Fast high-performance liquid chromatographic analysis of mianserin and its metabolites in human plasma using monolithic silica column and solid phase extraction

A fast high-performance liquid chromatography (HPLC) method was developed and validated for the simultaneous determination of mianserin (MIAN) and its metabolites desmethylmianserin (DMM), 8-hydroxymianserin (HM) and mianserin-N-oxide (MNO) in human plasma. Each compound, together with internal standard (propranolol) was extracted from the plasma matrix using solid phase extraction. Chromatographic resolution of the analytes was performed on a Chromolith Speed Rod monolithic silica column ( mm i.d.) under isocratic conditions using a mobile phase of 74:26 (v/v) 25 mM phosphate buffer (pH 5.3 adjusted with phosphoric acid): acetonitrile. The elution of the analytes were monitored at 292 mm and conducted at ambient temperature. Because of high column efficiency the mobile phase was pumped at a flow rate of 3.5 ml/min. The total run time of the assay was 5 min. The method was validated over the range of 10-200 ng/ml for MIAN, 10-150 ng/ml for DMM, 20-300 ng/ml for HM and 25-500 ng/ml for MNO. The method proved to be precise (within-run precision ranging from 1.6 to 6.9% R.S.D. and between-run precision ranging from 1.3 to 7.2% R.S.D.) and accurate (within-run accuracies ranged from 1.4 to 6.4% and between-run accuracies ranging from 1.5 to 4.5%). The mean absolute recoveries were 95.7, 94.8, 99.6, and 102.6% for MIAN, DMM, HM and MNO, respectively. The limit of quantitation (LOQ) for MIAN and DMM was 10 ng/ml and for HM and MNO were 20 and 25 ng/ml in human plasma, respectively. The limit of detection (LOD) for MIAN, DMM, HM and MNO was 5, 2.5, 10 and 15 ng/ml, respectively. The described method demonstrates the feasibility for employing monolithic columns to effect rapid bioanalytical HPLC analysis for the quantitative determination of MIAN and its major metabolites in human plasma.     

Liquid chromatographic determination of cis-platin as platinum(II) in pharmaceutical preparation, serum and urine samples of cancer patients

Spectrophotometric and high performance liquid chromatographic (HPLC) methods have been developed for the determination of cis-platin and carboplatin based on the pre-column derivatization of platinum(II) with 2-acetylpyridine-4-phenyl-3-thiosemicarbazone. The complex was extracted in chloroform with molar absorptivity of 2.2 × 10⁴ L mol⁻¹ cm⁻¹ at 380 nm. The complex eluted from a Phenomenex C-18 (150 mm × 4.6 mm i.d.) column with methanol:water:acetonitrile:tetrabutyl ammonium bromide (1 mM) (44:30:25:1, v/v/v/v) with a flow rate of 1 ml/min and UV detection at 260 nm. Ruthenium(IV) and selenium(IV) also separated completely. The linear calibration curve was with 0.5-12.5 μg/ml and detection limit of 10 ng/ml platinum(II).The analysis of cis-platin and carboplatin injections by spectrophotometric and HPLC methods indicated relative standard deviation (R.S.D.) of 0.66-2.1%. The method was used for the determinations of cis-platin in serum and urine of cancer patients after chemotherapy and platinum contents were found 148-444 and 50-90 ng/ml with R.S.D. of 0.3-3.0 and 0.6-2.4% for the serum and urine, respectively. The recovery of platinum(II) from serum was 97% with R.S.D. 2.2%.     

A liquid chromatography–atmospheric pressure photoionization tandem mass spectrometric method for the determination of azaarenes in atmospheric particulate matter

