Development of an automatic photometric titration procedure to determine olive oil acidity employing a miniaturized multicommuted flow-batch setup

Abstract

The present work proposes an automatic procedure for photometric determination of olive oil acidity, employing a miniaturized multicommuted flow-batch analysis setup without the use of calibration curves. Under microcomputer control, the proposed setup was able to mimic the manual procedure suggested by the European Commission Regulation. A homemade LED-based photometer was designed by coupling a radiation source and a photodetector to the titration chamber, creating a compact and downsized unit. The photometric titration of olive oil was carried out using potassium hydroxide solution in an n-propanol medium, which was done without any previous pretreatment, thereby allowing that a true photometric titration procedure in a non-aqueous medium was carried out for the first time. After establishing better operational conditions, the proposed procedure was applied to determine acidity in olive oil samples. The accuracy was assessed by applying the paired t-test to results obtained using a reference method, and there was no significant difference at a 95% confidence level. Other useful features were achieved, including a relative standard deviation of 1.8% (n = 6), a sample consumption of 125 μL per determination, an effluent generation of 1.4 mL per titration, and a sampling throughput ranging from 40 to 50 determinations per hour, whereby indicating that it could be an effective alternative for routine analysis of olive oil.