Development of a Sensitive High-Resolution Mass Spectrometry Approach for Urea Nitrogen Quantitation in Small Volumes of Bronchoalveolar Lavage Fluid (BALF)

A sensitive,
selective, and quantitative method incorporating high-resolution
mass spectrometry was developed for the determination of blood urea
nitrogen (BUN) in bronchoalveolar lavage fluid. The method requires
no sample cleanup or derivatization prior to analysis. High-performance
liquid chromatography (HPLC) on a Hypersil Gold PFP column (100 ×
3 mm, 3 μm particle size) connected to a C18 guard column was
employed for a 10 min chromatographic separation. The detection of
urea was achieved using a Thermo Scientific Q-Exactive Plus instrument
incorporating selected ion monitoring (SIM) modes for the protonated
adduct of urea. The urea analytical measuring range for the method
is 0.047–17.134 mg/dL, resulting in a BUN analytical measurement
range of 0.022–8.007 mg/dL, which allows for quantitation over
3 orders of magnitude (R2 = 0.999). In
addition, the method is suitable for small sample volumes (15 μL)
with a high level of accuracy, precision, and specificity.