Thin-layer Chromatography Strips Research Articles

Patch testing with serial dilutions and thin‐layer chromatograms of oak moss absolutes containing high and low levels of atranol and chloroatranol

Oak moss absolute (Evernia prunastri extract) contains a large number of substances, among them the potent allergens atranol and chloroatranol. Since 2008, their content in oak moss absolute has been restricted by the International Fragrance Association to a maximum level of 100 ppm each. To compare the elicitation capacities of a traditional (sample A) and a treated (sample B) oak moss absolute containing, in total, 27 000 and 66 ppm of atranol and chloroatranol, respectively, and to investigate reactions to components of oak moss absolute separated by thin-layer chromatography (TLC). Fifteen oak moss-allergic subjects were patch tested with serial dilutions and TLC strips of samples A and B. Fifteen subjects reacted to sample A at concentrations ≤ 2.0%, and 2 subjects reacted to sample B at 2.0% but not to lower concentrations. Among 13 subjects reacting to the TLC strip of sample A, 11 reacted to spots with retardation factor values corresponding to those of atranol and/or chloroatranol, and 11 reacted to other areas on the TLC strip. Only one subject reacted to the TLC strip of sample B. The patch test reactivity of sample B was significantly lower than that of sample A. The TLC patch tests indicate the presence of sensitizers other than atranol and chloroatranol in oak moss absolute.

Assisted disposable sensors for quantitative determination of.

A method for determination of arsenic is described. The sensor was constructed by immobilizing reagents on TLC (thin layer chromatography) paper. The reaction is based on chromogenic reaction of arsenic with a coupling complex of sulfanilic acid and N-(1-naphthyl) ethylene diamine dihydrochloride (NEDA) and formation of purple to magenta spots followed by scanner based detection. Changes in RGB values of color spots on TLC strips create a pattern. The obtained pattern was analyzed using MATLAB software. The proposed sensor is linear in the range 1-10 and 25-100 μg mL -1. The minimum detection limit found was 0.018 μg mL-1of arsenic.

Disposable sensor for quantitative determination of hydrazine in water and biological sample

A method for determination of hydrazine is described. The sensor was constructed by immobilizing a reagent on TLC (Thin Layer Chromatography) paper. This procedure is based on chromogenic reaction of hydrazine with p-(dimethylamino)benzaldehyde (reagent) and formation of red colour product followed by scanner-based detection. Changes in RGB values of colour spots on TLC strips create a pattern. The obtained pattern was analyzed by MATLAB software. The proposed sensor is linear in concentration range of 10–300 μg mL−1 of hydrazine and has practical detection limit of 0.1 μg mL−1. Parameters such as pH and concentration of p-(dimethylamino)benzaldehyde were optimized. The proposed sensor was successfully applied for the determination of hydrazine in bovine serum and tap water.

Patch testing of patients allergic to Disperse Blue 106 and Disperse Blue 124 with thin‐layer chromatograms and purified dyes

Former investigations have demonstrated that patch test preparations containing Disperse Blue (DB) 106 and DB 124 are impure. To investigate the significance of impurities in preparations of disperse dyes with regard to contact allergy. 21 patients allergic to DB 106 and/or DB 124 were tested with dilution series of commercial and purified DB 106 and DB 124. All patients were additionally tested with thin-layer chromatography (TLC) strips made from the commercial preparations containing DB 106 and 18 of them also with TLC strips containing DB 124. 13 of 21 and 12/18 patients tested positively to the strips of DB 106 and DB 124, respectively. Among these patients, 4/13 and 5/12, respectively, did not react to the main spot but reacted to other spots. Dilution series of purified DB 106 and DB 124 were positive in 10 patients each, while 16 and 15 patients, respectively, tested positively to the dilution series of the corresponding commercial disperse dye. Approximately 25% of the patients, diagnosed as contact allergic to DB 106 and DB 124, only reacted to impurities in the patch test preparations. This has implications for diagnosis and prevention.

Speciation of iron(II), iron(III) and full-range pH monitoring using paptode: A simple colorimetric method as an appropriate alternative for optodes

A new methodology for construction of a sensor array, to acquire signal patterns, is discussed in this article. This sensor is constructed by immobilizing an ionophore on a piece of paper (or porous material such as thin layer chromatography (TLC) plate) followed by charge coupled device (CCD) camera-based detection. This allows us to use non-transparent porous materials as a support for immobilization of ionophore. Changes in RGB values of color spots on pH paper or TLC strips create a pattern. The obtained pattern was analyzed using Microsoft Excel Solver. Full-range pH monitoring and speciation of ferric and ferrous ions in solution are discussed. A commercial multi-color pH strip was used as a typical prototype for full-range pH monitoring, and 4-methyl-2,6-bis (hydroxymethyl)phenol (or its halo-derivatives) and 1,10-phenanthroline were used as ionophores for determination of Fe(III) and Fe(II), respectively. Results of analyzed patterns showed a good correlation between predicted and true values of pH ( r = 0.9986), Fe(II) ( r = 0.9989) and Fe(III) ( r = 0.9978) with acceptable relative standard error.

Interfaces to connect thin-layer chromatography with electrospray ionization mass spectrometry.

