Headspace liquid-phase microextraction of methamphetamine and amphetamine in urine by an aqueous drop

This study developed a headspace liquid-phase microextraction (LPME) method by using a single aqueous drop in combination with high performance liquid chromatography (HPLC)-UV detection for the determination of methamphetamine (MAP) and amphetamine (AP) in urine samples. The analytes, volatile and basic, were released from sample matrix into the headspace first, and then protonated and dissolved in an aqueous H₃PO₄ drop hanging in the headspace by a HPLC syringe. After extraction, this drop was directly injected into HPLC. Parameters affecting extraction efficiency were investigated and optimized. This method showed good linearity in the investigated concentration range of 1.0-1500 μg L⁻¹, repeatability of the extraction (R.S.D. < 5%, n = 6), and low detection limits (0.3 μg L⁻¹ for both analytes). Enrichment factors of about 400-fold and 220-fold were achieved for MAP and AP, respectively, at optimum conditions. The feasibility of the method was demonstrated by analyzing human urine samples.     

Determination of anti‐malaria agent chloroquine using single drop liquid‐liquid‐liquid microextraction

A simple, sensitive, and inexpensive single drop liquid‐liquid‐liquid microextraction combined with isocratic RP‐HPLC and UV detection was developed for the determination of anti‐malaria drug, chloroquine. The target compound was extracted from alkaline aqueous sample solution (adjusted to 0.5 mol/L sodium hydroxide) through a thin layer of organic solvent membrane and back‐extracted to an acidic acceptor drop (adjusted to 0.02 mol/L phosphoric acid) suspended on the tip of a 25 μL HPLC syringe in the organic layer. This syringe was also used for direct injection after extraction. The linear range was 1–200 μg/L. The LOD and LOQ were 0.3 and 1.0 μg/L, respectively. Intra‐and inter‐day precisions were less than 2.0 and 2.3%, respectively. The real samples were successfully analyzed using the proposed method. The recoveries of spiked samples were more than 94.6%.     

Application of static and dynamic liquid-phase microextraction in the determination of polycyclic aromatic hydrocarbons

Two modes of liquid-phase microextraction (LPME), static and semi-automated dynamic, have been developed for the HPLC analysis of polycyclic aromatic hydrocarbons. In static LPME, a small drop (3 microl) of organic solvent was held at the tip of a microsyringe needle and exposed to the sample containing the analytes, permitting extraction to occur. In semi-automated dynamic LPME, a syringe pump was used to automate the repetitive procedure of filling a microsyringe barrel that functioned as a microseparatory funnel, with fresh aliquots of sample, and expelling them after extraction. The factors influential to both techniques such as the type of organic solvent, extraction time, sampling volume, number of samplings, salt concentration and temperature were investigated. Static LPME provided high enrichment (60- to 180-fold) and simplicity. The analytical data exhibited a relative standard deviation range of 4.7-9.0%. Dynamic LPME provided higher (>280-fold) enrichment within nearly the same extraction time (approximately 20 min) and better precision (< or = 6.0%). Both methods allow the detection of polycyclic aromatic hydrocarbons at microg/l levels in water by HPLC. Water samples collected from two rivers were analyzed using the methods, respectively. The results demonstrated that both modes of LPME were fast, simple and accurate.     

Determination of phenols in water using liquid phase microextraction with back extraction combined with high-performance liquid chromatography.

Liquid phase microextraction with back extraction (LPME/BE) combined with high-performance liquid chromatography (HPLC) was studied for the determination of a variety of phenols in water samples. The target compounds were extracted from 2-ml aqueous sample adjusted to pH 1 (donor solution) through a microliter-size organic solvent phase (400-microl n-hexane), confined inside a small PTFE ring, and finally into a 1-microl basic aqueous acceptor microdrop suspended inthe aforementioned solvent phase from the tip of a microsyringe needle. After extracting for a prescribed time, the microdrop was taken back into the syringe and directly injected into an HPLC for detection. Factors relevant to the extraction procedure were studied. At the optimized extraction conditions, a large enrichment factor (more than 100-fold) can be achieved for most of the phenols within 35 min. The detection limit range was 0.5-2.5 microg/l for different analytes in aqueous samples. The results demonstrate the suitability of the LPME/BE approach to the analysis of polar compounds in aqueous samples.     

