The Liquid Chromatographic Determination of Chlorogenic and Caffeic Acids in Xu Duan (Dipsacus asperoides) Raw Herb

A validated analytical method is reported for the analysis of chlorogenic and caffeic acids in Xu Duan (Dipsacus asperoides) in the dried raw herb. The ground samples were extracted by ultrasonication in water and the extract was analysed by LC-PDA with identity confirmation by (+)ESI-MS/MS. A C18 column was used with a 0.1% aqueous formic acid : methanol gradient mobile phase. The analytes were quantified 325 nm. With the MS detector, using the chlorogenic acid precursor ion with m/z 354, ions with m/z 191, and 85 were produced. For caffeic acid the precursor ion with m/z 181, ions with m/z 163, 135, and 89 were produced. The amount of chlorogenic and caffeic acids in the raw herb was found to be 4.46 and 0.63 mg/g, respectively, and the method LOD was 0.13 and 0.02 mg/g, respectively.

Redox-Reaction Based Spectrophotometric Assay of Isoniazid in Pharmaceuticals

Two spectrophotometric methods are described for the determination of isoniazid (INH) in pharmaceuticals. In the first method (FCR method), INH is reacted with Folin-Ciocalteu reagent in Na2CO3 medium and the resulting blue colored chromogen measured at 760 nm. Iron(II), formed as a result of reaction between INH and iron(III), is made to react with ferricyanide, and the resulting Prussian blue is measured at 760 nm, basing the second method (FFC method). The conditions for better performance are optimized. Beer’s law is obeyed in the concentration ranges 0.5–10 and 0.2–3.0 μg mL−1 for FCR method and FFC methods, respectively, with corresponding molar absorptivity values of 1.12×104 and 4.55×104 L mol−1 cm−1. The methods are validated for accuracy, precision, LOD, LOQ, robustness, and ruggedness as per the current ICH guidelines. The validated methods were successfully applied to quantify INH in its commercial formulation with satisfactory results; hence the methods are suitable for isoniazid determination in bulk drugs and pharmaceuticals.

Determination of Phenol and Chlorophenols at Single-Wall Carbon Nanotubes/Poly(3,4-ethylenedioxythiophene) Modified Glassy Carbon Electrode Using Flow Injection Amperometry

Phenol and chlorophenols were investigated using single-wall carbon nanotubes (SWCNT) and poly(3,4-ethylenedioxythiophene) (PEDOT) composite modified glassy carbon electrode (SWCNT/PEDOT/GCE) as a detector in flow injection system. Optimization of experimental variables such as the detection potential, flow rate, and pH of the carrier solution (0.1 M sodium acetate) for the determination of phenol (P), 4-chlorophenol (CP), 2,4-dichlorophenol (DCP), 2,4,6-trichlorophenol (TCP), and pentachlorophenol (PCP) were performed. Under these conditions, analytical parameters were calculated from the calibration curve of measured amperometric responses as a function of concentrations of phenol and chlorophenols. The designed electrode exhibited very good analytical performance. The designed electrode was tested with 20 repetitive injections of each analyte and showed good operational stability. The analytical performance of the SWCNT/PEDOT/GCE electrode under flow through conditions was tested and was found to be impressive. The electrode showed a wider dynamic range for the detection of phenol and chlorophenols with low limits of detection compared with other enzymatic and nonenzymatic sensors. These results suggest that the method is quite useful for the analysis and monitoring of phenols and chlorophenols.

Analytical Method Development and Validation of Solifenacin in Pharmaceutical Dosage Forms by RP-HPLC

A new, accurate, precise, and robust HPLC method was developed and validated for the determination of solifenacin in tablet dosage form. The chromatographic separation was achieved on an Inertsil ODS 3V C18 (150 mm × 4.6 mm, 5 μm) stationary phase maintained at ambient temperature with a mobile phase combination of monobasic potassium phosphate (pH 3.5) containing 0.1% triethylamine and methanol (gradient mode) at a flow rate of 1.5 mL/min, and the detection was carried out by using UV detector at 220 nm. The performance of the method was validated according to the present ICH guidelines.

Isocratic High-Performance Liquid Chromatographic Assay of Olanzapine: Method Development and Validation

An accurate, precise, sensitive, and rapid isocratic reversed phase high-performance liquid chromatographic (RP-HPLC) method for the analysis of olanzapine (OLP) in bulk drug and in tablets has been developed and validated. Analysis was performed on a 150 mm × 4.6 mm, 5 μm particle Intersil ODS 3V column with 10 mM disodium hydrogen phosphate buffer (pH 7.4)-acetonitrile (35 : 65) (v/v) as mobile phase at a flow rate of 1.0 mL min−1 with UV detection at 254 nm; the constant column temperature was 40°C. The runtime under these chromatographic conditions was less than 8 min. The calibration plot was linear over the concentration range of 2.5–20.0 μg mL−1 with limits of detection and quantification values of 50 and 200 ng mL−1, respectively. The precision and accuracy of the method were assessed by determination of validation data for precision (intraday RSD values of 0.11–0.28%, interday RSD values of 0.15–0.46%), accuracy (0.87–2.80% intraday, 0.33–1.80% interday), and specificity, in accordance with the ICH guidelines. The stability of standard solution and tablet extract was also studied over a period of 24 h. The method was applied for the determination of OLP in tablets with satisfactory results.

