF) and NMF combined with multivariate curve resolution-alternating least-squares (MCR-ALS) methods in order to separate individual component information from the overlapping and/or broad spectral peaks. Integrated analysis of the preprocessed chemical data demonstrated distinct discrimination of differential seaweed species. Further network analysis revealed a close correlation between the heavy metal elements and characteristic components of brown algae, such as cellulose, alginic acid, and sulfated mucopolysaccharides, providing a componential basis for its metal-sorbing potential. These results suggest that this integrated analytical strategy is useful for extracting and identifying the chemical characteristics of diverse seaweeds based on large chemical data sets, particularly complicated overlapping spectral data. [ABSTRACT FROM AUTHOR]

We use nuclear magnetic resonance spectroscopy methods to quantify the extent of ligand exchange between different types of thiolated molecules on the surface of gold nanoparticles. Specifically, we determine ligand density values for single-moiety ligand shells and then use these data to describe ligand exchange behavior with a second, thiolated molecule. Using these techniques, we identify trends in gold nanoparticle functionalization efficiency with respect to ligand type, concentration, and reaction time as well as distinguish between functionalization pathways where the new ligand may either replace the existing ligand shell (exchange) or add to it ("backfilling"). Specifically, we find that gold nanoparticles functionalized with thiolated macromolecules, such as poly(ethylene glycol) (1 kDa), exhibit ligand exchange efficiencies ranging from 70% to 95% depending on the structure of the incoming ligand. Conversely, gold nanoparticles functionalized with small-molecule thiolated ligands exhibit exchange efficiencies as low as 2% when exposed to thiolated molecules under identical exchange conditions. Taken together, the reported results provide advances in the fundamental understanding of mixed ligand shell formation and will be important for the preparation of gold nanoparticles in a variety of biomedical, optoelectronic, and catalytic applications. [ABSTRACT FROM AUTHOR]

Elemental analysis of unit-mass resolution (UMR) mass spectra is limited by the amount of information available to definitively elucidate the molecular formula of a molecule ionized by electron impact. The problem is compounded when a mixture of organic molecules (such as those found in organic aerosols) is analyzed without the benefit of prior separation. For this reason, quadrupole mass spectrometry is not usually suited to the elemental analysis of organic mixtures. Here, we present a mathematical method for the elemental analysis of UMR mass spectra of a complex organic aerosol through the use of isotopic labeling. Quadrupole aerosol mass spectrometry was used to obtain UMR data of 13C-labeled and unlabeled aerosol generated by far ultraviolet (FUV) photochemistry of gas mixtures containing 0.1% of either CH4 or 13CH4 in N2. In this method, the differences in the positions of ion groups in the resulting spectra are used to estimate the mass fraction of carbon in the aerosol, and estimation of the remaining elements follows. Analysis of the UMR data yields an elemental composition of 63 ± 7% C, 8 ± 1% H, and 29 ± 7% N by mass. Unlabeled aerosols formed under the same conditions are found by high-resolution time-of-flight aerosol mass spectrometry to have an elemental composition of 63 ± 3% C, 8 ± 1% H, 20 ± 4% N, and 9 ± 3% O by mass, in good agreement with the UMR method. This favorable comparison verifies the method, which expands the UMR mass spectrometry toolkit. [ABSTRACT FROM AUTHOR]

Oligosaccharides are critical for structural integrity, stability, and biological functions of recombinant monoclonal antibodies. It is relatively easy to characterize, quantify, and determine the impact of major glycoforms. While challenging to detect and quantify, certain low abundance oligosaccharides are highly relevant to the stability and functions of recombinant monoclonal antibodies. Methods were established in this study based on enzymatic digestion to consolidate peaks of the same type of oligosaccharides by removing heterogeneity and thus increase detectability of low abundance peaks. Endo H was used to collapse high mannose oligosaccharides to a single peak of GlcNAc for ease of detection and quantitation. β-Galactosidase and β-N-acetylhexosaminidase were used to convert complex oligosaccharides into two peaks containing either GlcNAc2Man3Fuc or GlcNAc2Man3, which simplified the chromatograms and data analysis. More importantly, low abundance hybrid oligosaccharides can only be detected and qualified after β-galactosidase and β-N-acetylhexosaminidase digestion. Detection and quantitation of low abundance oligosaccharides can also be achieved using a combination of all three enzymes. These methods can be applied to the development of recombinant monoclonal antibody therapeutics. [ABSTRACT FROM AUTHOR]

Although surface-enhanced Raman spectroscopy (SERS) has been featured by high sensitivity, additional signal enhancement is still necessary for trace amount of biomolecules detection. In this paper, a SERS amplified approach, featuring "ions-mediated cascade amplification (IMCA)", was proposed by utilizing the dissolved silver ions (Ag+) from silver nanoparticles (AgNPs). We found that using Ag+ as linkage agent can effectively control the gaps between neighboring 4-aminobenzenethiol (4-ABT) encoded gold nanoparticles (AuNPs@4-ABT) toform "hot spots" and thus produce SERS signal output, in which the SERS intensity was proportional to the concentration of Ag+. Inspired by this finding, the IMCA was utilized for ultrasensitive detection of single nucleotide polymorphism in human mitochondrial DNA (16189T → C). Combining with the DNA ligase reaction, each target DNA binding event could successfully cause one AgNP introduction. By detecting the dissolved Ag+ from AgNPs using IMCA, low to 3.0 × 10(-5) fm/μL targeted DNA can be detected, which corresponds to extractions from 200 nL cell suspension containing carcinoma pancreatic β-cell lines from diabetes patients. This IMCA approach is expected to be a universal strategy for ultrasensitive detection of analytes and supply valuable information for biomedical research and clinical early diagnosis. [ABSTRACT FROM AUTHOR]

A method for the detection and speciation of inositol phosphates (InsPn) in sediment samples was tested, utilizing oxalate-oxalic acid extraction followed by determination by high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) using electrospray ionization (ESI) in negative mode. The chromatographic separation was carried out using water and ammonium bicarbonate as mobile phase in gradient mode. Data acquisition under MS/MS was attained by multiple reaction monitoring. The technique provided a sensitive and selective detection of InsPn in sediment samples. Several forms of InsPn in the oxalate-oxalic acid extracted sediment were identified. InsP6 was the dominating form constituting 0.250 mg P/g DW (dry weight); InsP5 and InsP4 constituted 0.045 and 0.014 mg P/g DW, respectively. The detection limit of the LC-ESI-MS/MS method was 0.03 μM InsPn, which is superior to the currently used method for the identification of InsPn, 31P nuclear magnetic resonance spectroscopy (31P NMR). Additionally sample handling time was significantly reduced. [ABSTRACT FROM AUTHOR]

