Determination of methanol residues in crude glycerol for animal feed by gas chromatography

Carina Nazato,Alessandra De Cássia Romero,Adibe Luiz Abdalla

doi:10.1590/1678-992x-2017-0362

Carina Nazato, Alessandra De Cássia Romero + Show 1 more

Open Access

https://doi.org/10.1590/1678-992x-2017-0362

Copy DOI

Abstract

ABSTRACT: Crude glycerol is a major by-product of biodiesel production and is an economical additive feed for ruminants. However, residual methanol in crude glycerol can be harmful to animal health. Several methods exist for quantifying methanol residues in biodiesel, yet few have been described that identify the methanol level in crude glycerol. We propose a method for determining the methanol level in crude glycerol destined for animal feed. Crude glycerol was extracted from the headspace and quantified by gas chromatography using a flame ionization detector (GC-FID). The method was linear up to 0.5 % of methanol. The limits of detection (LOD) and quantification (LOQ) were 0.015 and 0.031 %, respectively. No significant matrix effects were observed. Precision was 2 % at the 0.05 and 0.5 % levels. The average percentage of recovery was 90 %. Three analyzed samples of crude glycerol had methanol residues of 0.027-7.802 %. Furthermore, this methanol quantification method may be externally or internally calibrated using a GC manual injector. A reduction of at least 20 % in running time was obtained with good resolution between the peaks. Thus, this method can be applied to determine the methanol level in crude glycerol according to the upper limits for animal feed (5,000 ppm) and for human consumption (150 ppm). Finally, this method is useful for the quality control of crude glycerol intended for use in animal feed, enabling the alternative use of this by-product to add value to the biodiesel production chain.

Highlights

Crude glycerol is a major by-product of biodiesel production and it is usually further refined to obtain a pure material that is used by the pharmaceutical and cosmetic industries
We propose a method for determining the methanol level in crude glycerol destined for animal feed
Crude glycerol was extracted from the headspace and quantified by gas chromatography using a flame ionization detector (GC-FID)

Summary

Introduction

Crude glycerol is a major by-product of biodiesel production and it is usually further refined to obtain a pure material that is used by the pharmaceutical and cosmetic industries. Glycerol in animal diets increases the efficiency of energy usage by animals without any adverse effects (Lee et al, 2011; Wilbert et al, 2013) These claims are not fully supported by the literature (Boyd et al, 2013; Ezequiel et al, 2015), implying that the remaining levels of chemical residues in crude glycerol generated from the biodisel industry should be further tested (Paiva, 2015). The Association of American Feed Control (AAFCO) approved in 2015 an allowable limit of up to 5,000 ppm of methanol in crude glycerol from biodiesel production (Wilkinson, 2017). This limit is more realistic than the previous FDA methanol limit established for human nutrition (150 ppm), which had been used for animal feed until 2006 (FDA, 2014). We propose a simple methodology for quantifying methanol residues in crude glycerol by gas chromatography

Materials and Methods

Results and Discussion

Conclusions