Abstract
In this study, the thermal desorption-cryofocusing-gas chromatographic(TD-C-GC) method was developed for determination of volatile organic compounds(VOCs) in ambient air and was applied at the municipal solid waste landfill sites. On-column cryofocusing was possible only with a 100 ml dewars bottle in TD-C-GC method with a stainless steel column. However, high operating pressure was needed for purging VOCs from the absorbent trap, which was able to solve by pressure programming with a electric pressure controller. By using both pressure and temperature programming brought increasing of resolution power in on-column cryofocusing method, but the high pressure caused a leakage of sample tube with repeated use. A loop cryofocusing devise was also developed and compared with the direct on-column method. In loop cryofocusing method, VOCs were concentrated on a 0.8mm i.d. loop which is located between the injector and separation column by using liquid nitrogen. In order to purge VOCs from the absorbent trap, only 0.4 psi of pressure was need in the loop cryofocusing method. Dual detection system was applied for the analysis of VOCs; a FID was used for hydrocarbons and a FPD was used for sulfur-containing compounds. Qualitative analysis was done by on-column cryofocusing GC-MS system. Among the large number of VOCs, toluene was the most abundant. Hydrogen sulfide, dimethyl sulfide, carbon disulfide, dimethyl disulfide and methyl propyl disulfide were detected at landfill site by FPD.
본 연구는 ppb와 ppt 정도의 농도 수준으로 존재하고 있는 대기 중 휘발성 유기화합물을 분석하기 위해 열탈착-저온농축-GC/FID/FPD를 개발하였다. 그리고 고체흡착제가 충진된 흡착관과 자체 제작한 휴대용 가스채취기를 사용하여 강원도 춘천지역에 위치한 근화동과 혈동리 생활폐기물 매립장에서 배출되는 VOCs를 채취하였다. 저온농축방법으로는 분석컬럼을 직접 저온 농축하는 on-column 저온 농축장치와 0.8mm loop를 이용한 저온농축장치를 서로 비교 검토해 보았다. On-column 저온농축법은 loop에 비해 분리능은 좋으나 흡착관에 채취한 시료를 저온농축할 때 요구되는 50 psi의 높은 탈착압력으로 인해 흡착관의 SwageLok fitting이 마모되어 가스가 새는 문제점이 발생하였다. 이에 반해 탈착압력을 낮추고 탈착유량을 늘리기 위해 설계한 loop 경우에는 탈착압력이 0.4 psi로 on-column에 비해 매우 낮아 가스가 새는 것을 방지할 수 있었다. 열탈착-저온농축-GC/FID/FPD로 분석한 근화동과 혈동리 생활폐기물 매립장에서 검출된 물질로는 toluene, xylene, ethylbenzene등 탄화수소류와 악취물인 styrene, limonene, dimethyl disulfide 등이 검출되었다. 그리고 매립지에서 방출되는 VOCs는 매립되는 폐기물의 조성과 매립기간에 따라 다르게 나타났다. 검출된 화합물은 저온농축-GC/MS를 이용하여 확인하였다.
