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An electrokinetically pumped sheath-flow nanoelectrospray interface provides an efficient means of transferring ions from a capillary electrophoresis system into a mass spectrometer. To characterize its performance, we analyzed angiotensin solutions prepared in a background of 0.25 mg/mL of a BSA tryptic digest. Calibration curves were prepared from 10 zeptomole (10(−21) mol) to 10 femtomole (10(−14) mol) of angiotensin injected into the capillary. A parallel reaction monitoring approach was used; MS1 was set to m/z = 523.8 ± 2, and fragment ion signals at 263.1389 (y(2+)) and 784.4095 (b(6+)) were used to generate selected ion electropherograms. Calibration curves based on peak areas were linear (log-log slope of 0.94 for the y(2+) fragment and 0.98 for the b(6+) fragment). We then injected 1-zmol (600 copies) of angiotensin in the BSA background using a 10-μm ID separation capillary. Triplicate analyses consistently produced co-migrating peaks for the two fragment ions. The b(6+) electropherogram showed no background signal, whereas the y(2+) electropherogram showed a few noise spikes that were smaller than the peak maximum. Bienayme-Tchebycheff inequality was used to estimate detection limits of 230 ymol (140 ions) injected into the separation capillary. To the best of our knowledge, these electropherograms present the smallest number of molecules detected using mass spectrometry coupled with a separation.

In this work, the analytical performance of a third-order/four-way calibration is evaluated to model a highly overlapped system, where two spectral dimensions are extremely similar, and the results are then compared with the results of second-order/three-way calibration. The four-way data were obtained during the photodegradation of fluoroquinolones (ciprofloxacin, norfloxacin and flumequine) in the form of excitation-emission matrices and modeled by unfolded partial least squares coupled to residual trilinearization (U-PLS-RTL). According to the results, the model obtained with the second-order algorithm (unfolded partial least squares coupled to residual bilinearization: U-PLS-RBL) was unsatisfactory due to high spectral overlap. The third-order approach obtained a satisfactory fit and better figures of merit (LOD, REP, RMSEP, and sensitivity, among others) even in the presence of unexpected interferences due to third-order advantages. Finally, the analytical method based on third-order multivariate calibration was applied to quantify these fluoroquinolones in spiked fish-farming water samples. In this case, the third-order advantage allowed us to satisfactorily model the data and to quantify these compounds in this complex matrix, demonstrating the superior analytical performance of the high-order data that were evaluated.

Fabricating simple, accurate and user-friendly diagnostic device for “point of care testing” (POCT) applications is one of the most challenging objectives in the analytical field. Hemin detection is important for drugs monitoring, diagnosis, and forensic latent bloodstain imaging. Herein is developed, luminol chemiluminescence biosensor for hemin detection using artesunate as coreactant. A possible mechanism to account for the chemiluminescence reaction is discussed. Hemin was detected using both photomultiplier tube (PMT) and smartphone as detector. The detection limit for hemin using smartphone as detector is 20 nM, enabling the visual detection of hemin in blood sample with a dilution factor of blood up to 120,000. While PMT detector is used, the system is able to detect hemin down to 0.22 nM. In addition to high sensitivity, this sensing system exhibit high selectivity. It can successfully distinguish bloodstain from other stains while applying the system for point of care testing using smart phone as detector. Moreover, the system can detect artesunate with a linear range from 0.1 nM to 1.0 μM with a limit of detection of 0.078 nM.

In this study, we used nano-smectite (SMT) and multiwall carbon nanotube (MWCNT) as a recognition surface over the disposable pencil graphite electrode for the low-level detection of ascorbic acid (AA) and acetyl salicylic acid (ACA). Firstly, nano-semectit was obtained by the purification of natural bentonite clay. XRD patterns and Scanning electron microscopy (SEM) were employed to ensure the purity of the bentonite samples. Pencil graphite rodes were immersed into suspensions of SMT, MWCNT or the both.The surface morphology of the sensor was investigated by cyclic voltammery (CV), electrochemical impedance spectroscopy (EIS) and SEM techniques. The effect of pH, percentage composition of modifiers, immobilization time, accumulation time and accumulation potential was optimized for reaching the best electroanalytical response for AA and ACA. The sensor developed proved to give good recovery, notable electro-catalytic activity and appropriately distant signals for the simultaneous determination of the analytes. Common contaminates, uric acid, l-cysteine, dopamine, glucose, Na+, Cl- and citric acid were investigated for their interference effects. Uric acid, citric acid and dopamine were found to interfere to some extent. The electrode exhibited wide working ranges and a fairly satisfactory detection limit of 0.096 and 0.241 μM for AA and ACA, respectively. The electrode system proved to be practical for the analysis of pharmaceutical tablets and the recovery results are very satisfactory.

Ambient ionization in open environment brings a capability of a coupled mass spectrometry to detect target molecules in situ. However, it is limited to qualitative and semi-quantitative analysis. By coupling of an ambient ionization-based Direct Analysis in Real Time (DART) with high-resolution quadrupole time-of-flight mass spectrometry (QTOF/MS), we observe that, in one-chemical system, the target molecule displays a non-linear response in MS signal vs concentration, accompanying with large variation in MS signal, suggesting two obstacles for quantification to be overcome. Surprisingly, in a two-chemical system, we observe an apparent suppression effect. We prove that, due to this observed suppression effect, a fluctuant response in the MS signal of the stable isotope-labeled analogue can immediately reflect the change in the analyte concentration and ionization efficiency. For example, by taking advantage of this effect, even the analyte of different concentrations despairingly displayed similar signals would be accurately calibrated through the suppression of the internal stable isotope standard. This puts an important foundation on accurate and linear quantitation of analytes in complex matrix using DART-MS assay. Moreover, we for the first time demonstrate an application of in situ calibration of DART-MS for direct and accurate quantification of target molecule (creatinine) in highly complex samples (human urine) without any pre-separation. The quantification is also validated using HPLC-UV analysis (n = 38). At last, we show that stable isotope-labeled-creatinine (m/z 117.0850 amu) can be used for simultaneous in situ calibration of some other urinary metabolites with a mass/charge ratio varying from 120.069 amu to 333.125 amu.

