Validated enantiospecific LC method for determination of (R)-enantiomer impurity in (S)-efavirenz

A high-performance liquid chromatographic method was developed for separation of the enantiomers of efavirenz. The developed method was applied for the determination of (R)-enantiomer in (S)-efavirenz and satisfactory results were achieved. The base line separation with a resolution of more than 4.0 was achieved on Chiralcel OD (250 mm x 4.6 mm, 10 microm) column containing tris-(3,5-dimethylphenylcarbomate) as stationary phase. The mobile phase consists of n-hexane: isopropyl alcohol (80:20 v/v) with 0.1% (v/v) of formic acid as additive. The flow rate was kept at 1.0 ml/min and the UV detection was monitored at 254 nm. The (R)-enantiomer was found linear over the range of 0.1 microg/ml--6 microg/ml. The limit of detection (LOD) was 0.03 microg/ml and the limit of quantification (LOQ) was 0.1 microg/ml (n=3. The precision of (R)-enantiomer at LOQ level was evaluated through six replicate injections and the RSD of the peak response was achieved as 1.34%. The results demonstrated that the developed LC method was simple, precise, robust and applicable for the purity determination of efavirenz.     

Determination of dexamethasone acetate in cream by HPLC

The aim of this research was to validate a high performance liquid chromatographic method for the quantitative determination of dexamethasone acetate contained in cream preparation. A MetaSil octadecyl silane (250 x 4.6 mm, 5 microm) column, a methanol: water (65:35; v/v) mobile phase (1.0 ml min(-1)) and an UV detector (set at 254 nm) were used to evaluate the parameters: linearity, precision, accuracy, specificity, as well as, quantitation and detection limits. The calibration curve showed a correlation coefficient of 0.9999. The precision was demonstrated by the relative standard deviation (RSD) of 0.53. The recovery test resulted in an average of 97.85%, what confirmed the accuracy of the method. The quantitation and detection limits determined were 1.41 and 0.47 microg ml(-1), respectively. The specificity test showed there was no interference in the drug peak.     

Quantitative determination of insulin entrapment efficiency in triblock copolymeric nanoparticles by high-performance liquid chromatography

A rapid and effective isocratic chromatographic procedure was described in this paper for the determination of insulin entrapment efficiency (EE) in triblock copolymeric nanoparticles using reversed-phase high-performance liquid chromatography (RP-HPLC) with an ultraviolet/visible detector at low flow rate. The method has been developed on a Shimadzu Shim-pack VP-ODS column (150 mm x 4.6 mm, 5 microm, Chiyoda-Ku, Tokyo, Japan) using a mixture of 0.2 M sodium sulfate anhydrous solution adjusted to pH 2.3 with phosphoric acid and acetonitrile (73:27, v/v) as mobile phase at the flow rate of 0.8 ml min(-1) and a 214 nm detection. The method was validated in terms of selectivity, linearity, precision, accuracy, solution stability, limit of detection (LOD) and limit of quantification (LOQ). The calibration curve was linear in the concentration range of 2.0-500.0 microg ml(-1), and the limits of detection and quantitation were 8 and 20 ng, respectively. The mean recovery of insulin from spiked samples, in a concentration range of 8-100 microg ml(-1), was 98.96% (R.S.D.= 2.51%, n = 9). The intra- and inter-assay coefficients of variation were less than 2.24%. The proposed method has the advantages of simple pretreatment, rapid isolation, high specificity and precision, which can be used for direct analysis of insulin in commercially available raw materials, formulations of nanoparticles, and drug release as well as stability studies.     

Development and Validation of a Reversed-phase HPLC Method for the Determination of Hydroxybenzene in a Cream Formulation

A rapid, sensitive and specific reversed-phase high performance liquid chromatographic method with diode-array detection has been developed and validated for the determination of hydroxybenzene (0.494%, w/w) in a commercially available cream pharmaceutical formulation. Isocratic chromatography was performed on a C18 column with methanol-water 60:40 (v/v) containing 0.1% phosphoric acid (v/v) as mobile phase at a flow rate of 1.0 ml/min. UV detection was at 254 nm. Linearity of the method was excellent (r(2) = 0.9999). The relative standard deviation values for intra- and inter-day precision studies were < 1% and the recovery of hydroxybenzene was >99%. The limit of detection and quantitation for hydroxybenzene was found to be 13.5 η g/ml and 2 μg/ml, respectively. The method was also validated for specificity and robustness. The method was found to be robust and can be reliably used to determine the hydroxybenzene content of marketed formulations.     

