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Comprehensive two-dimensional gas chromatography coupled with mass spectrometry (GC × GC–MS) has great potential for analyses of complicated mixtures and sample matrices, due to its separation power and possible high resolution. The second component of the measurement results, the mass spectra, is reproducible. However, the reproducibility of two-dimensional chromatography is affected by many factors and makes the evaluation of long-term experiments or cross-laboratory collaborations complicated. This paper presents a new open-source data alignment tool to tackle the problem of retention time shifts — with 5 different algorithms implemented: BiPACE 2D, DISCO, MSort, PAM, and TNT-DA, along with Pearson's correlation and dot product as optional methods for mass spectra comparison. The implemented data alignment algorithms and their variations were tested on real samples to demonstrate the functionality of the presented tool. The suitability of each implemented algorithm for significantly/non-significantly shifted data was discussed on the basis of the results obtained. For the evaluation of the "goodness" of the alignment, Kolmogorov–Smirnov test values were calculated, and comparison graphs were generated. The DA_2DChrom is available online with its documentation, fully open-sourced, and the user can use the tool without the need of uploading their data to external third-party servers. [ABSTRACT FROM AUTHOR]

This paper reports on an inkjet printing method for the fabrication of lateral flow immunochromatographic devices made from a single piece of filter paper by patterning microfluidic channels and dispensing immunosensing inks, requiring only a single printing apparatus. This “paperfluidic” immunosensing device allows for a less time-consuming and more low-cost fabrication compared with the conventional immunochromatographic strips requiring multiple pads, plastic or nylon backing, and a plastic case. A sandwich immunoreaction was performed on the patterned immunosensing paper device, and the sensitivity of the device was optimized with an IgG model analyte. Inkjet-printed antibodies on the test line and the control line were immobilized by physical adsorption, resulting in a very simple fabrication method applicable for pure cellulose surfaces. The color intensity in the test line and the control line was determined both by naked eye and by means of a color scanner in combination with a simple computer program. With the resulting paperfluidic immunosensing device, human IgG concentrations at least down to 10 μg/l could be detected within 20 min. Additionally, in order to demonstrate the feasibility of a total multianalyte sensing system, a combined immuno-chemical sensing device was also fabricated by patterning an additional microfluidic channel for a chemical assay onto the same paper substrate. This low-cost multianalyte paperfluidic sensing device thus demonstrates the feasibility of simple, portable, and disposable tools for pathogen detection in the field of medical, environmental, and food analyses, possibly resulting in useful devices in remote settings and less-industrialized countries. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The present paper describes an original method for the online preconcentration and analysis of ring-substituted amphetamines in urine samples, used on the integration of robot-assisted hollow fiber liquid-phase microextraction (HF-LPME), high-performance liquid chromatography (HPLC), and fluorescence detection (FLD). A lab-made autosampler, actuating a 100-μL syringe and equipped with a three-way solenoid microvalve, allowed the acceptor phase to flow through and be withdrawn from the lumen fiber, enabling the automated online transference of the enriched acceptor phase for chromatographic analysis, through a six-port switching valve. The developed online HF-LPME-LC/FLD method demonstrated high analytical throughput and confidence, facilitating the efficient extraction and determination of the target analytes, with minimal solvent consumption and sample manipulation, in a straightforward way. Sample cleanup, analyte uptake, and analysis were carried out in 14.5 min. Under optimal conditions, automated online HF-LPME showed excellent linearity, precision, and trueness, obtaining intraday RSDs between 2.9 and 9.2% (n = 6) and interday RSDs between 5.3 and 9.3% (n = 6). Enrichment factors (EFs) ranged between 14.2 and 15.7, extraction recoveries (ERs) ranged between 17.7 and 19.5%, and the limits of detection (S/N = 3) were 2.0, 3.0, and 3.0 μg L−1 for MDA, MDMA, and MDEA, respectively. The method proved to be an effortless, rapid, reliable, and environment-friendly approach for the determination of drug abuse in urine samples. [ABSTRACT FROM AUTHOR]

Engineered nanoparticles (ENP) are increasingly being incorporated into consumer products and reaching the environment at a growing rate. Unfortunately, few analytical techniques are available that allow the detection of ENP in complex environmental matrices. The major limitations with existing techniques are their relatively high detection limits and their inability to distinguish ENP from other chemical forms (e.g. ions, dissolved) or from natural colloids. Of the matrices that are considered to be a priority for method development, ENP are predicted to be found at relatively high concentrations in wastewaters and wastewater biosolids. In this paper, we demonstrate the capability of hydrodynamic chromatography (HDC) coupled to inductively coupled plasma mass spectrometry (ICPMS), in its classical and single particle modes (SP ICPMS), to identify ENP in wastewater influents and effluents. The paper first focuses on the detection of standard silver nanoparticles (Ag NP) and their mixtures, showing that significant dissolution of the Ag NP was likely to occur. For the Ag NP, detection limits of 0.03 μg L were found for the HDC ICPMS whereas 0.1 μg L was determined for the HDC SP ICPMS (based on results for the 80 nm Ag NP). In the second part of the paper, HDC ICPMS and HDC SP ICPMS were performed on some unspiked natural samples (wastewaters, river water). While nanosilver was below detection limits, it was possible to identify some (likely natural) Cu nanoparticles using the developed separation technology. [ABSTRACT FROM AUTHOR]

Data independent acquisition (DIA) attempts to provide comprehensive MS/MS data while providing a cycle time that is capable of following the elution profile of chromatographic peaks. Currently available MS technology is not yet fully capable of fulfilling these expectations. This paper suggests a new multiplex-based approach to more closely achieve this objective. Customized scans have been programmed for a Q Orbitrap instrument. Multiple nonadjacent mass range segments are sequentially collected (cut out) by the quadrupole. These combined mass ranges undergo fragmentation, and the resulting product ions are analyzed as a whole by the Orbitrap analyzer. The systematical variation of the mass range segments (nested design) permits the mathematical assignment of the observed product ions within a narrow precursor mass range. The proposed approach allows the use of mass windows that are narrower than those in conventional DIA (SWATH). A unique aspect of the proposed approach is the fact that halving the mass window width requires the addition of only a single multiplexed scan. This is different from conventional DIA, which requires the number of mass windows to be doubled in order to achieve the same objective. This paper shows that for a given cycle time, the proposed nested DIA technique produces significantly less chimeric product ion spectra than conventional DIA. However, further improvements from the programming, and most likely the hardware side, are still required in order to achieve the aim of comprehensive MS/MS. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

