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Efficiency of Various Solvents in the Extraction of Aflatoxin from Naturally Contaminated Cottonseed Meal, Corn Gluten Meal, Corn Gluten Feed, and Dried Distillers Grain

Bruce R. Malone, Carrie K. Maune

Trilogy Analytical Laboratory, Washington, Missouri

 

     Abstract

An evaluation was conducted to compare the extraction efficiency of aflatoxins from naturally contaminated cottonseed meal, corn gluten meal, corn gluten feed, and dried distillers grain using various solvents. The solvents compared were acetonitrile/water (84/16), acetonitrile/water (90/10), methanol/water (80/20), methanol/water (70/30), and chloroform. These solvents were chosen because they are commonly used for HPLC and test kit analysis of aflatoxins. Each naturally contaminated matrix was finely ground, well homogenized, and extracted using the various solvents in replicates of 10 and analyzed by HPLC using AOAC method #994.08 substituting the Kobra cell for the TFA derivative. The data demonstrates that the extraction efficiency of various solvents is matrix dependent with acetonitrile/water (84/16) consistently exhibiting the best extraction of aflatoxin. Solvents containing methanol/water should not be used for the extraction of aflatoxin from cottonseed meal. These solvents containing methanol/water at ratios of 80/20 and 70/30 only extracted 17% of the aflatoxin from cottonseed meal compared to the acetonitrile/water (84/16) solvent. This comparison of extraction solvents demonstrates the importance of the evaluation of naturally contaminated matrices when validating new methodology.

     Procedure

Dried distillers grain, corn gluten meal, corn
gluten feed, and cotton seed meal naturally
contaminated with aflatoxin were finely ground and well homogenized
Each sample was extracted with various extraction solvents, including acetonitrile/water (84/16),
acetonitrile/water (90/10), methanol/water
(80/20), methanol/water (70/30) and chloroform.
Each commodity was extracted with each extraction solvent in replicates of 10 for 1 hour on a reciprocating shaker (180 rpms)
The samples were analyzed for aflatoxins by
HPLC using AOAC method 994.08 substituting
the Kobra cell for the TFA derivative.
Due to the differences in extraction solvents,
the following method modifications were used:
– Acetonitrile/water (84/16) and (90/10): no modifications
– Methanol/water (80/20) and (70/30): 1ml of extract was combined with 1ml of acetonitrile before the solid phase purification step.
– Chloroform: 2 ml portions of each extract was evaporated and redisolved in acetonitrile/water prior to the solid phase purification step.

Aflatoxin Extraction Images.png

 

     Procedure continued

Aflatoxin Extraction Graphs and Charts.pngAflatoxin Extraction Chart.png

     Conclusions

The efficiency of organic solvents in the extraction of aflatoxin from naturally contaminated products can be matrix dependent.
This comparison of extraction solvents demonstrates the importance of the evaluation of naturally contaminated matrices when validating new methodology.
• Cotton Seed Meal
– Acetonitrile/water (84/16) and Chloroform were the most efficient extraction solvents
– Acetonitrile/water (90/10), methanol/water (80/20, and methanol/water (70/30) should not be used for the extraction of aflatoxin from cotton seed meal
Corn Gluten Feed
– Acetonitrile/water (84/16) was the most efficient extraction solvent
– Chloroform, Acetonitrile/water (90/10), methanol/water (80/20), and methanol/water (70/30) had similar extraction efficiencies
• Dried Distillers Grain
– Acetonitrile/water (84/16) and acetonitrile/water (90/10) were the most efficient extraction solvents
– Chloroform, methanol/water (80/20), and methanol/water (70/30) had similar extraction efficiencies
• Corn Gluten Meal
– Acetonitrile/water (84/16) and Chloroform were the most efficient extraction solvents
– Acetonitrile/water (90/10), methanol/water (80/20), and methanol/water (70/30) should not be used for the extraction of aflatoxin from corn gluten meal

 


 

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