USE OF BIOMARKERS IN DIAGNOSIS BY ISOTOPIC DILUTION AND GASCHROMATOGRAPHY-MASS SPECTROMETRY
Pages 135-141
Monica Culea, Mesaros Cornelia
Abstract
Small volumes of 20 µl of plasma or blood spots were used for neonatal blood screening for diagnosis of
phenylketonuria and other metabolic diseases. The blood samples were derivatized as trifluoroacetylbutyl
esters and analyzed by gas chromatography coupled with mass spectrometry in the SIM mode. Regression
curves for some standard amino acids are used for quantitative determination of valine, leucine, proline,
phenylalanine and tyrosine. The method is a rapid tool for diagnosis of some neonatal diseases. Samples were
separated on a Rtx-5MS capillary column, 30 m x 0.25 mm, 0.25µm film thickness, using a temperature
program from 50oC(1min), then 6oC/min to 100 oC, 4oC/min to 200 oC, 20oC/min to 300 oC in scan mode or
50oC(1min), then 20oC/min to 310 oC in the SIM mode. The following conditions were followed: transfer line
temperature: 250oC, injector temperature:200 oC; ion source temperature 250 oC; Splitter: 10:1. Electron
energy was 70eV and emission current, 100µA. Quantitative determination of the amino acids of interest was
made in the SIM mode by selecting the highest ions of the mass spectrum and the m/z 155 for the internal
standard, 15N-labelled glycine.