The development, optimization and validation of a liquid chromatography–atmospheric pressure photoionization tandem mass spectrometric (LC–APPI/MS/MS) method for the determination of 15 azaarenes (4-azafluorene, benzo[h] and -[f]quinoline, phenanthridine, acridine, 1-azafluoranthene, 4-azapyrene, benz[a]- and -[c]acridine, -10-azabenzo[a]pyrene, 7,9- and 7,10-dimethylbenz[c]acridine, dibenz[a,j]-, -[c,h] and [a,i]acridine) in airborne particulate matter is described. Each compound was detected and quantified operating in multiple reaction monitoring mode. Extraction of azaarenes was achieved using accelerated solvent extraction (ASE) with dichlormethane/methanol (50/50, v/v). After extraction, no additional clean-up procedure like solid phase or liquid/liquid extraction was necessary. Limits of quantification (S/N × 10) ranged from 0.2 pg/μl to 1.4 pg/μl, matrix dependent recoveries were between 57% and 94%, with relative standard deviations from 8% to 17%. Applicability of the method was demonstrated analyzing 10 samples of particulate matter (PM_2.5) collected in winter 2008. In all samples dimethylbenz[c]acridines as well as dibenzacridines were below the limit of quantification, concentration of the remaining analytes were in the range from 0.002 ng/m³ to 0.356 ng/m³.     

Liquid chromatographic determination of vanadium in petroleum oils and mineral ore samples using 2-acetylpyridne-4-phenyl-3-thiosemicarbazone as derivatizing reagent

Liquid chromatographic method has been developed, based on precolumn derivatization of vanadium(V) with 2-acetylpyridine-4-phenyl-3-thiosemicarbazone (APPT). The complex is extracted in chloroform together with palladium(II), tin(II) and iron(III) and eluted and separated completely from Kromasil 100 C-18, 10 μm (25 cm × 4.6 mm i.d.) column with methanol:water:acetonitrile (60:30:10, v/v/v) with a flow rate of 1 ml/min. UV detection was at 260 nm. Linear calibration curve was obtained with 1-12.5 μg/ml vanadium(V) with detection limit of 8 ng/injection (20 μl). A number of metal ions tested did not affect the determination of vanadium. The test mixtures were analyzed for vanadium(IV) and vanadium(V) contents and relative% error was obtained ±1-8%. The method was applied for the determination of vanadium in petroleum oils and mineral ore samples with vanadium contents of 0.32-2.3 and 121.7-717.3 μg/g with R.S.D. of 1.5-4.5 and 0.38-4.7%, respectively. The results correlated with reported values and by atomic absorption spectrophotometry.     

Synthesis of imprinted polymer material with palladium ion nanopores and its analytical application

Ion imprinted polymer (IIP) materials with nanopores were prepared by formation of ternary complex of palladium imprint ion with dimethylglyoxime (DMG) and 4-vinylpyridine (VP, functional monomer) and thermally copolymerizing with styrene (crosslinking monomer) and divinylbenzene (cross linker) and 2,2′-azobisisobutyronitrile as initiator. The synthesis was carried out with cyclohexanol as porogen and subsequently leached with 50% (v/v) HCl to obtain leached IIP particles. These leached IIP particles can now pick up palladium ions from dilute aqueous solutions. The optimal acidity for quantitative enrichment was 0.2-0.4N HCl and eluted completely by stirring for 15 min with 2×10 ml of 50% (v/v) HCl. The palladium ion imprinting polymer gave 100 times higher distribution ratio than ion recognition (blank) polymer (IRP). Further, percent extraction, distribution ratio and selectivity coefficients of palladium and other selected inorganic ions using IRP and IIP particles were determined and compared. Five replicate determinations of 50 μg of palladium in 1 l of solution gave a mean absorbance of 0.200 with a relative standard deviation of 2.12%. The detection limit corresponding to three times the standard deviation of the blank was 2.5 μg of palladium/l.     

Ultra performance liquid chromatography-tandem mass spectrometry for the determination of epirubicin in human plasma

