Investigation of problems associated with the determination of iodine in glacial acetic acid samples using flow injection analysis-inductively coupled plasma-mass spectrometry

Determination of iodine in glacial acetic acid is a major concern of acetic acid manufacturers and consumers. The use of ICP-MS for iodine determinati ons in acetic acid is hindered by memory effects that produce an elevated b ackground signal necessitating long rinse times between samples. In this wo rk, different analysis methods are employed in an attempt to minimize memor y and matrix effects allowing for the accurate determination of iodine in g lacial acetic acid using ICP-MS. Ammonium hydroxide solutions (3.7 and 7.4 M) were better at reducing the elevated iodine signal present after the int roduction of an acetic acid sample than water or 0.3 M nitric acid. Memory effects were decreased when the sample was introduced by flow injection rat her than constant sample aspiration. Peak areas generated by flow injection decreased significantly with increasing ammonium hydroxide concentration i n the carrier solution. Iodine determinations made with 1.7 M ammonium hydr oxide as the carrier solution were higher than determinations made with 3.7 M ammonium hydroxide as the carrier solution for the same samples, however , the percentage difference between the two determinations varied widely fr om sample to sample. All samples were analyzed by the method of standard ad ditions in an attempt to compensate for matrix effects. This work illustrat es the importance of the carrier solution in the determination of iodine in glacial acetic acid samples.