Solid-phase Extraction Gas Chromatography Research Articles

Synthesis of a novel isotopically labelled standard for quantification of γ-nonalactone in New Zealand Pinot noir via SIDA-SPE-GC–MS

γ-Nonalactone is a linear aliphatic lactone ubiquitous in wine, associated with coconut, sweet, and stone fruit aroma descriptors. Little research has been conducted looking at the importance of this compound to New Zealand (NZ) wine aroma. 2H213C2-γ-Nonalactone, a novel isotopologue of γ-nonalactone, was synthesised in this work for use in a stable isotope dilution assay (SIDA) for quantification of γ-nonalactone in NZ Pinot noir wines for the first time. Synthesis was carried out using heptaldehyde as the starting material, and 13C atoms and 2H atoms were introduced via Wittig olefination and deuterogenation steps, respectively. The suitability of this compound as an internal standard was demonstrated by spiking model wine at normal and elevated conditions during sample preparation, with subsequent analysis via mass spectrometry showing stability of 2H213C2-γ-nonalactone. A model wine calibration, with concentrations of γ-nonalactone from 0 to 100 µg L−1, was shown to have excellent linearity (R2 > 0.99), reproducibility (0.72%), and repeatability (0.38%). Twelve NZ Pinot noir wines, representative of a range of NZ Pinot noir–producing regions, prices, and vintages, were analysed by solid-phase extraction–gas chromatography–mass spectrometry (SPE-GC–MS). The concentrations of γ-nonalactone ranged from 8.3 to 22.5 µg L−1, the latter of which was close to the odour detection threshold of this compound. These findings provide a basis for further research into γ-nonalactone and its impact on NZ Pinot noir aroma and provide a robust method for the quantification of this compound in Pinot noir.Graphical abstract

Determination of four fatty acid ethyl esters in olive oil by solid phase extraction-gas chromatography

The fatty acid ethyl ester (FAEE) content of olive oil is an important indicator of its quality. At present, the international standard method used to detect FAEEs in olive oil is silica gel (Si) column chromatography-gas chromatography (GC); however, this technique presents a number of disadvantages, including complex operation, long analysis times, and high reagent consumption. In this study, a method based on Si solid phase extraction (SPE)-GC was established to determine four FAEEs in olive oil, namely, ethyl palmitate, ethyl linoleate, ethyl oleate, and ethyl stearate. First, the effects of the carrier gas were investigated, and He gas was ultimately selected as the carrier gas. Next, several internal standards were screened, and ethyl heptadecenoate (cis-10) was determined as the optimal internal standard. The SPE conditions were also optimized, and the effects of different brands of Si SPE columns on the recoveries of analytes were compared. Finally, a pretreatment method in which 0.05 g of olive oil was extracted with n-hexane and purified through a Si SPE column (1 g/6 mL) was developed. A sample could be processed within approximately 2 h using a total reagent volume of about 23 mL. Validation of the optimized method revealed that the four FAEEs have good linearities within the range of 0.1-5.0 mg/L (coefficients of determination (R2)>0.999). The limits of detection (LODs) of the method were within 0.78-1.11 mg/kg, and its limits of quantification (LOQs) were in the range of 2.35-3.33 mg/kg. The recoveries ranged from 93.8% to 104.0% at all spiked levels tested (4, 8, and 20 mg/kg), and the relative standard deviations were 2.2%-7.6%. Fifteen olive oil samples were tested using the established method, and the total FAEEs of three extra-virgin olive oil samples were found to exceed 35 mg/kg. Compared with the international standard method, the proposed method has the advantages of simpler pretreatment process, shorter operation time, lower reagent consumption and detection cost, high precision, and good accuracy. The findings provide an effective theoretical and practical reference for improving olive oil detection standards.