A novel method has been developed for the determination of epirubicin in human plasma by ultra performance liquid chromatography combined with tandem mass spectrometry (UPLC-MS/MS). Epirubicin and internal standard epidaunorubicin were achieved from plasma via solid-phase extraction (SPE) using Oasis HLB cartridge. The analysis was performed on an AcQuity UPLC™ BEH C₁₈ column (1.7 μm, 50 mm × 1 mm i.d.) utilizing a gradient elution profile and a mobile phase consisting of 0.1% formic acid in water and acetonitrile. The analytes were detected using an electrospray ionization tandem mass spectrometry in positive ion mode with multiple reaction monitoring (MRM). This method combines both advantages of UPLC and MS/MS, producing superior reliability, sensitivity and accuracy to previously published methods. The calibration curve was linear (r² = 0.998) over the concentration range of 0.50-100.0 ng/ml. The limits of detection (LOD) and quantification (LOQ) for epirubicin were 0.10 and 0.50 ng/ml using 0.2 ml plasma sample, respectively. Recoveries of greater than 89% with intra- and inter-day precision (R.S.D.) less than 12% were obtained at concentrations above the LOQ. The present method has been successfully applied to analyze human plasma samples taken from patients administered epirubicin intravenously. Also, the principal metabolite epirubicinol was detected in all the patient plasma samples under investigation. The proposed method is very rapid, reliable and sensitive, and can be applicable to therapeutical drug monitoring and pharmacokinetic studies of epirubicin.     

Ultrasound-assisted extraction and derivatization of sterols and fatty alcohols from olive leaves and drupes prior to determination by gas chromatography–tandem mass spectrometry

A method for simultaneous determination of sterols and fatty alcohols in olive leaves and drupes based on ultrasound-assisted extraction and derivatization prior to individual identification–quantitation by chromatographic separation and mass spectrometry detection (single ion monitoring mode) is reported here. The sample preparation procedure involves the following steps: (i) leaching of the raw material accelerated by ultrasound; (ii) saponification of the leachate, also accelerated by ultrasound, and separation of the unsaponifiable matter; (iii) cleaning of the extract by solid-phase extraction; (iv) silylation of the target analytes—also assisted by ultrasound; (v) injection into the gas chromatograph for identification–simultaneous quantitation of the two families of compounds. Individual separation–determination of the fatty alcohols and sterols provide limits of detection (LOD) in the range 9.8 × 10⁻² to 2 μg/l and 5.0–6.0 μg/l, respectively. The LOQs range from 0.3 to 0.9 μg/l and 17.0 to 21.0 μg/l, and the linear dynamic ranges are between LOQ and 25.0 μg/ml. The between-day precision, expressed as relative standard deviation (RSD), ranges between 3.6 and 6.1% and the within-laboratory reproducibility, also expressed as RSD, between 6.4 and 9.2%. Within the study of the metabolomic profile of the unsaponifiable fraction in olive tree, the method has been applied to the determination of the target analytes in different varieties of olive trees cultivated in the same zone, so that differences in this unsaponifiable fraction can be attributed to characteristics of the target varieties. As compared with its European Union counterpart, the method is endowed with similar analytical characteristics and drastic shortening of the operational time.     

Improved liquid chromatographic method with pulsed electrochemical detection for the analysis of kanamycin

This work describes the separation of the main component kanamycin A from its related substances using an improved liquid chromatographic method with pulsed electrochemical detection (LC-PED). Two methods, one using volatile ion pairing agents and the other using non-volatile ones were developed. Using volatile additives, the total run time was rather long with no possibility of developing gradient elution. The non-volatile method was found to be more performant and hence was selected for further quantitative work. This method employed gradient elution in order to reduce the analysis time and to improve the sensitivity of the late eluting peaks. Mobile phase A consisted of sodium sulphate (5.0 g/l), sodium octanesulphonate (0.5 g/l) and 0.2 M phosphate buffer pH 3.0 (50.0 ml/l). Mobile phase B was the same as A except for the amount of sodium sulphate which was increased to 15 g/l. Using a Platinum EPS column (150 mm × 4.6 mm ID, 3 μm) kept at 45 °C, 22 components could be separated within 45 min indicating that this method is much more selective than other already published ones. Robustness of the method was examined by means of an experimental design. The limit of detection and limit of quantitation were found to be 1.7 and 5 ng, respectively. The method was found to be linear in the range LOQ–600 ng injected with a coefficient of determination equal to 0.999.     

