An "on-off" fluorescent probe based on cucurbit[7]uril for highly sensitive determination of ammonia nitrogen in aquaculture water

Determination of Paddy Soil Ammonia Nitrogen Using Rapid Detection Kit Coupled with Microplate Reader

Indophenol blue colorimetry has been widely used for determining soil ammonia nitrogen, but this method has some disadvantages, such as complex reagent preparation, high toxicity, and long colorimetric time. Hence, we aimed to develop a rapid soil ammonia nitrogen determination method using a rapid detection kit. In order to select a suitable extractant, different concentrations of KCl and NaCl solutions were used to extract soil. The ammonia nitrogen content in different types of soils was determined using a rapid detection kit (purchased from Zhejiang Luheng Environmental Technology Limited Company) coupled with a microplate reader. The kit method was compared with the traditional indophenol blue colorimetry method. The results showed no significant difference between the 1 mol·L−1 KCl extraction kit method and indophenol blue colorimetry (p > 0.05). The linearity of the working curve was smooth, the linear detection range was 0.0−2.00 mg·L−1, the average relative standard deviation was 7.00% (n = 5), the standard addition recovery rate was 89.31−118.23%, and the detection limit were was 0.074 mg·L−1. We concluded that the 1 mol·L−1 KCl extraction kit method can be applied to determine the ammonia nitrogen content of paddy soil with different chemical properties. The 1 mol·L−1 KCl extraction kit method has the advantage over indophenol blue colorimetry due to its simple reagent preparation, convenient operation, and shorter detection time (the coloring and colorimetric time for 96 samples was only 30 min using the kit method coupled with a microplate reader). Hence, it has the potential for application due to its rapid determination of soil samples in large quantities.

Polarimetry-inspired feature fusion spectroscopy (PIFFS) for ammonia sensing in water

The sustainable use of water resources is inseparable from water pollution detection. The sensing of toxic ammonia nitrogen in water currently requires auxiliary reagents, which may cause secondary pollution. Benefiting from the ability of substances to change light characteristics, this work proposes polarimetry-inspired feature fusion spectroscopy (PIFFS) to detect ammonia. The PIFFS system mainly includes a light source, a quarter-wave plate (QWP), a linear polarizer (LP) and a fiber spectrometer. The target light containing substance information is polarization modulated by adjusting the QWP and LP angles. Then, the Stokes parameters of target light can be calculated by appropriate modulations. The feasibility of PIFFS method to detect ammonia nitrogen is verified by experiments on both standard water samples and environmental water samples. Experimental results show that inspired by the first Stokes parameter, the fused features provide superiority in classifying ammonia concentration. The results also demonstrate the effectiveness of support vector machine-based concentration classification and random forests-based spectral selection. The interaction between light and substances ensures that the proposed PIFFS method has the potential to detect other pollutants.