This paper proposed a newly developed heart-cutting two-dimensional supercritical fluid chromatography-high-performance liquid chromatography system coupled to tandem mass spectrometry (SFC-HPLC-MS/MS) for the determination of four tobacco-specific nitrosamines (TSNAs) in cigarette mainstream smoke. The orthogonality of five SFC columns and two HPLC columns was evaluated. The 1-AA column was applied for the first dimensional (1D) SFC separation to isolate the target compounds from the complex cigarette smoke matrices, and a trapping column in conjunction with an isocratic pump was employed to capture the 1D elutes. Then, the trapped 1D elutes were transferred into the C18 column through a two-position/six-port valve for the second dimensional (2D) analysis. The ion suppression was significantly reduced by the established SFC-HPLC system; meanwhile, the matrix interferences were eliminated as the results demonstrated. A dynamic range between 0.1 and 20 ng/mL was achieved with LOQs of 0.72 μg/cig for N-nitrosonornicotine (NNN), 0.66 μg/cig for nicotine-derived nitrosamine ketone (NNK), 0.81 μg/cig for N-nitrosoanatabine (NAT), and 0.39 μg/cig for N-nitrosoanabasine (NAB). All the results revealed that the presented method exhibited good repeatabilities and recoveries and could be used as a rapid and reliable approach for routine analysis of TSNAs in mainstream smoke. [ABSTRACT FROM AUTHOR]

With the number of approved biosimilars rapidly increasing in the various regulatory jurisdictions, public perception of safety and efficacy of these products have been gradually improving. Establishment of analytical similarity with the innovator product is a key aspect of biosimilar development. It serves as the basis for reduction in the size and/or scope of clinical trials. However, the clinical performance must be consistent with the innovator product. A considerable amount of effort precedes this exercise and requires a suitable reference material to support analytical method development. In view of the high cost as well as limited availability of innovator product in the market, there is a need for suitable reference material which could serve this purpose. The National Institute of Standards and Technology (NIST) have recently created NIST monoclonal antibody (NISTmAb) to support analytical method development and commercialization of monoclonal antibody-based biotherapeutics. In this paper, it is intended to evaluate lifecycle appropriate implementation of NISTmAb, a class-specific reference material in biosimilar analytical development. The results show that NISTmAb can be useful in developing initial platform analytical methods and as an external control for class-specific products. However, as expected, it cannot replace an innovator product or in-house product-specific reference material for analytical similarity assessment. As per regulatory guideline, a product-specific optimization will continue to be a prerequisite for specific analytical properties. [ABSTRACT FROM AUTHOR]

In this paper, electrochemical (EC) methods have been proposed to evaluate the oxidative behavior of drugs as rapid, simple, and cheap strategies to predict some metabolic features. Various commercial drugs belonging to different therapeutic families have been assayed to deal with a wide variety of biotransformations and to cover different metabolism extents. First, differential pulse voltammetry has been applied to evaluate the oxidative behavior of drugs. Voltammetric assays have demonstrated to be highly efficient to predict the metabolism extent from the current intensity data. The second objective of this work has been the comparison of metabolite profiles from both EC and in vitro methods based on liver microsome assays. The resulting samples have been analyzed by reversed-phase liquid chromatography mode using a core-shell column and UV detection. Chromatographic methods have been established for each particular drug and its metabolites using 0.1% (v/v) formic acid aqueous solution and methanol (MeOH) as the components of the mobile phase. Drug oxidation products from both EC- and microsome-based methodologies have been compared in terms of variety and percentage from the corresponding chromatographic profiles. In general, most of the metabolites occurring in vitro have also been reproduced in the EC runs. Besides, it has been found that compositional profiles from EC experiments are dependent on experimental variables such as pH and potential. In general, acid (pH 2) and basic (pH 10) conditions and too high potentials can contribute to the generation of oxidation artifacts which differ from metabolites while milder potentials and neutral pH values may reproduce more accurately the microsome patterns. The proposed methodology is suitable for a first study of the oxidative behavior of molecules that can be related to relevant metabolic properties. The obtained information could be of great interest to prioritize or discard compounds, as a first screening, on the research of drug candidates. [ABSTRACT FROM AUTHOR]

Fiber-based monoliths for use in liquid chromatographic separations are defined by columns packed with aligned fibers, woven matrices, or contiguous fiber structures capable of achieving rapid separations of proteins, macromolecules, and low molecular weight components. A common denominator and motivating driver for this approach, first initiated 25 years ago, was reducing the cost of bioseparations in a manner that also reduced residence time of retained components while achieving a high ratio of mass to momentum transfer. This type of medium, when packed into a liquid chromatography column, minimized the fraction of stagnant liquid and resulted in a constant plate height for non-adsorbing species. The uncoupling of dispersion from eluent flow rate enabled the surface chemistry of the stationary phase to be considered separately from fluid transport phenomena and pointed to new ways to apply chemistry for the engineering of rapid bioseparations. This paper addresses developments and current research on fiber-based monoliths and explains how the various forms of this type of chromatographic stationary phase have potential to provide new tools for analytical and preparative scale separations. The different stationary phases are discussed, and a model that captures the observed constant plate height as a function of mobile phase velocity is reviewed. Methods that enable hydrodynamically stable fiber columns to be packed and operated over a range of mobile phase flow rates, together with the development of new fiber chemistries, are shown to provide columns that extend the versatility of liquid chromatography using monoliths, particularly at the preparative scale. [ABSTRACT FROM AUTHOR]

A method for the determination of 1-hydroxypyrene in urine and hexachlorbenzene in water applying the regression triplet in the calibration procedure of chromatographic data has been applied. The detection limit and quantification limit are currently calculated on the basis of the standard deviation of replicate analyses at a single concentration. However, since the standard deviation depends on concentration, these single-concentration techniques result in limits that are directly dependent on spiking concentration. A more rigorous approach requires first careful attention to the three components of the regression triplet (data, model, method), examining (1) the data quality of the proposed model, (2) the model quality and (3) the least-squares method to be used for fulfilment of all least-squares assumptions. For high-performance liquid chromatography determination of 1-hydroxypyrene in urine and gas chromatography analysis of hexachlorbenzene in water, this paper describes the effects of deviations from five basic assumptions The paper considers the correction of deviations: identifying influential points, namely, outliers, the calibration task depends on the regression model used, and the least-squares method is based on the assumptions of the normality of the errors, homoscedasticity and the independence of errors. Results show that the approach developed provides improved estimates of analytical limits and that the single-concentration approaches currently in wide use are seriously flawed. [ABSTRACT FROM AUTHOR]

This paper describes the use of headspace solid-phase microextraction (SPME) combined with gas chromatography to identify the signature odors that law enforcement-certified detector dogs alert to when searching for drugs, explosives, and humans. Background information is provided on the many types of detector dog available and specific samples highlighted in this paper are the drugs cocaine and 3,4-methylenedioxy-N-methylamphetamine (MDMA or Ecstasy), the explosives TNT and C4, and human remains. Studies include the analysis and identification of the headspace "fingerprint" of a variety of samples, followed by completion of double-blind dog trials of the individual components in an attempt to isolate and understand the target compounds that dogs alert to. SPME–GC/MS has been demonstrated to have a unique capability for the extraction of volatiles from the headspace of forensic specimens including drugs and explosives and shows great potential to aid in the investigation and understanding of the complicated process of canine odor detection. Major variables evaluated for the headspace SPME included fiber chemistry and a variety of sampling times ranging from several hours to several seconds and the resultant effect on ratios of isolated volatile components. For the drug odor studies, the CW/DVB and PDMS SPME fibers proved to be the optimal fiber types. For explosives, the results demonstrated that the best fibers in field and laboratory applications were PDMS and CW/DVB, respectively. Gas chromatography with electron capture detector (GC/ECD) and mass spectrometry (GC/MS) was better for analysis of nitromethane and TNT odors, and C-4 odors, respectively. Field studies with detector dogs have demonstrated possible candidates for new pseudo scents as well as the potential use of controlled permeation devices as non-hazardous training aids providing consistent permeation of target odors. [ABSTRACT FROM AUTHOR]

