Simultaneous Estimation of Atorvastatin Calcium, Ramipril and Aspirin in Capsule Dosage Form by RP-LC

A simple, sensitive, precise and accurate reversed phase liquid chromatographic method has been developed for the simultaneous estimation of atorvastatin (AT) calcium, ramipril (RA) and aspirin (AS) from capsule dosage form. The method was developed using a Phenomenex Luna C₁₈ (250 mm, 4.6 mm i.d., 5 µm) column with a mobile phase consisting of 0.1%, orthophosphoric acid buffer:acetonitrile:methanol (45:50:5 v/v/v), pH 3.3, at a flow rate of 1 mL min^?1. Detection was carried out with ultra-violet detection at 210 nm. The retention times were about 12.19, 2.35, and 3.95 min for AT calcium, RA and AS, respectively. The developed method was validated for linearity, accuracy, precision, limit of detection, limit of quantitation and robustness. The linearity ranges were 1–6 µg mL^?1 for AT calcium, 0.5–3 µg mL^?1 for RA and 7.5–45 µg mL^?1 for AS with mean recoveries of 100.59 ± 0.68, 100.62 ± 0.83 and 100.49 ± 0.73% for AT calcium, RA and AS, respectively. Limit of detection obtained were 29.85 ng mL^?1 for AT calcium, 4.71 ng mL^?1 for RA and 85.13 ng mL^?1 for AS. Impurity of salicylic acid was found in capsule dosage form at the retention time of about 4.84 min. The proposed method can be used for the estimation of these drugs in combined dosage forms.     

Development of Stability Indicating HPLC–UV Method for Determination of Daclatasvir and Characterization of Forced Degradation Products

A simple and sensitive stability indicating high performance liquid chromatography method was developed for quantification of Daclatasvir hydrochloride in bulk and tablet dosage forms. The analysis was performed on water symmetry analytical column (150 mm?×?3.9 mm, 5 µm), packing octyl silica (Si-[CH₂]₇-CH₃) C8. Mobile phase containing potassium phosphate buffer (pH 2.0) and acetonitrile (38: 62) v/v was used at flow rate 0.7 mL min^?1 for isocratic elution. Detection was performed on 304 nm using UV detector. The method was validated appropriately according to the requirements of United State Pharmacopeia and International Conference on Harmonization guideline Q2 (R1). Recovery, precision, linearity and specificity of the method were assured. The correlation coefficient for linearity ranged from 2 to 24 µg mL^?1 was (r?>?0.9999). The limits of detection and quantification of Daclatasvir were 0.08 and 0.28 µg mL^?1, respectively. Stability studies of Daclatasvir were performed under various stressed conditions, i.e., hydrolytic (acidic, basic and neutral), oxidation, photolytic and thermal conditions, according to International Conference on Harmonization Q1A (R2) and QIB Guidelines. The degradation products were resolved using proposed method and further characterized by MS, NMR and IR spectroscopic analyses. The proposed method was successfully applied to assay determination of bulk drugs and tablet dosage forms.     

Simultaneous Determination and Drug Dissolution Testing of Combined Amlodipine Tablet Formulations Using RP-LC

In the proposed work, the simultaneous analysis of amlodipine–rosuvastatin and amlodipine–atorvastatin in their dosage forms was achieved. Simultaneous dissolution profiles of the amlodipine–rosuvastatin and amlodipine–atorvastatin tablets are realized using Apparatus II with a simple, accurate and precise RP-LC method. The mobile phase consisting of 0.2 % H₃PO₄ and pH 5:methanol:acetonitrile (46:27:27) was used. The samples of 10 µL were injected onto a Zorbax SB C18 (100 mm, 4.6 mm, 3.5 µm particle size) column with 1.2 µL min⁻¹ flow rate. The samples were detected at 236 nm. By plotting peak area ratios vs. concentration, the linearity for amlodipine–rosuvastatin and amlodipine–atorvastatin was determined. With the developed RP-LC method, AML, ROS and ATOR were detected within the range of 0.25–10, 0.5–10 and 0.25–25 µg mL⁻¹, respectively. LOD and LOQ values were also calculated as 0.028, 0.058, 0.021 and 0.095 µg mL⁻¹, 0.195 µg mL⁻¹, 0.070 µg mL⁻¹ for AML, ROS and ATOR, respectively. System suitability tests parameters, such as capacity factor, selectivity to previous peak, selectivity to next peak, resolution to previous peak, resolution to next peak, tailing factor, theoretical number of plates, were performed and found coherent with the ICH guideline parameters. The proposed method has been extensively validated in terms of recovery, and recovery results were between 99 and 101 %. For proving the precision, between-day and within-day repeatability results of the method were proposed. The method can be used for the simultaneous determination of amlodipine–rosuvastatin and amlodipine–atorvastatin.

