Multiresidue procedures for determination of triazine and organophosphorus pesticides in water by use of large-volume PTV injection in gas chromatography

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.     

Analysis of Terbumeton and its Major Metabolites by SPE and DAD-HPLC in Soil Bulk Water

A rapid and inexpensive method for simultaneous quantification of terbumeton (TER), and its major potential metabolites (TED; terbumeton-desethyl, TOH; terbumeton-2-hydroxy and TID; terbumeton-deisopropyl) in soil bulk water (SBW) samples is proposed. The analytical method involves extraction–concentration from SBW samples using a graphitized carbon black (GCB) cartridge followed by their separation–detection by reversed-phase high-performance liquid chromatography analysis using a C₁₈ column and a diode array detector. A mobile phase of acetonitrile−0.005 mol L⁻¹ phosphate buffer (pH 7.0) (35:65, v/v) at a flow rate of 0.8 mL min⁻¹ in isocratic elution mode has been used. After optimization of the extraction and separation conditions, this method can be used for the simultaneous determination of investigated compounds in the range of the international limits of 0.1 μg L⁻¹. For TER the detection limit was 0.009 μg L⁻¹ and it was 0.100, 0.550, and 0.480 μg L⁻¹ for TED, TOH, and TID, respectively. The recoveries of TER, TED, TOH, and TID from SBW samples, measured at three levels of concentration range, were found to be between 48.0 and 102.0%. The intra-day precision measured by relative standard deviation (RSD) was always lower than 9.0%.     

Quantitative trace analysis of a broad range of antiviral drugs in poultry muscle using column-switch liquid chromatography coupled to tandem mass spectrometry

A liquid chromatography–tandem mass spectrometry method for the analysis of seven antiviral drugs, zanamivir, ribavirin, oseltamivir, oseltamivir carboxylate, amantadine, rimantadine and arbidol, in poultry muscle is reported. The antiviral drugs were extracted from the homogenized poultry muscle sample using methanol. The extract was purified using tandem solid-phase extraction combining a cation exchange cartridge and a phenylboronic acid cartridge. To prevent excessive matrix effects, the analytes were separated from the matrix constituents using a column-switch liquid chromatography system combining a reversed-phase and a Hypercarb analytical column. Detection was carried out using tandem mass spectrometry. The method was fully validated according to 2002/657/EC [1] and proved to be adequate for quantification and confirmation of zanamivir and ribavirin at 10 μg kg⁻¹, oseltamivir, oseltamivir carboxylate, amantadine and rimantadine at levels below 1.0 μg kg⁻¹ and for qualitative confirmatory analysis of arbidol at levels below 1 μg kg⁻¹.     

Determination of five nitrobenzoic acids in groundwater by solid-phase extraction and liquid chromatography–mass spectrometry

A method involving solid-phase extraction (SPE) and reversed-phase liquid chromatography–mass spectrometry (LC–MS) has been developed for determination, in groundwater, of nitrobenzoic acids associated with 2,4,6-trinitrotoluene production. Pre-concentration on a co-polymer-based SPE cartridge enabled quantitative extraction of the analytes from water. Investigation of negative ion electrospray and atmospheric-pressure chemical ionization mass spectrometry indicated the sensitivity of APCI was more than twice that of ESI. An ¹⁵N-labeled internal standard was used to achieve more accurate quantitation and mass assignment. Recovery was better than 80% when 10 mL water was extracted with the SPE cartridge. Combination of SPE with LC–MS analysis resulted in method detection limits of less than 5 μg L⁻¹. The method has been used for analysis of groundwater samples collected from a site of a former ammunition plant. Contamination with nitrobenzoic acids was determined at μg L⁻¹ levels.     

Polar herbicides,pharmaceutical products,perfluorooctanesulfonate (PFOS), perfluorooctanoate (PFOA), and nonylphenol and its carboxylates and ethoxylates in surface and tap waters around Lake Maggiore in Northern Italy