This study describes, for the first time, the development of two platforms of competitive fluorescent immunoassays for bioanalysis of crizotinib (CZT), a potent drug used for the treatment of non-small cell lung cancer (NSCLC). These platforms were microwell-based heterogeneous fluoroimmunoassay (FIA) and a kinetic exclusion assay (KinExA) with KinExA™ 3200 immunosensor. Both FIA and KinExA were developed using same reagents; mouse anti-CZT antibody and a capturing reagent of CZT conjugated with bovine serum albumin (CZT-BSA). In the FIA, the CZT-BSA coated onto the microwells of the assay plate was present simultaneously in the assay mixture (CZT and its antibody). In the KinExA, the antibody was allowed to pre-equilibrate with CZT, and then the incubation mixture was rapidly passed through a microcolumn containing CZT-BSA coated onto polymethyl methacrylate (PMMA) beads. The analytical performances of both assays were comparatively evaluated in terms of assay working range, limit of detection, precision profile, and accuracy. The results revealed that KinExA yielded higher sensitivity and better precision than FIA; whereas, both assays had comparable accuracies. Both FIA and KinExA were superior to all the existing chromatographic methods for CZT in terms of the assay sensitivity, convenience, analysis throughputs. The proposed FIA and KinExA are anticipated to effectively contribute to the therapeutic drug monitoring (TDM) of CZT in clinical settings.

A comparison of the performance of two electrochemical immunosensors for the determination of the anorexigen biomarker peptide YY (PYY) is reported by using as scaffolds screen printed gold electrodes modified either by oxidative grafting of p-aminobenzoic acid (p-ABA) or by assembling of a 4-mercaptobenzoic acid (4-MBA) SAM. Covalent immobilization of capture antibodies on the surface-confined carboxyl groups was carried out by EDC/NHSS chemistry, and competitive immunoassays between target PYY and Biotin-PYY were implemented. Upon labeling with alkaline phosphatase (AP)-streptavidin conjugate and 1-naphtyl phosphate addition, differential pulse voltammograms recorded between −0.2 and +0.7 V were used as analytical readout. All the steps involved in the functionalization of the electrodes and the preparation of the immunosensors were monitored by electrochemical impedance spectroscopy. The calibration plot for PYY using the AP-Strept-Biotin-PYY(PYY)-anti-PYY-Phe-N-SPAuE immunosensor provided a linear current vs. log [PYY] plot extending between 10−6 and 103 ng/mL PYY with a detection limit of 3 × 10−7 ng/mL. These analytical characteristics are remarkably better than those obtained with the immunosensor prepared with 4-MBA SAM-SPAuEs. The AP-Strept-Biotin-PYY(PYY)-anti-PYY-Phe-N-SPAuE immunosensor was used to analyze human serum and saliva samples spiked with PYY at concentrations fitting with normal levels in these biological fluids.

N-acetylcysteine (N-AC) has widespread application such as pharmaceutical drug and nutritional supplement. Its adverse effects are rash, urticaria, and itchiness and large doses of N-AC could potentially cause damage to the heart and lungs. Therefore, in this work, a sensitive voltammetric sensor based on a carbon paste electrode modified with silica nano particles (i.e. Mobil Composition of Matter (No. 41) modified with Boron Trifluoride or BF3@MCM-41) with a combination of 4,4'-dihydroxybiphenyl (DHB) (BF3@MCM-41/DHB/CPE) was designed for determination of N-AC. The electrochemical oxidation of N-AC was examined using various techniques such as cyclic voltammetry (CV), chronoamperometry and differential pulse voltammetry (DPV). Under the optimum conditions, some parameters such as electron transfer coefficient (α) and heterogeneous rate constant (ks) were estimated for N-AC. Due to the use of N-AC for the treatment of acetaminophen (AC) overdose, the application of modified electrode was investigated for the simultaneous determination of N-AC and AC in blood serum and tablet samples. Since, the signals of these species overlap and due to the presence of interfering species in blood samples, the simultaneous determination of mentioned species is difficult or impossible. To overcome this challenge, parallel factor analysis (PARAFAC) was used for the analysis of the complex matrices to obtain the spectral profile of each component and interference. To achieve this goal, electrochemical second-order data were generated using a simple change in pulse height of differential pulse voltammetry. The results of the presently proposed strategy for the real samples analysis are similar to those obtained with HPLC. Thus, the proposed method has acceptable performance for simultaneous determination of the two species in real samples.

This study describes, for the first time, the development of an automated sensitive flow fluorescent noncompetitive immunoassay based on kinetic-exclusion analysis (KinExA) for the quantitative determination of human plasma levels of monoclonal antibodies (mAbs) used for cancer immunotherapy. The assay was adapted on KinExA™ 3200 biosensor and optimized and validated for bevacizumab (BEV) and cetuximab (CET), as representative examples of the mAbs, using their specific antigens. These antigens were the human vascular endothelial growth factor (VEGF) and epidermal growth factor receptor (EGFR) for BEV and CET, respectively. The limits of detection were 1.28 and 52.64 ng mL−1 for BEV and CET, respectively. The accuracy of the assay was demonstrated with analytical recovery of analytes from spiked plasma at 96.2–104.3 and 96.8–105.3% for BEV and CET, respectively. The precision of the assay was satisfactory as shown by relative standard deviation (RSD) at 2.2–5.7 and 2.5–6.1% for assay of BEV and CET, respectively. The high sensitivity of the assay allowed the use of very small volumes (~ 1 µL) of plasma sample for analysis. Automated analysis by the proposed KinExA-based assay facilitates the processing of large numbers of mAbs-containing specimens in studies of pharmacokinetics (PK), pharmacodynamics (PD), and therapeutic drug monitoring (TDM) of therapeutic mAbs. The proposed assay can be used to overcome the problems encountered in the existing conventional immunoassays for mAbs.