Herein, we report a new pyridine-biquinoline-derivative fluorophore L for effectively sensing pyrophosphate (PPi) and monohydrogen sulfide (HS-) in aqueous buffer and in living cells. L could selectively coordinate with metal ions (Mn+) in Groups IB and IIB to form L-Mn+ complexes with 1:1 stoichiometry, resulting in fluorescence quenching via photoinduced electron transfer (PET) mechanism. L-Zn2+ complex was applied to competitively coordinate with PPi to form a new "ate"-type complex, turning on the fluorescence by a 21-fold-increase. The limit of detection (LOD) of this assay for PPi detection in aqueous buffer is 0.85 μM. L-Cu2+ complex was applied for highly selective detection of HS- with an excellent sensitivity by 25-fold decomplexation-induced fluorescence increase. LOD of L-Cu2+ complex for HS- detection in aqueous buffer is 2.24 μM. With the in vitro data obtained, we successfully applied these two complexes for sequential imaging Zn2+ and PPi, Cu2+ and HS- in living cells, respectively. Since PPi and HS- occur in vascular calcification in positive correlation, our multifunctional probe L might help doctors to more precisely diagnose this disease in vivo in the future. For example, we could use radioactive tracer L-64Cu for qualitative and quantitative positron emission tomography/computed tomography (PET/CT) imaging of HS- in vivo. [ABSTRACT FROM AUTHOR]

We report for the first time seeing and counting integrin αIIbβ3 on a single-cell level. The proposed method is based on the using of the Au cluster probe. With the fluorescent property of Au24) cluster and the specific targeting ability of peptide, our probe can direcdy visualize integrin on the membrane of human erythroleukemia cells (HEL) via confocal microscopy. On the basis of the accurate formula of our probe (Au24Peptide8), the number of integrin αIIbβ3 can be precisely counted by quantifying the gold content on a single HEL cell via laser ablation inductively coupled plasma mass spectrometry. Our results reveal that the number of integrin a nhfi3 on a single cell varies from 5.75 × 10-17 to 9.11 × 10-17 mol, because of the heteroexpression levels of a αllbon individual cells. [ABSTRACT FROM AUTHOR]

Modern high-resolution mass spectrometry (HRMS) enables full-spectrum trace level analysis of emerging environmental organic contaminants. This raises the opportunity for post-acquisition suspect screening when no reference standards are a priori available. When setting up a conventional screening identification train based on successively different identification criteria including mass error and isotope fit, the false negative rate typically accumulates upon advancing through the decision tree. The challenge is thus to elaborate a well-balanced screening, in which the different criteria are equally stringent, leading to a controllable number of false negatives. Presented is a novel suspect screening approach using liquid-chromatography Orbitrap HRMS. Based on a multivariate statistical model, the screening takes into account the accurate mass error of the mono isotopic ion and up to three isotopes, isotope ratios, and a peak/noise filter. As such, for the first time, controlling the overall false negative rate of the screening algorithm to a desired level (5% in this study) is achieved. Simultaneously, a well-balanced identification decision is guaranteed taking the different identification criteria as a whole in a holistic statistical approach. Taking into account 1, 2, and 3 isotopes decreases the false positive rate from 22, 2.8 to <0.3%, but the cost of increasing the median limits of identification from 200, 2000 to 2062 ng L-1, respectively, should also be considered. As proof of concept, 7 biologically treated wastewaters were screened toward 77 suspect pharmaceuticals resulting in the indicative identification of 25 suspects. Subsequently obtained reference standards allowed confirmation for 19 out of these 25 pharmaceutical contaminants. [ABSTRACT FROM AUTHOR]

Purification of antibodies is an important first step to produce material for in depth characterization of biotherapeutics. To reduce the resource burden incurred by protein purification, we developed a high throughput protein A affinity capture step coupled to inline mass spectrometry (PrA-MS). Our method enables both UV quantitation of antibodies and product characterization of an intact molecule with microgram quantities of material. When purification and analysis are coupled along with the low material demand, PrA-MS is widely applicable to protein characterization and is uniquely advantageous for moieties that rely on molecular stoichiometry. Two model systems were studied using PrA-MS and are presented here: (a) bispecific antibodies (bsAb) and (b) glycan engineered antibodies. In the bsAb samples, hetero- and homodimer spedes, along with partial molecule, were readily identified and quantified directly from harvested cell culture fluid (HCCF). In the glycan engineered antibodies, fully afucosylated, as well as asymmetrically and symmetrically fucosylated, glycans were identified from HCCF in experiments that utilized a small molecule inhibitor of fucosyltrasferase. The PrA-MS method represents a high throughput alternative to offline purification and product characterization that may be leveraged across the product lifecycle of engineered antibodies to enable rapid development and production of important therapeutics. [ABSTRACT FROM AUTHOR]

A global spectral deconvolution, based on non-negative matrix factorization (NMF) in comprehensive two-dimensional gas chromatography high-resolution time-of-flight mass spectrometry, was developed. We evaluated the ability of various instrumental parameters and NMF settings to derive high-performance detection in nontarget screening using a sediment sample. To evaluate the performance of the process, a NIST library search was used to identify the deconvoluted spectra. Differences of the instrumental scan rates (25 and 50 Hz) in deconvolution were evaluated and results show that a high scan rate enhanced the number of compounds detected in the sediment sample. A higher mass resolution in the range of 1 000 to 10 000 and a higher m/z precision in the deconvolution were needed to obtain an accurate mass database. After removal of multiple duplicate hits, which occurred in batch processes of NIST library search on the deconvolution result, 62 unique assignable spectra with a match factor ≥900 were obtained in the deconvoluted chromatogram from the sediment sample, including 54 spectra that were refined by the deconvolution. This method will help to detect and build up well-resolved reference spectra from various complex mixtures and will accelerate nontarget screening. [ABSTRACT FROM AUTHOR]

