Development and validation of a reversed-phase high-performance liquid chromatographic method for the quantitation and stability of α-lipoic acid in cosmetic creams

Stress degradation studies and development of validated stability indicating densitometric method for estimation of alpha lipoic acid in bulk and capsule dosage form

A precise, sensitive, specific and accurate stability indicating densitometric method was developed and validated for alpha-lipoic acid (ALA) in bulk and capsule dosage form. The study employed pre-coated silica gel 60F254 TLC plates as stationary phase and toluene: chloroform: methanol: formic acid (5:3:1:0.05; v/v/v/v) as mobile phase. The developed method furnished compact spots of alpha-lipoic acid (Rf 0.28 ± 0.05) after derivatization, offered good linearity in range 80–400 ng/spot with correlation coefficient of 0.998. The values for detection and quantitation were found 18.022 and 54.612 ng/spot respectively. ALA was subjected to stress degradation studies and total 13 degradation products were resolved. Thus, the proposed method offered good results according to ICH guidelines, and can be used for identification, routine quantitative determination as well as for monitoring the stability of ALA in bulk and in capsules.

Bioanalytical methods for the detection of duloxetine and thioctic acid in plasma using ultra performance liquid chromatography with tandem mass spectrometry (UPLC-MS/MS)

Duloxetine and thioctic acid (TA) are standard drugs for treating diabetic neuropathy, a primary complication associated with diabetes. In this study, ultra performance liquid chromatography coupled with tandem mass spectrometry methods was successfully developed and validated for quantifying duloxetine and TA in biological samples. The protein precipitation method was used to extract duloxetine, TA and their internal standards from beagle dog plasma. A Hypersil Gold C18 column (150 × 2.1 mm, 1.9 μm) was used for the experiment. Isocratic elution with 0.1% formic acid in acetonitrile (A) and 0.1% formic acid (B) was used for duloxetine, whereas a gradient elution with 0.03% acetic acid (A) and acetonitrile (B) was used for TA. The validated parameters included linearity, sensitivity, accuracy, precision, selectivity, matrix effect, stability, and recovery under different conditions. The linear ranges of the calibration curves for duloxetine and TA were 5–800 ng/mL and 5–1,000 ng/mL, respectively. An intra- and inter-run precision of ± 15% can be observed in all quality control samples. These methods were successfully used for pharmacokinetics (PKs) studies in beagle dogs to compare PK differences in a fixed-dose combination including duloxetine and TA and co-administration of the 2 drugs.