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1.
A new multiclass/multiresidue method for monitoring plant protectant residues in raw- and drinking waters with on-site sampling using a mobile, self-contained sampling unit based on SPE was developed and validated. 38 active compounds with widely varying chemical and physicochemical properties (acid-base properties, polarities, vapor pressures, solubilities) are measured from just one sample and work-up. 100 mL water, acidified with acetic acid, are drawn through a cartridge filled with Amberchrom resins by means of a calibrated 100 mL syringe driven by servo motors, control circuit and rechargeable battery. Volumetric flow is high, quantitative extraction of acidic, neutral and weak basic substances is accomplished in a few minutes and loaded cartridges are transported into the laboratory. Further work-up, i.e. elution, drying, concentration and solvent change, is designed strictly non-selectively and produces 250 μL of an “extract”, which is the starting point of two GC measurement lines, GC-NPD and GC-ECD. Chlorinated herbicide acids are derivatised into perfluorinated benzyl esters employing reaction conditions so smooth that the organochlorine hydrocarbons are not destroyed at all and both substance classes can be chromatographed in one GC run. ECD-chromatograms from derivatised solutions are rather complex, therefore the flow is split after injection onto two columns with different polarities and two EC-detectors in order to resolve all analytes and matrix interferents. Short-chain carbonic acids added to the water prior to preconcentration are adsorbed on the hydrophobic surface in a reversible process and impart the Amberchrom resins with a partially hydrophilic character. Method performance was ascertained using tap water fortified at the 0.2 μg L–1 level: Mean recoveries were between 70 and 115% and method detection limits (MDLs) below 0.08 μg L–1. Waters from different sources did not affect the recoveries, loaded cartridges are stable for two weeks’ storage when cooled. Received: 28 December 1998 / Revised: 20 April 1999 / Accepted: 13 May 1999  相似文献   

2.
This study assesses how the physical characteristics of styrene-divinylbenzene (PS-DVB) resins affect the extent to which they are modified when they are functionalized, and how they affect recoveries in on-line solid-phase extraction (SPE) of some polar phenolic compounds, pesticides, and metabolites from water samples which were analyzed by liquid chromatography and UV detection. For this purpose, three commercial PS-DVB resins with different physical characteristics (Amberchrom GC-161m and two different PLRP-S resins) were chemically modified by placing a hydrophilic group, an o-carboxybenzoyl moiety, on their surface; although the physical characteristics are different, the extent of modification did not vary significantly. The results from the SPE process with each sorbent were related to their physical and chemical properties. The polymers with higher surface area provided better recoveries. Moreover, the recoveries for these analytes were better with the chemically-modified polymers due to the higher polarity of these sorbents. The best recovery values were with the sorbent obtained from the chemical modification of Amberchrom GC-161m, the commercial sorbent with higher surface area. For instance, in the analysis of 50 mL of a sample of 2 μg L–1, the recovery of phenol was 40% with Amberchrom GC-161m and 65% with the chemically-modified Amberchrom GC-161m.  相似文献   

3.
Optimization of focused microwave (FMW)‐assisted extraction of 4,4′‐DDE, 4,4′‐DDD, and 4,4′‐DDT from soil samples was carried out using central composite designs. All the extracts were analyzed with GC/MS and some of them also with GC/AED using columns of different polarities for each of the techniques. The extraction of the analytes was carried out in two ways: with acetic acid as microwave radiation absorbent solvent and n‐decane to concentrate the analytes and with reagent water and iso‐octane as solvents. In the first case, the influence of the extraction temperature, the extraction time, and the addition of sodium chloride were studied and the optimum conditions for the extraction of 1 g of soil with 5 mL of acetic acid and 2 mL of n‐decane were 1.30 mol L–1 sodium chloride at 98°C for 9.3 min. In the second case, the temperature was kept constant (94°C) and the influence of the concentration of sodium chloride and the extraction time were studied. The optimum conditions were 5 mL of a 2.0 mol L–1 sodium chloride together with 2 mL of iso‐octane for 15 min. The recoveries obtained by water‐FMW extraction were significantly lower than those obtained by the acetic acid‐FMW procedure. These last recoveries were in good agreement with those obtained by closed microwave assisted‐extraction with acetone‐n‐hexane as solvent.  相似文献   