Analysis and separation of atomic ions within a portable setting are studied in forensic applications of radiological debris analysis. Ion mobility spectrometry (IMS) may be used to show separation of atomic ions, while the related method of differential mobility spectrometry (DMS) has focused on fractionation of primarily molecular components. We set out to investigate DMS as a means for separating atomic ions. We initially derived the differential ion mobility parameter, alpha, from classic empirical IMS data of atomic ions, cesium and potassium, each showing its own distinct form of alpha. These alpha functions were applied to DMS simulations and supported by analytical treatment that suggested a means for a rapid disambiguation of atomic ions using DMS. We validated this hypothesis through the prototype cesium-potassium system investigated experimentally by DMS coupled to mass spectrometry (MS). Such a feature would be advantageous in a field portable instrument for rapid atomic analyses especially in the case of isobaric ions that cannot be distinguished by MS. Herein, we first report this novel method for the derivation of alpha from existing field dependent drift tube ion mobility data. Further, we translate experimental DMS data into alpha parameters by expanding upon existing methods. Refining the alpha parameter in this manner helps convey the interpretation of the alpha parameter particularly for those new to the DMS field. [ABSTRACT FROM AUTHOR]

Interesting properties of water with distinguishable hydrogen-bonding structure on interfacial phase or in confined environment have drawn wide attentions. However, these unique properties of water are only found within the interfacial phase and confined environment, thus, their applications are limited. In addition, quantitative evaluation on these unique properties associating with the enhancement of water's physical and chemical activities represents a notable challenge. Here we report a practicable production of free-standing liquid water at room temperature with weak hydrogen-bonded structure naming Au nanoparticles (NPs)-treated (AuNT) water via treating by plasmon-induced hot electron transfer occurred on resonantly illuminated gold NPs (AuNPs). Compared to well-known untreated bulk water (deionized water), the prepared AuNT water exhibits many distinct activities in generally physical and chemical reactions, such as high solubilities to NaCl and O2. Also, reducing interaction energy within water molecules provides lower overpotential and higher efficiency in electrolytic hydrogen production. In addition, these enhanced catalytic activities of AuNT water are tunable by mixing with deionized water. Also, most of these tunable activities are linearly proportional to its degree of nonhydrogen-bonded structure (DNHBS), which is derived from the O-H stretching in deconvoluted Raman spectrum. [ABSTRACT FROM AUTHOR]

The article discusses the principles of single molecule spectroscopy and its methodology into chromatographic analysis for complex mixtures. It describes the general considerations and requirements for various methods including reverse phase liquid chromatography, normal face for silica surfaces, and ion-exchange chromatography. It also presents theoretical insights and application of data for future direction of single molecule spectroscopy.

Surface-enhanced Raman spectroscopy (SERS) is generally performed on planar surfaces, which can be difficult to prepare and may limit the interaction of the sensing surface with targets in large volume samples. We propose that nanocomposite materials can be configured that both include SERS probes and provide a high surface area-to-volume format, i.e., fibers. Thiol-yne nanocomposite films and fibers were fabricated using exposure to long-wave ultraviolet light after the inclusion of gold nanoparticles (AuNPs) functionalized with thiophenol. A SERS response was observed that was proportional to the aggregation of the AuNPs within the polymers and the amount of thiophenol present. Overall, this proof-of-concept fabrication of SERS active polymers indicated that thiol-yne nanocomposites may be useful as durable film or fiber SERS probes. Properties of the nanocomposites were evaluated using various techniques including UV-vis spectroscopy, μ-Raman spectroscopy, dynamic mechanical analysis, differential scanning calorimetry, therm ogravimetric analysis, and transmission electron microscopy. [ABSTRACT FROM AUTHOR]

Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy is a powerful technique for characterizing the composition and bonding state of nanoscale materials and the top few nanometers of bulk and thin film specimens. When coupled with imaging methods like photoemission electron microscopy, it enables chemical imaging of materials with nanometer-scale lateral spatial resolution. However, analysis of NEXAFS spectra is often performed under the assumption of structural and compositional homogeneity within the nanometer-scale depth probed by this technique. This assumption can introduce large errors when analyzing the vast majority of solid surfaces due to the presence of complex surface and near-surface structures such as oxides and contamination layers. An analytical methodology is presented for removing the contribution of these nanoscale overlayers from NEXAFS spectra of two-layered systems to provide a corrected photoabsorption spectrum of the substrate. This method relies on the subtraction of the NEXAFS spectrum of the overlayer adsorbed on a reference surface from the spectrum of the two-layer system under investigation, where the thickness of the overlayer is independently determined by X-ray photoelectron spectroscopy (XPS). This approach is applied to NEXAFS data acquired for one of the most challenging cases: air-exposed hard carbon-based materials with adventitious carbon contamination from ambient exposure. The contribution of the adventitious carbon was removed from the as-acquired spectra of ultrananocrystalline diamond (UNCD) and hydrogenated amorphous carbon (a-C:H) to determine the intrinsic photoabsorption NEXAFS spectra of these materials. The method alters the calculated fraction of sp2-hybridized carbon from 5 to 20% and reveals that the adventitious contamination can be described as a layer containing carbon and oxygen ([O]/[C] = 0.11 ± 0.02) with a thickness of 0.6 ± 0.2 nm and a fraction of sp2-bonded carbon of 0.19 ± 0.03. This method can be generally applied to the characterization of surfaces and interfaces in several research fields and technological applications. [ABSTRACT FROM AUTHOR]

The concept of generalized ratiometric indicator based surface-enhanced Raman spectroscopy was first introduced and successfully implemented in the detection of Cd2+ in environmental water samples using Au nanoparticles (AuNPs) modified by trithiocyanuric acid (TMT). Without the use of any internal standard, the proposed method achieved accurate concentration predictions for Cd2+ in environmental water samples with recoveries in the ranges of 91.8-108.1%, comparable to the corresponding values obtained by atomic absorption spectroscopy. The limit of detection and limit of quantification were estimated to be 2.9 and 8.7 nM, respectively. More importantly, other species present in water samples which cannot react with TMT and have weaker binding ability to AuNPs than TMT do not interfere with the quantification of Cd2+. Therefore, it is expected that the combination of the generalized ratiometric indicator based surface-enhanced Raman spectroscopy with the proposed AuNP-TMT probing system can be a competitive alternative for the primary screening of Cd2+ pollution. [ABSTRACT FROM AUTHOR]

