Modelling the acid/base 1H NMR chemical shift limits of metabolites in human urine

INTRODUCTION: H NMR spectra of biofluid samples in metabolic profiling investigations typically suffer from extensive peak frequency shifting between spectra. These chemical shift changes are mainly due to differences in pH and divalent metal ion concentrations between the samples. This frequency shifting results in a correspondence problem: it can be hard to register the same peak as belonging to the same molecule across multiple samples. The problem is especially acute for urine, which can have a wide range of ionic concentrations between different samples. OBJECTIVES: H NMR chemical shift variations and limits of the main metabolites in a complex biological mixture. METHODS: H NMR spectra were acquired. CONCLUSION: H NMR spectra.