Microanalysis of urinary electrolytes and metabolites in rats ingesting dimethyl terephthalate

Quantitative methods are described for the analysis of pH, sodium, ammonium, potassium, calcium, magnesium, chloride, phosphate, and sulfate, as well as terephthalic acid and dimethyl terephthalate, in a single urine sample as small as 20 microliter. The procedure utilizes ion chromatography and atomic absorption for electrolyte analysis, a microelectrode for pH measurement, and high-performance liquid chromatography for analysis of the organic compounds. The techniques are applied to urine samples freshly collected from rats ingesting dietary dimethyl terephthalate. Specific changes in urinary ions, including hypercalciuria and urinary acidosis, are shown to develop as a consequence of dimethyl terephthalate ingestion. The results indicate that metabolism of dimethyl terephthalate to terephthalic acid occurs extensively in Fischer-344 rats, and accounts for the ion changes that are observed.