Check out our New Publishers' Select for Free Articles

Analytical and Bioanalytical Chemistry (v.405, #14)

Yolanda Picó (Ed.): Chemical analysis of food. Techniques and applications by Rudolf Krska (pp. 4665-4666).

SEC ICP MS and CZE ICP MS investigation of medium and high molecular weight complexes formed by cadmium ions with phytochelatins by Agata Miszczak; Magdalena Rosłon; Grzegorz Zbroja; Katarzyna Brama; Elżbieta Szalacha; Helena Gawrońska; Katarzyna Pawlak (pp. 4667-4678).

Size-exclusion chromatography (SEC) and capillary zone electrophoresis (CZE) coupled with inductively coupled plasma mass spectrometry were applied to characterize low, medium, and high molecular weight cadmium complexes with glutathione and phytochelatins (PCs). The dominant stoichiometry of the complexes formed in vitro was established as 1:1 using electrospray ionization mass spectrometry. Calculated molecular masses of Cd₁L₁ complexes were used for calibration of the SEC and CZE methods. The results showed a lower (2 kDa) SEC column exclusion limit for cadmium complexes compared with free peptides (10 kDa), and most of the high molecular weight cadmium species were eluted in the void volume of the column. Moreover, the CZE method based on the semiempirical model of Offord to elucidate peptide migration allowed us to show a high propensity of Cd–PC complexes for polymorphism on complexation, which was also observed for extracts of Arabidopsis thaliana treated with cadmium. All the information presented is vital for understanding the mechanism of metal deactivation in plants. Figure Estimation of molecular mass of Cd-thiopeptide complexes by size electrophoretic mobility

Keywords: Phytochelatins; Cadmium complexes; Capillary zone electrophoresis–inductively coupled plasma mass spectrometry; Size-exclusion chromatography–inductively coupled plasma mass spectrometry; Electrospray ionization mass spectrometry

Impact of enzymatic and alkaline hydrolysis on CBD concentration in urine by Mateus M. Bergamaschi; Allan Barnes; Regina H. C. Queiroz; Yasmin L. Hurd; Marilyn A. Huestis (pp. 4679-4689).

A sensitive and specific analytical method for cannabidiol (CBD) in urine was needed to define urinary CBD pharmacokinetics after controlled CBD administration, and to confirm compliance with CBD medications including Sativex—a cannabis plant extract containing 1:1 ∆⁹-tetrahydrocannabinol (THC) and CBD. Non-psychoactive CBD has a wide range of therapeutic applications and may also influence psychotropic smoked cannabis effects. Few methods exist for the quantification of CBD excretion in urine, and no data are available for phase II metabolism of CBD to CBD-glucuronide or CBD-sulfate. We optimized the hydrolysis of CBD-glucuronide and/or -sulfate, and developed and validated a GC-MS method for urinary CBD quantification. Solid-phase extraction isolated and concentrated analytes prior to GC-MS. Method validation included overnight hydrolysis (16 h) at 37 °C with 2,500 units β-glucuronidase from Red Abalone. Calibration curves were fit by linear least squares regression with 1/x ² weighting with linear ranges (r ² > 0.990) of 2.5–100 ng/mL for non-hydrolyzed CBD and 2.5–500 ng/mL for enzyme-hydrolyzed CBD. Bias was 88.7–105.3 %, imprecision 1.4–6.4 % CV and extraction efficiency 82.5–92.7 % (no hydrolysis) and 34.3–47.0 % (enzyme hydrolysis). Enzyme-hydrolyzed urine specimens exhibited more than a 250-fold CBD concentration increase compared to alkaline and non-hydrolyzed specimens. This method can be applied for urinary CBD quantification and further pharmacokinetics characterization following controlled CBD administration.

Keywords: Cannabidiol; Cannabidiol-glucuronide; Enzymatic hydrolysis; Urine; GC-MS

LC/ESI-MS/MS method for quantification of 28 synthetic cannabinoids in neat oral fluid and its application to preliminary studies on their detection windows by Stefan Kneisel; Michael Speck; Bjoern Moosmann; Todd M. Corneillie; Nathaniel G. Butlin; Volker Auwärter (pp. 4691-4706).

Serum and urine samples are commonly used for the analysis of synthetic cannabinoids in biofluids; however, their utilization as analytical matrices for drug abstinence control features some substantial drawbacks. While for blood collection invasive sampling is inevitable, the urinary analysis of synthetic cannabinoids is limited by the lack of available reference standards of the respective major metabolites. Moreover, the long detectability of synthetic cannabinoids in both matrices hampers the identification of a recent synthetic cannabinoid use. This article describes the development, validation and application of an LC/ESI-MS/MS method for the quantification of 28 synthetic cannabinoids in neat oral fluid (OF) samples. OF samples were prepared by protein precipitation using ice-cold acetonitrile. Chromatographic separation was achieved by gradient elution on a Luna Phenyl Hexyl column (50 × 2 mm, 5 μm), while detection was carried out on a QTrap 4000 instrument in positive ionization mode. The limits of detection ranged from 0.02 to 0.40 ng/mL, whereas the lower limits of quantification ranged from 0.2 to 4.0 ng/mL. The method was applied to authentic samples collected during two preliminary studies in order to obtain insights into the general detectability and detection windows of synthetic cannabinoids in this matrix. The results indicate that synthetic cannabinoids are transferred from the blood stream into OF and vice versa only at a very low rate. Therefore, positive OF samples are due to contamination of the oral cavity during smoking. As these drug-contaminations could be detected up to approximately 2 days, neat oral fluid appears to be well suited for detection of a recent synthetic cannabinoid use. Quantification of synthetic cannabinoids in biofluids by means of LC/ESI-MS/MS

Keywords: ‘Spice’; Synthetic cannabinoids; Neat oral fluid; LC/ESI-MS/MS; Detection window

Detection, quantification, and identification of dermorphin in equine plasma and urine by LC–MS/MS for doping control by Fuyu Guan; Cornelius E. Uboh; Lawrence R. Soma; Mary Robinson; George A. Maylin; Xiaoqing Li (pp. 4707-4717).

