Matrix-Assisted Photochemical Vapor Generation for the Direct Determination of Mercury in Domestic Wastewater by Atomic Fluorescence Spectrometry

In this article, matrix-assisted photochemical vapor generation is proposed for the direct determination of mercury in domestic wastewater by atomic fluorescence spectrometry. With the ultraviolet light irradiation, the matrix (low-molecular-weight organic compounds) in domestic wastewater samples can produce reducing species. These reducing species could reduce mercury from mercury (II) to elemental mercury, subsequently swept by argon to atomic fluorescence spectrometry for detection. The effects of several factors, such as material of the photoreaction coil, ultraviolet light wavelength, ultraviolet light irradiation time, and flow rate of carrier gas, were investigated. Under the optimized condition, a limit of detection of 0.1 µg L^?1 was obtained. The standard addition method was used for the spiked mercury domestic wastewater sample analysis, with a relative standard deviation (n = 11, at 20 µg L^?1) of 4.8%, and recovery test results ranged from 81% to 110%. The proposed method was applied to analyze two certified reference materials and four domestic wastewater samples, with analytical results in good agreement with certified values or those obtained by ICP-MS. Interferences from common transition metals and alkaline metals as well as alkaline earth metals were also investigated. This is a simple, reagent-free, cost-effective, green method for mercury determination in domestic wastewater.     

Detection of melamine in infant formula and grain powder by surface-assisted laser desorption/ionization mass spectrometry

We have developed a method for the determination of melamine (MEL), ammeline (AMN), and ammelide (AMD) by surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) using gold nanoparticles (Au NPs). The major peaks for MEL, AMN, and AMD at m/z 127.07, 128.05, and 129.04 are assigned to the [MEL + H](+), [AMN + H](+), and [AMD + H](+) ions. Because the three tested compounds adsorb weakly onto the surfaces of the Au NPs through Au-N bonding, they can be easily concentrated from complex samples by applying a simple trapping/centrifugation process. The SALDI-MS method provides limits of detection of 5, 10, and 300 nM for MEL, AMN, and AMD, respectively, at a signal-to-noise ratio of 3. The signal variation for 150-shot average spectra of the three analytes within the same spot was 15%, and the batch-to-batch variation was 20%. We have validated the practicality of this approach by the analysis of these three analytes in infant formula and grain powder. This simple and rapid SALDI-MS approach holds great potential for screening of MEL in foods.     

Ultrahigh resolution mass spectrometry and accurate mass measurements for high-throughput food lipids profiling

In the present study, accurate mass measurements by ultrahigh resolution mass spectrometry with Orbitrap-Exactive working at resolving power R: 100,000 (m/z 200, full width at half maximum) with an accuracy better than 2?ppm in all the mass range (m/z 200 to 2000) were used to show a detailed molecular composition of diverse edible oils and fats. Flow injection was used to introduce samples into the mass spectrometer, obtaining a complete analysis of each sample in less than 10 min, including blanks. Meticulous choice of organic solvents and optimization of the ion source and Orbitrap mass analyzer parameters were carried out, in order to achieve reproducible mass spectra giving reliable elemental compositions of the lipid samples and to prevent carry over. More than 200 elemental compositions attributable to diacylglycerols, triacylglycerols (TAGs), and their oxidation products have been found in the spectra of food lipids from different origin. Several compounds with very close molecular mass could only be resolved through ultrahigh resolution, allowing detailed and robust TAG profiling with a high characterization potential. Copyright ? 2012 John Wiley & Sons, Ltd.     

The use of mass defect in modern mass spectrometry

Mass defect is defined as the difference between a compound's exact mass and its nominal mass. This concept has been increasingly used in mass spectrometry over the years, mainly due to the growing use of high resolution mass spectrometers capable of exact mass measurements in many application areas in analytical and bioanalytical chemistry. This article is meant as an introduction to the different uses of mass defect in applications using modern MS instrumentation. Visualizing complex mass spectra may be simplified with the concept of Kendrick mass by plotting nominal mass as a function of Kendrick mass defect, based on hydrocarbons subunits, as well as slight variations on this theme. Mass defect filtering of complex MS data has been used for selectively detecting compounds of interest, including drugs and their metabolites or endogenous compounds such as peptides and small molecule metabolites. Several strategies have been applied for labeling analytes with reagents containing unique mass defect features, thus shifting molecules into a less noisy area in the mass spectrum, thus increasing their detectability, especially in the area of proteomics. All these concepts will be covered to introduce the interested reader to the plethora of possibilities of mass defect analysis of high resolution mass spectra.     

