Characterization of Ultrasonic Cavitation Energy for Efficient Soil Pretreatment: A Novel Approach for Rapid Detection of Available Potassium and Phosphorus Using CE-C4D

Background: Soil sample pretreatment is a critical step in soil analysis, often involving complex processes and the use of organic solvents, which can lead to environmental pollution and inefficiency. In this regard, traditional methods are time-consuming and prone to human error, rendering them unsuitable for large-scale soil surveys. To address these challenges, this study proposes a novel rapid soil pretreatment method employing a device that integrates ultrasonic extraction with pure water and capillary electrophoresis using capacitively coupled contactless conductivity detection (CE-C4D). This study aims to enhance the efficiency and accuracy of soil nutrient analysis while minimizing environmental impact. Methods: Ultrasonic extraction using pure water as a solvent, combined with CE-C4D detection, was employed for rapid and efficient analysis of soil nutrients, particularly potassium and phosphorus. Parameters influencing ultrasonic extraction, including frequency, treatment time, and the relationship between solution factors and cavitation yield, were optimized through both simulations and experiments. Cavitation yield was assessed using iodine release, conductivity measurement, and fluorescence analysis. Additionally, the sound pressure distribution within the extraction tube was simulated, and temperature changes during ultrasonic treatment were monitored. The pretreatment device and detection method were validated using standard soil samples. Results: The optimal ultrasonic extraction parameters were identified as a frequency of 1.7 MHz and a treatment time of 10 minutes, resulting in the most effective cavitation yield. The use of pure water as a solvent improved both the efficiency of soil pretreatment and the environmental sustainability of the process. The CE-C4D system successfully detected available potassium and phosphorus in standard soil samples with high accuracy, showing trends consistent with standard values and relative standard deviations (RSD, n=4) of less than 5%. Blind tests on soil samples also demonstrated minimal error, with RSD (n=4) below 4%. Conclusion: This study presents a portable and efficient ultrasonic extraction device for soil pretreatment coupled with a custom-designed CE-C4D detector for the rapid analysis of available potassium and phosphorus. The use of pure water as a solvent significantly reduces environmental impact, simplifies the process, and enhances testing efficiency, reducing the required testing time from 15-20 days to within 30 minutes. This innovation provides a reliable solution for on-site soil analysis, offering potential applications in large-scale soil surveys and routine soil testing.