Dermorphin is a unique opioid peptide that is 30–40 times more potent than morphine. It was misused and went undetected in horse racing until 2011 when intelligence obtained from a few North American race tracks suggested its use. To prevent such misuse, a reliable analytical method became necessary for detection and identification of dermorphin in post-race horse samples. This paper describes the first liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for such a purpose. Equine plasma and urine samples were pre-treated with ethylenediamine tetra-acetic acid and urea prior to solid-phase extraction (SPE) on Oasis MCX cartridges. Resulting eluates were dried under vacuum and analyzed by LC–MS/MS for dermorphin. The matrix effect, SPE efficiency, intra-day and inter-day accuracy and precision, and stability of the analyte were assessed. The limit of detection was 10 pg/mL in plasma and 20 pg/mL in urine, and the limit of confirmation was 20 pg/mL in plasma and 50 pg/mL in urine. Dermorphin in plasma is stable at ambient temperature, but its diastereomer is unstable. With isotopically labeled dermorphin as an internal standard, the quantification range was 20–10,000 pg/mL in plasma and 50–20,000 pg/mL in urine. The intra-day and inter-day accuracy was from 91 % to 100 % for the low, intermediate, and high concentrations. The intra-day and inter-day coefficients of variation were less than 12 %. The method differentiates dermorphin from its diastereomer. This method is very specific for identification of dermorphin in equine plasma and urine, as assessed by BLAST search and targeted SEQUEST search, and by MS/MS spectrum library search. The method has been successfully applied to analysis of samples collected following dermorphin administration to research horses and of official post-race samples. Figure ᅟ

Keywords: Dermorphin; Doping; Solid-phase extraction; Opioid peptide; Liquid chromatography–mass spectrometry; Equine

Repeat MALDI MS imaging of a single tissue section using multiple matrices and tissue washes by Rory T. Steven; Josephine Bunch (pp. 4719-4728).

Matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI MSI) techniques are continually being assessed with a view to improving the quality of information obtained from a given sample. A single tissue section will typically only be analyzed once by MALDI MSI and is then either used for histological staining or discarded. In this study, we explore the idea of repeat analysis of a single tissue section by MALDI MSI as a route toward improving sensitivity, structural characterization, and diversity of detected analyte classes. Repeat analysis of a single tissue section from a fresh frozen mouse brain is investigated with both α-cyano-4-hydroxycinnamic acid (CHCA) and para-nitroaniline (PNA). Repeat analysis is then applied to the acquisition of MALDI MSI and MALDI tandem mass spectrometry imaging employing collision induced dissociation (MS/MS imaging employing CID) from a formalin-fixed mouse brain section. Finally, both lipid and protein data are acquired from the same tissue section via repeat analysis utilizing CHCA, sinapinic acid (SA), and a tissue wash step. PNA was found to outperform CHCA as a matrix for repeat analysis; multiple lipids were identified using MS/MS imaging; both lipid and protein images were successfully acquired from a single tissue section. Figure Repeat analysis by MALDI MS imaging of a single tissue section is investigated with multiple matrices and tissue washes to provide increased molecular information from a single tissue section

Keywords: MALDI; Mass spectrometry imaging; Lipid; Protein; Tandem mass spectrometry

Impact of homogeneous and filamentary discharge modes on the efficiency of dielectric barrier discharge ionization mass spectrometry by Cordula Meyer; Saskia Müller; Bienvenida Gilbert-Lopez; Joachim Franzke (pp. 4729-4735).

The present study contributes to the evaluation of dielectric barrier discharge-based ambient ionization for mass spectrometric analysis (DBDI-MS) by providing a further step towards an understanding of underlying ionization processes. This examination highlights the effect of physical discharge modes on the ionization efficiency of the DBDI source. A distinction is made between the homogeneous and filamentary discharge mode due to different plasma gases in barrier configurations. Therefore, we first report on discharge modes of DBDI by demonstrating a universally applicable method to classify the predominant modes. Then, the ionization efficiency of these two modes is evaluated by a laser desorption-DBDI-MS with different molecular analytes. Here, the laser desorption is used to deliver neutral analytes which will be ionized by the plasma jet applied as dielectric barrier discharge ionization. With a clear increase of signal intensities in the homogeneous mode in contrast to the filamentary one, the present study indicates a pronounced dependence of the ionization efficiency on the discharge mode allowing further insight into the mechanisms of the ionization process. Figure He-DBD-jet, propazine mass spectrum, MHCD

Keywords: Ambient ionization; Soft ionization; Dielectric barrier discharge; Homogeneous discharge; Filamentary discharge

Rapid determination of 5-hydroxymethylfurfural by DART ionization with time-of-flight mass spectrometry by Aleš Rajchl; Ladislava Drgová; Adéla Grégrová; Helena Čížková; Rudolf Ševčík; Michal Voldřich (pp. 4737-4745).

DART (direct analysis in real time), a novel technique with wide potential for rapid screening analysis, coupled with high-resolution time-of-flight mass spectrometry (TOF-MS) has been used for quantitative analysis of 5-hydroxymethylfurfural (5-HMF), a typical temperature marker of food. The DART/TOF-MS method was optimised and validated. Quantification of 5-HMF was achieved by use of a stable isotope-labelled 5-HMF standard prepared from glucose. Formation of 5-HMF from saccharides, a potential source of overestimation of results, was evaluated. Forty-four real samples (honey and caramelised condensed sweetened milk) and 50 model samples of heated honey were analysed. The possibility of using DART for analysis of heated samples of honey was confirmed. HPLC and DART/TOF-MS methods for determination of 5-HMF were compared. The correlation equation between these methods was DART = 1.0287HPLC + 0.21340, R ² = 0.9557. The DART/TOF-MS method has been proved to enable efficient and rapid determination of 5-HMF in a variety of food matrices, for example honey and caramel.

Keywords: DART; 5-HMF; HPLC; TOF-MS; Honey; Caramel

Identification of non-volatile compounds and their migration from hot melt adhesives used in food packaging materials characterized by ultra-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry by Paula Vera; Elena Canellas; Cristina Nerín (pp. 4747-4754).

The identification of unknown non-volatile migrant compounds from adhesives used in food contact materials is a very challenging task because of the number of possible compounds involved, given that adhesives are complex mixtures of chemicals. The use of ultra-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UPLC-MS/QTOF) is shown to be a successful tool for identifying non-targeted migrant compounds from two hot melt adhesives used in food packaging laminates. Out of the seven migrants identified and quantified, five were amides and one was a compound classified in Class II of the Cramer toxicity. None of the migration values exceeded the recommended Cramer exposure values.

Keywords: Adhesives; Food packaging; Migration; UPLC-MS/QTOF; NIAS

Development and certification of a reference material for Fusarium mycotoxins in wheat flour by Robert Köppen; Wolfram Bremser; Tatjana Rasenko; Matthias Koch (pp. 4755-4763).

Deoxynivalenol (DON), nivalenol (NIV) and zearalenone (ZEN) are toxic secondary metabolites produced by several species of Fusarium fungi. These mycotoxins are often found together in a large variety of cereal-based foods, which are regulated by maximum content levels of DON and ZEN. To date, suitable certified reference materials (CRM) intended for quality control purposes are lacking for these Fusarium mycotoxins. In order to overcome this lack, the first CRM for the determination of DON, NIV and ZEN in naturally contaminated wheat flour (ERM®-BC600) was developed in the framework of a European Reference Materials (ERM®) project. This article describes and discusses the whole process of ERM®-BC600 development, including material preparation, homogeneity and stability studies, and an interlaboratory comparison study for certification. A total of 21 selected expert laboratories from different European countries with documented expertise in the field of mycotoxin analysis took part in the certification study using various gas and liquid chromatographic methods. The certified values and their corresponding expanded uncertainties (k = 2) were assigned in full compliance with the requirements of ISO Guide 35 and are as follows: 102 ± 11 μg kg⁻¹ for DON, 1000 ± 130 μg kg⁻¹ for NIV and 90 ± 8 μg kg⁻¹ for ZEN.

