การใช้ค่าเอนทัลปีของการละลายในการวิเคราะห์เอกลักษณ์สารในแก๊สโครมาโตกราฟี

Enthalpy of Solution as an Aid in Gas Chromatographic Identification

Name: อัญชนารถ ตัญจรูญ

Organization : มหาวิทยาลัยเทคโนโลยีพระจอมเกล้าธนบุรี

keyword: Carbon number

; Hydrocarbons

; แก๊สโครมาโตกราฟี

; กรดไขมันเมทิลเอสเตอร์

; กรดไขมันไฮดรอกซีเมทิลเอสเตอร์

Abstract: Gas chromatographic identification of organic compounds can be accomplished byseveral methods. In this study, enthalpy of solution (AH’) was preselected but it was foundthat the AH” was a constant of a molecule rather than a specific functional group, Thus,identification of an organic compound with &-I0 would be very complicated, Purther analysisof the experimental data, a linear relationship between retention time ($), carbon number (N)and column temperature (T) was established as described in equation (1), a singlemathematical equation:ln Y - toIwhere to is retention time of unretained molecules. This equation can be used toestimate retention time of a known compound as well as carbon number of an unlmown atvarious temperatures. The 4 constants, a, b, c and d were obtained by injections of fatty acidmethyl esters, hydroxy fatty acid methyl esters, fatty alcohols or hydrocarbons (the range ofcarbon numbers about 12-24 carbon atoms) into an OMEGAWAX and an SP 2330 cohmmsunder isobaric and isotheimal(l40-210 degree centigrade) conditions.The above equation would help facilitate gas chromatographic identification ofunknowns of different functional groups. Also, at constant N, equation (1) is reduced to-Van’tHof