Method validation and determination of total iodine in seaweed bathwater

Abstract

Abstract Seaweeds are a well-known natural source of iodine, although the quantity present varies depending on species, geographical location and season. Traditional seaweed baths contain hot water and seaweed but to date this bathwater matrix has not been studied. The objective of this study was to validate and apply the classical spectrophotometric Sandell-Kolthoff (SK) method for the analysis of total iodine in simulated seaweed bathwater. The principle of the method is based on the catalytic activity of iodide in the reduction of ceric ammonium sulphate being directly proportional to its concentration in the sample. Linear working range was from 30 μg l-1 to 300 μg l-1 iodine. The limit of detection (LOD) and limit of quantification (LOQ) were determined to be 9 μg l-1 and 29 μg l-1, respectively. The intra-assay repeatability indicated a mean coefficient of variation (CV) <2.5%. Inter-assay precision over 7 days indicated a CV of 6.7%. Recovery ranged from 87% to 114%. Addition of seaweed to simulated bathwater results in an increase in iodine which was found to be dependent on the length of contact time and on the temperature, with higher amounts released at longer immersion times and higher temperatures. The data confirms that traditional seaweed baths containing Fucus serratus stimulate the release of iodine into bathwater.