Keywords: Deoxynivalenol; Nivalenol; Zearalenone; Food; ERM; Quality assurance

Dispersive microextraction based on magnetic polypyrrole nanowires for the fast determination of pesticide residues in beverage and environmental water samples by Qin Zhao; Qian Lu; Yu-Qi Feng (pp. 4765-4776).

In this study, magnetic polypyrrole nanowires (mPPYs) were fabricated via a simple co-mixing method based on an “aggregation-wrap” mechanism. The polypyrrole (PPy) nanowires were synthesized by in situ chemical oxidative polymerization using cetyltrimethylammonium bromide as the “soft template” and the magnetic nanoparticles (MNPs) prepared using solvothermal methods. Typically, when these two nanomaterials were vortically mixed in a solvent, the MNPs were wrapped into the PPy nanowire networks that formed during the aggregation process, leading to the formation of mPPYs which can be separated from the solvent rapidly and conveniently by a magnet. Due to the better permeability, good adsorption ability, and magnetic separability of the resultant material, mPPYs were applied for the enrichment of 11 pesticides including organophosphorus, organochlorine, and pyrethroid using magnetic solid phase extraction (MSPE) to test their feasibility in sample preparation. Several parameters affecting the extraction efficiency were investigated, and under the optimized conditions, a simple and effective method for the determination of pesticide residues was established by coupling with gas chromatography/mass spectrometry (GC/MS) analysis. The whole pretreatment process was rapid and can be accomplished within 15 min. The linearity range of the proposed method was 0.2–10 μg/L, with correlation coefficients (R) of 0.995–0.999; the limits of quantification for the target compounds were in the range of 0.09–0.29 μg/L. In addition, an acceptable reproducibility was achieved by evaluating the intra- and inter-day precisions with relative standard deviations of less than 14 and 16 %, respectively. Finally, the established MSPE-GC/MS method was successfully applied for the determination of pesticide residues in beverage teas, juices, and environmental water samples. Figure Facile preparation of mPPYs based on “aggregation-wrap”

Keywords: Magnetic polypyrrole nanowires; Pesticides; Magnetic solid phase extraction; Gas chromatography/mass spectrometry

Use of gel permeation chromatography for clean-up in the analysis of coccidiostats in eggs by liquid chromatography–tandem mass spectrometry by J. Chico; A. Rúbies; F. Centrich; R. Companyó; M. D. Prat; M. Granados (pp. 4777-4786).

An analytical method for determination and confirmation of nine coccidiostatics in eggs is reported. Ethyl acetate is used as extraction solvent, with satisfactory results, and simple automated clean-up is based on gel-permeation chromatography (GPC) . The target compounds are then analysed by liquid chromatography–electrospray ionization–tandem mass spectrometry. The method was validated in-house in accordance with Commission Decision 2002/657/EC. Trueness and precision were determined at four concentrations, and the mean errors obtained were <10 %, with relative standard deviations ranging from 3 to 18 %. For three non-authorized coccidiostatics (clopidol, ethopabate, and ronizadole), decision limit and detection capability were in the ranges 0.12–0.16 and 0.18–0.23 μg kg⁻¹, respectively. The results obtained prove the suitability of this new analytical method for routine monitoring of these substances in eggs.

Keywords: Food analysis; Coccidiostatics residues; Eggs; GPC; LC–MS–MS; Clean-up

Preparation techniques alter the mineral and organic fractions of fish otoliths: insights using Raman micro-spectrometry by Aurélie Jolivet; Ronan Fablet; Jean-François Bardeau; Hélène de Pontual (pp. 4787-4798).

The high spatial resolution analysis of the mineral and organic composition of otoliths using Raman micro-spectrometry involves rigorous protocols for sample preparation previously established for microchemistry and trace elements analyses. These protocols often include otolith embedding in chemically neutral resin (i.e., resins which do not contain, in detectable concentration, elements usually sought in the otoliths). Such embedding may however induce organic contamination. In this paper, Raman micro-spectrometry reveals the presence of organic contamination onto the surface obtained from the use of epoxy resin, specifically Araldite. This contamination level varies depending on otolith structures. Core and checks, known as structural discontinuities, exhibit the most important level of contaminations. Our results suggest that otolith embedding with resin affects the organic matrix of the otolith, probably through an infiltration of the resin in the crystalline structure. The interpretation of chemical otolith signatures, especially Raman otolith signatures, and stable isotope analyses should then be revised in light of these results. In this respect, we propose a method for the correction of Raman otolith signatures for contamination effects.

Keywords: Epoxy resin; Otolith composition; Microstructure; Raman spectrometry

LC-QTOF/MS metabolomic profiles in human plasma after a 5-week high dietary fiber intake by Anna Johansson-Persson; Thaer Barri; Matilda Ulmius; Gunilla Önning; Lars Ove Dragsted (pp. 4799-4809).

The objective was to investigate the alterations of plasma metabolome profiles to identify exposure and effect markers of dietary fiber intake. Subjects (n = 25) aged 58.6 (1.1) years (mean and SD) with a body mass index of 26.6 (0.5) kg/m² were given a high fiber (HF) and a low fiber (LF) diet, in a 5-week randomized controlled crossover intervention. The HF diet consisted of oat bran, rye bran, and sugar beet fiber incorporated into test food products, whereas the LF diet was made of equivalent food products to the HF diet, but without adding fibers. Blood plasma samples were collected at the start and end of each intervention period and analyzed by LC-QTOF/MS. In total, 6 features in positive mode and 14 features in negative mode were significantly different between the HF and the LF diet (p < 0.01, q < 0.05). Two markers, 2,6-dihydroxybenzoic acid and 2-aminophenol sulfate, were increased after HF diet, along with a tentatively identified saponin derived from oat avenacosides. The untargeted metabolomics approach enabled the identification of two new markers of dietary fiber intake in human plasma. Further studies will be needed to verify if these markers could serve as compliance markers of fiber intake.

Keywords: LC-QTOF/MS; Metabolomics; Oat; Rye; Sugar beet; Dietary fiber

Discovery of safety biomarkers for realgar in rat urine using UFLC-IT-TOF/MS and ¹H NMR based metabolomics by Yin Huang; Yuan Tian; Geng Li; Yuanyuan Li; Xinjuan Yin; Can Peng; Fengguo Xu; Zunjian Zhang (pp. 4811-4822).

