Automated on-line in-tube solid-phase microextraction followed by liquid chromatography/electrospray ionization-mass spectrometry for the determination of chlorinated phenoxy acid herbicides in environmental waters

A method for the determination of six chlorinated phenoxy acid herbicides in river water was developed using in-tube solid-phase microextraction (SPME) followed by liquid chromatography/electrospray ionization-mass spectrometry (LC/ESI-MS). In-tube SPME is an extraction technique for organic compounds in aqueous samples, in which analytes are extracted from a sample directly into an open tubular capillary by repeated draw/eject cycles of the sample solution. Simple mass spectra with strong signals corresponding to [M-H]- and [M-RCOOH]- were observed for all herbicides tested in this study. The best separation of these compounds was obtained with a C18 column using linear gradient elution with a mobile phase of acetonitrile-water containing 5 mmol l-1 dibutylamine acetate (DBA). To optimize the extraction of herbicides, several in-tube SPME parameters were examined. The optimum extraction conditions were 25 draw/eject cycles of 30 microliters of sample in 0.2% formic acid (pH 2) at a flow rate of 200 microliters min-1 using a DB-WAX capillary. The herbicides extracted by the capillary were easily desorbed by 10 microliters acetonitrile. Using in-tube SPME-LC/ESI-MS with time-scheduled selected ion monitoring, the calibration curves of herbicides were linear in the range 0.05-50 ng ml-1 with correlation coefficients above 0.999. This method was successfully applied to the analysis of river water samples without interference peaks. The limit of quantification was in the range 0.02-0.06 ng ml-1 and the limit of detection (S/N = 3) was in the range 0.005-0.03 ng ml-1. The repeatability and reproducibility were in the range 2.5-4.1% and 6.2-9.1%, respectively.     

Automated sample preparation using in-tube solid-phase microextraction and its application -- a review

Sample preparation, such as extraction, concentration, and isolation of analytes, greatly influences their reliable and accurate analysis. In-tube solid-phase microextraction (SPME) is a new effective sample preparation technique using an open tubular fused-silica capillary column as an extraction device. Organic compounds in aqueous samples are directly extracted and concentrated into the stationary phase of capillary columns by repeated draw/eject cycles of sample solution, and they can be directly transferred to the liquid chromatographic column. In-tube SPME is an ideal sample preparation technique because it is fast to operate, easy to automate, solvent-free, and inexpensive. On-line in-tube SPME-performed continuous extraction, concentration, desorption, and injection using an autosampler, is usually used in combination with high performance liquid chromatography and liquid chromatography-mass spectrometry. This technique has successfully been applied to the determination of various compounds such as pesticides, drugs, environmental pollutants, and food contaminants. In this review, an overview of the development of in-tube SPME technique and its applications to environmental, clinical, forensic, and food analyses are described.     

Simultaneous determination of testosterone, cortisol, and dehydroepiandrosterone in saliva by stable isotope dilution on-line in-tube solid-phase microextraction coupled with liquid chromatography–tandem mass spectrometry

We have developed a simple and sensitive method for the simultaneous determination of testosterone (TES), cortisol (CRT), and dehydroepiandrosterone (DHEA) in saliva by automated online in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–tandem mass spectrometry (LC–MS/MS) using a Discovery HS F5 column. The optimum in-tube SPME conditions were 25 draw/eject cycles of 40 μL of sample at a flow rate of 200 μL/min using a Supel-Q PLOT capillary column as an extraction device. The extracted compounds were easily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. The in-tube SPME LC–MS/MS method showed good linearity with correlation coefficients r?≥?0.9998 for TES, CRT, and DHEA using their respective stable isotope-labeled internal standards. The intra-day and inter-day precisions (relative standard deviations) were below 4.9 and 8.5 % (n?=?5), respectively. This method was successfully utilized to analyze TES, CRT, and DHEA in saliva samples without any other pretreatment or interference peaks, and the quantification limits (S/N?=?10) of TES, CRT and DHEA were about 0.01, 0.03 and 0.29 ng/mL saliva, respectively. The recoveries of these compounds spiked into saliva samples were each above 94 %. This method was applied to analyze changes in salivary TES, CRT, and DHEA levels resulting from stress and fatigue load.     

