Choodum Aree, Boonsamran Pichapat, NicDaeid Niamh, Wongniramaikul Worawit
Applied and Environmental Chemistry Research Center, Andaman Environmental Research and Innovation Center, Faculty of Technology and Environment, Prince of Songkla University, Phuket Campus, Phuket 83120 Thailand; Trace Analysis and Biosensor Research Center, Prince of Songkla University, Hat Yai, Songkhla 90112 Thailand; Department of Applied Science, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112 Thailand.
Department of Applied Science, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112 Thailand.
Sci Justice. 2015 Dec;55(6):437-45. doi: 10.1016/j.scijus.2015.05.001. Epub 2015 May 29.
Digital image colourimetry was successfully applied in the semi-quantitative analysis of ammonium nitrate using Griess's test with zinc reduction. A custom-built detection box was developed to enable reproducible lighting of samples, and was used with the built-in webcams of a netbook and an ultrabook for on-site detection. The webcams were used for colour imaging of chemical reaction products in the samples, while the netbook was used for on-site colour analysis. The analytical performance was compared to a commercial external webcam and a digital single-lens reflex (DSLR) camera. The relationship between Red-Green-Blue intensities and ammonium nitrate concentration was investigated. The green channel intensity (IG) was the most sensitive for the pink-violet products from ammonium nitrate that revealed a spectrometric absorption peak at 546 nm. A wide linear range (5 to 250 mgL⁻¹) with a high sensitivity was obtained with the built-in webcam of the ultrabook. A considerably lower detection limit (1.34 ± 0.05mgL⁻¹) was also obtained using the ultrabook, in comparison with the netbook (2.6 ± 0.2 mgL⁻¹), the external web cam (3.4 ± 0.1 mgL⁻¹) and the DSLR (8.0 ± 0.5 mgL⁻¹). The best inter-day precision (over 3 days) was obtained with the external webcam (0.40 to 1.34%RSD), while the netbook and the ultrabook had 0.52 to 3.62% and 1.25 to 4.99% RSDs, respectively. The relative errors were +3.6, +5.6 and -7.1%, on analysing standard ammonium nitrate solutions of known concentration using IG, for the ultrabook, the external webcam, and the netbook, respectively, while the DSLR gave -4.4% relative error. However, the IG of the pink-violet reaction product suffers from interference by soil, so that blank subtraction (|IG-IGblank| or |AG-AGblank|) is recommended for soil sample analysis. This method also gave very good accuracies of -0.11 to -5.61% for spiked soil samples and the results presented for five seized samples showed good correlations between the various imaging devices and spectrophotometer used to determine ammonium nitrate concentrations. Five post-blast soil samples were also analysed and pink-violet product were observed using Griess's test without zinc reduction indicating the absence of ammonium nitrate. This demonstrates significant potential for practical and accurate on-site semi-quantitative determinations of ammonium nitrate concentration.
数字图像比色法通过锌还原的格里斯试验成功应用于硝酸铵的半定量分析。开发了一个定制的检测箱，以实现样品照明的可重复性，并与上网本和超极本的内置网络摄像头一起用于现场检测。网络摄像头用于对样品中化学反应产物进行彩色成像，而上 网本用于现场颜色分析。将该分析性能与商用外置网络摄像头和数码单反（DSLR）相机进行了比较。研究了红-绿-蓝强度与硝酸铵浓度之间的关系。绿色通道强度（IG）对硝酸铵产生的粉紫色产物最为敏感，该产物在546nm处有一个光谱吸收峰。使用超极本的内置网络摄像头获得了宽线性范围（5至250mgL⁻¹）和高灵敏度。与上网本（2.6±0.2mgL⁻¹）、外置网络摄像头（3.4±0.1mgL⁻¹）和数码单反相机（8.0±0.5mgL⁻¹）相比，使用超极本还获得了相当低的检测限（1.34±0.05mgL⁻¹）。外置网络摄像头获得了最佳的日间精密度（超过3天）（相对标准偏差为0.40%至1.34%），而上 网本和超极本的相对标准偏差分别为0.52%至3.62%和1.25%至4.99%。使用IG分析已知浓度的标准硝酸铵溶液时，超极本、外置网络摄像头和上网本的相对误差分别为+3.6%、+5.6%和-7.1%，而数码单反相机的相对误差为-4.4%。然而，粉紫色反应产物的IG受土壤干扰，因此建议对土壤样品分析进行空白扣除（|IG-IG空白|或|AG-AG空白|）。该方法对加标土壤样品也具有非常好的准确度，为-0.11%至-5.61%，五个查获样品的结果表明，用于测定硝酸铵浓度的各种成像设备与分光光度计之间具有良好的相关性。还分析了五个爆炸后土壤样品，使用未进行锌还原的格里斯试验观察到粉紫色产物，表明不存在硝酸铵。这证明了在现场实际准确地半定量测定硝酸铵浓度方面具有巨大潜力。
