Development and Validation of Two Methods to Quantify Volatile Acids (C2-C6) by GC/FID: Headspace (Automatic and Manual) and Liquid-Liquid Extraction (LLE)

Maria Angela Tallarico Adorno, Julia S. Hirasawa, Maria Bernadete Amâncio Varesche

Department of Hydraulics and Sanitation, School of Engineering of São Carlos, University of São Paulo, São Carlos, Brazil.

DOI: 10.4236/ajac.2014.57049                

Abstract

The concentration of the volatile fatty acids (VFA) is an important indicator of the status of an-aerobic processes, but most of the existing methods require sample pretreatment and are labor-intensive. It was developed and validated a rapid Gas Chromatographic (GC) method to quantify seven VFA (acetic, propionic, isobutyric, butyric, isovaleric, valeric and caproic), acetone, methanol, ethanol and n-butanol by headspace (automatic and manual) and liquid-liquid extraction (LLE) with diethyl ether (only VFA). The determination was made in a Shimadzu Gas Chromatograph equipped with a Flame Ionization Detector (GC/FID), a headspace auto-sampler and an HP-INNOWAX column. Isobutanol and crotonic acid were utilized as internal standards (IS). The validation parameters evaluated were: precision (coefficient of variation—C.V.% for the retention times, from 0.02 to 0.87), linearity (R² = 0.9291 - 0.9997), limits of detection (from 3.97 to 36.45 mg·L﹣1) and instrumental precision (from 0.01 to 0.53), which provide evidence that the methods are adequate to determine these analytes in samples from anaerobic reactors and from the environment.

Keywords

Short Chain Organic Acids, Gas Chromatography, Ethyl Ether, Anaerobic Processes

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Boe, K., Batstone, D.J. and Angelidaki, I. (2007) Online Headspace Chromatographic Method for Measuring VFA in Biogas Reactor. Water Science & Technology, 52, 473-478.
[2]	Hill, D.T. and Holmberg, R.D. (1988) Long Chain Volatile Fatty Acid Relationships in Anaerobic Digestion of Swine Waste. Biological Wastes, 23, 195-214. http://dx.doi.org/10.1016/0269-7483(88)90034-1
[3]	Hill, D.T. and Bolte, J.P. (1989) Digester Stress as Related to Iso-Butyric and Iso-Valeric Acids. Biological Wastes, 28, 33-37. http://dx.doi.org/10.1016/0269-7483(89)90047-5
[4]	Cobb, S.A. and Hill, D.T. (1991) Volatile Fatty-Acid Relationships in Attached Growth Anaerobic Fermenters. Transactions of the ASAE, 34, 2564-2572. http://dx.doi.org/10.13031/2013.31907
[5]	Ahring, B.K., Sandberg, M. and Angelidaki, I. (1995) Volatile Fatty Acids as Indicators of Process Imbalance in Anaerobic Digestors. Applied Microbiology and Biotechnology, 43, 559-565. http://dx.doi.org/10.1007/BF00218466
[6]	Angelidaki, I., Petersen, S.P. and Ahring, B.K. (1990) Effects of Lipids on Thermophilic Anaerobic Digestion and Reduction of Lipid Inhibition upon Addition of Bentonite. Applied Microbiology and Biotechnology, 33, 469-472. http://dx.doi.org/10.1007/BF00176668
[7]	Manni, G. and Caron, F. (1995) Calibration and Determination of Volatile Fatty Acids in Waste Leachates by Gas Chromatography. Journal of Chromatography A, 690, 237. http://dx.doi.org/10.1016/0021-9673(94)01081-O
[8]	Albert, D.B. and Martens, C.S. (1994) Determination of Low-Molecular-Weight Organic Acid Concentrations in Seawater and Pore-Water Samples via HPLC. Marine Chemistry, 56, 27-37. http://dx.doi.org/10.1016/S0304-4203(96)00083-7
[9]	Pan, L., Adams, M. and Pawliszyn, J. (1998) Determination of Fatty Acids Using Solid-Phase Microextraction. Analytical Chemistry, 67, 4396-4403. http://dx.doi.org/10.1021/ac00119a031
[10]	Wright, O. and Wright, W. (2008) Comparative Analysis of Eight Esterification Methods in the Quantitative Determination of Vegetable Oil Fatty Acid Methyl Esters (FAME). Journal of Brazilian Chemical Society, 19, 1475-1483. http://dx.doi.org/10.1590/S0103-50532008000800006
[11]	Rocha, S., Ramalheira, V., Barros, A., Delgadillo, I. and Coimbra, M.A. (2001) Headspace Solid Phase Microextraction (SPME) Analysis of Flavor Compounds in Wines. Effect of the Matrix Volatile Composition in the Relative Response Factors in a Wine Model. Journal of Agricultural and Food Chemistry, 49, 5142-5151. http://dx.doi.org/10.1021/jf010566m
[12]	Roy, B.C., Awual, M.R. and Goto, M. (2007) Effect of Inorganic Salts on Ternary Equilibrium Data of Propionic Acid-Water-Solvents Systems. Journal of Applied Sciences, 7, 1053-1060. http://dx.doi.org/10.3923/jas.2007.1053.1060
[13]	Ribani, M., Bottoli, C.B.G., Collins, C.H., Jardim, I.C.S.F. and Melo, L.F.C. (2004) Validação em Métodos Cromato-gráficos e Eletroforéticos. Química Nova, 27, 771-780. http://dx.doi.org/10.1590/S0100-40422004000500017
[14]	Miller, J.C. and Miller, J.N. (1993) Statistics for Analytical Chemistry. 3rd Edition, Ellis Horwood Limited, England.
[15]	Duarte, I.C.S., Oliveira, L.L., Buzzini, A.P., Adorno, M.A.T. and Varesche, M.B.A. (2006) Development of a Method by HPLC to Determine LAS and Its Application in Anaerobic Reactors. Journal of the Brazilian Chemical Society, 17, 1360-1367. http://dx.doi.org/10.1590/S0103-50532006000700025
[16]	Damasceno, L.H.S., Adorno, M.A.T., Hirasawa, J.S., Varesche, M.B.A. and Zaiat, M. (2008) Development and Validation of a HPLC Method for the Determination of Aldicarb, Aldicarb Sulfoxide and Aldicarb Sulfone in Liquid Samples from Anaerobic Reactors. Journal of the Brazilian Chemical Society, 19, 1158-1164. http://dx.doi.org/10.1590/S0103-50532008000600016
[17]	Budavari, S. (1996) The Merck Index. 12th Edition, Merck & CO, Inc., Whitehouse Station.
[18]	Maintinger, S.I., Fernandes, B.S., Adorno, M.A.T., Hirasawa, J.S., Varesche, M.B.A. and Zaiat, M. (2008) Fermentative Hydrogen Production by Microbial Consortium. International Journal of Hydrogen Energy, 33, 4309-4317. http://dx.doi.org/10.1016/j.ijhydene.2008.06.053
[19]	Bratinova, S., Raffael, B. and Simoneau, V. (2009) Guidelines for Performance Criteria and Validation Procedures of Analytical Methods Used in Controls of Food Contact Materials. JRC Scientific and Technical Reports, EUR 24105 EN, Italy.