Automated analysis of lidocaine and its metabolite in plasma by in-tube solid-phase microextraction coupled with LC-UV for pharmacokinetic study

A sensitive, selective, and reproducible in-tube solid-phase microextraction and liquid chromatographic (in-tube SPME/LC-UV) method for determination of lidocaine and its metabolite monoethylglycinexylidide (MEGX) in human plasma has been developed, validated, and further applied to pharmacokinetic study in pregnant women with gestational diabetes mellitus (GDM) subjected to epidural anesthesia. Important factors in the optimization of in-tube SPME performance are discussed, including the draw/eject sample volume, draw/eject cycle number, draw/eject flow rate, sample pH, and influence of plasma proteins. The limits of quantification of the in-tube SPME/LC method were 50 ng/mL for both metabolite and lidocaine. The interday and intraday precision had coefficients of variation lower than 8%, and accuracy ranged from 95 to 117%. The response of the in-tube SPME/LC method for analytes was linear over a dynamic range from 50 to 5000 ng/mL, with correlation coefficients higher than 0.9976. The developed in-tube SPME/LC method was successfully used to analyze lidocaine and its metabolite in plasma samples from pregnant women with GDM subjected to epidural anesthesia for pharmacokinetic study.     

Determination of fluoroquinolones in environmental waters by in-tube solid-phase microextraction coupled with liquid chromatography-tandem mass spectrometry

We developed a sensitive and useful method for the determination of five fluoroquinolones (FQs), enoxacin, ofloxacin, ciprofloxacin, norfloxacin, and lomefloxacin in environmental waters, using a fully automated method consisting of in-tube solid-phase microextraction (SPME) coupled with liquid chromatography-tandem mass spectrometry (LC/MS/MS). These compounds were analysed within 7 min by high-performance liquid chromatography (HPLC) using a CAPCELL PAK C8 column and aqueous ammonium formate (pH 3.0, 5 mM)/acetonitrile (85/15, v/v) at a flow rate of 0.2 mL/min. Electrospray ionization conditions in the positive ion mode were optimized for MS/MS detection. In order to optimize the extraction of FQs, several in-tube SPME parameters were examined. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 μL of sample at a flow-rate of 150 μL/min, using a Carboxen 1010 PLOT capillary column as an extraction device. The extracted compounds were easily desorbed from the capillary by passage of the mobile phase. Using the in-tube SPME LC/MS/MS method, good linearity of the calibration curve (r ≥ 0.997) was obtained in the concentration range from 0.1 to 10 ng/mL for all compounds examined. The limits of detection (S/N = 3) of the five FQs ranged from 7 to 29 pg/mL. The in-tube SPME method showed 60-94-fold higher sensitivity than the direct injection method (5 μL injection). This method was applied successfully to the analysis of environmental water samples without any other pretreatment and interference peaks. Several surface waters and wastewaters were collected from the area around Asahi River, and ofloxacin was detected in wastewater samples of a sewage treatment plant and other two hospitals at 17.5-186.2 pg/mL. The recoveries of FQs spiked into river water were above 81% for a 0.1 or 0.2 ng/mL spiking concentration, and the relative standard deviations were below 1.9-8.6%.     

Fully automated analysis of estrogens in environmental waters by in-tube solid-phase microextraction coupled with liquid chromatography-tandem mass spectrometry

A simple, rapid and sensitive method for the determination of five estrogens, estrone, 17beta-estradiol, estriol, ethynyl estradiol, and diethylstilbestrol, was developed using a fully automated method consisting of in-tube solid-phase microextraction (SPME) coupled with liquid chromatography-tandem mass spectrometry (LC/MS/MS). These estrogens were separated within 8 min by HPLC using an XDB-C8 column and 0.01% ammonia/acetonitrile (60/40, v/v) at a flow rate of 0.2 mL/min. Electrospray ionization conditions in the negative ion mode were optimized for MS/MS detection of the estrogens. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 microL of sample using a Supel-Q PLOT capillary column as an extraction device. The extracted compounds were easily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. Using the in-tube SPME LC/MS/MS method, good linearity of the calibration curve (r > or = 0.9996) was obtained in the concentration range from 10 to 200 pg/mL for all compounds examined. The limits of detection (S/N= 3) of the five estrogens examined ranged from 2.7 to 11.7 pg/mL. The in-tube SPME method showed 34-90-fold higher sensitivity than the direct injection method (5 microL injection). This method was applied successfully to the analysis of environmental water samples without any other pretreatment and interference peaks. Several surface water and wastewater samples were collected from the area around Asahi River, and estriol was detected at 35.7 pg/mL in the effluent of a sewage treatment plant. The recoveries of estrogens spiked into river waters were above 86%, except for estriol, and the relative standard deviations were below 0.9-8.8%.     

