Chemical stability of haloperidol injection by high performance thin-layer chromatography

The chemical stability of haloperidol lactate injection was studied under different storage conditions by high performance thin-layer chromatography (HPTLC). The study was performed at 25 +/- 2 degrees C and at refrigeration temperature (8 +/- 1 degrees C) in original glass ampoules over 15 days after being opened. The samples tested at 25 +/- 2 degrees C were stored with exposure to and protection from light. Chromatographic separation was achieved on precoated silica gel F 254 HPTLC plates using a mixture of acetone/chloroform/n-butanol/glacial acetic acid/water (5:10:10:2.5:2.5, v/v/v/v/v) as a mobile phase. Quantitative analyses were carried out at a wavelength of 254 nm. The method exhibited adequate linearity (r = 0.999), selectivity, precision (RSD = 1.92%), and accuracy (recoveries from 98.59 to 101.90%). The concentrations of all samples remained greater than or 90% of the original concentration. Haloperidol lactate injection was chemically stable under all conditions studied over 15 days.     

High performance liquid chromatographic determination of methylxanthines in canine serum, gastric and pancreatic juices

A convenient high performance liquid chromatographic method for the determination of methylxanthines in biological samples is described. Separation was achieved by reversed phase chromatography using a mobile phase consisting of tetrahydrofuran + methanol + 0.01M potassium dihydrogen phosphate, pH 3.5 (1:20:79, v/v/v), on a 7 microns C18 column and a C18 Lichrosorb precolumn at a flow rate of 0.8 mL/min. Levels varying from 0.25-16 mg/L could be detected by UV at 280 nm. In this range, standard curves were established for 4 methylxanthines: theobromine, paraxanthine, theophylline and caffeine in 4 media: mobile phase, serum, gastric and pancreatic juices, and were found to be linear (r greater than or equal to 0.9975). Overall characteristics of the method were determined as: percent recovery (89.54%), accuracy (greater than or equal to 99.4%) and reproducibility (greater than or equal to 95%). Retention times ranged from 4.21 +/- 0.01 (1-methyluric acid) to 10.8 +/- 0.03 min (caffeine). Animal experiments (5 and 10 mg/kg boluses) were used to determine caffeine half life in dog's blood (310 +/- 46 and 453 +/- 59 min, respectively) and its secretion into pentagastrin stimulated gastric juice (mean concentrations 2.51 and 6.04 mg/L; mean outputs 351 and 1206 micrograms/2.25 h; both statistically different at p less than 0.001 level).     

HPLC analysis and pharmacokinetics of icariin in rats

As a prerequisite to the determination of pharmacokinetic parameters of icariin in rats, an HPLC method using UV detection was developed and validated. Icariin and the internal standard, quercetin, were extracted from plasma samples using ethyl acetate after acidification with 0.05 mol/L NaH2PO4 solution (pH 5.0). Chromatographic separation was achieved on an Agilent XDB Cls column (250 x 4.6 mm id, 5 microm) equipped with a Shim-pack GVP-ODS C18 guard column (10 x 4.6 mm id, 5 microm) using a mobile phase of ACN/water/acetic acid (31:69:0.4 v/v/v) at a flow rate of 1.0 mL/ min. Detection was at 277 nm. The calibration curve was linear from 0.05 to 100.0 microg/mL with 0.05 microg/mL as the lower LOQ (LLOQ) in plasma. The intra- and interday precisions in terms of RSD were lower than 5.7 and 7.8% in rat plasma, respectively. The accuracy in terms of relative error (RE) ranged from -1.6 to 3.2%. The extraction recoveries of icariin and quercetin were 87.6 and 80.1%, respectively. The main pharmacokinetic parameters for rats were determined after a single intravenous administration of 10 mg/kg icariin: t1/2, 0.562 +/- 0.200 h; AUC0-infinity, 8.73 +/- 2.23 microg x h/mL; CLToT, 20.10 +/- 5.80 L/kg x h; Vz, 1.037 +/- 0.631 L/kg; MRT0-infinity, 0.134 +/- 0.040 h; and Vss, 0.170 +/- 0.097 L/kg.     