An automated micro solid phase extraction gas chromatography–mass spectrometry (μSPE-GC–MS) detection method for geosmin and 2-methylisoborneol in drinking water

Geosmin and 2-methylisoborneol (2-MIB) are amongst the most common earthy and musty taste and odour (T&O) compounds found in drinking water. With low odour threshold detection limits below 10 ng L−1, and the complexity of raw water matrices, these two compounds provide a significant challenge for water companies globally. In this research, for the first time, a novel and fully automated micro-solid phase-extraction (μSPE) method coupled with gas chromatography (GC)–mass spectrometry (MS) has been developed for the detection of geosmin and 2-MIB for drinking water analysis. The new automated method described herein is environmentally friendly requiring low raw water sample volumes, of 25 mL, and only 50 μL of elution solvent. Our μSPE-GC–MS method exhibits excellent linearity for both compounds (R2 > 0.999) and low limits of detection of 2.0 ng L−1 and 4.3 ng L−1 for geosmin and 2-MIB, respectively. The method showed excellent recovery rates (95.1–100.1%) and good precision (RSD < 7%) in raw sample matrices. Our approach is fully automated onto a robotic workstation which can be readily integrated into a laboratory workflow for routine water analysis. Furthermore, the method has excellent potential to be incorporated within a portable system for onsite analysis.

Could the high incidence of breast cancers in Nigerian women be related to 1,4-Dioxane in skin lightening products?

Two monstrous female health-related issues are currently engaging the attention of the global community. These are the chemical skin-lightening issue and the rising female breast cancer issue. Nigeria has the highest prevalence of chemical skin lightening practice with 77.3% of traders in Lagos using such products and one of the highest incidences of breast cancer globally of 50.5 per 100,000 women. 1,4-Dioxane, a possible contaminant in toiletries and cosmetics, is an IARC group 2B carcinogen and a potential breast carcinogen. It is generated when ethylene oxide -a known breast carcinogen is added to other chemicals during manufacturing. The skin lightening procedure is most conducive for optimal per-cutaneous absorption and inhalation of Dioxane. The research question entertained was if there is a link in the increasing prevalence of skin lightening practice and the rising breast cancer burden in Nigeria. One hundred skin lightening products procured from across Lagos, Nigeria had their listed contents scrutinized and entered onto a spreadsheet, then they were analyzed for Dioxane using Scalia’s Solid Phase Extraction gas chromatography procedure. Water (Aqua) 66%, Glycerin 60% and Tocopherol or Vitamin E 41% were found to be the most listed ingredients on the package labels, with Vitamin C 28%, Kojic acid 26%, Citric acid 22% and Carrot oil seen in 20% of products. All the analyzed samples were negative for Dioxane. The study brought to the fore the need to explore other potential breast carcinogens in skin lightening cosmetics and environmental chemicals.

Establishment and application of quantitative method for 22 organic acids in honey based on SPE-GC–MS

Honey, a natural healthy liquid bee product, is rich in amino acids, vitamins, and other essential nutrients. Different origin honeys also varied in organic acids. The objective of this study is to establish an efficient solid-phase extraction-gas chromatography–mass spectrometry (SPE-GC–MS) method to eliminate interference of sugar and other impurities for accurately estimating 22 organic acids in honey by optimizing extraction, purification, derivatization, and gas chromatography–mass spectrometry (GC–MS) analytical conditions. After being extracted, purified and derivatized, organic acids in honey were qualified and quantified by GC–MS. This method was evaluated experimentally, and the results showed that, within a certain concentration range, the standard curve linear relationship was satisfactory (R2 > 0.9942), and the target organic acid recovery rate was 86.74% ~ 118.68%. Besides, precision (relative standard deviation, RSD = 2.98% ~ 13.42%), detection limit (LOD = 0.002 ~ 0.2 mg kg−1), and quantification limit (LOQ = 0.008 ~ 0.5 mg kg−1) met the target requirements. Also, based on this analytical method, the organic acids in five types of honey (acacia, jujube, vitex, canola and linden honey) were estimated. Notably, they all contained 22 different kinds of organic acids, and significant differences (p < 0.05) in the organic acid content and composition among different honey varieties were observed. PCA analysis showed that the five honeys could be differentiated based on the content of 22 organic acids.

