Qualitative determination of low-molecular-weight organic acids in mixed hazardous wastes using thermospray liquid chromatography/mass spectrometry

A technique has been developed for the qualitative determination of low-molecular-weight organic acids in radioactive, mixed hazardous wastes using thermospray liquid chromatography/mass spectrometry. A tank waste was analyzed, and the results indicated the presence of citric, glycolic, acetic, and nitrosoiminodiacetic acid (NIDA). Further investigation revealed NIDA was formed under acidic conditions with the reaction of iminodiacetic acid and the high nitrate/nitrite concentration present in the waste.     

气质联用法测定纺织品中多种阻燃剂的研究

目前国内外常用的阻燃剂多为溴系、锑系和有机磷系产品[1].     

Quantitative determination of tiopronin in human plasma by LC-MS/MS without derivatization

Tiopronin (TP) is a synthetic thiol compound without chromophore. By optimizing the chromatographic conditions and sample preparation processes, an improved LC‐MS/MS analytical method without derivatization has been developed and validated to determine TP concentrations in human plasma. After reduction with 1,4‐dithiothreitol, plasma samples were deproteinized with 10% perchloric acid. The post‐treatment samples were analyzed on a C₈ column interfaced with a triple quadrupole tandem mass spectrometer in negative electrospray ionization mode. Methanol–5 mmol/L ammonium acetate (20:80, v/v) was used as the isocratic mobile phase. The assay was linear over the concentration range of 40.0–5000 ng/mL. The intra‐ and inter‐day precisions were within 12.9% in terms of relative standard deviation and the accuracy within 5.6% in terms of relative error. This simple and sensitive LC‐MS/MS method with short analytical time (3.5 min each sample) was successfully applied to the pharmacokinetic study of TP in healthy Chinese male volunteers after an oral dose of 300 mg TP. Copyright © 2011 John Wiley & Sons, Ltd.     

Identification of photocatalytic degradation products of diazinon in TiO2 aqueous suspensions using GC/MS/MS and LC/MS with quadrupole time-of-flight mass spectrometry

The photocatalytic degradation of the organophosphorus insecticide diazinon in aqueous suspensions has been studied by using titanium dioxide as a photocatalyst. The degradation of the insecticide was a fast process and included the formation of several intermediates that were identified using GC/ion-trap mass spectrometry with EI or CI in positive and negative ionization mode and HPLC/electrospray-QqTOF mass spectrometry. Since primarily hydroxy derivatives were identified in these aqueous suspensions, the mechanism of degradation was probably based on hydroxyl radical attack. The initial oxidative pathways of the degradation of diazinon involved the substitution of sulfur by oxygen on the Pz.dbnd6;S bond, cleavage of the pyrimidine ester bond, and oxidation of the isopropyl group. Exact mass measurements of the derivatives allowed the elemental formula of the molecules to be determined confidently. Similarities to the metabolic pathways occurring in living organisms were observed.     

Characterization of citrus and kiwi flavors and their degradation processes by combination of GC/FTIR and GC/MS

Flavor samples are complex mixtures with components of sometimes very similar chemical behavior (e.g. isomeres). As an approach towards their characterization an integrated analytical method on the basis of capillary gas-chromatography (HRGC) was applied consisting of two molecular specific techniques for component-identification in unknown samples: GC-FTIRS (GC-Fourier transform infrared spectrometry) and GC-MS (GC-mass spectrometry).In addition GC-retention indices-from simultaneous GC on two columns (nonpolar/polar) —were stored in a database for routine retrieval and quantitative monitoring. To correlate this information with sensory perception sniffing chromatograms were generated with the human nose as a high performance detector.Because of the high information contents of GC-FTIR spectra in this field a small but specific vapor-phase-FTIR flavor library was accumulated, which dramatically improved the fast identification power of GC-FTIRS alone.     

Quantitative determination of toluene,ethylbenzene, and xylene degradation products in contaminated groundwater by solid-phase extraction and in-vial derivatization

Benzylsuccinic acid (BSA) and methylbenzylsuccinic acids (mBSAs) are unambiguous indicators of anaerobic toluene and ethylbenzene/xylene degradation, and so the determination of these compounds in landfill leachates and contaminated groundwater is highly relevant. Samples were diluted to <0.8?mS?cm^?1 in order to reduce their ionic strength, and subsequently extracted through strong anion exchange disks, followed by simultaneous in-vial elution and methylation. A detection limit of 0.1?µg?L^?1 was obtained for 100?mL samples. Using this method, 19.3?µg?L^?1 of BSA was measured in a landfill leachate, and low µg?L^?1 levels of all of the mBSAs were measured in gasoline-contaminated groundwater. The results were compared with the findings of BSAs at 16 other contaminated sites, and BSAs as indicators of biodegradation were evaluated. The estimation of biodegradation rates based on parent hydrocarbons and BSA concentrations or ratios is questionable. However, the degradation products serve as good qualitative in situ indicators for anaerobic biodegradation in contaminated groundwater.     

