超聲波有機(jī)溶劑萃取法和改進(jìn)的Bligh-Dyer法提取甘油二烷基甘油四醚類化合物效果對(duì)比

王歡業(yè)，劉衛(wèi)國(guó),，張傳倫

1. 中國(guó)科學(xué)院地球環(huán)境研究所 黃土與第四紀(jì)地質(zhì)國(guó)家重點(diǎn)實(shí)驗(yàn)室，西安710061

2. 西安交通大學(xué) 人居環(huán)境與建筑工程學(xué)院，西安710049

3. 同濟(jì)大學(xué) 海洋地質(zhì)國(guó)家重點(diǎn)實(shí)驗(yàn)室，上海200092

超聲波有機(jī)溶劑萃取法和改進(jìn)的Bligh-Dyer法提取甘油二烷基甘油四醚類化合物效果對(duì)比

王歡業(yè)1，劉衛(wèi)國(guó)1,2，張傳倫3

1. 中國(guó)科學(xué)院地球環(huán)境研究所 黃土與第四紀(jì)地質(zhì)國(guó)家重點(diǎn)實(shí)驗(yàn)室，西安710061

2. 西安交通大學(xué) 人居環(huán)境與建筑工程學(xué)院，西安710049

3. 同濟(jì)大學(xué) 海洋地質(zhì)國(guó)家重點(diǎn)實(shí)驗(yàn)室，上海200092

由古菌和細(xì)菌產(chǎn)生的甘油二烷基甘油四醚類化合物（GDGTs）是微生物學(xué)和古環(huán)境研究中的一類重要的生物標(biāo)志化合物。有機(jī)溶劑萃取法和改進(jìn)的Bligh-Dyer法（簡(jiǎn)稱BD法）是兩種常用的提取環(huán)境樣品中GDGTs的方法，然而目前對(duì)這兩種方法提取效果的對(duì)比研究還比較少。本研究分別采用超聲波有機(jī)溶劑萃取法和BD法對(duì)兩個(gè)土壤樣品和兩個(gè)湖泊沉積物樣品的GDGTs進(jìn)行了提取。對(duì)比分析表明，超聲波有機(jī)溶劑萃取法提取出的核心脂形式的GDGTs（C-GDGTs）含量較高而BD法通常能提取出更多的完整極性膜脂形式的GDGTs（IP-GDGTs）。另外，兩種方法得到的C-GDGTs中TEX86、MBT和CBT指標(biāo)基本相同，但BD法提取的C-GDGTs的BIT值稍微偏高。這些結(jié)果將為土壤和湖泊沉積物樣品GDGTs提取方法的選擇以及不同研究間各指標(biāo)的對(duì)比提供一定的依據(jù)。

甘油二烷基甘油四醚類化合物；超聲波有機(jī)溶劑萃取法；Bligh-Dyer法；土壤；湖泊沉積物

甘油二烷基甘油四醚類化合物（GDGTs，glycerol dialkyl glycerol tetraethers）是新興的有機(jī)生物標(biāo)志物，它們廣泛分布于土壤、泥炭、海洋、湖泊等各種環(huán)境中（Schouten et al，2013）。通常所說的GDGTs是以核心脂（Core lipids）形式存在的GDGTs，即C-GDGTs，其基本結(jié)構(gòu)包括兩個(gè)烷基長(zhǎng)鏈和兩個(gè)甘油分子，烷基長(zhǎng)鏈末端通過醚鍵與甘油結(jié)合形成閉合雙鏈環(huán)狀大分子（Langworthy，1977；De Rosa and Gambacorta，1988；Schouten et al，2013）。目前，研究較多的GDGTs主要包括類異戊二烯（Isoprenoid）GDGTs和支鏈（Branched）GDGTs兩大類，可分別簡(jiǎn)稱為iGDGTs和bGDGTs（圖1）。由于GDGTs廣泛存在于各種環(huán)境中，且其分布對(duì)環(huán)境參數(shù)比較敏感，前人提出了一系列基于GDGTs的指標(biāo)，如：重建水體古溫度的TEX86指標(biāo)（Schouten et al，2002）、重建土壤/大氣溫度的MBT/CBT指標(biāo)（Weijers et al，2007）、重建土壤pH的CBT指標(biāo)（Weijers et al，2007），以及重建陸源有機(jī)質(zhì)輸入的BIT指標(biāo)（Hopmans et al，2004）等。這些指標(biāo)在海洋和陸地古氣候重建中發(fā)揮了非常重要的作用（王歡業(yè)等，2011；Schouten et al，2013）。