Simultaneous Analysis of Free/Combined Phytosterols in Rapeseed and Their Dynamic Changes during Microwave Pretreatment and Oil Processing

Here, a simple, efficient, and rapid solid phase extraction-gas chromatography (SPE–GC) method was developed for the simultaneous analysis of free/combined phytosterols in rapeseed and their dynamic changes during microwave pretreatment and oil processing. First, by comparing different methods for extracting free/combined phytosterols from rapeseed and rapeseed cake, the Folch method was considered to be the optimal method and was selected in subsequent experiments. Subsequently, the extraction method was validated by determining the recoveries of standards (brassinosterol, campesterol, β-sitosterol and cholesteryl oleate) spiked in rapeseed and rapeseed oil samples, and the recoveries were in the range from 82.7% to 104.5% and 83.8% to 116.3%, respectively. The established method was applied to study the dynamic changes of the form and content of phytosterols in rapeseed and its products (rapeseed oil and cake) during rapeseed microwave pretreatment and the oil production process. Additionally, the results showed that more than 55% of the free/combined phytosterols in rapeseed were transferred to rapeseed oil during the oil processing, and this proportion will increase after microwave pretreatment of rapeseed. This work will provide analytical methods and data support for a comprehensive understanding of phytosterols in rapeseed and its products during oil processing.

Determination of chlorobenzene metabolite-p-chlorophenol in urine by solid phase extraction-gas chromatography

Objective: A method to determine chlorobenzene metabolite-p-chlorophenol in urine by solid phase extraction-gas chromatography was established. Methods: In May 2021, the urine sample was hydrolyzed at 100 ℃ for 1.5 h with 2 ml concentrated hydrochloric acid. After cooling and filtering, the sample was enriched and purified by Oasis(®)MAX 6cc SPE column. Drip washing with 0.01 mol/L hydrochloric acid solution and elution with acetonitrile, the eluent was volumized to 5 ml with acetonitrile and determined by gas chromatography, and quantify by standard curve method. Results: Calibration curve of the method was linear within the range of 1.61-80.30 μg/ml and showed good linearity with r=0.9997, the regression equation was y=1.51602x-0.10234. The determination limit was 0.17 μg/ml, and the limit of quantitation was 0.55 μg/ml. Recovery rates were between 89.3%-104.4%, the relative standard deviation (RSD) of intra-day measurements ranged from 4.3% to 6.7%, and the RSD of inter-day measurements ranged from 4.5% to 6.7%. Conclusion: This method could optimize sample pretreatment, and eliminate the interference of impurities, which is sensitive, efficient and accurate for the determination of chlorobenzene metabolite-p-chlorophenol in urine.

Simultaneous determination of 10 N-nitrosamines in drinking water by tandem solid phase extraction-gas chromatography tandem mass spectrometry

Simultaneous determination of 10 N-nitrosamines in drinking water by tandem solid phase extraction-gas chromatography tandem mass spectrometry

Curcumin-loaded magnetic chitosan-based solid-phase extraction-gas chromatography of migrated phthalate esters from pacifiers and plastic toys into baby saliva

