A gas chromatographic method for determining the iodine content in milk powder was established, and the homogeneity and stability of iodine reference material were evaluated. Butanone derivative with iodine produced under acidic conditions was detected by gas chromatography (GC) with an electron capture detector and quantified by an external standard method. The proposed method showed a good linear relationship (R² = 0.9996), the recoveries from spiled samples were between 95.3% and 101.3%, and the relative standard deviation (RSD) was 2.3% (n = 6). This method had high accuracy and could be used for the determination of the iodine content in milk powder.

A high-throughput gas chromatography-mass spectrometry method was established for the analysis of 54 pesticide residues in milk. Samples were extracted with acetonitrile while shaking, and the extract was concentrated and purified using solid-phase extraction (SPE) on a C₁₈ column using acetonitrile as the eluent. The external standard method was used for quantification. The results showed that good linearity was observed over the concentration range from 0 to 1.00 μg/mL, with correlation coefficient (R²) greater than 0.990. Recoveries were between 43.33% and 113.87% with a relative standard deviation (RSD) of 1.8%-19.8% (n = 6). This method is accurate, simple and suitable for large numbers of milk samples.