Liquid chromatographic high-throughput analysis of ketamine and its metabolites in human plasma using a monolithic silica column and solid phase extraction

A rapid and sensitive liquid chromatographic (LC) assay was developed for the simultaneous determination of ketamine (KE) and its two main metabolites, namely, norketamine (NK) and dehydronorketamine (DHNK) in human plasma. Each compound together with an internal standard (Labetalol) was extracted from the plasma matrix using solid phase extraction (SPE). The applicability of monolithic LC phases in the field of quantitative bioanalysis has been evaluated. The existing method with UV detection set at 220 nm was successfully transferred from a conventional reversed phase column to a 10 cm × 4.6 mm i.d. monolithic silica column. By simply increasing the mobile phase flow-rate, run times were about six-fold reduced and consumption of mobile phase were about two-fold decreased, while the chromatographic resolution of the analytes remain unaffected. The method was validated over the range 25-2000 ng/mL for KE, 25-1500 ng/mL for NK, and 15-750 ng/mL for DHNK. The method proved to be precise (within-run precision ranges from 2.2 to 7.2% and between-run precision ranges from 3.7 to 8.2%) and accurate (within-run accuracies ranged from 1.3 to 7.2% and between-run accuracies ranged from 1.5 to 8.7%). The mean absolute recoveries were 95.3, 96.9, and 103.9% for KE, NK and DHNK, respectively. The limit of quantitation (LOQ) and limit of detection (LOD) for KE and NK in human plasma were 25 and 12.5 ng/mL, respectively, and for DHNK were 15 and 7.5 ng/mL (S/N = 3). The assay should be suitable for use in routine determination of KE and its metabolites in human plasma.     

Determination of 7-aminoflunitrazepam in urine by dispersive liquid-liquid microextraction with liquid chromatography-electrospray-tandem mass spectrometry

Dispersive liquid-liquid microextraction (DLLME) and liquid chromatography-electrospray-tandem mass spectrometry (LC-ES-MS/MS) procedure was presented for the extraction and determination of 7-aminoflunitrazepam (7-aminoFM2), a biomarker of the hypnotic flunitrazepam (FM2) in urine sample. The method was based on the formation of tiny droplets of an organic extractant in the sample solution using water-immiscible organic solvent [dichloromethane (DCM), an extractant] dissolved in water-miscible organic dispersive solvent [isopropyl alcohol (IPA)]. First, 7-aminoFM2 from basified urine sample was extracted into the dispersed DCM droplets. The extracting organic phase was separated by centrifuging and the sedimented phase was transferred into a 300 μl vial insert and evaporated to dryness. The residue was reconstituted in 30 μl mobile phase (20:80, acetonitrile:water). An aliquot of 20 μl as injected into LC-ES-MS/MS. Various parameters affecting the extraction efficiency (type and volume of extraction and dispersive solvent, effect of alkali and salt) were evaluated. Under optimum conditions, precision, linearity (correlation coefficient, r² = 0.988 over the concentration range of 0.05-2.5 ng/ml), detection limit (0.025 ng/ml) and enrichment factor (20) had been obtained. To our knowledge, DLLME was applied to urine sample for the first time.     

Headspace single drop microextraction of methylcyclopentadienyl-manganese tricarbonyl from water samples followed by gas chromatography-mass spectrometry

Headspace single drop microextraction coupled to gas chromatography-mass spectrometry yielded a simple, fast and virtually solventless analytical protocol used for the headspace analysis of aqueous samples contaminated with methylcyclopentadienyl-manganese tricarbonyl (MMT). Initially, several experimental parameters were controlled and optimized and the optimum conditions found were 2.5 μl octane microdrop exposed for 20 min to the headspace of a 10 ml aqueous sample (15 ml vial) containing 20% (w/v) NaCl and stirred at 1250 rpm. The calculated calibration curves gave a high level of linearity for MMT with correlation coefficients >0.9995 after conducting a 3-day study. The limit of detection was calculated to be 0.21 μg l⁻¹. The proposed method achieved an enrichment factor of the order of 2100 and a 53% recovery after extracting the spiked aqueous solution for 20 min under the optimized experimental conditions. The repeatability and intra-day reproducibility of the proposed method, expressed as relative standard deviation were 8.4 and 6.4%, respectively. Finally, analysis of spiked tap and wastewater samples revealed that matrix had little effect upon extraction.     

