Uncertainty measurement for automated macro program-processed quantitative proton NMR spectra.
Patrick A Hays1, Torsten Schoenberger
1Drug Enforcement Administration Special Testing and Research Laboratory, U.S. Department of Justice, 22624 Dulles Summit Court, Dulles, VA, 20166, USA, Patrick.A.Hays@USDOJ.gov.
Analytical and Bioanalytical Chemistry
|October 3, 2014
Summary
This study evaluates an automated quantitative proton nuclear magnetic resonance spectroscopy (qNMR) program. The program accurately determines processing uncertainty and combined qNMR results, validated with various chemical standards and illicit samples.
Area of Science:
- Analytical Chemistry
- Spectroscopy
- Organic Chemistry
Background:
- Quantitative proton nuclear magnetic resonance (qNMR) is a powerful tool for chemical analysis.
- Accurate determination of uncertainty is crucial for reliable qNMR results.
- Automated processing can enhance efficiency and reproducibility in qNMR.
Purpose of the Study:
- To evaluate a fully automated qNMR processing program.
- To determine the processing uncertainty of the automated qNMR method.
- To calculate the combined uncertainty of qNMR results using a trimmed purity average.
Main Methods:
- Collected 1359 quantitative NMR spectra of pseudoephedrine HCl at varying concentrations.
- Utilized maleic acid as an internal standard in D2O.
- Employed the median absolute deviation (MAD) statistical method to model uncertainty based on signal-to-noise ratios.
- Validated the model with chloroquine diphosphate and compared results with capillary electrophoresis for illicit heroin HCl samples.
Main Results:
- The automated qNMR program demonstrated reliable performance across a wide range of concentrations and signal-to-noise ratios.
- The 5436 calculated purities followed a normal distribution.
- The MAD method effectively modeled uncertainty relative to signal-to-noise.
- qNMR results for illicit heroin samples showed good agreement with capillary electrophoresis.
Conclusions:
- The automated qNMR processing program is effective for quantitative analysis.
- The developed method for uncertainty determination is robust and applicable.
- The trimmed purity average contributes to accurate qNMR result calculations.
- This automated approach offers a reliable alternative for analyzing various chemical substances.
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