Determination of acyclovir in plasma by solid-phase extraction and column liquid chromatography

After oral administration, valacyclovir, the L-valyl ester of acyclovir, converts to the antiherpes virus drug, acyclovir. The bioavailability of acyclovir after valacyclovir administration is between 3- to 4.5-fold higher than that achieved after oral acyclovir administration. Therefore, despite the drug's short terminal half-life (3 hours), acyclovir plasma concentrations obtained after oral administration of the prodrug offer a more convenient dosage regimen in patients with herpes zoster than that required after acyclovir administration. Acyclovir is also used for viral infection prophylaxis in patients with hematologic disorders and in those who have undergone solid organ transplantation. We have described a simple and selective liquid chromatographic method for the determination of acyclovir in plasma using a new polymeric reversed-phase sorbent for solid-phase extraction. A mean acyclovir absolute recovery of 90% was found after elution of the drug from the cartridge with the mobile phase. This procedure allowed us to measure 62.5 ng/mL of acyclovir with an acceptable precision using a plasma volume of 250 microL, and no drug was found to interfere with the assay. This method is suitable for the therapeutic monitoring of acyclovir in patients who have been given a wide variety of coadministered drugs.     

Determination of indinavir in plasma by solid-phase extraction and column liquid chromatography.

Indinavir is a specific and potent HIV protease inhibitor. A new column liquid chromatographic method for the determination of this drug is described. This assay was developed for the clinical monitoring of trough concentrations in AIDS patients, using a 1-mL plasma sample volume. Determination of indinavir was made by a rapid solid-phase extraction procedure with the new polymeric Oasis HLB sorbent followed by a reversed-phase liquid chromatography and a UV detection at 210 nm. A weighted least squares linear regression (weighting factor = 1/y where y = peak height ratio) was used to calculate the equation relating the peak-height ratio of the drug and the internal standard to the concentration of indinavir in the range 10-800 ng/mL (0.014-1.124 microM). At the lower limit of quantification (10 ng/mL), the mean accuracy was 102 +/- 7% and 104 +/- 11% for within- and between-day analysis, respectively. The limit of detection, based on a signal-to-noise ratio of 2:1, was 4 ng/mL (0.006 microM). Compounds of interest were eluted from the extraction cartridges with 300 microL of mobile phase, and mean absolute recoveries of indinavir and internal standard were 66.4% and 80.3%, respectively. No metabolite of indinavir was found to co-elute with the drug or its internal standard. Among the tested drugs, especially nucleoside analogues and the other protease inhibitors used in clinical care, none was found to interfere with the assay at this time. This simple and selective method is suitable for therapeutic indinavir monitoring.     

反相高效液相色谱法测定血清中丙戊酸浓度

目的建立适于普遍应用的丙戊酸血浓度测定方法.方法本文采用BrMMC将丙戊酸转化为可紫外检测的酯,再经RP-HPLC测定.结果在15～200μg*ml-1范围内,丙戊酸衍生物和内标的峰高比与浓度呈良好的线性关系,r=0.9991;平均回收率为100.9%.应用于34例患者的治疗药物监测,取得良好的临床效果.结论方法准确、灵敏、选择性强、重现性好,操作简便快速.本法适于临床研究与应用.     

