Determination of tetramethylthiuram disulfide (thiram) for residual analysis in food using spectrophotometry coupled with a solid-phase reactor (SPR) in a flow system

Abstract

An analytical method was developed for quantification of the fungicide thiram (tetramethylthiuram disulfide), based on its capacity to complex Cu²⁺ ions. A solid-phase reactor (SPR) was coupled in a flow system containing a spectrophotometer as detector. The SPR consisted of a tube filled with finely ground resin, in which copper(II) phosphate was immobilised prior to polymerisation. Contact of thiram with the Cu²⁺ ions immobilised in the resin resulted in the formation of a strongly coloured Cu²⁺/thiram complex. Maximum absorbance of the Cu²⁺/thiram complex was obtained at a wavelength of 439 nm. The usefulness of the methodology has been evidenced by the determination of thiram residues in corn and bean grains. Previously, a variety of transition metal cations which would form coloured complexes with tetramethylthiuram disulfide were tested.

Keywords:

• flow injection analysis
• spectrophotometry
• solid-phase reactor
• thiram
• thiuram disulfide

Acknowledgements

The authors are thankful to São Paulo Research Foundation – FAPESP (05/01296-4) and CNPq (474367/2004-5) for financial research support. The authors thank SJT.