This work presents a second-to-none method for Taxol isolation from the Endophytic fungus Cladosporium sphaerospermum (AUMC 6896) and the Entomopathogenic fungus Metarizium anisopliae (AUMC 5130). The extracts were analyzed by high performance liquid chromatography (HPLC) and Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) using positive electrospray ionization (ESI) in the multiple reaction monitoring (MRM) mode. This is rapid, consistent, reproducible, accurate, and sensitive for quantifying Taxol across multiple samples. The yield of crude Taxol product obtained from Potato Dextrose broth (PDB) medium inoculated with Cladosporium sphaerospermu and Metarizium anisopliae was found to be 3.732, and 0.0023 μg L−1 respectively. The yield can be improved by adding ammonium acetate or salicylic acid to the culture broth. Addition of ammonium acetate (AA) (20 mg L−1) to culture media resulted in an increase of Taxol yield to 30.365 and 27.289 μg L−1 respectively. Production of Taxol was 29.844 and 67.254 μg L−1 for the two fungus species when ammonium acetate was substituted by 90 mg L−1 salicylic acid (SA). Adding both AA (20 mg L−1) and SA (90 mg L−1) to the culture media resulted in an increase of the Taxol yield to 4.054 and 116.373 μg L−1 respectively. Our proposed analytical method offers very fast (3 min) quantitation of Taxol in comparison with other published methods. These findings represent a new bioprospecting of the endophytic fungi that may serve as a potential material for the production of Taxol for anticancer treatment.

Ferrous(II) phosphate nanoflowers (Fe3(PO4)2·8H2O NFs) were synthesized by a facial co-precipitation method. The structure, composition and morphology were characterized by XRD, EDX, element mapping and FESEM. The as-prepared Fe3(PO4)2·8H2O NFs exhibited excellent intrinsic peroxidase-like activity. Steady-state kinetic studies showed that Fe3(PO4)2·8H2O NFs exhibited stronger affinities with 3,3,5,5-tetramethylbenzidine (TMB) and H2O2 as the substrates compared with the natural horseradish peroxidase (HRP) and the catalytic constant (kcat) value was even higher than HRP and other reported nanomaterial based peroxidase mimics. The investigation of the catalytic mechanism by cyclic voltammetry, fluorescence spectroscopy and ESR displayed the catalytic activity of Fe3(PO4)2·8H2O NFs originated from the generation of •OH. The Fe3(PO4)2·8H2O NFs also exhibited higher robustness and better storage stability than HRP. Then, a Fe3(PO4)2·8H2O NFs-based colorimetric platform was developed to determine H2O2 and glucose. The linear range of H2O2 and glucose was as broad as 1 × 10−5–2.5 mM and 8 × 10−4–1.2 mM, and the detection limit (LOD) was as low as 5 nM and 35 nM, respectively. This simple assay offered a highly sensitive and specific strategy for H2O2 and glucose determination, which had been successfully utilized for real sample analysis with good reproducibility and accuracy.

A simple and economical spectrofluorimetric alternative for aluminium determination in bivalve mollusks based on the fluorescent blue-green colour complex between Al(III) and salicylaldehyde picolinoylhydrazone (SAPH) has been studied. The factors that are most likely to affect were optimized with a Box-Behnken design. Optimum conditions were: pH 6.6, 0.9 mol L-1 acetic acid/acetate buffer, 3.0 mmol L-1 SAPH, and 50% ethanol. Detection and quantitation limits were found to be 2.7 μg L-1 and 9.1 μg L-1, respectively. The upper limit of application was assessed through the limit of linearity which was set as 300 μg L-1. Intra-day repeatability and inter-day repeatability were evaluated showing an excellent precision for the fluorescence method (both < 5%). The method was sensitive enough for the satisfactory determination of aluminium in several bivalve mollusk samples both fresh and canned seafood. The results showed that commercial fresh wild products presented the smallest Al concentration (6-27 mg per 100 g dry weight), while bivalves preserved in cans the concentration was considerably higher (75 mg per 100 g dry weight). Thus, differences between Al concentration related to processing were identified. The study shows a simple, cost-effective and reliable tool for routine aluminium determination in seafood for food quality control.

The aim of the present work was to develop a rapid and interference-free method based on liquid chromatography-mass spectrometry (LC-MS) for the simultaneous determination of nine B-group vitamins in various energy drinks. A smart and green strategy that modeled the three-way data array of LC-MS with second-order calibration methods based on alternating trilinear decomposition (ATLD) and alternating penalty trilinear decomposition (APTLD) algorithms was developed. By virtue of "mathematical separation" and "second-order advantage", the proposed strategy successfully solved the co-eluted peaks and unknown interferents in LC-MS analysis with the elution time less than 4.5min and simple sample preparation. Satisfactory quantitative results were obtained by the ATLD-LC-MS and APTLD-LC-MS methods for the spiked recovery assays, with the average spiked recoveries ranging from 87.2-113.9% to 92.0-111.7%, respectively. These results acquired from the proposed methods were confirmed by the LC-MS/MS method, which shows a quite good consistency with each other. All these results demonstrated that the developed chemometrics-assisted LC-MS strategy had advantages of being rapid, green, accurate and low-cost, and it could be an attractive alternative for the determination of multiple vitamins in complex food matrices, which required no laborious sample preparation, tedious condition optimization or more sophisticated instrumentations.

