Advertisement

4 Preparation of Mycotoxin Standards

  • Stanley Nesheim
  • Michael E. Stack
Part of the Methods in Molecular Biology™ book series (MIMB, volume 157)

Abstract

The detection and quantitation of mycotoxins requires pure standards or standards for which the purity and identity are known. Methods for identifying and calibrating standards are necessary. Few commercial sources exist for the mycotoxins discussed in this volume, and for most mycotoxins, specifications of purity are not available. If primary standards are not available commercially, other sources may be investigators who have isolated standard materials which they may be willing to share. As a last resort, it may become necessary to isolate mycotoxins from appropriate fungal cultures. Calibration and purity tests have been developed based on physical and chemical properties such as melting points, visible/ultraviolet, nuclear magnetic, and infrared spectros-copy and mass spectrometry, and various methods of chromatography. Standards are quite expensive, and regardless of the source, the purity and authenticity can be variable. Analysts are responsible for calibrating the standards used in analysis. Procedures have been developed for this purpose (1). The present protocol outlines the preparation, calibration, purity determination, preparation of solutions, distribution, storage, and uses of quantitative aflatoxin standards, and is intended as a guide for application to other mycotoxins which are used in the protocols in this volume. The amounts needed for most methods of analysis and for fortifying various matrixes for use as laboratory test or control samples, are in the nanogram or microgram ranges. The protocols given are for the aflatoxins B1, B2, G1, and G2. Mycotoxins standards other than the aflatoxins may be prepared in the same way using the information provided in Table 1. For some mycotoxins, such as the fumonisins and deoxynivalenol, UV spectroscopy cannot be used due to the lack of a suitable chromophore in the molecule. For these molecules, use gravimetric methods combined with gas chromatography, liquid chromatography, and/or mass spectrometry.
Table 1

Calibration of Mycotoxins by UV Spectroscopy

Mycotoxin

Solvent

Conc. μg/mL

Molecular Weight

Molar Absorptivity e

Wavelength, a nm

Reference

Aflatoxin B:

Toluene-acetonitrile (9 + 1)

10

312

19,300

350

3

Aflatoxin B2

Toluene-acetonitrile (9 + 1)

10

314

21,000

350

3

Aflatoxin Gj

Toluene-acetonitrile (9 + 1)

10

328

16,400

350

3

Aflatoxin G2

Toluene-acetonitrile (9 + 1)

10

330

18,300

350

3

Aflatoxin M 1

Acetonitrile

10

328

18,900

350

1

Aflatoxin M2

Acetonitrile

10

330

21,400

350

1

Citrinin

Chloroform

10

250

16,100

332

2

Cyclopiazonic Acid

Methanol

10

336

20,417

284

2

Deoxynivalenol

Ethanol

50

296

4,500

218

2

Moniliformin

Water

50

98

5,600

260

2

Ochratoxin A

Benzene-acetic acid (9 + 1)

40

403

5,600

333

1

Patulin

Ethanol

10

154

14,600

275

1

Sterigmatocystin

Benzene

10

324

15,200

325

1

Zearalenone

Methanol

50

318

6,000

314

1

a The wavelength is variable depending on the solvent. The absorbance, A, is themaximum as measured

Keywords

Thin Layer Chromatography Volumetric Flask Purity Test Purity Determination Aflatoxin Concentration 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

References

  1. 1.
    Scott, P. M. (1995) Natural toxins, in Official Methods of Analysis ofAOAC International, 16th ed. (Cunniff, P., ed.), AOAC International, Gaithersburg, MD, Chapter 49, pp. 1–49.Google Scholar
  2. 2.
    Cole, R. J. and Cox, R. H. (1981) Handbook of Toxic Fungal Metabolites. Academic Press, New York.Google Scholar
  3. 3.
    Nesheim, S., Trucksess, M. W., and Page, S. W. (1999) Molar Absorptivities of Aflatoxins B1, B2, G1, and G2 in Acetonitrile, Methanol and Toluene-acetonitrile (9+1) (Modification of AOAC Official Method 971.22): Collaborative Study. J. AOAC Int. 82, 251–258.PubMedGoogle Scholar

Copyright information

© Humana Press Inc. 2001

Authors and Affiliations

  • Stanley Nesheim
    • 1
  • Michael E. Stack
    • 1
  1. 1.Food and Drug AdministrationWashington

Personalised recommendations