This paper aims at developing a general strategy to study the detection of adducts of drugs with DNA. In particular, ethacrynic acid has been chosen as a model reactive drug that could be able to bind covalently to DNA bases. Such interactions were detected by ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS). Principal component analysis (PCA) was applied as an unsupervised method to try to find the potential candidate adduct from MS features. The occurrence of adducts was investigated preliminarily using deoxynucleosides of the guanine, cytosine, adenine, and thymine separately as a way to optimize both separation and detection conditions. Interpretations of MS and MS/MS spectra provided tentative structures of the compounds formed. Conclusions extracted from such simple nucleoside models were further extended to the analysis of DNA adducts. For such a purpose, DNA was incubated in the presence of ethacrynic acid under appropriate experimental conditions and its further enzymatic hydrolysis released the corresponding nucleosides. UHPLC-MS analysis of the resulting test samples under the SRM detection mode confirmed the presence of ethacrynic acid derivatives of nucleosides occurring at very low concentration levels, thus proving the overall performance of the method. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Concern about the presence of emerging contaminants in the environment has increased because biological activity at low concentrations has been observed. The difficulty of detecting and quantifying these compounds encourages the development of analytical methods with highly sensitive and selective analytical procedures. Pharmaceuticals, pesticides, and industrial chemicals are used and finally discarded to the environment. This paper provides a rapid and sensitive analytical method for the quantification of eight emerging contaminants (carbamazepine, carbofuran, bisphenol A, diuron, 17 α ethinylestradiol, ametryn, carbazole, and triclosan). A two-level full factorial design for optimization of chromatographic separation and sample preparation was performed. The separation using a monolithic column (Onyx C18) achieved baseline resolution for all compounds in 4.6 min. The optimized sample treatment involved a preconcentration step by means of solid-phase extraction using HF Bond Elut-C18 cartridges, achieving an enrichment factor of 2222. Under optimum conditions, good linearity was obtained with a correlation coefficient higher than 0.999. The limits of detection and quantification for carbamazepine, carbofuran, bisphenol A, diuron, 17 α ethinylestradiol, ametryn, and carbazole were in the range of 0.01-208.7 and 0.03-695.7 ng L, respectively, and for triclosan, the limit of detection and quantification was 0.67 and 2.25 μg L, respectively. Precision evaluated as relative standard deviations was lower than 15 %. The proposed method was found robust. Finally, the method was successfully applied to superficial water samples. [ABSTRACT FROM AUTHOR]

This paper describes a new method for the determination of polar triazines, including some degradation products, which combines online in-tube solid-phase microextraction (IT-SPME) and capillary liquid chromatography with UV-diode array detection (DAD). Different extractive coatings have been evaluated for IT-SPME, a capillary column with a polydimethylsiloxane (PDMS) coating, and the same coating modified with carboxylated single-wall carbon nanotubes (c-SWCNTs) and carboxylated multiwall carbon nanotubes (c-MWCNTs). On the basis of the results obtained, a new method is presented for the identification and determination of triazines in water samples. A careful selection of the eluent composition provides the required selectivity and sensitivity for the quantification of the target analytes, even those highly polar (log K ≤ 2.3). The proposed conditions have been successfully used for the quantitation of the analytes in the 0.25-50.0 μg L range. The limits of detection (LODs) are in the 0.02-0.1 μg L range, and the intraday and interday relative standard deviation (RSD) coefficients are ≤9 and ≤17 %, respectively. The reliability of the described method has been tested by analyzing several real water samples. The proposed method can be considered an environmentally friendly and cost-effective alternative for routine monitoring of triazines and their degradation products in waters. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In this paper, we describe the findings of a study aimed at assessing the detection sensitivity of comprehensive two-dimensional high-performance liquid chromatography (LCxLC) separation of a degraded active pharmaceutical ingredient (API) with UV absorption as the detection technique. Specifically, we have examined the impact of the volume and solvent composition (referred to as 'interface conditions') of fractions of first-dimension column effluent transferred to the second dimension for further separation on the ability to resolve and detect low-abundance compounds. Historically, LCxLC has been perceived as being inferior to 1D-LC from the point of view of detection sensitivity. In this work, we demonstrate that LCxLC is sufficiently sensitive to be useful in the pharmaceutical context where in general impurities present at 0.05 % (relative to the API concentration) should be quantified. Moreover, we find that this level of sensitivity is only attained under certain conditions: dilution of the first column effluent with weak solvent (water in this case) prior to injection into the second-dimension column is very beneficial because it promotes focusing of the analyte band in the second column, thereby improving the detection sensitivity of the LCxLC system; and, quantitation limits are also a strong function of peak location in the second-dimension separation window, where baseline disturbances near the dead time of the second column can limit reliable detection of low-abundance compounds. [ABSTRACT FROM AUTHOR]

Size-exclusion chromatography (SEC) enables measurement of the average molecular weights and molecular-weight distributions of polymers. Because these characteristics may, in turn, be correlated with important performance characteristics of plastics, SEC is an essential analytical technique for characterization of macromolecules. Although SEC is one of the oldest instrumental chromatographic techniques, it is still under continuous development, as a result of the great demand for increased resolution and faster analysis in SEC. Ultra-high-pressure size-exclusion chromatography (UHPSEC) was recently introduced to satisfy the growing demands of analytical chemists. Using instrumentation capable of generating very high pressures and columns packed with small particles, this technique enables greater separation efficiency and faster analysis than are achieved with conventional SEC. UHPSEC is especially advantageous for high-resolution analysis of oligomers, for very rapid polymer separations, and as a second dimension in comprehensive two-dimensional liquid chromatography of polymers. In this paper we discuss the benefits of UHPSEC for separation of macromolecules, with examples from the literature. [ABSTRACT FROM AUTHOR]

