四甲基氢氧化铵参与下的中空纤维微萃取结合进样口衍生化气相色谱法同时测定啤酒中6种酚酸
王晓青等
摘 要 建立了以乙酸己酯为萃取相、四甲基氢氧化铵（TMAH）为接收相的中空纤维三相液相微萃取结合进样口衍生化气相色谱法，同时测定啤酒中水杨酸、对羟基苯甲酸、肉桂酸、香草酸、对香豆酸、阿魏酸等酚酸类物质。啤酒中的酚酸被中空纤维膜壁中的乙酸己酯萃取，接着溶于纤维膜内碱性的TMAH接收相。取1 μL接收相进样，在进样口酚酸被TMAH衍生化成相应的甲酯。对影响萃取与衍生化效率的主要因素进行了优化，得到最佳条件：萃取剂为乙酸己酯，衍生化试剂和接受相为5% TMAH溶液，供给相pH=2，NaCl浓度为25%，搅拌速度为References
1 DONG Xia， LI Qi， GU GuoXian. Liquor Making， 2003， 30（6）： 63-65
董 霞， 李 崎， 顾国贤. 酿酒， 2003， 30（6）： 63-65
2 Vanbeneden N， Delvaux F， Delvaux F R. J. Chromatogr. A， 2006， 1136（2）： 237-242
3 Floridi S， Montanari L， Marconi O， Fantozzi P. J. Agr. Food Chem.， 2003， 51（6）： 1548-1554
4 Alonso García A， Cancho Grande B， Simal Gándara J. J. Chromatogr. A， 2004， 1054（12）： 175-180
5 Citová I， Sladkovsky R， Solich P. Anal. Chem. Acta， 2006， 573-574： 231-241
6 Proestos C， Sereli D， Komaitis M. Food Chem.， 2006， 95（1）： 44-52
7 Nur B A B， Ahmad M， Bahruddin S. Anal. Chem. Acta， 2012， 724： 59-66
8 TAN XiaoWang， WEI RuiPing， SONG YanXi， YI GuYang. Chinese J. Anal. Chem.， 2012， 40（9）： 1409-1414
谭小旺， 魏瑞萍， 宋燕西， 易谷洋. 分析化学， 2012， 40（9）： 1409-1414
9 Peng J F， Liu J F， Hu X L， JiangG B. J. Chromatogr. A， 2007， 1139（2）： 165-170
10 SHAO Yan， ZHANG LiJun， ZHANG ZhanEn. Chinese J. Anal. Chem.， 2011， 39（11）： 1753-1757
邵 焰， 张丽君， 张占恩. 分析化学， 2011， 39（11）： 1753-1757
11 Sun Y， Wang X Q， Huang Y L， Pan Z F， Wang L L. J. Sep. Sci.， 2013， 36（14）： 2268-2276
12 Wu J M， Lee H K. J. Anal. Chem.， 2006， 78（20）： 7292-7301
13 Sanagi M M， Miskam M， Ibrahim W A W， Hermawan D， AboulEnein H Y. J. Sep. Sci.， 2010， 33（14）： 2131-2139
Derivatization at Injection Port Following Hollow Fiber Microextraction
with Tetramethylammonium Hydroxide for Determination of
Six Phenolic Acids in Beers by Gas Chromatography
WANG XiaoQing1， HUANG YiLei1， SUN Yang2， PAN ZaiFa1， WANG LiLi*1
1（College of Chemical Engineering， Zhejiang University of Technology， Hangzhou 310014， China）
2（Zhejiang Province Institute of Metrology， Hangzhou 310013， China）
Abstract A method of derivatization at injection port following three phase hollow fiber microextraction with tetramethylammonium hydroxide （TMAH） as a dualfunction reagent， for the simultaneous determination of salicylic acid， phydroxybenzoic acid， cinnamic acid， vanillic acid， pcoumaric acid and ferulic acid in beers by gas chromatography was developed. Phenolic acids were extracted from aqueous samples to a thin layer of organic solvent （hexyl acetate） phase impregnated into the pores of the hollow fiber wall， and then back extracted to an acceptor solution （TMAH） located inside the lumen of the hollow fiber. Upon injection， the phenolic acids were derivatized to their methyl esters in the GC injection port. Several parameters related to the derivatization and extraction efficiency were optimized. The optimized conditions were as follows： hexyl acetate was used as the extraction solvent， an aqueous solution of TMAH （5% W/V） was used as the derivatization reagent and acceptor phase， the pH value of donor phase was 2.0， the concentrations of NaCl was 25% W/V， the stirring rate was 500 r/min， the extraction time was 40 min. Under the optimal conditions， the linear range of phenolic acids was 0.50-15.00 mg/L， the limits of detection were 0.05-0.18 mg/L. The proposed method was applied to the determination of the phenolic acids in beers. Vanillic acid， pcoumaric acid and ferulic acid were found in the beer samples， others were not detected. The spiked average recoveries were 90.1%-106.8% and RSD% was less than 5.9%（n=3）. The method is suitable for the determination of phenolic acids in beers.
