Abstract This paper describes for the first time the use of emitter and receiver piezoelectric films coupled one in front of the other into a flow-batch analyzer for acoustic determination of free glycerol in biodiesel without chemicals/external pretreatment. Online extraction of free glycerol from biodiesel was carried out into aqueous solution without chemicals/external pretreatment. While the emitter piezoelectric is activated to sonicate the solution, the receiver piezoelectric translates the acoustic signal received into an electrical signal, which is measured and recorded by a digital oscilloscope. Multivariate calibration models were built for prediction of free glycerol concentration. In this sense, results of partial least square regression (PLS), the interval PLS (iPLS) and PLS coupled with the Successive Projections Algorithm for interval selection (iSPA-PLS) were compared. The proposed low-cost flow-batch analyzer exhibited good performance, satisfactory detection limit (0.12 mg kg−1) and a linear response from 72 to 372 mg kg−1 of free glycerol in biodiesel. The procedure was successfully applied to the analysis of biodiesel samples, and the results agreed with the reference method (ASTM D6584-07) at 95% confidence level.

中文翻译：

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发射器/接收器压电薄膜与流式分析仪耦合，用于在无化学品/外部预处理的情况下对生物柴油中的游离甘油进行声学测定

摘要 本文首次描述了将发射器和接收器压电薄膜一个在另一个之前耦合到流式分析仪中的使用，用于在没有化学品/外部预处理的情况下声学测定生物柴油中的游离甘油。从生物柴油中在线提取游离甘油是在没有化学品/外部预处理的情况下进行的。当发射器压电体被激活以对溶液进行超声处理时，接收器压电体将接收到的声学信号转换为电信号，由数字示波器测量和记录。建立多变量校准模型以预测游离甘油浓度。从这个意义上说，偏最小二乘回归 (PLS) 的结果，比较了间隔 PLS (iPLS) 和 PLS 与用于间隔选择的连续投影算法 (iSPA-PLS) 相结合。所提出的低成本流式分析仪表现出良好的性能、令人满意的检测限 (0.12 mg kg-1) 和生物柴油中 72 至 372 mg kg-1 游离甘油的线性响应。该程序成功应用于生物柴油样品的分析，结果与参考方法 (ASTM D6584-07) 一致，置信水平为 95%。