Implementation of design of experiments for optimization of forced degradation conditions and development of a stability-indicating high-performance liquid chromatography method for sepiwhite

Sepiwhite is a novel anti-pigmenting agent that is derived from fatty acid and phenylalanine and used for hyperpigmentation induced by light exposure or inflammation. In this study, a simple and validated high-performance liquid chromatography method for the quantitation of sepiwhite was developed. Optimized forced degradation of sepiwhite at thermal, acid/base, photolysis, oxidative, and heavy metal ions conditions were evaluated and the effect of each of them on production of specific 10%-30% degradants was studied by the approach of design of experiments. Sepiwhite accelerated study was conducted and toxicity of sepiwhite at each condition was tested. An optimized high-performance liquid chromatography method was validated by a face-centered central composition design. Ten different degradants were identified from sepiwhite and degradation behavior under different conditions was studied. Sepiwhite and its degradant products show no cytotoxicity. This optimized high-performance liquid chromatography method can be applied for quality control assay and sepiwhite degradation behavior may be considered in the manufacturing of sepiwhite products.

Application of supercritical fluid chromatography for separation and quantitation of 15 co-formulated binary anti-hypertensive medications using a single elution protocol

A facile supercritical fluid chromatography method is proposed to analyse 15 co-formulated binary anti-hypertensive drug combinations using a customized elution procedure. The effect of mobile phase composition, column back pressure and temperature was suitably optimized for adequate retention, analyte response and resolution. The chromatographic separation of the different drug combinations was performed on a DCPak poly(4-vinylpyridine) column (250 × 4.6 mm, 5 μm) at 125-bar pressure and 40°C using a photodiode array detector. A linear gradient of CO₂ and 0.1% formic acid in methanol provided the best elution conditions for all drug combinations. Baseline separation of the drugs was possible with resolution factor R_s ranging from 1.42 to 12.58. The method was validated for specificity, sensitivity, accuracy and precision, recovery and robustness. The limit of detection and limit of quantitation for aliskiren, amlodipine, atenolol, candesartan, hydrochlorothiazide, lisinopril, losartan, metoprolol, olmesartan, telmisartan and valsartan were in the range of 0.26-2.56 and 0.77-7.75 μg/mL, respectively. The thermodynamic study revealed that interactions of the drugs with the stationary phase were spontaneous as evident from the negative free energy values, and the separation process was enthalpy driven. The developed method was successfully employed to analyse these drugs in their co-formulated tablet formulations.

Determination of Hydrochlorothiazide and Two Major Degradation Products by Stability Indicating High Performance Liquid Chromatography

Background:

Hydrochlorothiazide (HCTZ) is a thiazide diuretic which comprises two sulfonamide groups. The literature is not clear regarding the identification of the chromatographic peaks of its two major related substances: chlorothiazide and 4-amino-6-chloro-1,3-benzenedisulfonamide (DSA).

Methods:

In the present study, a simple, sensitive, and selective HPLC method was developed and validated for the assay of HCTZ, Chlorothiazide and DSA. The method was carried out on a C18 column, maintained at 40ºC. The mobile phase was composed of monobasic potassium phosphate buffer 0.02M pH 3.0/acetonitrile/methanol (82:9:9, v/v/v), run at a flow rate of 1.0 mL/min, and UV detection at 270 nm.

Results:

All related compounds including processing impurities and degradants from stressed samples were well separated from each other. The performance of this method was validated in accordance to the ICH guidelines and included specificity, linearity, limit of detection, limit of quantification, accuracy, precision and robustness.

Conclusion:

Based on the results, the HCTZ degradation pathway was proposed and the validated HPLC method was successfully applied to the quantitative analysis of HCTZ in pharmaceutical formulations, contributing to improve quality control, to assure therapeutic efficacy and to clarify the literature.