高效液相色谱法测定丙戊酸血药浓度

目的建立测定血浆中丙戊酸血药浓度的高效液相色谱法.方法血浆用正己烷提取,经α-溴苯乙酮衍生后浓集进样,采用Alltech     

毛细管气相色谱法测定癫痫患儿血清中丙戊酸浓度

目的:建立血清中丙戊酸(VPA)毛细管气相色谱测定方法,监测丙戊酸血药浓度,分析血药浓度与剂量及疗效关系.方法:程序升温高效毛细管气相色谱法测定癫痫患儿血清中丙戊酸浓度.结果:丙戊酸在20～300 mg·L-1范围内线性关系良好,最低检测浓度为1 mg·L-1.相对回收率96%以上,日内RSD＜4.3%,日间RSD＜7.6%.23例癫痫患儿血药浓度个体差异大,其中13例患儿剂量(20.8±3.8)mg·kg-1·d-1,血药浓度为(53.8±19.1)mg·L-1;10例患儿剂量(32.6±2.6)mg·kg-1·d-1,血药浓度为(65.3±27.8)mg·L-1.结论:本法专属性强、简便、快速、准确,适合于体液中丙戊酸的监测及药动学研究;癫痫患儿口服丙戊酸钠血药浓度个体差异大,血药浓度与给药剂量无显著相关性,宜采用个体化用药.     

高效液相色谱-柱前衍生化法测定丙戊酸血浓度

目的　 建立高效液相色谱法测定血清中丙戊酸浓度。 方法 　血清用正己烷提取 ,经α 溴苯乙酮衍生后浓缩进样。 结果 　丙戊酸的线性范围为 1 76～ 176 0 μg/ml,平均回收率大于 97% ,日内及日间RSD小于5 %。 结论 　本法快速、简便、准确 ,可应用于临床丙戊酸血药浓度测定     

衍生化-HPLC法测定人血清中丙戊酸浓度

目的建立HPLC法测定丙戊酸血清浓度。方法以环己基丙酸为内标,血清样品经乙醚提取后,经2,4′-二溴苯乙酮衍生化并用HPLC法进行测定。Shim-pack CLC-C18为色谱柱（150mm×4.6mm,5μm）;流动相：甲醇-乙醇-水（70：8：22）;流速：1.1mL/min;柱温：35℃;紫外检测波长：248nm;结果血清中丙戊酸在5.0～150.5μg/mL浓度范围内呈良好线性关系（r=0.9996）,回收率为98.2%～101.3%,日内与日间RSD≤5.2%。结论本法简便、准确、专属性强,适用于临床常规监测需要。     

Determination of some local anesthetics in human serum by gas chromatography with solid-phase extraction

A method of analysis based on solid-phase extraction coupled with capillary gas chromatographic system for determination of mepivacaine, bupivacaine and lidocaine from human serum was developed. As extraction sorbents were used Chromosorb 103, Tenax-GC and Chromosorb T. The best extraction sorbent proved to be Chromosorb 103. Their recoveries ranged from 91 to 94% at the target concentrations of approx. 1.5 microgml(-1) in serum. Relative standard deviation of the recoveries ranged from 3.11 to 5.30 at these concentrations. As internal standard was used lidocaine. The chromatographic analysis was performed on a gas chromatograph equipped with a capillary column, HP-Innowax, and flame ionisation detector. Samples were injected in splitless mode. This method was applied in a stomatological clinic to healthy volunteers to whom superior-posterior alveolar nerve block anesthesia with mepivacaine was administered.     

Determination of unchanged clobazam in plasma by gas-liquid chromatography

A method has been developed for gas-chromatographic determination of clobazam in human plasma using a nitrogen-selective detector. The unchanged drug was extracted from the plasma at pH 9 by benzene. The method used methyl-1-clonazepam as internal standard. Calibration graphs were linear in the range of 20 to 10,000 ng/ml. The recovery of the compound was 102.29%. The sensitivity of the method was adequate for determination of the drug at toxic concentrations and at therapeutic doses. It was a simple, rapid, reproductible method for determination of clobazam and most of the commercialized benzodiazepines. The method has been tested in a few number of clinicals cases. No interferences occurred in plasma from patients treated with various drugs.     

A micromethod for the on-column methylation of valproic acid by gas-liquid chromatography

We described a simple procedure for the flash heater methylation of valproic acid and cyclohexylacetic acid (internal standard) by gas-liquid chromatography (GLC). A small volume (100 microL) of sample is acidified with 10% perchloric acid and extracted into hexane. An aliquot is back extracted into 5% tetramethylammonium hydroxide (TMH). A 1 microL sample of the TMH layer is injected into the GLC equipped with flame ionization detector (FID) and a 6 ft x 2 mm i.d. - nickel column packed with 3% OV-17 on 80/100 mesh Supelcoport. The injector temperature is set at 350 degrees C to ensure methylation. Recoveries are greater than 95% of theoretical value. The linearity for calibration points between 15 and 180 microgram/mL is excellent (coefficient of correlation and determination greater than 0.9999). The procedure is rapid and sensitive and does not require a dedicated column in the gas chromatograph.     