The rapid development of protein-based pharmaceuticals highlights the need for robust analytical methods to ensure their quality and stability. Among proteins used in pharmaceutical applications, an important and ever increasing role is represented by monoclonal antibodies and large proteins, which are often modified to enhance their activity or stability when used as drugs. The bioactivity and the stability of those proteins are closely related to the maintenance of their complex structure, which however are influenced by many external factors that can cause degradation and/or aggregation. The presence of aggregates in these drugs could reduce their bioactivity and bioavailability, and induce immunogenicity. The choice of the proper analytical method for the analysis of aggregates is fundamental to understand their (size) dimensional range, their amount, and if they are present in the sample as generated by an aggregation or as an artifact due to the method itself. Size exclusion chromatography is one of the most important techniques for the quality control of pharmaceutical proteins; however, its application is limited to relatively low molar mass aggregates. Among the techniques for the size characterization of proteins, field-flow fractionation (FFF) represents a competitive choice because of its soft mechanism due to the absence of a stationary phase and application in a broader size range, from nanometer- to micrometer-sized analytes. In this paper, the microcolumn variant of FFF, the hollow-fiber flow FFF, was online coupled with multi-angle light scattering, and a method for the characterization of aggregates with high reproducibility and low limit of detection was demonstrated employing an avidin derivate as sample model. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

This paper describes the retention behavior of oligolysine and oligoarginine peptides of different lengths as a function of heptafluorobutyric acid (HFBA) concentration in ion-pairing reversed-phase chromatography in isocratic elution. A mixture of oligolysine and a mixture of oligoarginine with number of amino acid residues (dp) from two to eight were conveniently prepared by one-pot protease-catalyzed synthesis. Analysis of the logarithm of the retention factor k as a function of [HFBA] for each oligopeptide component, using a closed pairing model, provided values for (1) number ( n) of paired HFBA anions per peptide molecule, (2) equilibrium constant ( Kip,m) for ion pairing between oligopeptides and HFBA anions, and (3) product of the phase ratio and the distribution constant of the paired oligopeptide between the mobile and stationary phases ( βKd,ip). We found that βKd,ip of oligoarginine is larger compared with oligolysine having the same dp. A linear relationship was obtained for ln βKd,ip as a function of n +  g · dp. By optimizing constant g separately for oligolysine and oligoarginine, we determined that g is larger for oligoarginine, in agreement with the higher hydrophobicity of arginine residues. Plotting the fraction of paired oligoarginine and oligolysine as a function of [HFBA] shows that the cooperative effect in forming ion pairs is greater for oligoarginine than oligolysine. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

This paper investigates the performance of a column classification system developed at the Katholieke Universiteit Leuven applied to pharmaceutical chromatographic analyses. The liquid chromatography assay of lamotrigine and related compounds was carried out according to the method prescribed in the European Pharmacopoeia monograph, using 28 brands of stationary phases. A ranking was built based on the F value calculated against the selected reference column, then compared with the column test performance established for the stationary phases studied. Therefore, the system suitability test prescribed by the European Pharmacopoeia in order to distinguish between suitable or unsuitable columns for this analysis was evaluated. Moreover, it was examined whether the classes of the stationary phases, determined using test parameter results, contain either suitable or unsuitable supports for the lamotrigine separation. This assay was performed using chemometric a technique, namely factor analysis. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Various implementations of two-dimensional high-performance liquid chromatography are increasingly being developed and applied to the analysis of complex materials, including those encountered in the analysis of foods, beverages, and nutraceuticals. Previously, we introduced the concept of selective comprehensive two-dimensional liquid chromatography (sLC × LC) as a hybrid between the more conventional, but extreme opposite sampling modes of heartcutting (LC-LC) and fully comprehensive (LC × LC) 2D separation. The sLC × LC approach breaks the link between first dimension (D) sampling time and second dimension (D) analysis time that is faced in LC × LC and allows very rapid (as low as 1 s) sampling of highly efficient D separations, while at the same time allowing efficient D separations on the timescale of tens of seconds. In this paper, we improve upon our previous sLC × LC work by demonstrating the ability to perform the processes of D sampling and D separation in parallel. This significantly improves the flexibility of the technique and allows targeted analysis of analytes that elute close together in time in the D separation. To demonstrate the value of this added capability, we have developed a sLC × LC method using multi-wavelength ultraviolet absorbance detection for the quantitative analysis of six target furanocoumarin compounds in extracts of celery, parsley, and parsnips. We show that D separations of D effluent containing the target compounds of interest reveal the presence of unanticipated interferent peaks that would otherwise compromise the quantitative accuracy of the method. We also demonstrate the application of the chemometric method iterative key set factor analysis with alternating least-squares to sLC × LC to mathematically resolve target compounds that are only slightly separated chromatographically but not sufficiently resolved for accurate quantitation. [ABSTRACT FROM AUTHOR]

This paper describes the characterisation of liposome-type nanoparticles (NPs) dispersed in a beverage matrix. Characterisation is based on a two-step procedure: first, liposomes are separated on the basis of size in the nanometre range by use of hydrodynamic chromatography (HDC); second, chemical characterisation is performed by use of MALDI-TOF mass spectrometry (MS). Characterisation of three types of Coatsome liposome, a commercially available type of empty liposome, was investigated. All three liposome types, Coatsome A = anionic, N = neutral, and C = cationic, gave single peaks in HDC, reflecting diameters of 153, 187, and 205 nm, respectively. Subsequent MALDI-TOF MS in positive mode furnished major signals at m/ z = 734.5 ([M + H] adduct) and m/ z = 756.6 ([M + Na] adduct) of l-(α)-dipalmitoylphosphatidylcholine (DPPC) monomer and dimeric adducts at m/ z = 1468.1 and m/ z = 1490.1, respectively. MALDI-TOF MS in negative mode gave a signal at m/ z = 721.3 ([M − H] adduct) of l-(α)-dipalmitoylphosphatidylglycerol (DPPG), except for Coatsome C which lacks this phospholipid. After HDC separation of Coatsome A NPs the major DPPC and DPPG signals can be detected in the expected fractions by use of MALDI-TOF MS in positive and negative modes, respectively. Validation of the analytical strategy revealed linearity ( R > 0.99), repeatability (relative standard deviation <10 %), and reproducibility (relative standard deviation between days <10 %) were good, recovery was 61 ± 5 %, and the limit of quantification was 1 mg mL in this matrix. With 4 mg Coatsome A mL 20 out of 20 samples furnished the 734.5 and 756.6 signals typical of DPPC in MALDI-TOF MS characterisation. [ABSTRACT FROM AUTHOR]

Size, weight and position are three of the most important parameters that describe a molecule in a biological system. Ion mobility spectrometry is capable of separating molecules on the basis of their size or shape, whereas imaging mass spectrometry is an effective tool to measure the molecular weight and spatial distribution of molecules. Recent developments in both fields enabled the combination of the two technologies. As a result, ion-mobility-based imaging mass spectrometry is gaining more and more popularity as a (bio-)analytical tool enabling the determination of the size, weight and position of several molecules simultaneously on biological surfaces. This paper reviews the evolution of ion-mobility-based imaging mass spectrometry and provides examples of its application in analytical studies of biological surfaces. [ABSTRACT FROM AUTHOR]

ymmetric flow field-flow fractionation (AsFlFFF) and high-performance size-exclusion chromatography (HPSEC) are techniques for separating and characterizing macromolecules; until now the latter is more utilized for analyzing polysaccharides. The demand for characterizing complex, high-molar-mass polysaccharides has raised interest in the use of AsFlFFF in analyzing polymeric carbohydrates in addition to HPSEC. In this paper, we compare the behavior of arabinoxylan aggregates present in aqueous solution in AsFlFFF and HPSEC and their effect on the obtained molecular characteristics (molar mass averages and size). Although the amount of aggregates in aqueous arabinoxylan solutions may be low, their role needs to be understood to avoid erroneous interpretations of AsFlFFF and HPSEC data. When these two separation systems were compared, AsFlFFF seemed to possess more separation power for the differentiation of aggregates from individual chains than HPSEC. To our knowledge, this is the first report on the characterization of xylans with AsFlFFF. [ABSTRACT FROM AUTHOR]

