Anal. Chim. Acta 1174 (2021) 3387022. Presentation of the next generation LabToGo system OCLab2 which was improved and made more robust e.g. by using print and media technologies in chromatography, so-called office chromatography (OC). The first LabToGo methods were developed in the field of food safety and quality for point-of-care or on-site usage. For application volume study,  HPTLC of different methanolic / propanolic Patent Blue V solutions on HPTLC silica gel with ethyl acetate - methanol - water - acetic acid 65:23:11:1 up to 50 mm. Evaluation in white light and  absorption measurement at 635 nm. For performance tests of plate imaging, HPTLC of benzoic acid and sorbic acid acid on HPTLC with ethyl acetate - toluene - acetic acid 25:25:1. For study of the illumination homogeneity, HPTLC of either sorbic acid, 7-hydroxy-4-methylcoumarin, or Patent Blue V on amino phase, evaluation at 254 nm (sorbic acid), 366 nm (7-hydroxy-4-methylcoumarin) and in white light (Patent Blue V), and in the OCLab2 at 278 nm, 365 nm, and white light, respectively, and scanning the plates at 254 nm 366 nm and 635 nm, respectively. For analysis of food dye mixture by OCLab2, HPTLC on silica gel with ethyl acetate - methanol - water - acetic acid 65:23:11:1 up to 5 cm, drying and capturing of plate images by the OCLab2 at 515-525 nm, 620-630 nm and 465-475 nm, video densitometry and evaluation using the open-source quanTLC software. For analysis of Stevia leave samples, the ethanolic extracts and four calibration levels of a steviol glycoside mixture were applied by OCLab2 for the hydrophilic interaction liquid chromatography (HILIC) separation on HPTLC silica gel with acetonitrile - water 5:1. Derivatization with 2-naphthol sulfuric acid reagent at evaluation in white light. For analysis of water and environmental samples, ink-printing the prepared samples on HPTLC silica gel MS-grade, focusing using acetone - water 4:1 up to 13 mm, drying,  developing with ethyl acetate - toluene 1:1 up to 70 mm, drying and capturing the plate images in white light, 254 nm and 366 nm. For biological detection, spraying the plate with A. fischeri bacteria suspension and capturing of images over 36 min with an exposure time of 60 s and a trigger interval of 3.0 min. 

Anal Chim Acta 1129 (2020) 76-84. Demonstration of a new hyphenated HPTLC-S9-AChE assay for detection of neurotoxic chemicals, including metabolic activation, at levels consistent with the threshold of toxicological concern (TTC) for organophosphates (OPs). The high sensitivity allows for the direct application of packaging migrates or extracts on the HPTLC plate without additional requirement steps. HPTLC of the ethanolic standards chlorpyrifos (CP), quinalphos (QP), eserine (ER), parathion (PT), nonylphenol (NP) and tris(nonylphenyl) phosphite (TNPP) at five different levels in the range of 0.5-10 mL/band (overall range for all six chemicals 0.1-1000 ng/band) on silica gel. After application, drying and pre-wetting the application bands by immersion up to 10 mm in water, then spraying the S9 mixture (7 mL each, 0.1 mg/mL) immediately on top of the start zones, followed by incubation at room temperature for 30 min. After drying plates for 20 min and 5 min chamber saturation, development with ethyl acetate - methanol - water 5:5:2 for ER; n-hexane - ethyl acetate - ethanol 16:3:1 for QP and PT; n-hexane - toluene - ethyl acetate 5:4:1 for CP, NP and TNPP. Evaluation in 254 nm, 366 nm and white light. Detection by immersion in AChE solution (6.6 U/mL plus 1 mg/mL bovine serum albumin in Tris-HCl buffer, 0.05 M, pH7.8) for 2 s, and incubating at 37 °C for 25 min, then immersing into the substrate-chromogenic solution (ethanolic solution of 1-naphthyl acetate  - aqueous solution of Fast Blue B salt 1:2 , 3 mg/mL each) for 1 s, drying for 10 min. Evaluation in white light, absorbance measurement at 546 nm (mercury lamp) using an inverse scan. The advantages of this straightforward workflow were demonstrated by comparison with the status quo microtiter plate assay. The method is a pragmatic new tool in risk assessment in general and can be transferred to further toxicities of interest and any other category of complex sample mixtures.

