数字图像比色技术快速测定室内空气中甲醛的含量

Rapid Determination of Formaldehyde in Indoor Air by Digital Image Colorimetric Technology

按照GB/T 18883-2002附录A的要求采集室内空气,采集的气体样品用0.05 g·L^(-1)酚试剂溶液吸收,将所得显色溶液倒入8个比色皿,并排放置于自制数字图像比色装置的木箱中。摄影灯被固定在木箱小孔上方,为比色测试提供面光源,色温为5 500 K、光照度为3 000 lx。智能手机被倒立固定在木箱外部,摄像头与比色皿距离23 cm,通过小孔对木箱内的显色溶液进行拍摄。采用Adobe Photoshop CS6图像处理软件处理智能手机拍摄的图片,通过提取“G(绿色)”通道G值来定量检测甲醛。结果显示:甲醛的质量浓度在0.10~0.60 mg·L^(-1)内和G值的对数转换值呈线性关系,检出限(3S/N)为0.04 mg·L^(-1),测定值的相对标准偏差(n=8)为2.0%;用不同智能手机拍摄,所得标准曲线的相关系数均不小于0.997 0,说明方法的普适性较好;按照标准加入法进行回收试验,回收率为101%~103%;方法用于两个实际测试场景室内空气中甲醛的分析,所得测定值和GB/T 18883-2002酚试剂分光光度法的相对误差绝对值小于5.0%。

According to the requirements of appendix A of GB/T 18883-2002,indoor air was collected.The collected gas sample was absorbed with 0.05 g·L^(-1)phenol reagent solution,and the resulting chromogenic solution was poured into 8 colorimetric dishes.The colorimetric dishes were placed side by side in the wooden box of the self-made digital image colorimetry device.The photography lamp was fixed above the small hole on the wooden box to provide a surface light source for colorimetric testing,with color temperature of 5500 K and irradiance of 3000 lx.The smartphone was fixed upside down on the outside of the wooden box,and the camera was 23 cm away from the colorimetric dish.The chromogenic solution inside the wooden box was captured through a small hole.Adobe Photoshop CS6 image processing software was used to process images taken by the smartphone,and formaldehyde was quantitatively detected by extracting the G value of the"G(green)"channel.It was shown that the linear relationship between values of the mass concentration and the logarithmic conversion value of G value of formaldehyde was kept in the range of 0.10-0.60 mg·L^(-1),with detection limit(3S/N)of 0.04 mg·L^(-1),and RSD(n=8)of the determined values of 2.0%.The correlation coefficients of the standard curves obtained from shooting with different smartphones were not less than 0.9970,indicating that the proposed method had good universality.Test for recovery was conducted according to the standard addition method,giving recoveries in the range of 101%~103%.The proposed method was used for the analysis of formaldehyde in indoor air of 2 actual test scenes,and absolute values of relative errors between the determined values and those obtained by the phenol reagent spectrophotometry in GB/T 18883-2002 were less than 5.0%.