Optimisation of pretreatment and derivatization method for analysis of organic acids by gas chromatography-mass spectrometry

Abstract

Introduction. Chromatography is the preferred method of analysis because it adequately addresses the simultaneous identification and quantification of targeted compounds. However, not all chromatographic protocols are suitable for the given task. Although the separation using this method generally targets volatile, non-polar species, the use of derivatization for polar low molecular weight species enables detection with a good resolution and sensitivity. Derivatization as and pretreatment can improve chromatographic results. The aim of our work was to develop reliable and accurate method for quantitative and qualitative analysis of organic acid, such as levulic, heptanoic, malic, lactic, glycolic, oxalic, nonanoic, maleic, succinic , stearic, citric. Materials and methods. The research was done using methodology on SHIMADZU GC-MS-QP2010 Ultra chromatography system with RXI-5ms (Restek Corporation) capillary column (30 m long, with 0.25 mm outer diameter and 0.25 μm liquid-stationary phase thickness) with a liquid stationary phase (5% diphenyl and 95% polysiloxane), as carrier gas of chromatography we used helium. Organics acids were identified by comparison with database mass spectra of compounds or analyzing ions characteristic of mass spectra. The oven temperature was programmed from 75 °C for 5 min, then 10 °C/min to 290 °C for 5 min, after 20 °C/min to 320 and held constant for 5 min. The injector temperature was 260 °C, injection volume 1 μL, injection mode split, split ratio 1:10, the ion source voltage 70eV. Mass spectra scan range of m/z 35-500 amu with mass scan time 0.2 seconds, interface temperature 280 °C. All solvents were HPLC grade. Results and discussion. In presence work we examined an effects of different derivative agents, solvents for sample dissolution and reaction solvents. The weights of samples were placed into 5 ml volumetric flasks, 3 ml (of the following solvents: water, acetonitrile, methanol, 80% methanol and 80% acetonit