Keywords Three phase hollow fiber microextraction； Gas chromatography； Injection port derivatization； Tetramethylammonium hydroxide； Phenolic acids
（Received 20 January 2014； accepted 7 March 2014）
This work was supported by the Analysis and Measurement Foundation of Zhejiang Province （No.2013C37067）
摘 要 建立了以乙酸己酯为萃取相、四甲基氢氧化铵（TMAH）为接收相的中空纤维三相液相微萃取结合进样口衍生化气相色谱法，同时测定啤酒中水杨酸、对羟基苯甲酸、肉桂酸、香草酸、对香豆酸、阿魏酸等酚酸类物质。啤酒中的酚酸被中空纤维膜壁中的乙酸己酯萃取，接着溶于纤维膜内碱性的TMAH接收相。取1 μL接收相进样，在进样口酚酸被TMAH衍生化成相应的甲酯。对影响萃取与衍生化效率的主要因素进行了优化，得到最佳条件：萃取剂为乙酸己酯，衍生化试剂和接受相为5% TMAH溶液，供给相pH=2，NaCl浓度为25%，搅拌速度为References
1 DONG Xia， LI Qi， GU GuoXian. Liquor Making， 2003， 30（6）： 63-65
董 霞， 李 崎， 顾国贤. 酿酒， 2003， 30（6）： 63-65
2 Vanbeneden N， Delvaux F， Delvaux F R. J. Chromatogr. A， 2006， 1136（2）： 237-242
3 Floridi S， Montanari L， Marconi O， Fantozzi P. J. Agr. Food Chem.， 2003， 51（6）： 1548-1554
4 Alonso García A， Cancho Grande B， Simal Gándara J. J. Chromatogr. A， 2004， 1054（12）： 175-180
5 Citová I， Sladkovsky R， Solich P. Anal. Chem. Acta， 2006， 573-574： 231-241
6 Proestos C， Sereli D， Komaitis M. Food Chem.， 2006， 95（1）： 44-52
7 Nur B A B， Ahmad M， Bahruddin S. Anal. Chem. Acta， 2012， 724： 59-66
8 TAN XiaoWang， WEI RuiPing， SONG YanXi， YI GuYang. Chinese J. Anal. Chem.， 2012， 40（9）： 1409-1414
谭小旺， 魏瑞萍， 宋燕西， 易谷洋. 分析化学， 2012， 40（9）： 1409-1414
9 Peng J F， Liu J F， Hu X L， JiangG B. J. Chromatogr. A， 2007， 1139（2）： 165-170
10 SHAO Yan， ZHANG LiJun， ZHANG ZhanEn. Chinese J. Anal. Chem.， 2011， 39（11）： 1753-1757
邵 焰， 张丽君， 张占恩. 分析化学， 2011， 39（11）： 1753-1757
11 Sun Y， Wang X Q， Huang Y L， Pan Z F， Wang L L. J. Sep. Sci.， 2013， 36（14）： 2268-2276
12 Wu J M， Lee H K. J. Anal. Chem.， 2006， 78（20）： 7292-7301
13 Sanagi M M， Miskam M， Ibrahim W A W， Hermawan D， AboulEnein H Y. J. Sep. Sci.， 2010， 33（14）： 2131-2139
Derivatization at Injection Port Following Hollow Fiber Microextraction
with Tetramethylammonium Hydroxide for Determination of
Six Phenolic Acids in Beers by Gas Chromatography
WANG XiaoQing1， HUANG YiLei1， SUN Yang2， PAN ZaiFa1， WANG LiLi*1
1（College of Chemical Engineering， Zhejiang University of Technology， Hangzhou 310014， China）
2（Zhejiang Province Institute of Metrology， Hangzhou 310013， China）
Abstract A method of derivatization at injection port following three phase hollow fiber microextraction with tetramethylammonium hydroxide （TMAH） as a dualfunction reagent， for the simultaneous determination of salicylic acid， phydroxybenzoic acid， cinnamic acid， vanillic acid， pcoumaric acid and ferulic acid in beers by gas chromatography was developed. Phenolic acids were extracted from aqueous samples to a thin layer of organic solvent （hexyl acetate） phase impregnated into the pores of the hollow fiber wall， and then back extracted to an acceptor solution （TMAH） located inside the lumen of the hollow fiber. Upon injection， the phenolic acids were derivatized