A comparative solid-phase extraction study for the simultaneous determination of fluvoxamine, mianserin, doxepin, citalopram, paroxetine, and etoperidone in whole blood by capillary gas-liquid chromatography with nitrogen-phosphorus detection

This paper reports a simple and reliable gas chromatographic method with nitrogen-phosphorus detection without derivatization for the simultaneous detection of fluvoxamine, mianserin, doxepin, citalopram, paroxetine, and etoperidone in whole blood as part of a systematic toxicological analysis (STA). All drugs were studied at concentration levels of 100-2000 ng/mL, except paroxetine for which it was necessary to study at concentration levels of 400-8000 ng/mL. A comparative and validation study using two solid-phase extraction (SPE) columns, Chem Elut and Bond Elut Certify, was developed regarding their recovery, precision, sensitivity, and matrix purification efficiency. The Chem Elut columns, diatomaceous earth, are closely related to conventional liquid-liquid extraction. The Bond Elut Certify columns, more recently developed in the market, are mixed SPE (reversed-phase and cation exchange sorbent). Recoveries for the antidepressants using Chem Elut columns at 500 ng/mL (2000 ng/mL for paroxetine) were in the range 43-72% with intra- and interassay precisions of less than 10% and 16%, respectively. Limits of detection (LODs) and quantitation (LOQs) for fluvoxamine, mianserin, doxepin, citalopram, and etoperidone ranged from 18 to 236 ng/mL and 60 to 786 ng/mL, respectively. LOD and LOQ for paroxetine were 303 and 1009 ng/mL, respectively. Recoveries of these compounds using Bond Elut Certify columns at 500 ng/mL (2000 ng/mL for paroxetine) were in the range 52-83% with intra- and interassay precisions of less than 6% and 8%, respectively. LODs and LOQs for fluvoxamine, mianserin, doxepin, citalopram, and etoperidone ranged from 7 to 28 ng/mL and 23 to 93 ng/mL, respectively. LOD and LOQ for paroxetine were 113 and 376 ng/mL, respectively. An excellent linearity was observed with both procedures from the LOQs up to the upper studied concentration level. In general, higher recoveries, cleaner extracts, better sensitivity, better precision, and reduced solvent consumption and disposal were achieved for the screening of these antidepressants with the use of the mixed SPE Bond Elut Certify compared with Chem Elut columns. The application of these methods on a forensic case study is also presented.     

Measurement of trazodone using solid-phase extraction and wide-bore capillary gas chromatography with nitrogen-selective detection

A method for the determination of the antidepressant drug trazodone is presented. 8-Hydroxyloxapine is used as the internal standard. A simple solid-phase extraction procedure utilizing disposable reversed-phase C18 columns is described. Samples are analyzed by gas chromatography with nitrogen-selective detection using a wide-bore capillary column with a permanently bonded, nonpolar stationary phase. The assay possesses linearity to 3.0 micrograms/mL, sensitivity to at least 0.25 microgram/mL, recovery averaging 96%, and between-run precision reflected by a CV of 5.6%. We conclude that the method reported here is ideally suited for monitoring therapeutic and toxic levels of trazodone.     

Simultaneous determination of viloxazine,venlafaxine, imipramine,desipramine, sertraline,and amoxapine in whole blood: comparison of two extraction/cleanup procedures for capillary gas chromatography with nitrogen-phosphorus detection

