Extract paraquat from soil using aqueous alkaline solutions, then quantify by reducing with ascorbic acid and measuring UV-Vis absorbance around 610 nm. This simple, low-cost method avoids specialized equipment and provides effective recovery.

Thank you very much for your response Abdelhak Maghchiche. I have already attempted the extraction procedure using sodium chloride, and subsequently with ammonium chloride, as extraction agents. Additionally, I applied ultrasonic-assisted extraction followed by centrifugation. However, I have not been able to successfully recover paraquat, and I am currently uncertain as to where the methodological error may lie. It is worth mentioning that the soil I am working with is clay-rich and has a high organic matter content, which may be influencing the extraction efficiency.

Extract paraquat from clay-rich soil using aqueous alkaline solution (e.g., 0.1 M NaOH) with ultrasonic-assisted extraction, then quantify by reducing with ascorbic acid and measuring UV-Vis absorbance at ~610 nm for effective, low-cost analysis.

Paraquat Extraction and Quantification Protocol

1.Sample Preparation

- Air-dry and sieve soil sample (2 mm mesh).

2. Extraction

- Weigh 5 g of soil into a centrifuge tube.

- Add 50 mL of 0.1 M NaOH solution.

- Ultrasonicate the mixture for 30 minutes.

- Shake mechanically for an additional 30 minutes.

- Centrifuge at 4000 rpm for 10 minutes.

- Collect the supernatant.

3. Repeat Extraction

- Perform a second extraction on the residue with 50 mL 0.1 M NaOH.

- Combine supernatants.

4. Reduction for Quantification

- Add ascorbic acid solution (e.g., 0.1 M) to the combined extract to reduce paraquat.

- Allow reaction to proceed for 10 minutes at room temperature.

5.Measurement

- Measure absorbance of the reduced solution at 610 nm using a UV-Vis spectrophotometer.

6. Calculation

- Use a paraquat standard calibration curve to determine concentration in the soil extract.