Development of an Eight-Channel Oxidation Stability Analyzer for Biodiesel

Abstract

This research aims to develop an oxidation stability analyzer for biodiesel based on the EN 14112 standard, which is one of the quality requirements specified by the Department of Energy Business (2019). The developed prototype consists of eight measuring cells that can simultaneously analyze multiple samples. The measurement system records the conductivity in accordance with the standard method by monitoring the change in vapor conductivity generated during the oxidation process. The instrument employs a PID temperature control system and independently regulated dry-air flow through solenoid valves for each measurement cell. The conductivity is measured using an AC circuit and processed by a PIC18F252 microcontroller, which transmits the data to a computer via an RS-232/USB interface. Data acquisition and analysis are performed using the developed software OxyGraph V1.0, which automatically calculates the oxidation stability in hours. The precision of the developed instrument, expressed as the relative standard deviation (%RSD), was 1.40%. A strong linear correlation was observed between the results obtained from the developed instrument and those from a commercial analyzer, as indicated by the Pearson product-moment correlation coefficient (r = 0.9994). Furthermore, the Bland-Altman analysis demonstrated good agreement within the limits of agreement (±1.96 SD), indicating that the developed analyzer provides reliable performance suitable for practical applications. This system offers a cost-effective alternative to imported instruments and demonstrates strong potential for domestic implementation.