As an arsenical, realgar (As₄S₄) is known as a poison and paradoxically as a therapeutic agent. However, a complete understanding of the precise biochemical alterations accompanying the toxicity and therapy effects of realgar is lacking. Using a combined ultrafast liquid chromatography (UFLC) coupled with ion trap time-of-flight mass spectrometry (IT-TOF/MS) and ¹H NMR spectroscopy based metabolomics approach, we were able to delineate significantly altered metabolites in the urine samples of realgar-treated rats. The platform stability of the liquid chromatography LC/MS and NMR techniques was systematically investigated, and the data processing method was carefully optimized. Our results indicate significant perturbations in amino acid metabolism, citric acid cycle, choline metabolism, and porphyrin metabolism. Thirty-six metabolites were proposed as potential safety biomarkers related to disturbances caused by realgar, and glycine and serine are expected to serve as the central contacts in the metabolic pathways related to realgar-induced disturbance. The LC/MS and NMR based metabolomics approach established provided a systematic and holistic view of the biochemical effects of realgar on rats, and might be employed to investigate other drugs or xenobiotics in the future. Figure Pipeline of safety biomarkers discovery for realgar in rat urine by metabolomics

Keywords: Realgar; Metabolomics; Liquid chromatography–mass spectrometry; NMR; Urine; Biomarker

Assaying the efficacy of dual-antiplatelet therapy: use of a controlled-shear-rate microfluidic device with a well-defined collagen surface to track dynamic platelet adhesion by Margaret B Lucitt; Sinead O’Brien; Jonathan Cowman; Gerardene Meade; Lourdes Basabe-Desmonts; Martin Somers; Nigel Kent; Antonio J. Ricco; Dermot Kenny (pp. 4823-4834).

We report the development and demonstration of an assay that distinguishes the pharmacological effects of two widely used antiplatelet therapies, aspirin (COX-1 inhibitor) and clopidogrel (P2Y₁₂ inhibitor). Whole blood is perfused through a low-volume microfluidic device in contact with a well-characterized (ellipsometry, atomic force microscopy) acid-soluble type I collagen surface. Whole human blood treated in vitro with a P2Y₁₂ inhibitor 2-methylthioadenosine 5′-monophosphate triethylammonium salt (2-MeSAMP) extended the time to the start of platelet recruitment, i.e., platelet binding to the collagen surface. Treatment with 2-MeSAMP also slowed the rate of aggregate buildup, with an overall reduced average platelet aggregate area after 8 min of constant blood flow. A far smaller effect was observed for in vitro treatment with aspirin, for which the rate of change of surface coverage is indistinguishable from controls. In whole blood obtained from patients under treatment with dual-antiplatelet therapy (aspirin and clopidogrel), a significant extension of time to platelet recruitment was observed along with a slowed rate of aggregate buildup and an average aggregate size approximately half that of control measurements. Differentiation of the pharmacological effects of these two well-targeted antiplatelet pathways suggests a role for this assay in determining the antiplatelet effects of these and related new therapeutics in clinical settings.

Keywords: Keywords; Antiplatelet therapy; Collagen–platelet interactions; Microfluidics; Parallel-plate flow chamber; Thrombosis

Comparative study of some robust statistical methods: weighted, parametric, and nonparametric linear regression of HPLC convoluted peak responses using internal standard method in drug bioavailability studies by Mohamed A. Korany; Hadir M. Maher; Shereen M. Galal; Marwa A. A. Ragab (pp. 4835-4848).

This manuscript discusses the application and the comparison between three statistical regression methods for handling data: parametric, nonparametric, and weighted regression (WR). These data were obtained from different chemometric methods applied to the high-performance liquid chromatography response data using the internal standard method. This was performed on a model drug Acyclovir which was analyzed in human plasma with the use of ganciclovir as internal standard. In vivo study was also performed. Derivative treatment of chromatographic response ratio data was followed by convolution of the resulting derivative curves using 8-points sin x i polynomials (discrete Fourier functions). This work studies and also compares the application of WR method and Theil's method, a nonparametric regression (NPR) method with the least squares parametric regression (LSPR) method, which is considered the de facto standard method used for regression. When the assumption of homoscedasticity is not met for analytical data, a simple and effective way to counteract the great influence of the high concentrations on the fitted regression line is to use WR method. WR was found to be superior to the method of LSPR as the former assumes that the y-direction error in the calibration curve will increase as x increases. Theil's NPR method was also found to be superior to the method of LSPR as the former assumes that errors could occur in both x- and y-directions and that might not be normally distributed. Most of the results showed a significant improvement in the precision and accuracy on applying WR and NPR methods relative to LSPR. Figure Comparison between RSD (percent) and E _r (percent) calculated for Acyclovir, for area, D ₁, and D ₁/FF in the internal standard methods, using the three types of regression models: parametric, nonparametric, and weighted

Keywords: Weighted regression method; Nonparametric regression; Chemometrics; HPLC; Fourier transform; Bioavailability

Method development and validation for rat serum fingerprinting with CE–MS: application to ventilator-induced-lung-injury study by Shama Naz; Antonia Garcia; Magdalena Rusak; Coral Barbas (pp. 4849-4858).

In the search for a noninvasive and reliable rapid screening method to detect biomarkers, a metabolomics fingerprinting approach was developed and applied to rat serum samples using capillary electrophoresis coupled to an electrospray ionization-time of flight-mass spectrometer (CE–TOF-MS). An ultrafiltration method was used for sample pretreatment. To evaluate performance the method was validated with carnitine, choline, ornithine, alanine, acetylcarnitine, betaine, and citrulline, covering the entire electropherogram of pool of rat serum. The linearity for all metabolites was >0.99, with good recovery and precision. Approximately 34 compounds were also confirmed in the pool of rat serum. The method was successfully applied to real serum samples from rats with ventilator-induced lung injury, an experimental rat model for acute lung injury (ALI), giving a total of 1163 molecular features. By use of univariate and multivariate statistics 18 significant compounds were found, of which five were confirmed. The involvement of arginase and nitric oxide synthase has been proved for other lung diseases, meaning the increase of asymmetric dimethyl arginine (ADMA) and ornithine and the decrease of arginine found were in accordance with published literature. Ultimately this fingerprinting approach offers the possibility of identifying biomarkers that could be regularly screened for as part of routine disease control. In this way it might be possible to prevent the development of ALI in patients in critical care units. Figure A fingerprinting approach in serum using capillary electrophoresis and mass spectrometry

Keywords: Capillary electrophoresis; Metabolomics; Fingerprinting; Serum; Ventilator induced lung injury; Asymmetric dimethyl arginine

Immobilized lipodisks as model membranes in high-throughput HPLC-MS analysis by Elinor Meiby; Malin Morin Zetterberg; Sten Ohlson; Víctor Agmo Hernández; Katarina Edwards (pp. 4859-4869).

Lipodisks, also referred to as polyethylene glycol (PEG)-stabilized bilayer disks, have previously been demonstrated to hold great potential as model membranes in drug partition studies. In this study, an HPLC-MS system with stably immobilized lipodisks is presented. Functionalized lipodisks were immobilized on two different HPLC support materials either covalently by reductive amination or by streptavidin–biotin binding. An analytical HPLC column with immobilized lipodisks was evaluated by analysis of mixtures containing 15 different drug compounds. The efficiency, reproducibility, and stability of the system were found to be excellent. In situ incorporation of cyclooxygenase-1 (COX-1) in immobilized lipodisks on a column was also achieved. Specific binding of COX-1 to the immobilized lipodisks was validated by interaction studies with QCM-D. These results, taken together, open up the possibility of studying ligand interactions with membrane proteins by weak affinity chromatography.