to their methyl esters in the GC injection port. Several parameters related to the derivatization and extraction efficiency were optimized. The optimized conditions were as follows： hexyl acetate was used as the extraction solvent， an aqueous solution of TMAH （5% W/V） was used as the derivatization reagent and acceptor phase， the pH value of donor phase was 2.0， the concentrations of NaCl was 25% W/V， the stirring rate was 500 r/min， the extraction time was 40 min. Under the optimal conditions， the linear range of phenolic acids was 0.50-15.00 mg/L， the limits of detection were 0.05-0.18 mg/L. The proposed method was applied to the determination of the phenolic acids in beers. Vanillic acid， pcoumaric acid and ferulic acid were found in the beer samples， others were not detected. The spiked average recoveries were 90.1%-106.8% and RSD% was less than 5.9%（n=3）. The method is suitable for the determination of phenolic acids in beers.
Keywords Three phase hollow fiber microextraction； Gas chromatography； Injection port derivatization； Tetramethylammonium hydroxide； Phenolic acids
（Received 20 January 2014； accepted 7 March 2014）
This work was supported by the Analysis and Measurement Foundation of Zhejiang Province （No.2013C37067）
摘 要 建立了以乙酸己酯为萃取相、四甲基氢氧化铵（TMAH）为接收相的中空纤维三相液相微萃取结合进样口衍生化气相色谱法，同时测定啤酒中水杨酸、对羟基苯甲酸、肉桂酸、香草酸、对香豆酸、阿魏酸等酚酸类物质。啤酒中的酚酸被中空纤维膜壁中的乙酸己酯萃取，接着溶于纤维膜内碱性的TMAH接收相。取1 μL接收相进样，在进样口酚酸被TMAH衍生化成相应的甲酯。对影响萃取与衍生化效率的主要因素进行了优化，得到最佳条件：萃取剂为乙酸己酯，衍生化试剂和接受相为5% TMAH溶液，供给相pH=2，NaCl浓度为25%，搅拌速度为References
1 DONG Xia， LI Qi， GU GuoXian. Liquor Making， 2003， 30（6）： 63-65
董 霞， 李 崎， 顾国贤. 酿酒， 2003， 30（6）： 63-65
2 Vanbeneden N， Delvaux F， Delvaux F R. J. Chromatogr. A， 2006， 1136（2）： 237-242
3 Floridi S， Montanari L， Marconi O， Fantozzi P. J. Agr. Food Chem.， 2003， 51（6）： 1548-1554
4 Alonso García A， Cancho Grande B， Simal Gándara J. J. Chromatogr. A， 2004， 1054（12）： 175-180
5 Citová I， Sladkovsky R， Solich P. Anal. Chem. Acta， 2006， 573-574： 231-241
6 Proestos C， Sereli D， Komaitis M. Food Chem.， 2006， 95（1）： 44-52
7 Nur B A B， Ahmad M， Bahruddin S. Anal. Chem. Acta， 2012， 724： 59-66
8 TAN XiaoWang， WEI RuiPing， SONG YanXi， YI GuYang. Chinese J. Anal. Chem.， 2012， 40（9）： 1409-1414
谭小旺， 魏瑞萍， 宋燕西， 易谷洋. 分析化学， 2012， 40（9）： 1409-1414
9 Peng J F， Liu J F， Hu X L， JiangG B. J. Chromatogr. A， 2007， 1139（2）： 165-170
10 SHAO Yan， ZHANG LiJun， ZHANG ZhanEn. Chinese J. Anal. Chem.， 2011， 39（11）： 1753-1757
邵 焰， 张丽君， 张占恩. 分析化学， 2011， 39（11）： 1753-1757
11 Sun Y， Wang X Q， Huang Y L， Pan Z F， Wang L L. J. Sep. Sci.， 2013， 36（14）： 2268-2276
12 Wu J M， Lee H K. J. Anal. Chem.， 2006， 78（20）： 7292-7301
13 Sanagi M M， Miskam M， Ibrahim W A W， Hermawan D， AboulEnein H Y. J. Sep. Sci.， 2010， 33（14）： 2131-2139
Derivatization at Injection Port Following Hollow Fiber Microextraction
with Tetramethylammonium Hydroxide for Determination of
