Sample Processing

Preprocessing of plasma and urine is required prior to NMR analysis to remove proteins, salts, and metal ions which degrade NMR spectra. Furthermore, the NMR spectra of plasma glucose or metabolites of glucose such as urinary acetaminophen glucuronide are a challenge to analyze. However, a derivative of glucose, monoacetone glucose (MAG) has more favorable NMR properties

sample-proc-1

Conversion of glucose to MAG. This derivative is soluble in non-aqueous solvents, avoiding use of lossy salt solutions. The molecule does not have anomeric forms, avoiding spreading signals for each carbon over more than one spectral region. Signals between carbons do not overlap, and long-range spin-spin couplings are more easily detected in 13C NMR spectra, increasing the information content of the spectra.

Chemspeed ASW2000 Automated Synthesis
Chemspeed ASW2000 Automated Synthesis

This laboratory has also developed the use of an automated solution phase synthesizer to handle sample preparation, including the conversion of both plasma glucose and urinary acetaminophen glucuronide to MAG. We are now able to offer a completely noninvasive analysis of hepatic intermediary metabolism by oral administration of 13C enriched substrates and analysis of urine.