J. Planar Chromatogr. 21, 289-294 (2008). HPTLC of quetiapine on silica gel with hexane - dioxane - propylamine 5:45:2 and on RP-8 with tetrahydrofuran - phosphate buffer (pH 9.0) 1:1 in horizontal chambers. Quantitative determination by absorbance measurement at 243 nm and by videodensitometry at 254 nm. The precision and accuracy of the four methods were fully comparable and no significant differences were observed.

Anal. Chim. Acta 641 (1-2), 52-58 (2009). Comparison of classical filtering techniques (Savitzky–Golay, Adaptive Degree Polynomial Filter, Fourier denoising, Butterworth and Chebyshev IIR filters) and wavelet shrinkage (31 mother wavelets, 3 thresholding techniques and 11 decomposition levels) with the original noisy signal and a reference signal which was denoised experimentally by averaging 64 measurements. The best similarity to the reference signal was obtained with filters, however the signal was slightly oversmoothed. The wavelet shrinkage method gave less denoised signals. There was a significant influence of the thresholding technique and decomposition level, and best conditions were at level 2 or 3 and soft thresholding), whereas changing of the mother wavelet almost did not change the result. The presented results can be used as general recommendations for denoising densitometric fingerprints before applying further chemometric algorithms. The best choices were: Savitzky–Golay filter of appropriate window width (optimized against autocorrelation) or wavelet shrinkage with Haar wavelet, soft thresholding and high decomposition level.

Asian J. of Chem. 21(9), 6999-7004 (2009). HPTLC of ursolic acid in methanolic and aqueous extracts of Ocimum sanctum (Tulsi) on silica gel with toluene - ethyl acetate - acetic acid 55:45:2 with chamber saturation. Detection by treatment with Liebermann Burchard’s reagent. Quantitative determination by absorbance measurement at 550 nm. The method was linear in the range of 100-400 ng/band. The amount of ursolic acid in aqueous and methanolic extracts was in the range of 0.2 and 0.4 %. Samples collected from different geographical regions were compared, samples from Kerala contained the highest levels of ursolic acid.

J. AOAC Int. 92, 691-697 (2009). HPTLC of dialkyl phosphate standards (dimethyl phosphate, diethyl phosphate, dimethyl thiophosphate, diethyl thiophosphate and dibutyl phosphate as internal standard) on amino phase, prewashed with methanol, with dichloromethane in a twin trough chamber. Quantitative determination by fluorescence measurement at 366/>400 nm. The limit of quantification was between 0.8 and 1.4 ng/zone. Fluorescence enhancement was achieved by dipping the plate into a 50 % solution of paraffin oil in n-hexane, increasing the sensitivity and resulting in an LOQ of 0.5-0.6 ng/zone.

Ind. J. Pharma. Sci. 8(4), 198-201(2009). HPTLC of nebivolol hydrochloride and valsartan on silica gel with ethyl acetate - methanol - acetic acid 12:2:1 in a twin trough chamber saturated for 15 min. Quantitative determination by absorbance measurement at 240 nm for valsartan and 280 nm for nebivolol hydrochloride. The method was found to be linear in the range of 600-1400 ng/band for valsartan 1200-2800 ng/band for nebivolol. The sample were subjected to different stress conditions (acid, alkali, oxidation, photolysis, thermal) and all degradation products were well separated from the main compounds.

Abstract No. F-243, 61st IPC (2009). HPTLC of isotretinoin and erythromycin on silica gel with toluene - dimethyl sulfoxide - methanol 65:2:25. Quantitative determination by absorbance measurement at 340 nm before derivatization for isotretinoin and at 410 nm for erythromycin after derivatization with 10 % sulfuric acid followed by heating at 100 °C for 15 min. The hRf value was 38 and 55 for isotretinoin and erythromycin, respectively. The linearity was in the range of 30-150 ng/band for isotretinoin and 1200-6000ng/band for erythromycin. Recovery was between 96.9 and 99.7 for isotretinoin and between 97.2 and 102.6 % for erythromycin. Intra-day and inter-day relative standard deviations for both components were <2.0 %.

Abstract No. F-269, 61st IPC (2009). HPTLC of hydrochlorothiazide and irbesartan on silica gel with acetonitrile - chloroform 5:6. The hRf value was 27 and 45 for irbesartan and hydrochlorothiazide, respectively. Quantitative determination by absorbance measurement at 270 nm. The sample was exposed to different stress conditions (acid, alkali, oxidative, photodegradation, thermal). Neither of the compounds showed degradation under thermal and photodegradation conditions, but both compounds showed significant degradation under acid, alkali and hydrolytic conditions. Degraded products were well resolved from the parent compounds.

J. Planar Chromatogr. 22, 439-443 (2009). HPTLC of jatrorrhizine in methanolic extracts of the stem of the ’heavenly elixir’ on silica gel with ethyl acetate - isopropanol - 10 % ammonia 3:5:3 in a twin trough chamber saturated for 5 min. Detection under UV 254 nm and after derivatization with Dragendorff’s reagent. Quantitative determination by absorbance measurement at 344 nm.