Molecularly imprinted solid phase extraction for rapid screening of cephalexin in human plasma and serum

A molecularly imprinted solid phase extraction (MISPE) method was developed for the rapid screening of cephalexin in human plasma and serum. The method employed a micro-column packed with molecularly imprinted polymer (MIP) particles for the selective solid phase extraction (SPE) of cephalexin. Since the MIP interacted indiscriminately with two other α-aminocephalosporins, cefradine and cefadroxil, their removal was ultimately achieved using differential pulsed elution (DPE) with acetonitrile+12% acetic acid. Cephalexin was then determined in a final pulsed elution (FPE) with methanol+1% trifluoroacetic (CF₃COOH, TFA) acid. This excellent selectivity represents a significant advance in analytical separation, demonstrating how a MIP can differentiate between molecules that are structurally dissimilar only in their non-hydrogen-bonding moieties, even if their hydrogen-bonding moieties are identical to each other. With UV detection, a concentration detection limit of 0.1 μg/ml (or 2 ng in 20 μl) was afforded for cephalexin. By increasing the CHCl₃ flow rate to 1.25 ml/min, each MISPE-DPE-FPE analysis required only 2 min to complete. Rapid screening was demonstrated in a modified MISPE-PE method, which used 14% CH₃COOH+CH₃CN as the mobile phase, followed by direct PE with 1% TFA+CH₃OH.     

Streamlined sample preparation procedure for determination of perchlorate anion in foods by ion chromatography-tandem mass spectrometry

A rapid, sensitive, and specific method was developed for the determination of perchlorate anion in foods. The foods included high moisture fruits and vegetables, low moisture foods (e.g. wheat flour and corn meal), and infant foods. Improvements to existing procedures were made in sample preparation that reduced sample test portion size from 100 to 5 or 10 g, extraction solvent volume from 150 to 20-40 ml, and replaced blending extraction-vacuum filtration and their associated large glassware with a simple shakeout-centrifugation in a small conical tube. Procedures common to all matrices involved: extraction, centrifugation, graphitized carbon solid phase extraction (SPE) cleanup, and ion chromatography-tandem mass spectrometry (IC-MS/MS) analysis. A Waters IC-Pak Anion HR column (4.6 mm × 75 mm) was eluted with 100 mM ammonium acetate in 50:50 (v/v) acetonitrile/water mobile phase at a rate of 0.35 ml/min. A triple stage quadrupole mass spectrometer, equipped with electrospray ionization (ESI) in the negative ion mode, was used to detect perchlorate anion. An ¹⁸O₄-labeled perchlorate anion internal standard was used to correct for any matrix effects. The method limit of quantitation (LOQ) was: 1.0 μg/kg in fruits, vegetables, and infant foods; 3.0 μg/kg in dry products. Fortified test portions gave 80-120% recoveries. Determination of incurred perchlorate anion residues agreed well with results for comparable commodities or products analyzed by published methods.     

A single sorbent for tetracycline enrichment and subsequent solid-matrix time-resolved luminescence

The aim of this study was to search for a sorbent that could act as an extraction phase and as a support for solid-matrix time-resolved luminescence (SMTRL). Four potential sorbents were investigated for this purpose using tetracycline (TC) as a model analyte. Sorbents prepared from C18 silica gel or calcium cross-linked pectin gel were able to extract TC from dilute solutions. Europium(III)-TC complex adsorbed on the surface of C18 generated the most intense TRL signal when measured at λ_ex = 388 nm and λ_em = 615 nm. This method achieved a 1 ng/ml limit of detection (LOD) with a 100 μl sample solution in a repeated spotting mode. Hyphenation of sorbent extraction and SMTRL was demonstrated using C18. This method is suitable for screening of TC in foods or aqueous solutions and can be extended to other luminescent lanthanide-chelating analytes in physiological or environmental samples.     

Simultaneous determination of cotinine and trans-3'-hydroxycotinine in human serum by high-performance liquid chromatography.