     

The Development and Validation of a Stability-Indicating UHPLC-DAD Method for Determination of Perindopril l-Arginine in Bulk Substance and Pharmaceutical Dosage Form

A stability-indicating ultra-high-performance liquid chromatography (UHPLC) method with a diode array detector was developed and validated for the determination of cis/trans isomers of perindopril l-arginine in bulk substance and pharmaceutical dosage form. The separation was achieved on a Poroshell 120 Hilic (4.6 × 150 mm, 2.7 µm) column using a mobile phase composed of acetonitrile–0.1 % formic acid (20:80 v/v) at a flow rate of 1 mL min⁻¹. The injection volume was 5.0 µL and the wavelength of detection was controlled at 230 nm. The selectivity of the UHPLC-DAD method was confirmed by determining perindopril l-arginine in the presence of degradation products formed during acid–base hydrolysis and oxidation as well as degradation in the solid state, at an increased relative air humidity and in dry air. The method’s linearity was investigated in the ranges 0.40–1.40 µg mL⁻¹ for isomer I and 0.40–2.40 µg mL⁻¹ for isomer II of perindopril l-arginine. The UHPLC-DAD method met the precision and accuracy criteria for the determination of the isomers of perindopril l-arginine. The limits of detection and quantitation were 0.1503 and 0.4555 µg mL⁻¹ for isomer I and 0.0356 and 0.1078 µg mL⁻¹ for isomer II, respectively.

     

Voltammetric Determination of Rosiglitazone in Pharmaceutical Preparations and Human Plasma

Abstract

The voltammetric behavior of rosiglitazone was studied using direct current (DC_t), differential pulse (DPP), and alternating current (AC_t) polarography. The drug manifests cathodic waves over a pH range of 2–11.2. In Britton‐Robinson buffer (BRb; pH 4), the diffusion current–concentration relationship was found to be rectilinear over a range of 4–24 µg · mL^?1 and 0.1–16 µg · mL^?1 using DC_t and DPP modes, respectively, with minimum limits of detection (LOD) of 0.15 µg · mL^?1 and 0.07 µg · mL^?1 using the DC_t and DDP modes, respectively. The diffusion‐current constant (I _d) was 6.63±0.03 (n=5). The proposed method was successfully applied to the determination of the studied compound both in pure form and in formulations. The mean percentage recoveries in tablets were 100.09±1.18 and 100.85±0.88 (n=5) using DC_t and DPP modes, respectively. Furthermore, the proposed method, adopting the DPP mode, was applied to the determination of rosiglitazone in spiked human plasma and the obtained mean percentage recoveries were 99.14±3.29 (n=4).     

Simultaneous HPLC–DAD Determination of Retinol and Eight Vitamin E Isomers in Human Serum

An efficient, high-performance liquid-chromatographic method with diode-array detection (HPLC–DAD) has been established for simultaneous determination of retinol, α, (β + γ), and δ-tocopherols, and α, β, γ, and δ-tocotrienols in human serum. After deproteinization, the target vitamins in serum were extracted with n-hexane and the extract was evaporated under weak nitrogen flow. The residue was redissolved in methanol and the resulting solution was used for HPLC analysis. Retinol acetate and α-tocopherol acetate were used as internal standards. The internal standard calibration curves were linear over the range of 0.010–50.0 µg mL⁻¹, with correlation coefficients >0.999. Mean recoveries of the method were 86.3–110 %, with intra-day and inter-day relative standard deviations less than 12.2 and 14.9 %, respectively. The detection limits of the method ranged from 0.001 to 0. 002 µg mL⁻¹, and the quantification limits ranged from 0.002 to 0.008 µg mL⁻¹. The method was successfully applied to analysis of the target vitamins in 50 human serum samples; all the analytes were detected at concentrations ranging from <0.002–23.0 µg mL⁻¹.