This paper describes an analytical three-capillary viscometer detector that eliminates the traditional viscometer 'hold-up' volume (commonly found in four-capillary designs) while maintaining cancellation of short-term pump noise and long-term baseline drift of temperature and solvent flow rate that are inherent in chromatography systems. This improvement allows a staggered sample injection approach in chromatography, yielding a significant increase in sample throughput by cutting down the chromatographic run time. It also provides a more robust design as it does not require capillary rebalancing, complex purging, flushing or changing the hold-up volume to accommodate long-term chromatographic use. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In this paper, the effect of temperature is investigated on the performance of glycoprotein enrichment by boronic acid lectin affinity chromatography (BLAC). Wheat germ agglutinin and m-aminophenyl boronic acid containing stationary phases were evaluated individually and in a mixed mode using an automated liquid handling robot with an integrated 96-well plate temperature controller. Glycoaffinity enrichment of the model proteins of ribonuclease B and trypsin inhibitor was investigated in the presence of the non-glycosylated proteins of myoglobin (neutral) and lysozyme (basic) at a wide temperature range of 5–65 °C. Our results revealed that glycoaffinity micropartitioning at the temperature of 25 °C provided the highest recovery rate for glycoprotein enrichment. We have also found that a large amount of lysozyme was present in the elution fractions of the m-aminophenyl boronic acid containing micropartitioning columns due to ion-exchange mechanism occurring between the positively charged protein and the negatively charged stationary phase at the operation pH. On the other hand, at high temperature (65 °C), non-specific interactions with the agarose carrier prevailed, evidenced by the presence of myoglobin in the eluate. [ABSTRACT FROM AUTHOR]

Computer-assisted optimization of chromatographic separations is still a fruitful activity. In fact, advances in computerized data handling should make the application of systematic optimization strategies much easier. However, in most contemporary applications, the optimization criterion is not considered to be a key issue (Vanbel, J Pharm Biomed, 21:603–610, ). In this paper, an update of the importance of selecting adequate criteria in chromatographic separation is presented. [ABSTRACT FROM AUTHOR]

The carbamates are a well-known thermosensible pesticides class, which are highly prone to degradation via fragmentation and/or rearrangement mechanisms leading to a difficult direct gas chromatography (GC) analysis, i.e., without derivatization. In this paper, spermine and thiabendazole both at 1 mg/mL were highlighted as efficient analyte protectants to improve the direct and simultaneous analysis of 16 carbamates both in solvent and green vegetable matrices. These two molecules were compared in mixture or in combination with three well-known efficient analyte protectants 3-ethoxy-1,2-propanediol, d-sorbitol, and l-gulonic acid-γ-lactone. The potential benefits were investigated in GC hyphenated to mass spectrometry (GC–MS) with two injection modes: programmable temperature vaporizing injector in a solvent split mode (PTV-SSI) and on-column injection (OCI). It was shown that the combined effect of the five protective agents led to the best sensitivity improvement with limits of detection between 0.1–0.4 and 0.03–0.1 μg/kg and limits of quantification between 0.3–1.1 and 0.1–0.5 μg/kg for PTV-SSI and OCI mode, respectively. The correlation coefficients from the analyzed 1–500 μg/kg range were all >0.999 both in the solvent and matrices studied. The recoveries of carbamates from three spiked matrices over five replicates at 20 and 100 µg/kg were in the range 90–107% with relative standard deviation (RSD) equal to 2–7% for PTV-SSI and 92–107% with an RSD equal to 1–6% for OCI. The use of spermine and thiabendazole with other analyte protectants shows very efficient partial or total reduction of breakdown of the most sensitive carbamates such as the N-sulfenylated ones. [ABSTRACT FROM AUTHOR]

This paper describes a fully automated on-line method combining in-tube solid-phase microextraction (SPME) in which sample clean-up and enrichment are conducted through an open tubular fused-silica capillary column and high-performance liquid chromatography (HPLC)/tandem mass spectrometry (MS/MS) detection for the determination of six butyrophenone derivatives (moperone, floropipamide, haloperidol, spiroperidol, bromperidol, and pimozide) in human plasma samples. The six butyrophenones were extracted by repeatedly aspirating and dispensing plasma sample solutions on a DB-17 capillary column (60 cm × 0.32 mm i.d., film thickness 0.25 µm). The analytes retained on the inner surface of the capillary column were then eluted into an acetonitrile-rich mobile phase using a gradient separation technique. Extraction efficiencies ranged from 12.7% to 31.8% for moperone, spiroperidol, and pimozide, and from 1.08% to 4.86% for floropipamide, haloperidol, and bromperidol. The regression equations for all compounds showed excellent linearity, ranging from 0.05 to 50 ng/0.1 mL of plasma, except for moperone and spiroperidol (0.01 to 50 ng/0.1 mL). The limits of detection and quantification in plasma for each drug were 0.03–0.2 and 0.1–0.5 ng/mL, respectively. The intra- and inter-day coefficients of variation for all compounds in plasma were not greater than 13.7%. [ABSTRACT FROM AUTHOR]

Many aromatic compounds can be found in the environment as a result of anthropogenic activities and some of them are highly toxic. The need to determine low concentrations of pollutants requires analytical methods with high sensitivity, selectivity, and resolution for application to soil, sediment, water, and other environmental samples. Complex sample preparation involving analyte isolation and enrichment is generally necessary before the final analysis. The present paper outlines a novel, simple, low-cost, and environmentally friendly method for the simultaneous determination of p-nitrophenol (PNP), p-aminophenol (PAP), and hydroquinone (HQ) by micellar electrokinetic capillary chromatography after preconcentration by cloud point extraction. Enrichment factors of 180 to 200 were achieved. The limits of detection of the analytes for the preconcentration of 50-ml sample volume were 0.10 μg L−1 for PNP, 0.20 μg L−1 for PAP, and 0.16 μg L−1 for HQ. The optimized procedure was applied to the determination of phenolic pollutants in natural waters from San Luis, Argentina. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The present paper provides a detailed analysis of the analyte-wall adsorption effects in nanochannels, including a random walk study of the analyte-wall collision frequency, and uses these insights to estimate wall desorption times from chromatographic experiments in nanochannels. Using coumarin dye analytes and using a methanol/water mixture buffered at pH 3 in 120-nm deep channels, the surface desorption times on naked fused-silica glass were found to be maximally of the order of 60 to 150 μs, while they were found to be on the order of 100 to 500 μs on a hydrophobically coated wall. These nonzero adsorption and desorption times lead to an additional band broadening when conducting chromatographic separations. Shear-driven flows, requiring a noncoated moving wall and a stationary coated wall, intrinsically turn out to be more prone to this effect than pressure-driven or electro-driven flows for example. The present study also shows that, interestingly, the number of analyte-wall collisions increases with the inverse of the channel depth and not with its second power, as would be expected from the Einstein–Smoluchowski relationship for molecular diffusion. [ABSTRACT FROM AUTHOR]