Electrooxidation of Indomethacin at Multiwalled Carbon Nanotubes-Modified GCE and Its Determination in Pharmaceutical Dosage Form and Human Biological Fluids

A simple, rapid, selective, and sensitive electrochemical method for the direct determination of indomethacin was developed. The electrochemical behavior of indomethacin was carried at multiwalled carbon nanotube- (MWCNTs-) modified glassy carbon electrode (GCE). The cyclic voltammetric results indicated that MWCNT-modified glassy carbon electrode remarkably enhanced electrocatalytic activity towards the oxidation of indomethacin in slightly acidic solutions. It led to a considerable improvement of the anodic peak current for indomethacin and could effectively accumulate at this electrode and produce two anodic peaks at 0.720 V and 0.991 V, respectively, and one reduction peak at 0.183 V. The electrocatalytic behavior was further exploited as a sensitive detection scheme for the determination of indomethacin by differential-pulse voltammetry (DPV). Under optimized conditions, the concentration range and detection limit were 0.2 to 6.0 μM and 13.2 nM, respectively. The proposed method was successfully applied to determination of Indomethacine in pharmaceutical samples. The analytical performance of this sensor has been evaluated for detection of analyte in human serum and urine as real samples.

Development and Validation of High Performance Liquid Chromatography Method for Simultaneous Estimation of Flavonoid Glycosides in Withania somnifera Aerial Parts

Withania somnifera (L.) Dunal (Solanaceae) commonly known as ashwagandha, is an important plant in Ayurveda and is believed to increase longevity and vitality. The root is considered to be the medicinally important part of the plant as per classical texts and accordingly is the subject of most Pharmacopeial monographs. The aerial parts, being less expensive, are sometimes mixed with roots to prepare “standardized” extracts of W. somnifera, and in cases with false declaration of plant part used as roots on the certificate of analysis. The present study described a new, simple, accurate, and precise HPLC method for the simultaneous determination of flavonoid glycosides as unique constituents of the aerial parts, being absent in roots of the plant. The RSD for intra- and interday analyses was less than 2.5% and the recovery was 90–108%. The method was used to analyze samples of roots and aerial parts of the plant collected from India and Egypt. The samples of commercially available extracts of W. somnifera were also analyzed and many samples were found to contain flavonoid glycosides indicating a possible undeclared use of aerial parts in the extracts derived from roots in commercial practice.

Simultaneous Estimation of Ambroxol Hydrochloride and Cetirizine Hydrochloride in Pharmaceutical Tablet Dosage Form by Simultaneous Equation Spectrophotometric Method: A Quality Control Tool for Dissolution Studies

Ambroxol Hydrochloride and Cetirizine Hydrochloride are used for the treatment of bronchitis, cough, and allergy. A simple, economical, accurate, and precise method for simultaneous estimation of Ambroxol Hydrochloride and Cetirizine Hydrochloride in tablet dosage form has been developed. Simultaneous equation method based on measurement of absorbance at two wavelengths, that is, 244 nm and 230 nm, λmax of Ambroxol Hydrochloride and Cetirizine Hydrochloride in pH 6.8 phosphate buffer. Both of these drugs obeyed Beer-Lambert’s law in the concentration range of 2–18 µg/mL for Ambroxol Hydrochloride and 2–20 µg/mL for Cetirizine Hydrochloride. The high values of correlation coefficient (R) indicated good linearity of calibration curve for both the drugs. The accuracy and precision of method were determined and the method was validated statistically. Result of percentage recovery study confirms the accuracy of proposed method. As per the ICH guidelines, the method validation parameters checked were linearity, accuracy, precision, and assay of drug formulation. Based on the results obtained, it can be concluded that the proposed simultaneous equation spectrophotometric method for simultaneous estimation of Ambroxol Hydrochloride and Cetirizine Hydrochloride is rapid, economical, accurate, precise, and reproducible. Hence, the proposed method can be employed for quantitative estimation of Ambroxol Hydrochloride and Cetirizine Hydrochloride from their tablet dosage form.

Characterization of Cr-Curcumin Complex by Differential Pulse Voltammetry and UV-Vis Spectrophotometry

Differential Pulse Voltammetry (DPV) and UV-Vis techniques were used in characterizing the complexation of chromium with curcumin. It was observed that chromium complexed with curcumin in a 1 : 3 ratio. The experimental values that were used to calculate this ratio were independently determined by the two techniques used. The values obtained from each technique agree with each other reasonably well, within limits of experimental error. The stability constant or formation constant, Kf, of the complex, 1.58×1010, was determined using the Lingane equation and Gibb’s free energy of formation was calculated as −58.18 kJ.

Removal of Hardness of Earth Alkaline Metals from Aqueous Solutions by Ion Exchange Method

An ion exchange process was introduced as an approach for softening of artificial hard water solutions. A strong acid cation exchange resin, Amberlite IR 120 [Na+], was used to reduce the hardness of water with the matrix of styrene-divinylbenzene copolymer having functional group as sulfonate. The ion exchange behavior of the ions of calcium and magnesium in synthetic solutions of hard water was investigated with the variables depending on pH, stirrer speed of the solutions and amount of the resin as a function of contact time between resin phase and hard water solution. The maximum ion exchange capacity was found to be 68 mg/g for Ca(II) and 12 mg/g for Mg(II) at pH 3.0. The method is a simple and efficient one to remove calcium and magnesium hardness from hard water solutions with the resin having more selectivity for calcium.