Organotin speciation in textile and plastics by microwave-assisted extraction HPLC-ESI-MS

The HPLC coupled with electrospray ionization mass spectrometry (ESI-MS) was applied for the determination of tributyltin chloride (TBT), triphenyltin chloride (TPhT), triethyltin chloride (TET) in textile and plastic samples. The separation was performed in the isocratic mode on ion exchange SCX column with a mobile phase containing methanol-ammonium acetate (50 mmol l(-1))-acetic acid (90/9.98/0.02, v/v/v). Sensitive detection of three organotin compounds by ESI-MS was performed on the basis of multiple reaction monitoring (MRM) mode. Limits of detection were 0.4, 20, 4 ng ml(-1) for TBT, TPhT, and TET, respectively. Microwave-assisted extraction (MAE) of organotin compounds was finished in 60% (v/v) methanol aqueous solution. Under the experimental conditions used, recoveries of three organotin compounds obtained for spiked textile and plastic samples are in the range of 55-95% and the R.S.D.s are 3-9%.     

高效液相色谱-串联质谱法分析毛发中甲基苯丙胺和苯丙胺手性对映异构体

建立了高效液相色谱-串联质谱（HPLC-MS/MS）分析毛发中甲基苯丙胺与苯丙胺对映异构体的手性分离方法。采用SUPELCO Astec CHIROBIOTIC^® V2手性液相色谱柱,以甲醇-含0.1%（v/v）甲酸的20 mmol/L乙酸铵水溶液（99：1,v/v）为流动相进行手性分离。结果表明,甲醇高温水浴超声法能较好地提取苯丙胺类化合物,且峰形较好（拖尾因子>0.95）。S-（+）-甲基苯丙胺、R-（-）-甲基苯丙胺、S-（+）-苯丙胺和R-（-）-苯丙胺在15~300 ng/mg范围内线性关系良好,相关系数均大于0.99;甲基苯丙胺和苯丙胺的检出限分别为0.1 ng/mg和0.15 ng/mg,定量限分别为0.4 ng/mg和0.5 ng/mg;日内精密度均≤6.8%,日间精密度均≤11.4%。采用所建方法对50余嫌疑人毛发进行手性分析,检出单一S-（+）-甲基苯丙胺和S-（+）-苯丙胺的占70%,同时检出S-（+）-甲基苯丙胺、R-（-）-甲基苯丙胺、S-（+）-苯丙胺和R-（-）-苯丙胺的占18%。该法简单快速,精密度好,可为实际法医毒物鉴定案例中的毛发手性分析提供技术支持与科学依据。     

Determination of aromatic amines in environmental water samples using solid-phase extraction modified with sodium dodecyl sulphate and micellar liquid chromatography

Extraction and determination of seven aromatic amines in environmental water samples were performed with solid-phase extraction (SPE) and micellar liquid chromatography (MLC) using experimental design. Extraction of aromatic amines was carried out with a C₁₈ cartridge modified with sodium dodecyl sulphate (SDS). The washing solution and elution solvent for extraction of aromatic amines were aqueous solution containing 5% (v/v) acetonitrile and 5% (v/v) acetone and 3 mL methanol, respectively. The chemometrics approach was applied for the separation optimisation of these compounds using MLC. Different mobile phase compositions were used for modelling based on retention times to obtain the best separation using central composite design. The optimum mobile phase composition for separation and determination of analytes in water samples was 69 mM SDS, 9% v/v 1-propanol and pH = 6.4. Recoveries were between 84.8–93.5% with relative standard deviation (RSD) less than 5.8% (n = 5). Limits of detection and linear range were 1–4.5 and 3.1–125.0 µg/L, respectively. The proposed method was applied to determine the aromatic amines in real samples (river and well waters). Amount of 4-nitroaniline and 3-nitroaniline in river water sample were 2.15 and 1.91 µg/L, respectively.     

