J. Planar Chromatogr. 4, 194-198 (1991). Study of the retention behavior of different penicillin and cephalosporin derivatives on silica impregnated with tricaprylmethylammonium chloride (TCMA) by OPLC with eluents containing water and methanol. The basis of retention is hydrophobic interaction, controlled by the surface concentration of TCMA; main advantage: retention is independent of the pH of the eluent.

CBS 98, 5-7 (2007). HPTLC of gatifloxacin on silica gel in a saturated twin-trough chamber with n-propanol - methanol - ammonia 25% 50:10:9 over 80 mm. Quantitative determination by absorbance measurement at 292 nm. The hRf value of gatifloxacin was 60 and selectivity regardnig matrix was given. Linearity was between 400 and 1200 ng/band. The intraday and interday precision both were below 0.03 %. The limit of detection and quantification was 2.7 and 8.3 ng/zone, respectively. Recovery was between 99.2 and 101.9 %. The HPTLC method was suited to study gatifloxacin stability under different stress conditions according to ICH guidelines (acid, base, heat, oxidation, photostability).

Chinese J. Pharm. Anal. 26 (2), 221-224 (2006). HPTLC of gentamycin and related compounds on silica gel with chloroform – methanol – 25 % ammonia 5:7:6. The main compound is well separated from the impurities. Quantification by densitometry at 485 nm. Linearity was between 4.0 – 40 ng/spot (r2 = 0.99) and the limit of detection was at the low ng level.

Kinetic evaluation of the degradation process and identification of photoproducts by mass spectrometry. J. Liq. Chromatogr. Relat. Technol. 36, 2431-2445 (2013). HPTLC of difloxacin and its degradation products on silica gel with methylene chloride - methanol - 2-propanol - ammonia 25 % 4:4:5:2. Quantitative determination by absorbance measurement at 294 nm. The hRf values of difloxacin and its degradation products were 43, 25, 32, 39, respectively. Linearity was 1.2-2.4 µg/zone. LOD and LOQ were 0.01 and 0.03 µg/zone, respectively. Intermediate precision was below 2.0 %. Recovery (by standard addition) was in the range of 101.1-110.9 %.

J. Planar Chromatogr. 27, 124-131 (2014). HPTLC of sparfloxacin (1) and flurbiprofen (2) on silica gel with chloroform - methanol - formic acid 7:1:1. Quantitative determination by absorbance measurement at 258 nm. The hRF values for (1) and (2) were 45 and 75. Linearity was in the range of 100-600 ng/zone for (1) and 40-800 ng/zone for (2). The intermediate/interday/intra-day precisions were below 2 % (n=6). The LOD and LOQ were 30 and 90 ng/zone for (1) and 13 and 40 ng/zone for (2), respectively. Recovery (by standard addition) was in the range of 99.3-99.9 % for (1) and 101.1-101.3 % for (2).

J. Planar Chromatogr. 29, 273-280 (2016). HPTLC of piroxicam, tenoxicam, meloxicam and isoxicam on silica gel with ethyl acetate – toluene – butylamine 2:2:1. Detection under UV 290 nm. The method was applied to study the effect of oxidizing or reducing agents on the stability of these drugs.

CBS 120, 14-15 (2018). The drugs cefixime trihydrate (CEFI) and azithromycin dihydrate (AZI) were subjected to hydrolytic degradation (with water, 0.5 N HCl or 0.5 N NaOH), oxidative degradation (with 3 % and 30 % hydrogen peroxide), thermal degradation (heated at 100 °C and 200 °C for 1 h and 2 h) and photolytic degradation (exposed to fluorescent cold white light and UV light). HPTLC of CEFI, AZI, and the degradation samples on silica gel with ethyl acetate – methanol – acetone –_x000D_ toluene – ammonia 2:10:14:1:1 to the migration distance of 80 mm. Detection of AZI by immersion into sulfuric acid reagent (1:4 in ethanol) and heating at 100 °C for 5 min. Evaluation under UV 254 nm, UV 366 nm, and white light. Quantitative determination by absorbance measurement at 235 nm for CEFI and 530 nm for AZI. Linearity was in the range of 500–2500 ng/zone for CEFI and 50–250 ng/zone for AZI. The LOD and LOQ (ng/zone) for CEFI were 58 and 175, respectively, and for AZI 3 and 10, respectively. Precision (%RSD) was <2 %. In the forced degradation studies, CEFI degraded to 4 major products under different stress conditions. AZI showed only one additional peak upon acid and neutral hydrolysis.

R.E. KAISER (Ed). Proc. of the 3rd Int. Symp. on Instr. HPTLC, Würzburg, IfC, Bad Duerkheim (1985), 277-280. Optimization of the instrumentation of quantitative HPTLC for the analysis of antibiotics by off-line use of an autosampler, a TLC scanner and a computer.