Gas Chromatography-negative Chemical Ionization Mass Research Articles

Determination of Phenols in Water by Modified Polymer Extraction-Fluorine Derivative Gas Chromatography-Negative Chemical Ionization Mass Spectrometry

Determination of Phenols in Water by Modified Polymer Extraction-Fluorine Derivative Gas Chromatography-Negative Chemical Ionization Mass Spectrometry

Washoff of cypermethrin residues from slabs of external building material surfaces using simulated rainfall

The use of pesticides by homeowners or pest-control operators in urban settings is common, yet contributions of washoff from these materials are not easily understood. In the present study, cypermethrin, formulated as Cynoff EC (emulsifiable concentrate) and Cynoff WP (wettable powder) insecticides, was applied at typical rates to 10 different building material surfaces to examine its washoff potential from each surface. Using an indoor rainfall simulator, a 1-h rainfall event was generated and washoff samples were collected from 3 replicates of each surface type. Washoff was analyzed for cypermethrin using gas chromatography-negative chemical ionization mass spectrometry. An analysis of variance for a split-plot design was performed. Many building materials had similar water runoff masses, but asphalt resulted in significantly reduced average water runoff masses (73% less). The Cynoff WP formulation generally produced greater cypermethrin washoff than the Cynoff EC formulation. In addition, results for both the WP and EC formulations indicated that smoother surfaces such as vinyl and aluminum siding had higher washoff (1.0–14.1% mean percentage of applied mass). Cypermethrin washoff from rough absorptive surfaces like concrete and stucco was lower and ranged from 0.1 to 1.3% and from 0 to 0.2%, respectively, mean percentage of applied mass. Both building material surface and formulation play a significant role in cypermethrin washoff. Environ Toxicol Chem 2014;33:302–307. © 2013 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited.

Determination of polybrominated diphenyl ethers in indoor dust using ultrasonic-assisted extraction and gas chromatography-negative chemical ionization mass spectrometry

A method for the determination of eight polybrominated diphenyl ethers (PBDEs) in indoor dust was developed. A vacuum cleaner was used for gathering the house dust, and n-hexane was added and the extraction was performed in an ultrasonic bath. The supernatant was concentrated and then n-hexane was added to 0.1 mL. Gas chromatography-negative chemical ionization mass spectrometry (GC-NCI/MS) has been investigated for the determination of the eight PBDE congeners in indoor dust. The eight PBDEs were separated within 20 min. The absolute recoveries were 53.2% - 107.6%. The relative standard deviations (RSDs) of intra-day were between 2.8% and 16.5%, while the RSDs of inter-day were between 6.4% and 22.6%. The limits of detection (LOD, S/N = 3) were in the range of 0.003 - 0.015 ng/g except the LOD of BDE-209 was 0.15 ng/g. The results indicated that the proposed method is sensitive, accurate, fast, simple, low solvent consumption and suitable for the determination of tri- to deca-BDEs in indoor dust.

The human body burden of polybrominated diphenyl ethers and their relationships with thyroid hormones in the general population in Northern China

This study was conducted to determine the human body burden of polybrominated diphenyl ethers (PBDEs) and then clarify the relationships between that and the disruption of thyroid hormones in the general population in Northern China. Between November 2010 and May 2011, 124 serum samples were obtained from volunteers from the provinces of Shanxi and Liaoning. Serum samples were prepared by solid-phase extraction and analyzed for BDE-17, 28, 47, 66, 99, 100, 153, 154, 183 and 209 by gas chromatography–negative chemical ionization mass spectrometry. The median concentration of the total PBDEs was 7.2ng/g lipid weights (lw); concentrations ranged from 2.1 to 160.3ng/glw. The PBDE profiles in this study differed from those of other general populations. BDE-209 was the most abundant congener (median, 5.0ng/glw; range, non-detected — 157.1ng/glw), accounting for more than 75% of the total PBDEs, followed by BDE-153. The total PBDE concentrations in men were significantly higher as compared to women. The donors' age was correlated with a few PBDE congeners, but was not correlated with the total PBDE concentrations. The overall level of PBDEs in this study was lower than that observed in general populations in Southern China, Europe, and North America. There were apparent correlations between concentrations of several PBDE congeners and thyroid hormones. Triiodothyronine (T3) was correlated with BDE-99 and 209 and inversely correlated with BDE-17, 28, 47, 153, 183, and the summed tri- to hepta-PBDE congeners (∑3–7PBDEs). Thyroid-stimulating hormone (TSH) was correlated with BDE-17, 28, 47, and 183 and inversely correlated with BDE-99. No correlation between free tetraidothyronine (FT4) and PBDEs was observed. Logistic regression analysis results indicated that those with higher levels of BDE-17 or BDE-153 had significantly lower odds of having T3 levels above the normal range compared to those with lower levels of BDE-17 or BDE-153. Association between FT4 and BDE-153 disappeared after controlling for sex and age. However, there was no significant association between TSH and PBDEs. The results of the present study showed that even at a relatively low level, PBDEs might interfere with the thyroid hormone levels in the general population.