     

HPLC and UPLC Methods for the Simultaneous Determination of Enalapril and Hydrochlorothiazide in Pharmaceutical Dosage Forms

High efficiency and less elution are the basic requirements of high-speed chromatographic separation. In this study, a new gradient reverse phase chromatographic methods were developed using HPLC and UPLC systems for simultaneous determination of enalapril maleate (ENL) and hydrochlorothiazide (HCZ) in pharmaceutical dosage forms. The chromatographic separations of ENL and HCZ were achieved on a Waters μ-Bondapak C 18, (300 × 3.9 mm, 10 μm) and Waters Acquity BEH C18 (100 × 2.1 mm, 1.7 μm) columns for HPLC within 5.30 min and UPLC within a short retention time of 1.95 min, respectively. A linear response was observed over the concentration range 0.270–399 μg mL⁻¹ of ENL, 0.260–399 μg mL⁻¹ of HCZ for HPLC system and 0.270–399 μg mL⁻¹ of ENL and 0.065–249 μg mL⁻¹ of HCZ for UPLC system. Also, limit of detection for ENL was 1.848 ng mL⁻¹ and 31.477 ng mL⁻¹ for HCZ, 2.804 ng mL⁻¹ for ENL and 2.943 ng mL⁻¹ for HCZ using HPLC and UPLC, respectively. The proposed methods were validated according to ICH guideline with respect to precision, accuracy, and linearity. Forced degradation studies were also performed for both compounds in bulk drug samples to demonstrate the specificity and stability indicating power of the HPLC method. Comparison of system performance with conventional HPLC was made with respect to analysis time, efficiency, and resolution.

     

Development and Validation of a Stability-Indicating LC Method for the Determination of Rupatadine in Pharmaceutical Formulations

A reversed-phase liquid chromatography (RP-LC) method was validated for the determination of rupatadine in pharmaceutical dosage forms. The LC method was carried out on a Gemini C₁₈ column (150 mm × 4.6 mm I.D.), maintained at 30 °C. The mobile phase consisted of ammonium acetate buffer (pH 3.0; 0.01 M) with 0.05% of 1-heptanesulfonic acid–acetonitrile (71.5:28.5, v/v), run at a flow rate of 1.0 mL min⁻¹ and using photodiode array (PDA) detection at 242 nm. The chromatographic separation was obtained with retention time of 5.15 min, and was linear in the range of 0.5–400 μg mL⁻¹ (r ² = 0.9999). The specificity and stability-indicating capability of the method was proven through the degradation studies and showing also, that there was no interference of the excipients. The accuracy was 100.39% with bias lower than 0.58%. The limits of detection and quantitation were 0.01 and 0.5 μg mL⁻¹, respectively. Moreover, method validation demonstrated acceptable results for precision, sensitivity and robustness. The proposed method was applied for the analysis of pharmaceutical dosage forms assuring the therapeutic efficacy.

     

The Pharmacokinetic Profiles of Pre-Operative Prophylactic Cefepime Application in Pregnant and Non-Pregnant Women Undergoing Surgical Interventions Using a Fully Validated Liquid Chromatographic Method

