3,4-Dimethylpyrazole phosphate (DMPP) is a nitration inhibitor added to solid fertilizers. According to Japanese Testing Methods for Fertilizers (2022*), "7.7.a High-performance liquid chromatography method" under "7.7 3,4-dimethylpyrazole phosphate (DMPP)" should be carried out with a column filled with silica gel modified with octadecyl groups. The method mentions that this analysis is applicable to fertilizers containing DMPP, and Silica C18M 4D as a suitable column. In this application, DMPP was analyzed using C18M 4D. The calibration curve for DMPP showed high linearity with a coefficient of determination (R² = 0.9999) over the concentration range of 0.5 to 50 μg/mL. We prepared and analyzed a urea fertilizer (one of the target fertilizers) according to the Japanese Testing Methods for Fertilizers. Since DMPP was not detected in the sample, we performed recovery tests by spiking DMPP into the same sample. At a spike concentration of 0.185 mg/g, an average recovery of 102% (n=3) was obtained.

Sample Preparation according to "(4.1) Extraction"

1. (1)Weigh 1.00 g of urea fertilizer and place it into a 200 mL screw-capped Erlenmeyer flask. For the spike recovery test, add DMPP to the sample at this step.
2. (2)Add 100 mL of water to (1) and stir for 10 minutes using a magnetic stirrer.
3. (3)After standing, transfer a portion of the supernatant into a 1.5 mL screw-capped centrifuge tube.
4. (4)Centrifuge at approximately 8,000 x g to 10,000 x g for about 5 minutes and use the resulting supernatant as a sample.

*The version at the time of the application acquisition.

Sample: 10 µL
(Standard solution) 5 µg/mL of DMPP in H₂O
(Sample solution with DMPP) Urea fertilizer spiked with 0.185 mg/g of DMPP
(Sample solution without DMPP) Urea fertilizer

1. 1.DMPP (3,4-Dimethylpyrazole phosphate)