Determination of fluoxetine and norfluoxetine enantiomers in human plasma by polypyrrole-coated capillary in-tube solid-phase microextraction coupled with liquid chromatography-fluorescence detection

A sensitive, selective, and reproducible in-tube polypyrrole-coated capillary (PPY) solid-phase microextraction and liquid chromatographic method for fluoxetine and norfluoxetine enantiomers analysis in plasma samples has been developed, validated, and further applied to the analysis of plasma samples from elderly patients undergoing therapy with antidepressants. Important factors in the optimization of in-tube SPME efficiency are discussed, including the sample draw/eject volume, draw/eject cycle number, draw/eject flow-rate, sample pH, and influence of plasma proteins. Separation of the analytes was achieved with a Chiralcel OD-R column and a mobile phase consisting of potassium hexafluorophosphate 7.5 mM and sodium phosphate 0.25 M solution, pH 3.0, and acetonitrile (75:25, v/v) in the isocratic mode, at a flow rate of 1.0 mL/min. Detection was carried out by fluorescence absorbance at Ex/Em 230/290 nm. The multifunctional porous surface structure of the PPY-coated film provided high precision and accuracy for enantiomers. Compared with other commercial capillaries, PPY-coated capillary showed better extraction efficiency for all the analytes. The quantification limits of the proposed method were 10 ng/mL for R- and S-fluoxetine, and 15 ng/mL for R- and S-norfluoxetine, with a coefficient of variation lower than 13%. The response of the method for enantiomers is linear over a dynamic range, from the limit of quantification to 700 ng/mL, with correlation coefficients higher than 0.9940. The in-tube SPME/LC method can therefore be successfully used to analyze plasma samples from ageing patients undergoing therapy with fluoxetine.     

Determination of polycyclic aromatic hydrocarbons in food samples by automated on-line in-tube solid-phase microextraction coupled with high-performance liquid chromatography-fluorescence detection

A simple and sensitive automated method, consisting of in-tube solid-phase microextraction (SPME) coupled with high-performance liquid chromatography-fluorescence detection (HPLC-FLD), was developed for the determination of 15 polycyclic aromatic hydrocarbons (PAHs) in food samples. PAHs were separated within 15 min by HPLC using a Zorbax Eclipse PAH column with a water/acetonitrile gradient elution program as the mobile phase. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 μL of sample using a CP-Sil 19CB capillary column as an extraction device. Low- and high-molecular weight PAHs were extracted effectively onto the capillary coating from 5% and 30% methanol solutions, respectively. The extracted PAHs were readily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. Using the in-tube SPME HPLC-FLD method, good linearity of the calibration curve (r > 0.9972) was obtained in the concentration range of 0.05–2.0 ng/mL, and the detection limits (S/N = 3) of PAHs were 0.32–4.63 pg/mL. The in-tube SPME method showed 18–47 fold higher sensitivity than the direct injection method. The intra-day and inter-day precision (relative standard deviations) for a 1 ng/mL PAH mixture were below 5.1% and 7.6% (n = 5), respectively. This method was applied successfully to the analysis of tea products and dried food samples without interference peaks, and the recoveries of PAHs spiked into the tea samples were >70%. Low-molecular weight PAHs such as naphthalene and pyrene were detected in many foods, and carcinogenic benzo[a]pyrene, at relatively high concentrations, was also detected in some black tea samples. This method was also utilized to assess the release of PAHs from tea leaves into the liquor.     

