Organic acids which form a broad class of compounds; are physiological intermediates formed in the basic metabolic pathways such as amino acid metabolism, fatty acid oxidation, lipid metabolism and Krebbs cycle. Organic acidemia is disorders caused by abnormal accumulation of organic acids in one or more of these metabolic pathways. Abnormal levels of organic acid are detected in the urine of people with chronic disease and neurological disorders. The analysis of organic acids is used in the early diagnosis or follow-up of health problems caused by amino acid and organic acid metabolism. TMS (trimethylsilyl) derivatives can be obtained using GC-MS technique and the following substances can be analyzed. Results are interpreted with internal standard (4-phenylbutyric acid).