圖1 本文討論的主要GDGTs的結(jié)構(gòu)圖Fig.1 Chemical structures of GDGTs discussed in the text

在活體細(xì)胞中，磷酸、醣基或葡萄糖醛酸等組成的極性頭基團(tuán)會(huì)通過醚鍵鍵合在C-GDGTs兩端的甘油基團(tuán)上。這樣，GDGTs是以完整極性膜脂（Intact polar lipids，簡(jiǎn)稱IPLs）的形式存在的（Sturt et al，2004；Koga and Morii，2005；Lipp et al，2008；Pitcher et al，2009；Liu et al，2010；姚鵬和于志剛，2010；Peterse et al，2011；曹鵬等，2012），被稱作intact polar GDGTs，即IPGDGTs。隨著細(xì)胞的凋亡降解，IP-GDGTs會(huì)逐漸丟失極性頭基團(tuán)轉(zhuǎn)化成C-GDGTs。因此，在有機(jī)地球化學(xué)研究和微生物學(xué)研究中IP-GDGTs常被認(rèn)為來自現(xiàn)存活體細(xì)胞或者剛剛死亡的微生物（Lipp et al，2008；Lipp and Hinrichs，2009；Pitcher et al，2009；Liu et al，2011；Tierney et al，2012）。但是需要注意的是，也有一些研究表明某些IP-GDGTs在環(huán)境中可以保存很長(zhǎng)時(shí)間，因而可能并非所有的IP-GDGTs都是原位產(chǎn)生的（Schouten et al，2010，2012）。

多種提取方法均可用來提取環(huán)境樣品中的GDGTs（Huguet et al，2010）。其中，超聲波有機(jī)溶劑萃取法和改進(jìn)的Bligh-Dyer（Bligh and Dyer，1959）提取法（本文簡(jiǎn)稱為BD法）是兩種常用的方法（Hopmans et al，2004；Sturt et al，2004；Lipp and Hinrichs，2009；Liu et al，2011；Jia et al，2013；Wu et al，2013；Yang et al，2014；Dong et al，2015；Xing et al，2015），尤其是在同時(shí)分析C-GDGTs與IP-GDGTs 的研究中（Pitcher et al，2009，2011；Wei et al，2011；Ayari et al，2013；Liu et al，2013；Jia et al，2014；Lengger et al，2014）。為便于不同研究之間結(jié)果的對(duì)比，有必要對(duì)兩種方法提取GDGTs產(chǎn)量和指標(biāo)的可能差異進(jìn)行有效評(píng)估。目前關(guān)于兩種方法對(duì)GDGTs提取效果的對(duì)比研究還很少（Huguet et al，2010；Zhang et al，2012）。Huguet et al（2010）調(diào)查了多種提取方法對(duì)于古菌培養(yǎng)物、美國(guó)Hood Canal峽灣水體懸浮物和沉積物以及俄勒岡州土壤中iGDGTs的萃取效率，但未評(píng)估不同方法對(duì)GDGTs指標(biāo)的影響。Zhang et al（2012）對(duì)比了超聲波有機(jī)溶劑萃取法和BD法對(duì)珠江下游和珠江口水體懸浮物和沉積物bGDGTs的提取效率和GDGTs分布的影響，但未報(bào)道iGDGTs的提取效率以及TEX86指標(biāo)的差異。另外，兩項(xiàng)研究均沒有涉及湖泊沉積物樣品。本研究中，以青海湖和柴達(dá)木盆地地區(qū)兩個(gè)湖泊沉積物樣品和兩個(gè)土壤樣品為研究對(duì)象，對(duì)比超聲波有機(jī)溶劑萃取法和BD法提取GDGTs對(duì)其含量和分布（指標(biāo)）的可能影響。