4.
Summary Two procedures, based on large-volume injection with a programmed-temperature vaporizer (PTV), have been developed for the determination of several triazine and organophosphorus pesticides. The use of PTV for injection in gas chromatography (GC) has enabled the introduction of up to 200 μL sample extract into the GC, thus increasing the sensitivity of the method. PTV injection has been combined off-line with two different microextraction procedures—liquid-liquid partition and solid-phase extraction. A simple and rapid off-line liquid-liquid microextraction procedure (5 mL water/1 mL methyltert-butyl ether) was applied to surface water samples spiked at levels between 0.01 and 5μg L−1. Recoveries of the overall procedure were >80% and the precision was better than 15%. Detection limits were <30 ngL−1 from 200-μL injections in GC-NPD analysis of triazines and GC-FPD analysis of organophosphorus pesticides. Off-line automated solid-phase extraction with C18 cartridges has been applied to water samples (50 mL) spiked at 0.01, 0.1 and 1 μg L−1. The overall procedure was satisfactory (recoveries >80% and coefficients of variation <12%) and the limits of detection ranged from 1 to 9 ng L−1. Finally, several surface water samples were anlysed, and triazine herbicides were detected at concentrations of approx. 0.1–0.2 μg L−1. The results were similar to those obtained by conventional solvent extraction then GC-MSD after splitless injection of 2 μL.  相似文献   

5.
In this paper, a procedure for the determination of 11 aromatic hydrocarbon-type sensitisers and their related compounds from water samples, used in the manufacture of thermal paper, is presented. The compounds were extracted using a solid-phase extraction (SPE) cartridge with an octadecyl (C18) or a phenyl-bonded silica (PH) sorbent and then determined by gas chromatography–mass spectrometry (GC–MS). Factors affecting the performance of the extraction steps were thoroughly evaluated, and their effects on the yield of the sample preparation were discussed. Under optimised experimental conditions, SPE cartridges were conditioned with 10?mL hexane followed subsequently by 10?mL methanol, loaded with water sample at 2?mL?min?1, and eluted with 10?mL hexane at 1.5?mL?min?1. The limits of detection and quantification, calculated for signal-to-noise ratios of 3 and 10, were in the range of 1–5?µg?L–1 and 2.5–10?µg?L–1, respectively. Recovery yields of the present method using river water were in the range of 88%–112% with a C18 sorbent and 86%–116% with a PH sorbent. The repeatability, expressed as a relative standard deviation, was in the range of 2.8%–11% with a C18 sorbent and 0.7%–9.7% with a PH sorbent (n?=?4). Analysis of paper mill effluents revealed the presence of aromatic hydrocarbon-type sensitisers with maximum concentrations of up to 5.2?µg?L?1.  相似文献   

6.
An on-line flow injection preconcentration-ETAAS method is developed for trace determination of cobalt in biological materials and natural samples by ion-pair sorption on the inner walls of a PTFE knotted reactor. The ion-pair is formed between the negatively charged cobalt-nitroso-R-salt complex and the tetrabutylammonium counter-ion. An enhancement factor of 15, a sampling frequency of 17 and a concentration efficiency of 4 are obtained for a preconcentration time of 60 s and a sample loading flow rate of 5 mL min–1. The detection limit (3σ) is 5 ng L–1. The relative standard deviation at the 0.2 μg L–1 level is 2.3%. The analytical results obtained for standard reference materials are in good agreement with the certified or indicated values and satisfactory recoveries of spiked cobalt in tap water are obtained.  相似文献   

