Quantitative analysis of urinary C-peptide by liquid chromatography-tandem mass spectrometry with a stable isotopically labelled internal standard.
We describe the first results of a quantitative LC-tandem mass spectrometry method for urinary C-peptide with the use of [2H14]C-peptide as internal standard. LC was based on gradient elution of a Hypersil PEP C18 column. Mass spectrometry was performed in the negative electrospray ionization mode and by monitoring of the transitions at m/z 1514/1334 ([2H14]C-peptide) and 1507/1320 (C-peptide). For sample preparation, we applied ultrafiltration. The analytical performance of the method in terms of measurement precision gave an RSD of <2% (n=10). The overall imprecision was investigated from independent analysis of two urine samples in six-fold and resulted in an RSD<5%. The limit of detection, expressed as signal-to-noise ratio 3, was approximately 0.15 ng C-peptide injected. Analysis of 10 random urine samples from laboratory volunteers showed interference-free ion chromatograms at a signal-to-noise ratio of approximately 75 on average. The C-peptide concentrations calculated from quantification by the bracketing calibration technique ranged from 32 to 165 ng/ml.
Fierens
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Laboratorium voor Analytische Chemie, Faculteit Farmaceutische Wetenschappen, Universiteit Gent, Ghent, Belgium.
Thienpont
L M
LM
Stöckl
D
D
Willekens
E
E
De Leenheer
A P
AP
D002138:Calibration; D002853:Chromatography, Liquid / Q000379:methods*; D003903:Deuterium; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods*; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D003903:Deuterium