Development and validation of a multi-residue method for the determination of pesticides in honeybees using acetonitrile-based extraction and gas chromatography–tandem quadrupole mass spectrometry

An optimized analytical method employing gas chromatography–tandem quadrupole mass spectrometry (GC–MS/MS) has been developed for the simultaneous screening of roughly 150 pesticides in honeybees suspected of poisoning by pesticides during field spraying. In this work, a sample preparation approach based on acetonitrile extraction followed by dispersive solid-phase extraction (d-SPE) cleanup was implemented and validated for pesticides in honeybees for the first time. The procedure involved homogenization of a 2 g sample (23 insects on average) with acetonitrile–water mixture followed by salting out with citrate buffer, magnesium sulphate and sodium chloride. An amount of matrix constituents with limited solubility in acetonitrile was reduced in the extract by precipitation at low-temperature (freezing-out cleanup). Hereafter, d-SPE cleanup was carried out using primary secondary amine (PSA), octadecyl (C18) and graphitized carbon black (GCB). This combination of cleanup steps ensured efficient extract purification. Linearity of the calibration curves was studied using matrix-matched standards in the concentration range between 4 and 500 ng mL⁻¹ (equivalent to 10 and 1250 ng g⁻¹), and coefficients of determination (R²) were ≥0.99 for approximately 90% of the targeted compounds. The recovery data were obtained by spiking honeybees samples free of pesticides at three concentration levels of 10, 50, and 500 ng g⁻¹ (approximately 0.9, 4.3, 43.5 ng per bee). At these spiking levels 47, 77 and 92% of the targeted compounds were recovered, respectively. Generally the recoveries were in the range between 70 and 120% with precision values, expressed as relative standard deviation (RSD) ≤ 20%. The expanded uncertainty was estimated following a “top down” empirical model as being 28% on average (coverage factor k = 2, confidence level 95%). Preliminary results from practical application to analysis of real samples are presented. A total of 25 samples of honeybees from suspected pesticides poisoning incidents were analyzed, in which 10 different pesticides were determined.     

Development of a simple extraction and clean-up procedure for determination of organochlorine pesticides in soil using gas chromatography–tandem mass spectrometry

A procedure based on QuEChERS extraction and a simultaneous liquid–liquid partition clean-up was developed. The procedure involved extraction of hydrated soil samples using acetonitrile and clean-up by liquid–liquid partition into n-hexane. The hexane extracts produced were clean and suitable for determination using gas chromatography–tandem mass spectrometry (GC–MS/MS). The method was validated by analysis of soil samples, spiked at five levels between 1 and 200 μg kg⁻¹. The recovery values were generally between 70 and 100% and the relative standard deviation values (%RSDs) were at or below 20%. The procedure was validated for determination of 19 organochlorine (OC) pesticides. These were hexachlorobenzene (HCB), α-HCH, β-HCH, γ-HCH, heptachlor, heptachlor epoxide (trans), aldrin, dieldrin, chlordane (trans), chlordane (cis), oxychlordane, α-endosulfan, β-endosulfan, endosulfan sulfate, endrin, p,p′-DDT, o,p′-DDT, p,p′-DDD and p,p′-DDE. The method achieved low limits of detection (LOD; typically 0.3 μg kg⁻¹) and low limits of quantification (LOQ; typically 1.0 μg kg⁻¹). The method performance was also assessed using five fortified soil samples with different physico-chemical properties and the method performance was consistent for the different types of soil samples. The proposed method was compared with an established procedure based on Soxtec extraction. This comparison was carried out using six soil samples collected from regions of Pakistan with a history of intensive pesticide use. The results of this comparison showed that the two procedures produced results with good agreement. The proposed method produced cleaner extracts and therefore led to lower limits of quantification. The proposed method was less time consuming and safer to use. The six samples tested during this comparison showed that soils from cotton growing regions contained a number of persistent OC residues at relatively low levels (<10 μg kg⁻¹). These residues were α-HCH, γ-HCH, heptachlor, chlordane (trans), p,p′-DDT, o,p′-DDT, p,p′-DDD, p,p′-DDE, β-endosulfan and endosulfan sulfate.     