Trace level analysis of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and its biodegradation intermediates in liquid media by solid-phase extraction and high-pressure liquid chromatography analysis

The use of solid-phase extraction for the analysis of liquid media containing low microg/L levels of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), mononitroso-RDX (MNX), dinitroso-RDX (DNX), and trinitroso-RDX (TNX) is examined. Aqueous samples (100 mL) consisting of water and a microbiological basal medium are spiked with known concentrations of RDX, MNX, DNX, and TNX. The compounds are extracted from the liquid media using a Porapak RDX cartridge and then eluted from the cartridge with 5 mL of acetonitrile. The eluent is concentrated to 1 mL before analysis by high-pressure liquid chromatography (HPLC). The method detection limits for RDX are 0.1 microg/L in water and 0.5 microg/L in the basal medium after a 100-fold concentration. For MNX, DNX, and TNX, the method detection limits are approximately 0.5 microg/L in water and approximately 1 microg/L in the basal medium after a 100-fold concentration. Interferences in the basal medium and a contaminant in the standard made quantitation for MNX and TNX, respectively, is less accurate below the 1 microg/L level. Solid-phase extraction of the liquid media gave good recoveries of nitramines and nitroso intermediates from a microbiological basal medium, allowing HPLC detection of RDX and the nitroso intermediates in the low microg/L (ppb) range.     

Simultaneous chiral determination of methamphetamine and its metabolites in urine by capillary electrophoresis-mass spectrometry

A capillary electrophoresis-mass spectrometry method for the simultaneous chiral determination of enantiomers of methamphetamine (MA), amphetamine (AP), dimethylamphetamine (DMA) and p-hydroxymethamphetamine (pOHMA), in urine has been developed. The internal standards used were 2-phenylethylamine and 1-amino4-phenylbutane. The electrolyte was 1 M formic acid (pH 2.2). The chiral selector, which was added to the electrolyte, was a mixture of 3 mM beta-cyclodextrin and 10 mM heptakis(2,6-di-O-methyl)-beta-cyclodextrin. The detection limits were 0.03 microg ml(-1) for the enantiomers of MA and AP and 0.05 microg ml(-1) for the enantiomers of pOHMA using selected ion monitoring. In the analysis of healthy adult urine samples spiked with MA, AP and pOHMA, the precision of within-run assays (n = 4) for the migration time after correction with two internal standards were under 0.04%, and the detection yields utilizing solid phase extraction were 95-105%. This method was applicable to the analysis of urine samples of MA addicts and DMA addicts.     

Cigarette filter as sorbent for on-line coupling of solid-phase extraction to high-performance liquid chromatography for determination of polycyclic aromatic hydrocarbons in water

An on-line solid-phase extraction (SPE) protocol using the cigarette filter as sorbent coupled with high-performance liquid chromatography (HPLC) was developed for simultaneous determination of trace naphthalene (NAPH), phenanthrene (PHEN), anthracene (ANT), fluoranthene (FLU), benzo(b)fluoranthene (BbF), benzo(k)fluoranthene (BkF), benzo(a)pyrene (BaP), and benzo(ghi)perylene (BghiP) in water samples. To on-line interface solid-phase extraction to HPLC, a preconcentration column packed with the cigarette filter was used to replace a conventional sample loop on the injector valve of the HPLC for on-line solid-phase extraction. The sample solution was loaded and the analytes were then preconcentrated onto the preconcentration column. The collected analytes were subsequently eluted with a mobile phase of methanol-water (95:5). HPLC with a photodiode array detector was used for their separation and detection. The detection limits (S/N = 3) for preconcentrating 42 mL of sample solution ranged from 0.9 to 58.6 ng L(-1) at a sample throughput of 2 samples h(-1). The enhancement factors were in the range of 409-1710. The developed method was applied to the determination of trace NAPH, PHEN, ANT, FLU, BbF, BkF, BaP and BghiP in local river water samples. The recoveries of PAHs spiked in real water samples ranged from 87 to 115%. The precisions for nine replicate measurements of a standard mixture (NAPH: 4.0 microg L(-1), PHEN: 0.40 microg L(-1), ANT: 0.40 microg L(-1), FLU: 2.0 microg L(-1), BbF: 1.6 microg L(-1), BkF: 2.0 microg L(-1), BaP: 2.0 microg L(-1), BghiP: 1.7 microg L(-1)) were in the range of 1.2-5.1%.     