Six Phenolic Acids in Beers by Gas Chromatography
WANG XiaoQing1， HUANG YiLei1， SUN Yang2， PAN ZaiFa1， WANG LiLi*1
1（College of Chemical Engineering， Zhejiang University of Technology， Hangzhou 310014， China）
2（Zhejiang Province Institute of Metrology， Hangzhou 310013， China）
Abstract A method of derivatization at injection port following three phase hollow fiber microextraction with tetramethylammonium hydroxide （TMAH） as a dualfunction reagent， for the simultaneous determination of salicylic acid， phydroxybenzoic acid， cinnamic acid， vanillic acid， pcoumaric acid and ferulic acid in beers by gas chromatography was developed. Phenolic acids were extracted from aqueous samples to a thin layer of organic solvent （hexyl acetate） phase impregnated into the pores of the hollow fiber wall， and then back extracted to an acceptor solution （TMAH） located inside the lumen of the hollow fiber. Upon injection， the phenolic acids were derivatized to their methyl esters in the GC injection port. Several parameters related to the derivatization and extraction efficiency were optimized. The optimized conditions were as follows： hexyl acetate was used as the extraction solvent， an aqueous solution of TMAH （5% W/V） was used as the derivatization reagent and acceptor phase， the pH value of donor phase was 2.0， the concentrations of NaCl was 25% W/V， the stirring rate was 500 r/min， the extraction time was 40 min. Under the optimal conditions， the linear range of phenolic acids was 0.50-15.00 mg/L， the limits of detection were 0.05-0.18 mg/L. The proposed method was applied to the determination of the phenolic acids in beers. Vanillic acid， pcoumaric acid and ferulic acid were found in the beer samples， others were not detected. The spiked average recoveries were 90.1%-106.8% and RSD% was less than 5.9%（n=3）. The method is suitable for the determination of phenolic acids in beers.
Keywords Three phase hollow fiber microextraction； Gas chromatography； Injection port derivatization； Tetramethylammonium hydroxide； Phenolic acids
（Received 20 January 2014； accepted 7 March 2014）
This work was supported by the Analysis and Measurement Foundation of Zhejiang Province （No.2013C37067）
摘 要 建立了以乙酸己酯为萃取相、四甲基氢氧化铵（TMAH）为接收相的中空纤维三相液相微萃取结合进样口衍生化气相色谱法，同时测定啤酒中水杨酸、对羟基苯甲酸、肉桂酸、香草酸、对香豆酸、阿魏酸等酚酸类物质。啤酒中的酚酸被中空纤维膜壁中的乙酸己酯萃取，接着溶于纤维膜内碱性的TMAH接收相。取1 μL接收相进样，在进样口酚酸被TMAH衍生化成相应的甲酯。对影响萃取与衍生化效率的主要因素进行了优化，得到最佳条件：萃取剂为乙酸己酯，衍生化试剂和接受相为5% TMAH溶液，供给相pH=2，NaCl浓度为25%，搅拌速度为References
1 DONG Xia， LI Qi， GU GuoXian. Liquor Making， 2003， 30（6）： 63-65
董 霞， 李 崎， 顾国贤. 酿酒， 2003， 30（6）： 63-65
2 Vanbeneden N， Delvaux F， Delvaux F R. J. Chromatogr. A， 2006， 1136（2）： 237-242
3 Floridi S， Montanari L， Marconi O， Fantozzi P. J. Agr. Food Chem.， 2003， 51（6）： 1548-1554
4 Alonso García A， Cancho Grande B， Simal Gándara J. J. Chromatogr. A， 2004， 1054（12）： 175-180