Development and validation of a pressurized liquid extraction liquid chromatography–tandem mass spectrometry method for perfluorinated compounds determination in fish

This paper describes the development and validation of an analytical methodology to determine eight perfluorinated compounds (PFCs) in edible fish using pressurized liquid extraction (PLE) with water and solid-phase extraction (SPE) with an ion-exchanger as extraction and pre-concentration procedures, followed by liquid chromatography–quadrupole-linear ion trap mass spectrometry (LC–QqLIT–MS). The rapidity and effectiveness of the proposed extraction procedure were compared with those most commonly used to isolate PFCs from fish (ion-pairing and alkaline digestion). The average recoveries of the different fish samples, spiked with the eight PFCs at three levels (the LOQ, 10 and 100 μg kg⁻¹ of each PFC), were always higher than 85% with relative standard deviation (RSD) lower than 17%. A good linearity was established for the eight PFCs in the range from 0.003–0.05 to 100 μg kg⁻¹, with r > 0.9994. The limits of quantification (LOQs) were between 0.003 and 0.05 μg kg⁻¹, which are well below those previously reported for this type of samples. Compared with previous methods, sample preparation time and/or LOQs are reduced. The method demonstrated its successful application for the analysis of different parts of several fish species. Most of the samples tested positive, mainly for perfluoropentanoic acid (PFPA), perfluorobutane sulfonate (PFBS) and perfluorooctanoic acid (PFOA) but other of the eight studied PFCs were also present.     

Development and validation of a multi-residue method for the determination of pesticides in processed fruits and vegetables using liquid chromatography–electrospray ionization tandem mass spectrometry

A sensitive multi-residue analytical method, utilizing ethyl acetate extraction and liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS), has been developed and validated for simultaneous determination of 28 pesticides of different chemical classes (polar organophosphates, carbamates, strobilurines, neonicotinoids, amides, pyrimidines, benzimidazoles, imidazoles and triazoles), and their transformation products, in processed fruit and vegetables. Two precursor-product ion transitions were monitored for each pesticide in selected reaction monitoring (SRM) mode. Linearity (r (2) > or = 0.99) was good over the concentration range 0.5 to 100 microg L(-1) for all the pesticides, and instrumental detection limits ranged from 0.1 to 1 microg L(-1). Mean recovery for fruit and vegetables spiked at 0.010 mg kg(-1) ranged from 65 to 94.4%, and relative standard deviations ranged from 9.0 to 20.0%. When the amount spiked was 0.050 mg kg(-1) recoveries ranged from 72.5 to 90% and relative standard deviations were from 6.1 to 19.0%. Method detection limits were from 0.002 to 0.007 mg kg(-1) for the different food matrices studied. The method was used to monitor pesticide residues in a wide variety of fruits and vegetables.     

On-line solid phase extraction fast liquid chromatography–tandem mass spectrometry for the analysis of bisphenol A and its chlorinated derivatives in water samples

In this study an on-line column-switching fast LC–MS/MS method was developed to analyze bisphenol A (BPA) and its chlorinated derivatives in water. Fast liquid chromatographic separation was performed on a C18 reversed phase column based on fused-core particle technology (2.7 μm particle size) providing analysis times shorter than 3 min and high peak efficiencies. The main benefit of this LC system is that it can easily be hyphenated to a conventional on-line preconcentration device allowing the direct analysis of water samples without any pretreatment at concentrations levels down to 60 ng L⁻¹ and preventing contaminations frequently reported in the analysis of BPA. This on-line SPE fast LC system was coupled to a triple quadrupole mass spectrometer operating in enhanced mass resolution mode (Q1 FWHM = 0.7 Th, Q3 FWHM = 0.1 Th) in order to minimize interferences and chemical noise. This highly sensitive and selective method was successfully employed to analyze BPA and its chlorinated derivatives in water samples.     