Keywords: Lipodisks; COX-1; HPLC-MS; Model membrane; Drug partition studies; Membrane protein; WAC; Weak affinity chromatography

Immobilized purine nucleoside phosphorylase from Schistosoma mansoni for specific inhibition studies by Marcela Cristina de Moraes; Carmen L. Cardoso; Quezia B. Cass (pp. 4871-4878).

The parasite Schistosoma mansoni (Sm) depends exclusively on the salvage pathway for its purine requirements. The enzyme purine nucleoside phosphorylase (PNP) is, therefore, a promising target for development of antischistosomal agents and an assay for screening of inhibitors. To enable this, immobilized SmPNP reactors were produced. By quantification of hypoxanthine by liquid chromatography, kinetic constants (K _M) for the substrate inosine were determined for the free and immobilized enzyme as 110 ± 6.90 μmol L −1 and 164 ± 13.4 μmol L −1, respectively, indicating that immobilization did not affect enzyme activity. Furthermore, the enzyme retained 25 % of its activity after four months. Non-Michaelis kinetics for the phosphate substrate, and capacity for P_i-independent hydrolysis were also demonstrated, despite the low rate of enzymatic catalysis. Use of an SmPNP immobilized enzyme reactor (IMER) for inhibitor-screening assays was demonstrated with a small library of 9-deazaguanine analogues. The method had high selectivity and specificity compared with screening by use of the free enzyme by the Kalckar method, and furnished results without the need for verification of the absence of false positives. Figure A cartoon illustrating the online SmPNP-IMER activity assay

Keywords: Schistosomiasis; Enzymatic inhibition assays; Immobilized enzyme reactors; Purine nucleoside phosphorylase

Comparison of comet assay parameters for estimation of genotoxicity by sum of ranking differences by K. Sunjog; S. Kolarević; K. Héberger; Z. Gačić; J. Knežević-Vukčević; B. Vuković-Gačić; M. Lenhardt (pp. 4879-4885).

The genotoxic potential of waters in six rivers and reservoirs from Serbia was monitored in different tissues of chub (Squalius cephalus L. 1758) with the alkaline comet assay. The comet assay, or single-cell gel electrophoresis, has a wide application as a simple and sensitive method for evaluating DNA damage in fish exposed to various xenobiotics in the aquatic environment. Three types of cells, erythrocytes, gill cells, and liver cells, were used for assessing DNA damage. Images of randomly selected cells were analyzed with a Leica fluorescence microscope and image analysis by software (Comet Assay IV Image analysis system, PI, UK). Three parameters (tail length—l, tail intensity—i, and Olive tail moment—m) were analyzed on 1,700 nuclei per cell type. The procedure for sum of ranking differences (SRD) was implemented to compare different types of cells and different parameters for estimation of DNA damage. Regarding our nine different estimations of genotoxicity: tail length, intensity, and moment in erythrocytes (rel, rei, rem), liver cells (rll, rli, rlm), and gill cells (rgl, rgi, rgm), the SRD procedure has shown that the Olive tail moment and tail intensity are (almost) equally good parameters; the SRD value was lower for the tail moment and tail intensity than for tail length in the case of all types of cells. The least reliable parameter was rel; close to the borderline case were rei, rll, and rgl (∼5 % probability of random ranking). Figure Comparison of comet assay parameters

Keywords: Ecogenotoxicity; Comet assay; Comparison; Parameters; Ordering; Fluorescence

Elimination of autofluorescence in fluorescence correlation spectroscopy using the AzaDiOxaTriAngulenium (ADOTA) fluorophore in combination with time-correlated single-photon counting (TCSPC) by Ryan M. Rich; Mark Mummert; Zygmunt Gryczynski; Julian Borejdo; Thomas Just Sørensen; Bo W. Laursen; Zeno Foldes-Papp; Ignacy Gryczynski; Rafal Fudala (pp. 4887-4894).

Fluorescence correlation spectroscopy (FCS) is a frequently applied technique that allows for the precise and sensitive analysis of molecular diffusion and interactions. However, the potential of FCS for in vitro or ex vivo studies has not been fully realized due in part to artifacts originating from autofluorescence (fluorescence of inherent components and fixative-induced fluorescence). Here, we propose the azadioxatriangulenium (ADOTA) dye as a solution to this problem. The lifetime of the ADOTA probe, about 19.4 ns, is much longer than most components of autofluorescence. Thus, it can be easily separated by time-correlated single-photon counting methods. Here, we demonstrate the suppression of autofluorescence in FCS using ADOTA-labeled hyaluronan macromolecules (HAs) with Rhodamine 123 added to simulate diffusing fluorescent background components. The emission spectrum and decay rate of Rhodamine 123 overlap with the usual sources of autofluorescence, and its diffusion behavior is well known. We show that the contributions from Rhodamine 123 can be eliminated by time gating or by fluorescence lifetime correlation spectroscopy (FLCS). While the pairing of ADOTA and time gating is an effective strategy for the removal of autofluorescence from fluorescence imaging, the loss of photons leads to erroneous concentration values with FCS. On the other hand, FLCS eliminates autofluorescence without such errors. We then show that both time gating and FLCS may be used successfully with ADOTA-labeled HA to detect the presence of hyaluronidase, the overexpression of which has been observed in many types of cancer.

Keywords: Fluorescence; Fluorescence correlation spectroscopy; Hyaluronan; Time-correlated single-photon counting

Chloroaluminum phthalocyanine thin films: chemical reaction and molecular orientation by Florian Latteyer; Heiko Peisert; Johannes Uihlein; Tamara Basova; Peter Nagel; Michael Merz; Stefan Schuppler; Thomas Chassé (pp. 4895-4904).

The chemical transformation of the polar chloroaluminum phthalocyanine, AlClPc, to μ-(oxo)bis(phthalocyaninato)aluminum(III), (PcAl)₂O, in thin films on indium tin oxide is studied and its influence on the molecular orientation is discussed. The studies were conducted using complementary spectroscopic techniques: Raman spectroscopy, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. In addition, density functional theory calculations were performed in order to identify specific vibrations and to monitor the product formation. The thin films of AlClPc were annealed in controlled environmental conditions to obtain (PcAl)₂O. It is shown that the chemical transformation in the thin films can proceed only in the presence of water. The influence of the reaction and the annealing on the molecular orientation was studied with Raman spectroscopy and NEXAFS spectroscopy in total electron yield and partial electron yield modes. The comparison of the results obtained from these techniques allows the determination of the molecular orientation of the film as a function of the probing depth. Illustration of the dimerization reaction of MClPc to (PcM)₂O.

Keywords: Interface/surface analysis; Thin films; Chloroaluminum phthalocyanine

Selective fluorescence response and magnetic separation probe for 2,4,6-trinitrotoluene based on iron oxide magnetic nanoparticles by Wen-Sheng Zou; Ya-Qin Wang; Feng Wang; Qun Shao; Jun Zhang; Jin Liu (pp. 4905-4912).

