On-line digestion in a focused microwave-assisted oven for elements determination in orange juice by inductively coupled plasma optical emission spectrometry

A flow injection system coupled to focused microwave-assisted oven was used for on-line orange juice sample digestion for determination of Ca, Cu, Fe, K, Mg, Mn, Na, P, and Zn by inductively coupled plasma optical emission spectrometry. The reactor coil was a PTFE tube (4.0 m long and 1.6 mm i.d.) positioned into the commercial glass tube of the focused microwave oven. Aliquots of 500 muL of sample and 1000 muL of reagent (80% v/v HNO3) were mixed in a confluence and carried out to the reactor coil by air carrier. The relative standard deviation for five replicates of sample was lower than 5.0%. Good recoveries varying from 91 to 111% were obtained for added concentrations of the interest elements. The results obtained using the proposed digestion system are in agreement with those obtained for total digestion at the 95% confidence level. With this on-line digestion system was possible to carry out 12 samples h(-1), minimizing contamination, saving consumption of samples and reagent and low residue generation.