The aim of this study was to investigate the presence of phthalate esters in the saliva of babies who use pacifiers or plastic toys mouthed by them. For this purpose, magnetic micro solid-phase extraction coupled with gas chromatography equipped with a flame ionization detector (GC–FID) was developed. The solid sorbent, curcumin loaded magnetic chitosan (CUR-MCH), successfully synthesized and characterized by FT-IR, FESEM, TEM and VSM. Parameters affecting the extraction efficiency are monitored and optimized through the univariate analysis and experimental design. Under optimum conditions, method presented good linearity [in the range 0.001–5 µg mL−1 for dimethyl phthalate (DMP), din-butyl phthalate (DBP), benzyl butyl phthalate (BBP) and di(2-ethylhexyl) (DEHP)] with coefficient of determination (R2) from 0.9823 to 0.9935 and enrichment factors from 38 to 50. The applicability of the method was examined using real samples from baby's saliva. Saliva samples are collected, extraction procedure performed on them, resultant of extraction injected to GC for separation and quantification of phthalate esters. The results of this study showed that baby accessories made of soft PVC emit phthalate species and contaminate baby's saliva. Among the phthalate species studied, DBP and DEHP are released from polymers more than other species and enter saliva and then the baby's body. Probably more of these two species have been used in the production of these products. Of course, the child's age and ability to chew plastic also play a role.

Magnetic polyimide nanosheet microspheres for trace analysis of estrogens in aqueous samples by magnetic solid-phase extraction-gas chromatography–mass spectrometry

Magnetic polyimide nanosheet microspheres (PI-NMs) were used for magnetic solid-phase extraction (MSPE) for the first time. The PI-NMs were modified with magnetic Fe3O4 nanoparticles by chemical coprecipitation to produce the PI-NM/Fe3O4 composite. The prepared composite possessed a nanosheet structure, large specific surface area (71.5 m2/g), high saturation magnetization (19.1 emu/g), large adsorption capacity (≥ 676 ng/mg for selected estrogens), and good extraction stability (> 10 times). Trace estrogens in environmental water and urine samples were extracted by the PI-NM/Fe3O4 composite, desorbed, derivatized, and analyzed by gas chromatography–mass spectrometry (GC-MS). The derivatization, extraction, and desorption conditions were optimized. Extraction equilibrium was achieved within 1 min due to the good dispersibility and large specific surface area of the PI-NM/Fe3O4 composite. Under the optimized conditions, the MSPE/GC–MS method validation results showed wide linearity (0.02–50 µg/L or 0.05–50 µg/L), high determination coefficients (R2 ≥ 0.9983), good intraday and interday precisions (expressed as relative standard deviation, RSDs ≤ 8.2%), and low limits of detection (LODs, 0.001–0.015 µg/L). For the real environmental water and urine samples, the recoveries and RSDs were 77.0–112.5% and 0.1–10.7%, respectively. The performance of the MSPE/GC–MS method proved that the PI-NM/Fe3O4 composite was a good alternative material for the extraction of organic pollutants in aqueous samples.

A sensitive, robust method for determining natural and synthetic hormones in surface and wastewaters by continuous solid-phase extraction–gas chromatography–mass spectrometry

Over recent decades, steroidal estrogens have become an emerging and very serious issue as they pose a serious threat to living organisms, soil, plants, and water resources in general. Estrogens have therefore been the subject of considerable scientific attention in order to develop new methodologies for its determination, being able of detecting them at very low concentrations. Those procedures minimize or eliminate the consumption of organic solvents and reagents that may be incompatible with the environment. In this respect, we developed a sensitive, selective method for the simultaneous determination of thirteen natural and synthetic hormones present at the nanogram-per-liter level in various types of water by using continuous solid-phase extraction in combination with gas chromatography and mass spectrometry (GC–MS). The target analytes were preferentially sorbed on an Oasis HLB sorbent column (80 mg) and eluted with acetone (600 µL) for derivatization with a mixture of 70 µL of N,O-bis(trimethylsilyl) trifluoroacetamide and trimethylchlorosilane and 35 µL of petroleum ether in a household microwave oven at 200 W for 4 min. Under optimum conditions, the ensuing method exhibited good linearity (r ≥ 0.998), good precision (RSD ≤ 7%), high recoveries (92–103%), and low detection limits (0.01–0.3 ng L−1). The method outperforms existing alternatives in robustness, sensitivity, throughput, flexibility—it allows both estrogens, progestogens, and androgens to be determined simultaneously—and compliance with the principles of Green Chemistry. It was successfully used to analyze various types of water samples (mineral, tap, well, pond, swimming pool, river, and waste) that were found to contain four estrogens (estrone, 17β-estradiol, 17α-ethinylestradiol, and hexestrol), two progestogens (testosterone, dihydrotestosterone), and one progestogen (progesterone) at concentrations ranging from 3.0 to 110 ng L−1.

