Isotope dilution liquid chromatography/mass spectrometry using a particle beam interface

Abstract

The use of a particle beam (PB) Interface for quantitation by Isotope dilution LC/MS was Investigated. Coelution of singlelabeled Internal standards (IS) with native compounds caused enhancement of the IS signal. The magnitude of enhancement for [3-13Ci]caffelne was affected by several experimental parameters, but no differences were observed In the 12C/13C response ratios under these conditions or upon analyte Introduction via a gas chromatography (GC) Interface. No coelution enhancement was observed with [ 1,3,7-13C3]caffelne, demonstrating that mass transfer effects and chemical complex formation do not affect PB transmission efficiency. Spectral overlap between native analyte and IS peaks and nonlinear detector responses cause the observed coelution enhancement. These results confirm that PB/LC/MS does not have Inherent limitations for use In Isotope dilution experiments as they have been performed by GC/MS. An equation was derived that permits accurate calculation of Isotope dilution results using a single-or multiple-labeled IS. Application of this equation could allow expansion of the Isotope dilution technique performed by PB/LC/MS or GC/MS to Include singlelabeled IS compounds without the need for nonlinear regression analysis of calibration curves.

Isotope dilution-liquid chromatography/electrospray ionization-tandem mass spectrometry for the determination of serum thyroxine as a potential reference method

“…These are particle beam (PB) LC/MS (e.g. for caffeine in coffee), 8 with thermospray (TSP) LC/MS (e.g.…”

Eluent Jet Interface for Combining Capillary Liquid Flows with Electron Impact Mass Spectrometry

“…However, coeluting internal standards were found to enhance the response of both analytes and standards. An alternative explanation for carrier effects was proposed by Doerge et al No coelution enhancement was observed with [1,3,7- 13 C 3 ]caffeine, instead of [3- 13 C 1 ]caffeine, demonstrating that mass transfer effects and chemical complex formation do not affect PB transmission efficiency. Spectral overlap between native analyte and nonlinear responses caused the observed enhancement.…”

“…Linearity. In the literature, nonlinear calibration curves have been reported at low concentration levels under LC/PB-MS [3][4][5][6][7][8] as well as under SFC/PB-MS conditions, 9 resulting in poor detection limits, reduced dynamic range, and quantification difficulties. In a recent extensive review, Creaser and Stygall 25 discussed these phenomena.…”

“…The use of PB interfaces has shown great promise, since the EI spectra obtained contain the fragmentation patterns necessary for unambiguous identification. However, quantitative analysis has been limited by fluctuations in absolute response observed in intra- and interday runs and nonlinearity at lower concentrations. − Besides, commercial instruments are not compatible with capillary flows resulting from microcolumn LC (micro-LC) and capillary electrophoresis (CE). On the other hand, in modern analysis, these capillary separation techniques are convincingly being used.…”

An eluent-jet interface for chemical ionization mass spectrometry and coupling of microcolumn liquid chromatography with electron ionization mass spectrometry

“…However, quantitative analysis with the PB interface introduces several problems, because of rather large fluctuations in absolute response commonly observed in intra-and interday runs and non-linear quantity vs. response plots at lower analyte concentrations. [2][3][4][5][6][7][8][9] In addition, compared with TSP, ES and APCI, PB interfacing often results in poor detection limits. The merits of PB-MS have been thoroughly reviewed by Creaser and Stygall 10 and recently by Cappiello.…”