In the last few years, the use of surfactants as mobile phase additives in reversed phase liquid chromatography (RPLC) has been steadily developing and improving. Surfactants modify the polarity of the stationary phase which in turn decreases the amount of organic solvent required for elution of the analytes rendering the methodologies linked to them greener and more eco-friendly. Brij-35 is a fatty alcohol ethoxylates non ionic surfactant, which is less widely used as mobile phase additive. Brij-35 can decrease stationary phase polarity while remaining neutral. In this research, Brij-35 was studied in the separation and determination of marketed antihypertensive combination therapy composed of triamterene (TRM) and xipamide (XIP). TRM and XIP are diuretics used for treatment of essential hypertension and associated edema conditions. Chromatographic separation was achieved on RP-C18 column (Kinetix®, 5 mm, 15 cm 3 4.6 mm) at flow rate 1 mL min1 and UV-detection at 254 nm. Isocratic elution was performed using mobile phase composed of 0.1 M Brij-35: methanol (MeOH) (60:40, v/v). The analytes were well separated and quantified within linearity ranges of 5–50 mg mL1 for both drugs in short retention time (2.6 and 5.3 min. for TRM and XIP, respectively). Since claiming greenness is not enough, Green Analytical Procedure Index (GAPI) was used to demonstrate the superiority of the proposed method over the previously reported methods. GAPI is a new metric for evaluation of the ecological impact of analytical procedures. The proposed method was validated according to ICH guidelines and applied successfully for simultaneous determination of the drugs in their co-formulated tablets.
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A simple stability-indicating high-performance liquid chromatography-diode array detection (HPLC-DAD) method has been developed for the simultaneous determination of triamterene (TRI) and xipamide (XIP) in presence of the degradation products generated in studies of forced decomposition. Drugs were subjected to stress by hydrolysis (acidic, alkaline, and neutral), oxidation, photolysis (254 and 365 nm), and dry and wet heat treatments. Degradation occurs under acidic and alkaline conditions (TRI only), oxidative stress (TRI and XIP), and by photolysis (XIP only), but both drugs were stable under other stress conditions investigated. Separation of the two drugs from all the degradant peaks was achieved within 11 min using C8 column (250 × 4.6 mm, 5 μm) and mobile phase consisting of acetonitrile and 0.05 M phosphate buffer adjusted to pH 4 delivered at a flow rate of 1 mL min -1 using gradient elution system. The drugs were quantified at 220 nm using photodiode array detector, based on peak area. Peak homogeneity of the two drugs was checked using diode array detector, and the purity angle was within the purity threshold limit in all of the stressed samples. The calibration graphs for each drug were rectilinear in the range of 0.2–50 and 0.1–20 μg Ml -1 for TRI and XIP, respectively. The method was validated in compliance with International Conference on Harmonization (ICH) guidelines; in terms of linearity, accuracy, precision, robustness, limit of detection, and limit of quantitation. The proposed method was successfully applied for the determination of the investigated drugs in their tablet without interference from excipients with acceptable accuracy and precision; the label claim percentages were 100.23 ± 0.70% and 100.75 ± 1.11% for TRI and XIP, respectively.
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