Gas-liquid chromatographic determination of bromide ion in lettuce: interlaboratory studies.

The gas-liquid chromatographic method for the determination of bromide ion, as originally described for grain by Heuser and Scudamore, was adapted for use on lettuce, and later on products of other vegetable or of animal origin. After optimization of the ashing and derivatization conditions, 2 interlaboratory studies were carried out in The Netherlands. In the first, a preparatory study, 6 laboratories investigated freeze-dried lettuce; in the second definitive study, 8 laboratories investigated both freeze-dried and fresh lettuce. Four lots of lettuce with bromide contents ranging from about 5 to about 200 mg/kg were investigated. Average bromide contents (mg/kg) and between-laboratory coefficients of variation were 5.6 (11.0%), 13.3 (18.4%), 29.9 (8.3%), and 209 (12.8%). The results obtained are normal for the type of work and the conditions of the study. The method will be recommended for regulatory use in The Netherlands and in international organizations.