Identification and quantification of odorous compounds from adhesives used in food packaging materials by headspace solid phase extraction and headspace solid phase microextraction coupled to gas chromatography–olfactometry–mass spectrometry

Adhesives are often responsible for off-flavors in food in contact with packaging. The aim of this investigation was to identify by GC–O–MS the odorous compounds in five different types of adhesive (hotmelt, vinyl acetate ethylene, starch, polyvinyl acetate and acrylic) used in food packaging. In order to obtain a substantial number of compounds, they were extracted by two complementary extraction methods: HS-SPE and HS-SPME. Fifteen minutes extraction time using PDMS fiber for hotmelt adhesive and DVD/CAR/PDMS fiber for the other adhesives were the best conditions for defining a representative solvent-free adhesive extract using a rapid and simple D-GC–O technique. Thirty-three compounds were identified by GC–O–MS. These include butyric acid, acetic acid, methyl butyrate, 1-butanol and nonanal, which were present in most of the adhesives under study producing cheesy, rancid, sour, medicinal and green aromas, respectively. The concentrations were determined, the most abundant compound being acetic acid with concentrations from 22.9 to 8930 μg g⁻¹ of adhesive.     

Speciation of butyltin compounds in marine sediments with headspace solid phase microextraction and gas chromatography – mass spectrometry

A method for the determination of organotin compounds (monobutyl = MBT, dibutyl = DBT, and tributyltin = TBT) in marine sediments by headspace Solid Phase Microextraction (SPME) has been developed. The analytical procedure involved 1) extraction of TBT, DBT and MBT from sediments with HCl and methanol mixture, 2) in situ derivatization with sodium tetraethylborate and 3) headspace SPME extraction using a fiber coated with poly(dimethylsiloxane). The derivatized organotin compounds were desorbed into the splitless injector and simultaneously analyzed by gas chromatography – mass spectrometry. The analytical method was optimized with respect to derivatization reaction and extraction conditions. The detection limits obtained for MBT, DBT and TBT ranged from 730 to 969 pg/g as Sn dry weight. Linear calibration curves were obtained for all analytes in the range of 30–1000 ng/L as Sn. Analysis of a standard reference sediment (CRM 462) demonstrates the suitability of this method for the determination of butyltin compounds in marine sediments. The application to the determination of TBT, DBT and MBT in a coastal marine sediment is shown.     

Aptamer-functionalized solid phase microextraction–liquid chromatography/tandem mass spectrometry for selective enrichment and determination of thrombin

In this publication, a novel solid phase microextraction (SPME) coating functionalized with a DNA aptamer for selective enrichment of a low abundance protein from diluted human plasma is described. This approach is based on the covalent immobilization of an aptamer ligand on electrospun microfibers made with the hydrophilic polymer poly(acrylonitrile-co-maleic acid) (PANCMA) on stainless steel rods. A plasma protein, human α-thrombin, was employed as a model protein for selective extraction by the developed Apt-SPME probe, and the detection was carried out with liquid chromatography/tandem mass spectrometry (LC–MS/MS). The SPME probe exhibited highly selective capture, good binding capacity, high stability and good repeatability for the extraction of thrombin. The protein selective probe was employed for direct extraction of thrombin from 20-fold diluted human plasma samples without any other purification. The Apt-SPME method coupled with LC–MS/MS provided a good linear dynamic range of 0.5–50 nM in diluted human plasma with a good correlation coefficient (R² = 0.9923), and the detection limit of the proposed method was found to be 0.30 nM. Finally, the Apt-SPME coupled with LC–MS/MS method was successfully utilized for the determination of thrombin in clinical human plasma samples. One shortcoming of the method is its reduced efficiency in undiluted human plasma compared to the standard solution. Nevertheless, this new aptamer affinity-based SPME probe opens up the possibility of selective enrichment of a given targeted protein from complex sample either in vivo or ex vivo.     

Development and validation of a pressurised liquid extraction liquid chromatography–electrospray–tandem mass spectrometry method for β-lactams and sulfonamides in animal feed

This study presents the development and validation of a sensitive and fast (30 min extraction time and 10 min chromatographic run) method for the detection of penicillins, cephalosporins and sulfonamides in animal feed using pressurised liquid extraction and solid phase extraction as extraction and pre-concentration procedures, followed by liquid chromatography–quadrupole-linear ion-trap mass spectrometry. The developed method was validated showing limits of detection ranging from 0.12 (ampicillin) to 3.94 ng/g (amoxicillin), instrumental and analytical linearity coefficients above 0.99 in both standard and matrix-based solutions as well as relative recoveries ranging from 71% (cefoperazone) to 115% (cefazolin). Repeatability of the method was in the range of 1–9% (RSD %), whereas reproducibility ranged from 3% to 13% (RSD %). The developed and validated method was finally applied to the analysis of real feed samples. The results showed 10 out of 18 analytes to be present in at least one sample and all 14 samples to contain at least one analyte. Penicillin V, oxacillin, ceftiofur, cefoperazone, cefalexin, cefazolin, sulfamethoxypyridazine and sulfapyridine were not detected in any of the samples analysed. Considering the ban of antibacterials as growth promoters added in animal feed, this method is capable of detecting the low concentrations that could result from failure to comply with the regulations or on-site contamination.     