Ultra trace determination of fluorobenzoic acids in reservoir and ground water using isotope dilution gas chromatography mass spectrometry

The accurate ultra-trace analysis of six fluorobenzoic acids (FBAs) via isotope dilution gas chromatography mass spectrometry through their deuterated analogues is described. North Sea reservoir and ground water samples were spiked with six deuterated FBAs (dFBAs), enriched using solid-phase extraction (SPE) and analysed using GC/MS after derivatisation with BF ₃· MeOH. All FBAs were enriched and determined simultaneously. SPE allowed a 250-fold enrichment of the acids if 100 mL of sample volume was used. The method enables the determination of FBAs down to the range of 8–37 ng L ^?1 with recoveries between 66 % and 85 %. It uses low amounts of chemicals and is adaptable to larger and smaller sample volumes.     

Routine analysis by high precision gas chromatography/mass selective detector/isotope ratio mass spectrometry to 0.1 parts per mil

Stable isotope methods are potentially quite useful for validating natural or enhanced mineral degradation of contaminants. For this reason, a continuous flow gas chromatograph (GC), isotope ratio mass spectrometer (IRMS) has been coupled with a quadrupole mass selective detector (MSD) to allow simultaneous mass spectral and stable carbon isotope ratio data to be obtained from a single chromatographic analysis. This allows the target contaminant and any extra-cellular degradation intermediates to be both qualified and quantified. Previously acceptable limits of precision (0.3 parts per mil) are undesirable given the small fractionation observed during aerobic degradation. To further understand the fate of organic contaminants and to gain information about the metabolic degradative pathway employed by a microorganism, routine isotopic analyses on a range of analytes have been performed. Quantities of sample producing mass-44 ion beam signal (I(44)) of 2 x 10(-10) to 1 x 10(-8) A were analysed. When the IRMS was tuned for high sensitivity, ion source nonlinearities were overcome by peak height correction from an algorithm that was produced using known isotopic standards of varying concentrations. This led to sample accuracy of <0.01 per thousand and sample precision of 0.1 per thousand. Copyright 1999 John Wiley & Sons, Ltd.     

Environmental Water Samples Analysis of Pesticides by Means of Chemometrics Combined with Fluorimetric Multioptosensing

A single flow-through optosensor spectrofluorimetric system is proposed for the resolution of mixtures of three pesticides, α-naphthol, o-phenylphenol and thiabendazole, at μg l⁻¹ levels using a partial least-squares (PLS) calibration approach. The sensor was developed in conjunction with a monochannel flow-injection analysis system with fluorimetric detection using C₁₈ silicagel as an active sorbent substrate in the flow cell. By using 20% methanol-water (v:v) solution as carrier solution, the multisensor responds linearly in the measuring range without requiring additional reagents or derivatization. First derivative emission spectra of the corresponding analytes recorded during the process of retention-elution were used to provide multivariate data. The different kinetic on the retention process of the analytes on the sensing zone allows the selection of a time matrix for each analyte providing best results in the PLS approach. Accurate prediction results were obtained for the three analytes with RMSEP values of 1.86%, 3.34% and 0.50% were obtained for α-naphtol, o-phenylphenol and thiabendazole respectively. In the analysis of environmental waters samples, a mean recovery of 103% was obtained.     

LC-MS/MS analysis of Δ9-tetrahydrocannabinolic acid A in serum after protein precipitation using an in-house synthesized deuterated internal standard

An assay based on liquid chromatography/tandem mass spectrometry is presented for the fast, precise and sensitive quantitation of Δ9-tetrahydrocannabinolic acid A (THCA) in serum. THCA is the biogenetic precursor of Δ9-tetrahydrocannabinol in cannabis and has aroused interest in the pharmacological and forensic field especially as a potential marker for recent cannabis use. After addition of deuterated THCA, synthesized from D(3)-THC as starting material, and protein precipitation, the analytes were separated using gradient elution on a Luna C18 column (150 × 2.0 mm × 5 μm) with 0.1% formic acid and acetonitrile/0.1% formic acid. Data acquisition was performed on a triple quadrupole linear ion trap mass spectrometer in multiple reaction monitoring mode with negative electrospray ionization. After optimization, the following sample preparation procedure was used: 200 μL serum was spiked with internal standard solution and methanol and then precipitated 'in fractions' with 500 μL ice-cold acetonitrile. After storage and centrifugation, the supernatant was evaporated and the residue redissolved in mobile phase. The assay was fully validated according to international guidelines including, for the first time, the assessment of matrix effects and stability experiments. Limit of detection was 0.1 ng/mL, and limit of quantification was 1.0 ng/mL. The method was found to be selective and proved to be linear over a range of 1.0 to 100 ng/mL using a 1/x weighted calibration model with regression coefficients >0.9996. Accuracy and precision data were within the required limits (RSD ≤ 8.6%, bias: 2.4 to 11.4%), extractive yield was greater than 84%. The analytes were stable in serum samples after three freeze/thaw cycles and storage at -20 °C for one month.     

