Determination of 1-Methyl-3,4,5-Trinitropyrazole and Its three Intermediate Products Prepared by One Pot Reaction by High Performance Liquid Chromatography

By optimizing chromatographic conditions such as column temperature, mobile phase, and flow rate, l-methyl-3,4,5-trinitropyrazole (MTNP) and intermediate products of 1-methyl-4-nitropyrazole (4-MNP), 1-methyl-4,5-dinitropyrazole (4,5-MDNP), and 1-methyl-3,5-dinitropyrazole (3,5-MDNP) prepared by one pot reaction were determined by high performance liquid chromatography. After diluting the reaction solution with acetonitrile, an appropriate amount of internal standard (2-nitrotoluene) was added, and the mixed solution was determined under optimized chromatographic conditions. The AT.C₁₈ chromatographic column was used as the stationary phase. Four targets were separated by isocratic elution at flow rate of 1.0 mL · min⁻¹ and column temperature of 30 ℃, with a mixture of acetonitrile and 0.1% (volume frantion) acetic acid solution at volume ratio of 45∶55 as mobile phase. Quantitative analysis was performed by internal standard method at detection wavelength of 265 nm. It was shown that the resolution of the 4 targets was greater than 2.5, and linear relationships between values of the mass concentration and the peak area ratio were kept in the range of 10.00-250.00 mg · L⁻¹ (MTNP and 4-MNP) and 10.00-350.00 mg · L⁻¹ (4,5-MDNP and 3,5-MDNP), with detection limits (3S/N) in the range of 0.40-0.80 mg · L⁻¹. The spiked recoveries were found in the range of 97.3%−105%, and RSDs (n=6) of the determined values were less than 1.0%.