Analysis of carbamate pesticides in water samples using single-drop microextraction and gas chromatography–mass spectrometry

Single-drop microextraction (SDME) followed by gas chromatography–mass spectrometry detection was used for the determination of some carbamate pesticides in water samples. The studied pesticides were thiofanox, carbofuran, pirimicarb, methiocarb, carbaryl, propoxur, desmedipham and phenmedipham. Two alternative sample introduction methods have been examined and compared; SDME followed by cool on-column injection (without derivatization) and SDME followed by in-microvial derivatization and splitless injection. Acetic anhydride was used as derivatization reagent. Parameters that affect the derivatization reaction yield and the extraction efficiency of the SDME method were studied and optimized. The analytical performances and possible applications of both approaches were investigated. Relative standard deviations for the studied compounds ranged from 3.2 to 8.3%. The detection limits obtained by the derivatization method were found to be in the range 3–35 ng/L. Using cool on-column injection (without derivatization), the detection limits were between 30 and 80 ng/L.     

High performance liquid chromatography–tandem mass spectrometry for the analysis of 10 pesticides in water: A comparison between membrane-assisted solvent extraction and solid phase extraction

This work describes the application of two sample preparation methods: membrane-assisted solvent extraction (MASE) and solid phase extraction (SPE) in combination with high performance liquid chromatography–tandem mass spectrometry (HPLC–MS–MS) for the determination of 10 pesticides in surface and ground water. Optimal extraction conditions for MASE were 60 min extraction time at 30 °C with a solvent volume of 100 μL toluene. 5 μL of the toluene extract were directly injected in the HPLC–MS–MS system. Concerning SPE, two materials were tested and C18 was superior to Oasis HLB. Complete desorption was ensured by desorbing the SPE (C18) cartridge with 3 mL of an acetonitrile/methanol mixture (1:1). After evaporation, the extract was injected in the analytical system. Analyte breakthrough was not found for the investigated compounds. For both methods, high extraction yields were achieved, in detail 71% (metalaxyl) till 105% (linuron) for MASE and 52% (ethiofencarb) till 77% (prometryne) for SPE (C18). Detection limits were in the low ng/L range for both methods and precision, expressed as the relative standard deviation (RSD) of the peak areas was below 13%. Five real water samples were analyzed applying both extraction methods. The results were in good agreement and standard addition proved that no matrix effects (such as ion suppression) occurred. In this comparison SPE has the potential of larger sensitivity whereas faster analysis and slightly better recoveries were achieved with MASE. MASE shows potential to be a promising alternative to the conventional off-line SPE concerning low to medium polar compounds.     

Development and validation of a comprehensive two-dimensional gas chromatography–mass spectrometry method for the analysis of phytosterol oxidation products in human plasma

Phytosterol oxidation products (POPs) have been suggested to exert adverse biological effects similar to, although less severe than, their cholesterol counterparts. For that reason, their analysis in human plasma is highly relevant. Comprehensive two-dimensional gas chromatography (GC×GC) coupled with time-of-flight mass spectrometry (TOF-MS) has been proven to be an extremely powerful separation technique for the analysis of very low levels of target compounds in complex mixtures including human plasma. Thus, a GC×GC/TOF-MS method was developed and successfully validated for the simultaneous quantification of ten POPs in human plasma. The calibration curves for each compound showed correlation coefficients (R ²) better than 0.99. The detection limits were below 0.1 ng mL⁻¹. The recovery data were between 71.0% and 98.6% (RSDs <10% for all compounds validated). Good results were obtained for within- and between-day repeatability, with most values being below 10%. In addition, non-targeted sterol metabolites were also identified with the method. The concentrations of POPs found in human plasma in the current study are between 0.3 and 4.5 ng mL⁻¹, i.e., 10–100 times lower than the typical values found for cholesterol oxidation products.     

