J. Chromatogr. A 1218 (19), 2754-2774 (2011). HPTLC for lipid analysis is particularly useful for smaller, apolar compounds and offers some advantages over HPLC. Description of stationary phases, solvent systems and detection methods for the individual lipid classes (cholesterol and its derivates, glycerides, sphingo- and glycolipids, phospholipids). In comparison with common staining methods the combination of HPTLC and mass spectrometric detection methods is a very powerful method to investigate the identities of the HPTLC zones in detail.

Food Research International 44, 1088-1093 (2011). HPTLC of resveratrol (1) and the resveratrol complex with hydrogenated soy phosphatidyl choline (2) on silica gel with dichloromethane – methanol 4:1. The hRf values of (1) and (2) were 87 and 92, respectively.

Brazilian Journal of Microbiology 42, 172-180 (2011). TLC of patulin on silica gel with toluene – ethyl acetate – formic acid 5:4:1. Detection by spraying with 0.5 % aqueous methyl-benzothiazolinone hydrazone hydrochloride monohydrate, followed by heating at 130 °C for 15 min. Quantitative determination by absorbance measurement at 366 nm. Linearity was between 45 and 2100 µg/kg. The limits of detection and quantification were 0.005 µg/kg and 14 µg/kg. The relative standard deviation for repatibility was 6.2 %. Recovery (by standard addition) was 88 % for patulin.

Acta Chromatographica 22 (3), 419-431 (2010), DOI:10.1556/AChrom.22.2010.3.6. Simultaneous analysis of tamsulosin hydrochloride and dutasteride in tablet formulations by HPTLC on silica gel with toluene – methanol - triethylamine 18:3:2. Quantification by densitometry at 280 nm over the concentration range 200–2000 ng/band for both drugs. The recovery was 99.7 % and 100.1 % for tamsulosin hydrochloride and dutasteride, respectively.

J. Chromatogr. A 1218 (52), 9406-9413 (2011). Description of a simple, elegant method for the formation of a continuous stationary phase gradient for use in chromatographic separations, at the example of TLC. Gradient stationary phases were formed on activated HPTLC plates using a newly developed methodology termed “controlled rate infusion”. Reaction of the SiOH groups on the activated HPTLC plates with 3-aminopropyltriethoxysilane in a time dependent fashion by using a programmable syringe pump to control the rate of 3-aminopropyltriethoxysilane infusion into the deposition reservoir. The profile of the gradient was controlled by the infusion rate and visualized by the concentration-dependent color reaction of amino groups and ninhydrin. The advantages of such gradients were shown by optimizing the retention and separation of various components in different mixtures of 1) four weak acids and bases and (2) three widely used over-the-counter drugs. The separation was better on gradient stationary phases than on NP-TLC phases or amino phases. The retention and separation can be controlled by strategically modifying the steepness of the gradient.

J. Planar Chromatogr. 24, 211-213 (2011). HPTLC of exo-polysaccharides from bacterial fermentation and a series of mono-, oligo-, and polysaccharide reference solutions on silica gel with chloroform - toluene - 35 % formic acid - methanol 10:2:2:7 in a twin-trough chamber saturated for 1 h. Detection of starch-type polysaccharides by placing the plate into a twin-trough chamber saturated with iodine vapor. After drying determination by densitometry in absorbance mode at 400 nm. The plates were then immersed for 1 min in a solution of 10 % concentrated sulfuric acid in n-propanol - toluene 1:1, followed by heating at 115 °C for 10 min. The zones were evaluated visually and densitometrically at 400 nm.

J. AOAC Int. 94, 735-742 (2011). HPTLC and TLC of ofloxacin on silica gel with ethanol - conc. ammonia 4:1 in a horizontal chamber. Quantitative determination by fluorescence measurement at 313 nm. Simulated samples at a residue level of 1 mg/m² were prepared by spreading the calculated amount of ofloxacin solution on 1, 5, and 10 dm² stainless steel surfaces. The hRf of ofloxacin was 56. The mean recovery (n = 6) was 88.6-95.3 % with a CV of 3.8-4.9 %. The LOD was 0.6 ng/zone and the LOQ was 2 ng/zone, but it was shown that these can be lowered by immersion of the developed plate into a solution of liquid paraffin - n-hexane 1:2 to approximately 0.3 and 0.9 ng/zone. The repeatability (system precision) was 4.2 % for 2 ng, and 3.7 % for 20 ng. The recovery was between 88.6-95.3 %.

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 %.