Despite the rapid development of nanomaterials and nanotechnology, it is still desirable to develop novel nanoparticle-based techniques which are cost-effective, timesaving, and environment-friendly, and with ease of operation and procedural simplicity, for assay of target analytes. In the work discussed in this paper, the dye fluorescein isothiocyanate (FITC) was conjugated to 1,6-hexanediamine (HDA)-capped iron oxide magnetic nanoparticles (FITC–HDA Fe₃O₄ MNPs), and the product was characterized. HDA ligands on the surface of Fe₃O₄ MNPs can bind 2,4,6-trinitrotoluene (TNT) to form TNT anions by acid–base pairing interaction. Formation of TNT anions, and captured TNT substantially affect the emission of FITC on the surface of the Fe₃O₄ MNPs, resulting in quenching of the fluorescence at 519 nm. A novel FITC–HDA Fe₃O₄ MNPs-based probe featuring chemosensing and magnetic separation has therefore been constructed. i.e. FITC–HDA Fe₃O₄ MNPs had a highly selective fluorescence response and enabled magnetic separation of TNT from other nitroaromatic compounds by quenching of the emission of FITC and capture of TNT in aqueous solution. Very good linearity was observed for TNT concentrations in the range 0.05–1.5 μmol L⁻¹, with a detection limit of 37.2 nmol L⁻¹ and RSD of 4.7 % (n = 7). Approximately 12 % of the total amount of TNT was captured. The proposed methods are well-suited to trace detection and capture of TNT in aqueous solution. Figure Iron oxide magnetic nanoparticles-based selective fluorescent response and magnetic separation probe for 2,4,6-trinitrotoluene

Keywords: Fluorescence resonance energy transfer (FRET); Iron oxide magnetic nanoparticles (Fe₃O₄ MNPs); 2,4,6-trinitrotoluene (TNT); Chemosensor; Magnetic separation

Application of graphene for the analysis of pharmaceuticals and personal care products in wastewater by Yong Yu; Laosheng Wu (pp. 4913-4919).

A novel and reliable analytical method based on a graphene adsorbent for solid-phase extraction (SPE) derivatized with N-tert-butyldimethylsilyl-N- methyltrifluoroacetamide and analyzed by gas chromatography–mass spectrometry was developed for determination of nine pharmaceuticals and personal care products (PPCPs) in wastewater samples. Different ratios of graphene/silica gel were tested, with 20 % graphene/silica gel giving the best performance as an SPE adsorbent. The mean recoveries of the target analytes obtained by 20 % graphene/silica gel SPE ranged from 58.1 to 87.6 %. The limit of quantification ranged from 30 to 259 ng/L and from 13 to 115 ng/L for the influent and effluent, respectively. By comparing the accuracy and precision of 20 % graphene/silica gel and Oasis HLB SPE cartridges, we demonstrated that the method can be satisfactorily used for the analysis of PPCPs in wastewater samples. We applied the method to wastewater samples from a sewage treatment plant near Riverside, California, to track the concentration change of PPCPs in the treatment processes.

Keywords: Pharmaceuticals and personal care products; Graphene; Solid-phase extraction; Gas chromatography–mass spectrometry

Ultrasensitive electrochemiluminescent immunosensor based on dual signal amplification strategy of gold nanoparticles-dotted graphene composites and CdTe quantum dots coated silica nanoparticles by Yan Zhang; Weijian Dai; Fang Liu; Long Li; Meng Li; Shenguang Ge; Mei Yan; Jinghua Yu (pp. 4921-4929).

A facile and ultrasensitive electrochemiluminescent (ECL) immunosensor for detection of prostate-specific antigen (PSA) was designed by using CdTe quantum dots coated silica nanoparticles (SiO₂@QDs) as bionanolabels. To construct such an electrochemiluminescence immunosensor, gold nanoparticles-dotted graphene composites were immobilized on the working electrode, which can increase the surface area to capture a large amount of primary antibodies as well as improve the electronic transmission rate. The as-prepared SiO₂@QDs used as bionanolabels, showed good ECL performance and good ability of immobilization for secondary antibodies. The approach provided a good linear response ranging from 0.005 to 10 ng mL⁻¹ with a low detection limit of 0.0032 ng mL⁻¹. Such immunosensor showed good precision, acceptable stability, and reproducibility. Satisfactory results were obtained for determination of PSA in human serum samples. Therefore, the proposed method provides a new promising platform of clinical immunoassay for other biomolecules.

Keywords: Gold nanoparticles-dotted graphene; CdTe quantum dots coated silica nanoparticles; Electrochemiluminescent; Immunoassay

Potentiometric sensor for determination of neutral bisphenol A using a molecularly imprinted polymer as a receptor by Li-Juan Kou; Rong-Ning Liang; Xue-Wei Wang; Yan Chen; Wei Qin (pp. 4931-4936).

The aim of this paper is to develop a potentiometric sensing methodology for sensitive and selective determination of neutral phenols by using a molecularly imprinted polymer as a receptor. Bisphenol A (BPA), a significant environmental contaminant, is employed as the model target. The BPA-imprinted polymer is synthesized by the semi-covalent technique and incorporated into a plasticized poly(vinyl chloride) membrane doped with the tridodecylmethylammonium salt. The present electrode shows a linear anionic potential response over the concentration range from 0.1 to 1 μM with a detection limit of 0.02 μM, and exhibits an excellent selectivity over other phenols. The proposed approach has been successfully applied to the determination of BPA released from real plastic samples. It offers promising potential in development of potentiometric sensors for measuring neutral phenols at trace levels.

Keywords: Molecularly imprinted polymers; Ion-selective electrodes; Bisphenol A; Phenols

Mass spectrometric analysis reveals O-methylation of pyruvate kinase from pancreatic cancer cells by Weidong Zhou; Michela Capello; Claudia Fredolini; Leda Racanicchi; Erica Dugnani; Lorenzo Piemonti; Lance A. Liotta; Francesco Novelli; Emanuel F. Petricoin (pp. 4937-4943).

Pyruvate kinase (PK) is an important glycolytic enzyme that catalyzes the dephosphorylation of phosphoenolpyruvate to pyruvate. Human PK isozyme M2 (PKM2), a splice variant of M1, is overexpressed in many cancer cells, and PKM2 has been investigated as a potential tumor marker for diagnostic assays and as a target for cancer therapy. To facilitate identification and characterization of PK, we studied the enzyme from pancreatic cancer cells and normal pancreatic duct cells by electrophoresis and mass spectrometry, and identified multiple O-methylated residues from PK. These findings advance our knowledge of the biochemical properties of PK and will be important in understanding its biological function in cells. Figure Pyruvate kinase (PK) is an important glycolytic enzyme that catalyzes the dephosphorylation of phosphoenolpyruvate to pyruvate. We studied the enzyme from pancreatic cancer cells and normal pancreatic duct cells by mass spectrometry, and identified multiple O-methylated residues from PK.

