Validation of a QuEChERS-Based Gas Chromatography-Mass Spectrometry (GC-MS) Method for Analysis of Phthalate Esters in Grain Sorghum.

A modified QuEChERS method coupled with gas chromatography-mass spectrometry (GC-MS) was developed for analysis of 14 phthalate esters (PAEs) in grain sorghum (GS). Chemical extraction was done with acetonitrile followed by dispersive-solid phase extraction technique with a mixture of sorbents including primary secondary amine and octadecyl silica. Under the optimized condition, the matrix-matched calibration curves for all PAEs showed good linear relationship in the concentration range between 5 and 500 μg/L with correlation coefficients (R2 ) better than 0.99. Mean recoveries were between 82.0% and 120.2% at spiking levels of 0.06, 0.6, and 2.0 mg/kg with RSD of 0.3% to 7.8% (n = 5) for intra-day precision and 1.2% to 7.6% (n = 5) for inter-day precision. The LODGS and LOQGS for 14 PAEs were between 0.4 and 10.0 μg/kg and 0.5 and 20.0 μg/kg, respectively. Analysis of 32 commercial GS samples revealed that dimethyl-, diethyl-, diisobutyl-, dibutyl-, and di- (2-ethylhexyl) phthalate esters were detected in all of the analytes. In addition, content-color scale model was applied to visualize the concentration differences of PAEs in real GS samples. Principal component analysis of PAEs revealed that the GS samples did not have a distinctive cluster based on their geographic origins. The established method was proven to be simple, accurate, and effective for analysis of PAEs in GS, which might also be applied for analysis of PAEs in other matrices.

PRACTICAL APPLICATION: A modified QuEChERS-based GC-MS method was developed for the determination of phthalate esters (PAEs) in grain sorghum (GS). The ubiquitous presence of PAEs can migrate into GS. Therefore, evaluation of the total content of PAEs in GS is helpful to understand its impact of overall pollution level on other foods. This study has provided some basic information in terms of the content and contamination of PAEs in GS, which is helpful to establish relevant standards and risk assessment of GS for the government.