A newly developed isotope ratio laser spectrometer for CO2 analyses has been tested during a tracer experiment at the Ketzin pilot site (northern Germany) for CO2 storage. For the experiment, 500 tons of CO2 from a natural CO2 reservoir was injected in supercritical state into the reservoir. The carbon stable isotope value (δ13C) of injected CO2 was significantly different from background values. In order to observe the breakthrough of the isotope tracer continuously, the new instruments were connected to a stainless steel riser tube that was installed in an observation well. The laser instrument is based on tunable laser direct absorption in the mid-infrared. The instrument recorded a continuous 10 day carbon stable isotope data set with 30 min resolution directly on-site in a field-based laboratory container during a tracer experiment. To test the instruments performance and accuracy the monitoring campaign was accompanied by daily CO2 sampling for laboratory analyses with isotope ratio mass spectrometry (IRMS). The carbon stable isotope ratios measured by conventional IRMS technique and by the new mid-infrared laser spectrometer agree remarkably well within analytical precision. This proves the capability of the new mid-infrared direct absorption technique to measure high precision and accurate real-time stable isotope data directly in the field. The laser spectroscopy data revealed for the first time a prior to this experiment unknown, intensive dynamic with fast changing δ13C values. The arrival pattern of the tracer suggest that the observed fluctuations were probably caused by migration along separate and distinct preferential flow paths between injection well and observation well. The short-term variances as observed in this study might have been missed during previous works that applied laboratory-based IRMS analysis. The new technique could contribute to a better tracing of the migration of the underground CO2 plume and help to ensure the long-term integrity of the reservoir. [ABSTRACT FROM AUTHOR]

Fourier transform (FT)-plasmon waveguide resonance (PWR) spectroscopy measures light reflectivity at a waveguide interface as the incident frequency and angle are scanned. Under conditions of total internal reflection, the reflected light intensity is attenuated when the incident frequency and angle satisfy conditions for exciting surface plasmon modes in the metal as well as guided modes within the waveguide. Expanding upon the concept of two-frequency surface plasmon resonance developed by Peterlinz and Georgiadis [Opt. Commun. 1996, 130, 260], the apparent index of refraction and the thickness of a waveguide can be measured precisely and simultaneously by FT-PWR with an average percent relative error of 0.4%. Measuring reflectivity for a range of frequencies extends the analysis to a wide variety of sample compositions and thicknesses since frequencies with the maximum attenuation can be selected to optimize the analysis. Additionally, the ability to measure reflectivity curves with both p- and s-polarized light provides anisotropic indices of refraction. FT-PWR is demonstrated using polystyrene waveguides of varying thickness, and the validity of FT-PWR measurements are verified by comparing the results to data from profilometry and atomic force microscopy (AFM). [ABSTRACT FROM AUTHOR]

Aggregation continues to be a critical quality attribute for a monoclonal antibody therapeutic product due to its perceived significant impact on immunogenicity. This paper aims to establish the versatility of circular dichorism (CD) spectroscopy toward understanding aggregation of monoclonal antibody (mAb) therapeutics. The first application involves the use of far-UV CD as a complementary analytical technique to size exclusion chromatography (SEC) for understanding protein aggregation. The second application uses thermal scanning CD as a high throughput screening tool for examining stability of a mAb therapeutic in various formulation and downstream buffers. For establishing far-UV CD as an orthogonal technique, a mAb was incubated in different downstream processing buffers and another mAb in formulation buffers, and they were analyzed by SEC and far-UV CD for aggregate content and conformational stability, respectively. To examine thermal scanning as a high throughput screening tool, ellipticity as a function of the temperature was measured at 218 nm from 20 to 90 °C. Far-UV CD was found to display high sensitivity toward early detection of conformational changes in mAb. CD measurements were also able to elucidate the different aggregation mechanisms. Furthermore, thermal stability scan allowed us to estimate Tonset which has been found to correlate with aggregation induced by salt, low pH, and buffer species. Tonset temperature from thermal scanning at 218 nm using CD was correlated successfully to aggregate content measured by SEC. Results from both the studies demonstrate the usefulness of CD for assessing stability of therapeutic proteins during process development, formulation development, and product characterization. [ABSTRACT FROM AUTHOR]

Hafnium content and its change are of significance in geochemistry and cosmochemistry; however, the determination of hafnium has always been problematic in analytical chemistry. In this paper, a new idea is proposed for the determination of hafnium in geochemical samples, including rocks, soils, and stream sediments. Through the comparison of two conventional open-type acid digestion methods (HF-HNO3-HClO4 and HF-HNO3-H2SO4), it was found that although neither of these methods could fully digest the zirconium and hafnium in a sample, the zirconium and hafnium digestion behaviors in one sample were consistent in the 60 experimental geochemical reference materials with different properties, so the experimentally determined Zr/Hf ratio in solution could be used to calculate the hafnium content in a sample. In addition, possible mass spectral interferences during the determination of zirconium and hafnium by high resolution inductively coupled plasma mass spectrometry (HR-ICPMS) were studied, and it was found that the mass spectral interferences of the selected isotopes 90Zr and 178Hf could be neglected. The mass spectral behaviors of 90Zr and 178Hf were also very consistent during the determination by HR-ICPMS. Since the hafnium content was calculated using the ratio value, all of the errors (including the errors in weighing process, the accidental errors during operation and the instrument fluctuation in the determination) of the Zr/Hf ratio could be effectively reduced or even eliminated. The relative standard deviation of the actual samples was lower than 3.2%, and the detection limit of the method (considering the dilution effect and matrix effect during measurement of the Zr/Hf ratio and zirconium content) was 0.04 μg/g. The proposed method could satisfy the requirement for the determination of hafnium in geochemical samples. [ABSTRACT FROM AUTHOR]

We demonstrate detection of femtogram-scale quantities of the explosive molecule 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) via combined nanomechanical photothermal spectroscopy and mass desorption. Photothermal spectroscopy provides a spectroscopic fingerprint of the molecule, which is unavailable using mass adsorption/desorption alone. Our measurement, based on thermomechanical measurement of silicon nitride nanostrings, represents the highest mass resolution ever demonstrated via nanomechanical photo-thermal spectroscopy. This detection scheme is quick, label-free, and is compatible with parallelized molecular analysis of multicomponent targets. [ABSTRACT FROM AUTHOR]

