Validation of a spectrophotometric methodology for a rapid iodine analysis in algae and seaweed casts

Abstract

Iodine plays an important role in human metabolism and its deficiency is particularly harmful in pregnancy and childhood. It remains a major public health concern in many countries, especially in Portugal. The main purpose of this work was to develop a validated spectrophotometric analysis for a fast and reliable iodine quantification in algal samples. Absorbance was determined at 410 nm demonstrating a good linearity (R2 ≈ 1.0) in the range of 0–0.06 mg I/100 g. LOD and LOQ were 1.7 × 10−3 and 5.0 × 10−3 mg I/100 g, respectively. Accuracy was determined using recovery and varied between 101 and 118%. For precision analysis, an intra-day test performance (RSD = 8.7%) and a repeatability assay (RSD = 3.8%) were performed. Matrix effect assessment demonstrated that this had a negligible effect (3.2%) in the iodine quantification. The spectrophotometric method was externally validated, for iodine quantification in algal samples, by INSA certified laboratory. The correlation coefficient between external iodine quantification and our work was R2 ≈ 0.9, showing a good correlation. Applicability was assessed in 25 macroalgae species (5 green, 9 red and 11 brown), 12 seaweed casts, collected in Canary Islands and 1 microalga (Isochrysis galbana) provided by ITC (Instituto Tecnologico de Canarias).