Solid phase microextraction-gas chromatographic–mass spectrometric determination of nitrous oxide evolution to measure denitrification in estuarine soils and sediments

A SPME-GC–MS method was developed to quantify nitrous oxide (N2O) to evaluate denitrification rates. There is a need for this sensitive and definitive N2O detection method to accurately measure the soil and sediment ability to convert anthropogenic mineral nitrogen loads to N2 through denitrification hence decreasing estuarine waterway pollution loading. This method is applied to measure denitrification, which is a major pathway for inorganic nitrogen removal, by incorporating the acetylene (C2H2) block method on anaerobic assays. Currently, denitrification is largely measured using GCs fitted with TCD or ECD detectors. With a mean R2 value of 0.996, the calibration curve spanned over three orders of magnitude (4.1–2030 nM) with a limit of detection (LOD) of 4.1 nM N2O (18 ppb) and a limit of quantification (LOQ) of 16 nM N2O (72 ppb). This detection method was valid with less than 15% relative standard deviation (RSD) and error for middle and high quality control (QC) points and less than 20% for low QC points on three experimental days. Measuring N2O using SPME-GC–MS technology allows for confidence in identification, high sensitivity, reproducibility, and short run times.