Determination of 17 Pyrethroid Pesticides Residues in Peanut and Its Products by Matrix Solid-phase Dispersion-Gel Permeation Chromatography Coupled with Gas Chromatography-Negative Chemical Ionization Mass Spectrometry

A gas chromatography-negative chemical ionization mass spectrometric method was developed for the determination of 17 pyrethroid pesticides residues in peanut and its products.The sample was extracted by matrix solid phase dispersion with C18/florisil(1/2,g/g).The analytes were eluted by ethyl acetate/cyclohexane(1/1,V/V) and then were purified by gel permeation chromatography.Finally,the residues were analyzed by gas chromatography-negative chemical ionization mass spectrometry.The linear range was from 10 to 500 μg/L for permethrin,and from 5 to 500 μg/L for other 16 pyrethroid pesticides with the good correlation coefficients(r≥0.9992).The recoveries at spiked concentrations of 10-500 μg/kg ranged from 72.6% to 102.9%.The limit of detection and quantitation of 17 pyrethroid pesticides were in the range of 0.33-6.58 μg/kg and 1.11-21.93 μg/kg respectively.The proposed method can be applied to the determination of pyrethroid pesticides residues in peanut and its products.

A Two-Component Mass Balance Model for Calibration of Solid-Phase Microextraction Fibers for Pyrethroids in Seawater

Determination of the analyte-specific distribution coefficient between the aqueous and sorbing phases is required for estimation of the aqueous-phase concentration of the analyte of interest using polymeric materials. Poly(dimethylsiloxane)-coated solid-phase microextration (PDMS-SPME) fiber-water partition coefficient (K(f)) values for eight common-use pyrethroids were determined using a two-compartment mass balance model and parameters determined in experimental seawater microcosms. Mass balance, epimerization, and aqueous-phase degradation (i.e., hydrolysis) were characterized using gas chromatography-negative chemical ionization mass spectrometry to facilitate K(f) estimation. Of the eight pyrethroids, only bifenthrin exhibited increasing sorption on the SPME fiber over the entire time-series exposure, indicating that its K(f) value could be estimated through a stable-compound model. The remaining pyrethroids were found to be unstable (half-life of <22 days), underscoring the importance of accounting for degradation in estimating K(f). The two-compartment model explained the experimental time-series data for bifenthrin (R(2) > 0.98) and the remaining unstable pyrethroids (R(2) > 0.7), leading to estimated values of log K(f) between 5.7 and 6.4, after correcting for residual dissolved organic carbon (DOC) in the experimental seawater. These K(f) values can be used to determine freely dissolved pyrethroid concentrations in the pg/L range using PDMS-SPME in fresh or seawater matrices under equilibrium conditions in laboratory or field applications.

The effect of co-occurring polychlorinated biphenyls on quantitation of toxaphene in fish tissue samples by gas chromatography negative ion mass spectrometry