Simultaneous determination of eight pesticide residues in coconut using MSPD and GC/MS

A simple and effective extraction method based on matrix solid-phase dispersion (MSPD) was developed to determine dimethoate, malathion, lufenuron, carbofuran, 3-hydroxycarbofuran, thiabendazole, difenoconazole and trichlorfon in coconut pulp using gas chromatography-mass spectrometry with selected ion monitoring (GC/MS, SIM). Different parameters of the method were evaluated, such as type of solid-phase (C(18), alumina, silica-gel and Florisil), the amount of solid-phase and eluent (dichloromethane, acetone, ethyl acetate, acetonitrile, n-hexane and n-hexane:ethyl acetate (1:1, v/v)). The best results were obtained using 0.5 g of coconut pulp, 1.0 g of C(18) as dispersant sorbent, 1.0 g of Florisil as clean-up sorbent and acetonitrile saturated with n-hexane as eluting solvent. The method was validated using coconut pulp samples fortified with pesticides at different concentration levels (0.25-1.0 mg kg(-1)). Average recoveries (four replicates) ranged from 70.1% to 98.7%, with relative standard deviations between 2.7% and 14.7%, except for lufenuron and difenoconazole, for which recoveries were 47.2% and 48.2%, respectively. Detection and quantification limits for coconut pulp ranged from 0.02 to 0.17 mg kg(-1) and from 0.15 to 0.25 mg kg(-1), respectively.     

Identification of Dinocap in water using GC/IR and GC/MS

The determination of Dinocap, one of the most often used acaricides and contact fungicides, is complicated by the fact that it consists of several isomeric alkyldinitro-phenyl-crotonates. In a first step, GC/IR and GC/MS has been used to separate the mixture, to determine the chromatographic behaviour and to fully characterize the six different isomeric compounds. The structures of additional impurities in the commerical preparation were shown to be the correlating phenols. An extraction/preconcentration method has been devised based on Carbopack B, yielding recoveries between 75 and 98%. A qualified estimation of the total Dinocap content of drinking water can be made by this approach for concentrations well below the limits set by the European drinking water regulations. The development of a complete analytical procedure based on these results appears to be feasible.Dedicated to Professor Dr. Dr. h.c. mult J. F. K. Huber on the occasion of his 70th birthday     

Ultra-trace determination of aquaculture chemotherapeutants and degradation products in environmental matrices by LC-MS/MS

Two of the most common products currently used to control parasitic sea lice in fin fish aquaculture, salmon in particular, are Slice® and AlphaMax®. Emamectin benzoate (EB) is the active ingredient in Slice® and deltamethrin is the active ingredient in AlphaMax®. Several analytical methods have been developed for the determination of the active ingredients in these products but these have been focused on specific matrices and lack the sensitivity and versatility required in environmental monitoring. Here we present a validated, versatile, and simple analytical method for the determination of EB, its desmethyl degradation product (AB), and deltamethrin in a wide range of environmental matrices (sea water, marine sediment, and tissue). Sediments and tissues were extracted by accelerated solvent extraction (ASE®) and sample cleanup was achieved by solid phase extraction (SPE) while sea water was extracted using SPE disks. Analyte identification and quantification was based on liquid chromatography tandem mass spectrometry (LC-MS/MS) instrumentation with electrospray ionization, and multiple reaction monitoring (MRM). Method detection limits for the target analytes was in the parts per trillion (pg?g^?1) level for tissue and sediment and parts per quadrillion (pg?L^?1) for water. Except for deltamethrin in sea water, method performance in terms of analyte recoveries was better than 60%, and the method precision was RSD<20%. The method was used to determine EB and AB concentrations in water, sediment and prawn tissue samples collected near salmon aquaculture sites treated with Slice®. A distinct concentration gradient was observed in the immediate vicinity (within 50 to 100?m radius) of the salmon aquaculture sites where EB was detected at low ng?g^?1 levels for tissue (EB ranged from 0.041 to 3.0?ng?g^?1) and sediment (EB ranged from 0.051 to 35?ng?g^?1) and pg?L^?1 levels (EB ranged from 3 to 209?pg?L^?1) for water samples.     

