Abstract: Determination of iodine in glacial acetic acid is a major concern of acetic acid manufacturers and consumers. The use of ICP-MS for iodine determinations in acetic acid is hindered by memory effects that produce an elevated background signal necessitating long rinse times between samples. In this work, different analysis methods are employed in an attempt to minimize memory and matrix effects allowing for the accurate determination of iodine in glacial 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 introduction 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 rather than constant sample aspiration. Peak areas generated by flow injection decreased significantly with increasing ammonium hydroxide concentration in the carrier solution. Iodine determinations made with 1.7 M ammonium hydroxide 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 from sample to sample. All samples were analyzed by the method of standard additions in an attempt to compensate for matrix effects. This work illustrates the importance of the carrier solution in the determination of iodine in glacial acetic acid samples.

Abstract: Types of sample and reagent carry-over in continuous-flow and discrete automated analyzer.s are discussed, and their effect on analytical precision is indicated. It is concluded that, with the development of new types of analyzer., other types of carry-over may occur, which will need to be recognized and corrected for.

Abstract: The indirect flow injection method was based on the reduction of nitrate to nitrite using online Cd reductor consisting of a 300-mm Cu tube (i.d. 0.35 mm) followed by a 100-mm column packed with Cd granules (0.3 to 0.5 mm diameter); the small i.d. of the reductor tubes limited sample dispersion, thus maintaining a high sampling frequency. Nitrite was then determined colorimetrically by the Shinn method. Precision was good (ltn1%) over nitrate concentration. range of 0.4 to 4.0 mg L-1 and recoveries were >99%. Results agreed with those obtained with a segmented flow method. At a sampling frequency of 100 per h, the carry-over was 1%. In this indirect flow injection method, water was fed via a sampling valve (2.0 mL min-1), together with 1.0 mL min-1 buffer solution, to a cadmium reduction tube consisting of a small-bore copperized cadmium column. The effluent was passed to a mixing coil with 0.16 mL min-1 of color reagent comprising aqueous sulfanilamide and N-(1-naphthyl)ethylenediamine dihydrochloride. The absorbance was measured at 520 nm. Two variations of the method were evaluated: one used the color reagent as prepared and the other used the reagent in a 1:7 dilution. Both methods showed good accuracy and precision, but the latter gave the best compromise between linearity and sensitivity. At a sampling frequency of 100 h-1, the carry-over between consecutive samples was 1%.