Determinative methods based on gas chromatography-negative chemical ionization mass spectrometry (GC–NCI/MS) provide improved sensitivity and specificity for toxaphene in environmental samples, but are subject to misidentification due to oxygen reaction in the presence of polychlorinated biphenyls (PCBs). The goal of this study was to quantify the impact of co-occurring PCBs in fish tissue samples when utilizing single quadrupole instruments to implement this method. Mixtures of PCB congeners and technical toxaphene, and extracts of fish tissue with varying concentrations of PCBs were analyzed for individual congener and total toxaphene concentrations by GC–NCI/MS. The contribution of co-injected PCB 204 ranged from 23% to 88% of the total peak area for the Cl-9 toxaphene homolog quantitation ion, a contribution that increased as the ratio of technical toxaphene to PCB 204 decreased. PCB interferences in fish tissue extracts, including a standard reference material, were subtracted using a three-step procedure featuring spectral analysis of isotopic patterns for target peaks. Total toxaphene concentrations without PCB subtraction in three fish tissue samples with low, intermediate and high co-occurring PCBs were overestimated by 33, 55 and 745%, respectively, underscoring the need for practical strategies to account for PCB interferences in GC–NCI/MS based protocols. In contrast, no appreciable interference or resulting positive bias in concentrations was observed for quantitation of eight common toxaphene residue congeners.

A multi-residue method for pesticides analysis in green coffee beans using gas chromatography–negative chemical ionization mass spectrometry in selective ion monitoring mode

In this study, a new gas chromatography–mass spectrometry (GC–MS) method, using the very selective negative chemical ionization (NCI) mode, was developed and applied in combination with a modified acetonitrile-based extraction method (QuEChERS) for the analysis of a large number of pesticide residues (51 pesticides, including isomers and degradation products) in green coffee beans. A previously developed integrated sample homogenization and extraction method for both pesticides and mycotoxins analysis was used. An homogeneous slurry of green milled coffee beans and water (ratio 1:4, w/w) was prepared and extracted with acetonitrile/acetic acid (1%), followed by magnesium sulfate addition for phase separation. Aliquots from this extract could be used directly for LC–MS/MS analysis of mycotoxins and LC-amenable pesticides. For GC–MS analysis, a further clean-up was necessary. C18- and PSA-bonded silica were tested as dispersive solid-phase extraction (d-SPE) sorbents, separate and as a mixture, and the best results were obtained using C18-bonded silica. For the optimal sensitivity and selectivity, GC–MS detection in the NCI-selected ion monitoring (SIM) mode had to be used to allow the fast analysis of the difficult coffee bean matrix. The validation was performed by analyzing recovery samples at three different spike concentrations, 10, 20 and 50μgkg−1, with 6 replicates (n=6) at each concentration. Linearity (r2) of calibration curves, estimated instrument and method limits of detection and limits of quantification (LODi, LODm, LOQi and LOQm, respectively), accuracy (as recovery %), precision (as RSD%) and matrix effects (%) were determined for each individual pesticide. From the 51 analytes (42 parent pesticides, 4 isomers and 5 degradation products) determined by GC–MS (NCI-SIM), approximately 76% showed average recoveries between 70–120% and 75% and RSD≤20% at the lowest spike concentration of 10μgkg−1, the target method LOQ. For the spike concentrations of 20 and 50μgkg−1, the recoveries and RSDs were even better. The validated LOQm was 10, 20 and 50μgkg−1 for respectively 33, 3 and 6 of the analytes studied. For five compounds, the European Union method performance requirements for the validation of a quantitative method (average recoveries between 70-120% and repeatability RSD≤20%) were not achieved and 4 problematic pesticides (captan, captafol, folpet and dicofol) could not be detected as their parent compound, but only via their degradation products. Although the matrix effect (matrix-enhanced detector response) was high for all pesticides studied, the matrix interference was minimal, due to the high selectivity obtained with the GC–NCI-MS detection. Matrix-matched calibration for applying the method in routine analysis is recommended for reliable quantitative results.

Development and validation of a chemiluminescent ELISA for simultaneous determination of florfenicol and its metabolite florfenicol amine in chicken muscle

A competitive indirect chemiluminescent enzyme-linked immunosorbent assay (CL-ELISA) for florfenicol (FF) and its major metabolite florfenicol amine (FFA) residues in chicken muscle has been developed and validated according to Commission Decision 2002/657/EC criteria. The IC50 value of the method was 0.153 μg kg−1 for FFA with a cross-reactivity of 74.3% for FF under optimum conditions, in which FFA–F–BSA (FFA–formaldehyde–BSA) and FF–G–OVA (FF–glutaric anhydride–OVA) were used as an immunogen and a coating antigen, respectively. FFA and FF were easily extracted from chicken muscle with a 40:1 ethyl acetate–ammonia mixture, obtaining recoveries of 70.3–100% (FFA) and 71.8–102.0% (FF). Accuracy, precision, selectivity, robustness, limit of detection (LOD), limit of quantification (LOQ) and detection capability (CCβ) of the assay have been assessed during the validation process. LOD values in chicken muscle were 0.353 μg kg−1 for FFA and 0.526 μg kg−1 for FF (10-fold dilution) and 0.453 μg kg−1 for FFA and 0.657 μg kg−1 for FF (100-fold dilution). Furthermore, the CL-ELISA method gave CCβ values of 1.0 μg kg−1 for FFA and FF. Finally, real chicken muscle samples were analyzed with the CL-ELISA method, traditional ELISA and a previously reported gas chromatography-negative chemical ionization mass spectrometry (GC-MS), and results confirmed the utility of this new CL-ELISA for trace determination of FF and FFA, simultaneously.