1 材料與方法

本實(shí)驗(yàn)的樣品采自青海省的青海湖和柴達(dá)木盆地地區(qū)。兩個(gè)土壤樣品（表層0 — 5 cm）TR1和TR2分別采自橡皮山和茶卡鹽湖周邊。兩個(gè)湖泊沉積物樣品CJW1和CJW2分別采自青海湖和托素湖。其中，CJW1為湖中心沉積物（3 — 5 cm），CJW2為湖邊沉積物（0 — 5 cm）。樣品在野外保存在液氮或干冰中運(yùn)回實(shí)驗(yàn)室。

冷凍干燥并研磨后的樣品分別用超聲波有機(jī)溶劑萃取法和BD法抽提。超聲波有機(jī)溶劑萃取法：稱取5 g樣品向其中加入一定量的C46內(nèi)標(biāo)，依次用甲醇、二氯甲烷/甲醇（1:1）、二氯甲烷、二氯甲烷/甲醇（1:1）和甲醇超聲震蕩15 min萃取其中的有機(jī)質(zhì)，5次得到的總提取液在水浴中用氮?dú)獯蹈?。BD法：用體積比2:1:0.8的甲醇/二氯甲烷/磷酸鹽緩沖溶液（pH 7.4）超聲震蕩萃取樣品（5 g，并提前加有一定量的C46內(nèi)標(biāo)）3次，每次15 min。合并三次所得萃取液加入一定量的二氯甲烷和磷酸鹽緩沖液調(diào)整三者比例為1:1:0.9。此時(shí)溶液出現(xiàn)較好分層，將底部的有機(jī)相轉(zhuǎn)移到40 mL玻璃瓶中，殘余相用二氯甲烷再萃取兩次，均收集到40 mL玻璃瓶里。將幾次收集的總萃取液在水浴中用氮?dú)獯蹈伞?/p>

用二氯甲烷重新溶解兩種方法提取的各樣品總提取物并平分為兩份（分別記為F1和F2組分）。其中F1組分吹干后用99:1的正己烷/異丙醇溶解并過0.45 μm濾膜。F2組分按照Wei et al（2011）的方法進(jìn)行酸水解，隨后萃取得到水解后的有機(jī)組分，該組分吹干后也用99:1的正己烷/異丙醇溶解并過濾以備GDGTs測(cè)試。

樣品的GDGTs測(cè)試所用儀器為高效液相色譜-大氣壓化學(xué)電離-質(zhì)譜（HPLC-APCI-MS，HPLC型號(hào)為Agilent 1200，MS型號(hào)為6460三重四級(jí)桿）。分析方法修改自Hopmans et al（2000）和Schouten et al（2007）。進(jìn)樣量為2 μL。所用液相色譜柱為奧泰Prevail氰基柱（150 mm × 2.1 mm，3 μm）。洗脫流動(dòng)相程序?yàn)椋? — 5 min，99:1正己烷/異丙醇；5 — 45 min，異丙醇比例線性升至1.8%，整個(gè)過程流動(dòng)相流速為0.2 mL · min-1。每分析完一個(gè)樣品，以 10%的異丙醇沖洗色譜柱15 min。質(zhì)譜方法采用選擇離子掃描（SIM）模式檢測(cè)GDGTs質(zhì)子化后特定質(zhì)荷比的離子。通過對(duì)各GDGTs的[M+H]+離子峰面積進(jìn)行積分并對(duì)比與C46內(nèi)標(biāo)[M+H]+離子峰面積的比值，可以對(duì)樣品中GDGTs的含量進(jìn)行定量（假設(shè)iGDGTs和bGDGTs均與C46內(nèi)標(biāo)具有相同的響應(yīng)因子）。