Simultaneous analysis of several synthetic cannabinoids, THC, CBD and CBN, in hair by ultra-high performance liquid chromatography tandem mass spectrometry. Method validation and application to real samples

A simple procedure for the quantitative detection of JWH-018, JWH-073, JWH 200, JWH-250, HU-210, Δ(9)-tetrahydrocannabinol (THC), cannabidiol (CBD) and cannabinol (CBN) in hair has been developed and fully validated. After digestion with NaOH and liquid-liquid extraction, the separation was performed with an ultra-high performance liquid chromatography system coupled to a triple quadrupole mass spectrometer operating in the selected reaction monitoring mode. The absence of matrix interferents, together with excellent repeatability of both retention times and relative abundances of diagnostic transitions, allowed the correct identification of all analytes tested. The method was linear in two different intervals at low and high concentration, with correlation coefficient values between 0.9933 and 0.9991. Quantitation limits ranged from 0.07 pg/mg for JWH-200 up to 18 pg/mg for CBD The present method for the determination of several cannabinoids in hair proved to be simple, fast, specific and sensitive. The method was successfully applied to the analysis of 179 real samples collected from proven consumers of Cannabis, among which 14 were found positive to at least one synthetic cannabinoid.     

Computational approach to structural identification of phospholipids using raw mass spectra from nanoflow liquid chromatography-electrospray ionization-tandem mass spectrometry

A qualitative analysis tool (LiPilot) for identifying phospholipids (PLs), including lysophospholipids (LPLs), from biological mixtures is introduced. The developed algorithm utilizes raw data obtained from nanoflow liquid chromatography-electrospray ionization-tandem mass spectrometry experiments of lipid mixture samples including retention time and m/z values of precursor and fragment ions from data-dependent, collision-induced dissociation. Library files based on typical fragmentation patterns of PLs generated with an LTQ-Velos ion trap mass spectrometer are used to identify PL or LPL species by comparing experimental fragment ions with typical fragment ions in the library file. Identification is aided by calculating a confidence score developed in our laboratory to maximize identification efficiency. Analysis includes the influence of total ion intensities of matched and unmatched fragment ions, the difference in m/z values between observed and theoretical fragment ions, and a weighting factor used to differentiate regioisomers through data filtration. The present study focused on targeted identification of particular PL classes. The identification software was evaluated using a mixture of 24 PL and LPL standards. The software was further tested with a human urinary PL mixture sample, with 93 PLs and 22 LPLs identified. Copyright ? 2012 John Wiley & Sons, Ltd.     

SPME-GC-MS快速分析炼油厂废水中痕量VOCs

采用固相微萃取-气相色谱-质谱联用(SPME-GC-MS)对炼油厂废水中痕量挥发性有机化合物(VOCs)进行了定性分析,简化了预处理过程,总分析时间为1h左右.对比处理前后的废水样品的MS定性结果,为废水处理工艺的评价以及有机物降解机理提供了依据.     

SPME-GC-MS快速分析炼油厂废水中痕量VOCs

采用固相微萃取 -气相色谱 -质谱联用 (SPME- GC- MS)对炼油厂废水中痕量挥发性有机化合物(VOCs)进行了定性分析 ,简化了预处理过程 ,总分析时间为 1h左右。对比处理前后的废水样品的 MS定性结果 ,为废水处理工艺的评价以及有机物降解机理提供了依据。     

Silver nanoparticles as matrix for laser desorption/ionization mass spectrometry of peptides

Silver nanoparticle synthesized from chemical reduction has been successfully utilized as a matrix in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) of peptides. Acting as a substrate to adsorb analytes, as well as a transmission medium for UV laser, silver nanoparticle was found to assist in the desorption/ionization of peptides with little or no induced fragmentation. The size of the nanoparticle was typically in the range of 160 ± 20 nm. One of the key advantages of silver nanoparticle for peptides analysis is its simple step for on-probe sample preparation. In addition, it also minimizes the interferences of sodium dodecyl sulfate (SDS) surfactant background signal, resulting in cleaner mass spectra and more sensitive signal, when compared to α–cyano-4-hydroxycinnamic acid (CCA) matrix.     