7.
A method based on solid phase extraction was developed for the determination of the herbicide triallate and its metabolite 2,3,3-trichloro-prop-2-en-sulfonic acid (TCPSA). Soil samples were extracted with methanol and diluted with water to yield a methanol/water ratio of 1?:?4. Triallate was adsorbed on C18 cartridges while TCPSA was enriched on quaternary amine anion exchange resins. Cartridges were eluted with methanol/ethyl acetate and methanol/sulfuric acid mixture, respectively. TCPSA methyl ester was formed using trimethyl orthoformate and subsequently analyzed by GC/ECD. Determination limits of both target compounds were 5 μg/kg soil with recoveries of 100 ± 12% for triallate and 57 ± 5% for TCPSA. In water analysis, determination limits were 0.05 μg/L with recoveries of 84 ± 14% for triallate and 100 ± 22% for TCPSA. In laboratory batch experiments, concentration of triallate decreased from 2690 to 1550 μg/kg soil within 59 days. 14 days after triallate application, TCPSA was determined to be 14 μg/kg which increased to 98 μg/kg soil at the end of the incubation period. Soil/water distribution coefficients in loamy sand soil were 102 for triallate and 0.02 for TCPSA which indicated a higher leaching tendency of the polar metabolite.  相似文献   

8.
In the present work, a minicolumn of XAD-4 loaded with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (Br-PADAP) is proposed as a preconcentration system for uranium determination in well, tap and mineral water samples by spectrophotometer using arsenazo III as the chromogenic reagent. Initially, a two-level (23) full factorial design was used for the preliminary evaluation of three factors, involving the following variables: sampling flow rate, elution flow rate, and pH. This design has revealed that, for the studied levels, buffer concentration and pH were significant factors. When the experimental conditions established in the optimization step were pH = 8.6, and an elution flow rate of 8.6 mL min?1 using 0.5% m/v ascorbic acid, this system has allowed for the determination of uranium with a detection limit (LOD) (3σ/S) of 0.05 μg L?1 and a quantification limit (LOQ) (10σ/S) of 0.16 μg L?1. The precision expressed as the relative standard deviation (R.S.D.) of 0.8% and 1.9% at 10.0 and 1.0 μg L?1, respectively- and a preconcentration factor of 184.5 for a sample volume of 50.0 mL. Accuracy was confirmed by uranium determination in the standard reference material, NIST SRM 1566b trace element units in Oyster Tissue samples, and spike tests with recuperations ranging from 93.2 to 105%; the procedure were applied for uranium determination in tap water, well water, and drinking water samples collected from Caetité and Cruz das Almas Cities, Bahia, Brazil. Five water samples were analyzed the uranium concentrations varied from 0.50 to 2.07 μg L?1  相似文献   

9.
A newly modified extractor facilitated rapid extraction (10.0 mL, 1 h) of eleven phenols from XAD-4 resin for comparable recoveries to those with conventional Soxhlet extractor (80.0 mL, 3 h). Combined with analysis by gas chromatography and gas chromatography-mass spectrometry in selected ion monitoring mode as tert-butyldimethylsilyl derivatives, the overall method was linear (≥ 0.9991) with satisfactory precision (≤ 9.2% RSD), accuracy (≤ 7.7% RE), detection limit (≤ 0.02 μg L?1), and recovery rates (≥ 75.0%) in 0.05 to 1.0 μg L?1. Six phenolic pollutants were quantitatively screened along with bisphenol A (0.028 μg L?1) from river water.  相似文献   

10.
In this paper, an effective graphene‐based SPE clean‐up procedure coupled with GC–MS was developed for the determination of organophosphorus pesticide residues in apple juices. The apple juice samples were diluted with water and could be loaded onto the cartridge directly. Several parameters affecting the extraction efficiency were investigated, including the type of elution, washing solution, and sample pH. Under the optimized conditions, excellent limits of quantitation for the target analytes were found to be 0.15–1.18 ng/mL, and the average recoveries of the analytes at two spiked levels for real‐sample analysis ranged from 69.8 to 106.2% with RSDs less than 7.3%. Furthermore, the graphene‐based cartridges exhibited superior reusability for juice sample analysis. The proposed method is sensitive, simple, and cost saving, and provides a detection platform for the monitoring of pesticide residues.  相似文献   