F1組分中檢測(cè)得到的GDGTs即為樣品中的C-GDGTs。F2組分中檢測(cè)得到的GDGTs為樣品中IP-GDGTs酸解后生成的C-GDGTs加上樣品中原始的C-GDGTs。進(jìn)而，根據(jù)差減法可以計(jì)算IPGDGTs酸解生成的C-GDGTs的含量（Huguet et al，2010；Zhang et al，2012）。為與C-GDGTs區(qū)分，本文仍將由IP-GDGTs酸解生成的C-GDGTs稱作PL-GDGTs。

表示bGDGTs甲基化指數(shù)的MBT指標(biāo)和環(huán)化指數(shù)的CBT 指標(biāo)按照 Weijers et al（2007）計(jì)算如下：

2 結(jié)果與討論

2.1 GDGTs提取效率

為便于比較超聲波有機(jī)溶劑萃取法與BD法對(duì)樣品GDGTs的提取效率，用RCS/BD來表示兩種方法提取GDGTs含量之比。對(duì)本研究中的兩個(gè)土壤樣品和兩個(gè)湖泊沉積物樣品，C-iGDGTs的RCS/BD均＞1.0（圖2），平均為1.3，表明超聲波有機(jī)溶劑萃取法提取C-iGDGTs的效率較高。Huguet et al（2010）對(duì)峽灣水體懸浮物、沉積物以及土壤的研究結(jié)果也表明超聲波有機(jī)溶劑萃取法常能得到較多的C-iGDGTs。對(duì)于IP-iGDGTs，4個(gè)樣品的RCS/BD均＜1.0，平均為0.6，表明BD法提取IP-iGDGTs的效率較高。另外，結(jié)果顯示，兩種方法對(duì)bGDGTs的提取效果與對(duì)iGDGTs的提取效果類似，C-bGDGTs的RCS/BD均≥1.0（圖2），平均為1.1，而IP-bGDGTs的RCS/BD均≤1.0，平均為0.7。以上結(jié)果表明，超聲波有機(jī)溶劑萃取法可以提取出較多的C-GDGTs而BD法通常能提取出更多的IPGDGTs。

圖2 GDGTs各組分用超聲波有機(jī)溶劑萃取法與BD法提取量比值（RCS/BD）Fig.2 The relative yield of GDGTs extracted by ultrasound-assisted organic solvent extraction vs. Bligh-Dyer extraction (RCS/BD)

與C-GDGTs相比，IP-GDGTs帶有一定數(shù)量的極性頭基團(tuán)，這導(dǎo)致了IP-GDGTs極性較強(qiáng)。由于超聲波有機(jī)溶劑萃取法所用的有機(jī)溶劑極性比BD法所用的甲醇/二氯甲烷/磷酸鹽緩沖溶液極性要弱，根據(jù)相似相溶原理，超聲波有機(jī)溶劑萃取法會(huì)對(duì)C-GDGTs有較高的提取效率，而BD法更適合提取極性較強(qiáng)的有機(jī)化合物。因此，對(duì)于只關(guān)心C-GDGTs的研究可以選用超聲波有機(jī)溶劑萃取法，而對(duì)于注重IP-GDGTs提取效率的研究，應(yīng)將BD法作為首選方法。但是需要注意的是，對(duì)于本實(shí)驗(yàn)選取的樣品，兩種方法提取的GDGTs含量并沒有數(shù)量級(jí)上的差別。事實(shí)上，相對(duì)于GDGTs的提取效率， GDGTs的研究往往更關(guān)心的是GDGTs指標(biāo)。因此，需要進(jìn)一步對(duì)比超聲波有機(jī)溶劑萃取法與BD法提取的GDGTs分布的差異。