Comparison between external and internal standard calibration in the validation of an analytical method for 1-hydroxypyrene in human urine by high-performance liquid chromatography/tandem mass spectrometry

1-Hydroxypyrene is a metabolite of pyrene, a member of the class of polycyclic aromatic hydrocarbons (PAHs) whose toxic properties in some cases include carcinogenicity. The determination of 1-hydroxypyrene in human urine is used as a biological indicator for exposure to PAHs, which is related to the combustion of organic materials, like smoking, living in urban environments, and eating grilled or smoked food. The determination of 1-hydroxypyrene by high-performance liquid chromatography (HPLC) with fluorescence detection has very good sensitivity but it is not highly specific: this can reduce accuracy in the quantitative determination of low levels of analyte in a complex matrix like urine. An HPLC method that uses triple quadrupole mass detection has been validated with the objective both to improve the signal-to-noise (S/N) ratio and to achieve the maximum specificity for the analyte in those urine samples that are richer in possible inteferents. The calibration range for 1-hydroxypyrene is from 0.005-0.1 microg/L in the urine of non-smoking healthy volunteers. After solid-phase extraction, samples were analyzed by HPLC/tandem mass spectrometry (MS/MS) in the multiple reaction monitoring (MRM) mode. In order to obtain reliable results quantitative analysis must be performed by means of the internal standard method (we used deuterium-labelled 1-hydroxypyrene): the method accuracy is not less than 85%. The S/N ratio at a concentration of 0.1 microg/L is about 10, and therefore this can be considered the lowest limit of quantitation. The method performance does not change if urine samples are measured using a calibration curve prepared in methanol, thus reducing the time of analysis and costs.     

Novel polymer monolith microextraction using a poly(methacrylic acid-ethylene glycol dimethacrylate) monolith and its application to simultaneous analysis of several angiotensin II receptor antagonists in human urine by capillary zone electrophoresis

Novel polymer monolith microextraction (PMME) using a poly(methacrylic acid-ethylene glycol dimethacrylate) (poly(MAA-EGDMA)) monolith in conjunction with capillary zone electrophoresis (CZE) was developed for the determination of several angiotensin II receptor antagonists (ARA-IIs) in human urine. The extraction device consisted of a regular plastic syringe (1 mL), a poly(MAA-EGDMA) monolithic capillary (2 cm x 530 microm I.D.) and a plastic pinhead connecting the former two components seamlessly. The extraction was achieved by driving the sample solution through the monolithic capillary tube using a syringe infusion pump, and for the desorption step, an aliquot of organic solvent was injected via the monolithic capillary and collected into a vial for subsequent analysis by CZE. The best separation was realized at 25 kV using a buffer that consisted of 50% acetonitrile and 50% buffer solution (v/v) containing 10 mM disodium hydrogenphosphate (adjusted to pH 2.3 with 1M hydrochloric acid). The method was successfully applied to the determination of telmisartan (T), irbesartan (I) and losartan (L) in urine samples with candesartan (C) as internal standard, yielding the detection limit of 15-20 ng/mL. Close correlation coefficients (R>0.999) and excellent method reproducibility were obtained for all the analytes over a linear range of 0.08-3 microg/mL.     

