ENGINEERING FOR RURAL DEVELOPMENT Jelgava, 20.-22.05.2015. 313 DETERMINATION OF N-BUTANOL AND ISOBUTANOL IN GASOLINE USING GAS CHROMATOGRAPHY (GC-FID) Vladimir Honig, Jan Taborsky, Zdenek Linhart Czech University of Life Sciences Prague honig@af.czu.cz Abstract. The paper is focused on the identification of laboratory quantities of n-butanol and isobutanol by gas chromatography GC-FID. Gas chromatography (GC) is a type of separation method. It is based on separation of components contained in the test sample that can be converted into the gas phase without decomposition. The process of separation of substances takes place in the gas chromatograph column. The mobile phase is always a gas which is in contact with the stationary phase. This assessment is also based on the application of n-butanol and isobutanol as high-percentage blends for possible future use. For laboratory analysis various combinations of fuels were collected containing gasoline with always one of the alcohols or with both together. The result is a chromatographic record, which is characteristic for each petroleum fraction. Using the chromatogram can clearly identify the presence of alcohol, which is necessary to ensure and check the prescribed amount of alcohol in the fuel. Gas chromatography can thus supplement the results of the evaluation of standard fuel or narrow selection of test parameters. The proposed method is an alternative to commonly used multidimensional chromatography. Keywords: n-butanol, isobutanol, GC-FID, gasoline, retention time. Introduction Recent fuels for any engine are complex blends of fuel ingredients. Some parts of blend are a product of crude oil distillation. Other products are produced by hydrocracking, catalytic cracking and by pyrolysis of vacuum distillates and heavy residues of distillation. Paraffins, olefins and aromates from crude oil compose resulting in fuel. Further, non-crude oil additives are composed of oxygen matters and methylesters in fuels. Therefore, it is not possible to examine fuel without examination of its parts. Also for the blending procedure and development of new fuel products an assessment of quality of properties and quantity of fuel parts is needed [1]. Traditionally, gas chromatography (CG) of gasoline is used for assessment of groups of hydrocarbons and additives, which are composed of oxygen substances. Multidimensional chromatography is the most precise method recently. Assessment of liquid petroleum products for automotive-motors is done according to the standard EN ISO 14517. Generally, chromatography is a physical-chemical method dividing liquid and gaseous blends according to different affinity of parts of blend towards mobile and stationary phases [2]. During the separation process molecules are repeatedly transported to the stationary phase and back to the mobile phase [3]. The mobile phase penetrates the stationary phase of blend separating its parts. This washing out is the principle of chromatography. Released parts of blend are transported in the direction of streaming mobile phase. The period until the stationary phase is keeping molecule of substance on its surface is proportionate with the strength of interaction between the substance and the stationary phase. Substances released from the stationary phase are measured on column output. Generally, the stronger interaction the later release of the substance from the stationary phase [4]. Gasoline sample is injected into automatically managed system of six chromatographic columns. Depending on number of carbon atoms in molecule of each group of specific hydrocarbons separation occurs being detected by a flame-ionisation detector (FID). Groups of n-alkanes, cycloalkanes, olefins, cycloolefins, aromatics and oxydated substances having from 3 to 10 carbon atoms are separated from gasoline at the end. Hydrocarbons with number of atoms above 10 are separated as saturated aromatic hydrocarbons [5]. Bioethanol (or as E85) is commonly and commercially used as gasoline additive. Use of biobutanol is not scheduled yet, although it has characteristics and especially because it is not hygroscopic. Biobutanol is preferable for replacement of bioethanol. Biobutanol can exist in the form of n-butanol, and also in the form of isobutanol. This paper works with the variant of adding isobutanol to its determination in gasolines and in blends with n-butanol. In the event of putting biobutanol to the fuel market it will also be needed to monitor compliance with the statutory limits.