2.2 GDGTs分布

首先，對(duì)比了C-GDGTs的分布（圖3）。對(duì)于本研究的4個(gè)樣品，兩種方法提取C-GDGTs的TEX86值非常一致，其超聲波有機(jī)溶劑萃取法與BD法的差值（即超聲波有機(jī)溶劑萃取法TEX86-BD法TEX86）分別為0.00、-0.01、-0.01、0.01，平均值為-0.002，基本在儀器的分析誤差之內(nèi)（±0.01或更大）（Yang et al，2011；Wang et al，2012）。這些結(jié)果表明對(duì)湖泊沉積物和土壤樣品采用兩種不同的提取方法可能不會(huì)影響對(duì)C-iGDGTs的TEX86的計(jì)算。另外，兩種方法得到的表示C-bGDGTs分布的MBT指標(biāo)和CBT指標(biāo)也比較接近，其差值分別為0.00、0.01、-0.01、0.00和-0.01、0.02、-0.01、-0.02，平均值分別為0.000和-0.008，表明對(duì)湖泊沉積物和土壤樣品采用兩種不同的提取方法可能也不會(huì)影響對(duì)C-bGDGTs的MBT和CBT的計(jì)算。Zhang et al（2012）對(duì)比這兩種方法提取珠江下游和珠江口沉積物bGDGTs的結(jié)果也顯示，超聲波有機(jī)溶劑萃取法和BD法得到的大部分樣品的C-bGDGTs的MBT和CBT并沒有差異。

圖3 超聲波有機(jī)溶劑萃取法（圓圈）與BD法（三角）提取的C-GDGTs各指標(biāo)對(duì)比Fig.3 Comparison of C-GDGT indices extracted using ultrasound-assisted organic solvent extraction (circles) and Bligh-Dyer extraction (triangles)

兩種方法提取C-GDGTs的BIT值差別也較?。▓D3），4個(gè)樣品的差值分別為-0.04、0.00、-0.05、-0.04，平均值為-0.031。但是，超聲波有機(jī)溶劑萃取法得到的C-GDGTs的BIT似乎比BD法得到的值系統(tǒng)偏低。根據(jù)C-bGDGTs在色譜圖中比C-iGDGTs具有更長(zhǎng)的保留時(shí)間可以推測(cè)C-bGDGTs的極性比C-iGDGTs要強(qiáng)。因此，更適合提取極性較強(qiáng)化合物的BD法對(duì)C-bGDGTs的提取效率可能比對(duì)C-iGDGTs的提取效率要高，這會(huì)導(dǎo)致BD法得到的C-GDGTs的BIT值偏高。這一推測(cè)可以進(jìn)一步通過RCS/BD的結(jié)果證實(shí)：C-bGDGTs的RCS/BD平均為1.1，小于C-iGDGTs的平均RCS/BD值（1.3）。

此外，還對(duì)比了IP-GDGTs的分布（圖4）。兩種方法提取IP-iGDGTs 組分的TEX86值較為一致，超聲波有機(jī)溶劑萃取法與BD法的差值分別為0.02、-0.04、-0.02、-0.01，平均值為-0.012。兩種方法提取IP-bGDGTs 組分的MBT和CBT具有一定差異，其差值分別為-0.01、-0.13、0.04、0.07和-0.48、0.13、0.06、0.39，平均值分別為-0.008和0.024。另外，兩種方法得到的IP-GDGTs的BIT值也具有一定差異，其差值分別為0.00、0.00、0.12、-0.04，平均值為0.018。Zhang et al（2012）對(duì)珠江下游和珠江口沉積物的研究結(jié)果也表明用兩種不同提取方法得到的IP-GDGTs的MBT、CBT和BIT值有所差異。需要指出的是，本文和Zhang et al（2012）中IP-GDGTs組分是由差減法得到的，但是該方法在計(jì)算GDGTs分布時(shí)可能誤差較大（Lengger et al，2012），尤其是樣品中IP-GDGTs相對(duì)于C-GDGTs含量較低的時(shí)候。因此，根據(jù)本文的結(jié)果，只能說兩種方法提取湖泊沉積物和土壤樣品引起的IP-GDGTs分布的差異可能不會(huì)太大，但是是否有差異或者具體有多大程度的差異仍需進(jìn)一步的確認(rèn)。