A comparative study for the simultaneous gas chromatographic (GC) resolution and detection of the six antidepressants viloxazine, venlafaxine, imipramine, desipramine, sertraline, and amoxapine in whole blood at concentration levels of 100-2000 ng/mL was developed. Two extraction/cleanup analytical procedures were compared regarding their recovery, precision, sensitivity and matrix purification efficiency. The first procedure consists of the employment of Chem Elut columns (diatomaceous earth) and is based on the principle of liquid-solid absorption extraction that is closely related to conventional liquid-liquid extraction. The second focuses on the use of Bond Elut Certify columns and a mixed SPE, reversed-phase and cation-exchange sorbent, more recently developed for the market. Each procedure required 2.0 mL of whole blood extraction and injection into a capillary GC equipped with a nitrogen-phosphorus detector. Mepivacaine was used as the extraction standard (surrogate), and prazepam was used as the chromatographic standard. No interferences were found, and the time for the chromatographic analysis was 16 min for one sample. Recoveries of the compounds using Chem Elut columns at 500 ng/mL were in the range of 28-74% with intra-assay and interassay precisions of less than 7% and 19%, respectively. Limits of detection (LOD) and quantitation (LOQ) ranged from 39 to 153 ng/mL and from 128 to 504 ng/mL, respectively. Recoveries of the compounds using Bond Elut Certify columns at 500 ng/mL were in the range of 64-86% with intra-assay and interassay precisions of less than 4% and 10%, respectively. LODs and LOQs ranged from 21 to 100 ng/mL and from 70 to 330 ng/mL, respectively. An excellent linearity was observed with both procedures from the LOQs up to 2000 ng/mL. The use of the reversed-phase and cation-exchange sorbent Bond Elut Certify showed advantages compared with Chem Elut columns for the screening of these antidepressants such as higher recoveries, cleaner extracts, better sensitivity, better precision, and less solvent consumption and disposal.     

Simultaneous congener-specific determination of selected organochlorine compounds and nitro musks in human whole blood samples by solid-phase extraction and capillary gas chromatography with electron capture detection

Chlororganic compounds like pesticides or polychlorinated biphenyls (PCB) and nitro musks are environmental contaminants, which remain public health concerns because of their persistence in humans and their toxicological properties. Many of these substances are associated with endocrine dysfunction or with carcinogenicity. Therefore, a simple method using solid-phase extraction followed by capillary gas chromatography with electron capture detection for the simultaneous determination of both organochlorines and nitro musks in human whole blood samples has been developed. Recovery rates of 13 PCB congeners and of 7 pesticides ranged from 67.5% to 100.4% and from 81.1% to 110.5%, respectively. Recoveries of the 5 nitro musks were consistent and ranged from 90.2% to 98.8%. The accuracy for organochlorines and nitro musks varied from 6.3% to 8.6%. Method detection limits ranged from 0.02 microg/L to 0.11 microg/L for the organochlorines and from 0.04 microg/L to 0.08 microg/L for the nitro musks. The method has a high sensitivity with a low detection limit even in slightly contaminated human blood samples. The time and technical effort is small, so the method is feasible for epidemiological studies with regard to the impact of organochlorines and nitro musks on certain diseases.     

Automated solid-phase extraction method for the determination of piperaquine in whole blood by rapid liquid chromatography

A bioanalytic method for the determination of piperaquine in whole blood by solid-phase extraction and rapid liquid chromatography has been developed and validated. Whole blood was hemolyzed with deionized water, and an internal standard was added to the samples before they were loaded onto a PRS cation-exchange solid-phase extraction column. Piperaquine and internal standard were analyzed by liquid chromatography on a Chromolith Performance (100 x 4.6 mm) column with mobile phase acetonitrile:phosphate buffer, I = 0.1, pH 2.5 (8:92, vol/vol), flow rate 4 mL x min-1, and UV detection at 345 nm. The intraassay precision for whole blood was 3.2% at 3.00 microM and 12.3% at 0.100 microM. The interassay precision for whole blood was 1.8% at 3.00 microM and 5.2% at 0.100 microM. The lower limit of quantification and the limit of detection were 0.050 microM and 0.010 microM, respectively.     