Determination of fluconazole in human serum by solid-phase extraction and reversed-phase high-performance liquid chromatography.

A simple, rapid, and accurate reversed-phase octadecylsilyl high-performance liquid chromatographic method using solid-phase column extraction is described for measuring fluconazole in human serum. The column eluent was monitored by ultraviolet absorption at 210 nm. Fluconazole was extracted from diluted serum by adsorption on a small Bond-Elut C18 cartridge after the addition of UK48,134 as the internal standard and recovered by elution with methanol. The methanol was then evaporated to dryness and the residue reconstituted in 200 microliters of mobile phase and filtered prior to injecting an aliquot (50 microliters) onto an Adsorbosphere C18 column (4.6 x 250 mm, 5 microns particle size), using a mobile phase of 25 mM tris(hydroxymethyl)aminomethane-phosphate buffer (pH 7.0):acetonitrile (75:25, vol/vol). The retention times were 6.6 min for fluconazole and 9.0 min for the internal standard. The assay was precise, with inter- and intraassay coefficients of variation of less than or equal to 2.9% and less than or equal to 2.1%, respectively, and with good linearity (r = 1.000) in the range of 0.1 to 25 micrograms/ml. The duration of each analysis was 15 min and the minimum detectable serum concentration was 0.1 microgram/ml.     

Determination of celecoxib in human plasma using solid-phase extraction and high-performance liquid chromatography

A simple reversed phase high-performance liquid chromatography (HPLC) method was developed for determination of celecoxib levels in human plasma. The procedure involves solid-phase extraction of celecoxib and the internal standard (SC-236) from plasma using C(18) extraction cartridges. The chromatographic separation of celecoxib and SC-236 was achieved with a Nova Pak C(8) column (3.8 mm x 150 mm) eluted with a mobile phase consisting of acetonitrile-tetrahydrofuran-sodium acetate buffer (pH 5.0) in the ratio of 30:8:62. An ultraviolet light detector with the wavelength set at 215 nm was employed for detection. Celecoxib was well resolved from the plasma constituents and the internal standard. The extraction recovery of celecoxib and SC-236 from human plasma was greater than 88%. Linear calibration curves were established over a concentration range of 40-4000 ng/ml when 0.25 ml aliquots of plasma were used. The inter- and intra-day R.S.D. for the assay was less than 12 and 5%, respectively. This assay has been applied to the analysis of celecoxib levels in plasma samples collected from healthy participants entered into a Phase II clinical study.     

Determination of atazanavir in human plasma using solid-phase extraction and high-performance liquid chromatography

Atazanavir is a new HIV-1 protease inhibitor. A simple high-performance liquid chromatographic method using UV detection was developed and validated for the analysis of atazanavir in human plasma. The sample clean up was carried out using solid-phase extraction with OASIS MCX cartridge. The chromatographic separation was achieved on a Kromasil C18 (150 mm x 3 mm, 5 microm) column with a mobile phase consisting of acetonitrile and water (38:62 v/v) delivered isocratically. The effluent of the column was monitored at a wavelength of 210 nm. The assay was linear over the concentration range of 0.156 to 10 microg/ml and the limit of quantification was 0.156 microg/ml. The method was also validated with respect to recovery, precision, accuracy and specificity. This method is suitable for therapeutic drug monitoring of atazanavir and can be easily reproduced with standard equipment.     