圖4 超聲波有機(jī)溶劑萃取法（圓圈）與BD法（三角）提取的IP-GDGTs各指標(biāo)對(duì)比Fig.4 Comparison of IP-GDGT indices extracted using ultrasound-assisted organic solvent extraction (circles) and Bligh-Dyer extraction (triangles)

3 結(jié)論

本研究分別采用BD法和超聲波有機(jī)溶劑萃取法提取了兩個(gè)土壤樣品和兩個(gè)湖泊沉積物樣品中的C-GDGTs和IP-GDGTs。結(jié)果顯示：（1）超聲波有機(jī)溶劑萃取法提取出的C-GDGTs含量較高而BD法通常能提取出更多的IP-GDGTs，但兩者對(duì)GDGTs的提取效率并沒有數(shù)量級(jí)上的差異。（2）兩種方法得到的C-GDGTs中TEX86、MBT和CBT指標(biāo)基本相同，但BD法得到的C-GDGTs的BIT稍微偏高。（3）兩種方法提取IP-iGDGTs組分的TEX86值比較一致，而MBT、CBT和BIT指標(biāo)具有一定差異（但不是很大）。考慮到本研究IP-GDGTs是由差減法計(jì)算的，尚無法確定兩種提取方法會(huì)導(dǎo)致IP-GDGTs分布的何種差異。

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Comparison of the ultrasound-assisted organic solvent extraction and modified Bligh-Dyer extraction for the analysis of glycerol dialkyl glycerol tetraethers from environmental samples

WANG Huanye1, LIU Weiguo1,2, ZHANG Chuanlun3
1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China
2. School of Human Settlement and Civil Engineering, Xi’an Jiaotong University, Xi’an 710049, China
3. State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China