A stability-indicating HPLC method for the determination of glucosamine in pharmaceutical formulations

A stability-indicating high performance liquid chromatographic (HPLC) method was developed for the assay of glucosamine in bulk forms and solid dosage formulations. The HPLC separation was achieved on a Phenomenex Luna amino column (150 mm x 4.6 mm, i.d., 5 microm particle size) using a mobile phase of acetonitrile-phosphate buffer (75:25, v/v, pH 7.50) at a flow rate of 1.5 ml min(-1) and UV detection at 195 nm. The method was validated for specificity, linearity, solution stability, accuracy, precision, limit of detection, and limit of quantitation. The detector response for glucosamine hydrochloride was linear over the selected concentration range from 1.88 to 5.62 mg ml(-1) with a correlation coefficient 0.9998. The accuracy was between 98.9 and 100.5%. The precision (R.S.D.) amongst six sample preparations was 1.1%. The limit of detection and the limit of quantitation are 0.037 and 0.149 mg ml(-1), respectively. The sample and standard solutions were stable for 1 week. The method was successfully used for analysis of active-excipient compatibility samples used for development of a solid dosage formulation in our laboratory and subsequent stability studies. The method was also used for the analysis of glucosamine in several commercially available solid dosage forms.     

Quantitative determination and sampling of azathioprine residues for cleaning validation in production area

Cleaning validation is an integral part of current good manufacturing practices in any pharmaceutical industry. Nowadays, azathioprine and several other pharmacologically potent pharmaceuticals are manufactured in same production area. Carefully designed cleaning validation and its evaluation can ensure that residues of azathioprine will not carry over and cross contaminate the subsequent product. The aim of this study was to validate simple analytical method for verification of residual azathioprine in equipments used in the production area and to confirm efficiency of cleaning procedure. The HPLC method was validated on a LC system using Nova-Pak C18 (3.9 mm x 150 mm, 4 microm) and methanol-water-acetic acid (20:80:1, v/v/v) as mobile phase at a flow rate of 1.0 mL min(-1). UV detection was made at 280 nm. The calibration curve was linear over a concentration range from 2.0 to 22.0 microg mL(-1) with a correlation coefficient of 0.9998. The detection limit (DL) and quantitation limit (QL) were 0.09 and 0.29 microg mL(-1), respectively. The intra-day and inter-day precision expressed as relative standard deviation (R.S.D.) were below 2.0%. The mean recovery of method was 99.19%. The mean extraction-recovery from manufacturing equipments was 83.5%. The developed UV spectrophotometric method could only be used as limit method to qualify or reject cleaning procedure in production area. Nevertheless, the simplicity of spectrophotometric method makes it useful for routine analysis of azathioprine residues on cleaned surface and as an alternative to proposed HPLC method.     

Determination of mianserin in human plasma by high performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI/MS): application to a bioequivalence study in Chinese volunteers