Analysis of Varietal Thiols in Sauvignon Blanc Wines—Optimization of a Solid-Phase Extraction Gas Chromatography Tandem Mass Spectrometry Method

Analysis of Varietal Thiols in Sauvignon Blanc Wines—Optimization of a Solid-Phase Extraction Gas Chromatography Tandem Mass Spectrometry Method

Removal of organic pollutants by effluent recirculation constructed wetlands system treating landfill leachate

The leachate of municipal solid waste landfills contains various types of organic substances, increasing the difficulty of efficient treatment. This study built an effluent recirculation (1:4 ratios) vertical subsurface flow constructed wetlands (CWs) system treating actual landfill leachate (LL). In order to better monitor and evaluate the removal of organic pollutants in LL by CWs, Three-Dimensional Fluorescence (3D-EEM) and Solid Phase Extraction–Gas Chromatography–Mass Spectrometry (SPE–GC–MS) analysis of CWs influent and effluent water was performed to investigate the removal of Dissolved organic matter (DOM), Organochlorine pesticides (OCPs), Organophosphorus pesticide (OPPs), Polycyclic aromatic hydrocarbons (PAHs), and Volatile organic compounds (VOCs). Results showed that during the treatment of LL by CWs, the average removal rate of conventional pollutants (COD, NH4+-N and TP) was over 85%, with a majority of microbial metabolites and humic acids in DOM effectively degraded. The concentrations of OCPs, OPPs, PAHs, and VOCs in the CWs influent LL ranged between 378.6 and 4746.32 ng L−1, accounting for only a small proportion (3.7×10−7–4.6×10−6) of COD. The achieved organic micro-pollutants total removal rates were: OCPs(56.9%), OPPs(41.4%), PAHs(58.3%), and VOCs(78.3%), with relatively higher removal rates observed for DDT (83.6%), dimethoate (89.2%), benzo(a)anthracene (82.0%). Therefore, the effluent recirculation CWs system can effectively remove organic pollutants in LL, indicating that this is a promising technology with good application for the effective treatment of wastewater.

Agricultural pesticide residues in water from a karstic aquifer in Yucatan, Mexico, pose a risk to children’s health

ABSTRACT Yucatan is a region with a high impact of water contamination since it has a karst type soil favoring contaminants entry into the phreatic level, the only source of freshwater in the area. However, no studies report pesticides in water for human consumption or the risk it represents. The objective of this study was to detect and measure pesticide concentrations in domestic tap water to estimate the risk (carcinogenic and non-carcinogenic) to health. A non-probabilistic sampling was applied of 48 tap water sources, and then pesticide detection with solid-phase extraction gas chromatography coupled to the electron capture and flame photometric detectors allowed the estimation of risk through hazard ratios. The present results suggest that aldrin, heptachlor, and β-BHC residues in domestic tap water from Ticul, Yucatan, pose a risk to children’s health, particularly for potential carcinogenic risks.

Migration of mineral oil hydrocarbons from food contact papers into food simulants and extraction from their raw materials