Single drop micro-extraction with O,O-diethyl dithiophosphate for the determination of lead by electrothermal atomic absorption spectrometry

Lead was extracted as the O,O-diethyldithiophosphate (DDTP) complex from aqueous solution into a drop of CHCl(3) immersed in the solution. Unlike previously reported procedures using single drop micro-extraction (SDME) for the extraction of inorganic analytes, the complexation reaction was conducted in the aqueous phase, as the ammonium salt of DDTP is soluble in water. The concentration of DDTP was optimized as 0.01% (m/v). Experimental parameters such as extraction time (7min) and organic drop volume (3microL) were optimized and selected as a compromise between sensitivity and stability of the organic drop in the aqueous solution. The sensitivity with electrothermal atomic absorption spectrometry (ET AAS) was low, probably due to infiltration of the organic drop into the totally pyrolytic graphite platform. To overcome this problem, tungsten (400microg) was thermally deposited onto the platform surface. A short pyrolysis stage at 700 degrees C was included to reduce background absorption. Under these conditions, five certified reference materials with different characteristics were analyzed using calibration against aqueous standards submitted to the SDME procedure, resulting in good agreement between certified and found concentration values at a 95% confidence level. Two real water samples have also been analyzed, with recoveries ranging from 85 to 92% after enrichment with Pb. An enhancement factor of 52 allowed a detection limit of 0.2microg L(-1) or 0.04microg g(-1), demonstrating the high detection capability of the proposed procedure, with a relative standard deviation typically below 4%.     

Determination of organic compounds in water using dispersive liquid-liquid microextraction

A new microextraction technique termed dispersive liquid-liquid microextraction (DLLME) was developed. DLLME is a very simple and rapid method for extraction and preconcentration of organic compounds from water samples. In this method, the appropriate mixture of extraction solvent (8.0 microL C2Cl4) and disperser solvent (1.00 mL acetone) are injected into the aqueous sample (5.00 mL) by syringe, rapidly. Therefore, cloudy solution is formed. In fact, it is consisted of fine particles of extraction solvent which is dispersed entirely into aqueous phase. After centrifuging, the fine particles of extraction solvent are sedimented in the bottom of the conical test tube (5.0 +/- 0.2 microL). The performance of DLLME is illustrated with the determination of polycyclic aromatic hydrocarbons (PAHs) in water samples by using gas chromatography-flame ionization detection (GC-FID). Some important parameters, such as kind of extraction and disperser solvent and volume of them, and extraction time were investigated. Under the optimum conditions the enrichment factor ranged from 603 to 1113 and the recovery ranged from 60.3 to 111.3%. The linear range was 0.02-200 microg/L (four orders of magnitude) and limit of detection was 0.007-0.030 microg/L for most of analytes. The relative standard deviations (RSDs) for 2 microg/L of PAHs in water by using internal standard were in the range 1.4-10.2% (n = 5). The recoveries of PAHs from surface water at spiking level of 5.0 microg/L were 82.0-111.0%. The ability of DLLME technique in the extraction of other organic compounds such as organochlorine pesticides, organophosphorus pesticides and substituted benzene compounds (benzene, toluene, ethyl benzene, and xylenes) from water samples were studied. The advantages of DLLME method are simplicity of operation, rapidity, low cost, high recovery, and enrichment factor.     

Analysis of benzene ethylamine derivatives in urine using the programmable dynamic liquid-phase microextraction (LPME) device

An automated LPME device for a dynamic LPME method was manufactured and its extraction efficiency was tested using spiked urine samples. The developed home-made LPME device was a programmable automated syringe dispenser to overcome deteriorating precision and difficulties in manually manipulating the plunger repeatedly. To establish the optimum parameters for benzene ethylamines, the effects of sampling volume, solvent volume, pH, salt-effect, choice of solvents, plunger speed, and number of samplings were investigated. Good repeatabilities for the extraction of mephentermine, ephedrine, methoxyphenamine, selegiline, and bupropion were obtained and the RSD values were 2.4, 1.9, 1.3, 1.6 and 1.5% at a concentration of 3 microg mL(-1) in spiked urine samples, respectively. The limit of detection was below 0.05 microg mL(-1) for the investigated drugs. This developed device for LPME analysis gave good validation results and improved convenience.     