Pregnancy alters pharmacokinetic profile of many drugs, because of altering body volume and metabolism rate. Therefore, dosage rates and concentrations of drugs must be controlled during pregnancy. Here, we identified the pharmacokinetic profile of pre-operatively given cefepime in caesarean section and gynecological operations using a simple, rapid, cost-effective and valid liquid chromatographic method. The chromatographic separation was performed using 40 mM, pH 3.2 phosphate buffer containing 6 % methanol as mobile phase at 0.30 mL min⁻¹ flow rate. Gradient elution with methanol was applied to get shorter analysis time without any interference from plasma endogens. During analyses, temperature of column, autosampler and detector were set as 30, 10 and 40 °C, respectively. The detection wavelength was 260 nm and ceftizoxime was used as internal standard. At the optimum conditions, the cefepime analysis from plasma samples was completed in 7 min. Cefepime was extracted from plasma samples using perchloric acid with a very high recovery rate (99.3 %). The method was fully validated according to the Food and Drug Administration guidelines for bioanalytical method validation, and found to be selective, linear, repeatable, reproducible and robust. After validation studies, the method was applied to five caesarean-sectioned and four non-pregnant sectioned women treated with pre-operative, prophylactic single intravenous dose of cefepime (1 g Maxipime^®) in order to determine pharmacokinetic profile of cefepime. Peak serum concentrations of cefepime in caesarean-sectioned women at the arterial port after infusion was 70.11 ± 10.74 μg mL⁻¹. The mean elimination half-life, volume of distribution and calculated area under the concentration–time curve (AUC)_0–∞ were 1.10 ± 0.23 h, 14.22 ± 2.29 L and 101.55 ± 10.99 μg h mL⁻¹ for caesarean-sectioned women; and 1.14 ± 0.21 h, 14.76 ± 2.92 L and 104.71 ± 36.34 μg h mL⁻¹ for non-pregnant sectioned women, respectively. The area under curve, elimination half-life, maximum plasma concentration and the mean distribution volume of cefepime were not changed in case of pregnancy.

     

Determination of the Enantiomeric Purity of Trelagliptin by Pre-Column Derivatization and Liquid Chromatography on a Chiral Stationary Phase

A precise and sensitive LC method for determination of enantiomeric purity of trelagliptin has been developed and validated. Pre-column derivatization was performed before separation. Baseline separation with a resolution factor >2.5 was accomplished within 10 min by use of a Chiralpak AD column (250 × 4.6 mm; particle size 5 µm) and n-hexane–2-propanol (90:10 v/v) as mobile phase at a flow rate of 1 mL min⁻¹. Eluted analytes were monitored by UV detection at 260 nm. The effects of mobile phase composition and temperature on enantiomeric selectivity and on resolution of enantiomers were thoroughly investigated. Calibration curves were plotted within the concentration range 0.005–2 mg mL⁻¹ (n = 12), and recoveries between 98.23 and 101.34 % were obtained, with relative standard deviation (RSD) <1.39 %. LOD and LOQ for the trelagliptin derivative were 1.51 and 5.03 µg mL⁻¹; those for its enantiomer were 1.49 and 4.94 µg mL⁻¹, respectively. The method was evaluated and validated by analysis of bulk samples of trelagliptin of different enantiomeric purity. It was demonstrated that the method was accurate, robust, and sensitive, and enabled practical analysis of real samples.

     

N‐(Substituted benzyl)‐3,5‐bis(benzylidene)‐4‐piperidones: Synthesis and Preliminary Anti‐leukemia Activity (I)

A series of novel N‐(substituted benzyl)‐3,5‐bis(benzylidene)‐4‐piperidones 5a – 5o were synthesized with substituted benzylamines as raw materials via a series of Michael addition, Dieckmann condensation, hydrolysis decarboxylation and aldol condensation. The structures were confirmed by ¹H NMR, IR, MS techniques and elemental analysis. Assay‐based antiproliferative activity study using leukemic cell lines K562 revealed that most of the title compounds have high effectiveness in inhibiting leukemia K562 cells proliferation, among which the compounds 5g (IC₅₀=7.81 µg·mL⁻¹), 5k (IC₅₀=6.35 µg·mL⁻¹), 5l (IC₅₀=7.20 µg·mL⁻¹), and 5o (IC₅₀=5.79 µg·mL⁻¹) have better inhibition activities than standard 5‐fluorouracil (IC₅₀=8.56 µg·mL⁻¹).     