Development of stir-bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry for the analysis of musks in vegetables and amended soils

The aim of this study was to develop a sensitive and environment-friendly method based on stir-bar sorptive extraction (SBSE) followed by thermal desorption–gas chromatography–mass spectrometry (TD–GC–MS) to determine 8 synthetic musks (musk ambrette, musk ketone, celestolide, tonalide, galaxolide, phantolide, traseolide, and cashmeran) in vegetables (lettuce, carrot, and pepper) and amended soil samples. In a first step sorptive extraction was studied both in the headspace (HSSE) and in the immerse mode (SBSE). The best results were obtained in the immersion mode which was further studied. The influence of the main factors: methanol (20%) and NaCl addition (0%), extraction temperature (40 °C) and time (180 min), extraction solvent volume (9 mL) and stirring rate (600 rpm) on the efficiency of SBSE was evaluated by means of experimental designs. In the case of TD, desorption time (10 min), desorption temperature (300 °C), cryo-focusing temperature (−30 °C), vent flow (75 mL/min) and vent pressure (7.2 psi) were studied using both a fractioned factorial design and a central composite design (CCD). The method was validated in terms of apparent recoveries (AR%), method detection limits (MDLs) and precision at two different concentration levels. Although quantification using instrumental calibration rendered odd results in most of the cases, satisfactory recoveries (74–126%) were obtained in the case of matrix-matched calibration approach for all of the analytes and matrices studied at the two concentration levels evaluated. MDLs in the range of 0.01–0.8 ng/g and 0.01–1.1 ng/g were obtained for vegetables and amended soil samples, respectively. RSD values within 1–23% were obtained for all the analytes and matrices. Finally, the method was applied to the determination of musks in vegetable and amended soil samples.     

Development and validation of a liquid chromatography tandem mass spectrometry method for the analysis of β-agonists in animal feed and drinking water

A reproducible, sensitive and selective multiresidue analytical method for seven β-agonists: clenbuterol (CBT), clenpenterol (CPT), ractopamine (RTP), brombuterol (BBT), mabuterol (MBT), mapenterol (MPT), and hydroxymethylclenbuterol (HMCBT) was developed and validated by using liquid chromatography tandem mass spectrometry (LC–MS/MS) in feed and drinking water samples. The validation was achieved according to the criteria laid down in the Commission Decision 2002/657/EC, however it was necessary to use minimum required performance limits (MRPLs) proposed by the Community Reference Laboratories (CRLs) due to the lack of maximum residue limits (MRLs) for β-agonists. By setting up these MRPLs, allows controlling their use in safe mode, since β-agonists are commonly used in veterinary medicine sometime in a fraudulent manner, for increasing the weigh of animals. Values set for both matrices studied are 50 μg/kg for animal feed, and a range from 0.2 to 10 μg/L for drinking water. CCα values calculated were under the MRPLs suggested; for drinking water the lowest value obtained was 0.12 μg/L, and for animal feed 0.87 μg/kg. Values for CCβ were ranged from 0.08 to 0.13 μg/L in drinking water and from 0.5 to 0.92 μg/kg in animal feed samples. The excellence values obtained, allowed us to conclude that the proposed analytical method is capable to control the β-agonists studied in both matrices and that it can be successfully applied and used as a routine method in laboratories of residue analysis of veterinary food control.     

Trace analysis of benzophenone-derived compounds in surface waters and sediments using solid-phase extraction and microwave-assisted extraction followed by gas chromatography–mass spectrometry

This study describes a procedure for determining eight benzophenone-derived compounds in surface waters and sediments. These include the pharmaceutical ketoprofen, its phototransformation products 3-ethylbenzophenone and 3-acetylbenzophenone, and five benzophenone-type ultraviolet (UV) filters. The proposed analytical method involves the pre-concentration of water samples by solid-phase extraction (SPE) and microwave-assisted extraction (MAE) of sediment samples followed by derivatization and analysis by gas chromatography–mass spectrometry. Different parameters were investigated to achieve optimal method performance. Recoveries of 91 to 96 % from water samples were obtained using HLB Oasis SPE cartridges, whereas MAE of sediments (30 min at 150 °C) gave recoveries of 80 to 99 %. Limits of detection were between 0.1 and 1.9 ng L^?1 for water samples and from 0.1 to 1.4 ng g^?1 for sediment samples. The developed method was applied to environmental samples and revealed the presence of UV filters in the majority of the surface waters with up to 690 ng L^?1 of 2-hydroxy-4-methoxybenzophenone. By contrast, ketoprofen (≤2,900 ng L^?1) and its degradation products (≤320 ng L^?1) were found in only two rivers, both receiving wastewater treatment plant effluents. Sediment analysis revealed benzophenone to be present in concentrations up to 650 ng g^?1, whereas concentrations of other compounds were considerably lower (≤32 ng L^?1). For the first time, quantifiable amounts of two ketoprofen transformation products in the aqueous environment are reported.     