A survey of contamination of surface and drinking waters around Lake Maggiore in Northern Italy with polar anthropogenic environmental pollutants has been conducted. The target analytes were polar herbicides, pharmaceuticals (including antibiotics), steroid estrogens, perfluorooctanesulfonate (PFOS), perfluoroalkyl carboxylates (including perfluorooctanoate PFOA), nonylphenol and its carboxylates and ethoxylates (NPEO surfactants), and triclosan, a bactericide used in personal-care products. Analysis of water samples was performed by solid-phase extraction (SPE) then liquid chromatography–triple-quadrupole (tandem) mass spectrometry (LC–MS–MS). By extraction of 1-L water samples and concentration of the extract to 100 μL, method detection limits (MDLs) as low as 0.05–0.1 ng L⁻¹ were achieved for most compounds. Lake-water samples from seven different locations in the Southern part of Lake Maggiore and eleven samples from different tributary rivers and creeks were investigated. Rain water was also analyzed to investigate atmospheric input of the contaminants. Compounds regularly detected at very low concentrations in the lake water included: caffeine (max. concentration 124 ng L⁻¹), the herbicides terbutylazine (7 ng L⁻¹), atrazine (5 ng L⁻¹), simazine (16 ng L⁻¹), diuron (11 ng L⁻¹), and atrazine-desethyl (11 ng L⁻¹), the pharmaceuticals carbamazepine (9 ng L⁻¹), sulfamethoxazole (10 ng L⁻¹), gemfibrozil (1.7 ng L⁻¹), and benzafibrate (1.2 ng L⁻¹), the surfactant metabolite nonylphenol (15 ng L⁻¹), its carboxylates (NPE₁C 120 ng L⁻¹, NPE₂C 7 ng L⁻¹, NPE₃C 15 ng L⁻¹) and ethoxylates (NPE _n Os, n = 3-17; 300 ng L⁻¹), perfluorinated surfactants (PFOS 9 ng L⁻¹, PFOA 3 ng L⁻¹), and estrone (0.4 ng L⁻¹). Levels of these compounds in drinking water produced from Lake Maggiore were almost identical with those found in the lake itself, revealing the poor performance of sand filtration and chlorination applied by the local waterworks.     

Determination of triazine herbicides: development of an electroanalytical method utilizing a solid amalgam electrode that minimizes toxic waste residues, and a comparative study between voltammetric and chromatographic techniques

The use of a copper solid amalgam electrode (CuSAE) for the analytical determination of triazine herbicides (atrazine and ametryne) instead of the conventional hanging mercury drop electrode (HMDE) is reported. The results obtained using electroanalytical methods utilizing each of these electrodes were also compared with those provided by the HPLC technique. The results indicated that the CuSAE electrode can be used to detect the herbicides studied, since the detection limits reached using the electrode (3.06 μg L⁻¹ and 3.78 μg L⁻¹ for atrazine and ametryne, respectively) are lower than the maximum values permitted by CONAMA (Brazilian National Council for the Environment) for wastewaters (50 μg L⁻¹) and by the US EPA (Environmental Protection Agency of the United States) in natural water samples (10.00 μg L⁻¹). An electroanalytical methodology employing CuSAE and square wave voltammetry (SWV) was successfully applied to the determination of atrazine and ametryne in natural water samples, yielding good recoveries (70.30%–79.40%). This indicates that the CuSAE provides a convenient substitute for the HMDE, particularly since the CuSAE minimizes the toxic waste residues produced by the use of mercury in HDME-based analyses.     

Determination of triazine herbicides by capillary gas chromatography with large-volume on-column injection

Summary This paper describes a study of the potential of large-volume on-column injection for the determination of triazine herbicides in clean water samples (ground-water). The sensitivity of chromatographic determination has been increased by two orders of magnitude by injection of up to 200 μL of pesticide solutions and nitrogen-phosphorus detection. Analytical characteristics expressed as precision, linear range and limit of detection have been determined, the results indicating adequate analytical performance and the ruggedness of the injection technique. As an application, gas chromatography with large-volume on-column injection and nitrogen-phosphorus detection was combined with off-line liquid-liquid micro-extraction with hexane (1 mL water/1 mL hexane). The procedure was applied to spiked groundwater samples at two concentration levels (1 and 10 μg L⁻¹) with good recoveries (between 81 and 103%, except for deethylatrazine) and repeatability (better than 15% at the 1 μg L⁻¹ level). Limits of detection of the triazine herbicides studied ranged from 0.08 to 0.16 μgL⁻¹.     

