1-heptanesulfonic Acid Sodium Salt Research Articles

Liquid Chromatographic Method for Irinotecan Estimation: Screening of P-gp Modulators.

The present work is aimed to develop a simple, sensitive, robust and reliable HPLC method for the estimation of irinotecan in the physiological media in order to assess the permeability profile of irinotecan, using the everted gut sac, in the presence of various P-gp modulators. Separation was achieved using, C18 column with mobile phase consisting of acetonitrile and 0.045 µM sodium dihydrogen phosphate dihydrate buffer containing ion pair agent heptane sulphonic acid sodium salt (0.0054 µM), pH 3. The flow rate was maintained at 1 ml/min and analysis was performed at 254.9 nm using PDA detector. Calibration data showed an excellent linear relationship between peak-area verses drug concentration (r(2), 0.9999). Linearity was found to be in the range of 0.060-10.0 µg/ml. Limits of detection and quantification were found to ~0.020 µg/ml and ~0.060 µg/ml, respectively. The developed method was found to be precise (RSD < 1.5%, for repeatability and <2.55% for intermediate precision, acceptable ranges of precision), accurate (The recovered content of irinotecan in the presence of various P-gp modulators varied from 96.11-101.51%, within acceptable range, 80-120%), specific and robust (% RSD < 2). Developed method has been applied successfully for the evaluation of eleven P-gp modulators from diverse chemical class.

QUANTIFICATION OF ZABOFLOXACIN IN RAT PLASMA USING HPLC-UV DETECTOR AND ITS APPLICATION TO A PHARMACOKINETIC STUDY

This paper presents a simple, rapid, and sensitive method of investigating the pharmacokinetics of zabofloxacin, a fluoroquinolone antibiotic agent used to treat infections caused by multidrug-resistant Gram-positive pathogens. The method presented involves the use of high-performance liquid chromatography with ultraviolet (UV) detection without an internal standard. Zabofloxacin was separated using an isocratic elution on a Capcell Pak C18 column using an acetonitrile–methanol–phosphate buffer (1 g of KH2PO4 and 1 g of heptane sulfonic acid sodium salt in 720 mL of purified water) and a 1 M tetrabutylammonium dihydrogenphosphate solution (18.5:8.5:72:1, by volume) as a mobile phase at a flow rate of 0.25 mL/min with UV detection at 275 nm. The lower limit of quantification (LLOQ) and the upper limit of quantification (ULOQ) were 100 ng/mL and 20000 ng/mL, respectively, with acceptable linearity in the range from 100 to 20000 ng/mL (R > 0.999). The intra- and inter-day accuracy (RE) ranged from −8.2% to 1.8% and the intra- and inter-day precision (CV) ranged from 3.8% to 10.6% for zabofloxacin. In addition, stock solution stability, recovery, freeze–thaw effects, and short-term and long-term stability met the acceptance criteria. Following oral administration of zabofloxacin to rats at a dose of 250 mg/kg, the concentration of zabofloxacin was readily quantifiable in plasma samples up to 8 hr post-dose. This suggests that a validated assay can be used to study the pharmacokinetics of zabofloxacin in rats.

DEVELOPMENT AND VALIDATION OF ION PAIR-LIQUID CHROMATOGRAPHIC METHOD FOR THE SIMULTANEOUS ESTIMATION OF INDAPAMIDE AND AMLODIPINE BESYLATE IN BULK AND MULTICOMPONENT FORMULATION

The present paper report the simple, rapid, accurate and precise ion pair high performance liquid chromatographic method for the simultaneous est imation of Indapamide and Amlodipi ne Besylate in bulk and m ulticomponant formulation. The reverse - phase liquid chromatographic analysis has been performed on a Hypersil C 18 column (250 mm × 4.6mm i.d., 5 μm particle size) column with mobile phase Methanol: Acetonitrile: 0.1 M Heptane sulphonic acid sodium salt (1.5 ml triethylamine was added and pH adjusted to 3.5 with Ortho phosphoric acid ) in the ratio 20:40:40 v/v /v and column temperature at 30°C. The flow rate of the mobile phase was adjusted to 1.0 ml/ min and the injection volume was 10 μl. Detection was performed at 237 nm. The retention ti me for Indapamide and Amlodipine besylate were 4. 1 3 min and 7.64 min respectively. The method was validated and shown to be linear for indapamide and Amlodipine Besy late in 25 - 150 µg/ml (r 2 =0.999) and 100 - 6 00 µg/ml (r 2 =0.999) respectively. The relative standard deviation of Indapamide and Amlodipine besylate for intra - day was 0.2930 and 0.1218 respectively , inter - day was found to be , 0.5905 and 0.2507 respectively. K EYWORD S : Indapamide, Amlodipine Besylate, heptanes sulphonic acid sodium salt, RP - H PLC, ion pair liquid chromatography .

