The determination of metoclopramide in plasma by reversed-phase ion-pair high-performance liquid chromatography

Methodology based on reversed-phase ion-pair high-performance liquid chromatography is described for the determination of metoclopramide in plasma. The chromatography was optimized in terms of the peak shape for the drug and its resolution from endogenous plasma components by investigating the effects of quaternary ammonium (competing) ions and alkylsulphate (pairing) ions in an acidic mobile phase containing acetonitrile (20%) and 20 mM acetic acid. Optimum chromatographic conditions were obtained with an ODS-Hypersil column and a mobile phase containing 20% acetonitrile, 20 mM acetic acid, 0.6 mM sodium octylsulphate and 0.5 mM tetrabutylammonium chloride. A simplified method of sample preparation is described in which only 1 ml of plasma is required. The limit of detection (at 310 nm) was 7 ng/ml and no interference from endogenous plasma components or from any drugs commonly used in the treatment of cancer was observed. Consequently the methodology should be applicable to pharmacokinetic studies on metoclopramide, when used clinically to control the gastro-intestinal side-effects of chemotherapy.     

Simultaneous determination of codeine and ibuprofen in plasma by high-performance liquid chromatography

A procedure is described for the simultaneous determination of codeine and ibuprofen in human plasma following the administration of the two substances in a proposed combination dosage form. The two substances were extracted separately from plasma and then determined together by high-performance liquid chromatography (HPLC) using a fluorescence detector. The codeine was first extracted from alkalinized plasma with hexane-dichloromethane (2:1, v/v) and then washed with sodium hydroxide solution. The ibuprofen was then extracted with hexane from the plasma acidified with sulphuric acid. The organic layers were collected, evaporated to dryness and the reconstituted residue was subjected to HPLC. The detection limit for codeine was 8 microg 1(-1) and for ibuprofen 1 mg 1(-1).     

Determination of amoxycillin in plasma by ion pair column extraction and reversed-phase ion pair high-performance liquid chromatography

A quantitative method is described for the determination of amoxycillin in plasma. The method utilizes ion pair extraction of amoxycillin on disposable columns packed with Baker-10 SPE octadecyl, with tetrabutylammonium ion as the counter ion and methanol as the eluent. Separation and quantitation is performed by reversed-phase ion pair high-performance liquid chromatography (Nucleosil C-18) using the same counter ion and a mobile phase of methanol-phosphate buffer (pH 6.0) (31:69 v/v) with detection at 229 nm.     

The determination of nadolol in biological samples using high-performance liquid chromatography

A method has been developed for the determination of nadolol in biological samples by reversed-phase high-performance liquid chromatography with fluorimetric detection. The method has been applied to plasma, serum and urine samples, which are prepared by extraction with diethyl ether-dichloromethane (5:2,v/v), evaporation of the organic solvent, and dissolution of the resultant residue in the chromatographic eluent. The sample is then subjected to chromatography on a C(18)-silica column, with an eluent of water-acetonitrile-triethylamine (800:200:1,v/v) adjusted to pH 3.0 with orthophosphoric acid. A single point external standard is used for quantitation. The working ranges were 1-400 ng/ml for plasma/serum, and 0.1-40 mug/ml for urine, although a detection limit of 0.1 ng/ml appears to be readily attainable. The sample size was 0.5 ml, and for both types of sample the method showed good correlation with a previously published fluorimetric method (for plasma, r = 0.9544, n = 70; for urine, r = 0.9919, n = 35).     

A reversed-phase high-performance liquid chromatographic assay for the determination of N-acetylcysteine in aqueous formulations

A stability-indicating assay is described for the determination of N-acetylcysteine in aqueous pharmaceutical formulations. The sample is diluted to an appropriate concentration with dilute aqueous orthophosphoric acid. An aliquot of the solution, containing added l-tyrosine as an internal standard, is chromatographed using a 10-mum C(18) stationary phase with dilute orthophosphoric acid (pH 2.0) containing 0.5% w/v of sodium perchlorate as the mobile phase. The assay, which has a relative standard deviation of about 0.8%, can also be used as a test for related impurities in N-acetylcysteine. It is also suitable for determining the N-acetylcysteine content of the drug substance.     

Analysis of neomycins A, B and C by high-performance liquid chromatography with post-column reaction detection

The analysis of the antibiotics neomycins A, B and C was investigated. The separation of the components was studied using reversed-phase and reversed-phase ion-pair chromatography. The optimum separation was obtained utilizing a Lichrosorb RP-2 column with a mobile phase consisting of 75 mg/l sodium dodecyl sulphate, 0.5M Na2SO4 and 0.015 M sodium acetate buffer at pH 7.0. Using this mobile phase, baseline separation was obtained for all three compounds in approximately 20 min. Detection was via post-column derivatization of the analytes with ortho-phthalaldehyde in the presence of mercaptoethanol to form fluorescent iso-indole products. This system is applied to the analysis of a number of formulated products containing neomycin.     

Determination of the theophylline solubilizer salicylamide-O-acetic acid in serum and urine using high-performance liquid chromatography

A high-performance liquid chromatographic method for the determination of the theophylline solubilizer salicylamide-O-acetic acid has been developed in the range 0.5 to 10 microg/ml for human serum and 5 to 400 microg/ml for urine. Reversed-phase ion-pair chromatography was employed with tetrabutylammonium hydrogen sulphate as counterion and 2-nitrophenylacetic acid as internal standard. Preliminary pharmacokinetic single-dose studies show that the sensitivity and the selectivity of the assay are adequate to measure lower concentrations in the late beta-phase.     

