Matrix Effects in Detection of Phthalate Esters from Wheat by a Modified QuEChERS Method with GC/MS

Nowadays, there is a lack of information regarding the occurrence and the content of phthalate esters (PAEs) contamination in wheats. In this study, a QuEChERS-GC/MS method was validated to measure trace levels of 14 PAEs in wheats. The work also focused on the matrix effects (MEs) which were evaluated through the study of slope ratios obtained of solvent and wheat matrix curves. All of the PAEs had positive MEs, and the percentage values were in a range of 5.4% (diisobutyl phthalate) to 53.7% (di-n-hexyl phthalate). The average recoveries (spiked at 0.06, 0.20, and 0.60 mg kg(-1)) had been considered satisfactory values between 84.8 and 120.3% with relative standard deviations of 0.6-9.0% for intra-day precision and 1.0-8.6% for inter-day precision. The limits of detection and limits of quantification ranged from 0.1 to 2.5 mu g kg(-1) and 0.13 to 5.0 mu g kg(-1), respectively. Following the employment of a top-down empirical model, the relative expanded measurement uncertainties were in the range of 21-43% (coverage factor k = 2, at 95% confidence). Based on the established method, PAEs in seven commercial wheat were evaluated, where 5 out of 14 studied PAEs were revealed in all of wheats, ranging from 0.028 to 0.669 mg kg(-1). One of them exceeded the upper limits 0.3 mg kg(-1) set for dibutyl phthalate in China.