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We propose a portable sensor, obtained by embedding luminol into the tetraethylorthosilicate/trietoxymethylsilane (TEOS/MTEOS) composite, for the quantitative determination of organic amino nitrogen and ammonium in water with the goal of achieving low levels of concentration. The method is based on the reaction between amino nitrogen compounds and hypochlorite to produce chloramino derivatives. Then, the remaining hypochlorite reacts with luminol sensor by producing a luminescence signal, which was measured by using a portable luminometer, being inversely proportional to nitrogen concentration. The liberation of the luminol from sensor is higher than 90% and the sensor is stable for at least a week at room temperature. This portable method was successfully validated and applied to the analysis of several real waters: fountain, river transition, lagoon, and seawater with recovery values between 92% and 112%, which indicated that the matrix effect was absent. The achieved limit of detection was around 10 µg·L−1, expressed as N. This sensor allows in situ monitoring owing to its simplicity, rapidity, and portability.

Paraquat (N,N′-dimethyl-4,4′-bipyridinium dichloride) is one of the most widely used herbicides owing to its high efficacy and low environmental persistence. However, because paraquat has significant acute toxicity, fatalities are often caused by accidental or voluntary ingestion of paraquat. In consideration of the strong toxicity and fast-Acting property of paraquat, on-site analysis at accident scenes should be effective in facilitating immediate medical treatment. In this study, a simple and rapid chemiluminescence assay using a portable luminometer was developed for on-site analysis of paraquat. The proposed assay is based on luminol chemiluminescence detection of superoxide anion radical resulting from the redox reaction between paraquat and dithiothreitol. Intense chemiluminescence was observed after mixing of paraquat and dithiothreitol in the presence of luminol. Because the chemiluminescence intensity was proportional to the concentration of paraquat, a quantitative measurement of paraquat was possible. The calibration curve for standard paraquat solution was linear from 0.025 to 2.5 μM with the correlation coefficient of 0.992; the detection limit (blank + 3SD) was 22 nM. The proposed assay was applied to determine paraquat in beverage samples after a cation exchange clean-up procedure. Given that the portable luminometer used in this study is small and lightweight, the proposed assay should be useful for on-site analysis of paraquat., Forensic Toxicology, 31(2), pp.301-306; 2013

Paraquat (N,N′-dimethyl-4,4′-bipyridinium dichloride) is one of the most widely used herbicides owing to its high efficacy and low environmental persistence. However, because paraquat has significant acute toxicity, fatalities are often caused by accidental or voluntary ingestion of paraquat. In consideration of the strong toxicity and fast-Acting property of paraquat, on-site analysis at accident scenes should be effective in facilitating immediate medical treatment. In this study, a simple and rapid chemiluminescence assay using a portable luminometer was developed for on-site analysis of paraquat. The proposed assay is based on luminol chemiluminescence detection of superoxide anion radical resulting from the redox reaction between paraquat and dithiothreitol. Intense chemiluminescence was observed after mixing of paraquat and dithiothreitol in the presence of luminol. Because the chemiluminescence intensity was proportional to the concentration of paraquat, a quantitative measurement of paraquat was possible. The calibration curve for standard paraquat solution was linear from 0.025 to 2.5 μM with the correlation coefficient of 0.992; the detection limit (blank + 3SD) was 22 nM. The proposed assay was applied to determine paraquat in beverage samples after a cation exchange clean-up procedure. Given that the portable luminometer used in this study is small and lightweight, the proposed assay should be useful for on-site analysis of paraquat.

A quantitative chemiluminescent method, enabling indirect identification of the peroxide-based explosives TATP (triacetone triperoxide) and HMTD (hexamethylene triperoxide diamine) has been developed. Treatment of these compounds with acidic solutions produced peroxides, which were transformed into radical derivatives by horseradish peroxidase (HRP) and then quantified by measuring the light emitted during their oxidation of luminol. The method was first developed in the microplate format and later optimized for a portable luminometer, to enable rapid application of the assay directly on site. When the portable luminometer was used each analysis took only 5-10 min. The method had good selectivity, sensitivity, and reproducibility; in the microplate format the limits of detection (LOD) and quantification (LOQ) were 40 and 50 ng mL(-1), respectively, for both TATP and HMTD. When the portable luminometer was used the LOD and LOQ were 50 and 100 ng mL(-1), respectively, for both compounds. Introduction of light emission-enhancing compounds did not improve the analytical performance of the assay. Imprecision (CV values) was always below 10%. Recovery varied rapidly with time, with an average value of 78% after 5 min. No false-positive result was detected on measurement of a variety of samples; this is an important feature for analysis on site. The method was applied both to contaminated materials and to fortified soil samples, simulating operational conditions.