Rapid determination of amide herbicides in environmental water samples with dispersive liquid–liquid microextraction prior to gas chromatography–mass spectrometry

This paper describes a novel, simple and environmentally friendly method for rapid determination of the amide herbicides metoalchlor, acetochlor, and butachlor. It is based on dispersive liquid-liquid microextraction and gas chromatography–mass spectrometry. Factors that may influence the enrichment efficiency, such as type and volume of extraction solvent, type and volume of dispersive solvent, extraction time, and content of NaCl, were investigated and optimized in detail. Under the optimum conditions, the limits of detection of metoalchlor, acetochlor, and butachlor were 0.02, 0.04, and 0.003 μg L⁻¹, respectively. The experimental results indicated that there was linearity over the range 0.1–50 μg L⁻¹ and good reproducibility with relative standard deviations over the range 1.6–3.0% (n = 5). The proposed method has been applied for the analysis of real-world water samples, and satisfactory results were achieved. Average recoveries of spiked herbicides were in the range 80.3–108.8%. All of these indicated that the developed method would be an efficient method for simultaneous determination of the three herbicides in environmental water samples.     

Determination of sulfonylurea herbicides in soil extracts by solid-phase extraction and capillary zone electrophoresis

Summary Sulfonylurea herbicides in soil extracts were concentrated using off-line solid-phase extraction (SPE), and determined by capillary zone electrophoresis (CZE) and UV detection. The method involves extraction of soils with 0.1 M NaHCO₃ solution and subsequent preconcentration by using C₁₈ cartridges prior to separation of the pesticide using CZE. The results show that a C₁₈ cartridge is suitable for the purification of sulfonylurea herbicides in soil extracts with the recoveries ranging from 65–103%. The separation conditions affecting the resolution and detection sensitivity was systematically investigated. The sulfonylureas were resolved well using 30 mM sodium acetate (NaAc)/acetic acid (HAc)+10% acetonitrile (ACN) buffer at pH 4.80. The calibration plots for the test solutes in the concentration of 0.2–50 mg L⁻¹ were linear with detection limits in the range of 0.05–0.10 mgL⁻¹. The proposed method has been successfully demonstrated for the determination of sulfonylurea herbicides in soil samples.     

Separation of polychlorinated biphenyls from chlorinated pesticides using aminopropyl bonded-phase cartridge and determination by GC-ECD

Summary Gas chromatography of polychlorinated biphenyls and chlorinated pesticides in water samples is carried out after adsorption from a 25–500 mL sample, on a cartridge containing 100 mg aminopropyl-bonded porous silica. The clean-up step in which the PCBs and chlorinated pesticides are separated in different eluates is achieved by passing 25 mL of 40% aqueous methanol through the NH₂ Sep-Pak cartridge. The PCBs are desorbed with 500 μL ethylacetate, which is concentrated and analysis by GC-ECD. The average recovery, at 1 ppb is >97% with a standard deviation <2. The limits of detection are 0.1 ng μL⁻¹ and 5 pg μL⁻¹ respectively for Cl₃-PCB and Cl₈-PCB congeners. In the separation of PCBs from the chlorinated pesticides tested in this work, only the Aldrin is adsorbed for 60% with the PCBs by the NH₂ Sep-Pak cartridge. The method described is rapid, simple and reproducible.     

Trace analysis of sulfonylurea herbicides and their metabolites in water using a combination of off-line or on-line solid-phase extraction and liquid chromatography–tandem mass spectrometry

Two alternatives for the rapid simultaneous quantification of six sulfonylurea herbicides and five of their main degradation products in natural water are proposed. For concentration, the compounds were extracted on a polystyrene–divinylbenzene solid phase under pH and elution conditions that suppressed any hydrolysis. The eluates were analysed by liquid chromatography coupled to electrospray tandem mass spectrometry within 20 min. The whole method was validated and shown to give no hydrolysis artefacts. The application of off-line and on-line SPE of sulfonylureas enabled the 0.1 μg L⁻¹ and 1 ng L⁻¹ LOQ levels to be reached, respectively. The on-line SPE–LC–MS–MS method allowed the accurate quantitation of all sulfonylureas and three degradation products at 0.1 μg L⁻¹ or below in natural water, with an average repeatability of 8%.     

Enantioselectivity of 6-O-alkyldimethylsilyl-2,3-di-O-methyl-β-cyclodextrins as chiral stationary phases in capillary GC

Summary Clenbuterol has been determined in urine by solidphase extraction on a C₁₈ cartridge, diazotization of the eluate with nitrite, coupling of the diazonium ion with 1-(naphthyl)ethylenediamine, and separation of the azo dye formed by HPLC with a C₁₈ column and a micellar mobile phase containing 0.1 M sodium dodecyl sulphate, 12%n-butanol and 0.05 M citrate buffer, pH 3. Recoveries higher than 90% were obtained by mixing the samples with a 20% 0.2 M NaOH before extraction. Limits of detection of 51 and 6.7 ng L⁻¹ were obtained with spectrophotometric and thermal lens spectrometric detection, respectively; respective repeatabilities were 3.1% (5 μg mL⁻¹) and 5.6% (0.16 μg mL⁻¹).     

