Urea
| Analyt: | Urea |
| Matrix: | Serum, Urine |
| Measuring Method: | GC-ID/MS |
| Standard: | Urea NIST 912b |
| Internal Standard: | ¹³C,¹⁵N₂-Urea |
| Sample Processing: | Samples are spiked gravimetrically with internal standard, equilibrated, then precipitated with ethanol, centrifuged and the supernatant evaporated to dryness. Derivatisation is with Damdee solution in pyridine followed by MSTFA in n-hexane. |
| Measurement: | Measurement at m/z 171 and m/z 174 |