THE USE OF A MONOLITHIC COLUMN TO IMPROVE THE SIMULTANEOUS DETERMINATION OF CAFFEINE, PARACETAMOL, PSEUDOEPHEDRINE, ASPIRIN, DEXTROMETHORPHAN, CHLORPHENIRAMINE IN PHARMACEUTICAL FORMULATIONS BY HPLC–A COMPARISON WITH A CONVENTIONAL REVERSED-PHASE SILICA-BASED COLUMN

A new simple, rapid, and sensitive liquid chromatographic method has been developed and validated for the simultaneous determination of caffeine, paracetamol, pseudoephedrine, aspirin, dextromethorphan, and chlorpheniramine in pharmaceutical tablet formulations and was performed on conventional C18 and monolithic silica C18 columns. Chromatographic separation was achieved by using a mixture of methanol and a buffer containing 10 mM NaH2PO4, 3 mM heptane sulfonic acid sodium salt, 0.1% triethylamine, pH 2.5 (adjusted with hydrochloric acid) in a ratio 50:50 v/v, 40:60 v/v for conventional C18 and monolithic silica C18 columns, respectively. Quantitation was achieved with UV detection at 214 nm, based on peak area. The proposed method could be used in the presence of salicylic acid as impurity or decomposition product in dosage forms containing aspirin. The proposed method was validated and successfully applied for the analysis of pharmaceutical formulations and laboratory-prepared mixtures containing these multicomponent combinations.

Quantification of negundoside inVitex negundoLinn. Leaf powder by high-performance liquid chromatography

Summary An HPLC method has been developed for routine analysis of negundoside in Vitex negundo Linn. leaf extract. Separation was performed on a C18 column with 65:35 (v/v) buffer solution (containing 0.01 M potassium dihydrogen orthophosphate and 0.01 M heptane sulphonic acid sodium salt; pH 3.0)-methanol as mobile phase. Detection and quantification were achieved by use of UV and photo diode array detectors operated at 251 nm. Response was a linear function of negundoside concentration in the range 1–37.5 μg mL−1 (correlation coefficient 0.9996). The method was validated for system and method precision, accuracy, linearity, and solution stability. The method is sensitive, simple, rapid, accurate, and precise and can therefore be used for routine qualitycontrol analysis of Vitex negundo Linn. leaf powder, including quantitative analysis of negundoside.

Development and validation of a stability-indicating RP-HPLC method for the determination of paracetamol with dantrolene or/and cetirizine and pseudoephedrine in two pharmaceutical dosage forms

A stability-indicating reversed-phase high-performance liquid chromatography (RP-HPLC) method has been developed which can separate and accurately quantitate paracetamol, dantrolene, cetirizine and pseudoephedrine. The method was successfully validated for the purpose of conducting stability studies of the four analytes in quality control (QC) laboratories. The stability-indicating capability of the method was demonstrated by adequate separation of these four analytes from all the degradant peaks. A gradient mobile phase system consisting of (A) 50 mmol L −1 sodium dihydrogen phosphate, 5 mmol L −1 heptane sulfonic acid sodium salt, pH 4.2 and (B) acetonitrile was used with Discovery reversed-phase HS C 18 analytical column (250 mm × 4.6 mm i.d., 5 μm particle size). Quantitation was achieved with UV detection at 214 nm, based on peak area. The proposed method was validated and successfully applied for the analysis of pharmaceutical formulations and laboratory-prepared mixtures containing the two multicomponent combinations.