A high-performance liquid chromatographic method with ultraviolet photometric detection has been developed for the quantitation of cotinine and trans-3'-hydroxycotinine in human serum. A solid-phase extraction procedure was performed for the analytes and the internal standard, N-ethylnorcotinine, before chromatography. The use of a 30-cm reversed-phase column and a mobile phase of water-methanol-0.1 M sodium acetate-acetonitrile (67:24.5:6.5:2, v/v), pH 4.3, prevented the co-elution of caffeine with cotinine. The limit of quantitation observed with this method was 5 ng/ml for both cotinine and trans-3'-hydroxycotinine. The present method proved useful for the determination of serum levels of these metabolites, correlating with nicotine daily intake.     

Determination of ethambutol by ion-pair reversed phase liquid chromatography with UV detection

An ion-pair reversed phase liquid chromatography method for the antituberculosis drug ethambutol hydrochloride was developed using sodium 1-heptanesulfonate (4.0 mg/ml) as an ion-pairing (IP) reagent. To enable detection of the ethambutol with a UV detector without sample pretreatment, the pH 4.5 aqueous tetrahydrofuran (THF) (25%, v/v) mobile phase contained 1.0 mM Cu(II), which forms a UV-absorbing complex with the analyte. At a column temperature of 35 °C, ethambutol gives a symmetrical peak with a retention time of 5 min. Chromatographic conditions were optimized through study of the effects of mobile phase composition and pH, Cu(II) and IP reagent concentration, and column temperature. The method is shown to be simple, precise, efficient, robust, linear up to at least 0.25 mg/ml, and to have a limit of quantitation of 6 μg/ml.     

Determination of ethyl glucuronide in urine using reversed-phase HPLC and pulsed electrochemical detection (Part II)

A direct, versatile method for the determination of ethyl glucuronide (EtG), a biomarker of ethanol consumption, in urine has been developed using reversed-phase liquid chromatography with pulsed electrochemical detection (PED). EtG and methyl glucuronide (MetG), which serves as an internal standard, are readily separated using a mobile phase consisting of 1% acetic acid/acetonitrile (98/2, v/v). Post-column addition of NaOH allows for the detection of all glucuronides using PED at a gold working electrode. Upon optimization, EtG was found to have a limit of detection of 0.03 μg/mL (7 pmol; 50 μL injection volume) and repeatability at the limit of quantitation of 1.7%R.S.D. (relative standard deviation). Solid-phase extraction (SPE) using an aminopropyl phase was used to remove interferents in urine samples prior to their analysis. Compound recovery following SPE was approximately 50 ± 2%. The forensic utility of this method was further validated by the analysis of 29 post-mortem urine specimens, whose results agreed strongly with certified determinations.     

An automated method for the simultaneous determination of pravastatin, 3-hydroxy isomeric metabolite, pravalactone and fenofibric acid in human plasma by sensitive liquid chromatography combined with diode array and tandem mass spectrometry detection

In this study, a sensitive and selective method based on liquid chromatography combined with diode array and tandem mass spectrometry detection (LC-DAD-MS/MS) was developed for the simultaneous quantitative determination of fenofibric acid, pravastatin and its main metabolites in human plasma. In this method, an automated solid-phase extraction (SPE) on disposable extraction cartridges (DECs) is used to isolate the compounds from the biological matrix and to prepare a cleaner sample before injection and analysis in the LC-DAD-MS/MS system. On-line LC-DAD-MS/MS system using an atmospheric pressure ionization (TurboIonSpray) was then developed for the simultaneous determination of pravastatin, 3-hydroxy isomeric metabolite (3-OH metab), pravalactone and fenofibric acid. The separation is obtained on an endcapped dodecyl silica based stationary phase using a mobile phase consisting of a mixture of acetonitrile, methanol and 5mM ammonium acetate solution (30:30:40, v/v/v). Sulindac and triamcinolone were used as internal standards (ISs). The detection of the fenofibric acid and sulindac was achieved by means of a DAD system. The MS/MS ion transitions monitored were m/z 442.2-->269.1, 442.2-->269.1, 424.3-->183.0 and 435.2-->397.2 for pravastatin, 3-OH metab, pravalactone and triamcinolone, respectively. The method was validated regarding stability, selectivity, extraction efficiency, response function, trueness, precision lower limit of quantitation and matrix effect. The limits of quantitation (LOQs) were around 0.50 ng/ml for pravastatin, 0.25 ng/ml for 3-OH metab, 0.05 ng/ml for pravalactone and 0.25 microg/ml for fenofibric acid.     