In this paper, we describe the preparation and the evaluation of a porous graphitic carbon (PGC) column coated with a new dinaphthyl derivative of neamine for chiral ligand-exchange (LE) chromatography. It was shown that the graphitic surface/dinaphthyl anchor system efficiently (1.15 μmol/m2) and stably (three months of intensive use) adsorbs the neamine template onto the chromatographic support. The resulting coated PGC stationary phase showed appreciable LE-based enantioselective properties towards several native amino acids. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A Correction to this paper has been published: https://doi.org/10.1007/s00216-021-03544-9. [ABSTRACT FROM AUTHOR]

During the last few decades, increasing interest in biological surfactants led to an intensification of research for the cost-efficient production of biosurfactants compared with traditional petrochemical surface-active components. The quest for alternative production strains also is associated with new demands on biosurfactant analysis. The present paper gives an overview of existing analytical methods, based on the example of rhamnolipids. The methods reviewed range from simple colorimetric testing to sophisticated chromatographic separation coupled with detection systems like mass spectrometry, by means of which detailed structural information is obtained. High-performance liquid chromatography (HPLC) coupled with mass spectrometry currently presents the most precise method for rhamnolipid identification and quantification. Suitable approaches to accelerate rhamnolipid quantification for better control of biosurfactant production are HPLC analysis directly from culture broth by adding an internal standard or Fourier transform infrared attenuated total reflectance spectroscopy measurements of culture broth as a possible quasi-online quantification method in the future. The search for alternative rhamnolipid-producing strains makes a structure analysis and constant adaptation of the existing quantification methods necessary. Therefore, simple colorimetric tests based on whole rhamnolipid content can be useful for strain and medium screening. Furthermore, rhamnolipid purification from a fermentation broth will be considered depending on the following application. [ABSTRACT FROM AUTHOR]

In this paper, a time-based multicommutated flow system is proposed for appropriate selection and modulation of mobile phase composition in flow-injection (FI)/sequential-injection (SI) chromatography. The novel flow assembly involves the on-line coupling of a short monolithic reversed-phase chromatographic column with a multisyringe flow injection set-up furnished with a set of solenoid valves. The proposed hyphenated technique was applied to the simultaneous spectrophotometric determination of thiamine (B1), pyridoxine (B6) and cyanocobalamin (B12) which were taken as model analytes. The separation method capitalizes on a dual isocratic elution protocol involving the use of a single forward stroke of the multisyringe pump for initial delivery of 50 mmol L−1 ammonium acetate (pH 7.0) for 2.4 min followed by 50 mmol L−1 ammonium acetate–methanol (80:20, v/ v) for 6.4 min at 0.5 mL min−1 and room temperature. Detection was performed at the maximum wavelength for each target vitamin—280 nm for B1, 325 nm for B6, and 360 nm for B12. A first-order, two-level full-factorial design was utilized to ascertain the significant variables influencing the chromatographic separation and the magnitude of the interaction effects. The experimental design method revealed that resolution of the target vitamins is highly dependent on the pH, percentage of organic modifier, and their second-order interaction. The multisyringe flow-injection-based monolithic column separation method, which should be viewed as an expeditious and cost-effective alternative to the high-performance liquid chromatography counterpart, was applied to the separation and determination of B1, B6, and B12 in different pharmaceutical dosage forms in less than 9 min. Statistical comparison of the results from the proposed procedure with those from the HPLC method endorsed by the US Pharmacopeia revealed there were no significant differences at the 95 % confidence level. [ABSTRACT FROM AUTHOR]

The flavonoids and the terpene lactones are regarded as the two main active components of Ginkgo biloba that affect human health. In the work discussed in this paper, two analytical methods for the characterization of G. biloba authentic materials and commercial products, an LC–UV chromatographic fingerprinting method and a traditional flavonol quantification method, were compared. The traditional method was used to determine the total flavonol content (as glycosides) after acid hydrolysis. The fingerprinting method examined the chromatographic profiles of methanol–water extracts using chemometric methods. The traditional method showed that all the commercial products met the current voluntary standard of 24% flavonols by weight. The chromatographic fingerprinting method revealed significant variations in the commercial products with regard to the relative concentration of individual flavonols. [ABSTRACT FROM AUTHOR]

Evaporative light scattering detection (ELSD) is widely recognized as a universal tool for liquid and supercritical chromatographies. In addition, this detection technique is fully compatible with continuous-flow systems. In fact, the combination of continuous non-chromatographic techniques and ELSD affords the design of simple, reliable systems for extracting qualitative information. This paper reviews instrumental innovations regarding the miniaturization of evaporative light scattering detectors and their uses in micro and capillary liquid chromatography; also, it discusses their increasingly important role in the development of vanguard configurations for sample screening and the determination of total indices without the need for chromatographic separation. Moreover, it compares them with other types of chromatographic detectors in terms of performance. Finally, the potential of ELSD for solving real-life analytical problems arising from the need to meet (bio)chemical information needs is illustrated with various selected applications. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The use of a drug to modify a person’s behavior for criminal gain is not a recent phenomenon. However, the recent increase in reports of drug-facilitated crimes (sexual assault, robbery) has caused alarm in the general public. The drugs involved can be pharmaceuticals, such as benzodiazepines (flunitrazepam, lorazepam, etc.), hypnotics (zopiclone, zolpidem), sedatives (neuroleptics, some anti-H1) or anaesthetics ( γ-hydroxybutyrate, ketamine), drugs of abuse, such as cannabis, ecstasy or LSD, or more often ethanol. To perform successful toxicological examinations, the analyst must follow some important rules: (1) obtain as soon as possible the corresponding biological specimens (blood and urine); (2) collect hair about 1 month after the alleged event; (3) use sophisticated analytical techniques (gas or liquid chromatography coupled to tandem mass spectrometry, MS/MS, headspace gas chromatography); and (4) take care in the interpretation of the findings. Drugs used to facilitate sexual assaults can be difficult to detect (active products at low doses, chemical instability), possess amnesic properties and can be rapidly cleared from the body (short half-life). In these situations, blood or even urine can be of low interest. This is the reason why some laboratories have developed an original approach based on hair testing. Hair was suggested as a valuable specimen in situations where, as a result of a delay in reporting the crime, natural processes have eliminated the drug from typical biological specimens. While there are a lot of papers that have focused on the identification of drugs in hair following chronic drug use, those dealing with a single dose are very scarce. The experience of the author and a review of the existing literature will be presented for cases involving benzodiazepines, hypnotics, γ-hydroxybutyrate and various sedatives or chemical weapons. The expected concentrations in hair are in the low picogram/milligram range for most compounds. Hair analysis may be a useful adjunct to conventional drug testing in sexual assault. It should not be considered as an alternative to blood and urine analyses, but as a complement. This approach may find useful applications, but the definition of legally defensible cutoff values would require much more data. MS/MS technologies appear as a prerequisite in drug-facilitated cases. [ABSTRACT FROM AUTHOR]

