Optimization of a capillary electrophoresis-electrospray mass spectrometry method for the quantitation of the 20 natural amino acids in childrens blood.

This paper describes useful information on the capillary electrophoresis-electrospray ionization mass spectroscopy (CE-ESIMS) interfacing for the analysis of amino acids (AAs) in standard mixtures and in child plasma blood serum. The developed procedure allows quantitation of the 20 natural AAs, in a single run, without any derivatization. Limits of detection as low as 3-20 micromol/l (5-30 pg injected) per analyte were obtained with an efficiency of about 100,000 plates and a peak area relative standard deviation below 4%.

Spectroscopic characterization of the uptake of essential and xenobiotic metal cations in cells of the soil bacterium Azospirillum brasilense.

The results of flame (FAAS) or graphite furnace atomic absorption spectrometric (GFAAS) analyses are presented and discussed on the accumulation of essential metals (Mg, Ca, Mn and Fe contained in the cultivation medium) and traces of each one of the conventionally xenobiotic elements from the group V, Co, Ni, Cu, Zn or Pb, added to the medium in concentrations (0.2 mM) which do not essentially suppress growth of the bacterial culture, in cells of the plant root-associated nitrogen-fixing bacterium Azospirillum brasilense. Along with the essential cations assimilated by the bacterium, Zn and Cu were found to effectively accumulate in the biomass from the environment. The uptake of Co and Ni was significantly less pronounced, whereas Pb and V appeared to be present in cells in much lower concentrations than in the cultivation medium evidently showing no tendency to be assimilated by azospirilla. The effect of the above xenobiotics on the uptake level of the four essential elements provided evidence that they may compete for the formation of biologically active complexes with substances of both intracellular and extracellular localization. The analytical data obtained are compared with Fourier transform infrared (FTIR) spectra of intact vacuum-dried bacterial cells grown in a standard medium and under the conditions of an increased metal uptake.

Correlation between dioxin levels in adipose tissue and estimated exposure to Agent Orange in south Vietnamese residents.

To permit new epidemiologic studies of the effects of dioxin on humans in Vietnam, we evaluated a model for quantifying exposure to Agent Orange (exposure index) based on the residential histories of 27 Vietnamese subjects and on information about spraying from the U.S. Army records (Herbs Tape) and compared this index to the dioxin levels measured in the subjects' adipose tissue. The mean dioxin level was 7.8 ppt, and dioxin and furan isomer profiles were similar to those already reported in industrialized countries. In addition, there was a highly significant correlation between the levels of almost all the isomers, whatever their degree of chlorination. For the group of 27 subjects, we found a Pearson correlation coefficient of 0.36 (P = 0.07) between the dioxin levels and the exposure index after log-transformation of both variables. When the analysis was restricted to the 22 subjects with a positive exposure index, the Pearson correlation coefficient rose to 0.50 (P = 0.02). We conclude that despite the limitations and power conditions of the study, this result is encouraging because it will be useful for future epidemiologic studies in Vietnam.

Fragmentations of dipeptides in plasma desorption mass spectrometry: new rules for the sequence elucidation of oligopeptides.

252Cf plasma desorption mass spectrometry is well suited for determining both composition and sequence of unknown small oligopeptides. A systematic study of a large number of dipeptides first leads to establishing common rules of fragmentation from positive ion mass spectra. These rules are then applied to the sequence elucidation of larger peptides.