高效液相色谱-质谱法测定比格犬血浆中的艾普拉唑及其药代动力学

运用高效液相色谱-电喷雾质谱(HPLC-ESI-MS)技术,建立了快速、简单、灵敏的比格犬静脉滴注艾普拉唑钠盐后血药浓度的检测方法。血浆样品采用蛋白沉淀法,以丁螺环酮作为内标,色谱柱为Teknokroma Kromasil C18(100 mm×2.1 mm, 5 μm),流动相为水-甲醇-乙腈(69:8:23, v/v/v)(含0.1%的甲酸),流速0.2 mL/min,采用电喷雾(ESI)离子源以正离子方式检测。绘制血药浓度-时间曲线,并采用DAS 2.0计算药代动力学参数。方法学实验结果表明内源性杂质不干扰艾普拉唑和内标的测定,线性范围为5～10000 μg/L (r=0.994),最低定量限为5 μg/L,精密度和准确度均符合生物样品测定的要求。低、中、高3个浓度的绝对回收率在106%左右,基质效应小于142.0%,表明该方法适合比格犬血浆中艾普拉唑浓度的测定及药代动力学研究。比格犬静脉滴注艾普拉唑钠盐3个剂量(0.2 mg/kg、0.8 mg/kg和3.2 mg/kg)后的药-时曲线下面积(AUC(0~∞))分别为(2.4×104±3×103)、(8.8×104±1.6×104)和(5.4×105±8×104) μg/L•min,呈线性药物代谢动力学过程。     

Plasma and blood assay of xanthine and hypoxanthine by gas chromatography-mass spectrometry: physiological variations in humans

Plasma and blood xanthine and hypoxanthine levels were assayed using a sensitive and specific method involving gas chromatography-mass spectrometry, associated with an optimized sample preparation procedure. Physiological variation was studied in 224 subjects with no purine metabolism disorders. An age dependency for both compounds was found, comparable with that known for uric acid. The mean plasma levels for the 224 subjects were 0.65 +/- 0.24 microM for xanthine and 1.65 +/- 0.78 microM for hypoxanthine. Corresponding mean blood levels were 0.59 +/- 0.21 microM for xanthine and 1.72 +/- 0.74 microM for hypoxanthine. Plasma and blood levels were significantly different, by ca. 10%. Rapid in vitro release of hypoxanthine from erythrocytes and continuation of intraerythrocytal metabolism lead to overestimation exceeding 10% within half an hour after sample blood collection. Hence samples must be deproteinized promptly. Blood can therefore be conveniently used for oxypurine assay instead of plasma when prompt spinning of samples is difficult to manage, as is usually encountered in clinical practice.     

HPLC with fluorescence detection of urinary phenol, cresols and xylenols using 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride as a fluorescence labeling reagent.

A simple and sensitive HPLC method for the determination of phenolic compounds, i.e., phenol (Phe), cresols (Cres) and xylenols (Xyls), was developed. After a pre-column fluorescence derivatization of these compounds with 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride (DIB-Cl) at 60 degrees C for 30 min, 11 DIB derivatives were successfully separated within 50 min with an ODS column using CH3CN-H2O-CH3OH (25 + 22 + 53, v/v) as the eluent. The detection limits of DIB derivatives at a signal-to-noise ratio of 3 ranged from 0.15 to 1.09 microM (0.2-1.6 pmol per 20 microliters). The precision of the proposed method for both within- and between-day assays of free and total phenol related compounds was satisfactory (RSD < 9.5%). By the proposed method, Phe and p-Cre could be detected in normal urine samples, and the calculated concentrations of free Phe and p-Cre in unhydrolysed urine samples were 1.5 +/- 1.3 and 23.9 +/- 24.3 microM and those of total Phe and p-Cre in hydrolysed urine samples were 87.3 +/- 81.2 and 200.7 +/- 195.4 microM (n = 21), respectively.     

Simultaneous determination of gastrodin and its metabolite by HPLC

A rapid and specific HPLC method for the simultaneous determination of gastrodin and its metabolite gastrodigenin (p-hydroxybenzyl alcohol) in rat plasma, bile, liver, urine and faeces is described. The separation was achieved by using a reversed phase column (YWG-C18) eluted with methanol-water (2.5:97.5 v/v). Phloroglucinolum was used as internal standard and the peaks were detected at UV 221 nm. The protein precipitation with ethanol was a very simple and rapid method for sample preparation. The gastrodin and gastrodigenin were quantitated by measuring the peak-height ratios. There was a linear concentration range of 10-320 micrograms/mL in the assay for both compounds. The coefficients of variation (within-day) for samples spiked with gastrodin and gastrodigenin were 2.94% and 3.08%, respectively. The method demonstrated a high specificity and was suitable for use in pharmacokinetic studies.     

