Determination of analytes in medical herbs extracts by SPE coupled with two-dimensional planar chromatography in combination with diode array scanning densitometry and HPLC-diode array detector

The purpose of this study is to demonstrate an application of 2-D high-performance planar chromatography-diode array detector (DAD) and HPLC-DAD after solid-phase extraction (SPE) for identification and quantitative analysis of pesticides (isoproturon, aziprotryne, hexazinone, flufenoxuron, methabenzthiazuron, procymidone, and α-cypermethrin) in Melissa officinalis L. (Labiatae) samples. The procedure described for the determination of compounds is inexpensive and can be applied to routine analysis of analytes in medical herbs' samples after preliminary cleanup and concentration by SPE. Average recoveries on C18 SPE cartridges of pesticides eluted with 5 mL tetrahydrofuran by the proposed HPLC-DAD method, before and after 2-D-high-performance planar chromatography separation of analytes from M. officinalis L. samples spiked with pesticide at a concentration level of 10 μg/g in plant material are presented. Method validation parameters for the quantification of pesticides by the proposed HPLC-DAD after SPE method are also presented.     

Application of SPE-HPLC-DAD and SPE-TLC-DAD to the determination of pesticides in real water samples

Planar chromatography with diode array scanning (TLC-DAD) and high-performance chromatography with diode array detection (HPLC-DAD) were used to screen water samples for pesticides. Pesticides were enriched from lake water samples by SPE on C18/SDB-1, C18, C18 Polar Plus and cyanopropyl (CN) cartridges. The recovery rates were high for all extraction materials except for all pesticides on CN cartridges, for which the values were lower. SPE was used not only for preconcentration of analytes but also for their fractionation. The analytes were eluted first with methanol and then with dichloromethane. Methanol eluates were analysed by HPLC-DAD, the dichloromethane eluates with TLC-DAD. The method was validated for precision, repeatability and accuracy. The calibration plots were linear between 0.1 and 50.0 microg/mL for all pesticides, the correlation coefficients, r, were between 0.9992 and 1.000 as determined by HPLC-DAD. In the TLC experiments, the best fit for the calibration lines was found when the calibration data were analysed using a second-degree polynomial regression. Calibration plots lay between 0.1 and 17 microg/spot for all pesticides, the correlation coefficients, r, were between 0.9974 and 0.9997 determined by TLC-DAD. The LOD was between 0.04 and 0.65 microg/spot (TLC-DAD) and between 0.02 and 3.68 microg/mL (HPLC-DAD).     

Determination of pesticides in water samples from the Wieprz-krzna Canal in the Leczyńsko-Włodawskie Lake District of southeastern Poland by thin-layer chromatography with diode array scanning and high-performance column liquid chromatography with diode array detection

High-performance thin-layer chromatography with diode array scanning (TLC-DAD) and high-performance column liquid chromatography with a diode array detector (HPLC-DAD) were used to screen water samples for pesticides. Atrazine, clofentezine, chlorfenvinphos, hexaflumuron, terbuthylazine, lenacyl, neburon, bitertanol, and metamitron were enriched from canal water samples by solid-phase extraction (SPE) on octadecyl silane (C18)/styrene-divinylbenzene-1, C18, C18 Polar Plus, and cyanopropyl (CN) cartridges. Recovery rates were high for all extraction materials except CN, for which values for all pesticides were lower. SPE was used for both preconcentration and fractionation of the analytes. Analytes were eluted by means of methanol and dichloromethane. Methanol eluates were analyzed by HPLC-DAD and dichloromethane eluates by TLC-DAD. The method was validated for precision, repeatability, and accuracy. Calibration graphs were linear between 0.1 and 50.0 microg/mL for all pesticides, and correlation coefficient (r) values were between 0.9994 and 1.000 as determined by HPLC-DAD. Calibration graphs were linear between 0.1 and 1.5 microg/spot for all pesticides, and r values were between 0.9899 and 0.9987 as determined by TLC-DAD. The limit of detection was between 0.04 and 0.23 microg/spot for TLC-DAD and 0.02 and 0.45 microg/mL for HPLC-DAD.     

Determination of the rodenticides warfarin, diphenadione and chlorophacinone in soil samples by HPLC-DAD

A HPLC-DAD method is described for the analysis of the rodenticides warfarin, diphenadione and chlorophacinone, together with the phenylurea herbicides isoproturon and diuron, in soil samples. The HPLC parameters have been optimised to provide baseline separation with symmetrical peakshapes in short analysis times. The sample preparation consists of Soxhlet extraction followed by SPE clean-up on cyanopropyl silica.     