5 Citová I， Sladkovsky R， Solich P. Anal. Chem. Acta， 2006， 573-574： 231-241
6 Proestos C， Sereli D， Komaitis M. Food Chem.， 2006， 95（1）： 44-52
7 Nur B A B， Ahmad M， Bahruddin S. Anal. Chem. Acta， 2012， 724： 59-66
8 TAN XiaoWang， WEI RuiPing， SONG YanXi， YI GuYang. Chinese J. Anal. Chem.， 2012， 40（9）： 1409-1414
谭小旺， 魏瑞萍， 宋燕西， 易谷洋. 分析化学， 2012， 40（9）： 1409-1414
9 Peng J F， Liu J F， Hu X L， JiangG B. J. Chromatogr. A， 2007， 1139（2）： 165-170
10 SHAO Yan， ZHANG LiJun， ZHANG ZhanEn. Chinese J. Anal. Chem.， 2011， 39（11）： 1753-1757
邵 焰， 张丽君， 张占恩. 分析化学， 2011， 39（11）： 1753-1757
11 Sun Y， Wang X Q， Huang Y L， Pan Z F， Wang L L. J. Sep. Sci.， 2013， 36（14）： 2268-2276
12 Wu J M， Lee H K. J. Anal. Chem.， 2006， 78（20）： 7292-7301
13 Sanagi M M， Miskam M， Ibrahim W A W， Hermawan D， AboulEnein H Y. J. Sep. Sci.， 2010， 33（14）： 2131-2139
Derivatization at Injection Port Following Hollow Fiber Microextraction
with Tetramethylammonium Hydroxide for Determination of
Six Phenolic Acids in Beers by Gas Chromatography
WANG XiaoQing1， HUANG YiLei1， SUN Yang2， PAN ZaiFa1， WANG LiLi*1
1（College of Chemical Engineering， Zhejiang University of Technology， Hangzhou 310014， China）
2（Zhejiang Province Institute of Metrology， Hangzhou 310013， China）
Abstract A method of derivatization at injection port following three phase hollow fiber microextraction with tetramethylammonium hydroxide （TMAH） as a dualfunction reagent， for the simultaneous determination of salicylic acid， phydroxybenzoic acid， cinnamic acid， vanillic acid， pcoumaric acid and ferulic acid in beers by gas chromatography was developed. Phenolic acids were extracted from aqueous samples to a thin layer of organic solvent （hexyl acetate） phase impregnated into the pores of the hollow fiber wall， and then back extracted to an acceptor solution （TMAH） located inside the lumen of the hollow fiber. Upon injection， the phenolic acids were derivatized to their methyl esters in the GC injection port. Several parameters related to the derivatization and extraction efficiency were optimized. The optimized conditions were as follows： hexyl acetate was used as the extraction solvent， an aqueous solution of TMAH （5% W/V） was used as the derivatization reagent and acceptor phase， the pH value of donor phase was 2.0， the concentrations of NaCl was 25% W/V， the stirring rate was 500 r/min， the extraction time was 40 min. Under the optimal conditions， the linear range of phenolic acids was 0.50-15.00 mg/L， the limits of detection were 0.05-0.18 mg/L. The proposed method was applied to the determination of the phenolic acids in beers. Vanillic acid， pcoumaric acid and ferulic acid were found in the beer samples， others were not detected. The spiked average recoveries were 90.1%-106.8% and RSD% was less than 5.9%（n=3）. The method is suitable for the determination of phenolic acids in beers.
