Head-Space GC Determination of Residual Amount of Chloroacetic Acid in Carboxymethyl Chitosan

Residual chloroacetic acid was indirectly determined by head-space GC. The sample (0.2 g) was dissolved ultrasonically with 3 mL of H2O in a head-space flask, and the solution was esterified at 70 ℃ in a water bath for 40 min by reacting with 2.5 mL of methanol and 1.5 mL of sulfuric acid. The sample was introduced under the head-space condition. The gaseous analyte was separated on HP-INNOWAX capillary chromatographic column, and determined by hydrogen FID. The time and temperature chosen for equilibration of the sample in head-space flask were 15 min and 85 ℃ respectively. Linear relationship between values of peak area and mass of chloroacetic acid was obtained in the range of 0.2-20 mg, with detection limit (3S/N) of 5.6 mg·L-1. The proposed method was applied to the determination of chloroacetic acid in substantial samples. Recovery was tested by standard addition method, giving values of recovery and RSD′s (n=5) in the ranges of 90.0%-92.0% and 0.7%-0.9%.