This study has developed two interfaces to connect small-size thin-layer chromatography (TLC) with electrospray ionization mass spectrometry (ES-MS) for the continuous analysis of organic mixtures. The interfaces are (1) two bound optical fibers inserted into the C18-bonded particles at the exit of a small TLC channel and (2) a small commercial TLC strip with a sharpened tip. A reservoir continuously supplied a makeup solution to the tip of the TLC channel. The high voltage required for electrospray ionization was introduced into the makeup solution or mobile phase through a Pt wire, and electrospray was generated at the tip of the bonded optical fibers and at the sharp end of the TLC strip. Since small-size TLC channels were used, the elution time was short and less than 0.2 microL of the sample solution and 200 microL of the eluting solvent were required. Organic mixtures were separated successfully and detected on-line using the TLC/ES-MS techniques.

Radiotracer binding to brain microsomes determined by thin-layer chromatography

A thin-layer chromatography (TLC) assay was developed to monitor the interaction of radiotracers with brain microsomes. Murine brain microsomes were coated onto a zone of a TLC strip, the unreacted sites blocked with gelatin, and the radiotracers chromatographed over the microsomes. Radiotracers bound to the microsomes and were separated from the unreacted materials which migrated at or near the solvent front. Up to 80% of the applied radioactivity bound to the brain microsomes when using 99mTc-( d, l) hexamethyl-propyleneamine oxime (HMPAO) and 123I-(S)-2-hydroxy-3-iodo-6-methoxy-N-[(1-ethyl-2-pyrrolidinyl)methyl]-benzamide ( 123I-IBZM) as tracers. On the other hand, the presumptive negative control materials p-I-15-phenyl-pentadecanoic acid- 123I ( 123I-IPPA) and 99mTc-mercapto-acetyl triglycine (MAG3) bound poorly (7% and 4%, respectively). 99mTc-ethyl cysteinate dimer (ECD) interacted poorly (9.9%), a result thought to be consistent with its known inability to be metabolized by nonprimate brain tissue. Radiolabeled octreotide analogues (radiolabeled with 111In, I-131 or 99mTc) also bound, and the binding could be reduced by excess unlabeled octreotide. Also, chemical modification by acylation of Lys 5 in 111Inlabeled octreotide led to decreased binding (approximately 70%) compared to the original radiotracer. Chromatography of the various radiotracers over TLC strips coated only with gelatin was used to monitor nonspecific binding and was low and frequently below 5%. This technique does not require wash steps or centrifugation, and assays are rapidly completed. The assay could be useful in monitoring the interaction of radiotracers with brain microsomes and in evaluating and developing new radiotracers.

A new personal monitoring device for the detection of beta-propiolactone and other alkylating agents.

A personal monitoring badge has been developed for the detection of the direct-acting, alkylating carcinogen beta-propiolactone at atmospheric concentrations as low as 6 ppb for 24-hour and 0.6 ppm for 0.25-hour exposure. The method employs the trapping reagent p-nitrobenzyl pyridine (p-NBP) absorbed on a cellulose thin-layer chromatography (TLC) strip. Deoxyguanosine can be used in place of p-NBP, but its lower limit of detection is 60 ppb for 24-hour exposure. The authors also obtained positive results with the carcinogens bis (chloromethyl) ether, chloromethyl methyl ether, diepoxybutane, dimethylcarbamoyl chloride, ethyleneimine, and glycidaldehyde. In practice, the TLC strip is positioned in a filmbadge holder. The TLC strip monitoring badges are easy to prepare; they should encounter no resistance of personnel to their use since they are not cumbersome. Monitoring at the end of an exposure is simple and requires no expensive equipment or specialized personnel.

The quantitative assay of 3-hydroxy-3-methylglutaryl coenzyme A reductase: comparison of a thin-layer chromatographic assay with a rapid chloroform extraction assay

Two assays for the quantitative measurement of HMG-CoA reductase, the major regulatory enzyme in hepatic cholesterol biosynthesis, are described. The first of these procedures employs thin-layer chromatography (TLC) of the reaction product on plastic-backed silica gel G strips impregnated with ammonium carbonate. The TLC strip is then cut into 14 segments and each segment is assayed for radioactivity. Extraction efficiency and exact chromatographic mobility are monitored by the use of authentic [4-(3)H]mevalonolactone as an internal reference. A wide and complete separation is achieved between HMG and mevalonolactone. Also the radiochemical purity of biosynthetic [3-(14)C]mevalonolactone can be assessed by measurement of the (3)H/(14)C ratio across the mevalonolactone peak. While the TLC assay is accurate and sensitive, it is laborious. Therefore a second assay procedure was developed using chloroform extraction of an incubation mixture saturated with solid equal molar KH(2)PO(4)-K(2)HPO(4) at pH 6.8. Extraction efficiency was monitored by the addition of authentic [4-(3)H]mevalonolactone as an internal reference. The chloroform assay procedure was compared with the TLC procedure over a wide range of enzyme activities, both for rat liver microsomal HMG-CoA reductase and for solubilized enzyme. Excellent correspondence (r = 0.999) between the two assays was observed. TLC performed on the chloroform extract demonstrated that biosynthetic [3-(14)C]mevalonolactone was the only (14)C-labeled compound present in the extract. The chloroform extraction assay is rapid; 20-30 samples can be processed in 2-3 hr. This procedure should facilitate studies concerning the nature and regulation of HMG-CoA reductase.

An inexpensive sample applicator for thin-layer chromatography

A sample applicator for thin-layer chromatography (TLC), which is simple in design, inexpensive to construct, and ideal for applying small volumes of solutions to TLC strips or plates is described.