Using a flow-batch analyzer for photometric determination of Fe(III) in edible and lubricating oils without external pretreatment

In this study a flow-batch analyzer (FBA) was utilized and its feasibility was demonstrated for the determination of Fe(III) in edible and lubricating oils without external pretreatment. The FBA method uses the reaction of this ion with thiocyanate in organic medium. The formed red complex was monitored by employing a light emitting diode (LED, lambda(max) = 520 nm) and a phototransistor linked to the mixing chamber by optical fibers. All standard solutions were prepared in-line and all analytical processes were carried out by simply changing the operational parameters in FBA control software. Comparing with the reference method, no statistically significant differences were observed when applying the paired t-test at a 95% confidence level. The relative standard deviation, analytical frequency and limit of detection were estimated for both viscous matrices (edible and lubricating oils) at <2.1% (n = 3), about 95 h(-1), and 0.004 mg kg(-1), respectively. The recovery study shows results between 97.8% and 103.6% for both matrices. The FBA method showed better analytical features when compared with previous automatic flow methods. Thus, the FBA is potentially useful as an alternative for the determination of other ions in similar samples or in other viscous matrices without external pretreatment.