Determination of phenoxyalkanoic acids and other herbicides at the ng/ml level in water by solid-phase extraction with poly(divinylbenzene-co-N-vinylpyrrolidone) sorbent and high-performance liquid chromatography--diode-array detection

A method for the determination of phenoxyalkanoic acids and other polar compounds in environmental water samples without pH adjustment before extraction has been developed. Recoveries were calculated from 500 ml of milliQ water spiked at the level of 0.5 ng/ml using solid-phase extraction (SPE) and HPLC-DAD. Different SPE materials (RP-C18, ENV+, ENV+-C8, SAX and Oasis HLB) were tested. After method optimization, 15 of the 16 compounds studied could be extracted with recoveries better than 70% on the most suitable copolymeric poly(divinylbenzene-co-N-vinylpyrrolidone) material (Oasis HLB cartridges).     

Determination of enrofloxacin and its metabolite ciprofloxacin in goat milk by high-performance liquid chromatography with diode-array detection. Optimization and validation

A high-performance liquid chromatography-diode array detection method (HPLC-DAD) combined with liquid chromatography-mass spectrometry was developed for the determination of enrofloxacin and its metabolite ciprofloxacin in goat milk. The HPLC-DAD method validation was compliant with the "DG SANCO 1805/2000" European regulation. The residues were extracted from milk with phosphate buffer, purified on a C18 Speedisk cartridge SPE (Baker) and then analysed using HPLC-DAD set at 277 nm. The decision limit (CCa) calculated by spiking samples at 100 microg/kg with both analytes, taking into account the maximum residue limit (MRL) of 100 microg/kg established by the European Union for the sum of enrofloxacin and its metabolite ciprofloxacin in milk, was 105.3 microg/kg for enrofloxacin and 105.5 microg/kg for ciprofloxacin. The detection capability (CCbeta) was 110.7 and 110.9 microg/kg for enrofloxacin and ciprofloxacin, respectively. The mean recoveries of the method, calculated by spiking samples at 50, 100 and 150 microg/kg were 84% for enrofloxacin and 88% for ciprofloxacin. The limit of quantification was 20 microg/kg for both analytes. The HPLC-DAD validated method was successfully applied for the first time in goats milk, and proved to be suitable for the sensitive and accurate quantification and confirmation analysis of enrofloxacin and ciprofloxacin for regulatory purposes.     

Determination of Non-Steroidal Anti-Inflammatory Drugs in Natural Waters Using Off-Line and On-Line SPE Followed by LC Coupled with DAD-MS

Two different procedures for simultaneous determination of six NSAIDs (diflunisal, diclofenac, fenoprofen, ibuprofen, naproxen and tolmetin) in environmental waters are described. Final analysis of target compounds is performed by reversed-phase liquid chromatography – diode array detection and mass spectrometry (HPLC-DAD and LC-MS), whereas sample preparation is based on solid-phase extraction (SPE). A variety of sorbents and their respective advantages and disadvantages are discussed. For the off-line SPE of NSAIDs from water samples, a LiChrolut RP-18 was selected out of all investigated sorbents. In case of on-line coupling of SPE with chromatographic system LiChrosphere RP-18 was selected as the best one in terms of recovery of NSAIDs evaluated, RSD and availability. The applicability of the method was also evaluated. Method detection limits were in the range of 0.7−94 ng L⁻¹. Recoveries ranged from 96 to 109% and relative standard deviations were lower than 5%. The procedures were shown to be linear over a wide range of concentration, exhibited satisfactory repeatability and accuracy, and reached limits of detection in the low ng L⁻¹ range. No breakthrough volume was observed neither for off-line SPE (in the studied range of 100, 200, 300, 500, 700, 1000 and 2000 mL of tap water sample) nor for on-line SPE (in the wide range of 10 mL, 20 mL, 30 mL, 50 mL, 70 mL, 100 mL and 200 mL of tap water sample).     

Solid-phase extraction versus solid-phase microextraction for the determination of chlorinated paraffins in water using gas chromatography-negative chemical ionisation mass spectrometry

Solid-phase extraction (SPE) and solid-phase microextraction (SPME) were evaluated for the analysis of short-chain chlorinated paraffins (SCCPs) in water samples using gas chromatography coupled to negative chemical ionisation mass spectrometry (GC-NCI-MS). For SPE optimisation, four commercially available SPE cartridges were tested and several SPE parameters, such as the elution solvent, elution volume and breakthrough volume were studied. The best results were obtained with Varian Bond Elut-C18. In order to achieve a high selectivity in the determination of SCCPs, GC-NCI-MS was used. Quality parameters of the optimised SPE and SPME procedures were determined, and the best results were obtained for the SPE/GC-NCI-MS method with LODs of 5 and 20 ng l(-1) for tap and river water, respectively. This method was successfully applied to the analysis of SCCPs in river water samples at concentrations below the microg l(-1) level.     