UV-assisted degradation of propiconazole in a TiO2 aqueous suspension: identification of transformation products and the reaction pathway using GC/MS

Photocatalytic degradation of propiconazole, a triazole pesticide, in the presence of titanium dioxide (TiO₂) under ultraviolet (UV) illumination was performed in a batch type photocatalytic reactor. A full factorial experimental design technique was used to study the main effects and the interaction effects between operational parameters in the photocatalytic degradation of propiconazole in a batch photo-reactor using the TiO₂ aqueous suspension. The effects of catalyst concentration (0.15–0.4 gL^?1), initial pH (3–9), initial concentration (5–35 mg L^?1) and light conditions were optimised at a reaction time duration of 90 min by keeping area/volume ratio constant at 0.919 cm² mL^?1. Photocatalytic oxidation of propiconazole showed 85% degradation and 76.57% mineralisation under UV light (365 nm/30 Wm^?2) at pH 6.5, initial concentration 25 mg L^?1 and constant temperature (25 ± 1 °C). The Langmuir–Hinshelwood kinetic model has successfully elucidated the effects of the initial concentration on the degradation of propiconazole and the data obtained are consistent with the available kinetic parameters. The photocatalytic transformation products of propiconazole were identified by using gas chromatography–mass spectrometry (GC/MS). The pathway of degradation obtained from mass spectral analysis shows the breakdown of transformation products into smaller hydrocarbons (m/z 28 and 39).     

Radiation-oxidation mechanisms: Volatile organic degradation products from polypropylene having selective C-13 labeling studied by GC/MS

PP samples, in which the three unique carbon atom positions along the chain were selectively labeled with C-13, have been subjected to γ-irradiation in the presence of oxygen, and the resulting organic volatile products analyzed by GC/MS. The isotopic labeling patterns in 33 organic degradation compounds have been assigned by comparison of the four mass spectra for each compound (from unlabeled PP, and from the three labeled PP materials). The volatile products have been “mapped” onto their positions of origin from the PP macromolecule, and insights have been gained into the chemistry through which these compounds must have formed. Most products show high specificity of isotopic labeling, indicating a single dominant reaction pathway. Oxidation chemistry occurred heavily at the C(2) tertiary carbon, with chemistry also at C(1) methylene. Methyl ketones are in abundance, along with alcohols, some aliphatic hydrocarbons, and other compound types. The C(3) methyl carbon remained attached to its original C(2) position in all catenated degradation products, and underwent no chemistry. However, products containing “non-catenated” carbons (i.e., not bonded to any other carbon atom) consisted entirely of a mix of C(3) and C(1). By examination of the labeling patterns, many products could be assigned to two successive chain scission events in close proximity, while others are clearly seen to arise from cleavage, followed by radical-radical recombination reactions. Interestingly, the former products (two chain scissions) are all found to have an odd number of carbon atoms along their chain, while the latter (scission followed by radical-radical reaction) all have an even number of carbons. An explanation of this odd/even phenomenon is provided in terms of the symmetry of the PP macromolecule.     

Quantitative determination of vitamin D metabolites in plasma using UHPLC-MS/MS

Vitamin D is an important determinant of bone health at all ages. The plasma concentrations of 25-hydroxy vitamin D (25-OH D) and other metabolites are used as biomarkers for vitamin sufficiency and function. To allow for the simultaneous determination of five vitamin D metabolites, 25-OH D₃, 25-OH D₂, 24,25-(OH)₂ D₃, 1,25-(OH)₂ D₃, and 1,25-(OH)₂ D₂, in low volumes of human plasma, an assay using ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS) was established. Plasma samples were spiked with isotope-labeled internal standards and pretreated using protein precipitation, solid-phase extraction (SPE) and a Diels–Alder derivatization step with 4-phenyl-1,2,4-triazoline-3,5-dione. The SPE recovery rates ranged from 55% to 85%, depending on the vitamin D metabolite; the total sample run time was <5 min. Mass spectrometry was conducted using positive ion electrospray ionization in the multiple reaction monitoring mode on a quadrupole–quadrupole-linear ion trap instrument after pre-column addition of methylamine to increase the ionization efficiency. The intra- and inter-day relative standard deviations were 1.6–4.1% and 3.7–6.8%, respectively. The limit of quantitation for these compounds was determined to be between 10 and 20 pg/mL. The 25-OH D results were compared with values obtained for reference materials (DEQAS). In addition, plasma samples were analyzed with two additional Diasorin antibody assays. All comparisons with conventional methods showed excellent correlations (r ² = 0.9738) for DEQAS samples, demonstrating the high degree of comparability of the new UHPLC-MS/MS technique to existing methods.     

Simultaneous determination of 32 antibiotics in aquaculture products using LC-MS/MS

An analytical multiclass, multi-residue method for the determination of antibiotics in aquaculture products was developed and validated. A fast, cheap, and straightforward extraction procedure followed by liquid chromatography-tandem mass spectrometry analysis was proposed. This method covers 32 antibiotics of different classes, which are frequently used in aquaculture. Three different extraction procedures were compared, and the extraction with acetonitrile (0.1 vol. % formic acid) showed the best results. The selected extraction procedure was validated at four different fortification levels (10 μg kg^?1, 25 μg kg^?1, 50 μg kg^?1, and 100 μg kg^?1). Recoveries of the tested antibiotics ranged from 70 % to 120 %, with the relative standard deviation (RSD) of triplicates lower than 20 %. The limits of quantification (LOQ) ranged from 0.062 μg kg^?1 to 4.6 μg kg^?1, allowing for the analysis of trace levels of these antibiotics in aquaculture products. The method was applied to the analysis of selected antibiotics in fish and shrimp meat available in the Czech market.     