Solid-phase microextraction (SPME) is a miniaturized and solvent-free sample preparation technique for chromatographic–spectrometric analysis by which the analytes are extracted from a gaseous or liquid sample by absorption in, or adsorption on, a thin polymer coating fixed to the solid surface of a fiber, inside an injection needle or inside a capillary. In this paper, the present state of practical performance and of applications of SPME to the analysis of blood, urine, oral fluid and hair in clinical and forensic toxicology is reviewed. The commercial coatings for fibers or needles have not essentially changed for many years, but there are interesting laboratory developments, such as conductive polypyrrole coatings for electrochemically controlled SPME of anions or cations and coatings with restricted-access properties for direct extraction from whole blood or immunoaffinity SPME. In-tube SPME uses segments of commercial gas chromatography (GC) capillaries for highly efficient extraction by repeated aspiration–ejection cycles of the liquid sample. It can be easily automated in combination with liquid chromatography but, as it is very sensitive to capillary plugging, it requires completely homogeneous liquid samples. In contrast, fiber-based SPME has not yet been performed automatically in combination with high-performance liquid chromatography. The headspace extractions on fibers or needles (solid-phase dynamic extraction) combined with GC methods are the most advantageous versions of SPME because of very pure extracts and the availability of automatic samplers. Surprisingly, substances with quite high boiling points, such as tricyclic antidepressants or phenothiazines, can be measured by headspace SPME from aqueous samples. The applicability and sensitivity of SPME was essentially extended by in-sample or on-fiber derivatization. The different modes of SPME were applied to analysis of solvents and inhalation narcotics, amphetamines, cocaine and metabolites, cannabinoids, methadone and other opioids, fatty acid ethyl esters as alcohol markers, γ-hydroxybutyric acid, benzodiazepines, various other therapeutic drugs, pesticides, chemical warfare agents, cyanide, sulfide and metal ions. In general, SPME is routinely used in optimized methods for specific analytes. However, it was shown that it also has some capacity for a general screening by direct immersion into urine samples and for pesticides and other semivolatile substance in the headspace mode. [ABSTRACT FROM AUTHOR]

A commercially available piezo-driven drop-on-demand dispenser was tested for its suitability for the preparation of analytical calibration standards and in a standard addition approach prior to quantitative ultra performance liquid chromatography (UPLC) analysis of homoserines. The reproducibility of the drop-on-demand dosing system was tested and the verification of the droplet volume was performed by preparing a series of 1.0 mg/L caffeine standard solutions from a 1,000.0 mg/L stock solution and analysis of the concentrations obtained by UPLC. The reproducibility was better than 1% relative standard deviation from measurement to measurement and the highest was 1.6% from day to day. The results were compared with the conventional way of generating standard solutions (pipetting). A gravimetric method and a photography-based method for the determination of the average single droplet volume were compared and found to be in very good agreement. The system was employed for the quantification of N-decanoyl homoserine by standard addition in bacterial culture supernatants containing this analyte. The agreement with conventional quantification techniques was high. The paper shows the feasibility of the approach with advantages in low sample and solvent volume consumption and very good reproducibility and reliability combined with easy usage. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The present paper describes the use of different solvent mixtures to extract from fish various sulfophenylcarboxylic acids (SPCs of C6 to C13), and their originating compounds, linear alkylbenzene sulfonates (LAS of C10 to C13). The analytical method utilized involves pressurized liquid extraction, followed by preconcentration of the samples, purification by solid-phase extraction, and finally identification and quantification of the target compounds by high-performance liquid chromatography-mass spectrometry using a system equipped with an electrospray interface operating in negative ion mode. The SPCs and LAS were extracted from spiked fish first with hexane to remove interference from fats, then with different mixtures of solvents: dichloromethane followed by methanol; 50:50 dichloromethane-methanol; and 30:70 dichloromethane-methanol. The LAS recoveries obtained with these three extraction options were high (between 68.5 and 80.8%); however, owing to the low percentages obtained for SPC homologues (13.5, 13.1, and 15.9%, respectively), another extraction procedure with methanol was developed in order to increase these recoveries. The percentage of recovery for total SPCs with the methanolic extraction was higher (90.1%), with a standard deviation of 9.9, and the LAS recoveries also increased (99.9%). Detection limits were between 1 and 22 ng g−1 for LAS, and between 1 and 58 ng g−1 for SPCs. Quantitation limits were between 4 and 73 ng g−1 for LAS, and between 2 and 193 ng g−1 for SPCs. This method has been applied to measure the biotransformation of 2ØC10 LAS (where Ø is a sulfophenyl group) in fish exposed in a flow-through system, and enabled the separation and identification of SPCs from 5ØC6 to 9ØC10. [ABSTRACT FROM AUTHOR]

This paper describes an analytical method for the determination of ceruloplasmin (Cp) in human serum. The method uses immunoaffinity chromatography and size-exclusion chromatography (SEC) to “purify” the serum sample prior to analysis of 63Cu and 65Cu by inductively-coupled plasma mass spectrometry (ICPMS). By removing the six most abundant proteins from serum with immunoaffinity chromatography and by using SEC to separate Cu bound by Cp from any free Cu that might be present in the serum sample, we demonstrated that SEC-ICPMS can accurately and reproducibly measure Cp in the ERM DA470 reference serum. Cp identification is based on retention time match of the unknown in the serum sample with the Cp external standard and the presence of 63Cu and 65Cu at a ratio of 2.2±0.1. This method was used to analyze a reference serum certified for Cp, 47 serum samples from four different diseases and a set of normal controls. The reference serum and a serum sample from a patient with myocardial infarction, as well as a Cp standard, were also analyzed by electrospray mass spectrometry to confirm the presence of Cp in the SEC fraction known to contain 63Cu. [ABSTRACT FROM AUTHOR]

This paper demonstrates headspace liquid-phase microextraction (HS-LPME) as used for the determination of volatile residual solvents in pharmaceutical products. This method is based on headspace liquid-phase microextraction capillary column gas chromatography. Under optimum conditions, the linerary of the method ranged from 1 to 1,000 mg l−1. The limits of detection are 0.2–2.0 mg l−1 and relative standard deviations (RSD) for most of the volatile solvents were below 10%. This novel method is applied to the analysis of volatile residual solvents in pharmaceutical products with satisfactory results. [ABSTRACT FROM AUTHOR]

