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A Novel Approach for Determination of Free Fatty Acids in Vegetable Oils by a Flow Injection System with Manual Injection

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Lipids

Abstract

A non-aqueous flow injection method for determining free fatty acid (FFA) content in corn and sunflower oil samples was developed. A single-line manifold system was built by modification of an HPLC for flow injection analysis (FIA). Without pre-treatment, oil samples were injected into a n-propanol solution containing KOH and phenolphthalein (PHP). The main parameters, such as flow rate of carrier phase, length, geometry, inner diameters of the coils and reagent concentration were all optimized. The proposed FIA method was validated for precision, accuracy, linear region, limit of detection (LOD) and limit of quantification (LOQ). The intra- and inter-day measurements of the precision of the method were found to be within the limits of acceptance criteria (RSD < 1%), and were rugged when the method was performed by a different analyst. The linear concentration range was calculated as 0.09–1.50 and 0.07–1.40 FFA% for corn and sunflower oils, correspondingly. The LOD and LOQ were found to be 7.53 × 10−4–2.28 × 10−3 oleic acid % and 7.11 × 10−4–2.23 × 10−3 oleic acid % for corn and sunflower oils, respectively. The results were compared with those obtained by the AOCS (Ca-5a-40) method using statistical t and F tests, and a significant difference was not observed between the methods at a 95% confidence level. The proposed method is suitable for quality control of routine applications due to its simplicity, high sample throughput, and economy of solvents and sample, offering considerable promise as a low cost analytical system that needs minimum human intervention over long periods of time.

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Abbreviations

AOCS:

American Oil Chemists’ Society

FFA:

Free fatty acids

FIA:

Flow injection analysis

IUPAC:

International Union of Pure and Applied Chemistry

PHP:

Phenolphthalein

WRM:

Working references materials

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Acknowledgments

This study, a part of Ph.D. thesis entitled “Improvement of Edible Oil Analysis Methods by Flow Injection Systems” was supported by Selcuk University Coordination of Scientific Research with SU-BAP 08-101029 project numbers. The authors wish to thank the Principal of Selcuk University and Scientific Research Projects Coordination.

Conflict of interest

The authors declare that there is no conflict of interest.

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Authors and Affiliations

  1. Department of Chemistry, Faculty of Science, Selcuk University, 42075, Campus-Konya, Turkey

    H. Filiz Ayyildiz & Huseyin Kara

  2. National Centre of Excellence in Analytical Chemistry, University of Sindh, Jamshoro, 76080, Pakistan

    S. T. H. Sherazi

Authors
  1. H. Filiz Ayyildiz
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  2. Huseyin Kara
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  3. S. T. H. Sherazi
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Corresponding author

Correspondence to Huseyin Kara.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Supplemental Fig 1. Scatter plot with fit and residual plot obtained from ANOVA test for corn oil samples

Supplemental Table 1. Properties of reagents used in optimization experiments for each coil

Supplemental Table 2. Repeatability (intra day) and intermediate precision (inter-day) data of FIA method developed for FFA% Determination of Corn Oil

Supplemental Table 3. Regression statistics by ANOVA of linearity of the FIA method developed for FFA% Determination of Corn Oil

Supplementary material 1 (PDF 95 kb)

Supplementary material 2 (DOCX 567 kb)

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Ayyildiz, H.F., Kara, H. & Sherazi, S.T.H. A Novel Approach for Determination of Free Fatty Acids in Vegetable Oils by a Flow Injection System with Manual Injection. Lipids 46, 1181–1190 (2011). https://doi.org/10.1007/s11745-011-3610-9

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  • DOI: https://doi.org/10.1007/s11745-011-3610-9

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