Large-scale human metabolic phenotyping and molecular epidemiological studies via 1H NMR spectroscopy of urine: investigation of borate preservation.

Author(s): Smith LM, Maher AD, Want EJ, Elliott P, Stamler J, Hawkes GE, Holmes E, Lindon JC, Nicholson JK

Publication: Anal Chem, 2009, Vol. 81, Page 4847-56

PubMed ID: 19453167 PubMed Review Paper? No

Purpose of Paper

Conclusion of Paper

Studies

1. Study Purpose

   The purpose of this study was to determine the effects of boric acid preservation and storage at -40 degrees C on urine analysis by NMR spectroscopy and ESI mass spectrometry.

   Summary of Findings:

   Only a few minor differences were observed between NMR spectra for specimens preserved with various concentrations of borate (3.07-30.74 mmol/L) and those without borate. Upon addition of borate, alpha-hydroxyisobutyrate methyl, methylmalonate methyl, and citrate exist both as free substances and as a borate complex in slow exchange. The mannitol peaks became broader upon addition of borate, suggesting a faster exchange between a free and complexed form. ESI MASS spectrometry confirmed the presence of borate complexes in a 1:2 borate to metabolite stoichiometry. The T1 relaxation time was found to be reduced by borate addition across the entire spectra which may reflect increased specimen viscosity. The T2 relaxation time showed far more specific effects on the proton values of the complexed molecules. The effects of storage time on the NMR spectrum were reported to be negligible. In conclusion, the effects of the addition of boric acid or specimen storage are specific to a few molecules and negligible compared to biological variation among specimens.

   Biospecimens

   • Bodily Fluid - Urine

   Preservative Types

   • Frozen
   • Other Preservative

   Diagnoses:

   • Not specified

   Platform:

   Analyte	Technology Platform
   Small molecule	NMR
   Small molecule	ESI MS

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Biospecimen Preservation	Type of fixation/preservation	Boric acid Frozen
   Storage	Time at room temperature	24 h
   Storage	Storage duration	0 days 1 day 2 days 7 days 14 days 28 days 91 days 182 days 364 days
   Storage	Storage temperature	-40 degrees C

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