SIMULTANEOUS ASSAY OF NITRITE, NITRATE AND CHLORIDE IN MEAT-PRODUCTS BY FLOW-INJECTION

A flow injection (FI) analytical method for the simultaneous assay of nitrite, nitrate and chloride in meat products is reported, The method is based on the potentiometric determination of chloride using a tubu lar ISE and on the spectrophotometric determination of nitrite. The FI system consisted in splitting the flow after potentiometric detection using a tubular detector and the subsequent confluence of the flow be fore reaching the spectrophotometric detector, This allowed the reduct ion of nitrate to nitrite in part of the sample plug on an on-line cop per cadmium reductor column. Since each channel had a different reside nce time, two peaks were obtained for nitrite and nitrite plus nitrate , Spectrophotometric determination was made after a diazotization-coup ling reaction. The results obtained were in good agreement with refere nce procedures and showed adequate precision (RSDs less than 6% for ch loride and nitrite and 2% for nitrate). A high sampling rate was obtai ned (120 determinations per hour corresponding to 40 samples per hour) .