Specific determination of linear Alkylbenzenesulfonates (LAS) in commercial detergents and whole blood by high-performance liquid chromatography with solid-phase extraction

This paper presents the extraction and analysis of linear alkylbenzenesulfonates (LAS) from whole blood using solid-phase extraction (SPE) together with high-performance liquid chromatography (HPLC). The sample was buffered with extraction solution and purified with Bakerbond C(18) SPE columns. The columns were washed, dried, and eluted with experimental optimized solvent systems. HPLC was performed using a Wakopak) WS AS-Aqua column (4.6 * 250-mm) and monitored at 228 nm using a UV detector. A mobile phase consisting of acetonitrile/water (60:40, v/v) and containing 1.2% (w/v) of sodium perchlorate was employed. Good separation was achieved for the five homologues of LAS (C(10) approximately C(14)) eluted at 6.85 and 13.79 min. The linearity range for this analysis was found to be from 10.0 to 100.0 ng/g and the limit of detection was 4.0-5.0 ng/g in blood for each homologue. The recovery of each homologue in blood ranged from 76 to 107%. The LAS in commercial detergents could be extracted and the homologues of C(10) approximately C(13) were detected. Blood samples of rats, which were administered a commercial detergent orally, were determined by the present method, and C(14) was used as an internal standard. The method was simple and reliable for the determination of LAS in blood samples and could be expected to apply to the forensic and clinical specimens.     

A single-step extraction for screening whole blood for basic drugs by capillary GC/NPD

Basic drugs were routinely extracted from whole blood under alkaline conditions into n-butyl acetate. An aliquot of the n-butyl acetate was injected into a gas chromatograph equipped with a nitrogen-phosphorous detector and a wide-bore cross-linked 50% phenylmethyl silicone capillary column. Absolute and relative retention times were recorded for more than 100 extracted drug standards. Recovery from whole blood was determined for some of the more frequently encountered drugs. This one-step extraction proved to be reliable for general screening and has been used routinely in forensic and clinical toxicological analyses.     

A modified assay for cyclosporin in blood using solid-phase extraction with high-performance liquid chromatography

A modified procedure for measuring cyclosporin in whole blood by high-performance liquid chromatography is described and evaluated for clinical use. Sample preparation uses solid-phase extraction cartridges that can be reused. Life of the reverse-phase analytical column exceeds 1,000 injections at 70 degrees C. Cyclosporins A and D (internal standard) elute after 5.6 and 7.6 min, respectively. Calibration plots are linear from 50 ng/ml to at least 2,000 ng/ml. Within-day and between-day imprecision is less than 9% (coefficient of variation). Minimum measurable concentration is 50 ng/ml.     

固相萃取-反相高效液相色谱法测定全血环孢素A

目的：采用快速固相萃取反相高效液相色谱法测定全血环孢素Ａ。方法：全血用水溶血,用乙腈和水混合液沉淀蛋白后,用ＳＰＥ固相萃取柱萃取,５０％甲醇冲洗杂质,９５％甲醇洗脱,挥干,乙腈重组,正己烷进一步除去杂质,重组液上机。本法采用柱温为７０℃的Ｃ１８反相色谱柱,以乙腈∶甲醇∶水（３∶１∶１,Ｖ∶Ｖ）为流动相,检测波长２１０ｎｍ。结果：本法最低检出浓度为２０ｎｇ·ｍｌ－１。至少在４０～１５００ｎｇ·ｍｌ－１范围内呈线性。平均方法回收率１０２．９％,ＲＳＤ均在１０％以内。结论：本法灵敏,特异,既适合临床常规检测又适合ＣｓＡ的药动学研究。     

Headspace solid-phase micro-extraction and gas chromatography with micro-electron capture detection for the measurement of p,p'-DDE in rat whole blood and hair

A sensitive, specific, and reproducible capillary gas chromatography (GC) with micro-electron capture detection (micro-ECD) method using headspace solid-phase micro-extraction (HS-SPME) for the quantitative analysis of p,p'-DDE in rat whole blood and hair was developed. A 100 microm polydimethylsiloxane (PDMS) phase was used for the extraction. The obtained detection limits were 0.003 ng/mg and 0.004 ng/mg in whole blood and hair, respectively, at a signal-to-noise ratio of 3 (S/N = 3). Linearity was obtained in the ranges 0.003-2.0 ng/mg and 0.004-2.0 ng/mg in whole blood and hair, respectively, and the correlation coefficients of whole blood and hair were greater than 0.998. This method was successfully applied to the analysis of p,p'-DDE in rat whole blood and rat hair after an oral dose of p,p'-DDE.     

