Jingzhou Hou,Huixiang Wu,Xin Shen,Chao Zhang,Changjun Hou,Qiang He,Danqun Huo
A facile and effective colorimetric-sensing platform based on the diazotization of phenosafranin for the detection ofNO2−under acidic conditions using the Griess assay is presented. Diazotization of commercial phenosafranin produces a color change from purplish to blue, which enables colorimetric quantitative detection ofNO2−. Optimal detection conditions were obtained at a phenosafranin concentration of 0.25 mM, HCl concentration of 0.4 M, and reaction time of 20 min. Under the optimized detection conditions, an excellent linearity range from 0 to 20 μM was obtained with a detection limit of 0.22 μM. Favorable reproducibility and selectivity of the colorimetric sensing platform towardNO2−were also verified. In addition, testing spiked ham sausage, bacon, and sprouts samples demonstrated its excellent practicability. The presented colorimetric sensing platform is a promising candidate for the detection ofNO2−in real applications.Keywords:Griess assay;colorimetric;nitrite;phenosafranin
Ca 2+ is an important cation in coagulants used in the treatment of mine wastewater such as coal slime water, and its concentration directly affects the settling and flotation of coal slime water. The rapid determination of Ca 2+ concentration is of great significance to guiding industrial production. Herein, the complexation color development—visible spectrophotometry (CCDVS) method was proposed to obtain the concentration information of Ca 2+ , wherein 1-(1-Hydroxy-4-methyl-2-phenylazo)-2-naphthol-4-sulfonic acid (Calmagite) was used as an indicator and the mechanism of complexation between the indicator and Ca 2+ was explored. The strong correlation between spectral data and Ca 2+ concentration (R 2 = 0.997) indicated that this method could be used for Ca 2+ detection, thereby a quantitative model was proposed to predict Ca 2+ concentration by using the complexation color development—visible light absorption data. The chemical element and bonding analysis confirmed that Ca 2+ was complexed with the sulfonic acid group on the indicator skeleton in the form of Ca(OH) + intermediate in an alkaline environment. The generated complexation product (-S-O-Ca(OH) + ) could stably absorb 620 nm light energy, and its absorption performance remained 99.8% after standing for 60 min. The relative standard deviation of the detection results of Ca 2+ in different calcium source solutions was as low as 1.24%, which confirmed the strong calcium source compatibility of the proposed method. More importantly, the successful application of this method in the determination of Ca 2+ concentration at different points in industrial coal slime water system proved its advantages of high accuracy (relative error is as low as 5.01%), low cost and simple operation. The LOD of this method is 0.038 mg/L. Therefore, the complexation color development—visible spectrophotometry method can maximize the potential for cost reduction and efficiency improvement in mine wastewater treatment.
The paper-based analytical platforms have been applied in biochemical detection and environmental monitoring due to their low cost and easy operation. Despite their advantages, the complexity of fabrication has limited their further application. Here, a simple and innovative approach using parylene C, a material commonly used in semiconductors, is reported to fabricate paper-based chips and construct a point-of-care testing (POCT) platform through smartphones. Parylene C is deposited on the filter paper through a polydimethylsiloxane (PDMS) clamp and forms a hydrophobic barrier. A three-channel paper-based chip was utilized to detect aluminum (Al) ions on a smartphone platform by the chromogenic method. The color change after Al 3+ detection is represented with △E which was photographed and calculated by app on smartphone. The detection limit is 0.05 mg/L and the detection range is from 0.05 mg/L to 10 mg/L which indicates the application potential in the field of biochemical detection. This new paper-based sensing method and smartphone-based portable detection platform are simple, low-cost, fast, and highly sensitive, and provides a potential application for on-site, visual detection of ions and even other substances.
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