Sensitive determination of polybrominated diphenyl ethers in environmental water samples with etched stainless steel wire based on solid-phase microextraction prior to gas chromatography-mass spectrometry

Solid-phase microextraction (SPME) is a solvent-free sample pretreatment technique and has attracted great attention in many application fields. The potential of etched stainless steel wire as SPME adsorbent for the enrichment of organic pollutants has been investigated in recent years. The goal of this work was to investigate the feasibility of using etched stainless steel wire as SPME adsorbents to enrich polybrominated diphenyl ethers (PBDEs) at trace levels, which are new typical persistent organic pollutants in the environment. Extraction conditions that maybe influence the extraction efficiency such as extraction time, agitation speed, ionic strength, and desorption conditions were investigated and optimized in detail. The experimental results exhibited the good linear relationship over the range of 1–200 ng L−1, and the precisions were 5.2–9.5% under the optimal conditions. The limits of detection could reach 0.2–0.6 ng L−1. Satisfactory results were obtained when the present method was applied to determine the seven PBDEs in real world water samples with the recoveries over the range of 77–118%. All these results indicated that etched stainless steel wire as SPME adsorbents coupled to gas chromatography-negative chemical ionization mass spectrometry (GC-NCI-MS) was an excellent method for the rapid analysis of PBDEs at trace levels in the environment.

Determination of polybrominated diphenyl ethers and dechloraneplus in fish and fish oil supplements by gel permeation chromatography coupled with gas chromatography-negative chemical ionization mass spectrometry

Polybrominated diphenyl ethers (PBDEs) and dechlorane plus (DP) are two kinds of widely used organic flame retardants, and PBDE and DP residues have been found in both environment and biota. A method for the determination of 8 PBDEs and 2 DPs in fish and fish oil supplements was developed using auto gel permeation chromatography (GPC) coupled with gas chromatography-negative chemical ionization/mass spectrometry (GC-NCI/MS) in the selected ion-monitoring (SIM) mode on a 15 m capillary column. The sample added with BDE-77 and 13C12-BDE-209 as the internal standards was extracted using a Soxhlet extractor, and further purified by auto GPC and a multilayer silica gel column. The sample preparation procedure was optimized, and the characteristic ions and fragmentations of the analytes in NCI/MS were studied. The limits of detection (LODs, S/N = 3) ranged from 2.2 to 39.8 ng/kg. The average recoveries were between 71.1% and 121.4% at two spiked levels of 2 and 20 ng/g for both BDE-209 and DP and 0.2 and 2 ng/g for others with the relative standard deviations between 2.96% and 13.31%. The developed method has been successfully applied in the determination of PBDEs and DPs in several fish and fish oil supplements samples. The total PBDEs found ranged from 2.18 to 15.93 ng/g, and DP was not found. This method was validated to be accurate and sensitive for the trace analysis of PBDEs and DPs in the samples with fat.

Simultaneous determination of 103 pesticide residues in cabbages and apples using programmable temperature vaporizer-based large volume injection by gas chromatography-negative chemical ionization mass spectrometry

