Nitric Acid-based Partial-digestion Method for Selective Determination of Inorganic Arsenic in Hijiki and Application to Soaked Hijiki

Abstract

Because there is a great di#erence between the toxicity of inorganic arsenic (As) and organic As in food, the JECFA has set a PTWI value for inorganic As (iAs) rather than for total As. The di#erence in As toxicity makes it necessary to extract iAs completely from food samples for toxicological analysis, but complete extraction of As from most foods including seaweed has not been achieved to date. We developed a partial-digestion method that uses nitric acid as a solvent in order to extract almost all arsenicals from the solid matrix of hijiki (Hizikia fusiforme, a brown alga) samples. In this method, organic As species were not converted into iAs. HPLC/ICP-MS was then used to determine the concentration of iAs. Total As was measured by hydride generationatomic absorption spectrometry. The adopted conditions for 0.1 g of ground fine powder sample were: 2 mL of 0.3 mol/L nitric acid; heating, 80ῌ for 1 hr. Intra-laboratory validation of the method showed good precision and accuracy. The repeatability and intermediate precision for iAs were 1.5῍ and 1.5῍, respectively. The LOD and LOQ for iAs were 0.14 and 0.46 mg/kg dry weight, respectively. Recovery studies performed by spiking 0.5 mg/kg dry weight as the LOQ level and by spiking 3 mg/kg dry weight as the iAs concentration of an un-spiked hijiki sample showed good accuracy. The method was applied to hijiki samples after a water soaking process and a water soaking and simmering process. The results suggested that the As concentration in hijiki after both processes was lower than that before the treatments and that the water soaking and simmering process reduced the iAs concentration much more e#ectively than the water soaking process.

Arsenic Release from Foodstuffs upon Food Preparation

“…When exposure to As i is high, a biotransformation limit can be reached and As i is not further transformed but accumulates in the organism . Especially in the hijiki algae (Hizikia fusiformis) high concentrations of As i are reported, ranging from 30 to 117 mg kg –1 dry weight (DW), as sold. ,,, Concentrations of As i are mostly <0.8 mg kg –1 DW in other algae (e.g., nori, wakame, etc. ). , …”

Speciation Analysis of Arsenics in Commercial Hijiki by High Performance Liquid Chromatography-tandem-mass Spectrometry and High Performance Liquid Chromatography-inductively Coupled Plasma Mass Spectrometry

“…Gamble et al 32) reported that AsSug 408 and AsSug 482 were degraded to DMA via AsSug 328 in a basic environment. In acidic conditions, the formation of AsSug 254 26) and an increase in DMA with heating 33) were also reported. Both of our Boso hijiki products (#6 and #7) contained DMA at the concentration of 0.8 µg/kg dw hijiki, while the DMA levels in two raw hijiki samples (#8 and #9) were much lower (0.2 µg/kg dw hijiki), and these changes in DMA amount may be enhanced by heating.…”

A Simplified Questionnaire for the Assessment of Inorganic Arsenic Intake in a Japanese Population

“…Since the soaking method used for hijiki samples in the MAFF investigation was not published, it is possible that differences in the soaking process could be the reason. Soaking significantly reduces the iAs content of hijiki [ 12 ]. It may be more appropriate to use our measured hijiki iAs concentration for estimation because the soaking method employed in the present study [ 12 ] was close to that used in general households in Japan.…”

“…An additional 31 hijiki samples were purchased in Kanto District, Japan and were prepared for iAs analysis in our laboratory. The hijiki, sold in dried form, was soaked in 40 times its volume of purified water (e.g., 5 g in 200 mL) for 30 min, after which the water was discarded [ 12 ]. The soaked sample was then rinsed twice with 40 times its volume of purified water.…”