Coupling solid-phase microextraction (SPME) with ambient mass spectrometry using surface coated wooden-tip probe was achieved for the first time and applied in the analysis of ultra trace perfluorinated compounds (PFCs) in complex environmental and biological samples. We modified n-octadecyldimethyl[3-(trimethoxysilyl)propyl] ammonium chloride on the surface of sharp wooden tip via silanization to form a novel SPME probe, which was then used for highly selective enrichment of PFCs from complex matrices and applied as a solid substrate to induce electrospray ionization for mass spectrometric analysis. The porous structural surface together with the dual extraction mechanisms (reversed phase adsorption and ion exchange adsorption) demonstrated that the SPME probe has an outstanding enrichment capacity, enhancing sensitivity by approximately 4000-8000 folds for the detection in aqueous samples, and 100-500-fold in whole blood and milk samples. The method showed good linearity, with correlation coefficient values (r2) of no less than 0.9931 for eight target PFCs. The limits of detection and qualification of the eight PFCs were 0.06-0.59 and 0.21-1.98 ng/L, respectively. Quantification of real samples was achieved by isotope internal standard calibration curve method or isotope dilution method, and ultratrace levels of PFCs present in lake water, river water, whole blood, and milk samples had been successfully detected and qualified. [ABSTRACT FROM AUTHOR]

Shearforce regulated scanning electrochemical microscopy (SECM) has been associated with Raman microspectrometry in order to perform combined electrochemical and spectrochemical analysis on reactive interfaces. The interest of the method was evaluated by analyzing local corrosion phenomena in damaged Zn(Mg, Al) self-healing coatings deposited on steel. Despite the high aspect ratio of the analyzed sample displaying here more than a 50 μm depth profile, the optimized setup allowed (1) precise electrode positioning with the help of shearforce detection, (2) electrochemical measurement at a constant distance from the sample surface, and (3) local chemical analysis of the solid surface by confocal Raman microspectroscopy performed at a constant focal distance from the sample. All in all, this new setup allows one to approach the detailed reactivity involved in defective metal samples. [ABSTRACT FROM AUTHOR]

The development of a portable and easy-to-use device for the detection of explosives with high sensitivity and selectivity is in high demand for homeland security and public safety. In this study, we demonstrate miniaturized devices depending on the upconversion ratiometric luminescent probe for point-of-care (POC) assay of explosives with the naked-eye. When the PEI-coated upconversion nanoparticles (UCNPs) selectively bonded to 2,4,6-trinitrotoluene (TNT) explosives by the formation of Meisenheimer complex, the formed of UCNP-Meisenheimer complexes show turned visible multicolor upconversion luminescence (UCL) on account of TNT-modulating Forster resonance energy transfer process under near-infrared excitation. With UCL emission at 808 nm as internal standard and ratiometric UCL at 477 nm to that at 808 nm (I477/I808) as output signal, the probe can simultaneously meet the accuracy for TNT explosives quantitative analysis. In addition, this easy-to-use visual technique provides a powerful tool for convenient POC assay of rapid explosives identification. [ABSTRACT FROM AUTHOR]

In the field of bioanalysis, there is an increasing demand for miniaturized, automated, robust sample pretreatment procedures that can be easily connected to directinfusion mass spectrometry (DI-MS) in order to allow the high-throughput screening of drugs and/or their metabolites in complex body fluids like plasma. Liquid-Liquid extraction (LLE) is a common sample pretreatment technique often used for complex aqueous samples in bioanalysis. Despite significant developments that have been made in automated and miniaturized I LF, procedures, fully automated LLE techniques allowing high-throughput bioanalytical studies on small-volume samples using direct infusion mass spectrometry, have not been matured yet. Here, we introduce a new fully automated micro-LLE technique based on gas-pressure assisted mixing followed by passive phase separation, coupled online to nanoelectrospray-DI-MS. Our method was characterized by varying the gas flow and its duration through the solvent mixture. For evaluation of the analytical performance, four drugs were spiked to human plasma, resulting in highly acceptable precision (RSD down to 9%) and linearity (Rz ranging from 0.990 to 0.998). We demonstrate that our new method does not only allow the reliable extraction of analytes from small sample volumes of a few microliters in an automated and high-throughput manner, but also performs comparable or better than conventional offline LLE, in which the handling of small volumes remains challenging. Finally, we demonstrate the applicability of our method for drug screening on dried blood spots showing excellent linearity (R2 of 0.998) and precision (RSD of 9%). In conclusion, we present the proof of principe of a new high-throughput screening platform for bioanalysis based on a new automated microLLE method, coupled online to a commercially available nano-ESI-DI-MS. [ABSTRACT FROM AUTHOR]

Mass spectrometry (MS) is widely used for isotopic studies ol metabolism in which detailed information about biochemical processes is obtained from the analysis of isotope incorporation into metabolites. The biological value of such experiments is dependent on the accuracy of the isotopic measurements. Using MS, isotopologue distributions are measured from the quantitative analysis of isotopic clusters. These measurements are prone to various biases, which can occur during the experimental workflow and/or MS analysis. The lack of relevant standards limits investigations of the quality of the measured isotopologue distributions. To meet that need, we developed a complete theoretical and experimental framework for the biological production of metabolites with hilly controlled and predictable labeling patterns. This strategy is valid for different isotopes and different types of metabolisms and organisms, and was applied to two model microorganisms, Pichia augusta and Escherichia coli, cultivated on 13C-labeled methanol and acetate as sole carbon source, respectively. The isotopic composition of the substrates was designed to obtain samples in which the isotopologue distribution of all the metabolites should give the binomial coefficients found in Pascal s triangle. The strategy was validated on a liquid chromatography-tandem mass spectrometry (LC-MS/MS) platfonn by quantifying the complete Isotopologue distributions of different intracellular metabolites, which were in dose agreement with predictions. This strategy can be used to evaluate entire experimental workflows (from sampling to data processing) or different analytical platforms in tire context of isotope labeling experiments. [ABSTRACT FROM AUTHOR]