Optimization of Pretreatment Method for Alkylmercuries Speciation in Coal by High‐Performance Liquid Chromatography Coupled with UV‐Digestion Cold Vapor Atomic Fluorescence Spectrometry

Abstract

Exhaustive extraction of analytes in their original chemical forms from samples with complex matrices is a pivotal step for speciation analysis. Herein we propose a pretreatment method for extracting and preconcentrating methylmercury and ethylmercury from coal samples by using KBr–H₂SO₄/CuSO₄–C₆H₅CH₃–Na₂S₂O₃ system. The extraction conditions, including the volume of the organic phase and the extraction time, were optimized in detail. Speciation analysis of alkylmercuries was carried out by high‐performance liquid chromatography online coupled with UV‐digestion and cold vapor atomic fluorescence spectrometry. The detection limits were 0.6 ng mL^?1 for methylmercury and 1 ng mL^?1 for ethylmercury, respectively. The recoveries of methylmercury and ethylmercury spiked in a sample were 84% and 82%, respectively. The method was applied successfully to analysis of alkylmercuries in four coal samples collected from northeast China.     

Rapid speciation and quantification of selenium compounds by HPLC-ICP MS using multiple standards labelled with different isotopes

Speciation analysis using high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP MS) is now commonly used to investigate metabolic and toxicological aspects of some metals and metalloids. We have developed a rapid method for simultaneous identification and quantification of metabolites of selenium (Se) compounds using multiple standards labelled with different isotopes. A mixture of the labelled standards was spiked in a selenised garlic extract and the sample was subjected to speciation analysis by HPLC-ICP MS. The selenised garlic contains γ-glutamyl-methylselenocysteine, methylselenocysteine, and selenomethionine and the concentrations of those Se compounds were 723.8, 414.8, and 310.7 ng Se ml(-1), respectively. The isotopically labelled standards were also applied to the speciation of Se in rat urine. Selenate, methylselenonic acid, selenosugar, and trimethyselenium ions were found to be excreted by the present speciation procedure. Multiple standards labelled with different stable isotopes enable high-throughput identification and quantitative measurements of Se metabolites.     

Preconcentration and Determination of Manganese and Nickel from Various Water Samples by Nano Zirconium Oxide/Boron Oxide

ABSTRACT

This work assesses the potential of the adsorptive material nano zirconium oxide/boron oxide (ZrO₂/B₂O₃) for removal of trace Mn(II) and Ni(II) from environmental samples. This method is based on the sorption of Mn(II) and Ni(II) ions directly onto nanosorbent, followed by the elution and determination by flame atomic absorption spectrometry (FAAS). Experimental parameters, including pH of sample solution, volume and concentration of eluent, sample volume, and flow rate of sample solution, that affect the recovery of the Mn(II) and Ni(II) ions from model solutions have been optimized. Under the optimum conditions, adsorption isotherms and adsorption capacities have been examined. The recoveries of Mn(II) and Ni(II) were 96% ± 2% and 95% ± 3% at 95% confidence level, respectively. The analytical detection limits for Mn(II) and Ni(II) were 1.9 and 4.9 µ g L^?1, respectively. Adsorption capacities of the nano ZrO₂/B₂O₃ were found as 92.8 mg g^?1 for Mn and 168.4 mg g^?1 for Ni. The accuracy of the method was checked by analyzing certified reference material (SPS-WW1 wastewater) and spiked real samples. The method was applied for the determination of analytes in water samples.     