ABSTRACT To determine the occurrence of mineral oil hydrocarbons (MOH) in food contact papers in China, and to investigate the potential sources of MOH contamination, a total of 159 food contact papers and raw materials were analysed by off-line solid-phase extraction-gas chromatography flame ionisation detection (SPE-GC-FID) and a GC-MS method. The migration of MOH from food contact papers into Tenax, olive oil or 50% ethanol under the worst foreseeable conditions of use was determined. The results indicated that the occurrence of MOH in China is of a potential health risk concerning the migration of mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH) which were detected in 82.6% and 50.4% of samples, respectively. Migration of MOSH from 47.9% of samples was higher than 2 mg/kg and migration of MOAH from 32.2% samples exceeded 0.5 mg/kg in case of the worst foreseeable condition of use. The highest mean migration of MOSH and MOAH were found in packaging papers for long-term storage (more than 6 months), with mean migration of 91.2 mg/kg and 1.4 mg/kg, respectively. Migration of MOH from printed paper was considerably higher than that of unprinted paper, validating previous findings that the printing ink is the predominant source of MOH contamination in food contact papers. Migration of MOH from paper bowls used for packing instant noodles was relatively low, suggesting the internal hollow layer may be acting as a functional barrier that could block the transfer of MOH (up to C28) through the gas phrase, even though the outer layer was made from recycled paper. High concentrations of MOSH and MOAH were also detected in de-foamers, adhesives and rosin sizing agents, indicating that the MOH contamination caused by the use of raw materials and additives should also be taken into consideration.

Characteristic polycyclic aromatic hydrocarbons and their sources in surface water in North China

Sixteen priority polycyclic aromatic hydrocarbons (PAHs) in nine typical surface water sources in North China have been analyzed by solid phase extraction-gas chromatography tandem triple four-stage mass spectrometry (SPE-GC-MS-MS). The results showed that eleven in sixteen PAHs were detected except BkFL, BaP, InP, BghiP and DBA. The range of total PAHs in spring water body of nine water sources is 23.76-71.47 ng/L, and that is 83.72-277.8 ng/L in summer. The results showed that the seasonal pollution of PAHs was significantly different, and the pollution status of PAHs in summer was significantly higher than that in spring because the non-point source pollutants including PAHs would easily enter surface water sources with rainfall-runoff. The results also showed the PAHs are mainly composed of medium and low cyclic aromatic hydrocarbons (2-3 rings). In addition, the ratios of Ant/(Phe+Ant), Flu/(Pyr+Flu) and BaA/(BaA+Chr) indicate the PAHs pollutants should be mainly from coal and wood burning in the upstream area of these water sources, entering water sources through surface runoff, which is not obviously affected by the pollution of oil leakage and discharge. Generally, the concentration of the PAHs in surface water sources in North China is still lower, but it is suggested that we should pay more attention to PAHs risk assessment for the drinking water sources.

Characterization of segregated greywater from Indian households-part B: emerging contaminants.

Emerging contaminants (ECs) have become an increasing area of concern due to the likely impacts of these compounds on human health and the environment. Generally, products which are used for households and personal care activities contribute to major percentage of ECs in household greywater. Not much information on the presence of xenobiotic organic compounds in greywater is currently available. Therefore, the present study focused on the qualitative and quantitative analyses of emerging contaminants from different classifications of Indian households. The qualitative screening of emerging pollutants by solid-phase extraction-gas chromatography and mass spectroscopy (SPE-GC-MS) showed the presence of 78 different emerging contaminants from three different sources, which are categorized into ten different groups based on their chemical properties. The quantitative analysis of few selected target pollutants such as phthalic esters, namely diethyl hexyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, triclosan, bisphenol A, caffeine, acetaminophen, 3-methyl salicylic acid, 4-octylphenol, and 4-nonylphenol were found to be 0.38 ± 0.39 μg/L, 1.57 ± 1.54 μg/L, 4.77 ± 2.57 μg/L, 0.712 ± 0.17 μg/L, 5.82 ± 1.85 μg/L, 11.08 ± 2.64 μg/L, 2.30 ± 1.19 μg/L 13.18 ± 4.48 μg/L, 3.75 ± 1.90 μg/L, 4.95 ± 2.21 μg/L, and 5.96 μg/L, respectively. Risk assessment indicated that 63 compounds identified in the greywater can be considered priority pollutants. Based on the results obtained in the present study, effective zero-discharge liquid system can be designed for different sources of greywater and it can be recycled and reused without much risk. Graphical abstract .

