Determination of Phthalates in Diet and Bedding for Experimental Animals Using Gas Chromatography-Mass Spectrometry

We have developed a gas chromatography–mass spectrometry method to measure five phthalates (dibutyl phthalate, butylbenzyl phthalate, di-2-ethylhexyl phthalate, diisooctyl phthalate, and diisononyl phthalate) in diets and beddings for experimental animals. The recoveries from diets and beddings spiked with five phthalates were 98.8%–148% with coefficients of variation of 0.4%–7.8% for diets and 94.7%–146% with coefficients of variation of 1.0%–5.0% for beddings. We analyzed commercial animal diets and beddings, and found that the levels of phthalates varied from sample to sample; the concentrations of five phthalates were 141–1,410 ng/g for diets and 20.5–7,560 ng/g for beddings.