Simultaneous determination of selected endocrine disrupters (pesticides,phenols and phthalates) in water by in-field solid-phase extraction (SPE) using the prototype PROFEXS followed by on-line SPE (PROSPEKT) and analysis by liquid chromatography-atmospheric pressure chemical ionisation-mass spectrometry

In this study, a new procedure, based on on-line solid-phase extraction (SPE) and analysis by liquid-chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS), has been developed for the simultaneous, multianalyte determination of 21 selected pesticides, phenols and phthalates in water. SPE was carried out on polymeric PLRP-s cartridges by percolating 20 mL-samples. For sample preconcentration, the performance of a prototype programmable field extraction system (PROFEXS) was evaluated against the commercial laboratory bench Prospekt system used for method development. The Profexs is designed for the automated on-site sampling, SPE preconcentration, and storage of up to 16 samples in SPE cartridges. These cartridges are further eluted and on-line analyzed with the Prospekt coupled to the chromatographic system. In the optimized method, where completely on-line SPE-LC-MS analysis of the samples is carried out with the Prospekt in the laboratory, detection limits lower than 100 ng/L, and satisfactory precision (relative standard deviations <25%) and accuracies (recovery percentages >75%) were obtained for most investigated compounds from the analysis of spiked Milli-Q water. The extraction efficiency achieved with the Profexs was comparable to that of the Prospekt for most compounds and somewhat lower for the most apolar analytes, probably due to adsorption on the pump filters. The completely on-line optimized method was applied to the analysis of surface water, ground water and drinking water from a waterworks in Barcelona. Some pesticides and phenols were found in both surface water and groundwater at ng/L or µg/L levels, but not in the final drinking water. Di(2-ethylhexyl)phthalate (DEHP) was present in all samples investigated, including blanks. To the author's knowledge, this is the first work describing the application of a fully automated on-line SPE-LC-MS method for the simultaneous analysis of pesticides, phenols, and phthalates in water, and the second one that examines the possibilities of the prototype Profexs for automated on-site SPE preconcentration of organic pollutants from water samples.     

高效液相色谱法同时测定食品中6种对羟基苯甲酸酯

建立了同时检测食品中6种对羟基苯甲酸酯的高效液相色谱-二极管阵列检测器( HPLC-DAD)定量分析方法.样品用乙腈提取,经LC-C18固相萃取柱净化,采用Agilent C18色谱柱分离,甲醇/水溶液梯度洗脱,二极管阵列检测器检测,外标法定量.结果表明:6种对羟基苯甲酸酯在1.0～500.0 mg/L范围内线性关系良好(r≥0.9997);检出限为0.0016～0.0081 mg/L(S/N=3);6种对羟基苯甲酸酯各添加水平在经表面处理的新鲜蔬菜、水果、醋、碳酸饮料及牛奶,食品馅料中的回收率为85.1％～95.4％;相对标准偏差为3.6％～10.9％.     

Liquid chromatographic determination of fosthiazate residues in environmental samples and application of the method to a fosthiazate field dissipation study

A method was developed and validated for the determination of residues of the organophosphorus nematicide fosthiazate in soil and water by using reversed-phase liquid chromatography with UV detection. Good recoveries (>85%) of fosthiazate residues were obtained from water samples (drinking water, groundwater, and liquid chromatography water) after passage of 0.5-2 L water through solid-phase extraction (SPE) C-18 cartridges and subsequent elution with ethyl acetate. Residues in soil were extracted with methanol-water (75 + 25, v/v) on a wrist-action shaker, and the extract was cleaned up on C-18 SPE cartridges before analysis. The method was validated by analysis of a range of soils with different physicochemical characteristics; recoveries exceeded 87% at fortification levels ranging from 0.02 to 5.0 mg/kg. The precision values obtained for the method, expressed as repeatability and reproducibility, were satisfactory (<11%). Fosthiazate detection limits were 0.025 microg/L and 0.005 mg/kg for water and soil samples, respectively. The decline in the levels of fosthiazate residues in soil was measured after application of fosthiazate to protected tomato cultivation. The dissipation of fosthiazate residues followed first-order kinetics with a calculated half-life of 21 days.     