LC Determination of Ketorolac in Human Plasma and Urine for Application to Pharmacokinetic Studies

A simple, specific and sensitive liquid chromatographic method has been developed for the assay of ketorolac in human plasma and urine. The clean-up of plasma and urine samples were carried out by protein precipitation procedure and liquid–liquid extraction, respectively. Separation was performed by a Waters sunfire C₁₈ reversed-phase column maintained at 35 °C. The mobile phase was a mixture of 0.02 M phosphate buffer (pH adjusted to 4.5 for plasma samples and to 3.5 for urine samples) and acetonitrile (70:30, v/v) at a flow rate of 1.0 mL min⁻¹. The UV detector was set at 315 nm. Nevirapine was used as an internal standard in the assay of urine sample. The method was validated over the concentration range of 0.05–8 and 0.1–10 μg mL⁻¹ for ketorolac in human plasma and urine, respectively. The limits of detection were 0.02 and 0.04 μg mL⁻¹ for plasma and urine estimation at a signal-to-noise ratio of 3. The limits of quantification were 0.05 and 0.1 μg mL⁻¹ for plasma and urine, respectively. The extraction recoveries were found to be 99.3 ± 4.2 and 80.3 ± 3.7% for plasma and urine, respectively. The intra-day and inter-day standard deviations were less than 0.5. The method indicated good performance in terms of specificity, linearity, detection and quantification limits, precision and accuracy. This assay demonstrated to be applicable for clinical pharmacokinetic studies.

     

Rapid and Highly Sensitive HPLC and TLC Methods for Quantitation of Amlodipine Besilate and Valsartan in Bulk Powder and in Pharmaceutical Dosage Forms and in Human Plasma

Two simple, sensitive, and specific high-performance liquid chromatography and thin-layer chromatography methods were developed for the simultaneous estimation of Amlodipine besilate (AM) and Valsartan (VL). Separation by HPLC was achieved using a xTerra C18 column and methanol /acetonitrile /water/ 0.05% triethylamine in a ratio 40:20:30:10 by volume as mobile phase, pH was adjusted to 3 ± 0.1 with o-phosphoric acid. The flow rate was 1.2 mL min^?1. The linearity range was 0.2 to 2 µg mL^?1 for amlodipine besilate and 0.4 to 4 µg mL^?1 for Valsartan with a mean percentage recovery of 99.59 ± 0.523% and 100.61 ± 0.400% for amlodipine besilate and valsartan, respectively. The TLC method used silica gel 60 F₂₅₄ plates; the optimized mobile phase was ethyl acetate/ methanol / ammonium hydroxide (55:45:5 by volume). Quantitatively, the spots were scanned densitometrically at 237 nm. The range was 0.5–4.0 µg spot^?1 for amlodipine besilate and 2.0–12.0 µg spot^?1 for valsartan. The mean percentages recovery was 99.80 ± 0.451% and 100.61 ± 0.363% for amlodipine besilate and valsartan, respectively. The HPLC method was found to be simple, selective, precise, and reproducible for the estimation of both drugs from spiked human plasma.     

Development and Validation of a Stability-Indicating HPLC Method for Determination of Ciprofloxacin Hydrochloride and its Related Compounds in Film-Coated Tablets

The objective of the current study was the development and subsequent validation of a simple, sensitive, precise and stability-indicating reversed-phase HPLC method for the determination of ciprofloxacin HCl in pharmaceutical dosage forms in the presence of its potential impurities. The chromatographic separation of ciprofloxacin HCl and its related compounds was achieved on an Inertsil ODS3 column using UV detection. The optimized mobile phase consisted of phosphoric acid solution: acetonitril. The proposed method provided linear responses within the concentration range 250–750 μg mL⁻¹ for ciprofloxacin HCl and 0.5–1.5 μg mL⁻¹ for its related compounds. LOD and LOQ values for the active substance were 5.159 and 15.632 μg mL⁻¹, respectively. Correlation coefficients (r) of the regression equations for the impurities were greater than 0.99 in all cases. The precision of the method was demonstrated using intra- and inter-day assay RSD% values which were less than 1% in all instances. No interference from any components of pharmaceutical dosage forms or degradation products was observed.

