Analysis of nitrite from biological fluids by SERRS
 
  Marc Boris Dürner*, David Crowther*, Eric Demoncheaux#
 
  * Biomedical Research Centre, Sheffield Hallam University, Pond Street,
  Sheffield S11WB, UK
  # Division of Clinical Sciences, University of Sheffield Medical School,
  Sheffield S102RX, UK


Measurement of nitrate and nitrite as indicators of in-vivo NOS activity are
complicated by other NOx sources, e.g. dietary intake. Use of L-arginine with
a 15N stable lable allows determination of the NO pathway throughput, but
requires sensitive detection methods which are capable of isotopic
discrimination.

The product of the Griess assay is suitable for use in SERRS and a limit of
detection of 50nmol/L has been achieved, an increase in sensitivity over
absorbance detection. Isotopic Discrimination is possible through a bandshift
in the N=N stretch frequency, though limited to percentage levels by overlap
between the spectral bands for 14N=14N and 14N=15N vibrations and by spectral
noise. Matrix interferences seen with serum and urine samples could be
overcome by sample cleanup with solid phase extraction (SPE) cartridges.