Improving quantitative measurements for the evaporative light scattering detector

A study was undertaken to evaluate a generic calibration routine for the evaporative light scattering detector (ELSD). The calibration routine was designed for use with gradient HPLC-ELSD in order to adjust for the effects of the non-linear response curve and the variation in response with mobile phase composition. A single calibrant was employed with an automated injection protocol to enable rapid capture of the calibration information. The study assessed the validity of the calibration method and the suitability of the calibrant for the quantitation and purity estimation of a series of structurally unrelated compounds. The calibration routine was demonstrated to improve the quality of quantitative estimates and purity estimates given by the gradient HPLC-ELSD. The average error in quantitation for the series of materials was 8.3%

Gas chromatography coupled-to Fourier transform orbitrap mass spectrometer for enantioselective amino acid analyses: Application to pre-cometary organic analog

International audienceGas chromatography (GC) is a separation technique commonly developed for targeted in situ analyses in planetary space missions. It is coupled with low-resolution mass spectrometry to obtain additional structural information and allow compound identification. However, ground-based analyses of extraterrestrial samples have shown the presence of large molecular diversities. For future targeted in situ analyses, it is therefore essential to develop new technologies. High resolution mass spectrometry (HRMS) is currently being spatialized using FT-orbitrap-MS technology. In this contribution, the coupling of gas chromatography with FT-orbitrap-MS is studied for targeted amino acid analyses. The method for enantioselective separation of amino acids was optimized on a standard mixture comprising 47 amino acid enantiomers. Different ionization modes were optimized, chemical ionization with three different reactive gases (NH 3 , CH 4 and NH 3 /CH 4) and electron impact ionization at different electron energies. Single ion and full scan monitoring modes were compared, and detection and quantification limits were estimated by internal calibration under the optimized conditions. The GC-FT-orbitrap-MS demonstrated its ability to separate 47 amino acid enantiomers with minimal co-elution. Furthermore, due to the high mass resolution and accuracy of FT-orbitrap-MS, with mass extraction, the S/N is close to zero, allowing average LOD values of 10⁻ 7 M, orders of magnitude lower than conventional GC-MS techniques. Finally, these conditions were tested for enantioselective analysis of amino acids on an analog of a pre-cometary organic material showing similarities to that of extraterrestrial materials