Effect of l-cysteine on drying and neutron irradiation loss of Hg, Se, As, and Br from fish tissue

Powdered, thawed composited, and fresh frozen fish tissues were analyzed for Hg, Se, As, and Br. Experiments were designed to measure or estimate upper limits of long-term storage, drying, and instrumental neutron activation analysis (INAA) irradiation-related analyte losses. Tissue was analyzed as received (dried, if necessary, for INAA) and treated with l-cysteine to determine if such treatment reduces analyte loss, especially for Hg. Untreated tissues experienced large (23–49%) volatile Hg losses during irradiation. l-Cysteine treatment followed by freeze drying reduced Hg losses to 0.9–3.5%. Desiccation over Mg(ClO4)2 and oven drying at 40 °C of treated tissues were less successful at reducing Hg irradiation loss. Irradiation losses for volatile Se, As, and Br species were smaller, ranging from 0.06–0.4%, <0.01–0.11%, and 0.02–1.0%, respectively. Treated tissue drying losses for Hg, Se, As, and Br ranged from about 3–20%, ≤2–6%, <0.2–6%, and <0.3–3%, respectively, depending on drying method. There was some evidence that, unlike for Hg, l-cysteine treatment enhanced Se drying loss. There was little evidence of element loss during long-term storage at −80 °C, except for an 8% loss from Hg in desiccator dried, l-cysteine treated powdered fish protein.

► Up to half of untreated fish tissue Hg lost as volatile during neutron irradiation.
► l-Cysteine treatment, freeze drying reduced Hg irradiation loss by up to factor of 26.
► l-Cysteine treatment with desiccator or oven drying less effective for Hg retention.
► Se, As, and Br irradiation losses from fish tissues much lower (<0.01–1.0%) than for Hg.
► Up to 20% of Hg, 1% of Se, 6% of As, and 3% of Br lost during drying procedures.