     

Determination of Nateglinide in Human Plasma by LC-ESI-MS and Its Application to Bioequivalence Study

To evaluate the bioequivalence of nateglinide, a rapid and specific liquid chromatographic-electrospray ionization mass spectrometric method was developed and validated to determine nateglinide for human plasma samples. The analyte was detected using electrospray positive ionization mass spectrometry in the selected ion monitoring mode. Tinidazole was used as the internal standard. A good linear relationship obtained in the concentration ranged from 0.05 to 16 μg mL^?1 (r ² = 0.9993). Lower limit of quantification was 0.05 μg mL^?1 using 100 μL of plasma sample. Intra- and inter-day relative standard deviations were 2.1–7.5 and 4.7–8.9%, respectively. Among the pharmacokinetic data obtained, T _max was 2.09 ± 1.06 h for reference formulation and 2.40 ± 0.97 h for test formulation. C _max was 4.17 ± 1.31 μg mL^?1 for reference formulation and 4.37 ± 1.53 μg mL^?1 for test formulation. The half-life (t _½) was 1.93 ± 0.44 h for reference formulation and 1.92 ± 0.29 h for test formulation. AUC_0–10h was 13.67 ± 4.36 μg h mL^?1 for reference formulation and 13.21 ± 4.09 μg h mL^?1 for test formulation. This method was successfully applied to the pharmacokinetic study in human plasma samples.     

Determination of Three Nonsteroidal Anti-Inflammatory Drugs in Human Plasma by LC Coupled with Chemiluminescence Detection

A simple and sensitive method was developed for the determination of three nonsteroidal anti-inflammatory drugs (NSAIDs)—ibuprofen, naproxen and fenbufen in human plasma. The method involved in column liquid chromatographic separation and chemilumenescence (CL) detection based on the CL reaction of NSAIDs, potassium permanganate (KMnO₄) and sodium sulfite (Na₂SO₃) in sulfuric acid (H₂SO₄) medium. The chromatographic separation was carried out using a reversed-phase C₁₈ column, which allowed the selective determination of the three medicines in the complicated samples. The special features of the CL detector provided lower LOD for determination than that of existing chromatographic alternatives. The results indicated that the linear ranges were 0.01–10.0 μg mL⁻¹ for ibuprofen, 0.001–1.0 μg mL⁻¹ for naproxen, and 0.01–10.0 μg mL⁻¹ for fenbufen. The limits of detection were 0.5 ng mL⁻¹ for ibuprofen, 0.05 ng mL⁻¹ for naproxen and 0.5 ng mL⁻¹ for fenbufen (S/N = 3). All average recoveries were in the range of 90.0–102.3%. Finally, the method had been satisfactorily applied for the determination of ibuprofen, naproxen and fenbufen in human plasma samples.

     

Determination of Tectorigenin in Rat Plasma: Application to a Pharmacokinetic Study After Oral Administration of Tectorigenin or Its Prodrug Tectoridin

A simple, sensitive, and validated liquid chromatographic method has been developed for the determination of tectorigenin in rat plasma and application to a pharmacokinetic study after oral administration of tectorigenin or its prodrug tectoridin. The analysis was performed on a Kromasil C₁₈ analytical column using gradient elution with acetonitrile 0.1% phosphonic acid water at 0.8 mL min⁻¹. The detection wavelength for UV detection was set at 264 nm. The established method was fully validated with parameters as follows: the intra- and inter-day assay precisions (CV) of three analytes were in the range of 4.2–13.3% and accuracies were between 98.0 and 107.5%; the calibration curve was linear with r ² > 0.99 over a concentration range of 0.02–2 μg mL⁻¹; the lower limit of quantification was 0.02 μg mL⁻¹; tectorigenin showed stable in rat plasma after 12 h incubation at room temperature, 15 days storage at −80 °C and three freeze/thaw cycles, as well as in reconstitute buffer for 24 h at 25 °C; and the mean recoveries of tectorigenin were 92.3 ± 3.2, 95.5 ± 2.9 and 94.5 ± 3.0% with quality control levels of 0.02, 0.2 and 2 μg mL⁻¹, respectively. In conclusion, this method is simple, economic, and sensitive enough for in vivo pharmacokinetic studies of tectorigenin.