高效液相色谱法测定丙戊酸血浓度

本文建立了采用BrMMC将丙戊酸转化为可紫外检测的酯,再经RP-HPLC测定的丙戌酸血浓度测定方法.在15-200μg/ml范围内,峰高比与浓度呈良好的线性关系,r=0.9991;平均回收率为101.2%.方法准确、灵敏、选择性强、重现性好,操作简便快速.应用于34例患者的治疗药物监测,取得良好的临床效果,本法适于临床研究与应用.     

Determination of valproic acid in human serum by high-performance liquid chromatography with fluorescence detection.

A simple and highly sensitive high-performance liquid chromatographic method is described for the determination of valproic acid in human serum. The method is based on the direct derivatization of serum sample with 6,7-methylenedioxy-1-methyl-2-oxo-1,2-dihydroquinoxaline-3-ylpr opionohydrazide. The derivatization reaction proceeds in aqueous solution in the presence of pyridine and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide at 37 degrees C. The resulting derivatives were separated on a reversed-phase column (YMC Pack ODS-A) with isocratic elution and were fluorimetrically detected at 440 nm with excitation at 365 nm. The detection limit (signal-to-noise ratio=3) for valproic acid added to serum sample was 0.1 microg (700 fmol)/ml serum sample (2.3 fmol on column). The method was applied to determine the unbound- and total-valproic acid levels in the serum obtained from three healthy volunteers after oral administration of the drug (600 mg).     

Determination of ribavirin in serum using highly selective solid-phase extraction and high-performance liquid chromatography

A rapid assay for determination of ribavirin in serum using solid-phase extraction (SPE), high-performance liquid chromatography (HPLC), and UV-detection was developed. The SPE uses phenylboronic acid columns with an approximately 100% recovery for ribavirin. The concentration-peak area relation was linear (r > 0.995), from 1 to 64 microM in 100 microL serum. The limit of detection was 0.1 microM. The intraassay CV was 3.2% at treatment levels (9.7 microM) and 11.5% at 0.4 microM. The method is used to monitor patients undergoing ribavirin treatment for hepatitis C (HCV). Samples from HCV-infected patients with and without renal dysfunction have been analyzed without interference of endogenous compounds. It is concluded that the method is useful for routine therapeutic drug monitoring.     

Determination of amphotericin B in human plasma using solid-phase extraction and high-performance liquid chromatography

A rapid and selective HPLC method is described and validated for measuring amphotericin B (AB) in plasma. The procedure involves the solid phase extraction of AB from plasma by incorporating 1-amino-4-nitronaphthalene as an internal standard during the last elution step in extraction followed by HPLC analysis with UV detection at 407 nm. The chromatographic separation is achieved in less than 10 min on a reversed-phase C-18 column using acetonitrile-disodium edetate (20 mM) (45:55, v/v) at pH 5.0 as eluent. A linear response over the concentration range of 0.0100--2.00 microg ml(-1) is obtained having a detection limit of 0.00500 microg ml(-1) for AB. The mean extraction recovery is found to be 98.1+/-1.1% (n=15). The within-day and day-to-day R.S.D. were less than 2% (n=15) and 6.54% (n=45) respectively. This method is applied for quantifying AB trough levels in the plasma of cancer patients who have been on antifungal therapy with AmBisome. It can further be applied either for AB therapeutic monitoring or single/multiple pharmacokinetic analysis of AB in plasma.     

Determination of cotinine in biological fluids of non-smokers by packed column gas-liquid chromatography

A method is described for the analysis of cotinine in plasma, saliva and urine using packed-column gas-liquid chromatography, which is sufficiently sensitive and reproducible for quantitative study of the low levels resulting from exposure of non-smokers to other people's smoke. The lower limit of detection of cotinine in these fluids was 100 pg ml-1. The coefficient of variation over the range 0.25 to 2.0 ng ml-1 averaged 7.7%. In a sample of 85 non-smokers the concentrations of cotinine in plasma correlated 0.82 with those in urine and saliva, while the correlation between the saliva and urine concentrations was 0.91. Saliva cotinine concentrations were quantitatively related to passive exposure to parental smoking in a population study of 569 non-smoking schoolchildren.