The Effect of Inorganic and Organic Pre-reducing Agents on Selenium Analysis in Tomato Sample using Microwave-Assisted Digestion Followed by FI-HGAAS

摘要

Optimum pre-reducing agents used to convert Se(VI) to Se(IV) for speciation analysis of inorganic selenium in tomato were investigated by Fi-HGAAS. It was found that optimal conditions of Se(IV) consisted of 2 M HCI as carrier and 0.3%(w/v) NaBH4 in 0.2%(w/v) NaOH as reducing agent. Concerning the completely pre-reduction of Se(Vi), various reducing agents were studied including KCI, KBr, Kl, ascorbic acid and thiourea in association with dilute and concentrate HCI and effect of temperature. From results, two optimal pre-reducing agents:0.5%(w/v) Kl/conc. HCI and 0.5%(w/v) thiourea/conc. HCI and heating for 30 min were chosen, giving a linearity between 5 and 25 ng/mL LOD and LOQ were 0.5 and 2 ng/L, respectively. Both of pre-reducing agents were then applied to tomato digest based on dry basis of its sample, which comparatively resulted in 5.10 mg Se(IV)/kg and 29.12 mg Se(VI)/kg using 0.5%(w/v) Kl/conc. HCI, and 3.84 mg Se(IV)/ kg and 22.29 mg Se(VI)/kg using 0.5%(w/v) thiourea/conc. HCI.