Determination of coenzyme Q10 in human seminal plasma by high-performance liquid chromatography and its clinical application

A high-performance liquid chromatographic (HPLC) method for the analysis of coenzyme Q10 (CoQ10) in human seminal plasma was developed and applied to investigate its clinical significance as a reference index relating to oxidative stress and infertile status of spermatozoa. After precipitation of proteins in seminal plasma with methanol, CoQ10 and coenzyme Q9 (CoQ9; internal standard) were extracted with hexane. The supernatant after centrifugation was evaporated to dryness with nitrogen at 45 degrees C. The residue was re-dissolved in isopropanol. HPLC separation of the sample solution was performed on a Lichrospher C(18) column with a mobile phase composed of isopropanol-methanol-tetrahydrofuran in the ratio of 55:39:6 (v/v/v) at a flow rate of 1.0 mL/min. Under the chromatographic conditions described, the CoQ10 and CoQ9 had retention times of approximately 5.83 and 4.97 min, respectively. The peaks were detected at UV 275 nm. Good separation and detectability of CoQ10 in human seminal plasma were obtained. The method was linear in the range 0.01-10.00 microg/mL. The relative standard deviations within- and between-assay for CoQ10 analysis were 0.85 and 1.86%, respectively. The average recoveries were 94.1-99.0% for the human seminal plasma samples. The CoQ10 levels in seminal plasma of 195 patients and 23 control subjects were studied. CoQ10 concentrations in the two populations were: 37.1 +/- 12.2 ng/mL in the fertile group and 48.5 +/- 20.4 ng/mL in the infertile group. The large difference (p < 0.01) between the fertile and infertile populations is evident.     

Chemical stability of midazolam injection by high performance liquid chromatography

The chemical stability of midazolam hydrochloride injection, undiluted or diluted with dextrose sterile solution, was studied at different storage conditions by LC. The study was performed at room temperature (23 +/- 2 degrees C) under light exposure and light protection, +8 +/- 1 degrees C and -20 +/- 0.5 degrees C, in glass and plastic containers over 14 days with midazolam hydrochloride injection, undiluted or diluted with 5% dextrose sterile solution. Chromatographic separation was carried out on a RP-18(e) column, using a mobile phase consisting of ACN-phosphate buffer (pH 3.3; 0.1 M) (30:70 v/v) at a flow rate of 1.0 mL/min and UV detection at 220 nm. The concentrations of all samples remained greater than 90% of the original concentration. The chromatographic assay exhibited an adequate linearity (r(2) >0.999), selectivity, precision (RSD <3.1), and accuracy (recoveries from 100.46 to 101.40%). Injectable midazolam hydrochloride was chemically stable in all conditions that were studied.     

Reversed-phase high performance liquid chromatographic method for the determination of lansoprazole, omeprazole and pantoprazole sodium sesquihydrate in presence of their Acid-induced degradation products

A simple sensitive, selective and accurate reversed-phase high performance liquid chromatographic method was developed and validated for the quantitative determination of lansoprazole, omeprazole and pantoprazole sodium sesquishydrate in the presence of their acid-induced degradation products. The three compounds were monitored at 280 nm using Nova-Pak C(18) column and a mobile phase consisting of 0.05 M potassium dihydrogen phosphate : methanol : acetonitrile (5 : 3 : 2 v/v/v). Linearity ranges were 2-20 mug ml(-1), 2-36 mug ml(-1) and 0.5-20 mug ml(-1) for lansoprazole, omeprazole and pantoprazole, respectively. The corresponding recoveries were 100.61+/-0.84%, 100.50+/-0.80% and 99.78+/-0.88%. The minimum detection limits were 0.55, 0.54 and 0.03 mug ml(-1) for lansoprazole, omeprazole and pantoprazole, respectively. The method could be successfully applied to the determination of pure, laboratory prepared mixtures and pharmaceutical dosage forms. The results obtained were compared with the reported methods for lansoprazole and pantoprazole or the official U.S.P method for omeprazole.     