Keywords: PKM2; Mass spectrometry; Pancreatic cancer; Metabolism; Methylation

Multivariate determination of ¹³CO₂/¹²CO₂ ratios in exhaled mouse breath with mid-infrared hollow waveguide gas sensors by Felicia Seichter; Andreas Wilk; Katharina Wörle; Seong-Soo Kim; Josef A. Vogt; Ulrich Wachter; Peter Radermacher; Boris Mizaikoff (pp. 4945-4951).

The ¹²CO₂/¹³CO₂ isotope ratio is a well-known marker in breath for a variety of biochemical processes and enables monitoring, e.g., of the glucose metabolism during sepsis. Using animal models—here, at a mouse intensive care unit—the simultaneous determination of ¹²CO₂ and ¹³CO₂ within small volumes of mouse breath was enabled by coupling a novel low-volume hollow waveguide gas cell to a compact Fourier transform infrared spectrometer combined with multivariate data evaluation based on partial least squares regression along with optimized data preprocessing routines.

Keywords: FT-IR spectroscopy; Mid-infrared gas sensor; Hollow waveguide; Mouse sepsis model; Glucose/insulin metabolism disorder; ¹³CO₂ enrichment; TTR; Multivariate data analysis

Chip-based nLC-TOF-MS is a highly stable technology for large-scale high-throughput analyses by L. Renee Ruhaak; Sandra L. Taylor; Suzanne Miyamoto; Karen Kelly; Gary S. Leiserowitz; David Gandara; Carlito B. Lebrilla; Kyoungmi Kim (pp. 4953-4958).

Many studies focused on the discovery of novel biomarkers for the diagnosis and treatment of disease states are facilitated by mass spectrometry-based technology. HPLC coupled to mass spectrometry is widely used; miniaturization of this technique using nano-liquid chromatography (LC)-mass spectrometry (MS) usually results in better sensitivity, but is associated with limited repeatability. The recent introduction of chip-based technology has significantly improved the stability of nano-LC-MS, but no substantial studies to verify this have been performed. To evaluate the temporal repeatability of chip-based nano-LC-MS analyses, N-glycans released from a serum sample were repeatedly analyzed using nLC-PGC-chip-TOF-MS on three non-consecutive days. With an average inter-day coefficient of variation of 4 %, determined on log₁₀-transformed integrals, the repeatability of the system is very high. Overall, chip-based nano-LC-MS appears to be a highly stable technology, which is suitable for the profiling of large numbers of clinical samples for biomarker discovery.

Keywords: Biomarker discovery; Nano-LC-MS; Time of flight; N-Glycans

“Do it yourself” reference materials for δ ¹³C determinations by isotope ratio mass spectrometry by J. F. Carter; B. Fry (pp. 4959-4962).

A method is described to prepare inexpensive organic reference materials for routine stable isotope work. The method blends isotope-enriched and isotope-depleted materials to match closely international measurement standards. Examples are presented showing how ¹³C-enriched and ¹³C-depleted glucose were blended to match the isotopic compositions of the international carbon isotope standards, NBS 19 and L-SVEC. Preparation of the blended standards was straightforward, and the prepared solutions proved easy to dispense into tin capsules and easy to combust in a conventional isotope analysis system. The blended materials allow a laboratory to perform a two-point calibration for isotopic composition on a daily basis, with the use of an international reference material recommended for routine quality assurance. The blending method can be applied widely to make isotope standards for other elements and compounds.

Keywords: Stable isotope ratio measurements; Isotope ratio mass spectrometry; Reference materials; Quality assurance

Quantitative measurements of glutathione in yeast cell lysate using ¹H NMR by Steve Y. Rhieu; Aaron A. Urbas; Katrice A. Lippa; Vytas Reipa (pp. 4963-4968).

Methods for quantifying the level of glutathione (GSH) in yeast cell lysate are described using ¹H NMR analysis. For quantification purposes, the ¹H resonances corresponding to the Cys βCH₂ of GSH were identified as having the fewest overlapping spectral interferences from lysate matrix components using GSH spiked yeast lysate samples. Two methods, standard addition based on peak integration and a spectral subtraction approach, were evaluated for quantifying GSH in lysate samples. The peak integration procedure required baseline estimation and a peak fitting step to correct for background interferences while the spectral subtraction procedure was comparatively straightforward. The level of GSH measured by ¹H NMR was in good agreement with the concentration measured by the DTNB-GSSG reductase recycling assay. The proposed NMR method can lead to a reliable quantitation of GSH and could be applicable to a variety of other analytes of interest in complex biological matrices.

Keywords: Quantitative NMR; Spectral subtraction; Glutathione

Versatile synthesis of probes for high-throughput enzyme activity screening by Tristan de Rond; Pamela Peralta-Yahya; Xiaoliang Cheng; Trent R. Northen; Jay D. Keasling (pp. 4969-4973).

Mass spectrometry based technologies are promising as generalizable high-throughput assays for enzymatic activity. In one such technology, a specialized enzyme substrate probe is presented to a biological mixture potentially exhibiting enzymatic activity, followed by an in situ enrichment step using fluorous interactions and nanostructure-initiator mass spectrometry. This technology, known as Nimzyme, shows great potential but is limited by the need to synthesize custom substrate analogs. We describe a synthetic route that simplifies the production of these probes by fashioning their perfluorinated invariant portion as an alkylating agent. This way, a wide variety of compounds can be effectively transformed into enzyme activity probes. As a proof of principle, a chloramphenicol analog synthesized according to this methodology was used to detect chloramphenicol acetyltransferase activity in cell lysate. This verifies the validity of the synthetic strategy employed and constitutes the first reported application of Nimzyme to a non-carbohydrate-active enzyme. The simplified synthetic approach presented here may help advance the application of mass spectrometry to high-throughput enzyme activity determination. Figure The Nimzyme high-throughput enzyme activity assay allows for the detection of enzyme activity in cell lysate. Fluorous interactions between a specialized substrate probe and a nanostructure-initiator mass spectrometry surface allow for in situ cleanup and the subsequent collection of unambiguous mass spectra. One of the main hurdles that prevents the widespread adoption of this technology is the need to chemically synthesize the required probes. Here, we present a simplified route to derive Nimzyme probes from a wide variety of biologically interesting substrates.

Keywords: Enzyme assays; High-throughput; Nimzyme; Nanostructure-initiator mass spectrometry; Chloramphenicol acetyltransferase

Application of cyclic biamperometry to viability and cytotoxicity assessment in human corneal epithelial cells by Mehdi Rahimi; Hyun-Yi Youn; David J. McCanna; Jacob G. Sivak; Susan R. Mikkelsen (pp. 4975-4979).