This study aims to develop a standard protocol for the bioequivalence study of mianserin hydrochloride tablets--a tetracyclic antidepressant drug. For this purpose, a rapid, convenient and selective method using high performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC-ESI/MS) has been developed and validated to determine mianserin in human plasma. Mianserin and the internal standard (I.S.), cinnarizine were extracted from plasma by N-hexane:dimethylcarbinol (98:2, v/v) after alkalinized with sodium hydroxide. LC separation was performed on a Thermo Hypersil-Hypurity C18 (5 microm, 150 mm x 2.1 mm) with the mobile phase consisting of 10mM ammonium acetate (pH 3.4)-methanol-acetonitrile (35:50:15, v/v/v) at 0.22 ml/min. The retention time of mianserin and cinnarizine was 3.4 and 2.1 min, respectively. Quadrupole MS detection and quantitation was done by monitoring at m/z 265 [M+H]+ for mianserin and m/z 369 [M+H]+ for cinnarizine. The method was validated over the concentration ranges of 1.0-200.0 ng/ml for mianserin. The recovery was 81.3-84.1%, intra- and inter-day precision of the assay at three concentrations were 9.6-11.4% with accuracy of 97.5-101.2% and the lower limit of quantitation (LLOQ) detection was 1.0 ng/ml for mianserin. The stability of compounds was established in a battery of stability studies, i.e., short-term and long-term storage stability as well as freeze-thaw cycles. This method proved to be suitable for the bioequivalence study of mianserin hydrochloride tablets in healthy human male volunteers.     

Analysis of neolignans compounds of Piper regnellii (Miq.) C. DC. var. pallescens (C. DC.) Yunck by HPLC

A high performance liquid chromatographic (HPLC) method was developed and validated for quantitative determination of neolignans in extracts of Piper regnellii var. pallescens. The analysis were carried out on a Metasil ODS column (150 mm x 4.6 mm, 5 microm) at 30 degrees C, using as mobile phase acetonitrile-water (60:40, v/v) containing 2% acetic acid. The flow rate was 1.0 ml/min and the detection was at 280 nm. The validation using conocarpan as standard demonstrated that the method presents linearity (linear correlation coefficient=0.9991), precision (relative standard deviation <5%) and accuracy (mean recovery=104.55%) in the concentration range 31.25-500 microg/ml. The limit of detection (LOD) was 1.68 microg/ml and the limit of quantitation was 5.60 microg/ml. This method allowed the identification and quantification of conocarpan, eupomatenoid-5 and eupomatenoid-6 in the hydroethanolic extracts obtained from the leaves, stems and roots by maceration process. All the extracts showed the same chromatographic profile, being that the extract of the roots presented the highest concentration of neolignans.     

A stability indicating LC method for rivastigmine hydrogen tartrate

An isocratic, reversed-phase liquid chromatographic (RPLC) method was developed for the quantitative determination of Rivastigmine hydrogen tartrate, a cholinesterase inhibitor in bulk drugs and in pharmaceutical dosage forms. The developed method is also applicable for the related substance determination of Rivastigmine hydrogen tartrate in bulk drugs. The chromatographic separation was achieved on a Waters X Terra RP18 (250 mm x 4.6 mm, 5 microm) column using aqueous 0.01 M sodium-1-heptane sulphonate (pH: 3.0 with dilute phosphoric acid)-acetonitrile (72:28, v/v) as a mobile phase. The chromatographic resolution between Rivastigmine and its potential impurity, namely (S)-3-(1-dimethylaminoethyl) phenol (Imp 1) was found to be greater than four. Forced degradation studies were performed for Rivastigmine hydrogen tartrate bulk drug using acid (0.5 N hydrochloric acid), base (0.5 N sodium hydroxide), oxidation (3% hydrogen peroxide), heat (60 degrees C) and UV light (254 nm). No degradation was observed for Rivastigmine hydrogen tartrate except in base hydrolysis and the formed degradation product was found to be Imp 1. The mass balance of Rivastigmine hydrogen tartrate was close to 100 in all the stress conditions. The limit of detection (LOD) and limit of quantification (LOQ) of Imp 1 were found to be 100 and 300 ng/ml, respectively, for 10 microl injection volume. The percentage recovery of Imp 1 in bulk drug sample was ranged from 95.2 to 104.3. The active pharmaceutical ingredient was extracted from its finished dosage form (capsule) using water. The percentage recovery of Rivastigmine hydrogen tartrate was ranged from 99.2 to 101.3 and 98.6 to 101.5 in bulk and pharmaceutical formulation samples, respectively. Rivastigmine hydrogen tartrate sample solution and mobile phase were found to be stable for at least 48 h. The developed method was validated with respect to linearity, accuracy, precision, robustness and forced degradation studies prove the stability indicating power of the method.     