Keywords Three phase hollow fiber microextraction； Gas chromatography； Injection port derivatization； Tetramethylammonium hydroxide； Phenolic acids
（Received 20 January 2014； accepted 7 March 2014）
This work was supported by the Analysis and Measurement Foundation of Zhejiang Province （No.2013C37067）
摘 要 建立了以乙酸己酯为萃取相、四甲基氢氧化铵（TMAH）为接收相的中空纤维三相液相微萃取结合进样口衍生化气相色谱法，同时测定啤酒中水杨酸、对羟基苯甲酸、肉桂酸、香草酸、对香豆酸、阿魏酸等酚酸类物质。啤酒中的酚酸被中空纤维膜壁中的乙酸己酯萃取，接着溶于纤维膜内碱性的TMAH接收相。取1 μL接收相进样，在进样口酚酸被TMAH衍生化成相应的甲酯。对影响萃取与衍生化效率的主要因素进行了优化，得到最佳条件：萃取剂为乙酸己酯，衍生化试剂和接受相为5% TMAH溶液，供给相pH=2，NaCl浓度为25%，搅拌速度为References
1 DONG Xia， LI Qi， GU GuoXian. Liquor Making， 2003， 30（6）： 63-65
董 霞， 李 崎， 顾国贤. 酿酒， 2003， 30（6）： 63-65
2 Vanbeneden N， Delvaux F， Delvaux F R. J. Chromatogr. A， 2006， 1136（2）： 237-242
3 Floridi S， Montanari L， Marconi O， Fantozzi P. J. Agr. Food Chem.， 2003， 51（6）： 1548-1554
4 Alonso García A， Cancho Grande B， Simal Gándara J. J. Chromatogr. A， 2004， 1054（12）： 175-180
5 Citová I， Sladkovsky R， Solich P. Anal. Chem. Acta， 2006， 573-574： 231-241
6 Proestos C， Sereli D， Komaitis M. Food Chem.， 2006， 95（1）： 44-52
7 Nur B A B， Ahmad M， Bahruddin S. Anal. Chem. Acta， 2012， 724： 59-66
8 TAN XiaoWang， WEI RuiPing， SONG YanXi， YI GuYang. Chinese J. Anal. Chem.， 2012， 40（9）： 1409-1414
谭小旺， 魏瑞萍， 宋燕西， 易谷洋. 分析化学， 2012， 40（9）： 1409-1414
9 Peng J F， Liu J F， Hu X L， JiangG B. J. Chromatogr. A， 2007， 1139（2）： 165-170
10 SHAO Yan， ZHANG LiJun， ZHANG ZhanEn. Chinese J. Anal. Chem.， 2011， 39（11）： 1753-1757
邵 焰， 张丽君， 张占恩. 分析化学， 2011， 39（11）： 1753-1757
11 Sun Y， Wang X Q， Huang Y L， Pan Z F， Wang L L. J. Sep. Sci.， 2013， 36（14）： 2268-2276
12 Wu J M， Lee H K. J. Anal. Chem.， 2006， 78（20）： 7292-7301
13 Sanagi M M， Miskam M， Ibrahim W A W， Hermawan D， AboulEnein H Y. J. Sep. Sci.， 2010， 33（14）： 2131-2139
Derivatization at Injection Port Following Hollow Fiber Microextraction
with Tetramethylammonium Hydroxide for Determination of
Six Phenolic Acids in Beers by Gas Chromatography
WANG XiaoQing1， HUANG YiLei1， SUN Yang2， PAN ZaiFa1， WANG LiLi*1
1（College of Chemical Engineering， Zhejiang University of Technology， Hangzhou 310014， China）
2（Zhejiang Province Institute of Metrology， Hangzhou 310013， China）
Abstract A method of derivatization at injection port following three phase hollow fiber microextraction with tetramethylammonium hydroxide （TMAH） as a dualfunction reagent， for the simultaneous determination of salicylic acid， phydroxybenzoic acid， cinnamic acid， vanillic acid， pcoumaric acid and ferulic acid in beers by gas chromatography was developed. Phenolic acids were extracted from aqueous samples to a thin layer of organic solvent （hexyl acetate） phase impregnated into the pores of the hollow fiber wall， and then back extracted to an acceptor solution （TMAH） located inside the lumen of the hollow fiber. Upon injection， the phenolic acids were derivatized to their methyl esters in the GC injection port. Several parameters related to the derivatization and extraction efficiency were optimized. The optimized conditions were as follows： hexyl acetate was used as the extraction solvent， an aqueous solution of TMAH （5% W/V） was used as the derivatization reagent and acceptor phase， the pH value of donor phase was 2.0， the concentrations of NaCl was 25% W/V， the stirring rate was 500 r/min， the extraction time was 40 min. Under the optimal conditions， the linear range of phenolic acids was 0.50-15.00 mg/L， the limits of detection were 0.05-0.18 mg/L. The proposed method was applied to the determination of the phenolic acids in beers. Vanillic acid， pcoumaric acid and ferulic acid were found in the beer samples， others were not detected. The spiked average recoveries were 90.1%-106.8% and RSD% was less than 5.9%（n=3）. The method is suitable for the determination of phenolic acids in beers.