11.
Summary A method has been developed for determination of twenty-four polar pesticides—nine organophosphorus pesticides, thirteen organonitrogen compounds, and two triazine degradation products—in surface water. It entails extraction of the target pesticides from 1-L water samples by solid-phase extraction (SPE), then gas chromatography (GC) with large-volume (40 μL) injection. Filtered surface water, from the St Lawrence River in Canada and the River Loire and its tributaries in France, was extracted on cartridges filled with 500 mg Carbopack B (120–400 mesh). Analysis was performed by gas chromatography with a thermionic specific detector (GC-TSD) and a mass spectrometric (MS) detector. Overall percentage recoveries were satisfactory (>70%) for all target pesticides, with precision below 10%. Detection limits were between 0.5 and 4 ng L−1.  相似文献   

12.
A liquid chromatographic method with fluorimetric detection is proposed for the determination of trace levels of oxytetracycline, tetracycline, chlortetracycline and doxycycline in water samples. The analytes are preconcentrated by solid phase extraction using reversed phase polymeric cartridges and acetonitrile as eluent. Preconcentration factors up to 125 can be obtained. The chromatographic separation is performed on a polymeric column with a gradient elution program using mobile phases based on mixtures of acetonitrile and 0.01 mol L?1 oxalic acid aqueous solution at a flow rate of 1.2 mL min?1. Tetracyclines are post-column derivatized with a reagent solution consisting of 0.1 mol L?1 Mg(II) at pH 9 at a flow rate of 0.6 mL min?1. The highly fluorescent Mg(II) chelates are detected at λ ex = 374 nm and λ em = 499 nm. The detection limits of the whole process are in the low μg L?1 level. The proposed method has been applied to the analysis of spiked natural water samples, and recovery rates higher than 80% have been obtained.  相似文献   

13.
Abstract

A multi-component target method for screening purposes to determine organic pollutants of different polarities in water is reported. The following classes of chemicals were tested: base-neutral and acidic herbicides, phenolic compounds, polycyclic aromatic hydrocarbons and phthalic acid esters.

Data was initially obtained from the extraction of one liter of water sample, using separate octyl bonded porous silica (C8) and highly crosslinked polystyrene based polymer columns (SDVB) cartridges. A second set of data was obtained using for the extraction a combined cartridge containing both phases. The analysis was carried out directly by GC-MS in SIM mode, without any derivatisation, with the exception of acidic herbicides, derivatised with pentafluorobenzylbromide. The obtained results showed recoveries between 75% and 98% at two different spiking levels, with relative standard deviations below 15%.  相似文献   

14.
In this work multifunctional sorbents, based on surfactant-coated mineral oxides, are assessed for the simultaneous extraction/preconcentration of pesticide multiresidues from aqueous environmental samples. Seventeen pesticides, representative of all the common groups (triazines, phenylureas, carbamates, azols, anilides, chloroacetanilides, organophosphorous, phenoxyacids, aryloxy acids and phenols), are selected for this study. The sorbents assessed are pure sodium dodecyl sulphate (SDS) and mixed tetrabutylammonium (TBA)-SDS hemimicelles and/or admicelles adsorbed onto alumina. Because of their multifunctional character, these sorbents provide different retention mechanisms (i.e. hydrophobic, ionic and/or π-cation interactions), which highly contribute to the efficient retention of pesticides with different polarities and acidities (bases, neutrals and acids). In addition, the low volume of eluent required for complete elution of analytes (typically 1-2 mL) avoided the need of using time-consuming and tedious evaporation steps that generally are needed when cross-linked polymeric resins or carbon materials are used as sorbents. The performance of two sorbents, i.e. SDS and TBA-SDS mixed hemimicelles/admicelles, for the admicellar solid-phase extraction (ASPE) of pesticide multiresidue was comparatively investigated. The latter was selected on the basis of the higher breakthrough volumes permitted, the lower volume of eluent required and the higher sample and eluent flow rates allowed. The proposed ASPE/LC/UV approach provided detection limits lower than 100 ng L−1 for the determination of the 17 pesticides tested. Recoveries from spiked (at the ng L−1 level) river and underground water samples was quantitative for most of the pesticides tested.  相似文献   

