Evaluation and optimization of ion-current ratio measurements by selected-ion-monitoring mass spectrometry.
Anal Chem
; 73(13): 2976-84, 2001 Jul 01.
Article
em En
| MEDLINE
| ID: mdl-11467543
ABSTRACT
Stable isotopically labeled compounds are regularly used as internal standards in quantitation and as tracers of in vivo metabolism. In both applications, the ratio of unlabeled to labeled analogues is determined from an ion-current ratio measured by a mass spectrometer. The precision of the ion-current ratio measurement defines the detection limit for quantitation and for tracer enrichment measurement. We have used standard models of noise to develop a method that evaluates ion-current ratio noise (i) that varies with the signal intensity and (ii) that is signal independent. This model produces a simple equation that defines the ion-current ratio precision using constants that can be evaluated empirically from the measurement of two ion-current ratios from a single standard measured multiple times. We demonstrate that our approach can predict the effect of signal intensity, ion-current ratio magnitude, and internal standard or tracer choice on the measurement precision. The standard deviations predicted by our method are shown to equal standard deviations of samples measured experimentally. This method allows a simple evaluation of a mass spectrometry system and can define the precision of new quantitation and tracer methods.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Espectrometria de Massas
Tipo de estudo:
Prognostic_studies
Idioma:
En
Revista:
Anal Chem
Ano de publicação:
2001
Tipo de documento:
Article
País de afiliação:
Estados Unidos