Precoated plates

After removal of solvent in vacuo, the yellow residue is chromatographed on silica thin layer chromatography (TLC) plates using hexane-CH2Cl2(85 15) as eluent. The major product, 2, is a nearly colorless band observed at Rf = 0.17. This band can be seen better by using an UV lamp and UV sensitized TLC plates (precoated TLC plates, silica gel 60 F-254, layer thickness 0.25 mm, Merck). This band is separated from the starting material (Rf = 0.47) and several minor bands and the products are eluted from the silica gel with CH2C12. An analytically pure sample can be obtained by recrystallization from hexane at - 20 °C. Yield 0.053-0.070 g (30-40%). 

I. Thin-layer chromatography Mangalan et al. [53] used of an HPTLC method for the detection and determination of omeprazole in plasma levels. Plasma was extracted three times with dichloromethane at pH 6.5-7 and the combined extracts were evaporated to dryness at 60 °C. The residue was dissolved in dichloromethane and the solution was analyzed by TLC on aluminium-packed plates precoated with Silica gel 60 F254 with the upper organic layer of butanol-ammonium hydroxide-water (14 1 15) as mobile phase. The spots were observed by fluorescence quenching under UV light illumination at 280 nm the total area of each... 

The application of this technology for determining CYP induction in primary hepatocytes was first described by Strong et al. (40). To further demonstrate the potential of this technology, a study was conducted in our laboratory using primary human primary hepatocytes cultured on a 96-well plate precoated... 

Sorbent HPTLC plate precoated RPigFjj for Nano-TLC, Merck... 

The newly introduced HPTLC-LiChrospher Si 60 F254S precoated plates in many cases show a still better separation efficiency than the HPTLC silica gel 60 precoated plates. For example. Fig. 12a (HPTLC silica gel 60) and Fig. 12b (HPTLC-LiChrospher Si 60254s) how the scanned chromatograms of eight pesticides, all in the solvent system petroleum ether 40-60 °C + acetone (70 + 30 ml, without saturation of the chamber) [13a]. Also in the analysis of frankincense (olibanum), better separations were obtained on plates precoated with spherical silica gel than on those precoated with irregularly shaped particles [13b-dj. 

Practical Tip Forget the DAB recommendations and use normal TLC plates precoated with silica gel 60 without fluorescence indicator. If the only plates available contain this indicator, it does not matter for this example. This method, of comse, does not imply treatment of only one plate, and the impregnation process is not always successful every time. If you impregnate three plates, you will be on the safe side as a begirmer. 

Figure 22a shows the chromatogram on a sorbent layer which is not impregnated, and Fig. 22b shows the chromatogram on an impregnated TLC plate precoated with silica gel 60. However, a poorly performed impregnation leads to unusable TLCs, as shown in Fig. 22c. 

Standard Curve for ELISA of the Mn-SOD in Human Serum. Mn-SOD purified from human liver was serially diluted and then introduced into the wells of microtiter plates precoated with the Mn-SOD antibody, and then the assay was performed as described above. A typical standard curve for the ELISA using the pure human Mn-SOD and the PG-11 antibody is shown in Fig. 12. The lower limit of detection was 2 ng/ml and the working range was 2-200 ng/ml. Each point represents the mean SD. 

On the same day, coat a 96-well maxisorb black plate with 10 pg/mL neutravidin in PBS add 100 pL/well of the neutravidin solution and incubate the plate stationary overnight at 4 °C. Alternatively, commercially available black plates precoated with streptavidin could be used. 

When aluminum plates precoated with the mixture of silica gel 60 and Kieselguhr F254 ( 1.05567) were used, the selection of mobile phases depended on the kind of bile acids which are being separated. The mobile phase 25 20 8 (v/v/v) allows separation of all pairs of bile acids, with the exception of the pair of LC and DC. Using mobile phases in other volume compositions can separate the pair of LC and DC. In this case— the separation on the silica gel 60 and Kieselguhr F254 mixture—the biggest problem was to... 

Fig. 1 Densitometric profiles obtained for the investigated bile acids on aluminum plate precoated with silica gel 6OF254 (E. Merck, 1.05554) using n-hexane-ethyl acetate-acetic acid (22 21 5, v/v). Glycocholic acid (GC), glycodeoxycholic acid (GDC), cholic acid (C), glycohthocholic acid (GLC), cheno-deoxycholic acid (CDC), deoxycholic acid (DC), lithocholic acid (LC). (Camag densitometer, wavelength A = 250 nm slit dimensions 6 x 0.2 mm scanning speed 40 nm/sec).

The mobile phase n-hexane-ethyl acetate-acetic acid in a volume composition of 25 20 5 (v/v/v) is not optimal for separating all seven bile acids on aluminum plates precoated with silica gel 60 ( 1.05553). However, when this mobile phase is used, the difference between Rp values of C and GLC is 0.05, but the Rs of this pair of bile acids is smaller than 1 (/ y(c/oLC) = 0.96 see Table 1). To obtain complete separation of the seven examined bile acids on aluminum plates precoated with silica gel 60 ( 1.05553), a two-dimensional (2-D) technique was used. The first development used the mobile phase n-hexane-ethyl acetate-acetic acid in a volume composition of 25 20 5. Chloroform- -butanol-acetic acid-water (2 32 2 2, v/v/v/v) as mobile phase was used for the second development. The scheme of the chromatogram of separated bile acids with the use of a 2-D technique is presented in Fig. 2. The chromatogram indicates that, under these conditions, all the bile acids studied were completely separated. Better separation for C and GLC was obtained. 

Similar analyses were also used to compare the separations of studied bile acids. Both analyses showed that on the plates precoated with silica gel, the biggest problem was to separate GC from GDC. In the case of the separation on the silica gel 60 and Kieselguhr F254 mixture, the biggest problem was to separate C from GLC. The obtained results indicate that similar analysis can be an... 

Recently, the modified broadening index, detection index, densitometric visualizing index (DVl), and modified contrast index were used for the evaluation of detectabihty effects of salicylanilide, estradiol, and ibu-profen. Estradiol is a steroid compound, but it contains an aromatic ring with hydroxyl group about phenohc character. Salicylanilide was detected on glass plates precoated with a 0.50 mm layer of sihca gel 6OF254 (E. Merck, 1.05744) and with a 0.25 mm layer of silica gel 6OF254 (E. Merck, 1.05715), as well as on aluminum plates precoated with a 0.20 mm... 

Fig. 3 Spectrodensitograms of salicylanilide on glass plates precoated with 0.50 mm layer of silica gel 6OF254 (E. Merck, 1.05744) A, without the use of a visualizing reagent B, with the use of brilliant green as a visualizing reagent.

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