Determination of stimulants in human urine and hair samples by polypyrrole coated capillary in-tube solid phase microextraction coupled with liquid chromatography-electrospray mass spectrometry

A simple and sensitive method for the determination of amphetamine, methamphetamine and their methylenedioxy derivatives in urine and hair samples was developed by coupling automated in-tube solid phase microextraction (SPME) to high performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ES-MS). To achieve optimum performance, the conditions for both the in-tube SPME and the ES-MS detection were investigated. ES-MS detection conditions were studied by flow injection analysis (FIA) with direct liquid injection. In-tube SPME conditions were optimized by selecting the appropriate extraction parameters, including capillary stationary phases and sample pH. For the compounds studied, a custom-made polypyrrole (PPY) coated capillary showed superior extraction efficiency as compared to commercial capillaries. Therefore, the PPY coated capillary was selected for in-tube SPME in this study. The calibration curves of stimulants were linear in the range from 0.1 to 100 ng ml(-1) with detection limits (S/N=3) of 8-56 ng l(-1). This method was successfully applied to the analysis of the stimulants in spiked human urine and hair samples.     

Bio-compatible in-tube solid-phase microextraction capillary for the direct extraction and high-performance liquid chromatographic determination of drugs in human serum

A restricted access material (RAM), alkyl-diol-silica (ADS), was used to prepare a highly bio-compatible solid-phase microextraction (SPME) capillary for the automated and direct in-tube extraction of several benzodiazepines from human serum. The bifunctionality of the ADS extraction phase prevented fouling of the capillary by protein adsorption while simultaneously trapping the analytes in the hydrophobic porous interior. This the first report of a restricted access material utilized as an extraction phase for in-tube SPME. The approach simplified the required apparatus in comparison to existing RAM column switching procedures, and more importantly eliminated the excessive use of extraction solvents. The biocompatibility of the ADS material also overcame the existing problems with in-tube SPME that requires an ultrafiltration or other deproteinization step prior to handling biological samples, therefore further minimizing the sample preparation requirements. The calculated oxazepam, temazepam, nordazepam and diazepam detection limits were 26, 29, 22 and 24 ng/ml in serum, respectively. The method was linear over the range of 50-50 000 ng/ml with an average linear coefficient (R2) value of 0.9998. The injection repeatability and intra-assay precision of the method were evaluated with five injections of a 10-microg/ml serum sample (spiked with all compounds), resulting in an average RSD<7%. The ADS extraction column was robust, providing many direct injections of biological fluids for the extraction and subsequent determination of benzodiazepines.     

Analysis of polar pesticides in water and wine samples by automated in-tube solid-phase microextraction coupled with high-performance liquid chromatography-mass spectrometry

A simple and sensitive method for the determination of polar pesticides in water and wine samples was developed by coupling automated in-tube solid-phase microextraction (SPME) to high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS). To achieve optimum performance, the conditions for both the in-tube SPME and the ESI-MS detection were investigated. In-tube SPME conditions were optimized by selecting the appropriate extraction parameters, especially the stationary phases used for SPME. For the compounds studied, a custom-made polypyrrole (PPY)-coated capillary showed superior extraction efficiency as compared to several commercial capillaries tested, and therefore, it was selected for in-tube SPME. The influence of the ethanol content on the performance of in-tube SPME was also investigated. It was found that the amount of pesticides extracted decreased with the increase of ethanol content in the solutions. The ESI-MS detection conditions were optimized as follows: nebulizer gas, N2 (30 p.s.i.; 1 p.s.i.=6894.76 Pa); drying gas, N2 (10 l/min, 350 degrees C); capillary voltage, 4500 V; ionization mode, positive; mass scan range, 50-350 amu; fragmentor voltage, variable depending on the ions selected. Due to the high extraction efficiency of the PPY coating and the high sensitive mass detection, the detection limits (S/N = 3) of this method for the compounds studied are in the range of 0.01 to 1.2 ng/ml, which are more than one order of magnitude lower than those of the previous in-tube SPME-HPLC-UV method. A linear relationship was obtained for each analyte in the concentration range of 0.5 to 200 ng/ml with MS detection. This method was applied to the analysis of phenylurea and carbamate pesticides in spiked water and wine samples.     