Gas chromatographic behaviour of urea herbicides

Summary Gas chromatographic conditions for determining eight phenylurea (chlortoluron, diuron, fluometuron, isoproturon, linuron, metabenzthiazuron, metobromuron and monuron) and one sulfonylurea (chlorsulfuron) herbicides were assessed. Degradation products of the herbicides formed in the injector were used for identification. Most phenylureas formed their respective carbamic acid methyl esters, metabenzthiazuron formed an aminobenzothiazol and chlorsulfuron formed an aminotriazine plus a phenylsulfonamide. On-column injection of standards using a BP10 capillary column was evaluated to identify the chromatographic behaviour. Detection limits ranged from 0.05 ng for chlorsulfuron to 3 ng for monuron with the NPD and, from 0.01 ng for chlorsulfuron to 5 ng for metabenzthiazuron with the ECD. The RSDs (n=4) were lower than 4% at the 12–25 ng level. The method was applied to the analysis of surface waters extracted with C18 Empore disks with recoveries higher than 85%. Each herbicide could be determined in water down to 0.1 μg·L⁻¹. Chlortoluron was found (11.4 μg·L⁻¹) in a water sample and its presence was confimed by gas chromatography-mass spectrometry.     

Rapid residue analysis of four triazolopyrimidine herbicides in soil, water, and wheat by ultra-performance liquid chromatography coupled to tandem mass spectrometry

A sensitive and effective method for simultaneous determination of triazolopyrimidine sulfonamide herbicide residues in soil, water, and wheat was developed using ultra-performance liquid chromatography coupled with tandem mass spectrometry. The four herbicides (pyroxsulam, flumetsulam, metosulam, and diclosulam) were cleaned up with an off-line C18 SPE cartridge and detected by tandem mass spectrometry using an electrospray ionization source in positive mode (ESI+). The determination of the target compounds was achieved in <2.0 min. The limits of detection were below 1 μg kg⁻¹, while the limits of quantification did not exceed 3 μg kg⁻¹ in different matrices. Quantitation was determined from calibration curves of standards containing 0.05–100 μg L⁻¹ with r ² > 0.997. Recovery studies were conducted at three spiked levels (0.2, 1, and 5 μg kg⁻¹ for water; 5, 10, and 100 μg kg⁻¹ for soil and wheat). The overall average recoveries for this method in water, soil, wheat plants, and seeds at three levels ranged from 75.4% to 106.0%, with relative standard deviations in the range of 2.1–12.5% (n = 5) for all analytes.     

Solid phase microextraction of volatile organic compounds using carboxen-polydimethylsiloxane fibers

Summary A new 80 μm Carboxen-polydimethylsiloxane (PDMS) fiber for solid phase microextraction (SPME) was tested for the enrichment of volatile organic compounds from water and air. Detection limits between 13 ng L⁻¹ (CH₂Cl₂) and 0.1 ng L⁻¹ (CHCl₂Br and CHClBr₂) for the combination: Carboxen-PDMS fiber and GC-ECD and between 35 ng L⁻¹ and 45 ng L⁻¹ (BTEX compounds) for the combination: Carboxen-PDMS and GC-FID using the headspace procedure were determined. Comparisons with the 100 μm PDMS fiber and further coatings show the advantages of the Carboxen-PDMS fiber with respect to extraction efficiency. Disadvantages of the new fiber compared with the 100 μm PDMS fiber are poorer repeatability and prolongation of equilibrium time. Distribution coefficients of the BTEX compounds between aqueous solution and SPME fiber coating were calculated and compared with the results of other researchers and with octanol-water partition coefficients.     

Large-volume PTV injection: Comparison of direct water injection and in-vial extraction for GC analysis of triazines

Summary The potential of large-volume PTV injection was studied for the analysis of triazine herbicides in water samples. Direct water injection and in-vial extraction were described and compared. Detection limits were between 0.01–0.02 μg L⁻¹ and relative standard deviations were <9%. Both methods are suitable for the analysis of triazines at ppt-level, although in-vial extraction is favourable for water samples with relatively large amounts of matrix components.     