Determination of Ro 15-1788, a benzodiazepine antagonist, in human plasma by gas-liquid chromatography with nitrogen-phosphorus detection. Application to single-dose pharmacokinetic studies

A sensitive (to 3 ng/ml) and specific method for analysis of the benzodiazepine antagonist Ro 15-1788 is described. The method utilizes gas-liquid chromatography with nitrogen-phosphorus detection. A neutral pH ethyl acetate extraction of 0.1-3.0 ml plasma is used for sample preparation. Standard curves using methylclonazepam as the internal standard are linear for plasma concentrations up to 200 ng/ml. Applicability of the method is demonstrated by a pharmacokinetic study in a normal volunteer who received 10 mg Ro 15-1788 intravenously.     

Simultaneous determination of citalopram, fluoxetine and their main metabolites in human urine samples by solid-phase microextraction coupled with high-performance liquid chromatography

A liquid chromatography method was developed for the determination of some frequently prescribed selective serotonin re-uptake inhibitors (SSRI) - citalopram and fluoxetine - and its main metabolites - demethylcitalopram, didemethylcitalopram and norfluoxetine - in human urine samples, using a previous stage of solid-phase microextraction. All the extraction parameters influencing adsorption (extraction time, temperature, pH, ion strength and organic modifier addition) and desorption (desorption time and desorption solvent mixture composition) of the analytes on the fiber have been studied. A satisfactory reproducibility for extraction from urine samples (R.S.D.<10%) was obtained. The linearity for urine ranged from 0.05 to 2 mg l(-1) with limits of detection close to 0.01 mg l(-1), which cover the typical urinary concentrations obtained for citalopram, fluoxetine and their metabolites.     

HPLC with ultraviolet detection for the determination of chloroquine and desethylchloroquine in whole blood and finger-prick capillary blood dried on filter paper

A simple, sensitive, selective and reproducible method based on liquid chromatography was developed for the determination of chloroquine (CQ) and its active plasma metabolite desethylchloroquine (DECQ) in finger-pricked capillary blood spot onto filter paper (DBS) and whole blood samples. Both were separated from the internal standard quinine on a reversed phase C18 column, with the mobile phase consisting of a mixture of 1% diethylamine, acetonitrile and methanol (20:55:25, v:v:v) running at a flow rate of 1.0ml/min. Retention times of QN, DECQ and CQ were 4.5, 5.7 and 6.4min, respectively. Ultraviolet detection was at the wavelength 256nm. Sample preparation was done by extraction with hexane and tert-butyl methyl ether (1:1, v:v). Good precision and accuracy were obtained for both within-day repeatability and day-to-day reproducibility. Limit of quantification (LOQ) for both CQ and DECQ was accepted as 50ng/ml using 80μl DBS sample and 25ng/ml using 150μl whole blood sample. The mean recoveries for CQ, DECQ and internal standard for both whole blood and DBS were between 74 and 87%. The method was successfully applied for a pharmacokinetic study of CQ and DECQ in patients with Plasmodium vivax. Excellence correlation (r=0.997) was observed between the analysis of both CQ and DECQ in paired whole blood and DBS samples.     

Fully automated assay for the determination of sumatriptan in human serum using solid-phase extraction and high-performance liquid chromatography with electrochemical detection

A method is described for a fully automated, sensitive, accurate and precise assay for the determination of sumatriptan in human serum. The assay consists of solid-phase extraction followed by reversed-phase HPLC with electrochemical detection. The extraction procedure has been fully automated on a Zymate XP robot linked on-line to the HPLC system. The assay is linear over the analytical range 1–30 ng ml⁻¹ and selective for sumatriptan with respect to endogenous plasma components and GR49336, the major circulating metabolite. The intra-assay data demonstrate a maximum bias and precision across the calibration range of 10% and 6.6%, respectively. The inter-assay data demonstrate a maximum bias and precision across the calibration range of 6.7% and 8.8%, respectively. The extraction efficiency of the assay is approximately 90% and is constant across the calibration range. The assay was used for the determination of sumatriptan in serum clinical samples and was shown to be robust in sustained use over several months. The use of a Zymate XP robot allowed complete automation of the assay, which resulted in high-quality, high-throughput analyses.     