Biocompatible in-tube solid phase microextraction coupled with liquid chromatography-fluorescence detection for determination of interferon α in plasma samples

The present work demonstrates the successful application of automated biocompatible in-tube solid-phase microextraction coupled with liquid chromatography (in-tube SPME/LC) for determination of interferon alpha(2a) (IFN α(2a)) in plasma samples for therapeutic drug monitoring. A restricted access material (RAM, protein-coated silica) was employed for preparation of a lab-made biocompatible in-tube SPME capillary that enables the direct injection of biological fluids as well as the simultaneous exclusion of macromolecules by chemical diffusion barrier and drug pre-concentration. The in-tube SPME variables, such as sample volume, draw/eject volume, number of draw-eject cycles, and desorption mode were optimized, to improve the sensitivity of the proposed method. The IFN α(2a) analyses in plasma sample were carried out within 25min (sample preparation and LC analyses). The response of the proposed method was linear over a dynamic range, from 0.06 to 3.0MIUmL(-1), with correlation coefficient equal to 0.998. The interday precision of the method presented coefficient of variation lower than 8%. The proposed automated method has adequate analytical sensitivity and selectivity for determination of IFN α(2a) in plasma samples for therapeutic drug monitoring.     

Optimisation of an in-tube solid phase microextraction method coupled with HPLC for determination of some oestrogens in environmental liquid samples using different capillary columns

A simple on-line method for simultaneous determination of some oestrogens including oestriol (E3), norethisterone (NORE), ethynylestradiol (EE2), D-norgestrel (NORG) and bisphenol A (BPA), in environmental liquid samples was developed by coupling in-tube solid phase microextraction (in-tube SPME) to high-performance liquid chromatography with diode array (DAD) and fluorescence (FLD) detectors. Two capillary chromatographic columns (Supel-Q? and Carboxen? 1006 porous layer open tubular) were selected to develop this method. To achieve optimum extraction performance, several parameters were investigated including number of draw/eject cycles and the sample volume for each of the columns. Reproducibility was satisfactory for inter- and intra-day precision, yielding % RSDs of less than 10% and 7.6%, respectively. Limits of detection (LODs) and quantification (LOQs) for the proposed method using a DAD detector were achieved in the ranges of 0.04–0.63?ng?mL^?1 and 0.12–1.9?ng?mL^?1, depending of the capillary column used. Fluorescence detection improved these parameters for E3, BPA and EE2, obtaining LODs of 0.005–0.03?ng?mL^?1 and LOQs of 0.015–0.08?ng?mL^?1 using Supel-Q and LODs of 0.01–0.015?ng?mL^?1 and LOQs of 0.025–0.04?ng?mL^?1 using Carboxen. The proposed method was successfully applied to spiked environmental waters obtaining recoveries greater than 80%.     

Biomolecules and Nutritional Quality of Soymilk Fermented with Probiotic Yeast and Bacteria

Soymilk was fermented with five isolates of probiotic lactic acid bacteria and in combination with probiotic yeast Saccharomyces boulardii. Nutritional profile like fat, protein, ash, pH, acidity, polyphenol, and protein hydrolysis were analyzed. Polyphenol content decreased from 265.88 to 119 microg/ml with different cultures. Protein hydrolysis ranged from 2.46 to 2.83 mmol l(-1) with different cultures. The antioxidant activity was assessed using different methods like 1, 1-diphenyl-2-picrylhydrazyl free radical-scavenging assay, inhibition of ascorbate autoxidation, and measurement of reducing activity. The activities varied with the starters used but, nevertheless, were significantly higher than those found in unfermented soymilk. Bioconversion of the isoflavone glucosides (daidzin + genistin) into their corresponding bioactive aglycones (daidzein + genistein) was observed during soymilk fermentation. Total glucosides in soyamilk were 26.35 mg/100 ml. In contrast, aglycones genistein and daidzein were quantitatively lesser accounting 2.91 mg/100 ml (genistein 1.17 mg/100 ml and daidzein 1.19 mg/100 ml). Soymilk fermented with probiotic cultures resulted in the reduction of glycosides ranging from 0.40 mg to 1.36 mg/100 ml and increase in aglycones ranging from 6.32 mg to 13.66 mg/100 ml.     