15.
In this work, a sensitive flow injection chemiluminescence (FI-CL) method for the determination of nematicide Fenamiphos in a rapid and simple way is proposed. Fenamiphos is first photodegraded in basic medium. These photofragments react with Ce(IV) providing the chemiluminescence signal. To the authors’ knowledge, no chemiluminescence method has been described in the literature for the determination of the nematicide Fenamiphos. All physical and chemical parameters in the flow injection chemiluminescence system were optimized in order to obtain the best sensitivity, selectivity and sample throughput. Before the injection of the sample in the FI-CL system, a preconcentration step with solid phase extraction C18 cartridges was performed. By applying solid phase extraction (SPE) to 250?mL of standard (final volume 10?mL), the linear dynamic range was between 3.4 and 60?µg?L?1, and the detection limit was 1?µg?L?1. When SPE was applied to 500?mL of standard (final volume 10?mL), the detection limit was 0.5?µg?L?1. These detection limits are below the emission limit value established by the Spanish Regulations of the Hydraulic Public Domain for pesticides (50?µg?L?1) and of the same order as the limit established for total pesticides (0.5?µg?L?1) at European Directive on the quality of water for human consumption. The sample throughput was 126 hour?1. Intraday and interday coefficients of variation were below 10% in all cases. No interference was registered in presence of usual concentrations of anions, cations and other organophosphorus pesticides. The method was successfully applied to the analysis of environmental water samples, obtaining recoveries between 96 and 107.5%.  相似文献   

16.
A simple and economical method for the determination of eight polybrominated diphenyl ethers (BDE‐28, 47, 99, 100,153,154,183, and 209) in water was developed. This method involves the use of ultrasound‐assisted dispersive liquid–liquid microextraction combined with GC‐MS in negative chemical ionization mode. Various parameters affecting the extraction efficiency, including the type and volume of extraction and dispersive solvents, salt concentration, extraction time, and ultrasonic time, were investigated. A volume of 1.0 mL of acetone (dispersive solvent) containing 10 μL tetrachloroethylene (extraction solvent) was injected into 5.0 mL of water samples and then emulsified by ultrasound for 2.0 min to produce the cloudy solution. Under the optimal condition, the enrichment factors for the eight PBDEs were varied from 845‐ to 1050‐folds. Good linearity was observed in the range of 1.0–200 ng L?1 for BDE‐28, 47, 99, and 100; 5.0–200 ng L?1 for BDE‐153, 154, and 183; and 5.0–500 ng L?1 for BDE‐209. The RSD values were in the range of 2.5–8.4% (n = 5) and the LODs ranged from 0.40 to 2.15 ng L?1 (S/N = 3). The developed method was applied for the determination of eight BPDEs in the river and lake water samples, and the mean recoveries at spiking levels of 5.0 and 50.0 ng L?1 were in the range of 70.6–105.1%.  相似文献   

17.
《Analytical letters》2012,45(3):408-423
A solid phase derivative extraction method using acetic anhydride was developed for the determination of chlorophenols and alkylphenols in water and fruit juice by gas chromatography–mass spectrometry (GC–MS). The quantitative extraction was performed by passing 100 mL of sample prepared in 0.1 mol L?1 sodium hydroxide through a column packed with 500 mg of a strong anion-exchange resin at a flow rate of 0.75 mL min?1. The retained phenols were quantitatively derivatized in the column by the introduction of 0.25 mL of acetic anhydride. The derivatized phenols were eluted with 3.0 mL of hexane and the effluent was dried under nitrogen. The final volume was diluted to fifty microliters with hexane and analyzed by GC–MS. Under the optimum conditions, preconcentration factors of 2000, limits of detection between 0.005 and 1.796 µg L?1, and relative standard deviations of 2.1% to 6.7% were obtained. The method was successfully applied to wastewater and fruit juice and the recoveries of phenols were between 76% and 111%.  相似文献   