手性荧光衍生化反相高效液相法分离DL-异丙肾上腺素

目的探讨R(-)-4-(N,N-Dimethylaminosulfonyl)-7-(3-isothiocyanatopyrrolidino)-2,1,3-benzoxadiazole(DBD-PyNCS)为手性荧光衍生化试剂,建立DL-异丙肾上腺素对映体的柱前衍生反相高效液相色谱法(RP-HPLC)高灵敏分离及分析的最佳方法。方法分别取DBD-PyNCS乙腈溶液(36mmol/L)、异丙肾上腺素对映体水溶液(1mmol/L)、20%吡啶乙腈溶液各10μL混合于聚丙烯管中,用涡旋搅拌器搅拌1min,在金属恒温仪遮光65℃条件下,反应35min。取衍生产物10μL进样于HPLC中。结果生成的非对映体衍生物(λex=460nm,λem=550nm)在流动相为乙腈-水(35∶65,v/v),流速为1.0mL/min,在Diamon-silTMC18(150mmx4.6mm,i.d.,5μm)色谱柱上分离成两个完全独立的峰,D-异丙肾上腺素、L-异丙肾上腺素的保留时间分别为26min、31min。异丙肾上腺素对映体在3.23×10-4mol/L~2.63×10-3mol/L范围内与峰面积呈良好的线性关系(r=0.9997),峰面积测定结果的相对标准偏差为1.83%(n=7),最低检测限为2.1×10-11mol/L(S/N=3)。结论利用柱前衍生反相高效液相色谱法可以使DL-异丙肾上腺素对映体得到快速、高效的分离。     

Determination of flunixin in equine plasma by reversed-phase liquid chromatography

Flunixin is determined in equine plasma by liquid chromatography on LiChrosorb RP-18 with 70% methanol in phosphate buffer pH 3.1 as the eluent, with detection at 284 nm. Plasma is deproteinized with methanol and the supernatant is then injected directly into the system. With a short pre-column (5 × 3 mm i.d.), which is replaced after 25–40 injections of sample, 420 plasma samples could be analysed on one analytical column. The detection limit in plasma is 0.30 μmol/l (89 ng/ml) and the method can be used in pharmacokinetic studies.     

Dynamically-modified silica--an alternative to reversed-phase high-performance liquid chromatography on chemically bonded phases

An alternative to the well known reversed-phase separations on chemically-bonded phases has been developed. The approach is based on a dynamic modification of bare silica with long chain quaternary ammonium ions. The influence of the concentration and type of the quaternary ammonium ion, the pH value and the ionic strength of the eluent on the selectivity towards test solutes has been investigated. The large number of parameters that can be varied in the system offers numerous possibilities by which the desired selectivity can be attained. Once established, a high degree of reproducibility of the selectivity between solutes is obtained even when using different brands of silica; this is in contrast to the situation when using chemically-bonded phases, such as, for example, different brands of octadecylsilyl-bonded silica materials.     

The combined use of high-performance liquid chromatography and radioimmunoassay for the bioanalysis of nicomorphine and its metabolites

Methods have been developed for the determination of nicomorphine using reversed-phase HPLC with UV detection; for the simultaneous assay of morphine and mononicotinoylmorphine by a coupled normal-phase HPLC-radioimmunoassay method; and for conjugates of morphine and mononicotinoylmorphine by radioimmunoassay. The methods have been evaluated and applied to a pharmacokinetic study of nicomorphine administered intramuscularly.     

Analysis of tablets containing acetylsalicylic acid and phenylephrine by high-performance liquid chromatography

A high-performance liquid chromatographic method permitted the quantitation of acetylsalicylic acid, phenylephrine, caffeine and phenacetin in tablets, and of the main impurities, salicylic acid and mono- and diacetyl derivatives of phenylephrine. A C8 reversed-phase column was used with a mobile phase containing methanol-1 M phosphoric acid—water 34:5:61 v/v/v.     

The determination of fenspiride in human plasma and urine by liquid chromatography with electrochemical or ultraviolet detection

A selective and sensitive method for the determination of fenspiride in biological fluids is described. The method involves liquid—liquid extraction followed by separation on a reversed-phase column with electrochemical detection for low levels of the drug in plasma ( 100 ng ml⁻¹) or UV absorption for higher concentrations in plasma or urine. The method is suitable for pharmacokinetic analyses and drug monitoring studies.     

高效液相色谱法测定大鼠血浆中的二氯二茂钛

目的 建立反相高效液相色谱法测定大鼠血浆中有机金属抗癌原料药二氯二茂钛的含量.方法 采用Shimadzu VP-ODS色谱柱(250×4.6 mm,5 m),V(甲醇):V(醋酸铵)=55:45,pH 2.5为流动相,流速为1.0 ml/min,紫外检测波长254 nm,柱温室温,氨基比林为内标进行测定.血浆中生物样品采用液-液萃取法进行提取.结果 二氯二茂钛在大鼠血浆中的线性范围为10～120 μg/ml,回归方程为Y=57.83X-0.6042(r=0.9991,n=7),方法精密度RSD为1.8 %(n=6),平均回收率为RSD=1.63%(n=9).结论 方法简单快速,专属性强,可用于测定大鼠血浆中二氯二茂钛的含量,为该类药物的体内血药浓度检测和动力学研究提供了实验依据.