In this paper the most recent developments in the microextraction of polar analytes from aqueous environmental samples are critically reviewed. The particularities of different microextraction approaches, mainly solid-phase microextraction (SPME), stir-bar-sorptive extraction (SBSE), and liquid-phase microextraction (LPME), and their suitability for use in combination with chromatographic or electrically driven separation techniques for determination of polar species are discussed. The compatibility of microextraction techniques, especially SPME, with different derivatisation strategies enabling GC determination of polar analytes and improving their extractability is revised. In addition to the use of derivatisation reactions, the possibility of enhancing the yield of solid-phase microextraction methods for polar analytes by using new coatings and/or larger amounts of sorbent is also considered. Finally, attention is also focussed on describing the versatility of LPME in its different possible formats and its ability to improve selectivity in the extraction of polar analytes with acid-base properties by using separation membranes and buffer solutions, instead of organic solvents, as the acceptor solution. [ABSTRACT FROM AUTHOR]

This paper reports the effect of transfer line (TL) internal diameter (i.d.) on gas chromatographic separation characteristics such as efficiency and speed, when a multicapillary (MC) column is used for speciation analysis of mercury. Five different TL consisting of fused-silica capillaries with 0.15, 0.20, 0.25, 0.32, and 0.53 mm i.d. are compared. The separation efficiency and total chromatographic run time are critically affected by the i.d. of the TL. Narrow capillaries (i.d.≤0.20 mm) produce minimum peak dispersion whereas wide capillaries result in narrow peaks and shorter chromatographic analysis times. A thermodynamic approach is proposed to describe the motion of the analytes through the separation column and TL. The model provides good agreement with the experimental data for high pressures (≥35 psig) and wide TL (≥0.25 mm i.d.). [ABSTRACT FROM AUTHOR]

The semi-experimental approach to approximating physicochemical data relevant to environmental distribution (vapor pressure and gas–octanol distribution) by correlation with gas chromatography (GC) retention data has been extended to the determination of Kow values. We estimated Kow values >104 for polychlorinated biphenyls (PCB), which are often derived by liquid chromatography, by correlation with gas chromatographic retention data. Selecting a set of reference compounds with known Kow values for relative retention time (RRT) correlation enables easy and accurate semi-empirical calculation of further Kow values for a given group of congeners. The RRT/log Kow correlation is validated in this paper with regard to the following gas chromatographic conditions: (1) isothermal versus temperature-programmed elution, (2) the possible effect of the polarity of the stationary phase, and (3) the effect of the format of the standardized GC retention data. The advantages of our Kow(GC) method can be summarized as follows: complex mixtures can be analyzed, only amounts in the nanogram-range or less are required, Kow values of isomers can be determined and the exact structure of compounds need not be known. Normalized GC retention data of persistent organic pollutants are readily available. The quality of the Kow values obtained by the GC method compares well with that for other Kow estimation methods. It depends mainly on the accuracy of the Kow data of the structurally correlated compounds used as standards for the correlation cohort. The Kow(GC) data for all 209 PCB congeners are given. [ABSTRACT FROM AUTHOR]

Polyelectrolyte–surfactant complexes (PSC) of polycarboxylic acids with alkyl-trimethylammonium salts look very promising as a new type of pseudo-stationary phase in micellar electrokinetic chromatography. PSC produce an intramolecular micellar phase, and the morphology of the micelles is significantly different from that of the corresponding “typical” surfactant micelles. Pseudo-stationary phases based on PSC have unique selectivity. In this paper, the effect of the composition ( φ) of the PSC of polyacrylic acid (PAA) MW 130,000 with dodecyltrimethylammonium bromide (DTAB) and of the PSC of PAA MW 450,000 with DTAB on the separation of DNS–amino acids and phenol derivatives in these systems was investigated. Relative retention and relative selectivity were used to describe the electrophoretic behavior of the amino acids and phenol derivatives. The main advantage of PSC pseudo-phases is that the nature and the structure of micelle-like units, and hence the selectivity of electrophoretic separation, could easily be modified by changing the composition of the complex. [ABSTRACT FROM AUTHOR]

A simple and rapid microwave-assisted extraction (MAE) technique has been developed for the determination of water-soluble inorganic species (cations: Na+, NH, K+, Ca2+ and Mg2+ and anions: F-, Cl-, NO, POand SO) in airborne particulate matter. The analytes were extracted under different treatment conditions such as microwave power and extraction time. They were quantified using ion chromatography. The observed concentrations and recovery yields obtained under different conditions were compared. The results of a comparison between this MAE and sonication using NIST SRM 1648 are also given in this paper. The optimized MAE technique gave results in good agreement with the values obtained by the sonication. For some ions, for example Mg2+ and K+, recovery was low with both techniques. The results demonstrated that the optimized MAE is fast and efficient compared with conventional ultrasonic extraction. Urban airborne particles were collected and subjected to the MAE followed by the IC analysis to determine the relative proportions of different water-soluble inorganic species. These results are briefly discussed. [ABSTRACT FROM AUTHOR]

This paper describes a fast, simple and novel extraction method for total selenium and selenium species determination in food samples. Parameters influencing extraction, such as sonication time, extracting media, temperature, sample mass, ultrasound amplitude and sample/enzyme mass ratio were investigated. The enzymatic hydrolysis proposed, enhanced by probe sonication, allowed the quantitative extraction of selenium in chicken muscle, liver, kidney and feed (97, 93, 95 and 102%, respectively) in 2 min, maintaining the original Se-species integrity. Total Se content of the samples was determined using inductively coupled plasma mass spectrometry. Se-species were identified and quantified using high-performance liquid chromatography in conjunction with inductively coupled plasma mass spectrometry. Chromatographic analyses were carried out under two chromatographic conditions and led to the identification of SeMet in all samples. The accuracy of the proposed method was assessed using certified reference materials as well as microwave digestion. Potential advantages of the proposed method over traditional hydrolysis are speed, simplicity and safety of the procedure. [ABSTRACT FROM AUTHOR]

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is a versatile coupling system which combines both selectivity and sensitivity and certainty. Hence, it is generally considered as the most reliable technique to quantify chemical compounds in complex matrices. In the present paper, we evaluate the performance of LC-MS/MS methods for the quantification of 3-nitrotyrosine in human urine in order to point out its dependence on the design of the quantification method, and emphasize the role of matrix effects in the performance. We compare external and internal calibrations, isotope dilution and isotopomer-based exact matching. The role of both sample preparation and multiple transitions monitoring is particularly addressed. [ABSTRACT FROM AUTHOR]

This paper describes the optimisation of a PSS injector in a gas chromatograph with a programmed pneumatic control (PPC) for the determination of 21 organochlorine pesticides. The injection of high volumes of sample (20 µl) improves the detection limits and allows a reduction in the amount of sample processed. The injection conditions were selected by a Plackett-Burman design followed by a central composite design. The LODs obtained in the optimum conditions were compared with those obtained with splitless/ECD. Finally, the method was successfully applied to the analysis of a leachate and vegetable samples. [ABSTRACT FROM AUTHOR]