A simple, rapid, and ultrasensitive fluorescence strategy for adenosine triphosphate (ATP) detection was developed by using a FAM (carboxyfluorescein) labeled DNA (FAM-DNA). In this strategy, highly fluorescent FAM-DNA was used as a probe, and nanoceria (CeO2 NPs) acted as an efficient quencher. FAM-DNA attached to the surface of nanoceria through the coordination between the phosphate group of DNA and NP surface, which induced complete quenching in the FAM-DNA fluorescence due to a photo induced electron transfer (PET) process. It was found that ATP can readily displace adsorbed DNA from nanoceria surface because of the stronger coordination ability of ATP with nanoceria, and the nanoceria-based competitive binding resulted in over 7-fold fluorescence enhancement. Over a wide range from 0.1nM to 1.5μM, a good linear relationship between the fluorescence intensity and the concentration of ATP was obtained and the detection limit was estimated to be as low as 54pM. This method was successfully used to analyze ATP in a single drop of blood and human urine.

In this work, polypropylene hollow fiber was replaced by agarose gel in conventional electro membrane extraction (EME) to develop a novel approach. The proposed EME method was then employed to extract two amino acids (tyrosine and phenylalanine) as model polar analytes, followed by HPLC-UV. The method showed acceptable results under optimized conditions. This green methodology outperformed conventional EME, and required neither organic solvents nor carriers. The effective parameters such as the pH values of the acceptor and the donor solutions, the thickness and pH of the gel, the extraction voltage, the stirring rate, and the extraction time were optimized. Under the optimized conditions (acceptor solution pH: 1.5; donor solution pH: 2.5; agarose gel thickness: 7 mm; agarose gel pH: 1.5; stirring rate of the sample solution: 1000 rpm; extraction potential: 40 V; and extraction time: 15 min), the limits of detection and quantification were 7.5 ng mL−1 and 25 ng mL−1, respectively. The extraction recoveries were between 56.6% and 85.0%, and the calibration curves were linear with correlation coefficients above 0.996 over a concentration range of 25.0–1000.0 ng mL−1 for both amino acids. The intra- and inter-day precisions were in the range of 5.5–12.5%, and relative errors were smaller than 12.0%. Finally, the optimized method was successfully applied to preconcentrate, clean up, and quantify amino acids in watermelon and grapefruit juices as well as a plasma sample, and acceptable relative recoveries in the range of 53.9–84.0% were obtained.

In this paper, a procedure for in-situ pre-concentration in graphite furnace by repeated sampling and pyrolysis is proposed for the determination of ultra-trace thallium in drinking water by graphite furnace atomic absorption spectrometry (GF-AAS). Without any other laborious enrichment processes that routinely result in analyte loss and contamination, thallium was directly concentrated in the graphite furnace automatically and subsequently subject to analysis. The effects of several key factors, such as the temperature for pyrolysis and atomization, the chemical modifier, and the repeated sampling times were investigated. Under the optimized conditions, a limit of detection of 0.01 µg L−1 was obtained, which fulfilled thallium determination in drinking water by GB 5749-2006 regulated by China. Successful analysis of thallium in certified water samples and drinking water samples was demonstrated, with analytical results in good agreement with the certified values and those by inductively coupled plasma mass spectrometry (ICP-MS), respectively. Routine spike-recovery tests with randomly selected drinking water samples showed satisfactory results of 80–96%. The proposed method is simple and sensitive for screening of ultra-trace thallium in drinking water samples.

We describe the preparation and validation of a novel lateral flow immunoassay test for the detection of human heart fatty acid binding protein (hFABP). Water-soluble CdTe quantum dots (QDs) were selected as the fluorescent label and were linked covalently to anti-hFABP antibodies. Upon conjugation, the secondary structure of the anti-hFABP was preserved and the fluorescence quantum yield of the CdTe QDs increased. The labelled antibodies were transferred to the immunoassay test strip and the antigen-antibody reaction was successfully performed. This evidenced the preserved antibody activity of QD-labelled anti-hFABP towards hFABP, and provided a rapid means for the quantitation of hFABP in human serum within the range of 0-160ng ∙ ml-1, with a much lower detection limit of 221pg.∙ ml-1 compared with other rapid tests based on lateral flow immunoassays. This new immunoassay test has been successfully used for the early detection of acute myocardial infarction.

A simple and efficient multi residue method was developed, for the analysis of 160 pesticides by GC-MS/MS in herbal plants. The developed method employs pesticide residue extraction by EtAC/ n. hexane (6:4) with a cleanup step using florisil/ PSA mixture. The optimized conditions have resulted in lower co-extracted matrix components than those extracted using EtAC or MeCN (QuEChERS method), according to FTIR and full scan GC/MS analyses. In addition, the developed method (EtAC/ Hexane) eliminates the evaporation step that is usually performed when using MeCN as an extraction solvent prior to the GC-MS/MS injection. The developed method was fully validated on chamomile, based on SANTE/11945/2015 guidelines. Where, intraday recoveries were estimated at three concentration levels of 10, 50 and 250 μg kg −1 . However, interday recoveries have also been carried out, at 250 μg kg −1 . In addition, intraday recoveries were estimated for two other herbal plants (thyme and marjoram), at 250 μg kg −1 . Three point calibration mixtures were prepared in ethyl acetate solvent and in the blank extracts of chamomile, thyme, and marjoram, in order to check the linearity and matrix effect. The average recoveries for most of the studied pesticides ranged from 70% to 100% at 50 and 250 μg kg −1 with relative standard deviations below 20%. The validated method was successfully applied for determination of pesticide residues in 20 herb samples, collected from the Egyptian market.