Keywords Three phase hollow fiber microextraction； Gas chromatography； Injection port derivatization； Tetramethylammonium hydroxide； Phenolic acids
（Received 20 January 2014； accepted 7 March 2014）
This work was supported by the Analysis and Measurement Foundation of Zhejiang Province （No.2013C37067）
摘 要 建立了以乙酸己酯为萃取相、四甲基氢氧化铵（TMAH）为接收相的中空纤维三相液相微萃取结合进样口衍生化气相色谱法，同时测定啤酒中水杨酸、对羟基苯甲酸、肉桂酸、香草酸、对香豆酸、阿魏酸等酚酸类物质。啤酒中的酚酸被中空纤维膜壁中的乙酸己酯萃取，接着溶于纤维膜内碱性的TMAH接收相。取1 μL接收相进样，在进样口酚酸被TMAH衍生化成相应的甲酯。对影响萃取与衍生化效率的主要因素进行了优化，得到最佳条件：萃取剂为乙酸己酯，衍生化试剂和接受相为5% TMAH溶液，供给相pH=2，NaCl浓度为25%，搅拌速度为References
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Derivatization at Injection Port Following Hollow Fiber Microextraction
with Tetramethylammonium Hydroxide for Determination of
Six Phenolic Acids in Beers by Gas Chromatography
WANG XiaoQing1， HUANG YiLei1， SUN Yang2， PAN ZaiFa1， WANG LiLi*1
1（College of Chemical Engineering， Zhejiang University of Technology， Hangzhou 310014， China）
2（Zhejiang Province Institute of Metrology， Hangzhou 310013， China）
Abstract A method of derivatization at injection port following three phase hollow fiber microextraction with tetramethylammonium hydroxide （TMAH） as a dualfunction reagent， for the simultaneous determination of salicylic acid， phydroxybenzoic acid， cinnamic acid， vanillic acid， pcoumaric acid and ferulic acid in beers by gas chromatography was developed. Phenolic acids were extracted from aqueous samples to a thin layer of organic solvent （hexyl acetate） phase impregnated into the pores of the hollow fiber wall， and then back extracted to an acceptor solution （TMAH） located inside the lumen of the hollow fiber. Upon injection， the phenolic acids were derivatized to their methyl esters in the GC injection port. Several parameters related to the derivatization and extraction efficiency were optimized. The optimized conditions were as follows： hexyl acetate was used as the extraction solvent， an aqueous solution of TMAH （5% W/V） was used as the derivatization reagent and acceptor phase， the pH value of donor phase was 2.0， the concentrations of NaCl was 25% W/V， the stirring rate was 500 r/min， the extraction time was 40 min. Under the optimal conditions， the linear range of phenolic acids was 0.50-15.00 mg/L， the limits of detection were 0.05-0.18 mg/L. The proposed method was applied to the determination of the phenolic acids in beers. Vanillic acid， pcoumaric acid and ferulic acid were found in the beer samples， others were not detected. The spiked average recoveries were 90.1%-106.8% and RSD% was less than 5.9%（n=3）. The method is suitable for the determination of phenolic acids in beers.
Keywords Three phase hollow fiber microextraction； Gas chromatography； Injection port derivatization； Tetramethylammonium hydroxide； Phenolic acids
（Received 20 January 2014； accepted 7 March 2014）
This work was supported by the Analysis and Measurement Foundation of Zhejiang Province （No.2013C37067）