Cotinine (COT), trans-3'-hydroxycotinine (OH-COT), cotinine-N-β-glμcμronide (COT-GLUC), and trans-3'-hydroxycotinine- O-β-dμcμronide (OH-COT-GLUC) are excreted in μrine following the intake of nicotine (NIC), and, as sμch, they have been detected in sewaee Thμs they also constitμte convenient biomarkers for NIC tracing throμU the sewage epidemiology approach at the local scale. Sμch estimation reqμires granting a good stability of the target biomarkers in sewage However, it was foμnd that glμcμronides are not stable, particμlarly in the case of OH-COT-GLUC, which coμld render variable concentrations of COT, OH-COT, and their glμcμronides, depending on sampling and storage time or temperatμre. Thμs, an enzymatic deconjμgation with β-glμcμronidase was optimized. βith the optimized method after enzymatic deglμcμronization, the limits of qμantification obtained were in the range of 0 .2-1 μgL-1, relative standard deviations were <10%, and the trμeness in terms of recovery was in Z 95%-112% ranee The application of the method to composite sewage samples collected dμring 1 week in three different vearsin Smtiago de Compostela (Galicia, Spain) showed COT and OH-COT concentrations of 0.3-1.9 μg L-1 and 1.0-3.3 μg L-1 respectively Thereby the average NIC consμmption derived was in the 1.7-1.9 mg per day and person range, being comparable to those derived from tobacco sales statistics. [ABSTRACT FROM AUTHOR]

In this Article, our previously developed ambient LESA-MS methodology is implemented to analyze five types of thermally treated meat species, namely, beef, pork, horse, chicken, and turkey meat, to select and identify heat-stable and species-specific peptide markers. In-solution tryptic digests of cooked meats were deposited onto a polymer surface, followed by L&A-MS analysis and evaluation using multivariate data analysis and tandem electrospray MS. The five types of cooked meat were clearly discriminated using principal component analysis and orthogonal partial least-squares discriminant analysis. 23 heat stable peptide markers unique to species and muscle protein were identified Mowing data-dependent tandem LESA-MS analysis. Surface extraction and direct ambient MS analysis of mixtures of cooked meat species was performed for the first time and enabled detection of 10% (WW of Dork horse, and turkey meat and 5% (w/w) of chicken meat in beef, using the developed LESA-MS/MS analysis The study shows for the first time, that ambient LESA-MS methodology displays specificity sufficient to be implemented effectively for the analyst of processed and complex peptide digests. The proposed approach is much faster and simpler than other measurement tools for meat speciation; it has potential for application in other areas of meat science or food production [ABSTRACT FROM AUTHOR]

Arsenic-containing lipids (arsenolipids) are novel natural products recently shown to be widespread in marine animals and algae. Research interest in these arsenic compounds lies in their possible role in the membrane chemistry of organisms and, because they occur in many popular seafoods, their human metabolism and toxicology. Progress has been restricted, however, by the lack of standard arsenolipids and of a quantitative method for their analysis. We report that the certified reference material CRM 7405-a (Hijiki) is a rich source of arsenolipids, and we describe a method based on HPLC-ICPMS/ESMS to quantitatively measure seven of the major arsenolipids present. Sample preparation involved extraction with DCM/methanol, a cleanup step with silica, and conversion of the (oxo)arsenolipids originally present to thio analogues by brief treatment with H2S. Compared to their oxo analogues, the thioarsenolipids showed much sharper peaks on reversed-phase HPLC, which facilitated their resolution and quantification. The compounds were determined by HPLC-ICPMS and HPLC-ESMS, which provided both arsenic-selective detection and high resolution molecular mass detection of the arsenolipids. In this way, the concentrations of two arsenic-containing hydrocarbons and five arsenosugar phospholipids are reported in the CRM Hijiki. This material may serve as a convenient source of characterized arsenolipids to delineate the presence of these compounds in seafoods and to facilitate research in a new era of arsenic biochemistry. [ABSTRACT FROM AUTHOR]

The concept and method for mass selective ion transfer and accumulation within quadrupole ion trap arrays have been demonstrated. Proof-of-concept experiments have been performed on two sets of ion trap arrays: (1) a linear ion trap with axial ion ejection plus a linear ion trap with radial ion ejection; (2) a linear ion trap with axial ion ejection plus a linear ion trap with axial ion ejection. In both sets of ion trap arrays, ions trapped in the first ion trap could be mass selectively transferred and accumulated into the second ion trap, while keeping other ions reserved in the first ion trap. Different operating modes have been implemented and tested, including transferring all ions, ions within a selected mass range, ions with a mass-to-charge ratio of 1, and randomly selected ions. Unit mass resolution for ion transfer and ~90% ion transfer efficiency has been achieved. A new tandem mass spectrometry scheme for analyzing multiple precursor ions in a single sample injection has been demonstrated, which would improve instrument duty cycle and sample utilization rate (especially for very limited samples), potentially facilitate applications like single cell analyses, and improve electron transfer dissociation efficiency. [ABSTRACT FROM AUTHOR]

Although it is known that the CaSO4/H2O system is formed by at least five different phases, this fact is not correctly documented in Raman spectroscopy studies. The main problem detected in the literature was the incorrect definition of the anhydrite, which produced the assignation of different spectra for a single compound. In this sense, two different spectra were clearly identified from the bibliography, which showed different main Raman bands at 1017 or 1025 cm-1, although anhydrite could be present even as three different polymorphous species with different structures. A better understanding of the whole system obtained from a review of the literature allowed new conclusions to be established. Thanks to that revision and the development of different thermodynamical experiments by Raman spectroscopy, the Raman spectra of each phase were successfully identified for the first time. In this way, the main Raman bands of gypsum, bassanite, anhydrite III, anhydrite II and anhydrite I were identified at 1008, 1015, 1025, 1017 and 1017 cm-1, respectively. To conclude this work, the contradictions found in literature were critically summarized. [ABSTRACT FROM AUTHOR]

A novel gas to particle conversion-gas exchange technique for the direct analysis of metal carbonyl gas by inductively coupled plasma mass spectrometry (ICPMS) was proposed and demonstrated in the present study. The technique is based on a transfer of gas into particle, which can be directly analyzed by ICPMS. Particles from metal carbonyl gases such as Cr(CO)6, Mo(CO)6, and W(CO)6 are formed by reaction with ozone (O3) and ammonium (NH3) gases within a newly developed gas to particle conversion device (GPD). The reaction mechanism of the gas to particle conversion is based on either oxidation of metal carbonyl gas by 03 or agglomeration of metal oxide with ammonium nitrate (NH4NO3) which is generated by the reaction of O3 and NH3. To separate the reaction gases (remaining O3 and NH3) from the formed particles, a previously reported gas exchange device (GED) was used and the in argon stabilized analyte particles were directly introduced and measured by ICPMS. This new technique provided limits of detection (LOD) of 0.15 pL L-1 (0.32 ng m-3) 0.02 pL L-1 (0.07 ng m-3), and 0.01 pL L-1 (0.07 ng m-3) for Cr(CO)6, Mo(CO)6 and W(CO)6 respectively, which were 4-5 orders of magnitude lower than those conventional applied for detecting these gases, e.g., gas chromatography with electron captured detector (GC-ECD) as well as Fourier transform-infrared spectroscopy (FT-IR). The achieved LODs were also similar or slightly better than those for ICPMS coupled to GC. Since the gas to particle conversion technique can achieve the direct measurement of metal carbonyl gases as well as the removal of reaction and ambient gases from metal carbonyl gases the technique is considered to be well suited to monitor gas quality in semiconductor industry, engine exhaust gases ana" or 'waste incineration products. [ABSTRACT FROM AUTHOR]

