基于LED的便携式牛乳亚硝酸盐含量检测仪研究

Design of Portable Detector on Nitrite Content in Milk Using Light-emitting Diodes

为了实现牛乳中亚硝酸盐含量的快速检测,基于亚硝酸盐在弱酸条件下与对氨基苯磺酸和盐酸萘乙二胺反应后生成紫红色偶氮化合物,从而影响可见光波段处光反射特性的原理,以发光二极管(LED)为光源设计了一种便携式牛乳中亚硝酸盐含量检测仪。首先,以市售牛乳为对象,以国家标准指出的NaNO为亚硝酸盐,采用连续投影算法从380~780 nm光谱范围内提取出用于检测亚硝酸盐含量的特征波长,并确定了5个波长(469、500、546、628、665 nm)的LED用于采集漫反射光照度。进而设计了由微控制器模块、光源模块、光传感器模块、电源和输入输出模块组成的检测仪。基于5个波长下的漫反射光照度,采用偏最小二乘回归法建立了定量预测牛乳中亚硝酸盐含量的模型。最后对检测仪的性能进行了验证。验证结果表明,该检测仪对亚硝酸盐质量浓度的检测误差为-0.13~0.07 mg/L,平均绝对误差为0.03 mg/L。

Nitrite content is one of the most important quality indices of milk.The traditional methods used to measure the nitrite content of milk are high in precision and good in repeatability,but the process is complex,the equipment is expensive,and these methods just can be used in the laboratory.To realize the detection of nitrite content of milk low in cost,fast and convenient in detection,a portable nitrite detector was developed based on the principle that a purple-red azo-compound was produced when nitrite reacted with p-aminobenzenesulfonic acid and naphthylenediamine hydrochloride under weak acid conditions.Taking commercial milk as object and the NaNOgiven in Chinese national standard as nitrite,the characteristic wavelengths for detecting the nitrite content was extracted from the spectra range of 380~780 nm by successive projection algorithm.Five light-emitting diodes at the wavelengths of 469 nm,500 nm,546 nm,628 nm and 665 nm were determined for collecting the intensity of diffuse reflected light.The developed detector consisted of a microcontroller module,a light source module,a light sensor module,a power supply,and an input and output module.Based on the intensity of diffuse reflected light at the five wavelengths,a partial least squares model was developed to predict the nitrite content of milk.The precision of the detector was verified,and the results showed that the measurement error on nitrite mass concentration ranged from-0.13 mg/L to 0.07 mg/L,and the average absolute error was 0.03 mg/L.