Extraction and determination of polybrominated diphenyl ethers in water and urine samples using solidified floating organic drop microextraction along with high performance liquid chromatography

We have developed a method, termed solidification of floating organic drop microextraction (SFOME), for the extraction of polybrominated diphenyl ethers (PBDEs) in water and urine samples, this followed by quantification via HPLC. This method requires very small quantities of organic solvent consumption. It is based on exposing a floating solidified drop of an organic solvent on the surface of aqueous solution in a sealed vial. The organic drop is easily collected with a spatula, molten (at ambient temperature), and then submitted to HPLC. Experimental parameters including extraction solvent and its volume, disperser solvent and its volume, extraction time, ionic strength, stirring speed and extraction temperature were optimized. The enrichment factors of analytes are in the range from 921 to 1,462, and acceptable extraction recoveries (92%–118%) are obtained. The dynamic linear range for five PBDE congeners is in the range of 0.5–75?μg.L^?1 and from 5 to 500?μg.L^?1 for BDE 209. The correlation coefficients range from 0.9960 to 0.9999. The limits of detection (at S/N?=?3) for PBDE congeners vary between 0.01 and 0.04?μg.L^?1. This method has been successfully applied to detecting PBDEs in two environmental waters and in human urine.

固相微萃取涂层的制备及其在水体和气态基质中的应用

采用物理涂渍的方法制备了γ-Al2O3固相微萃取涂层。通过γ-Al2O3固相微萃取（SPME）-气相色谱（GC）联用技术,对水中痕量苯系物苯、甲苯、乙苯、二甲苯异构体(BTEXs)进行萃取分析,结果表明该涂层具有热稳定性强(最高使用温度可达350 ℃)、灵敏度高(检测限为1~10 μg/L)以及制备重复性好（相对标准偏差为8.3%）的特点;同时该涂层对气态基质中的污染物亦可进行萃取分析。     

Dynamic three-phase hollow fiber microextraction based on two immiscible organic solvents with automated movement of the acceptor phase

Dynamic three-phase hollow fiber liquid-liquid-liquid microextraction (HF-LLLME) based on two immiscible organic solvents, with automated movement of organic acceptor phase to facilitate mass transfer was introduced for the first time. Polycyclic aromatic hydrocarbons were used as model compounds and extracted from water and soil samples. The extraction involved filling an 8 cm length of hollow fiber with 25 μL of organic acceptor solvent using a microsyringe, followed by impregnation of the pores in the fiber wall with n-dodecane. The fiber was then immersed in 20 mL of aqueous sample solution. During extraction, the organic acceptor phase was repeatedly moved in the lumen of the hollow fiber by movement of the syringe plunger controlled by programmable syringe pump. Following this microextraction, 2 μL of organic acceptor phase was injected into gas chromatography-flame ionization detector. This new technique provided up to 554-fold preconcentration of the analytes under the optimized conditions. Good repeatabilities (with RSDs ≤8.4%) were obtained. Detection limits were in the range of 0.2-0.5 μg/L. The utilization of the proposed method for extraction of the polycyclic aromatic hydrocarbons from different real samples (such as water and soil samples) also gave good precision and recovery.     

Extraction of trace organic pollutants from aqueous samples by a single drop method

Summary A single drop extraction method for isolation of trace organic pollutants from aqueous samples is described. The optimisation of extraction parameters such as drop volume, temperature, time and solvent type, on the extraction efficiency was investigated. This technique involves use of small amounts of organic solvent (2μL) in a conventional GC syringe. The analytical performance of this technique is presented for the determination of trichlorobenzene and trichloromethane. Suitable precision of extraction was obtained with RSD values in the range of 2.5–5.2%. Presented at Balaton Symposium on High Performance Separation Methods, Siófok Hungary, September 1–3, 1999     

Screening of citalopram, fluoxetine and their metabolites in human urine samples by gas chromatography-mass spectrometry. A global robustness/ruggedness study

Capillary gas chromatography with mass spectrometry detection in SIM mode (GC-MS-SIM) has been used for the analysis of citalopram (CIT), fluoxetine (FLX), and all of their metabolites in urine samples. The instrumental parameters affecting GC separation and MS-SIM detection were investigated. A validation procedure was performed on urine matrix and a simultaneous robustness/ruggedness evaluation is also presented in this paper. An optimized solid-phase extraction (SPE) has been applied, reaching in this way to limits of detection (LODs) between 0.7 ng L(-1) (CIT) and 33.6 microg L(-1) (CIT-PA). A pharmacokinetic screening in clinical urine samples has been also carried out.     