Rapid extraction and determination of atrazine and its degradation products from microporous mineral sorbents using microwave-assisted solvent extraction followed by ultra-HPLC-MS/MS

We have evaluated three methods for the extraction of atrazine and six of its degradation products from microporous mineral sorbents. Soxhlet extraction and ultrasonic extraction, which work well on soils and sediments, recover only <15 % of the atrazine from a dealuminated Y zeolite. Closed-vessel microwave-assisted extraction, in contrast, gives much better recoveries. This is attributed to the accelerated mass transfer at elevated temperatures and the displacement by the solvent forced into the mineral micropores under elevated pressures. Under the optimized conditions, the recovery of atrazine from the hydrophilic Y zeolites (Si/Al ratios <8) is almost quantitative, and ～77 % for the more hydrophobic ones. The extraction efficiencies for the degradation products of atrazine in the hydrophilic zeolites (74.1–100 %) are also higher than those in the hydrophobic ones (22.3–44.2 %). The extracted compounds were quantified by a combination of ultra-HPLC and tandem MS and resulted in detection limits between 0.04 and 1.41 mg kg^?1 on a hydrophilic Y zeolite (Si/Al?=?2.55), and of 0.09–2.35 mg kg^?1 on a hydrophobic zeolite (Si/Al?=?15). The method was applied to study the degradation of atrazine sorbed on dealuminated Y zeolites.      

Analysis of odorous trichlorobromophenols in water by in-sample derivatization/solid-phase microextraction GC/MS

The simultaneous determination of several odorous trichlorobromophenols in water has been carried out by an in-sample derivatization headspace solid-phase microextraction method (HS-SPME).The analytical procedure involved their derivatization to methyl ethers with dimethyl sulfate/NaOH and further HS-SPME and gas chromatography-mass spectrometry (GC/MS) determination. Parameters affecting both the derivatization efficiency and headspace SPME procedures, such as the selection of the SPME fiber coating, derivatization–extraction time and temperature, were studied. The commercially available polydimethylsiloxane (PDMS) 100 μm and Carboxen-polydimethylsiloxane-divinylbenzene (CAR-PDMS-DVB) fibers appeared to be the most suitable for the simultaneous determination of these compounds. The precision of the HS-SPME/GC/MS method gave good relative standard deviations (RSDs) run-to-run between 9% and 19% for most of them, except for 2,5-diCl-6-Br-phenol, 2,6-diCl-3-Br-phenol and-2,3,6-triBr-phenol (22%, 25% and 23%, respectively). The method was linear over two orders of magnitude, and detection limits were compound dependent but ranged from 0.22 ng/l to 0.95 ng/l. The results obtained for water samples using the proposed SPME procedure were compared with those found with the EPA 625 method, and good agreement was achieved. Therefore, the in-sample derivatization HS-SPME/GC/MS procedure here proposed is a suitable method for the simultaneous determination of odorous trichlorobromophenols in water.     

Determination of bifonazole and identification of its photocatalytic degradation products using UPLC‐MS/MS

The main goal of the presented work was to investigate the effect of ZnO or/and TiO₂ on the stability of bifonazole in solutions under UVA irradiation. To this end, a simple and reproducible UPLC method for the determination of bifonazole in the presence of its photocatalytic degradation products was developed. Linearity was studied in the range of 0.0046–0.15 mg mL⁻¹ with a determination coefficient of 0.9996. Bifonazole underwent a photocatalytic degradation process under the experimental conditions used. Comparative studies showed that combination of TiO₂/ZnO (1:1 w /w) was a more effective catalyst than TiO₂ or ZnO with a degradation rate of up to 67.57% after 24 h of irradiation. Further, kinetic analyses indicated that the photocatalytic degradation of bifonazole in the mixture of TiO₂/ZnO can be described by a pseudo‐first order reaction. Statistical comparison clearly indicated that the presence of TiO₂/ZnO also affected the stability of bifonazole from a cream preparation after 15 h of UVA exposure (p < 0.05). Ten photodegradation products of bifonazole were identified for the first time and their plausible fragmentation pathways, derived from MS/MS data, were proposed. The main pathway in the photocatalytic transformation of bifonazole in the presence of ZnO or/and TiO₂ involves hydroxylation of the methanetriyl group and/or adjacent phenyl rings and cleavage of the imidazole moiety.