A reversed phase high performance liquid chromatography method for the determination of fumonisins B1 and B2 in food and feed using monolithic column and positive confirmation by liquid chromatography/tandem mass spectrometry

The development of a reversed phase high performance liquid chromatography fluorescence method for the determination of the mycotoxins fumonisin B(1) and fumonisin B(2) by using silica-based monolithic column is described. The samples were first extracted using acetonitrile:water (50:50, v/v) and purified by using a C(18) solid phase extraction-based clean-up column. Then, pre-column derivatization for the analyte using ortho-phthaldialdehyde in the presence of 2-mercaptoethanol was carried out. The developed method involved optimization of mobile phase composition using methanol and phosphate buffer, injection volume, temperature and flow rate. The liquid chromatographic separation was performed using a reversed phase Chromolith(?) RP-18e column (100 mm × 4.6 mm) at 30 °C and eluted with a mobile phase of a mixture of methanol and phosphate buffer pH 3.35 (78:22, v/v) at a flow rate of 1.0 mL min(-1). The fumonisins separation was achieved in about 4 min, compared to approximately 20 min by using a C(18) particle-packed column. The fluorescence excitation and emission were at 335 nm and 440 nm, respectively. The limits of detections were 0.01-0.04 μg g(-1) fumonisin B(1) and fumonisin B(2), respectively. Good recoveries were found for spiked samples (0.1, 0.5, 1.5 μg g(-1) fumonisins B(1) and B(2)), ranging from 84.0 to 106.0% for fumonisin B(1) and from 81.0 to 103.0% for fumonisin B(2). Fifty-three samples were analyzed including 39 food and feeds and 14 inoculated corn and rice. Results show that 12.8% of the food and feed samples were contaminated with fumonisin B(1) (range, 0.01-0.51 μg g(-1)) and fumonisin B(2) (0.05 μg g(-1)). The total fumonisins in these samples however, do not exceed the legal limits established by the European Union of 0.8 μg g(-1). Of the 14 inoculated samples, 57.1% contained fumonisin B(1) (0.16-41.0 μg g(-1)) and fumonisin B(2) (range, 0.22-50.0 μg g(-1)). Positive confirmation of selected samples was carried out using liquid chromatography-tandem mass spectrometry, using triple quadrupole analyzer and operated in the multiple reaction monitoring mode.     

Sample stacking microemulsion electrokinetic capillary chromatography induced by reverse migrating pseudostationary phase for the quantification of phenobarbital and its p-hydroxyphenobarbital metabolite in rat urine

For the first time, a capillary electrophoretic (CE) method with sample stacking induced by a reverse migrating pseudostationary phase (SRMP) technique has been developed and validated for sensitive determination of phenobarbital (PB) and its p-hydroxyphenobarbital (PHPB) metabolite in rat urine samples. Separation and determination were optimized on a fused-silica capillary with a total length of 50 cm (effective length 40 cm) and 75 μm ID. The microemulsion background electrolyte consisted of 0.8% (v/v) ethyl acetate, 6.6% (v/v) butan-2-ol, 1.0% (v/v) acetonitrile, 2.0% (w/v) sodium n-dodecyl sulfate (SDS), and 89.6% (v/v) of 7.5 mM ammonium formate at pH 8. When this preconcentration technique was used, the sample stacking and the separation processes took place successively with changing the voltage with an intermediate polarity switching step. For practical application, a solid-phase extraction (SPE), C(18) sorbent with n-hexane/ethyl acetate (1?:?1%, v/v) as the elution solvent was used for sample purification and concentration. The SPE method gave good extraction yields for all the analytes, with absolute recovery values of 96.9% and 99.1% for PB and PHPB, respectively. The regression equations for PB and PHPB showed excellent linearity over a concentration range of 55-1386 ng mL(-1) for PB and PHPB (r = 0.998). The developed microemulsion electrokinetic capillary chromatography (MEEKC) method for separation of the studied compounds with SRMP as the electrophoretic preconcentration technique allowed detection limits in urine samples at 16.8 ng mL(-1) for PB and PHPB which are 15-fold lower than the reported CE method in the literature. The precision results, expressed by the intra-day and inter-day relative standard deviation (RSD) values range from 3.6 to 7.1% (repeatability) and from 3.2 to 7.2% (intermediate precision) for PB and PHPB, respectively, which were in line with Food and Drug Administration (FDA) criteria.     