A simple method for simultaneous determination of nine triazines in drinking water

A simple, effective, and economic method for determination of nine triazines (ametryn, atrazine, cyanazine, prometryn, propazine, simazine, simetryn, terbuthylazine, and terbutryn) in drinking water based on solid-phase extraction (SPE) followed by high-performance liquid chromatography-diode array detection (HPLC-DAD) was developed. A specialized solid phase (Oasis HLB) was used, and the parameters that may affect the efficiency of SPE were optimized. The limits of detection (ranged from 0.010 to 0.023 µg L^?1) were satisfactory and allow the determination of triazines at the levels required by European Union legislation. Repeatability (2.4–7.6%) and intermediate precision (0.9–11.0%) calculated at 0.1 µg L^?1 (legislation level) were adequate. The accuracy calculated as the average recovery of spiked tap and mineral waters was higher than 86% for all compounds. The developed method also could be used for undergraduate laboratory experiments because it acquaints students with solution preparation, solid phase extraction procedure, and HPLC-DAD technique.     

Semi-automated disk-type solid-phase extraction method for polychlorinated dibenzo-p-dioxins and dibenzofurans in aqueous samples and its application to natural water

A disk-type solid-phase extraction (SPE) method was used for the extraction of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in natural water and tap water. Since this SPE system comprised airtight glass covers with a decompression pump, it enabled continuous extraction with semi-automation. The disk-type SPE method was validated by comparing its recovery rates of spiked internal standards with those of the liquid-liquid extraction (LLE). The recovery ranges of both methods were similar in terms of (13)C-labeled internal standards: 64.3-99.2% for the LLE and 52.4-93.6% for the SPE. For the native spike of 1,3,6,8-tetrachlorinated dibenzo-p-dioxin (TCDD) and octachlorinated dibenzo-p-dioxin (OCDD), the recoveries in the SPE were in the normal range of 77.9-101.1%. However, in the LLE, the recoveries of 1,3,6,8-TCDD decreased significantly. One of the reasons for the low recovery is that the solubility of this congener is high. The semi-automated SPE method was applied to the analysis of different types of water: river water, snow, sea water, raw water for drinking purposes, and tap water. PCDD/F congeners were found in some sea water and snow samples, while their concentrations in the other samples were below the limits of detection (LODs). This SPE system is appropriate for the routine analysis of water samples below 50L.     

Nanometer‐sized alumina packed microcolumn solid‐phase extraction combined with field‐amplified sample stacking‐capillary electrophoresis for the speciation analysis of inorganic selenium in environmental water samples

In this paper, a new method of nanometer‐sized alumina packed microcolumn SPE combined with field‐amplified sample stacking (FASS)–CE‐UV detection was developed for the speciation analysis of inorganic selenium in environmental water samples. Self‐synthesized nanometer‐sized alumina was packed in a microcolumn as the SPE adsorbent to retain Se(IV) and Se(VI) simultaneously at pH 6 and the retained inorganic selenium was eluted by concentrated ammonia. The eluent was used for FASS–CE–UV analysis after NH₃ evaporation. The factors affecting the preconcentration of both Se(IV) and Se(VI) by SPE and FASS were studied and the optimal CE separation conditions for Se(IV) and Se(VI) were obtained. Under the optimal conditions, the LODs of 57 ng L^?1 (Se(IV)) and 71 ng L^?1 (Se(VI)) were obtained, respectively. The developed method was validated by the analysis of a certified reference material of GBW(E)080395 environmental water and the determined value was in a good agreement with the certified value. It was also successfully applied to the speciation analysis of inorganic selenium in environmental water samples, including Yangtze River water, spring water, and tap water.     

Development and application of methods using SPE,HPLC-DAD,LC-ESI-MS/MS and GFAAS for the determination of herbicides and metals in surface and drinking water

A preliminary study of the pollution in surface and drinking waters caused by herbicides and metals in the Municipal Water Supply System (CORSAN) in Rio Grande city, RS, Brazil, is reported. The occurrence of 5 herbicides and 9 metals was studied in surface and drinking water through the analysis of 2 sampling spots at CORSAN. The analytical determination was performed by solid-phase extraction (SPE), high performance liquid chromatography-photodiode array detection (HPLC-DAD) and liquid chromatography coupled to electrospray ionisation tandem mass spectrometry (LC-ESI-MS/MS) for herbicides, and graphite furnace atomic absorption spectrometry (GFAAS) for metals. The concentrations of herbicides in the surface water were very low; however, the herbicide clomazone was detected in more than 50% of the samples analysed in concentration exceeding 1.0?µg L^?1. The concentration of metals was below the Maximum Contaminant Level (MCL) set by the Brazilian regulation.     