Simultaneous LC determination of tizanidine and rofecoxib in tablets

A reverse phase high performance liquid chromatographic method to determine tizanidine (TZ) and rofecoxib (RF) in combination is proposed and applied to the pharmaceuticals. This method allows the determination of 0.1-0.5 microg/ml of TZ and 1.2-6.0 microg/ml of RF along with 10 microg/ml of nimesulide (internal standard), in a mobile phase consisting of 1% (v/v) triethylamine (pH adjusted to 2.5 using dilute orthophosphoric acid):acetonitrile in the ratio 55:45% (v/v). Detection wavelength of 303 nm and flow rate of 0.8 ml/min were fixed for the study. The limit of detection (LOD) for TZ and RF were found to be 10 and 1 ng/ml, respectively. The limit of quantification (LOQ) for TZ and RF were found to be 80 and 12 ng/ml, respectively. The amount of drug present in the tablet and the recovery studies were also carried out. The % R.S.D. of recovery studies for TZ and RF were found to be 0.0673 and 0.0146, respectively. The method is validated for accuracy, precision, ruggedness and robustness.     

A validated chiral LC method for the enantiomeric separation of Zolmitriptan key intermediate, ZTR-5

A new and accurate chiral liquid chromatographic method was described for the enantiomeric separation of ZTR-5 [(4S)-4-(4-aminobenzyl)-2-oxazolidinone, (S)-isomer], a key intermediate of Zolmitriptan in bulk drugs. The enantiomers of ZTR-5 were baseline resolved on a Chiralpak AD-H (250 mm x 4.6 mm, 5 microm) column using a mobile phase system containing hexane:ethanol (70:30, v/v). The resolution between the enantiomers was not less than four and interestingly distomer was eluted prior to eutomer. The limit of detection and limit of quantification of (4R)-4-(4-aminobenzyl)-2-oxazolidinone [(R)-isomer] were found to be 250 and 750 ng/ml, respectively, for 10 microl injection volume. The percentage recovery of (R)-isomer ranged from 92.0 to 105.6 in the bulk drug samples of ZTR-5. The validated method yielded good results regarding precision, linearity, accuracy and ruggedness. The proposed method was found to be suitable and accurate for the quantitative determination of (R)-isomer in bulk drug samples of ZTR-5.     

Development and validation of an automated method for the liquid chromatographic determination of sotalol in plasma using dialysis and trace enrichment on a cation-exchange pre-column as on-line sample preparation

A fully automated method for the determination of sotalol in human plasma was developed, involving dialysis through a cellulose acetate membrane, clean-up and enrichment of the dialysate on a strong cation-exchange pre-column and subsequent liquid chromatographic (LC) analysis with UV detection. All sample handling operations were carried out by means of an ASTED system. Before starting dialysis, the trace enrichment column (TEC) was conditioned. The plasma sample, to which the internal standard (atenolol) was automatically added, was then loaded in the donor channel and was kept static while the dialysis liquid, consisting of 0.017 M acetic acid, was passed through the acceptor channel in successive pulses. After each pulse, the dialysate was dispensed onto the TEC. When dialysis was discontinued, the analytes were eluted from the TEC by the LC mobile phase by rotation of a switching valve and transferred to the analytical column packed with octyl silica. The LC mobile phase was a mixture of methanol and pH 7.0 phosphate buffer containing 1-octanesulfonate at a concentration of 7.5×10⁻⁴ M (19:81; v/v). The UV detection was performed at 230 nm. The influence of several parameters of the dialysis and trace enrichment processes on analyte recovery and method selectivity was investigated. The method was then validated. The mean absolute recovery for sotalol was about 60%. The limit of quantitation was 25 ng/ml and R.S.D. for repeatability and intermediate precision obtained at a concentration level of 50 ng/ml were 4.3 and 5.8%, respectively.     