The application of cyclic biamperometry to viability and cytotoxicity assessments of human corneal epithelial cells has been investigated. Electrochemical measurements have been compared in PBS containing 5.0 mM glucose and minimal essential growth medium. Three different lipophilic mediators including dichlorophenol indophenol, 2-methyl-1,4-naphthoquinone (also called menadione or vitamin K₃) and N,N,N′,N′-tetramethyl-p-phenylenediamine have been evaluated for shuttling electrons across the cell membrane to the external medium. Transfer of these electrons to ferricyanide in the extra cellular medium results in the accumulation of ferrocyanide. The amount of ferrocyanide is then determined using cyclic biamperometry and is related to the extent of cell metabolic activity and therefore cell viability. To illustrate cytotoxicity assessment of chemicals, hydrogen peroxide, benzalkonium chloride and sodium dodecyl sulfate have been chosen as sample toxins, the cytotoxicities of which have been evaluated and compared to values reported in the literature. Similar values have been reported using colorimetric assays; however, the simplicity of this electrochemical assay can, in principle, open the way to miniaturization onto lab-on-chip devices and its incorporation into tiered-testing approaches for cytotoxicity assessment. Figure After mediated reduction of ferricyanide by cell components, its reduced form, ferrocyanide, is quantitated using cyclic biamperometry in presence of excess ferricyanide. Concentration of ferrocyanide is then related to the extent of cell metabolic activity for viability/cytotoxicity assessments

Keywords: Cyclic biamperometry; Cytotoxicity; Viability; Mediated electrochemistry; Human corneal epithelial cells; Benzalkonium chloride; Sodium dodecylsulfate; Hydrogen peroxide

Analysis of triacylglycerol hydroperoxides in human lipoproteins by Orbitrap mass spectrometer by Shu-Ping Hui; Toshihiro Sakurai; Seiji Takeda; Shigeki Jin; Hirotoshi Fuda; Takao Kurosawa; Hitoshi Chiba (pp. 4981-4987).

Herein, we represent a simple method for the detection and characterization of molecular species of triacylglycerol monohydroperoxides (TGOOH) in biological samples by use of reversed-phase liquid chromatography with a LTQ Orbitrap XL mass spectrometer (LC/LTQ Orbitrap) via an electrospray ionization source. Data were acquired using high-resolution, high-mass accuracy in Fourier-transform mode. Platform performance, related to the identification of TGOOH in human lipoproteins and plasma, was estimated using extracted ion chromatograms with mass tolerance windows of 5 ppm. Native low-density lipoproteins (nLDL) and native high-density lipoproteins (nHDL) from a healthy donor were oxidized by CuSO₄ to generate oxidized LDL (oxLDL) and oxidized HDL (oxHDL). No TGOOH molecular species were detected in the nLDL and nHDL, whereas 11 species of TGOOH molecules were detected in the oxLDL and oxHDL. In positive-ion mode, TGOOH was found as [M + NH₄]⁺. In negative-ion mode, TGOOH was observed as [M + CH₃COO]^–. TGOOH was more easily ionized in positive-ion mode than in negative-ion mode. The LC/LTQ Orbitrap method was applied to human plasma and three molecular species of TGOOH were detected. The limit of detection is 0.1 pmol (S/N = 10:1) for each synthesized TGOOH. Figure Analysis of triacylglycerol hydroperoxides in human lipoproteins by Orbitrap mass spectrometer

Keywords: Triacylglycerol hydroperoxides; TGOOH; Orbitrap; Liquid chromatography/electrospray ionization mass spectrometry; LC/MS; Triglyceride

Sensitive detection of trace hemoglobin using fluorescence method based on functionalized quantum dots by Houjuan Zhu; Suhua Wang (pp. 4989-4991).

The fluorescence quenching of quantum dots by hemoglobin has been demonstrated to depend on surface functionalization, and this property has been utilized to construct a novel fluorescent method for rapid, sensitive, and selective detection of trace hemoglobin in urine at microgram level. This method shows low interference and high selectivity for hemoglobin with a limit of detection of 4.3 μg L⁻¹ in water and 66.1 μg L⁻¹ in urine, which are lower than those of currently used methods in labs and clinics. Spike and recovery tests in raw, acidified, and alkalized urine samples exhibit good recovery rates for the spiked concentrations close to the limit of detection. Figure Fluorescence spectra and photographs of MPA-QD solution before and after the addition of Hb taken under 365-nm irradiation.

Keywords: Optical sensors; Fluorescence/luminescence; Nanoparticles/nanotechnology; Semiconductor materials; Biosensors

Bamboo charcoal as a novel solid-phase microextraction coating material for enrichment and determination of eleven phthalate esters in environmental water samples by Ru-Song Zhao; Yan-Long Liu; Jia-Bin Zhou; Xiang-Feng Chen; Xia Wang (pp. 4993-4996).

This study demonstrates the potential of bamboo charcoal as a novel and inexpensive solid-phase microextraction (SPME) coating material for enrichment and determination of organic pollutants in water samples. Bamboo charcoal was prepared and used as a SPME coating material. Eleven phthalate esters (PAEs) were used as model analytes, and gas chromatography–mass spectrometry was used for separation and detection. Important extraction conditions (ionic strength, stirring rate, and extraction time) and desorption conditions (desorption temperature and time) were systematically investigated and optimized. Linearity of 0.1–100 μg L⁻¹ and correlation coefficients of 0.9992–0.9998 were obtained under optimum conditions. Inter-day and intra-day repeatability were 2.15–9.93 % and 1.89–9.85 %, respectively, and fiber-to-fiber reproducibility was 5.42–9.66 %. On the basis of a chromatographic signal-to-baseline noise ratio of three, the limits of detection reached 0.004–0.023 μg L⁻¹. Satisfactory results were achieved when the bamboo coating was used for determination of 11 PAEs in real water samples. The experimental results indicate that bamboo charcoal has significant potential as a SPME coating material for rapid enrichment and sensitive determination of organic pollutants in environmental samples.

Keywords: Bamboo charcoal; Solid-phase microextraction; Phthalate esters; Gas chromatography–mass spectrometry

Quantum dot-based lateral flow immunoassay for detection of chloramphenicol in milk by Anna N. Berlina; Nadezhda A. Taranova; Anatoly V. Zherdev; Yuri Y. Vengerov; Boris B. Dzantiev (pp. 4997-5000).

A novel rapid (20 min) fluorescent lateral flow test for chloramphenicol (CAP) detection in milk was developed. The chosen format is a binding-inhibition assay. Water-soluble quantum dots with an emission peak at 625 nm were applied as a label. Milk samples were diluted by 20 % with phosphate buffer to eliminate the matrix effect. The result of the assay could be seen by eye under UV light excitation or registered by a portable power-dependent photometer. The limit of CAP detection by the second approach is 0.2 ng/mL, and the limit of quantitation is 0.3 ng/mL. Figure Principle of proposed immunoassay of chloramphenicol using quantum dots

Keywords: Chloramphenicol; Milk; Quantum dots; Lateral flow assay

Sections

Personal tools

Analytical and Bioanalytical Chemistry (v.405, #14)

Sections

Personal tools

Local resources

Analytical and Bioanalytical Chemistry (v.405, #14)