An aqueous solution of phosphoric acid was used as a selective stationary liquid phase for the separation of volatile fatty acids under conditions of steam chromatography. Organic acids C2--C s are etuted from the column as symmetric peaks, and the order of their elution is reverse to that observed commonly on other phases.Key words: selective stationary liquid phase: aqueous solution of phosphoric acid as stationary liqt, id phase; gas chromatography of fatty acids C2--Cs; steam chromatography.Separation of fatty acids is an important analytical task. Compounds of this type are characterized by a high polarity and adsorption capability, which makes their chromatographic determination difficult. Acids from formic to dodecanoic have been first separated as early as in 1952 in the first work on gas liquid chromatography. I A nonpolar phase along with stearic acid were deposited on a solid support to obtain symmetric peaks of acids. The use of nonpolar Apiezon L at high temperature (276 ~ made it possible to separate high-boilng acids CI2_18. 2 However, the chromatographic zones were uonsymmetric. A substantially better separation of acids C4_22 was obtained on pentaerythritol with addition of phosphoric acid (2% of the weight of the solid support)) Further, instead of direct determination of lower acids, in the majority of cases, they were analyzed in the form of esters, "t on the phases containing nonvolatile organic or inorganic acids (modifying agents) s.n, or on the phases with high polarity (for example, Nukol7).The purpose of the present work is to search for and study superselective phases for separation of volatile organic acids using a zlew approach suggested previously s which is based on the use of aqueous solutions of inorganic salts (selective under conditions of steam chromatography) as the stationary liquid phase (SLP). 9,t~ Unlike the studies mentioned, t-7 in the present work, an aqueous solution of phosphoric acid was used as SLP, and the separation of organic acids was studied on this phase.
ExperimentalThe studies were performed on a chromatograph with two independent thermostats (for a steam generator and for columns) using a procedure described previously. 9 Steel columns 2 m• mm were used, and SLP (H3PO a (87%)) was deposited on a Chmmaton solid support in amounts of 15% and 20% of the weight of the support. The rate of a carrier gas (water vapor) was 30 mL rain -I.