A gas chromatography-mass spectrometric (GC-MS) method has been established for the simultaneous determination of 103 pesticide residues in cabbages and apples using programmable temperature vaporizer-based large volume injection (PTV-LVI) and negative chemical ionization (NCI). It was found that much lower detection limits for the investigated pesticides can be obtained. Prior to GC-NCI/MS analysis, the optimized parameters of PTV-LVI were as follows: inlet temperature was set at 45 degrees C, split vent flow rate was 20 mL/min, evaporation time was 1 min and evaporation temperature was set at 60 degrees C. The volume of injection was 10 microL. Co-extractives were removed from the acetonitrile extracts using solid phase extraction with octadecyl (200 mg) and primary secondary amine (100 mg) sorbents. Matrix matched calibration solutions were used for all the analyses. To evaluate performance of the method, validation experiments were carried out in cabbages and apples at two spiking levels (5 and 10 microg/kg). The average recoveries ranged from 58.5% to 113.2%, and the relative standard deviations (RSDs, n = 6) were in the range of 3.3% - 14.5%. The limits of detection (S/N = 3) were less than 5 microg/kg for all the pesticides. The results show that this method is simple, rapid, sensitive and specific. It is appropriate for the simultaneous identification and quantification of the multi-residues in cabbages and apples.

Method optimization to measure polybrominated diphenyl ether (PBDE) concentrations in soils of Bratislava, Slovakia

We modified an analytical method to determine polybrominated diphenyl ethers (PBDEs) in urban soils of Bratislava (Slovakia). Gel permeation chromatography (GPC) introduced as a clean-up step for soil extracts substantially reduced matrix enhancements when PBDEs were measured with gas chromatography–negative chemical ionization–mass spectrometry (GC–NCI–MS). The resulting method proved to be accurate, precise, and showed low detection limits. The sum of 15 PBDE concentrations in surface horizons of Bratislava soils ranged from 87 to 627 pg g −1. PBDE concentrations were mostly higher in surface than deeper horizons probably because of atmospheric deposition and lack of substantial vertical transport. Lower brominated PBDEs undergo more soil–atmosphere exchanges or are more scavenged and transferred with litter fall to the soil organic matter than higher brominated ones as suggested by the correlation between lower brominated PBDEs and soil organic C (C org) concentrations.

11-Nor-Δ 9-tetrahydrocannabinol-9-carboxylic acid ethyl ester (THC-COOEt): Unsuccessful search for a marker of combined cannabis and alcohol consumption

11-Nor-Δ 9-tetrahydrocannabinol-9-carboxylic acid ethyl ester (THC-COOEt) can be presumed to be a mixed metabolite formed during combined consumption of cannabinoids and alcohol. In order to examine this hypothesis, THC-COOEt and its deuterated analogue D 3-THC-COOEt were synthesized as reference substance and internal standard from the corresponding carboxylic acids and diazoethane and methods were developed for the sensitive detection of THC-COOEt in plasma and hair based on gas chromatography–electron impact mass spectrometry after silylation with N-methyl- N-tert-butyldimethylsilyl-trifluoroacetamide and gas chromatography–negative chemical ionization mass spectrometry (GC-NCI-MS) as well as tandem mass spectrometry (GC-NCI-MS-MS) after derivatization with pentafluoropropionyl anhydride. The methods were applied for THC-COOEt determination to plasma samples from 22 drunk driving cases which contained both ethanol (0.30–2.16 mg/g) and THC-COOH (15–252 ng/mL) as well as to 12 hair samples from drug fatalities which were both positive for THC (0.09–2.04 ng/mg) and fatty acid ethyl esters as markers of chronic alcohol abuse (0.70–6.3 ng/mg). In none of these samples THC-COOEt could be found with limits of detection of 0.3 ng/mL in plasma and 2 pg/mg in hair in 11 samples using GC-NCI-MS and 0.2 pg/mg in one sample using GC-NCI-MS. Therefore, the use of this compound as a marker for combined cannabis and alcohol consumption could not be achieved.

Determination of hydroxylated metabolites of polycyclic aromatic hydrocarbons in human hair by gas chromatography–negative chemical ionization mass spectrometry

