Tetramethylammonium hydroxide (TMAH) is the compound most commonly applied for iodine determination in environmental samples but, at the same time, is very harmful for human health when used as an analytical reagent. For that reason, it is desirable to seek for alternative, equally rapid and easy-to-perform (but requiring less hazardous chemicals) methods of iodine analysis in environmental samples on the same detection level. The aim of the research was to assess the applicability of iodine determination in spinach after incubation of plant samples with 2% acetic acid in comparison with standard analytical procedure using solution of TMAH (tetramethylammonium hydroxide). Studies were conducted on spinach samples from two vegetation experiments carried out in pots and field including soil fertilization and foliar application of diverse iodine doses in the form of KI and KIO₃. Obtained results indicated a relatively high usefulness of sample incubation with 2% acetic acid for iodine determination in spinach plants. Still, the statistical significance of the relation (defined with the use of correlation coefficients) between iodine content determined in TMAH (x variable) and 2% acetic acid (y variable) was primarily influenced by iodine form, dose and method of its application during plant cultivation. In the pot experiment, values of correlation coefficients between tested variables were statistically significant and equal to r = 0.66. In the field study, values of correlation coefficients (between x and y variables) for plants with foliar application of KI and KIO₃ were statistically significant and equal to r = 0.99 and r = 1.00, respectively. Combined comparative analysis of data obtained in both experiments revealed that correlation between tested variables was statistically significant and its coefficient was equal to r = 0.80. Mean iodine recovery from fortified samples after incubation with 2 % acetic acid was 91.1% ±17.7% (n = 15), whereas using TMAH – 89.3% ±30.7 (n = 15).

29-38