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Summary Ethyl 8-oxo-5,6,7,8-tetrahydrothiazolo[3,2-a][1,3]diazepin-3-carboxylate (HIE-124) is one of a new generation of ultra-short-acting hypnotics. A high-performance thin-layer chromatographic (HPTLC) method has been established as the first reported method for quantitative analysis of HIE-124 in plasma. Baseline resolution between HIE-124 and diazepam (internal standard) was achieved on HPTLC plates with chloroform–ethyl acetate 80:20 (v/v) as mobile phase. Densitometric detection was performed at 265 nm. The method was linear in the range 40–400 μg mL–1 (R = 0.997) and recoveries of the drug were in the range 93–102% at 80– 350 μg mL –1 . Within-run and between-run precision calculated as RSD [%], and accuracy calculated as percentage error were in the ranges 2.1–4.6% and 0.8–6.9%, respectively. The limits of detection (LOD) and quantification (LOQ) in spiked human plasma were 20 and 40 μg mL–1 (40 and 80 ng per band), respectively.

A high-performance thin-layer chromatographic (HPTLC) method has been established for determination of sildenafil citrate in commercial products. The compounds were separated on silica gel, with CHCl 3 -MeOH-diethylamine, 90 + 10 + 1 ( v/v ), as mobile phase, and the analyte spots were quantified densitometrically at λ = 305 nm. Recovery of sildenafil citrate was 100.6 and 98.2%, for pure and spiked samples, respectively. Method precision and specificity were also validated. The method was used for determination of sildenafil in four pharmaceutical products and three aphrodisiac herbal preparations which were claimed to be totally natural. Levels of sildenafil in the pharmaceutical products ranged from 49.7 to 50.5 mg per tablet. Sildenafil was also detected in one herbal preparation at a concentration of 85.0 mg per capsule.

A high-performance thin-layer chromatographic method for determination of parthenolide has been validated for recovery, accuracy, specificity, and precision and applied to four feverfew products. Chromatography was performed on silica gel plates with ethyl acetate- n -hexane, 3 + 2 ( v/v ) as mobile phase. Parthenolide was visualized by dipping plates into p -anisaldehyde reagent and heating at 105°C for 5 min. Densitometric quantification of analyte spots was achieved by scanning the plates at λ = 543 nm after derivatization. The method is precise with CV [%] < 5.00; calibration recovery = 101.12 ± 4.11% and overall accuracy = 101.14 ± 4.47%. The levels of parthenolide in the products analyzed ranged from 0.03 to 0.24%.