Analysis of sediment-associated insecticides using ultrasound assisted microwave extraction and gas chromatography-mass spectrometry

An ultrasound assisted microwave extraction (UAME) method was developed to simultaneously extract five organophosphate (OP) and eight pyrethroid insecticides from sediment. The optimized UAME conditions were to use 100 ml of a mixture of hexane and acetone (1:1, v/v) solution as the extraction solvents, and extraction time, microwave and ultrasonic power settings of 6 min, 100 W and 50 W, respectively. Extracts were cleaned using solid phase extraction and analyzed by gas chromatography-mass spectrometry in negative chemical ionization mode and quantification was based on matrix-matched standard solutions along with internal standard calibration. At the spiked concentrations of 1, 5 and 20 ng/g dry weight (dw), recoveries of OPs were 77.6-122%, 65.2-128% and 75.6-141% with relative standard deviations (RSDs) of 10.6-18.1%, 3.1-12.5% and 8.0-35.3%, respectively, while recoveries of pyrethroids were 78.0-101%, 76.4-104% and 71.0-99.5% with RSDs of 10.3-23.5%, 4.7-17.6% and 8.8-18.7%, respectively. Method detection limits ranged from 0.31 to 0.45 ng/g dw for the OP insecticides and from 0.27 to 0.70 ng/g dw for the pyrethroid insecticides. The newly developed UAME method was validated by comparing it to Soxhlet and sonication extraction methods. Better recoveries were achieved for most OPs by the novel UAME method, whereas there was no significant difference in recoveries for most of the pyrethroids. Finally, the UAME method was used to quantify the target insecticides in field-contaminated sediment samples which were collected in Guangzhou, China.     

Part-per-trillion determination of chlorobenzenes in water using dispersive liquid-liquid microextraction combined gas chromatography-electron capture detection

In this study, a simple, rapid and efficient method, dispersive liquid-liquid microextraction (DLLME) combined gas chromatography-electron capture detection (GC-ECD), for the determination of chlorobenzenes (CBs) in water samples, has been described. This method involves the use of an appropriate mixture of extraction solvent (9.5 μl chlorobenzene) and disperser solvent (0.50 ml acetone) for the formation of cloudy solution in 5.00 ml aqueous sample containing analytes. After extraction, phase separation was performed by centrifugation and the enriched analytes in sedimented phase were determined by gas chromatography-electron capture detection (GC-ECD). Our simple conditions were conducted at room temperature with no stiring and no salt addition in order to minimize sample preparation steps. Parameters such as the kind and volume of extraction solvent, the kind and volume of disperser solvent, extraction time and salt effect, were studied and optimized. The method exhibited enrichment factors and recoveries ranging from 711 to 813 and 71.1 to 81.3%, respectively, within very short extraction time. The linearity of the method ranged from 0.05 to 100 μg l⁻¹ for dichlorobenzene isomers (DCB), 0.002-20 μg l⁻¹ for trichlorobenzene (TCB) and tetrachlorobenzene (TeCB) isomers and from 0.001 to 4 μg l⁻¹ for pentachlorobenzene (PeCB) and hexachlorobenzene (HCB). The limit of detection was in the low μg l⁻¹ level, ranging between 0.0005 and 0.05 μg l⁻¹. The relative standard deviations (R.S.D.s) for the concentration of DCB isomers, 5.00 μg l⁻¹, TCB and TeCB isomers, 0.500 μg l⁻¹, PeCB and HCB 0.100 μg l⁻¹ in water by using the internal standard were in the range of 0.52-2.8% (n = 5) and without the internal standard were in the range of 4.6-6.0% (n = 5). The relative recoveries of spiked CBs at different levels of chlorobenzene isomers in tap, well and river water samples were 109-121%, 105-113% and 87-120%, respectively. It is concluded that this method can be successfully applied for the determination of CBs in tap, river and well water samples.