Comparison of solvent extraction and solid-phase extraction for the determination of organochlorine pesticide residues in water.

Solid-phase extraction (SPE) of organochlorine pesticide residues from environmental water samples was evaluated using octadecyl (C18)-bonded porous silica. The efficiency of SPE of these pesticide residues from reagent water samples at 1-5 micrograms dm-3 levels was compared with those obtained by solvent extraction with hexane and Freon TF (trichlorotrifluoroethane). Average recoveries exceeding 80% for these organochlorine pesticides were obtained via the SPE method using small cartridges containing 100 mg of 40 microns C18-bonded porous silica. The average recovery by solvent extraction with hexane and Freon TF exceeded 90% in both instances. It was concluded that the recoveries and precision for the SPE of organochlorine pesticides were poorer than those for the solvent extraction method. Organochlorine pesticide residue levels in environmental water samples from two major rivers flowing through predominantly rice-growing areas were monitored by gas chromatography using the solvent extraction method with hexane. Exceptionally high levels of organochlorine pesticide residues such as BHC, DDT, heptachlor, endosulfan and dieldrin were found in these water samples.     

Determination of the pesticides considered as endocrine-disrupting compounds (EDCs) by solid-phase extraction followed by gas chromatography with electron capture and mass spectrometric detection

An SPE method followed by GC-electron capture detection (ECD) with confirmation by MS for the trace determination of four pesticides considered as endocrine-disrupting compounds (EDCs) in natural waters and sediments has been developed. Target analytes, fenarimol, fenvalerate, pendimethalin, and vinclozolin, belong to different chemical groups and are used mainly in agriculture. In the present study, analysis employs an offline SPE step for the extraction of the target analytes from natural waters. Sonication and subsequent SPE clean-up was used for extraction and purification of the sediment samples which were finally treated with activated copper powder. The type of SPE disk, eluents as well as solution parameters including pH value, and concentrations of salts and humic substances were examined for the efficiency of the method. The recoveries of all pesticides were in relatively high levels, ranging from 75 to 97% for waters and 71 to 84% for sediment samples. Both methods were applied to real water and sediment samples and the presence of the tested compounds was investigated.     

Development and optimization of the determination of pharmaceuticals in water samples by SPE and HPLC with diode‐array detection

This paper describes the development, optimization, and validation of a method for the determination of five pharmaceuticals from different therapeutic classes (antibiotics, anthelmintics, glucocorticoides) in water samples. Water samples were prepared using SPE and extracts were analyzed by HPLC with diode‐array detection. The efficiency of 11 different SPE cartridges to extract the investigated compounds from water was tested in preliminary experiments. Then, the pH of the water sample, elution solvent, and sorbent mass were optimized. Except for optimization of the SPE procedure, selection of the optimal HPLC column with different stationary phases from different manufacturers has been performed. The developed method was validated using spring water samples spiked with appropriate concentrations of pharmaceuticals. Good linearity was obtained in the range of 2.4–200 μg/L, depending on the pharmaceutical with the correlation coefficients >0.9930 in all cases, except for ciprofloxacin (0.9866). Also, the method has revealed that low LODs (0.7–3.9 μg/L), good precision (intra‐ and interday) with RSD below 17% and recoveries above 98% for all pharmaceuticals. The method has been successfully applied to the analysis of production wastewater samples from the pharmaceutical industry.     

Titanium wire-based SPE coupled with HPLC for the analysis of PAHs in water samples

Titanium wire-based solid phase extraction (SPE) is developed for the analysis of six different polycyclic aromatic hydrocarbons in water samples with coupling with high performance liquid chromatography. The adsorbent is a Ti wire on which TiO(2) nanotubes are first formed by anodization and then Au nanoparticles and n-octadecanethiol are modified. The surface composition and structure of the adsorbent were characterized in detail using field emission scanning electron microscope and Fourier transform infrared spectroscopy. The main parameters affecting the extraction efficiency, such as the volume of the organic modifier, extraction time, elution solvent, and desorption time were optimized. Good linearities ranging from 0.025 to 30 μg L(-1) with correlation coefficients (R(2)) ranging from 0.9964 to 0.9999 and low limits of detection were obtained in spiked water samples. Furthermore, this method was successfully applied in the analysis of real river water samples with recoveries in the range of 75.33-115.83% and relative standard deviations ranging from 4.85 to 10.77%. The developed SPE can be a particularly convenient means of sample pretreatment for environmental water samples.