Evaluation of the schlieren effect employing a LED-based photometer with a long-pathlength flow cell for reagentless photometric determination of ethanol in distilled ethanolic beverages
Evaluation of the schlieren effect employing a LED-based photometer with a long-pathlength flow cell for reagentless photometric determination of ethanol in distilled ethanolic beverages
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使用带有长光程流通池的 LED 光度计对蒸馏乙醇饮料中乙醇的无试剂光度测定进行纹影效应评估
DOI：
10.1016/j.microc.2016.07.009
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
B. Reis
中科院分区：
文献类型：
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作者：
Diogo S. Silva;B. Reis
使用配有长光程流通池的自制 LED 光度计评估纹影效应，该光度计被用作开发自动光度测定程序的工具，用于蒸馏乙醇饮料中的无试剂乙醇测定。分析程序采用多换向流动分析歧管，使用电磁微型泵进行流体推进。为了评估纹影效应是否会受到流动池长度的影响，光度计设计为与光程长度范围为 50 至 250 毫米的流动池耦合。流量系统的控制和数据采集是使用通过串行接口连接到微型计算机的 Arduino Due 微控制器来执行的，该微控制器被编程为作为从机工作。在最佳操作条件下（采样环长度、流通池光路长度和 LED 发射波长），纹影效应产生的信号强度与水介质中乙醇浓度从 2.5% 到 60% (v/v) 呈线性相关，r= 0.9994。通过对蒸馏乙醇饮料中的乙醇进行测定来确定该程序的有效性，得到的结果与使用 AOAC 官方方法在 95% 置信水平下获得的结果一致。其他有用的功能包括每小时 52 次测定的采样率、0.8% 乙醇的检测限以及含有 38.6% (v/v) 乙醇的典型样品的 1.8% (n= 9) 标准偏差。
The schlieren effect was evaluated employing a homemade LED- based photometer furnished with flow cell of long optical pathlengths, which was exploited as a tool to develop an automated photometric procedure for reagentless ethanol determination in distilled ethanolic beverages. The analytical procedure employed a multicommuted flow analysis manifold, using solenoid mini-pumps for fluid propulsion. Aiming to evaluate if schlieren effect would be or not affected by the length of the flow cell, the photometer was designed to be coupled to flow cells with optical pathlengths ranging from 50 to 250 mm. The control of the flow system and the data acquisition were performed using an Arduino Due microcontroller coupled to a microcomputer through the serial interface, which was programmed to work as a slave. Under optimal operational conditions (sampling loop length, flow cell optical pathlength and LED emission wavelength), the magnitude of the signal generated by the schlieren effect was linearly related to ethanol concentration in aqueous medium from 2.5 to 60% (v/v),r= 0.9994. The efficacy of this procedure was ascertained by performing ethanol determination in distilled ethanolic beverages, yielding results in agreement with those achieved using the AOAC official method at the 95% confidence level. Other useful features include a sampling rate of 52 determinations per hour, a detection limit of 0.8% ethanol and a standard deviation of 1.8% (n= 9) for a typical sample containing 38.6% (v/v) ethanol.