Determination of patulin in fruit juice and dried fruit samples by in-tube solid-phase microextraction coupled with liquid chromatography–mass spectrometry

A simple and sensitive method for the determination of patulin in fruit juice and dried fruit samples was developed using a fully automated method consisting of in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–mass spectrometry (LC–MS). Patulin was separated within 5 min by high-performance liquid chromatography using a Synergi MAX-RP 80A column and water/acetonitrile (80/20, v/v) as the mobile phase. Electrospray ionization conditions in the negative ion mode were optimized for MS detection of patulin. The pseudo-molecular ion [M−H]⁻ was used to detect patulin in selected ion monitoring (SIM) mode. The optimum in-tube SPME conditions were 25 draw/eject cycles of 40 μL of sample using a Carboxen 1006 PLOT capillary column as an extraction device. The extracted patulin was readily desorbed from the capillary by passage of the mobile phase, and no carry-over was observed. Using the in-tube SPME LC–MS with SIM method, good linearity of the calibration curve (r = 0.9996) was obtained in the concentration range of 0.5–20 ng/mL using ¹³C₃-patulin as an internal standard, and the detection limit (S/N = 3) of patulin was 23.5 pg/mL. The in-tube SPME method showed >83-fold higher sensitivity than the direct injection method (10 μL injection volume). The within-day and between-day precision (relative standard deviations) were below 0.8% and 5.0% (n = 6), respectively. This method was applied successfully for the analysis of fruit juice and dried fruit samples without interference peaks. The recoveries of patulin spiked into apple juice were >92%, and the relative standard deviations were <4.5%. Patulin was detected at ng/mL levels in various commercial apple juice samples.     

Determination of aflatoxins in food samples by automated on-line in-tube solid-phase microextraction coupled with liquid chromatography–mass spectrometry

A simple and sensitive automated method for determination of aflatoxins (B1, B2, G1, and G2) in nuts, cereals, dried fruits, and spices was developed consisting of in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–mass spectrometry (LC–MS). Aflatoxins were separated within 8 min by high-performance liquid chromatography using a Zorbax Eclipse XDB-C8 column with methanol/acetonitrile (60/40, v/v): 5 mM ammonium formate (45:55) as the mobile phase. Electrospray ionization conditions in the positive ion mode were optimized for MS detection of aflatoxins. The pseudo-molecular ions [M+H]⁺ were used to detect aflatoxins in selected ion monitoring (SIM) mode. The optimum in-tube SPME conditions were 25 draw/eject cycles of 40 μL of sample using a Supel-Q PLOT capillary column as an extraction device. The extracted aflatoxins were readily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. Using the in-tube SPME LC–MS with SIM method, good linearity of the calibration curve (r > 0.9994) was obtained in the concentration range of 0.05–2.0 ng/mL using aflatoxin M1 as an internal standard, and the detection limits (S/N = 3) of aflatoxins were 2.1–2.8 pg/mL. The in-tube SPME method showed >23-fold higher sensitivity than the direct injection method (10 μL injection volume). The within-day and between-day precision (relative standard deviations) at the concentration of 1 ng/mL aflatoxin mixture were below 3.3% and 7.7% (n = 5), respectively. This method was applied successfully to analysis of food samples without interference peaks. The recoveries of aflatoxins spiked into nuts and cereals were >80%, and the relative standard deviations were <11.2%. Aflatoxins were detected at <10 ng/g in several commercial food samples.     