     

LC-ESI-MS-MS Determination of Rat Plasma Protein Binding of Major Flavonoids of Flos Lonicerae Japonicae by Centrifugal Ultrafiltration

A simple, precise, accurate, selective, and sensitive reversed-phase LC–UV method has been developed for simultaneous analysis of diltiazem and non-steroidal anti-inflammatory drugs (NSAIDs) in the bulk drug, tablet dosage forms, and human serum. Chromatographic separation of the drugs was performed at ambient temperature on a C₁₈ stationary phase with 80:20 (v/v) methanol–water, pH 3.1 ± 0.02, as isocratic mobile phase. The mobile phase flow rate was initially 0.5 mL min^?1 then increased to 1 mL min^?1. All the NSAIDs were well separated from each other and from diltiazem. Total run time was 10 min. The assay was successfully applied to pharmaceutical formulations and serum and there was no chromatographic interference from tablet excipients. The method was linear in the range 1.25–50 μg mL^?1 both for diltiazem and the NSAIDs. The suitability of this HPLC method for quantitative analysis of the drugs was proved by validation in accordance with International Conference on Harmonization (ICH) guidelines. The validation results, and results from statistical analysis of the data, demonstrated the method was reliable.     

Application of Multicriteria Methodology in the Development of Improved RP-LC-DAD for Determination of Rizatriptan and Its Degradation Products

A simple, rapid, and stability-indicating reversed-phase high-performance liquid chromatographic (LC) method for analysis for dutasteride has been successfully developed. Chromatography was performed on a 150 mm × 4.6 mm C₁₈ column with acetonitrile–water 60:40 (v/v) as isocratic mobile phase at 1.0 mL min⁻¹. Ultraviolet detection of dutasteride was at 210 nm. Its retention time was approximately 10 min and its peak was symmetrical. Response was a linear function of concentration over the range 0.2–1 μg mL⁻¹ (R ² = 0.997) and the limits of detection and quantitation were was 0.05 and 0.10 μg mL⁻¹, respectively. The method was validated for linearity, precision, repeatability, sensitivity, and selectivity. Selectivity was validated by subjecting dutasteride stock solution to photolytic, acidic, basic, oxidative, and thermal degradation. The peaks from the degradation products did not interfere with that from dutasteride. The method was used to quantify dutasteride in pharmaceutical preparations.

     

Nonextractive Trace Level Simultaneous Determination of Mercury(II) and Zinc(II) in Environmental Samples with 2‐(5‐Bromo‐2‐pyridylazo)‐5‐diethylaminophenol and Cetylpyridinium Chloride

Abstract

A simple, rapid, selective, and sensitive method for the derivative spectrophotometric determination of Hg(II) and its simultaneous determination in the presence of Zn(II) using 2‐(5‐bromo‐2‐pyridylazo)‐5‐diethylaminophenol in the presence of cetylpyridinium chloride, a cationic surfactant, has been developed. The molar absorption coefficient and analytical sensitivity of the 1∶1 Hg(II) complex at 558 nm (λ_max) are 5.78×10⁴ L mol^?1 cm^?1 and 0.67 ng mL^?1, respectively. The detection limit of Hg(II) is 1.40×10^?2 ng mL^?1, and Beer's law is valid in the concentration range 0.05–2.40 µg mL^?1. Overlapping spectral profiles of Hg(II) and Zn(II) complexes in zero‐order mode interfere in their simultaneous determination. However, 0.10–2.00 µg mL^?1 of Hg(II) and 0.065–0.650 µg mL^?1 of Zn(II), when present together, can be simultaneously determined at zero cross point of the derivative spectrum, without any prior separation. The relative standard deviation for six replicate measurements of solutions containing 0.134 µg mL^?1 of Hg(II) and 0.620 µg mL^?1 of Zn(II) is 1.72 and 1.47%, respectively. The proposed method has successfully been evaluated for trace level simultaneous determination of Hg(II) and Zn(II) in environmental samples.