Sens. Actuators. B. Chem. 325, 128753 (2020). Leucomalachite green (1) and malachite green (2) and certain amount of highly dispersed potassium iodate titanium dioxide composites (0.1 M titanium butoxide was used as a precursor with 5 % potassium iodate solution to prepare KIO3-doped TiO2 nanoparticles). The sample was developed with chloroform - methanol 4:5. Detection by dipping into 5 % potassium iodine, followed by heating and then dipping into a zinc ion solution followed by heating at 80 °C. Linearity was in the range of 0.3–8.0 μg/mL for (1) and 0.1–4.0 μg/mL for (2), respectively. LOD and LOQ were 1.7 and 5.2 μg/kg for (1) and 0.9 and 2.7 μg/kg for (2), respectively.

J. Liq. Chromatogr. Relat. Technol. https://doi.org/10.1080/10826076.2021.1930556 (2021). HPTLC of patulin in apple juice on silica gel with methyl tert-butylether - n-pentane 9:5. Detection by spraying with 0.25 % methyl-benzothiazolinone hydrazone hydrochloride monohydrate in methanol, followed by heating at 105 °C. Quantification was performed using a 48-bit flatbed scanner for color measurements (in red, green, and blue). Quantification in fluorescence mode by use of a 16-bit CCD-camera and UV-366 nm illumination as well as a HPTLC DAD-scanner. The hRF value for patulin was 58. Linearity was between 5 and 800 ng/zone. The LOD and LOQ were 33 and 67 ng/zone, respectively.

Anal. Bioanal. Chem. 412, 4527-4536 (2020). HPTLC of 20 chemicals representative of migrants from plastic food contact materials on silica gel with chloroform - acetone - petroleum ether 11:5:5. Yeast estrogen screen was performed by spraying with yeast culture, followed by incubation at 30 ºC for 3 h. Detection by spraying with the indicator (2 mL 0.5 mg/mL 4-methylumbelliferyl-β-D-galactopyranoside-MUG in lacZ buffer), followed by incubation at 37 ºC for 20 min. Qualitative identification under UV light at 366 and 550 nm. The method was more sensitive than a microtiter plate YES (lyticase-YES). 

Anal. Bioanal. Chem. 411, 725-734 (2019). HPTLC of bisphenol A (1) and its nine brominated analogs, namely monobromobisphenol A (2), 2,2’-dibromobisphenol A (3), tribromobisphenol A (4), tetrabromobisphenol A (TBBPA) (5), TBBPA mono(methyl ether) (6), TBBPA mono(allyl ether) (7), TBBPA mono(2,3-dibromopropylether) (8), TBBPA bis(allyl ether) (9), TBBPA bis(2,3-dibromopropyl ether) (10) in chicken samples on silica gel with n-hexane - ethyl acetate - dichloromethane - acetic acid 25:5:5:1. Detection at UV 254 nm. Further analysis by high-performance liquid chromatography-diode array detector/triple quadrupole mass spectrometry. The hRF values for (1) to (10) were 30, 32, 33, 45, 58, 68, 69, 69, 91 and 86, respectively.  

J. Planar Chromatogr. 34, 183-186 (2021). HPTLC of carbosulfan in viscera sample (pieces of stomach, small and large intestine with contents, liver, spleen, kidney, and lungs) on silica gel with hexane - acetone 4:1. Detection by spraying with reagent A (10 % sodium hydroxide), then 10 min later with reagent B (2 g sodium nitrite added to 2 g copper acetate in 100 mL distilled water), followed by heating at 100 °C for 15 min. The hRF value for carbosulfan was 48. The color visibility of pink-colored zones was up to 72 h.

J. Planar Chromatogr. 33, 533-546 (2020). Review of chromogenic spray reagents for the detection and identification of organic pesticides by TLC and HPTLC. Specific applications for the analysis of organochlorine pesticides, organophosphate pesticides, carbamates and synthetic pyrethroids were described.