Simultaneous determination of chondroitin sulfate sodium, allantoin and pyridoxine hydrochloride in pharmaceutical eye drops by an ion-pair high-performance liquid chromatography

An ion-pair high-performance liquid chromatography (HPLC) method has been developed for the simultaneous determination of chondroitin sulfate sodium (CSS), allantoin and pyridoxine hydrochloride (VB 6) in a commercial eye drops dosage form. An Alltima C 18 column (250 mm × 4.6 mm i.d., 5 μm) was used for the separation at room temperature, with 25 mM ammonium dihydrogen phosphate (containing 0.01% heptanesulfonic acid sodium salt) and acetonitrile (95:5, v/v) as the mobile phase at the flow rate of 0.5 mL min −1. The detection wavelength for CSS, allantoin and VB 6 was 195 nm, 215 nm and 291 nm, respectively. The method showed good linearity for CSS, allantoin and VB 6, with correlation coefficients greater than 0.9996, in the range of 203.96–815.84 mg L −1, 371.16–1488.64 mg L −1, and 23.32–93.28 mg L −1, respectively. The instrumental and method precisions were adequate with all relative standard deviations lower than 2.0%. The accuracy of this method, measured by the recovery of three compounds from spiked placebo solutions, was from 99.01% to 101.92%. The three components, CSS, allantoin and VB 6 were well separated from other ingredients and degradation products. This method is fast, simple, and can be used for direct and simultaneous determination of CSS, allantoin and VB 6 in the pharmaceutical preparation.

Validated, Stability-Indicating LC Method for Analysis of Pipenzolate Bromide and Its Hydrolysis Products

A liquid chromatographic method has been developed and validated for quantitative analysis of pipenzolate bromide (PP), its hydrolysis products, and phenobarbitone, sodium benzoate, and sodium saccharine. A 5-μm particle ODS column was used with acetonitrile–KH2PO4 (10 mm, pH 3.5) 40:60 (v/v), containing 5 mm heptanesulfonic acid sodium salt, as mobile phase. Quantitation was achieved by UV detection at 210 nm, on the basis of peak area. Forced degradation studies were performed on a bulk sample of PP using 0.1 M hydrochloric acid, 0.01 M sodium hydroxide, 0.33% hydrogen peroxide, heat (70 °C), and photolytic degradation. The proposed LC method was used to study the kinetics of acidic hydrolysis and pH-rate profiles of hydrolysis of PP in Britton–Robinson buffer solutions.

Simultaneous Determination of Phenylephrine Hydrochloride, Guaifenesin, and Chlorpheniramine Maleate in Cough Syrup by Gradient Liquid Chromatography

A simple and reliable high-performance liquid chromatographic method was developed for the simultaneous determination of mixture of phenylephrine hydrochloride (PHENYL), guaifenesin (GUAIF), and chlorpheniramine maleate (CHLO) either in pure form or in the presence of methylparaben and propylparaben in a commercial cough syrup dosage form. Separation was achieved on a C8 column using 0.005 M heptane sulfonic acid sodium salt (pH 3.4 +/- 0.1) and acetonitrile as a mobile phase by gradient elution at different flow rates, and detection was done spectrophotometrically at 210 nm. A linear relationship in the range of 30-180, 120-1800, and 10-60 microg/mL was obtained for PHENYL, GUAIF, and CHLO, respectively. The results were statistically analyzed and compared with those obtained by applying the British Pharmacopoeia (2002) method and showed that the proposed method is precise, accurate, and can be easily applied for the determination of the drugs under investigation in pure form and in cough syrup formulations.

Characterization of the Metabolic Activation of Hepatitis C Virus Nucleoside Inhibitor β-d-2′-Deoxy-2′-fluoro-2′-C-methylcytidine (PSI-6130) and Identification of a Novel Active 5′-Triphosphate Species

beta-D-2'-Deoxy-2'-fluoro-2'-C-methylcytidine (PSI-6130) is a potent inhibitor of hepatitis C virus (HCV) replication in the subgenomic HCV replicon system, and its corresponding 5'-triphosphate is a potent inhibitor of the HCV RNA polymerase in vitro. In this study the formation of PSI-6130-triphosphate was characterized in primary human hepatocytes. PSI-6130 and its 5'-phosphorylated derivatives were identified, and the intracellular concentrations were determined. In addition, the deaminated derivative of PSI-6130, beta-d-2'-deoxy-2'-fluoro-2'-C-methyluridine (RO2433, PSI-6026) and its corresponding phosphorylated metabolites were identified in human hepatocytes after incubation with PSI-6130. The formation of the 5'-triphosphate (TP) of PSI-6130 (PSI-6130-TP) and RO2433 (RO2433-TP) increased with time and reached steady state levels at 48 h. The formation of both PSI-6130-TP and RO2433-TP demonstrated a linear relationship with the extracellular concentrations of PSI-6130 up to 100 mum, suggesting a high capacity of human hepatocytes to generate the two triphosphates. The mean half-lives of PSI-6130-TP and RO2433-TP were 4.7 and 38 h, respectively. RO2433-TP also inhibited RNA synthesis by the native HCV replicase isolated from HCV replicon cells and the recombinant HCV polymerase NS5B with potencies comparable with those of PSI-6130-TP. Incorporation of RO2433-5'-monophosphate (MP) into nascent RNA by NS5B led to chain termination similar to that of PSI-6130-MP. These results demonstrate that PSI-6130 is metabolized to two pharmacologically active species in primary human hepatocytes.

