High‐sensitivity liquid chromatography–combustion isotope ratio mass spectrometry of fat‐soluble vitamins

Abstract

The sensitivity of high-precision liquid chromatography/combustion isotope ratio mass spectrometry (LC/C-IRMS) was improved by more than two orders of magnitude by modifications which permit optimization of flows. The lower limits for high precision are about 3 pg of analyte on-column for flow injection and LC modes. Pneumatic aerosol spray coating was implemented and compared with simple dip coating. The signal enhancement for aerosol compared with dip coating is up fourfold at higher levels but drops to less than twofold at lower levels, while the dynamic range is extended at higher levels by fourfold at high sample load levels. LC separations for underivatized tocopherols, retinyl acetate and ergocalciferol are demonstrated with precision and accuracy of about 6I3C < 2.5% for replicates. This work demonstrates sensitivity useful for a wide range of LC analyses and extends high-precision LC/C-IRMS to the determination of several fat-soluble vitamins.

Liquid chromatography combined with mass spectrometry for 13C isotopic analysis in life science research

“…δ 13 C) around 0.5‰ by flow injection analysis mode (FIA, meaning injection without any LC column as dropwise or “discrete” analysis) and 1‰ by LC for amounts greater than 50 µg (Caimi & Brenna, 1993). In 1995, the sensitivity of the interface was improved by more than two orders of magnitude by changing the coating process as well as other parameters (Caimi & Brenna, 1995). A pneumatic aerosol spray was installed to atomize the liquid into an aerosol cone which was then coated onto the wire.…”

Ultrahigh Efficiency Moving Wire Combustion Interface for Online Coupling of High-Performance Liquid Chromatography (HPLC)

“…This represents a 30x efficiency increase and 8x maximum wire loading compared to the spray transfer technique used in earlier moving wire interfaces. 6 …”

“…4,5 In 1995, Caimi and Brenna published the description of a “liquid chromatography/combustion isotope ratio mass spectrometry” (LC/C-IRMS) MWI 6 . This system allowed on-line measurement of the 13 C/ 12 C ratios in LC peaks with an isotopic precision of around 1‰ for samples greater than 1 μg.…”

Recent progress in stable isotope methods for assessing vitamin metabolism

“…The coupling of liquid chromatography with IRMS is an even newer development, which despite an early report of its utility [8] has not been applied to micronutrient work. However, the marriage of HPLC with molecular mass spectrometry has been more widely employed (Table 1).…”