Superoxide anion (O2•-), one of the most active reactive oxygen species (ROS) in micro-environment of the human body, is involved in some diseases if there is excess O2•- associated with oxidative stress. Accurate detection of its concentration has important medical diagnostic significance. In this work, a new electrochemical sensor was designed and fabricated for sensitive detection based on Mn-superoxide dismutase (MnSOD) that decorated onto the surface of magnetic polymeric nanotubes by surface self-assembly processes. The composite nanotubes were characterized by transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), Zeta potential analyzer, energy dispersive spectroscopy (EDS) and vibrating sample magnetometer(VSM), and the biosensor exhibited excellent analytical performance, for example, the interference could be eliminated with high selectivity, the linear range from 0.15 to 3.0μM with a detection limit of 0.0136μM (S/N=3)，Cyclic voltammogram (CV) curves of the biosensor for 30 overlapping cycles showed the biosensor had a good cycle stability. Results indicated that the magnetic polymeric nanotubes that decorated by Mn3(PO4)2 nanoparticles could effectively catalyze the dismutation of O2•- that attributed to its high surface areas and a large number of active sites of self-assembled Mn3(PO4)2 nanoparticles. This method combining nanotechnology and self-assembly technique provided a new appropriate platform to design and fabricate electrochemical sensor with high performance.

We designed two double quenching molecular beacons (MBs) with simple structure based on guanine (G base) and Black Hole Quencher (BHQ), and developed a new analytical method for sensitive simultaneous detection of two DNAs by synchronous fluorescence analysis. In this analytical method, carboxyl fluorescein (FAM) and tetramethyl-6-carboxyrhodamine (TAMRA) were respectively selected as fluorophore of two MBs, Black Hole Quencher 1 (BHQ-1) and Black Hole Quencher 2 (BHQ-2) were respectively selected as organic quencher, and three continuous nucleotides with G base were connected to organic quencher (BHQ-1 and BHQ-2). In the presence of target DNAs, the two MBs hybridize with the corresponding target DNAs, the fluorophores are separated from organic quenchers and G bases, leading to recovery of fluorescence of FAM and TAMRA. Under a certain conditions, the fluorescence intensities of FAM and TAMRA all exhibited good linear dependence on their concentration of target DNAs (T1 and T2) in the range from 4 × 10-10 to 4 × 10-8molL-1 (M). The detection limit (3σ, n = 13) of T1 was 3 × 10-10M and that of T2 was 2×10-10M, respectively. Compared with the existing analysis methods for multiplex DNA with MBs, this proposed method based on double quenching MBs is not only low fluorescence background, short analytical time and low detection cost, but also easy synthesis and good stability of MB probes.

Electrochemical properties of eugenol were investigated on a graphene modified carbon paste electrode (CPE) by using voltammetric methods, which exhibited a well-defined irreversible peak at about 0.7V vs Ag/AgCl, NaCl (3M) in Britton-Robinson buffer at pH 2.0. Mechanism of the electrochemical reaction of eugenol was studied by performing density functional theory (DFT) computations and mass spectroscopic analysis. (CPCM:water)-wB97XD/aug-cc-PVTZ//(CPCM:water)-wB97XD/6-31G(d) level calculations predicted that the formation of product P2, possessing a para-quinoid structure, is preferred rather than the product P1, suggested in the literature, having an ortho-quinoid system. Determination of eugenol in a pharmaceutical sample was realized in the light of the electrochemical findings, and a validated voltammetric method for quantitative analysis of eugenol in a pharmaceutical formulation was proposed. The differential pulse voltammogram (DPV) peak currents were found to be linear in the concentration range of 1.0 × 10-7 to 1.7 × 10-5M. The limit of detection (LOD) and the limit of quantification (LOQ) were obtained to be 7.0 × 10-9 and 2.3 × 10-8, respectively.

In the current study, poly(MImEO8BS)-Ni nanocomposite was synthesized and applied to modify a glassy carbon electrode along with conductive polymeric ionic liquids. The electrochemical investigation of the modified electrode as well as its efficiency for voltammetric oxidation of warfarin is elucidated. The electrode was used to study the voltammetric oxidation of warfarin by employing cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry, and square wave voltammetry (SWV) as diagnostic techniques. It has been observed that warfarin oxidation at the surface of modified electrode occurs at a potential of about 230mV which is less positive than that of an unmodified glassy carbon electrode. SWV demonstrated a linear dynamic range from 1.0×10-6 to 1.0×10-4M and a detection limit of 1.5×10-7M for warfarin. In addition, this modified electrode was utilized for simultaneous determination of warfarin and tramadol. Finally, the modified electrode was employed for determination of warfarin and tramadol in pharmaceutical compounds.

Nowadays, a deep eutectic solvent (DES) has recently been considered as a green ion liquid analogue. In this study, a new compound of DES has been synthesized as an extraction solvent in air assistedemulsification liquid-liquid microextraction method (DES-AAELLME) for preconcentration and extraction of methadone followed by gas chromatographyflame ionization detector (GC-FID). To obtain an efficient water-miscible deep eutectic solvent, choline chloride (ch-cl) and 5,6,7,8-Tetrahydro-5,5,8,8-tetramethylnaphthalen-2-ol (TNO) were mixed at a molar ratio of 1:2 and tetrahydrofuran (THF) was used as a demulsifier solvent into homogeneous solution for providing a turbid state. The solution was rapidly sucked up and injected 10 times using a 10-mL glass syringe to enhance the turbidity of solution and disperse the aggregated DES droplets into aqueous phase. Some important parameters affecting extraction recovery were investigated. Under optimum conditions, the calibration curve was linear in the concentration range from 2 to 8000µgL-1. The limit of detection and the limit of quantification were found 0.7µgL-1 and 2.3µgL-1 respectively with preconcentration factor of 270. The precision, as the relative standard deviation (RSD) (n=6), was

The present paper reported an one-pot synthesis of Co nanoparticles doped amino-graphene nanocomposites (Co-amino-Gr), involving in situ generation of Co nanoparticles (NPs). The simultaneous reduction of graphene oxide (GO) and Co2+ to produce Co-amino-Gr had been achieved under mild reaction conditions using an environmentally benign reducing agent, glycine. By combining the merits of amino-Gr and the Co NPs, a highly sensitive electrochemical sensor was erected to detect baicalin based on the Co-amino-Gr nanocomposites. Under optimum conditions, the response peak currents were linear related with baicalin concentrations in the range of 1.0×10-8-8.0×10-7molL-1 with a lower detection limit of 5.0×10-9molL-1 (S/N=3). Additionally, the proposed method was used to detect baicalin in the medicinal capsules with satisfactory results.

