3,4-Dimethylpyrazole phosphate (DMPP) is a nitration inhibitor added to solid fertilizers. The Japanese regulation for “Testing Methods for Fertilizers (2022*)” mentions to use an octadecylsilylated silica gel column for DMPP analysis. A calibration curve for DMPP obtained using Silica C18M 4D showed a high linearity with a coefficient of determination (R2) 0.9999 in the concentration range 0.5 to 50 μg/mL.
Urea fertilizer, one of the target fertilizers, was analyzed. The extract was prepared in accordance with the Testing Methods for Fertilizers. DMPP was not detected in the extract of the fertilizer analyzed.  As a next step, addition recovery test was performed using the same sample (spiked DMPP concentration 0.185 mg/g). A good result was obtained with an average recovery rate of 102 % (n=3).

*The version at the time of the application acquisition.

Sample preparation

1. (1)Measure 1.00 g of urea fertilizer and put it in a 200-mL erlenmeyer flask. (For the spike recovery test DMPP was added to the sample at this point.)
2. (2)Add 100 mL of water to (1) and stir with a magnetic stirrer for 10 minutes.
3. (3)After allowing it to stand, transfer a portion of the supernatant to a 1.5-mL glass-stoppered centrifugal sedimentation tube.
4. (4)Centrifuge (8000 ~ 10000 x g for about 5 minutes) and use the supernatant as an injection sample.

Sample: 10 µL
Standard solution (5 µg/mL)
Sample solution spiked with DMPP (0.185 mg/g)
Sample solution

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