We report on the performance of structures for lossless ion manipulation (SLIM) as a means for transmitting ions and performing ion mobility separations (IMS). Ions were successfully transferred from an electrospray ionization (ESI) source to the TOF MS analyzer by means of a linear SLIM, demonstrating lossless ion transmission and an alternative arrangement including a 90° turn. First, the linear geometry was optimized for radial confinement by tuning RF on the central "rung" electrodes and potentials on the DC-only guard electrodes. Selecting an appropriate DC guard bias (2-6 V) and RF amplitude (+160 Vp-p at 750 kHz) resulted in the greatest ion intensities. Close to ideal IMS resolving power was maintained over a significant range of applied voltages. Second, the 90° turn was optimized for radial confinement by tuning RF on the rung electrodes and DC on the guard electrodes. However, both resolving power and ion transmission showed a dependence on these voltages, and the best conditions for both were >300 Vp-p RF (685 kHz) and 7- 11 V guard DC bias. Both geometries provide IMS resolving powers at the theoretical limit (R ~ 58), showing that degraded resolution from a "racetrack" effect from turning around a corner can be successfully avoided, and the capability also was maintained for essentially lossless ion transmission. [ABSTRACT FROM AUTHOR]

Recent advances in sector field inductively coupled plasma mass spectrometry (ICP-SFMS) have led to significant sensitivity enhancements that expand the range of radionuclides measurable by ICP-MS. The increasing capability and performance of modern ICP-MS now allows analysis of medium-lived radionuclides previously undertaken using radiometric methods. A new generation ICP-SFMS was configured to achieve sensitivities up to 80 000 counts per second for a 1 ng/L 133Cs solution, providing a detection limit of 1 pg/L. To extend this approach to environmental samples it has been necessary to develop an effective chemical separation scheme using ultrapure reagents. A procedure incorporating digestion, chemical separation and quantification by ICP-SFMS is presented for detection of the significant fission product radionuclides of cesium (135Cs and 137Cs) at concentrations found in environmental and low level nuclear waste samples. This in turn enables measurement of the 135Cs/137Cs ratio, which varies with the source of nuclear contamination, and can therefore provide a powerful dating and forensic tool compared to radiometric detection of 137Cs alone. A detection limit in sediment samples of 0.05 ng/kg has been achieved for 135Cs and 137Cs, corresponding to 2.0 × 10-3 and 160 mBq/kg, respectively. The critical issue is ensuring removal of barium to eliminate isobaric interferences arising from 135Ba and 137Ba. The ability to reliably measure 135Cs/137Cs using a high specification laboratory ICP-SFMS now enables characterization of waste materials destined for nuclear waste repositories as well as extending options in environmental geochemical and nuclear forensics studies. [ABSTRACT FROM AUTHOR]

Fast 8 MHz polarization modulation coupled with analytical modeling, fast beam-scanning, and synchronous digitization (SD) have enabled simultaneous nonlinear optical Stokes ellipsometry (NOSE) and polarized laser transmittance imaging with image acquisition rates up to video rate. In contrast to polarimetry, in which the polarization state of the exiting beam is recorded, NOSE enables recovery of the complexvalued Jones tensor of the sample that describes all polarization-dependent observables of the measurement. Every video-rate scan produces a set of 30 images (10 for each detector with three detectors operating in parallel), each of which corresponds to a different polarization-dependent result. Linear fitting of this image set contracts it down to a set of five parameters for each detector in second harmonic generation (SHG) and three parameters for the transmittance of the incident beam. These parameters can in turn be used to recover the Jones tensor elements of the sample. Following validation of the approach using z-cut quartz, NOSE microscopy was performed for microcrystals of both naproxen and glucose isomerase. When weighted by the measurement time, NOSE microscopy was found to provide a substantial (>7 decades) improvement in the signal-to-noise ratio relative to our previous measurements based on the rotation of optical elements and a 3-fold improvement relative to previous single-point NOSE approaches. [ABSTRACT FROM AUTHOR]

A dual quinone tagging strategy is designed for quantitation of cysteine-containing peptide (CCP) with MALDI-TOF mass spectrometry. The quinone compounds can rapidly and specifically bind to the thiol group of cysteine residues by a Michael addition reaction, which is used to identify both CCP and the number of cysteine residues in CCP through the direct observation of untagged and tagged products. After reduced with DL-dithiothreitol, the intramolecular disulfide bond can also be identified. Using benzoquinone (BQ) and methylp- benzoquinone (MBQ) as dual tags and a peptide with an amino acid sequence of SSDQFRPDDCT (C-pep1) as a model target, respectively, the quantitation strategy is performed through the intensity ratio of MBQ-tagged C-pep1 to BQ-tagged C-pep1 as the internal standard. The logarithm value of the intensity ratio is proportional to C-pep1 concentration in a range from 5.0 to 5000 nM. The limit of detection is as low as 2.0 nM. The proposed methodology provides a novel tool for rapid characterization, identification, and quantitation of biomolecules containing thiol reactive sites and has a promising application in the large-scale detection and analysis of cysteine-containing biomolecules. [ABSTRACT FROM AUTHOR]

Matrix-assisted laser desorption ionization (MALDI) imaging is gaining popularity, but matrix effects such as mass spectral interference and damage to the sample limit its applications. Replacing traditional matrices with silver particles capable of equivalent or increased photon energy absorption from the incoming laser has proven to be beneficial for low mass analysis. Not only can silver clusters be advantageous for low mass compound detection, but they can be used for imaging as well. Conventional matrix application methods can obstruct samples, such as fingerprints, rendering them useless after mass analysis. The ability to image latent fingerprints without causing damage to the ridge pattern is important as it allows for further characterization of the print. The application of silver clusters by soft-landing ion mobility allows for enhanced MALDI and preservation of fingerprint integrity. [ABSTRACT FROM AUTHOR]