A rapid and sensitive quantitation of Dipterex in serum by solid-phase extraction and gas chromatography with flame thermionic detection

A simple, sensitive, and rapid quantitative method for Dipterex in serum is described. A SepPak C18 cartridge for the extraction and gas chromatography with flame thermionic detection for determination are used. The detection limit is 2.5 ng/mL, and linearity is obtained in the range 5-500 ng/mL.     

A strategy for the determination of beta blockers in plasma using solid-phase extraction in combination with high-performance liquid chromatography

This paper describes a general approach for the therapeutic drug monitoring of 13 different beta blockers in plasma. The chromatographic system contains a cyanopropyl-bonded phase as a stationary phase in combination with a mobile phase composed of acetonitrile and phosphate buffer (pH = 3, mu = 0.05). Two modes of detection are used, namely, UV detection and fluorescence detection. The sample pretreatment is performed with a nitrile-sorbent in combination with methanol-phosphate buffer (pH = 3, mu = 0.05) or with methanol containing 0.1% propylamine as eluent. Acceptable recoveries are obtained for practolol, acebutolol, pindolol, oxprenolol, mepindolol, atenolol, propranolol, prenalterol, alprenolol, metoprolol, sotalol and nadolol. For labetalol, however, the elution recovery has to be improved. Finally, this approach is illustrated by the assay of nadolol in the plasma of patients suffering from hypertension, who had received an oral formulation of the drug.     

A simple and environmentally-friendly method by pipette-tip matrix solid-phase dispersion microextraction coupled with high-performance liquid chromatography for the simultaneous determination of lignans and terpenes

A simple and efficient ultra-miniaturized pipette-tip matrix solid-phase dispersion microextraction using molecular sieve as adsorbent has been developed to simultaneously determine honokiol, magnolol, costunlide and dehydrocostus lactone in a complex Chinese medicine. The types of adsorbent and elution solventswere optimized by single factor experiment. Adsorbent/sample ratio, grinding time and elution volume were optimized by Box-Behnken design (BBD). The optimum extraction is: using SBA-3 as an adsorbent, 200 μL of methanol as elution solvent, 2:1 of sample/adsorbent ratio and 130 s of grinding time. The proposed method applied in real samples provides good linearity (R² > 0.9999), sufficient accuracy, high reproducibility (RSD<4.93%) and satisfactory recoveries (91.4%–101.4%). Compared with the conventional methods, it is featured with a tiny amount of sample and adsorbent consumption (3 mg of sample and 6 mg of SBA-3) which accompanied with the advantage of rapid, simple, cheap and environment-friendly. Moreover, it shows great potential on analyzing precious or rare amounts of complicated samples.     

Stereoselective determination of venlafaxine and its three demethylated metabolites in human plasma and whole blood by liquid chromatography with electrospray tandem mass spectrometric detection and solid phase extraction

A stereoselective method is described for simultaneous determination of the S- and R-enantiomers of venlafaxine and its three demethylated metabolites in human plasma and whole blood samples. This validated method involved LC/MS/MS with positive electrospray ionization and solid phase extraction. Chromatographic separation was performed on a 250 mm × 2.1 mm Chirobiotic V column with a total run time of 35 min. In plasma, calibration curves were in the range of 1–1000 nM for the S- and R-enantiomers of venlafaxine and O-desmethylvenlafaxine, and 0.5–500 nM for N-desmethylvenlafaxine and N,O-didesmethylvenlafaxine. In whole blood the corresponding concentrations were 10–4000 and 5–2000 nM, respectively. The intra-day precision was <6.3% and the inter-day precision was <9.9% for plasma and <15% and <19% for whole blood. LLOQ ranged between 0.25 and 0.5 nM. No ion suppression/enhancement or other matrix effects were observed. The method was successfully applied for determination of venlafaxine and its metabolites in plasma from patients and whole blood samples from forensic autopsy cases.