The avian influenza A H7N9 virus is known as one of the newly discovered highly pathogenic avian influenzas with serious threat to public health and the poultry industry. In this work, an ultrasensitive surface-enhanced Raman scattering (SERS) determination of H7N9 virus via exonuclease III-assisted cycling amplification was proposed to meet the needs of rapid, sensitive and accurate detection of H7N9-related genes. The SERS strategy aims to simultaneously determine the characteristic gene fragments of H7 and N9 by specially designing Capture, Replace, and Probe single-strand DNAs to realize exonuclease III-assisted cycling amplifications, and then integrating the cyclic amplification with SERS-active Ag nanorods array substrate to achieve an ultrasensitive SERS determination of H7N9. After characterizing the effectiveness of the sensing mechanism and further investigating the surface blocking and the dosage of exonuclease III, the optimal surface blocking was achieved by using 10 μM and 100 μM mercaptohexanol for H7 and N9 detection respectively, and the optimal Exo III concentrations for sensing H7 and N9 were 0.10 U μL−1 and 0.30 U μL−1 respectively. Under the optimal conditions, dual and specific detections of H7 and N9 gene fragments were obtained with detection linear interval from 1 fM to 100 pM and limit of detections low to 31 aM of H7 and 44 aM of N9, as well as recovery in the range of 93.8–106.2% with relative standard deviation less than 6.12%. The proposed ultrasensitive SERS strategy can provide a powerful tool for determining H7N9 virus and other avian influenza viruses.

A fast and simple analytical method was developed to fully understand the chemical diversity of pentacyclic triterpenes: lupane, oleanane and ursane type, using multiple neutral loss markers scanning combined with substructure recognition (MNLSR). This procedure was performed on ultra-high performance liquid chromatography coupled to electrospray ionization quadrupole Orbitrap high resolution mass spectrometry (UHPLC/ESI Q-Orbitrap). Hippophae rhamnoides was used as an example. This approach includes three systematic workflows: (i) targeted identification of 25 reference standards in order to deduce the mechanism of fragmentation in both positive and negative modes. (ii) statistical analysis for neutral loss markers and structural fragment markers of pentacyclic triterpenes by fragmentation mechanism information. (iii) untargeted identification using multiple neutral loss markers scanning technique to discover new compounds and then confirming structural characterization by structural fragment markers. This mass spectra data analysis approach was successful to identify and confirm 15 new compounds from Hippophae rhamnoides samples. This study extended the application of mass spectrometry to satisfy the requirements of high-throughput identification for pentacyclic triterpenes in new medicine or food resources and could help chemists rapidly discover novel similar substructure compounds from a complex matrix.

2-(2H-Benzotriazol-2-yl)-4,6-di-tert-pentylphenol (UV 328; CAS: 25973-55-1) is a benzotriazole ultraviolet light (BUV) absorber which is applied to plastics and other organic substances to prevent discoloration and enhance product stability. Therefore, UV 328 is frequently used as a plastic additive and may lead to an exposure of consumers. For a reliable assessment of UV 328 metabolism, an analytical method applying dispersive liquid-liquid microextraction (DLLME) followed by gas chromatography tandem mass spectrometry and advanced electron ionization was developed which allows the determination of UV 328 and six of its metabolites in human whole blood. Sample preparation was optimized with respect to DLLME parameters. A critical aspect of the procedure was the application of spiked human blood for calibration, which proved to be essential for achieving accurate results. Validation of the method resulted in limits of detection of 0.1 μg/L for all analytes. Variation coefficients ranged from 2 to 9% for intraday precision and from 3 to 11% for interday precision. Furthermore, relative recovery rates between 80 and 100% were calculated. Afterwards, the procedure was successfully applied to blood samples collected from a volunteer orally exposed to a single dose of UV 328. The method proved to be highly sensitive, repeatable and robust for all compounds and may further be used for studies to elucidate the human metabolism and kinetics of UV 328 and for biomonitoring of specific, environmental and occupational exposure to this UV stabilizer.

A simple and rapid HPLC method using 2-chloro-1-methyllepidinium tetrafluoroborate (CMLT) as a derivatization reagent was developed for simultaneous determination of homocysteine (Hcy), glutathione (GSH), γ-glutamylcysteine (γ-GluCys), cysteinylglycine (CysGly), N-acetylcysteine (NACys) and cysteine (Cys) in human saliva, plasma and urine. Separation of the analytes was achieved in just 7min using an HPLC, followed by UV detection at 355nm. Chromatographic separation was accomplished on Aeris PEPTIDE XB-C18 (150mm×4.6mm, 3.6µm) column from Phenomenex with a gradient elution: 0-4.0min, 7-30% B; 4.0-5.5min, 30-7% B; 5.5-7.5min, 7% B; (A: B, v/v); (A) 0.5% CH3COOH and (B) EtOH. Mobile phase was delivered at a flow rate 1.0mLmin(-1). Linearity in detector response for total thiols was observed over the range of 0.1-20μmolL(-1) for Hcy, GSH and γ-GluCys, 0.25-50μmolL(-1) for NACys and CysGly and 5-300 for Cys. The LOQ values for Hcy, GSH, γ-GluCys, NACys, CysGly and Cys were 0.05, 0.05, 0.10, 0.06, 0.12 and 0.08μmolL(-1), respectively. The method was successfully implemented to analysis of the samples donated by 15 apparently healthy volunteers and 10 patients.

