Comparison of Different Approaches for Estimation of the Detection Limit of Quantitative NMR

Abstract

Limit of detection (LOD), which indicates the detection ability of an analytical method, is an important parameter used in validating quantitative 1H nuclear magnetic resonance (NMR) method. Different approaches to evaluate LOD have been reported in literature, including the calibration curve approach, regression parameters-based approach, ASTM approach (proposed by American Society of Testing Materials), EPA approach (established by the United States Environmental Protection Agency) and the signal-to-noise ratio approach. In this study, systemic analyses and summaries of all mentioned approaches were given together with their principles, equations and characteristics. A novel approach based on signal-to-ratio regression curve for determining the detection limit was proposed, which can overcome weaknesses of the signal-to-noise ratio approach. The LOD of liquid-state 1H NMR method in the determination of sodium formate in aqueous solution was calculated using 5 different approaches. The influence of the number of scans on LOD was discussed. The results showed that the LOD was in the range of 10.4~14.4 μmol/L when the number of scans was 64 with 700 MHz NMR spectrometer. In conclusion, the study can provide a reference for determining the LOD of 1H quantitative NMR.

Keywords

• liquid-state nuclear magnetic resonance
• quantitative detection
• limit of detection (lod)
• signal-to-noise regression approach