RP-HPLC determination of recombinant human interferon omega in the Pichia pastoris fermentation broth

A rapid and valid reversed-phase high performance liquid chromatography (RP-HPLC) method for determination of recombinant human interferon omega (rhIFNomega) in the yeast Pichia pastoris fermentation broth was developed. The method is based on the hydrophobicity of rhIFNomega followed by RP-HPLC separation with UV detection. The chromatography analysis was performed on EC 250/4 NUCLEOSIL 300-5 C18 (250 mm x 4 mm i.d., 300 A, with a particle size of 5 microm) column. The compositions of the mobile phase A and B were 999:1 (v/v) water/TFA and 999:1 (v/v) acetonitrile/TFA at a flow rate of 1.0 ml min(-1). Detection was done by spectrophotometry at 280 nm and the column temperature was 30+/-1 degrees C. Calibration curve was linear (r=0.9986, n=7) in the range of 0.074-0.555 mg ml(-1) for rhIFNomega and the regression equation was y=2.02 x 10(6)x-1.27 x 10(5). Limit of detection for rhIFNomega was 0.053 mg ml(-1). The values of R.S.D. (%) of intra-day and inter-day precision were <5.65 and <5.68 (n=6), respectively. The R.S.D. (%) values and the average recovery rate of recovery experiment were <1.23 (n=3) and 97.97%.     

Development and Validation of Stability-indicating High Performance Liquid Chromatographic Method for the Estimation of Everolimus in Tablets

The present study depicts the development of a validated reversed-phase high performance liquid chromatographic method for the determination of the everolimus in presence of degradation products or pharmaceutical excipients. Stress study was performed on everolimus and it was found that it degrade sufficiently in oxidizing and acidic conditions but less degradation was found in alkaline, neutral, thermal and photolytic conditions. The separation was carried out on Hypersil BDS C18 column (100×4.6 mm, 5 μ) column having particle size 5 μ using acetate buffer:acetonitrile (50:50 v/v) with pH 6.5 adjusted with orthophosphoric acid as mobile phase at flow rate of 1 ml/min. The wavelength of the detection was 280 nm. A retention time (R_t) nearly 3.110 min was observed. The calibration curve for everolimus was linear (r²=0.999) from range of 25-150 μg/ml with limit of detection and limit of quantification of 0.036 μg/ml and 0.109 μg/ml, respectively. Analytical validation parameters such as selectivity, specificity, linearity, accuracy and precision were evaluated and relative standard deviation value for all the key parameters were less than 2.0%. The recovery of the drug after standard addition was found to be 100.55%. Thus, the developed RP-HPLC method was found to be suitable for the determination of everolimus in tablets containing various excipients.     

RP-HPLC法测定环吡酮胺发用洗剂的含量

目的建立环吡酮胺发用洗剂的含量测定方法。方法以WatersXTerraRP18(4.6mm×250mm,5μm)为色谱柱,乙腈-0.1%乙二胺四醋酸二钠(含0.05%冰醋酸)(0.60:0.40)为流动相,流速为1ml/min,检测波长为304nm,采用反相高效液相色谱法测定其含量。结果环吡酮胺浓度在20.0～240.0μg/ml范围内线性关系良好(r=0.9999,n=5);平均回收率为101.0%;RSD为0.98%(n=6)。结论本方法简便、灵敏、准确,可用于发用洗剂的质量控制。     

Direct determination of s-carboxymethyl-l-cysteine in syrups by reversed-phase high-performance liquid chromatography

A simple reversed-phase high-performance liquid chromatography method was developed for the determination of s-carboxymethyl-l-cysteine in syrup preparations. The experiments were performed without specific sample pre-treatment. The LC conditions used were acetonitrile-10 mM sodium dihydrogenphosphate buffer, pH 2.0 (1:99, v/v) on a C(18) Inersil column with a flow rate of 1.5 ml/min. Ultraviolet detection was carried out at 240 nm. The method showed excellent linearity (r(2)>0.9998) over the concentration range tested (0.8-25.6 mg/ml) with good precision and accuracy (%R.S.D. 0.7%). Recoveries were good (>99%) with a limit of detection and limit of quantitation of 0.1 and 0.8 mg/ml. Other compositions in the syrup vehicle did not interfere the analysis of s-carboxymethyl-l-cysteine.     