The study describes the determination of mono-hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs), metabolites of PAHs, in human hair. Twelve selected OH-PAHs from two to four rings, generally determined in urine analysis, were investigated as markers of human exposure to PAHs. Following hydrolysis of hair specimens of 50–300 mg with 1 M NaOH, OH-PAHs were extracted using dichloromethane and submitted to an optimized derivatization with (2S,4R)-N-heptafluorobutyryl-4-heptafluorobutoyloxy-prolyl chloride. Compounds were then analyzed using gas chromatography–negative chemical ionization mass spectrometry (GC–NCIMS). The average inter-day and intra-day variability was 12% and 17%, respectively. The average recovery was 52% and the limits of detection and quantification ranged from 20 and 66 pmol/g for 1-OH-phenanthrene (i.e., 3.9 and 12.8 pg/mg) to 311 and 1030 pmol/g for 2-OH-benzo(c)phenanthrene (i.e., 75.9 and 251 pg/mg). The influence of hair washing with water as decontamination step, and enzymatic treatment (β-glucuronidase) to hydrolyze conjugated derivatives were also tested. The application of the developed method to the analysis of 30 hair specimens (17 from non-smoker and 13 from smoker volunteers) demonstrated inter-individual qualitative and quantitative variations. According to the easiness of hair sampling and based on the extended detection windows provided by hair analysis, this method is proposed as a new promising tool for the assessment of human chronic exposure to PAHs.

Determination of chloramphenicol, thiamphenicol, florfenicol, and florfenicol amine in poultry and porcine muscle and liver by gas chromatography-negative chemical ionization mass spectrometry

A sensitive and reliable method using gas chromatography-negative chemical ionization mass spectrometry (GC-NCI/MS) was developed for the simultaneous determination of chloramphenicol (CAP), thiamphenicol (TAP), florfenicol (FF), and florfenicol amine (FFA) at trace levels in muscle and liver. Before extraction with ethyl acetate, CAP-d5 was added to tissue samples as internal standard. The organic extracts were frozen to remove lipid and further purified by liquid–liquid extraction (LLE) with hexane and solid-phase extraction (SPE) using Oasis HLB cartridges. The target compounds were derivatized with BSTFA+1% TMCS prior to GC-NCI/MS determination in selected ion monitoring mode (SIM). The recovery values ranged from 78.5 to 105.5%, with relative standard deviations (RSD) <17%. The limits of detections (LODs) of 0.1μg/kg for CAP and 0.5μg/kg for TAP, FF, and FFA were obtain. Incurred sample and samples from local market were successfully analyzed using this method.

Orthogonal array optimization of microwave-assisted derivatization for determination of trace amphetamine and methamphetamine using negative chemical ionization gas chromatography–mass spectrometry

An orthogonal array design (OAD) was applied to optimize microwave-assisted derivatization (MAD) for analysis of trace amphetamine (AM) and methamphetamine (MA) by negative chemical ionization gas chromatography–mass spectrometry (NCI GC–MS). The 2,3,4,5,6-pentafluorobenzoyl chloride (PFBC) was used as a derivatization reagent. Experimental factors including solvent, microwave power, and irradiation time at four-levels were studied in 16 trials by OAD 16 (4 4). The significance of these factors was investigated using analysis of variance (ANOVA) and percent contribution (PC). Solvent is statistically demonstrated a chief factor; microwave power and irradiation time are secondary factors. Under the optimum condition, calibration curve of AM is linear over a range from 0.01 to 100 ng mL −1 with correlation coefficient 0.9988, and MA from 0.1 to 1000 ng mL −1 with correlation coefficient 0.9951. The limit of detection (LOD) is 1.20 pg mL −1 for AM and 13.04 pg mL −1 for MA. An applicability of the method was tested by analyzing urine samples from amphetamine-type stimulants (ATS)-abusing suspects. Consequently, the OAD method not only optimizes the MAD condition for determination of trace AM and MA, but identifies the effects of factor solvent, microwave power and irradiation time on the MAD performance.

Determination of phenolic endocrine disrupting chemicals and acidic pharmaceuticals in surface water of the Pearl Rivers in South China by gas chromatography–negative chemical ionization–mass spectrometry