Method validation and comparison of acetonitrile and acetone extraction for the analysis of 169 pesticides in soya grain by liquid chromatography–tandem mass spectrometry

An acetonitrile-based extraction method for the analysis of 169 pesticides in soya grain, using liquid chromatography–tandem mass spectrometry (LC–MS/MS) in the positive and negative electrospray ionization (ESI) mode, has been optimized and validated. This method has been compared with our earlier published acetone-based extraction method, as part of a comprehensive study of both extraction methods, in combination with various gas chromatography–(tandem) mass spectrometry [GC–MS(/MS)] and LC–MS/MS techniques, using different detection modes. Linearity of calibration curves, instrument limits of detection (LODs) and matrix effects were evaluated by preparing standards in solvent and in the two soya matrix extracts from acetone and acetonitrile extractions, at seven levels, with six replicate injections per level. Limits of detection were calculated based on practically realized repeatability relative standard deviations (RSDs), rather than based on (extrapolated) signal/noise ratios. Accuracies (as % recoveries), precision (as repeatability of recovery experiments) and method limits of quantification (LOQs) were compared. The acetonitrile method consists of the extraction of a 2-g sample with 20 mL of acetonitrile (containing 1% acetic acid), followed by a partitioning step with magnesium sulphate and a subsequent buffering step with sodium acetate. After mixing an aliquot with methanol, the extract can be injected directly into the LC–MS/MS system, without any cleanup. Cleanup hardly improved selectivity and appeared to have minor changes of the matrix effect, as was earlier noticed for the acetone method. Good linearity of the calibration curves was obtained over the range from 0.1 or 0.25 to 10 ng mL⁻¹, with r² ≥ 0.99. Instrument LOD values generally varied from 0.1 to 0.25 ng mL⁻¹, for both methods. Matrix effects were not significant or negligible for nearly all pesticides. Recoveries were in the range 70–120%, with RSD ≤ 20%. If not, they were still mostly in the 50–70% range, with good precision (RSD ≤ 20%). The method LOQ values were most often 10 μg kg⁻¹ for almost all pesticides, with good repeatability RSDs. Apart from some minor pros and cons, both compared methods are fast, efficient and robust, with good method performances. The two methods were applied successfully in a routine analysis environment, during surveys in 2007 and 2008.     

Analysis of polysulfides in drinking water distribution systems using headspace solid-phase microextraction and gas chromatography–mass spectrometry

Sulfide and polysulfides are strong nucleophiles and reducing agents that participate in many environmentally significant processes such as the formation of sulfide minerals and volatile organic sulfur compounds. Their presence in drinking water distribution systems are of particular concern and need to be assessed, since these species consume disinfectants and dissolved oxygen, react with metal ions to produce insoluble metal sulfides, and cause taste and odour problems. The analysis of sulfide and polysulfides in drinking water distribution systems is challenging due to their low concentrations, thermal instability and their susceptibility to undergo oxidation and disproportionation reactions. This paper reports on the development and optimisation of a rapid, simple, and sensitive method for the determination of sulfide and polysulfides in drinking water distribution systems. The method uses methyl iodide to derivatise sulfide and polysulfides into their corresponding dimethyl(poly)sulfides, which are then extracted using solid-phase microextraction in the headspace mode and analysed by gas chromatography–mass spectrometry. Good sensitivity was achieved for the analysis of dimethyl(poly)sulfides, with detection limits ranging from 50 to 240 ng L⁻¹. The method also demonstrated good precision (repeatability: 3–7%) and good linearity over two orders of magnitude. Matrix effects from raw drinking water containing organic carbon (3.8 mg L⁻¹) and from sediment material from a drinking water distribution system were shown to have no interferences in the analysis of dimethyl(poly)sulfides. The method provides a rapid, robust, and reliable mean to analyse trace levels of sulfides and polysulfides in aqueous systems. The new method described here is more accessible and user-friendly than methods based on closed-loop stripping analysis, which have been traditionally used for the analysis of these compounds. The optimised method was used to analyse samples collected from various locations in a drinking water distribution system. Some of the samples were shown to contain inorganic polysulfides, and their presence was associated with high sediment density in the system and the absence of disinfectant residual in the bulk water.     