New Validated Methods for the Simultaneous Determination of Two Multicomponent Mixtures Containing Guaiphenesin in Syrup by HPLC and Chemometrics‐Assisted UV‐Spectroscopy

High pressure liquid chromatographic (HPLC) and spectrophotometric methods are developed for the determination of two multicomponent mixtures containing guaiphenesin, dextromethorphane hydrobromide, and sodium benzoate together with either phenylephrine hydrochloride, chlorpheniramine maleate, and butylparaben (mixture 1) or ephedrine hydrochloride and diphenhydramine hydrochloride (mixture 2). The HPLC method depended on using an ODS column with mobile phase consisting of acetonitrile −10 mM potassium dihydrogen phosphate, pH 2.7 (40∶60 v/v) containing 5 mM heptane sulfonic acid sodium salt (for mix 1) and a cyanopropyl column with mobile phase consisting of acetonitrile −12 mM ammonium acetate, pH 5 (40∶60 v/v) (for mix 2) and UV detection at 214 nm. The cyanopropyl column is much less hydrophobic, less sterically restricted to the penetration of bulky solute molecules into the stationary phase, and has weaker hydrogen‐bond acidity than the ODS column. So the cyanopropyl column is more suitable for separation of components of mix 2. The chemometric‐assisted spectrophotometric method with, principal component regression (PCR) and partial least squares (PLS‐1) was used. For the chemometric method a calibration set of the mixture consisting of each compound in each mixture was prepared in distilled water. The absorbance data in the UV spectra were measured in the spectral region (210–240 or 210–224 nm for mix 1 and mix 2, respectively, as this range provided the greatest amount of information about the two mixture components). The spectrophotometric method does not require a separation step. The proposed methods were successfully applied for the analysis of the two multicomponents combinations in laboratory‐prepared mixtures and in commercial syrups, and the results were compared with each other.

Liquid Chromatography and Chemometric-Assisted Spectrophotometric Methods for the Analysis of Two Multicomponent Mixtures Containing Cough Suppressant Drugs

Three methods were applied for the analysis of 2 multicomponent mixtures containing dextromethorphan hydrobromide, phenylephrine hydrochloride, chlorpheniramine maleate, methylparaben, and propylparaben, together with either sodium benzoate (Mix 1) or ephedrine hydrochloride and benzoic acid (Mix 2). In the first method, liquid chromatography was used for their simultaneous determination using an ODS column with a mobile phase consisting of acetonitrile-phosphate buffer, pH 2.7 (40 + 60, v/v), containing 5mM heptanesulfonic acid sodium salt and ultraviolet (UV) detection at 214 nm. Also, 2 chemometric methods, principal component regression, and partial least squares were used. For both chemometric calibrations, a concentration set of the mixture consisting of each compound in each mixture was prepared in distilled water. The absorbance data in the UV spectra were measured for the 76 or 71 wavelength points in the spectral region 210-240 or 210-224 nm considering the intervals of deltagamma = 0.4 or 0.2 nm for Mix 1 and Mix 2, respectively. The 2 chemometric methods did not require any separation step. These methods were successfully applied for the analysis of the 2 multicomponent combinations in synthetic mixtures and in commercial syrups, and the results were compared with each other.