An analytical method for phenolic endocrine disrupting chemicals and acidic pharmaceuticals in river water was developed using gas chromatography mass spectrometry (GC–MS) coupled with negative chemical ionization (NCI) technique, and used for the determination of these compounds in the Pearl Rivers (Liuxi, Zhujiang and Shijing Rivers). Derivatization using pentafluorobenzoyl chloride (PFBOCl) and pentafluorobenzyl bromide (PFBBr) before GC–MS analysis were applied and optimized for phenolic compounds and acidic compounds, respectively. The target compounds were analyzed for river waters from the upstream to downstream of the Pearl Rivers. Phenolic compounds 4- tert-octylphenol (4- t-OP), 4-nonylphenol (4-NP), bisphenol-A (BPA), estrone (E1), estradiol (E2) and triclosan (TCS) were detected at trace or low levels in the water samples from Liuxi River and Zhujiang River. Diethylstilbestrol (DES) was not detected in the Pearl Rivers. The highest concentrations of the phenolic compounds were found in Shijing River, and they were 3150 ng/L for 4- t-OP, 11,300 ng/L for 4-NP, 1040 ng/L for BPA, 79 ng/L for E1, 7.7 ng/L for E2 and 355 ng/L for TCS, respectively. Only a few acidic pharmaceuticals were detected at low concentrations in water from Liuxi River and Zhujiang River, but the highest concentrations for the acidic pharmaceuticals were also found in Shijing River. The highest concentrations detected for clofibric acid, ibuprofen, gemfibrozil, naproxen, mefenamic acid and diclofenac were 17 ng/L, 685 ng/L, 19.8 ng/L, 125 ng/L, 24.6 ng/l and 150 ng/L, respectively. The results suggest Liuxi and Zhujiang Rivers are only slightly contaminated and can be used as drinking water sources, but Shijing River is heavily polluted by the wastewater from nearby towns.

Analysis of aldehydes in excipients used in liquid/semi-solid formulations by gas chromatography–negative chemical ionization mass spectrometry

Monitoring of low-molecular-weight aldehyde levels in excipients used in liquid/semi-solid based capsule (LFC) dosage forms plays a critical role in the development of these pharmaceutical products. A simple, sensitive and specific method based on gas chromatography coupled with mass spectrometry (GC–MS) utilizing an Rtx-5MS capillary column was developed and validated for the detection and quantification of C 1–C 8 aliphatic aldehydes in LFC excipients at sub-μg/g levels. The proposed procedure is based on the derivatization of aldehydes in 10:1 (v/v) acetonitrile:water with O-2,3,4,5,6-(pentafluorobenzyl) hydroxylamine hydrochloride (PFBHA), followed by direct GC analysis of aldehyde-PFBHA-oxime derivatives with negative chemical ionization (NCI) MS detection. The method developed was successfully applied to the analysis of short chain aldehydes in 30 typical LFC excipients. An example case study on the formation and growth of aldehydes in these excipients under accelerated storage conditions is also reported.

Automated analysis of 2-methyl-3-furanthiol and 3-mercaptohexyl acetate at ng L −1 level by headspace solid-phase microextracion with on-fibre derivatisation and gas chromatography–negative chemical ionization mass spectrometric determination

A fast and automated method for the analysis at ng L −1 level of aroma-powerful polyfunctional thiols has been developed and applied to wine. The sample is just poured in a 20 mL vial and its vapour extracted with a poly(dimethylsiloxane)–divinylbenzene (PDMS–DVB) solid-phase microextraction fibre (65 μm thickness) previously exposed to vapours of the reactive (pentafluorobenzyl bromide) and of an alkali (tributylamine). The derivatised compounds are subsequently desorbed in the GC system and determined by negative chemical ionization mass spectrometry. The method is fully automated by using a Combi-Pal autosampler conveniently programmed. The analysis takes 50 min, which contrasts to the long and tedious methods previously proposed. The development of an optimal procedure is constrained by the aggressive character of the reagent (towards the fibre and the chromatographic column), its volatility and the quality of the blanks that can be obtained. Therefore, a critical step was fixing in the fibre a “safe” and repetitive amount of reagent. This was achieved by exposing the fibre (5 min) to the vapours of a water:acetone (9:1) solution containing 200 mg L −1 of reagent. Under these conditions, the extraction-derivatisation of analytes improves with time and temperature, and the best working conditions are dictated by a compromise between sensitivity, speed and chromatographic performance. Although analytes studied were 2-methyl-3-furanthiol, 4-mercapto-4-methyl-2-pentanone, 3-mercaptohexanol, 2-furanmethanethiol and 3-mercaptohexyl acetate, a good analytical performance could be achieved only for these two last compounds. Both of them can be repetitively (10% < RSD < 20%) determined in wine at concentrations below 0.1 ng L −1. Other aspects considered in the method setup were the oxidation of analytes during the process, and the electron-capture detection (ECD) and MS properties of the pentafluorobenzyl derivatives of different polyfunctional thiols.