Thin-layer chromatography assay

Use of the cELISA to determine methoprene content of tobacco residues prepared as described above, showed that the extracts contained materials which interfered with the assay (Figure 8). Extracts of tobacco not only contained methoprene, but also plant substances that interfered with the assay. Thin-layer chromatography (TLC) was then used to clean up crude extracts from tobacco samples to reduce and/or eliminate interference. 

Chromatographic assays—thin-layer chromatography (TEC) LC with UV, fluorescence (EL) or mass spectrometric (MS) detection... 

Incubation of this Na-K ATPase preparation with phosphatidylserine decarboxylase leads to complete conversion of the 31 phosphatidyl serine molecules present per molecule of Na-K ATPase, again without significant reduction in Na-K ATPase activity. In this case the sensitivity of the phosphatidylserine assay (thin layer chromatography and amino acid analysis) is such that it can be stated that less than one phosphatidylserine molecule per molecule of enz3rme is left. 

Verification—organic impurities Assay Thin-layer chromatography (TLC)... 

Finally, the techniques of nmr, infrared spectroscopy, and thin-layer chromatography also can be used to assay maleic anhydride (172). The individual anhydrides may be analyzed by gas chromatography (173,174). The isomeric acids can be determined by polarography (175), thermal analysis (176), paper and thin-layer chromatographies (177), and nonaqueous titrations with an alkaU (178). Maleic and fumaric acids may be separated by both gel filtration (179) and ion-exchange techniques (180). 

Assay Methods. The primary assay for the streptovaricins is the microbiological assay using the agar diffusion method or a turbidimetric procedure (60). The streptovaricins can also be identified by paper (60,88) or thin-layer chromatography (3). 

Spectrophotometric deterrnination at 550 nm is relatively insensitive and is useful for the deterrnination of vitamin B 2 in high potency products such as premixes. Thin-layer chromatography and open-column chromatography have been appHed to both the direct assay of cobalamins and to the fractionation and removal of interfering substances from sample extracts prior to microbiological or radioassay. Atomic absorption spectrophotometry of cobalt has been proposed for the deterrnination of vitamin B 2 in dry feeds. Chemical methods based on the estimation of cyanide or the presence of 5,6-dimethylben2irnida2ole in the vitamin B 2 molecule have not been widely used. 

A thin-layer chromatography assay was developed for ffie simultaneous determination of the three major hydroxylated metabolites of antipyrine 409,410, and 411 in urine of humans and other animals (82JPP168) (Scheme 95). 

The active drug and metabolites can be detected from the urine by thin-layer chromatography, gas-liquid chromatography, or gas chromatography-mass spectrometry. However, assays are available only at specialized centers. Treatment of acute intoxication with mescaline is virtually identical to the treatment outlined for LSD intoxication. DOM-induced vasospasm responds well to intra-arterial tolazohne or sodium nitroprusside. Major life-threatening complications of hallucinogenic amphetamine derivatives include hyperthermia, hypertension, convulsions, cardiovascular collapse, and self-inflicted trauma. 

Fusari et al. [66] described a qualitative thin-layer chromatography (TLQ elution technique, for the assay of primaquine and other pharmaceuticals. 

Thin-layer chromatography has been used by Foppiano and Brown229 to assay the total neomycin B and C content of neomycin sulphate. The neomycin zone was scraped off the plate and reacted with orcinol/ferric chloride reagent, the absorbance of the resulting colour being measured at 665nm. By this procedure a precision of - 2% was achieved. 

SPE, chromatography (i.e., thin-layer chromatography, gel-permeation chromatography and HPLC) and on-line multi-dimensional chromatography. These techniques are rarely used in routine tablet assays due to their technical difficnlties, labor intensity and problems with recovery. 

Thin Layer Chromatography. TLC analysis of the WSAP was accomplished By application to silica gel G plates at a concentration of 0.1 mg and development to 14 cm with chloroform-methanol-water (60 35 8). Prior to sulfuric acid-char treatment, five components were visibly resolved. Following such treatment a total of 10 components were visualized. Duplicate plates were divided into six zones, which were scraped, eluted with methanol and assayed at a concentration of 0.2 mg equivalents... 

Due to the identical behavior of GT-3 (16) and GT-4 on thin layer chromatography in addition to the ileum assays, these toxins are considered to be very closely related, if not identical. GT-3 likely represents a water soluble carry-over in the initial diethyl ether partition. In light of this observation, the effects of the crude ESAP on the guinea pig ileum previously reported (16) are quite understandable. We surmise that the first phase of Immediate, but reversible inhibition was ellicitied by GT-1 and GT-2 which have already been shown to be competitive in nature (16), and the second, irreversible phase was caused by GT-3. 

Salicylic acid and Its metabolite were separated by two methods. The first was thin layer chromatography on cellulose with BAW solvent as for the In vivo metabolism studies. A quicker separation was achieved with a polyamide column. The entire 400 pL from an individual assay was placed on top of a 0.8 x 2.0 cm column packed with Polyamide-6 (Accurate Chemical and Scientific Corp.). The salicylic acid metabolite was eluted with 6 mL water but salicylic acid was retained. 3a70B scintillation fluid (Research Product International Corp.) was used to determine the radioactive content of the entire 6 mL of eluant. Separation of salicylic acid and its metabolite by polyamide column chromatography was verified by thin layer chromatography. 

The ability of an esterase or a -glucosidase to hydrolyze the in vitro generated metabolite was tested. An assay mixture that had been incubated for 22 h (ca. 50% conversion of salicylic acid) was incubated with either 10 units of hog-liver esterase (E.C. 3.1.1.1, Sigma Chemical Co.) at pH 8.0 or 20 units of -glucosidase (E.C. 3.2.1.21, Sigma) at pH 5.0 for 1 h at 37 °C. Salicylic acid and the metabolite were separated by thin layer chromatography with BAW and quantified by liquid scintillation chromatography. 

Cinnamyl anthranilate can be assayed by a method based on ester hydrolysis. Bulk samples of food-grade cinnamyl anthranilate have been analysed for purity by thin-layer chromatography and high-performance liquid chromatography. A method has been described for determining the content of this compound in food products by steam distillation followed by paper chromatography and examination under ultraviolet light it has a limit of detection of 1 pg (lARC, 1983). 

Qualitatively interpreted assays such as mucopolysaccharide electrophoresis (MPS-EP), urinary organic analysis and amino acid thin-layer chromatography (AA-TLC) are extremely important in biochemical genetics and yet are difficult to quality control. Some useful control measures often used include ... 

Increased porphyrins in clear fluid such as urine may be detected directly by their pink fluorescence if exposed to long ultraviolet (Fig. 7.3.2). The specificity of this screening assay may be improved if porphyrins are extracted by talcum [8]. These isolated porphyrins may be quantified using a spectrofluorimeter. As different porphyrias show specific excretion patterns, separation of the main porphyrins is desirable. The formerly used fractionated extraction enabled to separate the uroporphyrin fraction from the coproporphyrin fraction. In addition to uroporphyrin, the first fraction includes heptacarboxy- and part of hexacarboxyporphyrins, and in addition to coproporphyrin, the second fraction includes part of hexacarboxy- and pentacar-boxyporphyrins. Later on, thin-layer chromatography of methylester derivatives is used. 

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