Occurrence of PAHs in water samples of the Diep River, South Africa

Occurrence of polycyclic aromatic hydrocarbons (PAHs) in freshwater may aggravate the water crisis currently being experienced in the Western Cape Province of South Africa. However, there is dearth of data on the levels of PAHs, which is necessary for effective assessment of water quality as well as remediation strategies. This study therefore assessed levels of PAHs in the Diep River freshwater system of Western Cape Province, South Africa. A liquid-liquid extraction solid-phase extraction gas chromatography flame ionisation detection (LLE-SPE-GC-FID) method was developed to simultaneously determine the 16 United States Environmental Protection Agency (USEPA) listed priority PAHs in water samples. The SPE-GC-FID method allowed an acceptable linearity (R2 &gt; 0.999) within the calibration range of 1 to 50 µg/mL. Instrument detection limits ranged between 0.02 and 0.04 µg/mL and instrument quantification limits between 0.06 and 0.13 µg/mL. Recovery study results were also acceptable (83.69–96.44%) except for naphthalene, which had recovery of 60.05% in spiked water matrix. The seasonal averages of individual PAH detected at the studied sites ranged between not detected (nd) and 72.38 ± 9.58 µg/L in water samples.

Multiresidue determination of polycyclic aromatic hydrocarbons in edible oils by liquid-liquid extraction–solid-phase extraction–gas chromatography–mass spectrometry

The presence of polycyclic aromatic hydrocarbons (PAHs) in edible oils is usually due to environmental contamination, manufacturing processes or the nature of the oil. Because oils constitute a very large family of foodstuffs that are ubiquitous in human diet, the presence of PAHs in them may have a considerable impact. In this work, we developed a method for determining EPA's 16 PAH priority pollutants using liquid–liquid and solid-phase extraction for their extraction and isolation, and gas chromatography–mass spectrometry for their quantification. The proposed method is highly sensitive, with limits of detection from 4 to 110 ng kg−1, accurate (PAH recoveries of 87–104%) and precise (relative standard deviation < 7.5%). Application to various types of oil (olive, sunflower, coconut, soybean and sesame) testified to its flexibility. Most of the samples studied contained more than three PAHs, albeit at concentrations below the legally allowed levels. Only two samples of refined sunflower oil contained no PAH at levels within the sensitivity range of the method.

A sensitive and specific solid-phase extraction-gas chromatography-tandem mass spectrometry method for the determination of 11 haloacetic acids in aqueous samples.

A method for the analysis of 11 haloacetic acids in water samples has been developed. It involves enrichment of the target analytes from water samples by solid-phase extraction, derivatization to methyl esters, and gas chromatography coupled with tandem mass spectrometry determination. Gas chromatography conditions were optimized for a good separation of all haloacetic acids in a short runtime. Data were acquired in the multiple reaction monitoring mode. Six solid-phase extraction sorbents among the most widely used in environmental analysis were tested. Bakerbond SDB was retained because it has been shown to provide the best results for a large class of targeted haloacetic acids. The performances of the developed method have been assessed according to the French Standard NF T 90-210. The calibration curves for all the studied haloacetic acids had consistent slopes with r2 values > 0.99. Quantification limits between 0.01 and 0.50 µg l-1 were achieved. Satisfactory repeatability (relative standard deviation ≤ 14.3%) and intermediate precision (relative standard deviation ≤ 15.7%) were obtained. Applied to the analysis of 15 untreated water samples collected from three rivers, the method allowed the detection of five haloacetic acids including monochloroacetic acid (in 100% of the samples, <0.5-1.85 µg l-1), dichloroacetic acid (87%, <0.05-0.22 µg l-1), trichloroacetic acid (93%, <0.05-0.52 µg l-1), dibromoacetic acid (53%, <0.01-0.40 µg l-1), tribromoacetic acid (20%, <0.05-0.14 µg l-1), and bromodichloroacetic acid (6%, < 0.05 µg l-1).