Flow injection sequential speciation of free and total potassium in fortified wines

A flow injection system for the potassium speciation in fortified wines, using two detectors placed in series, is described. The free, or ionized form, is monitored in a tubular-shaped potassium ion-selective electrode, and the total potassium content in a flame emission spectrometer used as end-of-line detector. Potassium determinations can be carried out in a linear range from 300 to 2000 mg l ^-1 with a sampling-rate of 60 samples per hour. The results obtained were comparable to the conventional procedures using the same detection systems, and the precision was good (relative standard deviations below 3.1% for free potassium and 3.8% for total potassium).