Peak measurement in gas chromatographic/mass spectrometric isotope studies

✍ Scribed by Bluck, L. J. C.; Coward, W. A.

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 281 KB
• Volume: 32
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/(sici)1096-9888(199711)32:11<1212::aid-jms580>3.0.co;2-9

✦ Synopsis

A novel algorithm is described for the improved estimation of isotopomer ratios from gas chromatographic/mass spectrometric data. The minor isotopomer peak proÐle is Ðtted to an admixture of the major proÐle and its Ðrst and second derivatives. By this means allowance is made for non-coincidence in the measurement of the two proÐles. It is shown that a simple approximation for the derivative functions allows linear methods to be used to Ðt the digitized data for the minor to the data for the major and to that data shifted by one unit in both directions along the x-axis. By including the x-axis vector itself in the Ðt data superimposed on a linear baseline (i.e. with both slope and o †set) can be accommodated. The algorithm has been tested with both simulated data and real data obtained from a commercially available instrument. In addition, the data were analysed by traditional summation estimates of spectral intensity and by Ðtting to a particular lineshape, the exponentially modiÐed Gaussian. In all cases the proposed method is as good as, if not better than, the others, which, in conjunction with its simplicity, makes it a useful tool for the estimation of isotopomer ratios, with potential to improve precision of tracer techniques in metabolic studies.