Development and validation of spectrophotometric, TLC and HPLC methods for the determination of lamotrigine in presence of its impurity

Three reliable, rapid and selective methods have been developed and validated for the determination of lamotrigine in the presence of its impurity, 2,3-dichlorobenzoic acid. The first method is spectrophotometric method using p-chloranilic acid forming a colored product with lambda(max) 519+/-2 nm. All variables affecting the reaction have been investigated and the conditions were optimized. Beer's law was obeyed over a concentration range of 10-200 microg ml(-1) with mean accuracy 100.13+/-0.44%. The molar ratio of the formed ion-association complex is found to be 1 : 1 as deduced by Job's method. The conditional stability constant (K(f)), standard free energy (DeltaG), molar absorptivity(epsilon), and sensitivity index were evaluated. The second method is based on TLC separation of the cited drug (Rf=0.75+/-0.01) from its impurity (Rf=0.23+/-0.01) followed by densitometric measurement of the intact drug spots at 275 nm. The separation was carried on silica gel plates using ethyl acetate : methanol : ammonia 35% (17 : 2 : 1 v/v/v) as a mobile phase. The linearity range was 0.5-10 microg/spot with mean accuracy 99.99+/-1.33%. The third method is accurate and sensitive stability-indicating HPLC method based on separation of lamotrigine from its impurity on a reversed phase C(18) column, using a mobile phase of acetonitrile : methanol : 0.01 M potassium orthophosphate (pH 6.7+/-0.1) (30 : 20 : 50 v/v/v) at ambient temperature 25+/-5 degrees C and UV detection at 275 nm in an overall analysis time of about 6 min., based on peak area. The injection repeatability, intraday and interday repeatability were calculated. The procedure provided a linear response over the concentration range 1-12 microg ml(-1) with mean accuracy of 99.50+/-1.30%. The proposed methods were successfully applied for the determination of lamotrigine in bulk powder, in dosage form and in presence of its impurity. The results obtained were analyzed by ANOVA to assess that no significant difference between each of the three methods and the reported one. The validation was performed according to USP guidelines.     

A quantitative extraction method for the determination of trace amounts of both butyl- and phenyltin compounds in sediments by gas chromatography-inductively coupled plasma mass spectrometry

A simple and reliable extraction method was developed for quantitative determination of both butyl- and phenyltin compounds in sediments by capillary gas chromatography combined with inductively coupled plasma mass spectrometry (GC-ICP-MS). Both types of organotin compounds were extracted quantitatively from sediment by mechanical shaking into tropolone-toluene and HCl-methanol. After phase separation and pH adjustment, these organotins were ethylated with sodium tetraethylborate. The method was evaluated by analyzing PACS-2 and NIES No. 12 sediment certified reference materials. The dibutyltin (DBT; 1.14 +/- 0.02 micrograms g-1) and tributyltin (TBT; 1.01 +/- 0.04 micrograms g-1) values observed in PACS-2 sediment closely matched the certified values (DBT, 1.09 +/- 0.15; TBT, 0.98 +/- 0.13 microgram g-1 as tin). The monobutyltin (MBT) value was higher (0.62 +/- 0.02 microgram g-1) by more than two fold over the reference value (0.3 microgram g-1 as tin). The concentrations of TBT (0.18 +/- 0.04 microgram g-1) and triphenyltin (TPhT; 0.0099 +/- 0.002 microgram g-1) in the NIES No. 12 sediment were also in good agreement with the certified and reference values of TBT (0.19 +/- 0.03 microgram g-1 as compound) and TPhT (0.008 microgram g-1 as compound), respectively. Recoveries of TBT, tripentyltin (TPeT) and TPhT from spiked sediments were satisfactory (TBT, 102 +/- 3.4%; TPrT, 96 +/- 3.4%; TPhT, 99 +/- 8.5%). The detection limits as tin were in the range 0.23-0.48 ng g-1 for a 0.5 g sample size. It is also noteworthy that clean-up of the extract is not necessary because of the superior selectivity of ICP-MS detection. The present method was successfully applied to marine sediment samples.     

