Quantification of urea in serum by isotope dilution HPLC/MS

동위원소 희석 HPLC/MS에 의한 혈청 내 urea의 정량

  • Lee, Hwashim ;
  • Park, Sangryoul
  • 이화심 ;
  • 박상열
  • Received : 2004.11.24
  • Accepted : 2005.08.01
  • Published : 2005.08.25


Urea in blood has been measured as an effective marker for diagnosis of renal function. Urea which is e end-product of nitrogen containing metabolites such as proteins is filtered through glomeruli of kidneys and then excreted as urine. If the renal function is deteriorated, the urea concentration in blood will be increased, from which the healthiness of renal function is judged. In order to improve the confidence of diagnosis results, the results must keep traceability chain to certified reference materials, which was certified by primary reference method. In this study, we proposed isotope dilution-liquid chromatography/mass spectrometry (ID-LC/MS) as a candidate primary method, in which $15^N_2$-urea is used as an internal reference material. The developed method is highly accurate in principle and is convenient as it does not require cumbersome derivatization. 0.1 mmol/L ammonium chloride was selected as a mobile phase for HPLC because it provided low interference in MS analysis of relatively low molecular weighted urea. HPLC and MS were connected with an electrospray ionization (ESI) interface of positive mode, which provided high sensitivity and reproducibility. The developed method was validated with internationally recognized reference materials, and we have obtained satisfactory results in an international ring trial. The expanded uncertainty calculated according to ISO guide was 1.8% at 95% confidence interval. The developed method is being used as a primary reference measurement method such as for certification of serum certified reference materials (CRMs).


urea;isotope dilution-liquid chromatography/mass spectrometry;primary method;traceability


  1. C. A. Burtis and E. R. Ashwood, 'Renal Function and Nitrogen Metabolites' in 'Tietz Textbook of Clinical Chemistry', 3rd Ed., Vol. 3, p.1238, W. B. Saunders Company Ed., Philadelphia, U.S.A., 1991
  2. 新谷 英晴, 井上 剛, Bunseki Kagaku, 43, 807(1994)
  3. A. Takatsu and S, Nishi, Analytical Sciences, 11, 1021 (1995) https://doi.org/10.2116/analsci.11.1021
  4. Eric J. Sampson and Marie A. Baird, Clinical Chemistry, 25(10), 1721-1729(1979)
  5. J. K. Fawcett and J. E. Scott, J. Clin. Path., 13, 156(1960) https://doi.org/10.1136/jcp.13.2.156
  6. C. S. Phinney, K. E. Murphy, M. J. Welch, P. M. Ellerbe, S. E. Long, K. W. Pratt, S. B. Schiller, L. T. Sniegoski, M. S. Rearick, T. W. Vetter, R. D. Vocke, Fresenius J. Anal. Chem., 361, 71-80(1998) https://doi.org/10.1007/s002160050837
  7. Baoxin Li, Zhujun Zhang and Van Jin, Analytical Letters, 34(12), 1241(2001)
  8. 靑野 正, 松林, 公藏, 河本 昭子, 木村 茂昭, 土居 義典, 小澤利男, Japanese Journal of Geriatrics, 31(3), 232(1994)
  9. C. Eggenstein, M. Borchardt, C. Diekmann, B. Griindig, C, Dumschat, K. Cammann, M. Knoll and F. Spener, Biosensors and Bioelectronics, 14, 33(1999) https://doi.org/10.1016/S0956-5663(98)00103-1
  10. T. Tanigawa, Y. Mizo-oku, K. Moriguchi, T. Suzuki, T. Osumi and M. Odomi, J. Chromatography B, 683, 135(1996) https://doi.org/10.1016/0378-4347(96)00115-6
  11. Michael J Welch, Alex Cohen, Harry S. Hertz, Fillmer C. Ruegg, Robert Schaffer, Lorna T. Sniegoski and Edward White V, Anal. Chem., 56, 713-719(1984) https://doi.org/10.1021/ac00268a028
  12. O. B. Mortensen, M. Noehr, J. F. Moller-Petersen and I. Balslev, Danish Medical, Bulletin, 41(2), 237(1994)
  13. Anja Kessler, Lothar Siekmann, Clinical Chemistry, 45(9), 1523-1529(1999)
  14. B. G Wolthers, T. Tepper, A. Withag, G T. Nagel, T. H. Y. de Haan, J. J. van Leeuwen, C. A. Stegeman and R. M. Huibman, Clinica Chimica Acta, 225, 29(1994) https://doi.org/10.1016/0009-8981(94)90025-6
  15. M. S. Elisaf, H. J. Millionis and K. C. Siamopoulos, European Journal of Internal Medicine, 8(2), 127(1997)