Understanding cellular metabolism is a major challenge in current systems biology and has triggered extensive metabolomics research, which in most cases involves destructive analysis. However, the information obtainable only in a nondestructive manner will be required for accurately mapping the global structure of the organism's metabolic network at a given instant. Here we report that metabolic pathways can be explored in vivo by mixed stable isotope-labeled Raman microspectroscopy in conjunction with multivariate curve resolution analysis. As a model system, we studied ergosterol biosynthesis in single living fission yeast cells grown in mixtures of normal and 13C-labeled glucose as the sole carbon source. The multivariate spectral data analysis of space-resolved Raman spectra revealed the intrinsic spectra and relative abundances of all isotopomers of ergosterol whose carbon atoms in the 5,7-diene moiety of the sterol skeleton are either partly or fully substituted with 13C. Our approach is applicable to other metabolites and will earn a place in the toolbox of metabolomic analysis. [ABSTRACT FROM AUTHOR]

Using raw GC/MS data as the X-block for chemometric modeling has the potential to provide better classification models for complex samples when compared to using the total ion current (TIC), extracted ion chromatograms/profiles (EIC/EIP), or integrated peak tables. However, the abundance of raw GC/MS data necessitates some form of data reduction/feature selection to remove the variables containing primarily noise from the data set. Several algorithms for feature selection exist; however, due to the extreme number of variables (106-108 variables per chromatogram), the feature selection time can be prolonged and computationally expensive. Herein, we present a new prefilter for automated data reduction of GC/MS data prior to feature selection. This tool, termed unique ion filter (UIF), is a module that can be added after chromatographic alignment and prior to any subsequent feature selection algorithm. The UIF objectively reduces the number of irrelevant or redundant variables in raw GC/MS data, while preserving potentially relevant analytical information. In the m/z dimension, data are reduced from a full spectrum to a handful of unique ions for each chromatographic peak. In the time dimension, data are reduced to only a handful of scans around each peak apex. UIF was applied to a data set of GC/MS data for a variety of gasoline samples to be classified using partial least-squares discriminant analysis (PLS-DA) according to octane rating. It was also applied to a series of chromatograms from casework fire debris analysis to be classified on the basis of whether or not signatures of gasoline were detected. By reducing the overall population of candidate variables subjected to subsequent variable selection, the UIF reduced the total feature selection time for which a perfect classification of all validation data was achieved from 373 to 9 min (98% reduction in computing time). Additionally, the significant reduction in included variables resulted in a concomitant reduction in noise, improving overall model quality. A minimum of two um/z and scan window of three about the peak apex could provide enough information about each peak for the successful PLS-DA modeling of the data as 100% model prediction accuracy was achieved. It is also shown that the application of UIF does not alter the underlying chemical information in the data. [ABSTRACT FROM AUTHOR]

Spectral chemical sensing with digital color analysis by using consumer imaging devices could potentially revolutionize personalized healthcare. However, samples with small spectral variations often cannot be differentiated in color due to the nonlinearity of color appearance. In this study, we address this problem by exploiting the color image formation mechanism in digital photography. A close examination of the color image processing pipeline emphasizes that although the color can be represented digitally, it is still a reproducible subjective perception rather than a measurable physical property. That makes it possible to physically manage the color appearance of a nonradiative specimen through engineered illumination. By using scattering light imaging of gold nanoparticles (GNPs) as a model system, we demonstrated via simulation that enlarged color difference between spectrally close samples could be achieved with actively controlled illumination of multiple narrow-band light sources. Experimentally, darkfield imaging results indicate that color separation of single GNPs with various sizes can be significantly improved and the detection limit of GNP aggregation-based colorimetric assays can be much reduced when the conventional spectrally continuous white light was replaced with three independently intensity-controlled laser beams, even though the laser lines were uncorrelated with the LSPR maxima of the GNPs. With low-cost narrow-band light sources widely available today, this actively controlled illumination strategy could be utilized to replace the spectrometer in many spectral sensing applications. [ABSTRACT FROM AUTHOR]

The development of techniques to probe interfacial molecular transport is important for understanding and optimizing surface-based analytical methods including surface-enhanced spectroscopies, biological assays, and chemical separations. Single-molecule-fluorescence imaging and tracking has been used to measure lateral diffusion rates of fluorescent molecules at surfaces, but the technique is limited to the study of slower diffusion, where molecules must remain relatively stationary during acquisition of an image in order to build up sufficient intensity in a spot to detect and localize the molecule. Although faster time resolution can be achieved by fluorescence-correlation spectroscopy (FCS), where intensity fluctuations in a small spot are related to the motions of molecules on the surface, long-lived adsorption events arising from surface inhomogeneity can overwhelm the correlation measurement and mask the surface diffusion of the moving population. Here, we exploit a combination of these two techniques, imaging-FCS, for measurement of fast interfacial transport at a model chromatographic surface. This is accomplished by rapid imaging of the surface using an electron-multiplied-charged-coupled-device (CCD) camera, while limiting the acquisition to a small area on the camera to allow fast framing rates. The total intensity from the sampled region is autocorrelated to determine surface diffusion rates of molecules with millisecond time resolution. The technique allows electronic control over the acquisition region, which can be used to avoid strong adsorption sites and thus minimize their contribution to the measured autocorrelation decay and to vary the acquisition area to resolve surface diffusion from adsorption and desorption kinetics. As proof of concept, imaging-FCS was used to measure surface diffusion rates, interfacial populations, and adsorption-desorption rates of 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine (DiI) on planar C18- and C1-modified surfaces. [ABSTRACT FROM AUTHOR]

We present a novel high throughput photocatalyst efficiency assessment method based on 96-well microplates and UV-vis spectroscopy. We demonstrate the reproducibility of the method using methyl orange (MO) decomposition and compare kinetic data obtained with those provided in the literature for larger conventional photoreactors. To demonstrate the capabilities of the method, we rapidly screened the effects of salts, potentially present in wastewater, on kinetic rates of MO decomposition and briefly discuss the obtained data on the basis of existing literature. [ABSTRACT FROM AUTHOR]