Determination of certain drugs in binary mixtures formulations by second derivative ratio spectrophotometry and LC

Spectrophotometric and high-performance liquid chromatographic (HPLC) methods are developed for simultaneous determination of three binary mixtures with overlapping spectra. The spectrophotometric method is based on the use of second derivative of the ratio spectra ( 2DD) for resolution of three binary mixtures of indapamide with captopril (mixture 1), cinnarizine with heptaminol acefylline (mixture 2) and amoxycillin trihydrate with flucloxacillin sodium (mixture 3). The HPLC method depends on the separation of components of binary mixtures using ODS column with mobile phase consisting of acetonitrile and 5 mM aqueous heptane sulphonic acid sodium salt in ratios of (60:40, v/v, pH 5.5) for mixture 1, (50:50, v/v, pH 3.0) for mixture 2 and (35:65, v/v, pH 4.2) for mixture 3. The proposed methods are accurate, non-destructive and successfully applied for the determination of the three binary combinations in synthetic mixtures and commercial pharmaceutical products.

Determination of two ternary mixtures containing phenobarbitone by second derivative of the ratio spectrum-zero-crossing and HPLC methods

A spectrophotometric method is developed for the determination of ternary mixtures with overlapping spectra. The method is based on the use of the second derivative of the ratio spectrum with a zero-crossing technique. The ratio spectrum was obtained by dividing the absorption spectrum of the mixture by that of one of the components. The concentration of the other components are then determined from their respective calibration graphs treated similarly. The method is accurate, non-destructive and do not require resolutions of equations. The method has been applied for the resolution of two ternary mixtures, namely, phenobarbitone, methylphenobarbitone and phenytoin (1), and phenobarbitone, papaverine HCl and piperazine acefyllinate (2). Also, a HPLC method was developed for determination of phenobarbitone, papaverine and HCL and piperazine acefyllinate. The HPLC method depends upon using ODS column with a mobile phase consisting of acetonitrile–5 mM aqueous heptane sulfonic acid sodium salt (50:50, v/v) and adjusted to apparent pH 4 using acetic acid. Quantitation was achieved with UV detection at 220 nm based on peak area. The proposed methods were applied for the determination of the two ternary combinations in synthetic mixtures and in commercial pharmaceutical products. The results obtained were precise and accurate.

Validated liquid chromatography method for assay of tizanidine in drug substance and formulated products

A new isocratic stability indicating HPLC method for determination of tizanidine in drug substance and formulated products is described. Chromatographic separation of tizanidine from the related substances and degraded products was achieved with a Hypersil CN column ( 150 mm×5.0 mm, 5 μm) using a mobile phase comprising a mixture of an ion-pairing solution of heptanesulphonic acid sodium salt (HAS), methanol and acetonitrile (50:57:18 (v/v)) within 10 min. The flow-rate was 1.0 ml/min and detection was made at 227 nm. The method has good selectivity towards tizanidine, related substances and degraded products. Limits of quantitation for tizanidine and its synthetic intermediates were determined, ranging from 0.051 to 0.54 μg/ml. The linearity range was found to be 2–20 μg/ml ( r=0.9998, n=5). Mean recovery for tizanidine from the tablets was from 99.5 to 99.8%. Precision of the method was 1.0% ( n=9). The method can be used for routine analysis and the quality control of tizanidine drug substance and its formulated products.

First derivative spectrophotometric and high-performance liquid chromatographic determination of cinchocaine hydrochloride in presence of its acid degradation product

Two methods are presented for the determination of cinchocaine HCl in presence of its acid-induced degradation product using first ( 1D) derivative spectrophotometry and high-performance liquid chromatography. Cinchocaine HCl was determined by measurement of its first derivative amplitude at the zero crossing point of 2-hydroxyquinoline-4-carboxylic acid diethylaminoethylamide as its acid degradation product (at 333.5 nm). The HPLC method depends upon using a μBondapak C 18 column at ambient temperature with a mobile phase consisting of acetonitrile—0.01 M sodium acetate trihydrate (45:55, v/v) containing 0.06% (w/v) heptane sulphonic acid sodium salt and adjusted to apparent pH 4.5 with acetic acid at a flow rate 2 ml min −1. Quantitation was achieved with UV detection at 254 nm based on peak area. The HPLC method was applied for simultaneous determination of cinchocaine HCl, methylparaben and propylparaben. The two proposed methods were successfully applied to the determination of the cinchocaine HCl in laboratory-prepared mixtures in the presence of its acid degradation product and in cream. Moreover, the proposed methods were utilized to investigate the kinetics of the acid degradation process at different temperatures and the apparent pseudo first-order rate constant, half-life and activation energy calculated.

