Phosphine estimation in fumigated food grains using gas chromatography equipped with FPD detector

Phosphine, as per several reports, is considered to be an ideal and effective alternative to methyl bromide (MB) fumigant, phased out globally honouring 'Montreal Protocol'. The food grains fumigated with phosphine are perceived to be residue-free; however, estimation of its residues is imperative. In the present study, the phosphine residues were estimated in grains of wheat, rice, green gram, chickpea and yellow pea fumigated with different formulations of phosphine under 7 and 10 days exposure periods at various locations in India. For efficacy studies, the conventional aluminium phosphide (AlP) tablet (56% @2 and 3 tablet/MT) and granular AlP (77.5% @1.0 and 1.5 g phosphine/m³) formulations were applied. Each treatment including untreated control was replicated thrice. The concentration was monitored every 24 h until the end of exposure periods. Food grain samples were drawn before and post fumigation following a certain waiting period for estimation of phosphine residues using gas chromatography equipped with FPD detector. Residues in fumigated food grains were observed in traces in all the experimental stacks, but below the MRL (0.1 ppm), fixed by Codex Alimentarius Commission (CAC). Phosphine can be considered safe for use as an alternate fumigant in quarantine and long-term storage of food grains leaving residues below MRL.