Catalytic Chemical Vapor Generation Microplasma Optical Emission Spectrometry for Field Detection of Urea in Dried Blood Spots

Despite widespread acceptance of dried blood spots (DBS) as a robust sampling strategy for clinical diagnosis, the analysis methods based on DBS frequently require tedious sample pretreatments, and bulky and expensive instruments, resulting in analyte loss, high reagent blank, long analysis time and limiting its field analysis. Herein, a method coupling catalytic chemical vapor generation (CVG) to miniature point discharge emission spectrometry (mu PD-OES) was developed for the sensitive quantification of urea in DBS. In the presence of urease, the non-volatile urea contained in DBS could be catalytically converted to CO2 and NH3, which were separated from DBS and further swept into the mu PD-OES for its quantitation via monitoring carbon atomic emission line at 193.0 nm. Compared to the conventional methods, the proposed catalytic CVG not only eliminates extraction, centrifugal separation, and other tedious pretreatments but also provides an efficient and high anti-interference sample introduction means for mu PD-OES, allowing rapid, convenient, selective, and sensitive detection of blood urea. The proposed method provides a limit of detection (LOD) of 0.03 mM and a relative standard deviation (RSD) of 3.3% at 1 mM of urea with sampling 20 mu L of blood. The accuracy and practicability of the catalytic CVG-mu PD-OES were validated by successfully analyzing several finger blood samples. Owing to the advantages of the CVG and the mu PD-OES, the proposed method also provides promising potentials for the field determination of other clinical targets spotted on DBS with small sample volume consumption and high sensitivity.