In-tube solid-phase microextraction with poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary for direct high-performance liquid chromatographic determination of ketamine in urine samples

Ketamine was used for anaesthesia originally but has emerged as an abused drug in recent years. The prevalence of ketamine abuse demands a direct and rapid determination method. It is known that in-tube solid phase microextraction (in-tube SPME) can perform extraction with a capillary linked directly to a HPLC system, providing an automated and accurate extraction procedure. In this paper, an in-tube SPME coupled to HPLC method was developed for the determination of ketamine in urine samples with a poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary column as the extraction phase, which is expected to provide higher extraction efficiency than open tubular capillaries. After optimizing the extraction conditions, ketamine was extracted directly from urine samples in a wide dynamic linear range of 50-10,000 ng mL(-1), with the detection limit obtained as 6.4 ng mL(-1). The intra-day and inter-day precision for the method was 1.6% and 1.7%, respectively. The urine samples from suspect addicts have been successfully analyzed within 20 min. The re-usability of the monolithic column was also confirmed as no decrease of the extraction efficiency was shown after urine extraction.     

Preparation and evaluation of hydroxylated poly(glycidyl methacrylate-co-ethylene dimethacrylate) monolithic capillary for in-tube solid-phase microextraction coupled to high-performance liquid chromatography

A hydroxylated poly(glycidyl methacrylate-co-ethylene dimethacrylate) (GMA-co-EDMA) monolithic capillary was prepared and investigated for in-tube solid-phase microextraction (SPME). The polymer monolith was synthesized by in-situ polymerization of GMA and EDMA in the presence of dodecanol and toluene as the mixed porogenic solvents. After polymerization, glycidyl groups were hydrolyzed with sulfuric acid to produce diol groups at the surface of the porous monolith. To investigate the extraction mechanism, several groups of model analytes (including neutral, acidic and basic) were selected to perform extractions. The resulting monolith showed high extraction selectivity towards polar compounds, which resulted from the enhancement of dipole-dipole and hydrogen bonding interactions relative to hydrophobic interactions. The equilibrium extraction time profiles were also monitored for those model compounds to assess the extraction capacity of the monolithic capillary. Moreover, the hydroxylated poly(GMA-co-EDMA) monolithic capillary exhibited satisfactory reproducibility and stability. Finally, the in-tube SPME-HPLC method, based on the developed monolithic capillary as the extraction media, was successfully applied to the determination of five polar organic contaminants in lake water.     

Quantitative analysis of isoflavone aglycones in human serum by solid phase extraction and liquid chromatography-tandem mass spectrometry

This paper describes a liquid chromatography-electrospray-tandem mass spectrometry (LC-ESI-MS/MS) for the qualitative and quantitative analysis of three isoflavone aglycones (glycitein, daidzein and genistein) in human serum. Positive ion mode was used for the detection of these compounds and selective reaction monitoring (SRM) was employed for quantitative measurement. The SRM transitions monitored were as 285.0 → 242.0, 270.0 for glycitein, 255.0 → 137.0, 153.0, 181.0, 199.0 for daidzein and 271.0 → 153.0, 215.0 for genistein. d₃-Daidzein was used as an internal standard for quantitative measurement. The linearity was good from 0.5 to 500 ng/ml. The detection limit based on a signal-to-noise ratio of three was 0.27, 0.38 and 0.29 ng/ml for glycitein, daidzein and genistein, respectively. A newly developed solid phase extraction (SPE) procedure was developed for sample pre-treatment. Good recovery, 92.3-103.2%, for three isoflavone aglycones were obtained. This newly developed method was successfully applied to evaluate isoflavone pharmacokinetic in human serum after oral administration.     

管内硼亲和固相微萃取-高效液相色谱全自动在线联用检测茶饮料中的顺式二羟基化合物

自动化联用分析技术对于降低人力强度、提高效率和保证数据重现性等具有重要意义。硼亲和固相微萃取（BA-SPME）是近十年出现的用于富集顺式二羟基化合物的独特工具,但BA-SPME与高效液相色谱（HPLC）的自动化在线联用还未见报道。该文报道了一种新颖的管内BA-SPME-HPLC全自动在线联用方法,用于分析茶饮料中的顺式二羟基化合物。该自动化在线联用方法利用自动进样器通过六通阀的切换实现流路连接。制备了管内BA-SPME毛细管,考察了涂层柱的柱容量,并对其形貌进行了表征,考察并优化了影响实际样品分离效果的因素。最后,利用该联用方法对3种不同品牌的茶饮料进行了分析,并对沏茶温度对茶水中顺式二羟基化合物含量的影响进行了评价。