Determination of total phthalate in urine by gas chromatography

While urine rarely contains significant quantities of phthalate diesters, it does contain a variety of metabolites (phthalate monoesters) including conjugates. In the absence of bacterial action following excretion, the metabolites retain an intact phthalate ring. A procedure for the hydrolysis of phthalate esters and metabolites to free phthalic acid, recovery and esterification of the acid, and gas chromatographic quantification of the product ester all relative to an intermal standard of 4-chlorophthalate has been developed. The assay spans the range of phthalate levels found thus far in human urine samples. The procedure can also be used to determine levels of isophthalate and terephthalate simultaneously with phthalate.