Restricted access magnetic materials prepared by dual surface modification for selective extraction of therapeutic drugs from biological fluids

Magnetic porous particles with dual functionality have been prepared by a two-step procedure and evaluated as novel restricted access materials for extraction of therapeutic agents from biological fluids. The magnetic silica particles served as scaffolds were first modified with diol groups, which were then converted to octadecyl esters through reaction with stearoyl chloride. In the second step, the octadecyl esters on the exterior surface were hydrolyzed by the action of lipase to yield magnetic particles with hydrophobic reversed-phase ligands on the inner surface and biocompatible diol groups on the outer surface. The restricted access behavior of the resulting materials was confirmed by differential binding of small molecules such as methotrexate (MTX), leucovorin (LV) and folic acid (FA) relative to bovine serum albumin. While MTX, LV and FA were all bound to the magnetic particles with high affinity, the adsorption of the protein was markedly reduced due to size exclusion effect. The utility of the magnetic particles for sample preparation was tested in solid-phase extraction of MTX, LV and FA from spiked human serum and the effects of the SPE conditions on the recovery of the analytes were systematically studied. Moreover, the magnetic particle-based sample preparation procedure coupled with reversed-phase liquid chromatography analysis was validated in terms of specificity, linearity and reproducibility. The method was shown to be free from interference of endogenous compounds and linear over the concentration range of 0.5-10 μg/mL for the three drugs studied. The limits of detection for the three drugs in serum were in the range of 0.160−0.302 μg/mL. Reproducibility expressed as the RSD of the recovery for ten replicated extractions at three different concentrations was found to be less than 8.93%. With a unique combination of surface functionality with magnetic cores, the restricted access magnetic particles may be adapted in automated and high throughput protocols for routine analysis of a large volume of clinical samples.     

In situ derivatization-liquid liquid extraction as a sample preparation strategy for the determination of urinary biomarker prolyl-4-hydroxyproline by liquid chromatography-tandem mass spectrometry

Polar analytes that possess protic functional groups have often been treated with alkyl chloroformates to decrease their polarity and increase their volatility prior to gas chromatography-mass spectrometry analysis. This derivatization reaction has two distinct advantages. It proceeds smoothly in aqueous media, and the desired reaction products are efficiently separated from interfering ionic components by their extraction into a water-immiscible organic phase. In the present work, the derivatization-liquid liquid sample preparation was examined in detail for analysis of a potential urinary dipeptide biomarker L-prolyl-4-L-hydroxyproline (PHP) by downstream liquid chromatography coupled to electrospray mass spectrometry. PHP was treated with a series of alkyl and fluoroalkyl chloroformates in aqueous media, and the detected reaction products were investigated. Smooth conversion of PHP into the N-isobutyloxycarbonyl isobutyl ester was accomplished by the coupled action of isobutanol, isobutyl chloroformate and the pyridine catalyst. This derivative afforded a highest detector response from all the derivatized forms examined, including the nonderivatized PHP. A simple isocratic elution on a common RP-C18 HPLC column coupled with tandem mass spectrometry, and use of the synthesized heptadeuterated analog (D7-PHP) as an internal standard, enabled validation of the method and determination of PHP in human urine in less than 5?min. The in situ derivatization-liquid liquid extraction has thus been demonstrated to be a useful sample preparation strategy for the analysis of polar metabolites by liquid chromatography-tandem mass spectrometry in the complex urine matrix.     

电感耦合等离子体发射光谱测定植物精油中的重金属元素

植物精油是从芳香植物提取的天然复杂化合物,作为芳香植物的次生代谢产物具有挥发性和浓郁香味,其特有的多样化生物活性广泛应用于医药和化妆品行业.植物精油具有高渗透性,能以活跃的分子态渗透皮肤组织,经淋巴腺吸收后进入血液,其所含的重金属元素也极易随植物精油进入人体对健康构成潜在威胁.采用硝酸-双氧水对植物精油进行微波消解,在...     

Rapid speciation and quantification of selenium compounds by HPLC-ICP MS using multiple standards labelled with different isotopes

Speciation analysis using high-performance liquid chromatography–inductively coupled plasma mass spectrometry (HPLC-ICP MS) is now commonly used to investigate metabolic and toxicological aspects of some metals and metalloids. We have developed a rapid method for simultaneous identification and quantification of metabolites of selenium (Se) compounds using multiple standards labelled with different isotopes. A mixture of the labelled standards was spiked in a selenised garlic extract and the sample was subjected to speciation analysis by HPLC-ICP MS. The selenised garlic contains γ-glutamyl-methylselenocysteine, methylselenocysteine, and selenomethionine and the concentrations of those Se compounds were 723.8, 414.8, and 310.7 ng Se ml^?1, respectively. The isotopically labelled standards were also applied to the speciation of Se in rat urine. Selenate, methylselenonic acid, selenosugar, and trimethyselenium ions were found to be excreted by the present speciation procedure. Multiple standards labelled with different stable isotopes enable high-throughput identification and quantitative measurements of Se metabolites.