Background, aim, and scope The microbial glycerol dialkyl glycerol tetraethers (GDGTs) are increasingly popular in the fi eld of organic geochemistry. These high-molecular-weight compounds produced by archaea and bacteria are sensitive to environmental variables, and therefore they contain important information on environmental parameters in paleoclimatic studies. Two extraction method, the ultrasonic-assisted organic solvent extraction and the modified Bligh-Dyer extraction (the BD extraction), are commonly applied forextracting GDGTs from environment samples. To date, however, only a few studies have compared the effect of the two extraction methods on the yield and distribution of GDGTs. In this study, we aimed to systematically compare the effect of the ultrasonic-assisted organic solvent extraction and the BD extraction on GDGTs extracted from sediment and soil samples, and to further provide some basis for the choice of extraction methods for GDGTs in soils and lake sediments, as well as for the comparison of GDGT distributions between different studies. Materials and methods We extracted GDGTs by the ultrasonic-assisted organic solvent extraction and the BD extraction from two soil samples and two lake sediment samples collected from the Qinghai province, China. GDGTs present as both core lipids (C-GDGTs) and intact polar lipids (IP-GDGTs) were analyzed as follows: each GDGT sample was separated into two halves, with one half subjecting to hydrolysis (the hydrolyzed fraction) and the other not (the non-hydrolyzed fraction); GDGTs of each fraction was directly measured on the high performance liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry. Quantifi cation was performed by way of peak area integration of [M+H]+ions in the extracted ion chromatogram, and comparison with the internal standard. Ionization effi ciency for each GDGT was assumed identical. GDGTs in the non-hydrolyzed fraction were C-GDGTs, while the difference in yield of GDGTs between the hydrolyzed and non-hydrolyzed fractions is considered to be IP-GDGTs. Results (1) For iGDGTs, the yield of C-GDGTs using ultrasonic-assisted organic solvent extraction is higher than that using BD extraction (by 30% on average), while the yield of IP-GDGTs using ultrasonic-assisted organic solvent extraction is lower than that using BD extraction (by 40% on average). (2) For bGDGTs, the yield of C-GDGTs using ultrasonic-assisted organic solvent extraction is higher than that using BD extraction (by 10% on average), while the yield of IP-GDGTs using ultrasonic-assisted organic solvent extraction is lower than that using BD extraction (by 30% on average). (3) For C-GDGTs of the two soil samples and two lake sediment samples: the difference in TEX86values is 0.00,-0.01, -0.01 and 0.01, respectively; the difference in MBT values is 0.00, 0.01, -0.01 and 0.00, respectively; the difference in CBT values is -0.01, 0.02, -0.01 and -0.02, respectively. All these values are within the analytical error. However, the BIT values are systematically higher for the BD extraction (ca. 0.03 higher than those for the ultrasonic-assisted organic solvent extraction). Discussion Compared with C-GDGTs, the polarity of IPGDGTs is much stronger due to its polar headgroups. On the other hand, the polarity of the solvent used in the BD extraction (MeOH/dichloromethane/phosphate buffer) is much stronger than the organic solvent (MeOH/ dichloromethane) used in ultrasonic-assisted organic solvent extraction. According to the “Like Dissolves Like Theory”, the ultrasonic-assisted organic solvent extraction can extract more C-GDGTs while the BD extraction can extract more IP-GDGTs. For the TEX86index, it is calculated based on similar GDGTs with similar polarity, and therefore, the values of different methods showed little difference. For the MBT and CBT indices, the values of different methods also showed little difference, similar to the case for the TEX86index. For the BIT index, however, it is calculated based on two groups of GDGTs, i.e., iGDGTs and bGDGTs, and the polarity of bGDGTs is stronger than iGDGTs. Consequently, the BIT index should be higher if samples are extracted using a BD extraction. Conclusions The ultrasonic-assisted organic solvent extraction showed higher extraction effi ciency for C-GDGTs, while the BD extraction is more effective for IP-GDGTs. Moreover, the TEX86, MBT and CBT indices for C-GDGTs are not signifi cantly affected by method difference, while the BIT index of C-GDGTs is slightly higher using BD extraction. Recommendations and perspectives For C-GDGT investigations, the ultrasonic-assisted organic solvent extraction is the fi rst choice, while for studies concerning the yield of IP-GDGTs, the BD extraction should be used. Anyhow, the TEX86, MBT and CBT indices should not be signifi cantly biased if different extracting methods are used, and therefore, some of the GDGT results using different extracting methods might be comparable.

glycerol dialkyl glycerol tetraethers; ultrasonic-assisted organic solvent extraction; Bligh-Dyer extraction; soil; lake sediment

LIU Weiguo, E-mail: liuwg@loess.llqg.ac.cn

2016-11-15；錄用日期：2017-02-14

Received Date: 2016-11-15; Accepted Date: 2017-02-14

中國(guó)科學(xué)院“西部之光”人才培養(yǎng)引進(jìn)計(jì)劃（XAB2015B01）

Foundation Item: CAS “Light of West China” Program (XAB2015B01)

劉衛(wèi)國(guó)，E-mail: liuwg@loess.llqg.ac.cn

王歡業(yè), 劉衛(wèi)國(guó), 張傳倫, 等. 2017. 超聲波有機(jī)溶劑萃取法和改進(jìn)的Bligh-Dyer法提取甘油二烷基甘油四醚類化合物效果對(duì)比[J].地球環(huán)境學(xué)報(bào), 8(2): 176 – 184.

: Wang H Y, Liu W G, Zhang C L, et al. 2017. Comparison of the ultrasound-assisted organic solvent extraction and modifi ed Bligh-Dyer extraction for the analysis of glycerol dialkyl glycerol tetraethers from environmental samples [J]. Journal of Earth Environment, 8(2): 176 – 184.