Determination and pharmacokinetics of isoferulic acid in rat plasma by high-performance liquid chromatography after oral administration of isoferulic acid and Rhizoma Cimicifugae extract

A simple and specific high-performance liquid chromatographic (HPLC) method with ultraviolet (UV) absorbance detection has been developed for the determination of isoferulic acid in rat plasma. The plasma samples were deproteinized with methanol after the addition of internal standard (IS) tinidazole. The analysis was performed on a Kromasil C18 column (250 mm x 4.6 mm i.d., 5 microm particle size) with acetonitrile-0.05% phosphoric acid (25:75, v/v) as mobile phase. The linear range was 0.0206-5.15 microg ml(-1) and the lower limit of quantification (LLOQ) was 0.0206 microg ml(-1). The intra- and inter-day relative standard deviations (R.S.D.s%) were less than 11.4 and 12.3%, respectively, and accuracy as relative error (R.E.%) between -6.7 and -1.1%. Mean extraction recovery was above 80%. The validated method was successfully applied to the pharmacokinetic study of isoferulic acid in rat plasma after oral administration of isoferulic acid and Rhizoma Cimicifugae extract.     

HPLC-ELSD法测定复方苦参洗剂中苦参碱的含量

目的建立复方苦参洗剂中苦参碱的含量测定方法。方法采用高效液相-蒸发光散射检测法测定苦参碱的含量。Hypersil NH2色谱柱（250mm×4．6mm,5μm）,乙腈旬．1％的三乙胺（68：32）为流动相,流速1．0ml·min^-1,柱温25℃。ELSD参数为：漂移管温度94．4℃,载气流速2．4L·min^-1。结果苦参碱质量（X）的对数值与色谱峰面积（Y）的对数值之间呈良好的线性关系,回归方程为lgY=0．908 lgX＋5．64,r=0．9999,线性范围为0．3456—5．184μg,检测限为0．0432μg,定量限为0．1296μg,平均回收率为98．36％（RSD为0．82％）。结论本法操作简便,结果准确,重现性好,可用于测定苦参碱的含量。     

柑柏止痒浴液的质量标准研究

目的:建立柑柏止痒浴液的质量标准。方法:采用薄层色谱(TLC)法对处方中薄荷脑和黄柏进行定性鉴别;采用高效液相色谱法测定黄柏中盐酸小檗碱的含量:色谱柱为Agilent Eclipse Plus C18(100 mm×4.6 mm,5μm),流动相为甲醇-0.03 mol/ml乙酸铵溶液(45∶55,V/V),检测波长为346 nm。结果:TLC图专属性强,阴性对照无干扰。盐酸小檗碱的质量浓度在1²00μg/ml范围内与峰面积积分值呈良好的线性关系(r=0.999 8);精密度、稳定性、重复性试验的RSD<2%;平均加样回收率为100.28%,RSD=1.58%(n=6)。结论:所建标准可用于柑柏止痒浴液的质量控制。     

HPLC法测定双唑乳膏中克霉唑与硝酸益康唑的含量

目的：建立高效液相色谱法测定双唑乳膏中克霉唑与硝酸益康唑的含量.方法：采用高效液相色谱法,色谱柱为Alltech Alltima C18色谱柱（150 mm×4.6 mm,5 μm）,流动相为磷酸盐缓冲液（取磷酸二氢钾与磷酸氢二钾各2.5 g,加水溶解并稀释至1000 ml）-甲醇（25∶75）,流速为1.0 ml/min,柱温为35 ℃,检测波长为232 nm.结果：克霉唑与硝酸益康唑在0.25~100 μg/ml范围内,浓度与其峰面积呈良好线性关系（r=0.9999,n=9）,平均回收率分别为99.87%与101.11%,RSD%分别为1.4%与1.8%.结论：为双唑乳膏中克霉唑与硝酸益康唑联合用药的新剂型建立了简单、快速、专属性强、重现性好的含量测定方法,可用于双唑乳膏中克霉唑与硝酸益康唑的测定.