A novel multi-wavelength nonaqueous capillary electrophoresis (MW-NACE) technique based on wavelength-dependent laser-induced fluorescence (LIF) detection was investigated for the simultaneous screening of various synthetic organic dyes. Multi-wavelength excitation light sources were utilized to excite different organic dyes [e.g., 543 nm for crystal violet (CV), methyl violet B (MVB), methyl violet B base (MBB), rhodamine 6G (R6G), and rhodamine B base (RBB); 635 nm for nile blue A (NBA) and methylene blue (MB)] simultaneously. Using a nonaqueous buffer system composed of 15 mM sodium borate and 835 mM acetic acid in 100% ethanol (pH=5.4), all dyes were analyzed within 15 min with excellent resolution (R≥4.0) under an electric field of 500 V/cm. Calibration curves showed excellent linearity with square of correlation coefficients (r(2)) greater than 0.9908 over wide dynamic ranges of 0.4-50 μM for CV, 0.8-50 μM for MVB, 1.5-50 μM for MBB, 0.08-5 nM for R6G, 0.06-10 μM for MB, 0.02-10 μM for NBA, and 0.13-10 pM for RBB. The detection limits (S/N=3) of 40 fM to 0.5 μM were 10-200,000 times lower than those of previous detection methods. While adjacent peaks were not well distinguished with baseline separation in a single capillary, the devised technique was faster and more sensitive than conventional aqueous and nonaqueous CE approaches, thereby enabling the quantitative analysis of various dyes based on wavelength-dependent fluorescence detection with different excitation wavelengths.

A novel voltammetric sensor was constructed by simple dripping single-walled carbon nanotubes (SWCNTs) on to the glass carbon electrode (GCE) firstly and electro-polymerizing L-Citrulline film subsequently. The resulting poly(L-Citrulline)/SWCNTs/GCE showed a significant voltammetric response to picroside II due to the synergistic effect of SWCNTs and poly(L-Citrulline) film. The first electroanalytical method of picroside II was proposed with detection linear range from 8.0 × 10(-8) to 5.0 × 10(-6) mol L(-1) and a detection limit of 3 × 10(-8) mol L(-1). The high sensitivity, selectivity and long-term stability made the sensor suitable for the determination of picroside II. Moreover, based on the systematically investigation and some kinetics parameters calculated in the experimentation, the reaction mechanism of picroside II at the poly(L-Citrulline)/SWCNTs modified GCE was obtained reliably. Lastly, the proposed sensor was used for the determination of picroside II in real sample with satisfactory results. This work promoted the potential applications of amino acid materials and SWCNTs in electro-chemical sensors.

The effect of the molecular weight of polyethyleneimine (PEI), defined as a compound having two or more ethyleneamine units, and of its carboxymethylation rate (CM/N), represented by the ratio of ion-exchange capacity to the amount of N on the resin, on the selective solid-phase extraction ability of the chelating resin immobilizing carboxymethylated (CM) PEI was investigated. The chelating resins (24 types) were prepared by immobilization of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, PEI300 (MW=ca. 300), and PEI600 (MW=ca. 600) on methacrylate resins, followed by carboxymethylation with various amounts of sodium monochloroacetate. When resins with approximately the same CM/N ratio (0.242-0.271) were used, the recovery of Cd, Co, Cu, Fe, Ni, Pb, Ti, Zn, and alkaline earth elements increased with increasing the molecular weight of PEIs under acidic and weakly acidic conditions; however, the extraction behavior of Mo and V was only slightly affected. This was probably due to the increase in N content of the resin, resulting in an increase in carboxylic acid groups; the difference in the molecular weight of PEIs immobilized on the resin exerts an insignificant influence on the selective extraction ability. The CM/N ratio considerably affected the extraction behavior for various elements. Under acidic and neutral conditions, the recovery of Cd, Co, Cu, Fe, Ni, Pb, Ti, and Zn increased with increasing CM/N values. However, under these conditions, the recovery of alkaline earth elements was considerably low when a resin with low CM/N ratio was used. This is presumably attributed to the different stability constants of the complexes of these elements with aminocarboxylic acids and amines, and to the electrostatic repulsion between the elements and the protonated amino groups in the CM-PEI. The recovery of Mo and V decreased or varied with increasing CM/N values, suggesting that the extraction of these elements occurred mainly by the anion-exchange reaction. For the separation and preconcentration of trace elements in samples containing large amounts of alkali and alkaline earth elements, the CM-PEI600 resin with CM/N=0.131 (Cu(II) extraction capacity, 0.37mmol g(-)(1)) was found to be the most suitable because it scarcely extracts alkali and alkaline earth elements under acidic and neutral conditions. This resin proved to be convenient for separating and preconcentrating Cd, Co, Cu, Fe, Mn, Mo, Ni, Pb, V, and Zn in the certified reference materials (EnviroMAT EU-L-1 wastewater and ES-L-1 ground water) and commercially available table salt.

