Automated profiling of urinary organic acids by dual-column gas chromatography and gas chromatography/mass spectrometry

Abstract

A multi-stage screening and identification scheme for the diagnosis of inborn errors in amino acid, fatty acid, carbohydrate and intermediary metabolism is described. The method is based on a computerized analysis of data obtained with dual-column gas chromatography/FID (GC/FID) and gas chromatography/mass spectrometry (GC/MS) profiling of urinary organic acids. It involves: (1) isolation of the compounds by solvent or solid-phase extraction; (2) conversion into trimethylsilyl (TMS) or TMS-oxime derivatives; (3) GC/FID analysis on SE-52 and OV-1701 capillary columns; (4) tentative identification by comparing the methylene unit (MU) values on both columns with a user-built library of reference compounds; (5) quantitative evaluation of the excretion profile; and (6) analysis by GC/MS of samples with an abnormal profile using an automated peak identification programme.

Liquid–Liquid Extraction and Solid Phase Extraction for Urinary Organic Acids: A Comparative Study from a Resource Constraint Setting

“…Particularly the ill shaped peak of urea with large area, masks peak of benzoic acid as its retention time was near the retention time of urea. This finding of our contradicts with various previous studies which stated LLE isolates many unwanted neutral compound like urea highly from urine samples [11,15,23,24]. This could be averted by urease pretreatment of samples.…”

“…There is limited literature available that has compared both extraction procedures [10,11,15]. Within day precision and accuracy was obtained from six replicate extraction of same standard mixture by both extraction procedures in a day.…”

Cribado neonatal ampliado en la Región de Murcia. Experiencia de tres años

“…Para el aná lisis de á cidos orgá nicos en orina se utilizó un cromató grafo de gases acoplado a un espectró metro de masas (CG-MS) formado por un cromató grafo 5890 A de la serie II y un espectró metro de masas 5971 A (HewlettPackard, Analytical Products Group, Delaware, EE.UU.) 9 . Para la cuantificació n de aminoá cidos en sangre se utilizó un cromató -grafo de intercambio ió nico (Biochrom 30, Cambridge, Reino Unido).…”

Simultaneous retention index analysis of urinary amino acids and carboxylic acids for graphic recognition of abnormal state

“…For the I analysis, the peak area ratios of individual CAs positively identified in GC profiles were normalized to the peak area ratio of the largest peak and were plotted as a function of their reference I values in the form of a bar graph. Compared with retention time scale, the I scale was more substantial because it provides qualitative information on peak identities [13][14][15][16][17][18][19][20][21]. Moreover, the relative abundance of each peak allowed direct quantitative comparison between peaks and between samples.…”