高效液相色谱法测定大鼠血浆中的原儿茶酸

建立了大鼠血浆中原儿茶酸含量测定的高效液相色谱方法。采用的色谱柱为DiamondsilTM C18 柱(150 mm×4.6 mm,5 μm);流动相为乙腈-水(体积比为9∶91,用H3PO4 调pH至2.5);流速1.2 mL/min;检测波长260 nm;内标为对羟基苯甲酸。原儿茶酸的线性范围为0.050~3.20 mg/L,线性相关系数为0.9978，最低定量限为0.050 mg/L,日内和日间测定的精密度（以相对标准偏差表示）均低于7.0%,准确度（以相对误差表示）为-1.4%～2.6%；在0.050,0.40,3.20 mg/L低、中、高3个添加浓度水平下，血浆样品的提取回收率分别为83.4%,87.3%,91.1%。该方法简便,灵敏,准确,适用于大鼠体内原儿茶酸的药物动力学研究。     

Evaluation of new silica‐based humic acid stationary phase for the separation of tocopherols in cold‐pressed oils by normal‐phase high‐performance liquid chromatography

A new humic acid stationary phase was prepared by immobilizing humic acid onto aminopropyl silica via an amide linkage formation and used, for the first time, for the separation and quantification of the tocopherol compounds in cold‐pressed oil samples under normal‐phase high‐performance liquid chromatography conditions. Parameters affecting the chromatographic separation such as mobile phase composition and flow rate were optimized. By evaluating the calculations of capacity factor, asymmetry factor, resolution, selectivity factor, and theoretical plate number, the best separation was obtained with isocratic elution of n‐hexane and isopropyl alcohol (99:1% v/v) at a flow rate of 1.0 mL/min. The effluent was monitored by a fluorescence detector set at excitation and emission wavelengths 295 and 330 nm, respectively. All compounds were separated in 20 min. The method was validated according to international guidelines and found to be linear in a wide concentration range, also the mean recovery of the compounds ranged from 97.9 to 99.2%, with a CV less than 2.7% in all cases. The results showed that the developed stationary phase is suitable for the separation and quantification of the tocopherol compounds in real oil samples.     

Simultaneous quantitation of rosuvastatin and gemfibrozil in human plasma by high-performance liquid chromatography and its application to a pharmacokinetic study

A simple, sensitive and specific high-performance liquid chromatography method is described for simultaneous determination of rosuvastatin (RST) and gemfibrozil (GFZ) in human plasma using celecoxib as an internal standard (IS). The assay procedure involved extraction of RST, GFZ and IS from plasma into acetonitrile. Following separation and evaporation of the organic layer the residue was reconstituted in the mobile phase and injected onto an X-Terra C(18) column (4.6 x 150 mm, 5.0 microm). The chromatographic run time was less than 20 min using flow gradient (0.0-1.60 mL/min) with a mobile phase consisting of 0.01 M ammonium acetate:acetonitrile:methanol (50:40:10, v/v/v) and UV detection at 275 nm. Nominal retention times of RST, GFZ and IS were 6.7, 13.9 and 16.4 min, respectively. Absolute recovery of both analytes and IS was greater than 90%. The lower limit of quantification (LLOQ) of RST and GFZ was 0.03 and 0.30 microg/mL, respectively. Linearity was excellent (r(2) = 0.999) in the 0.03-10 microg/mL and 0.3-100 microg/mL ranges for RST and GFZ, respectively. The inter- and intra-day precisions in the measurement of RST quality control (QC) samples 0.03, 0.09, 2.50 and 8.00 microg/mL were in the range 2.37-9.78% relative standard deviation (RSD) and 0.92-10.08% RSD, respectively. Similarly, the inter- and intra-day precisions in the measurement of GFZ quality control (QC) samples 0.30, 0.90, 25.0 and 80.0 microg/mL were in the ranges 2.79-6.27 and 0.96-9.69% RSD, respectively. Accuracies in the measurement of QC samples for RST and GFZ were in the range 85.43-107.23 and 84.98-102.35% respectively, of the nominal values. RST and GFZ were stable in the array of stability studies viz., bench-top, auto-sampler and freeze-thaw cycles. Stability of RST and GFZ was established for 1 month at -80C. The application of the assay in an oral pharmacokinetic study in rats co-administered with RST and GFZ is described.