Nitrate ions is a very common contaminant in drinking water and has a significant impact on the environment, necessitating routine monitoring. Due to its chemical and physical properties, it is hard to directly detect nitrate ions with high sensitivity in a simple and inexpensive manner. Herein with amino group modified graphene oxide (GO) as a sensing element, we show a direct and ultra-sensitive method to detect nitrate ions, at a lowest detected concentration of 5 nM in river water samples, much lower than the reported methods based on absorption spectroscopy. Furthermore, unlike the reported strategies based on absorption spectroscopy wherein the nitrate concentration is determined by monitoring an increase in aggregation of gold nanoparticles (GNPs), our method evaluates the concentration of nitrate ions based on reduction in aggregation of GNPs for monitoring in real samples. To improve sensitivity, several optimizations were performed, including the assessment of the amount of modified GO required, concentration of GNPs and incubation time. The detection methodology was characterized by zeta potential, TEM and SEM. Our results indicate that an enrichment of modified GO with nitrate ions contributed to excellent sensitivity and the entire detection procedure could be completed within 75 min with only 20 μl of sample. This simple and rapid methodology was applied to monitor nitrate ions in real samples with excellent sensitivity and minimum pretreatment. The proposed approach paves the way for a novel means to detect anions in real samples and highlights the potential of GO based detection strategy for water quality monitoring.

Given the threat that ostreid herpesvirus 1 (OsHV-1) poses to shellfish aquaculture, the need for rapid, user-friendly and cost-effective methods to detect this marine pathogen and minimise its impact is evident. In this work, an electrochemical biosensor for the detection of OsHV-1 based on isothermal recombinase polymerase amplification (RPA) was developed. The system was first tested and optimised on maleimide microtitre plates as a proof-of-concept, before being implemented on miniaturised gold electrodes. Amperometric detection of the isothermally amplified product was achieved through a sandwich hybridisation assay with an immobilised thiolated capture probe and a horseradish peroxidase (HRP)-labelled reporter probe. Calibration curves were constructed using PCR-amplified OsHV-1 DNA, achieving a limit of detection of 207 OsHV-1 target copies. The biosensor was applied to the analysis of 16 oyster samples from an infectivity experiment, and results were compared with those obtained by qPCR analysis, showing a strong degree of correlation (r = 0.988). The simplicity, rapidity, cost-effectiveness and potential for in-situ testing with the developed biosensor provide a valuable tool for the detection of OsHV-1 in aquaculture facilities, improving their management. info:eu-repo/semantics/acceptedVersion

The development of a simple and economical spectrophotometric system based on the use of a device created by 3D printing and the electronics necessary to control the intensity of the radiation source was described. The measurements are made with a low-cost digital webcam. The entire system is only powered through the USB outputs of a computer, which makes the portable and really practical system for the measurements in the field. This method was applied to determine iron (II) in waters using o-phenanthroline as chromogenic reagent giving a red complex, and also to hypochlorite determination using tetramethylbenzidine as the reagent providing a yellow color. The calibration curves were built using a mathematical algorithm making a RGB deconvolution. The intense of colors obtained from a webcam in each concentration of analyte had a relationship with the absorbance values. In order to confirm the accuracy and precision of this method, a traditional spectrophotometer was used for validation.

Endogenous metabolites of amino acids and their derivatives in biosamples are frequently highlighted as the most differential metabolites in recent metabolomics studies. The method for the detection of amino acid derivatives such as N-acetyl amino acids and oligopeptides is rarely reported. We developed a rapid, high-throughput, sensitive and reliable quantitative method to simultaneously profile 40 underivatized amino acids and their derivatives including N-acetyl amino acids and oligopeptides in cell lines, based on ultra-high-performance liquid chromatography-electrospray tandem mass spectrometry (UHPLC- MS/MS) by using a hydrophilic interaction liquid chromatography (HILIC) column. The optimized method was successfully validated with satisfactory linearity, sensitivity, accuracy, precision, matrix effects, recovery and stability for all analytes. Only one compound (cysteine-glutathione disulfide) showed relatively low recoveries at three concentration levels (60.8–74.3%). The limit of quantification (LOQ) for most compounds was in the range of 0.6–10 ng/mL (6–100 pg on column). This method was successfully applied to the analysis of amino acids and their derivatives in breast cancer cell samples. Principal component analysis (PCA) and the orthogonal projections to latent structures (OPLS) showed a clear discrimination of the non-tumorigenic breast epithelial cell line MCF-10A from the breast cancer cell line HCC 1806. Characteristic metabolic changes in amino acid metabolism were observed in the breast cancer cell line. This quantified analytical method of 40 endogenous amino acids and their derivatives in cell lines meets the requirement of quantification in specific expanded metabolomics studies with good sensitivity.

PCR enables sensitive and specific detection of infectious disease agents, but application in point-of-care diagnostic testing remains scarce. A compact tool that runs PCR assays in less than a few minutes and that relies on mass-producible, disposable reactors could revolutionize while-you-wait molecular testing. We here exploit well-established semiconductor manufacturing processes to produce silicon ultra-fast quantitative PCR (UF-qPCR) chips that can run PCR protocols with limited assay optimization. A total of 110 clinical samples were analyzed for the detection of group B streptococci using both a validated benchtop and an on-chip qPCR assay. For the on-chip assay, the total reaction time was reduced after optimization to less than 5 min. The standard curve, spanning a concentration range of 5 log units, yielded a PCR efficiency of 94%. The sensitivity obtained was 96% (96/100; CI: 90-98%) and the specificity 70% (7/10; CI: 40-90%). We show that if melting analyses would be integrated, the obtained sensitivity would drop slightly to 93% (CI: 86-96%), while the specificity would increase to 100% (CI: 72% - 100%). In comparison to the benchtop reference qPCR assay performed on a LightCycler©96, the on-chip assay demonstrated a highly significant qualitative (Spearman's rank correlation) and quantitative (linear regression) correlation. Using a mass-producible qPCR chip and limited assay optimization, we were able to develop a validated qPCR protocol that can be carried out in less than five minutes. The analytical performance of the microchip-based UF-qPCR system was shown to match that of a benchtop assay. This is the first report to provide UF-qPCR validation using clinical samples. We demonstrate that qPCR-based while-you-wait testing is feasible without jeopardizing assay performance. ispartof: TALANTA vol:192 pages:220-225 ispartof: location:Netherlands status: published