Caffeine determination by flow injection analysis employing Bovine Serum Albumin as a fluorophore

Abstract

A new methodology for caffeine determination was developed based on the quenching effect on fluorescent emission of the molecule of Bovine Serum Albumin at λem = 338 nm (λex = 280). A flow injection disposition was designed improving significantly the sampling rate to 60 samples/h using potassium dihydrophosphate 5 · 10-3 mol L-1 buffer (pH 6.8) as carrier and flow rate of 1.5 mL min-1. The experimental and instrumental conditions that influence on analytical quality parameters were systematically investigated, as consider: buffer nature and concentration, fluorophore nature and concentration, and carrier flow rate. The proposal is simple, fast, inexpensive and precise, with a linear range from 6.68 · 10-6 to 4.0 · 10-3 mol L-1 and SD of 0.0668, under optimized conditions. Methodology sensibility and selectivity allowed a variety of sample analyses. It was successfully applied to caffeine quantification in energy drinks, dietary supplements and sliming infusion samples without previous treatment.