18.
A molecularly imprinted polymer was synthesized and applied as a sorbent in the solid‐phase extraction device. The imprinted polymer was characterized by fourier‐transform infrared spectroscopy and scanning electron microscope. The results revealed that imprinted polymer possess sensitive selectivity and reliable adsorption properties for five NSAIDs. The imprinted polymer was successfully applied to the pre‐concentration for five NSAIDs in different water samples prior to UPLC‐MS/MS. In the early studies, several factors were investigated, including pH adjustment, the kind of elution solvent and the volume of elution solvent. Finally, we found that the pH 5 and an aliquot of 2 mL methanol were suitable for the water samples. The limits of detection and limits of quantitation of five nonsteroidal anti‐inflammatory drugs varied from 0.007 to 0.480 μg L−1 and 0.03 to 1.58 μg L−1, respectively. The spiking recoveries of the target analytes were 50.33‐127.64% at the levels of 0.2 μg L−1, 2 μg L−1 and 5 μg L−1. The precision and accuracy of this method showed a great increase compared with traditional solid‐phase extraction. The developed method was successfully applied to extraction and analysis of NSAIDs in different water samples with satisfactory results which could help us better understand their environmental fate and risk to ecological health.  相似文献   

19.
A gas chromatography–mass spectrometry (GC–MS) method was investigated for the simultaneous analysis of two types of endocrine disrupting compounds (EDCs), i.e., alkylphenol ethoxylates and brominated flame retardants (BFRs), by extraction and derivatization followed by GC–MS. Different solid phase extraction (SPE) cartridges (Cleanert PestiCarb, C18, Cleanert-SAX and Florosil), solvents (toluene, tetrahydrofuran, acetone, acetonitrile and ethyl acetate) and bases (NaHCO3, triethylamine and pyridine) were tested and the best chromatographic analysis was achieved by extraction with Strata-X (33?μm, Reverse Phase) cartridge and derivatization with heptafluorobutyric anhydride at 55?°C under Na2CO3 base in hexane. It was observed that APE together with lower substituted PBBs (PBB1, PBB10, PBB18 and PBB49), HBCD and TBBPA can be determined simultaneously under the same GC conditions. This simple and reliable analytical method was applied to determining trace amounts of these compounds from wastewater treatment plant samples. The recoveries of the target compounds from simulated water were above 60?%. The limit of detection ranged from 0.01 to 0.15?μg L?1 and the limit of quantification ranged from 0.05 to 0.66?μg L?1. There were no appreciable differences between filtered and unfiltered wastewater samples from Leeuwkil treatment plant although concentration of target analytes in filtered influent was slightly lower than the concentration of target analytes in unfiltered influent water. The concentrations of the target compounds from the wastewater treatment were determined from LOQ upwards.  相似文献   

20.
Here, a simple new method is proposed to evaluate water for the presence of pesticides. Specifically, pesticides for golf link maintenance were used as the targets for this investigation. Water samples containing the pesticides were mixed with particulate adsorbent, after which the pesticides were extracted from the adsorbents using supercritical fluid carbon dioxide and then analyzed by gas chromatography-mass spectrometry. The recoveries of pesticides were examined with several types of adsorbents and found to be related to their octanol/water partition coefficients (Kow) for most of the adsorbents. Good recoveries were obtained when the water samples were mixed with octadecylsilane (ODS) and stylene-divinylbenzene copolymer (XAD) resins for 15 and 30 min, respectively. In the supercritical fluid extraction, extraction pressure affected the efficiency of extraction from XAD while a little effect on extraction from ODS, probably due to the internal structure of the adsorbents. The limit of detection ranged from 0.002 to 2.3 μg L−1 and the method is suitable for the measurement of golf link pesticides in μg L−1 order to 100 μg L−1. The procedure of the proposed method was simpler than the conventional solid-phase extraction method. Finally, the method presented here was used to identify pesticides present in actual wastewater from golf links.  相似文献   

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