Application of ethyl chloroformate derivatization for gas chromatography-mass spectrometry based metabonomic profiling

A new combined gas chromatography and mass spectrometry (GC-MS) method has been developed suitable for the urine sample treatment in aqueous phase with ethyl chloroformate (ECF) derivatization agents. The method has been extensively optimized and validated over a broad range of different compounds and urine samples. Analysis of test metabolite derivatives, containing spiked standards, or rat urine exhibited acceptable linearity, satisfactory intra-batch precision (repeatability) and stability, relative standard deviations (R.S.D.) less than 10 and 15% within 48 h, respectively. The quantification limits were 150-300 pg on column for most metabolites. Recovery of several representative compounds, at different concentrations, ranged from 70 to 120%, with R.S.D. better than 10% for rat urine. We were able to generally eliminate potentially confounding variables such as medium complexity, different urea concentrations, and/or derivatization procedure variability. Metabonomic profiling of 1,2-dimethylhydrazine (DMH)-induced precancerous colon rat urine using GC-MS with ECF derivatization was performed to evaluate the proposed method. The analytical variation of the method was smaller than the biological variation in the rat urine samples, proving the suitability of the method to analyze differences in the metabonome of a living system with perturbed metabolic network. Thus, the proposed GC-MS analytical method is reliable to analyze a large variety of metabolites and can be used to investigate human pathology including disease onset, progression, and mortality.