A Modern Apparatus for Performing Flash Chromatography: An Experiment for the Organic Laboratory.
A modern apparatus for performing flash chromatography using commercially available, prepacked silica cartridges has been developed. The key advantage of this system, when compared to traditional flash chromatography, is its use of commercially available silica cartridges, which obviates the need for students to handle silica gel. The apparatus has been tested for its ability to perform separations that are commonly found in organic chemistry teaching laboratories, and a laboratory module that combines the techniques of thin-layer chromatography, gas chromatography, and flash chromatography is described. The performance of this new chromatography apparatus was comparable to a traditional flash chromatography column.
Mutations, tissue accumulations, and serum levels of p53 in patients with occupational cancers from asbestos and silica exposure
In order to determine the relationship between mutations, tissue accumulations, and serum levels of p53 in occupational cancers, we used denaturing gradient gel electrophoresis and DNA sequencing of exons 5–9 of the p53 gene, immunohistochemical analysis for tissue identification of mutant p53 protein, and enzyme‐linked immunosorbent assay for serum levels of mutant p53 protein to examine for such alterations in a cohort of individuals with workplace exposure to asbestos or silica, and resultant lung cancers or mesotheliomas. DNA analysis detected mutations in 5 of 18 (28%) tumors, and tissue accumulations of protein were detected in 7 of 20 tumors; the agreement between mutational and immunohistochemical analyses was significant (κ˘ = 0.62, P = 0.002). Serum elevations of protein were detected in 4 of 11 (36%) cases with available serum samples; the agreement between tissue alterations and serum elevations was also significant (κ˘ = 0.71, P = 0.017). In addition, based on the analysis of banked samples, serum results tended to be consistent over time prior to the diagnosis of disease (positive predictive value = 0.67, negative predictive value = 0.83). These results suggest that serum levels of p53 are reasonably accurate in reflecting tissue alterations in p53 at the gene and/or protein level and may be early biomarkers of disease risk. Environ. Mol. Mutagen. 30:224–230, 1997. © 1997 Wiley‐Liss, Inc.
Novel method for the determination of the methoxyl content in lignin by headspace gas chromatography.
The paper reports on a headspace gas chromatographic (HS-GC) method for the determination of methoxyl in lignin. The method involves the quantitive cleavage of methoxyl with hydroiodic acid (HI) to form methyl iodide in a closed headspace sample vial at 130 °C for 30 min. After HI has been added, the sample is neutralized by injecting a sodium hydroxide solution; the methyl iodide in the vial was determined by HS-GC using a flame ionization detector. The results showed that the method has an excellent measurement precision (RSD < 0.69%) and accuracy (RSD < 3.5%) for the quantification of methoxyl content in lignin. The present method is simple and accurate and can be used for the efficient determination of methoxy1 content in lignin and related materials.