Method Performance and Validation for Quantitative Analysis by 1H and 31P NMR Spectroscopy. Applications to Analytical Standards and Agricultural Chemicals

Abstract

Nuclear magnetic resonance (NMR) can be used to provide an independent and intrinsically reliable determination of chemical purity. Unlike chromatography, it is possible to employ a universal reference standard as an internal standard for the majority of chemical products assayed by quantitative NMR (QNMR). This is possible because the NMR response can be made the same for all chemical components, including the internal standard, by optimizing certain instrumental parameters. Experiments were performed to validate the quantitative NMR method described in this paper for the analysis of organic chemicals. Experimental precision, accuracy, specificity, linearity, limits of detection and quantitation, and ruggedness were systematically addressed, and system suitability criteria were established. The level of the major chemical ingredient can be determined with accuracy and precision significantly better than 1%, and impurities may be quantified at the 0.1% level or below. Thus, QNMR rivals chromatography in sensitivity, speed, precision, and accuracy, while avoiding the need for a reference standard for each analyte. Examples are given of (1)H and (31)P NMR used for quantitative analysis of agricultural chemicals, and a method for characterization of analytical standards is presented.