Determination of Trihalomethanes in Drinking Water by Dispersive Liquid–Liquid Microextraction then Gas Chromatography with Electron-Capture Detection

Dispersive liquid–liquid microextraction (DLLME) has been used for preconcentration of trihalomethanes (THMs) in drinking water. In DLLME an appropriate mixture of an extraction solvent (20.0 μL carbon disulfide) and a disperser solvent (0.50 mL acetone) was used to form a cloudy solution from a 5.00-mL aqueous sample containing the analytes. After phase separation by centrifugation the enriched analytes in the settled phase (6.5 ± 0.3 μL) were determined by gas chromatography with electron-capture detection (GC–ECD). Different experimental conditions, for example type and volume of extraction solvent, type and volume of disperser solvent, extraction time, and use of salt, were investigated. After optimization of the conditions the enrichment factor ranged from 116 to 355 and the limit of detection from 0.005 to 0.040 μg L⁻¹. The linear range was 0.01–50 μg L⁻¹ (more than three orders of magnitude). Relative standard deviations (RSDs) for 2.00 μg L⁻¹ THMs in water, with internal standard, were in the range 1.3–5.9% (n = 5); without internal standard they were in the range 3.7–8.6% (n = 5). The method was successfully used for extraction and determination of THMs in drinking water. The results showed that total concentrations of THMs in drinking water from two areas of Tehran, Iran, were approximately 10.9 and 14.1 μg L⁻¹. Relative recoveries from samples of drinking water spiked at levels of 2.00 and 5.00 μg L⁻¹ were 95.0–107.8 and 92.2–100.9%, respectively. Comparison of this method with other methods indicates DLLME is a very simple and rapid (less than 2 min) method which requires a small volume of sample (5 mL).     

Improved extraction of glycol ethers from water by solid-phase micro extraction by carboxen polydimethylsiloxane-coated fiber

Summary 15 glycol ethers can be extracted from water by solidphase microextraction with a carboxen-polydimethyl-siloxane and separated by GC a Carbowax column. Water containing 15 glycol ethers at concentrations 0.1–10 mg.L⁻¹ is saturated at ambient temperature with NaCl. A carboxen-polydimethylsiloxane-coated fiber is then exposed to the liquid for 20 min and then automatically injected into a capillary GC injection port. Calibration curves were linear for different glycol ethers in the rang 0.1–10 mg.L⁻¹ Detection limits of each component of the mixture of glycol ethers between 50–500 μg.L⁻¹. The SPME method with direct immersion in water results in better sensivity than methods based on liquid-liquid extraction.     

Dispersive liquid-liquid microextraction and liquid chromatographic determination of pentachlorophenol in water

A simple and sensitive dispersive liquid-liquid microextraction method for extraction and preconcentration of pentachlorophenol (PCP) in water samples is presented. After adjusting the sample pH to 3, extraction was performed in the presence of 1% W/V sodium chloride by injecting 1 mL acetone as disperser solvent containing 15 μL tetrachloroethylene as extraction solvent. The proposed DLLME method was followed by HPLC-DAD for determination of PCP. It has good linearity (0.994) with wide linear dynamic range (0.1–1000 μg L⁻¹) and low detection limit (0.03 μg L⁻¹), which makes it suitable for determination of PCP in water samples.      

Forensic analysis of dyed textile fibers

A rapid, specific, and sensitive method has been developed using molecularly imprinted polymers (MIPs) as solid-phase extraction sorbents for extraction of trace tetracycline antibiotics (TCs) in foodstuffs. MIPs were prepared by precipitation polymerization using tetracycline as the template. Under the optimal condition, the imprinting factors for MIPs were 4.1 (oxytetracycline), 7.0 (tetracycline), 7.4 (chlortetracycline), 7.7 (doxycycline), respectively. Furthermore, the performance of MIPs as solid-phase extraction sorbents was evaluated and high extraction efficiency of molecularly imprinted solid-phase extraction (MISPE) procedure was demonstrated. Compared with commercial sorbents, MISPE gave a better cleanup efficiency than C18 cartridge and a higher recovery than Oasis HLB cartridge. Finally, the method of liquid chromatography–tandem mass spectrometry coupled with molecular-imprinted solid-phase extraction was validated in real samples including lobster, duck, honey, and egg. The spiked recoveries of TCs ranged from 94.51% to 103.0%. The limits of detection were in the range of 0.1–0.3 μg kg⁻¹. Chromatograms obtained by direct injection of the spiked egg extracts (5 × 10^-3 mmol L⁻¹) and purification with MISPE