キャピラリーカラムを用いたGC/MSによる豚糞から発生する硫化水素，メチルメルカプタン，トリメチルァミンおよび低級脂肪酸の分析

摘要

Malodorous substances such as hydrogen sulfide (H_2S), methyl mercaptan (MM), trimethylamine (TMA), and low molecular weight fatty acids (LMFAs) are released from pig's feces. A packed column was used to separate these substances from the feces by gas chromatography (GC). Furthermore, FPD was used to detect H2S and MM, and FID was used to detect TMA and LMFAs. However, the peaks of these target substances were inclined to be overlapped by those of other substances present in the feces. This is because, the packed column has low peak-separating ability, and FPD and FID have low detector resolution. Analytical methods for the detection of malodorous substances using a capillary column and a MS detector that have high peak-separating ability and high detector resolution were developed to resolve the abovementioned problems. The cold-trap method with liquid argon was used to concentrate H2S, MM, and TMA before GC/MS analysis. Acetone absorption of LMFAs followed by dehydration and concentration was performed before GC/MS analysis. The quantitative levels obtained for the abovementioned substances were considered to be below the standard limit for a pigsty. MM and TMA were detected in a model experiment conducted to vaporize malodorous substances from an untreated pig's feces under a neutral pH condition, however, H_2S and LMFAs, which are acidic substances, were not detected. Furthermore, H_2S and LMFAs were detected when the pig's feces was acidified with phosphoric acid. These results demonstrated that the methods used in this study are useful for the analysis and research of odorous substances.%豚糞からは，硫化水素（H_2S)ゃメチルメルカブタン（MM),トリメチルァミン（TMA)および低級脂肪酸類（LMFAs)といった悪臭物質が放出される.従来，これらの悪臭物質のガスクロマトダフィーによる分離にはパックドカラムが使用されてきた.また，H_2SとMMの検出にはFPDが利用され，TMAとLMFAsの検出にはFIDが利用されてきた.しかし，パックドカラムはピーク分離能が低く， FPDやFIDは検出器としての分解能が低いため，低濃度の悪臭物質の測定では妨害ピークの影響を受け易かった.以上の問題を解決するため，本研究では，ピーク分離能が高いキヤビラリーカラムと検出器としての分解能が高いMS検出器を用いる悪臭物質分析法を開発した.H_2S, MMおよびTMAは液体アルゴンで低温濃縮後，GC/MSで測定した.また，LMFAsは，アセトン吸収後，脱水濃縮しGC/MSで測定した.定量下限値は，いずれの悪臭物質に対しても豚小屋の敷地境界基準値以下になることが分かつた.pH中性の無処理の豚翼から悪臭物質を発生させたモデル実験では，MMとTMAは検出されたが，酸性物質であるH_2SとLMFAsは検出されなかった.ところが，豚糞をリン酸で酸性にしたところH_2SとLMFAsも検出されるようになった.以上の検討から，悪臭物質に関する分析および調査研究への本分析法の有用性が示された.