Determination of trace amounts of chlorobenzenes in water using membrane-supported headspace single-drop microextraction and gas chromatography–mass spectrometry

A novel method based on the coupling of membrane-supported headspace single-drop microextraction with gas chromatography?mass spectrometry (GC–MS) is developed for the determination of chlorobenzenes in water samples. For the determination of five chlorobenzenes, a 15 μL toluene microdrop was placed inside the plastic membrane and exposed for 10 min for headspace extraction while stirring at 1000 rpm. The microdrop was then picked up by a microsyringe and directly injected into the injector block of the GC–MS instrument. Under the optimized operation conditions, the calculated calibration curves gave a high level of linearity for all targets with correlation coefficients range from 0.9945 to 0.9987. The limits of detection range from 0.01 to 0.05 μg/L and the RSDs for most of chlorobenzenes were below 7%. The method is simple, sensitive, and stable for single drop microextraction. Its applicability is demonstrated by the determination of chlorobenzenes in tap water samples.     

Development and validation of a solid-phase extraction gas chromatography–mass spectrometry method for the simultaneous quantification of methadone, heroin, cocaine and metabolites in sweat

A sensitive and specific method is presented to simultaneously quantify methadone, heroin, cocaine and metabolites in sweat. Drugs were eluted from sweat patches with sodium acetate buffer, followed by SPE and quantification by GC/MS with electron impact ionization and selected ion monitoring. Daily calibration for anhydroecgonine methyl ester, ecgonine methyl ester, cocaine, benzoylecgonine (BE), codeine, morphine, 6-acetylcodeine, 6-acetylmorphine (6AM), heroin (5-1000 ng/patch) and methadone (10-1000 ng/patch) achieved determination coefficients of >0.995, and calibrators quantified to within +/-20% of the target concentrations. Extended calibration curves (1000-10,000 ng/patch) were constructed for methadone, cocaine, BE and 6AM by modifying injection techniques. Within (N = 5) and between-run (N = 20) imprecisions were calculated at six control levels across the dynamic ranges with coefficients of variation of <6.5%. Accuracies at these concentrations were +/-11.9% of target. Heroin hydrolysis during specimen processing was <11%. This novel assay offers effective monitoring of drug exposure during drug treatment, workplace and criminal justice monitoring programs.     

Determination of multiclass pesticides in river sediments via matrix solid-phase dispersion extraction and gas chromatography–tandem mass spectrometry

A fast and environment-friendly analytical method was implemented to determine multiclass pesticides in river sediments. Twenty-three pesticides—organochlorine pesticides, organophosphorus pesticides, and triazines—were extracted via matrix solid-phase dispersion (MSPD) and analyzed by gas chromatography–tandem mass spectrometry (GC–MS/MS). Florisil demonstrated excellent analytes uptake capability as the extractant phase, with suitable selectivity for treating complex sediment samples. Under defined extraction conditions, the MSPD–GC–MS/MS method demonstrated robustness in the n inter-day analysis of sediments from different sources, providing limit of quantifications (LOQs) between 5 and 15 ng/g, linear responses in the range between LOQs and 150 ng/g, extraction recoveries of 71%–106%, and precision, assessed as relative standard deviation below 20%. The MSPD significantly reduced samples and solvents’ consumption, providing critical environmental gains compared to traditional extraction methods like Soxhlet. Finally, the method was applied to analyze sediment samples from three different collection areas of the Subachoque River (Cundinamarca, Colombia), demonstrating a fast, efficient, confident, and profitable analytical tool for pollution control and monitoring in environmental samples. The method allowed us to determine the current use in Colombia of banned pesticides under the 2001 Stockholm Convention.