Validated procedure for simultaneous trace level determination of the anti-cancer agent gemcitabine and its metabolite in human urine by high-performance liquid chromatography with tandem mass spectrometry

A sensitive, accurate and reproducible procedure has been developed for the quantitative determination of gemcitabine (2',2'-difluorodeoxycytidine, dFdC) and its metabolite 2',2'-difluorodeoxyuridine (2dFdU) in human urine. The samples (2 mL) were extracted by solid-phase extraction (SPE) and analyzed by reversed-phase high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC/MS/MS), operating in multiple reaction monitoring (MRM mode). This procedure was validated using 2'-deoxycytidine as internal standard (IS). The urine assay was linear over the range 0-50 microg/L, with a limit of quantification (LLOQ) of 0.2 microg/L for gemcitabine and 1.0 microg/L for the metabolite. The respective limits of detection (LODs) for dFdC and 2dFdU were 0.05 and 0.3 microg/L. The precision and accuracy of the assay were determined on three different days. The within-series precision was found to be always less than 8.5 and 12.7% for gemcitabine and 2dFdU, respectively. The overall precision expressed as relative standard deviation (CVr) was always less than 7.1% for both analytes. The recovery of gemcitabine was always greater than 90% with a CVr <6.3%. The measurement uncertainty determined from the validation data assessed the possibility of determining this drug and its metabolite at trace levels in urine, considering that the combined uncertainty of the whole procedure was always less than 30%.     

In‐line coupled single drop liquid–liquid–liquid microextraction with capillary electrophoresis for determining fluoroquinolones in water samples

A simple in‐line single drop liquid–liquid–liquid microextraction (SD‐LLLME) coupled with CE for the determination of two fluoroquinolones was developed. The method is capable to quantify trace amount of analytes in water samples and to improve the sensitivity of CE detection. For the SD‐LLLME, a thin layer of organic phase was used to separate a drop of 0.1 M NaOH hanging at the inlet of the capillary from the aqueous donor phase. By this way, the analytes were extracted to the acceptor phase through the organic layer based on their acidic/basic dissociation equilibrium. The drop was immersed into the organic phase during 10 min for extraction and then it is directly injected into the capillary for the analysis. Parameters such as type and volume of organic solvent phase, aqueous donor, and acceptor phases and extraction time and temperature were optimized. The enrichment factor was calculated, resulting 40‐fold for enrofloxacin (ENR) and sixfold for ciprofloxacin (CIP). The linear range were 20–400 μg/L for ENR and 60–400 μg/L for CIP. The detection limits were 10.1 μg/L and 55.3 μg/L for ENR and CIP, respectively, and a good reproducibility was obtained (4.4% for ENR and 5.6% for CIP). Two real water samples were analysed applying the new method and the obtained results presented satisfactory recovery percentages (90–100.3%).     

Ion-pair liquid-liquid-liquid microextraction of nerve agent degradation products followed by capillary electrophoresis with contactless conductivity detection

The four nerve agent degradation products methylphosphonic acid (MPA), ethyl methylphosphonic acid (EMPA), isopropyl methylphosphonic acid (IMPA) and cyclohexyl methylphosphonic acid (CMPA) have been successfully extracted from aqueous sample solution by ion-pair liquid-liquid-liquid microextraction. In this procedure, the target analytes in the sample solution were converted into their ion-pair complexes with tri-n-butyl amine and then extracted by an organic solvent (1-octanol) layer on top of the sample solution. Simultaneously, the analytes were back-extracted into a drop of an aqueous acceptor solution which was suspended in the organic phase at a microsyringe needle tip. The factors influential to extraction: type of organic solvent, type of ion-pair reagent and its concentration, pH values of sample solution and acceptor aqueous phase, stirring rate and extraction time were investigated in detail. After extraction, the drop of the acceptor solution was withdrawn into the syringe and injected into a capillary electrophoresis system for analysis. Using contactless conductivity detection, direct quantification of these compounds is possible. Moreover, large-volume sample injection was employed for further preconcentration. Improvements in the limits of detection between 2.5 and 4 orders of magnitude could be achieved and concentrations at the ng/mL level can be determined. This newly established approach was successfully applied to a spiked river water sample.