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

doi:10.4236/ajac.2014.57049

Maria Angela Tallarico Adorno, Julia S Hirasawa + Show 1 more

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https://doi.org/10.4236/ajac.2014.57049

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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.

Highlights

The factors that affect the performance of anaerobic reactors are related to the production of the so called vola-How to cite this paper: Adorno, M.A.T., et al (2014) Development and Validation of Two Methods to Quantify Volatile Acids (C2-C6) by Gas Chromatographic (GC)/FID: Headspace (Automatic and Manual) and Liquid-Liquid Extraction (LLE)
In the anaerobic processes of wastewater treatment it is important to monitor the levels of such substances as well as others by-products generated, acetone and n-butanol, in order to evaluate the status of the system
The smaller differences between the standard deviation of the responses were observed for the samples centrifuged and analyzed without addition of any preservative and frozen or refrigerated, after 60 days

Summary

Introduction

The factors that affect the performance of anaerobic reactors are related to the production of the so called vola-How to cite this paper: Adorno, M.A.T., et al (2014) Development and Validation of Two Methods to Quantify Volatile Acids (C2-C6) by GC/FID: Headspace (Automatic and Manual) and Liquid-Liquid Extraction (LLE). The concentration of the VFA gives fast information of the status of the anaerobic processes and is an important indicator for monitoring them compared to others such as alkalinity, chemical oxygen demand (COD) and pH [1]. In the anaerobic processes of wastewater treatment it is important to monitor the levels of such substances as well as others by-products generated, acetone and n-butanol, in order to evaluate the status of the system. Several studies have pointed the importance of the concentration of the individual VFA as an early warning indicator for process failure [2]-[5]. These include the concentration of isobutyric and isovaleric acids [2]-[4]. According to Ahring et al [5] the accumulation of VFA suggests an imbalance in the process

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