Simultaneous determination of tenoxicam and 2-aminopyridine using derivative spectrophotometry and high-performance liquid chromatography

Derivative spectrophotometry and high-performance liquid chromatography (HPLC) were used to determine tenoxicam and one of its decomposition products (2-aminopyridine) simultaneously and in the presence of each other. The derivative procedure was based on the linear relationship between the tenoxicam concentration and the second derivative amplitudes at 390-348 nm (peak-to-trough) measurement. The 2-aminopyridine was determined through measuring the second derivative amplitude at 241 nm (zero-crossing for tenoxicam). For the HPLC procedure, a reversed-phase C8 column with a mobile phase composed of 0.02 M sodium acetate-methanol-acetonitrile (11:8:1) with 0.005 M heptane sulfonic acid sodium salt, as an ion pair, was used to separate both compounds with 2,4-dinitrochlorobenzene, as an internal standard, in reasonable time. The flow rate was 1.5 ml min−1 with a programmable ultraviolet (UV) detection at 300 and 375 nm. Both UV derivative spectrophotometric and HPLC approaches were followed for confirming the purity of tenoxicam in bulk and tablets dosage form.

Determination of α-methyldopa in human plasma by validated high-performance liquid chromatography with fluorescence detection

A sensitive reversed-phase gradient elution high-performance liquid chromatographic method with fluorescence detection has been developed for the determination of α-methyldopa (AMD) in human plasma. Separation of the investigated compound and the 3,4-dihydroxyphenylalanine (DOPA) internal standard was achieved on a Nucleosil 7 C 18 column with a 5 m M heptanesulphonic acid sodium salt containing 0.05 M potassium dihydrogenphosphate (pH 3.2)-acetonitrile mobile phase. The composition of the mobile phase was changed according to a linear gradient time program. Detection was performed at 270 nm fluorimetric excitation and 320 nm emission. The compounds were isolated from plasma by Bond-Elut C 18 solid-phase extraction. The limit of quantitation was found to be 10 ng/ml plasma. The assay was validated with respect to accuracy, precision and system suitability. All validated parameters were found to be within the 20% required limits. On the basis of the sensitivity, linearity and validation parameters the developed analytical method was found to be suitable for application in a bioequivalency study.

Hplc Assay for Phenelzine Sulfate Drug Substance and the Decomposition Product Phenethyl Alcohol Using Short Wavelength UV Detection

Abstract An HPLC procedure for the determination of phenelzine sulfate in the presence of its oxidation decomposition products expressed as phenethyl alcohol has been developed. The method uses a mobile phase consisting of 20:80 acetonitrile - 0.05 M sodium dihydrogen phosphate (pH 2.5) containing 0.02 M heptane sulfonic acid sodium salt, pumped at a flow rate of 1.0 mL/min. through a 100 mm × 4.6 mm i. d. octadecylsilane column (5 um) with UV detection at 209 nm. As little as 0.005% decomposition of phenelzine, expressed as phenethyl alcohol (134.5 pg on column), can also be detected at 209 nm. Peak height or area versus concentration of phenelzine base is linear over the range of 7.5 to 22.5 mg (r2=0.9982 for height and 0.9991 for area; n=5). Analysis of spiked samples of phenelzine gave mean percent recoveries of 101.31 ± 0.78%. Precision of the method ranged from 0.33 − 1.42% and 0.53 − 0.85% using peak height and peak area data, respectively.

Simultaneous Determination of Hydroxyzine Hydrochloride and Benzyl Alcohol in Injection Solutions by High-Performance Liquid Chromatography

A stability-indicating, high-performance liquid chromatographic method was developed for the simultaneous determination of hydroxyzine hydrochloride and benzyl alcohol in injection solutions. Separation was achieved using a μ Bondapak C18 column and the eluent [60% water, 25% acetonitrile, and 15% methanol containing 0.06% (v/v) sulfuric acid, 0.5% (w/v) sodium sulfate, and 0.02% (w/v) heptanesulfonic acid sodium salt] at a flow rate of 2ml/min. Isobutyrophenone and p-nitroacetophenone were used as internal standards. The UV detector response at 257nm was linear for hydroxyzine hydrochloride in the 3-10-mg/ml range and for benzyl alcohol in the 0.54-1.8-mg/ml range under analysis conditions. The method is accurate, simple, and precise.