62nd Indian Pharmaceutical Congress Abstract No. F-343 (2010). TLC of hydrochlorothiazide (HCTZ) and irbesartan (IRBE) on silica gel with toluene – acetic acid – methanol 70:2:50. Quantitative determination by absorbance measurement at 264 nm. The hRf values were 15 for HCTZ and 45 for IRBE. The linearity was in the range of 90-540 ng/band and 180-900 ng/band with r2= 0.9989 for HCTZ and IRBE. The recovery of HCTZ was 95.3-97.7 % and of IRBE 95.2-98.7 %.

J. of Chromatogr. Sci. 49, 129-135 (2011). TLC on silica gel with ethyl acetate – chloroform – formic acid – triethyl amine 70:30:1:1. Detection and quantification by densitometry. Good correlation between the integrated peak area of the studied drugs and their corresponding concentrations was found in different ranges.

J. Sep. Sci. 34, 286-291 (2011). HPTLC of 1beta,3alpha,8beta-trihydroxy-pimara-15-ene (1), 6alpha,11,12,16-tertahydroxy-7-oxo-abieta-8,11,13-triene (2) and 2alpha,19-dihydroxy-primara-7,15-diene (3) in the root bark of Premna integrifolia on silica gel with hexane – acetone – ethyl acetate 3:1:1. Detection by dipping into vanillin-sulfuric acid reagent (2 g vanillin in 190 mL ethanol with 10 mL sulfuric acid) followed by air drying and heating for 3 min at 110 °C. Quantitative determination by absorbance measurement at 475 nm. The hRf values of (1), (2) and (3) were 58, 44, and 32, respectively and selectivity regarding matrix was given. Linearity was between 1-10 µg/spot for (1), (2) and (3), respectively. The limits of detection were found to be 230, 106 and 336 ng/band for compounds (1), (2) and (3), respectively, whereas the limits of quantification were 769, 354 and 1122 ng/band, respectively. Inter- and intraday precisions were 0.9-1.3 % and 1.1-1.2 %, respectively. The average recoveries for compounds (1) to (3) were found to be 100.6, 103.9 and 97.6 %, respectively, within the acceptable %RSD.

J. Liq. Chromatogr. Relat. Technol. 34, 902-919 (2011). HPTLC of seven sugars (D-glucose, D-galactose, D-mannose, beta-D-fructose, alpha-D-fructose, sucrose, maltose, lactose) in food samples on silica gel with n-butanol - isopropanol - acetic acid - boric acid solution (200 mg boric acid in 10 mL water) 6:14:1:3. Detection by dipping into either aniline diphenylamine o-phosphoric acid reagent or p-aminobenzoic acid reagent. Quantitative determination by absorbance measurement at 370 nm. The HPTLC method was more sensitive by a factor of 8 for detection of sugars when compared to HPLC; only fructose showed a slightly better LOQ (difference by factor of 3). LOQ was better than 63 ng for HPTLC and about 500 ng for HPLC. Method comparison showed a good correlation and only a mean difference between both methods of 1.5 % sugar content for many food samples analyzed. HPTLC is a fully compliant method for determination of sugars in food. Application in the bioanalytical field was shown as well.

J. of Chromatogr. A 1218 (20), 3089-3084 (2011). Comparison of the separation of the structurally related angiotensin-converting enzyme (ACE) inhibitors lisinopril, cilazapril, ramipril and quinapril and their corresponding active diacid forms (prilates) by conventional TLC on silica gel with the separation on monolithic ultra-TLC (UTLC) phase. Technical modifications of the commercially available equipment for sample application, development and detection were necessary for the use with UTLC plates. Development in a modified horizontal developing chamber with ethyl acetate - acetone - acetic acid - water 16:4:1:2. Detection by absorbance measurement at 220 nm and after exposure to iodine vapors under daylight, as well as by image analysis. As a result the monolithic layer was more efficient for the separation of structurally similar polar compounds, such as prilates, than conventional silica layers. Confirmation of the identity of the compounds by ESI-MS after their online extraction from the UTLC and TLC plates.

J. Planar Chromatogr. 24, 331-336 (2011). HPTLC of pioglitazone (PIO), metformin (MET), and glimepiride (GLI) in pharmaceutical preparations on silica gel, prewashed with methanol, with acetonitrile - methanol - propanol - ammonium acetate solution 7:2:1:1 in a twin trough chamber saturated for 10 min. Quantitative determination by densitometry at 240 nm. The hRf value was 83, 21, and 89 for PIO, MET, and GLI, respectively. Linearity was in the concentration range of 300-1200 ng/band, 10-40 µg/band and 40-160 ng/band with correlation coefficients of 0.995, 0.996, and 0.998 for PIO, MET, and GLI, respectively. The LOD and LOQ was 57 and 171 ng for PIO, 6 µg and 18 µg for MET, and 12 and 36 ng for GLI. The %RSD for method and intermediate precision was below 2 %. The mean recovery (n = 5) was 98.2-99.5 % for PIO, 98.6-99.3 % for MET, and 98.7-99.7 % for GLI with %RSD between 0.4 and 1.3 %.

J. Planar Chromatogr. 24, 66-71 (2011). HPTLC of extracts of Stresroak premix and gallic acid (1), mangiferin (2), and withanolide A (3) as standards on silica gel with A) ethyl acetate - formic acid - acetic acid - water 100:11:11:27, for (1) and (2), and B) chloroform - methanol 9:1 for (2) in a twin trough chamber. Quantitative determination by absorbance measurement at 280 nm for (1), 330 nm for (2), and 225 nm for (3). The hRf values of (1), (2) and (3) were 76, 29, and 48, respectively. The average recoveries were 100.4 % (1), 99.3 % (2) and 98.0 % (3). The linear concentration range was 50-150 ppm for (1), and 40-100 ppm for (2) and (3). The LOD, defined as the amount of compound required to produce a signal at least three times the noise level, for gallic acid, mangiferin, and withanolide A was 80, 110, and 200 ng for (1), (2), and (3), respectively. The LOQ was 20, 27, and 38 µg, respectively.

J. Liq. Chromatogr. Relat. Technol. 34, 817-828 (2011). HPTLC of diclofenac (1) and ibuprofen (2) in aqueous environmental samples, on cyano phase with dichloromethane - methanol - cyclohexane 19:1:8. Detection by dipping into a Vibrio fisheri bacteria suspension for 3 sec. Then a glass plate was placed on top of the layer and a light-sensitive camera was used to measure the luminescence for 1 to 10 min. Linearity was between 10 and 2000 ng/zone. Limits of detection and quantification were 89 and 129 ng/band for (1), and 20 and 26 ng for (2). The coupling of HPTLC with a luminescent bacteria assay is suitable to determine drugs in aqueous environmental samples.