Test Kits and Rapid Methods for Use in a Non-Laboratory Environment/Non-Specialist Laboratory

The ideal testing environment in which to obtain the most accurate and reliable results in the analysis of foods for any of the mycotoxins is a specialist laboratory using standardised or certified methods of analysis. Often more time- or cost-efficient methods are needed that are also reliable and accurate. There are a number of test kits available that are suitable without the use of expensive equipment or the need for highly trained analysts, and most fulfil the requirements of speed, efficiency and simplicity without costing a great deal per sample.

Test kits are available in

• quantitative formats (e.g. ELISA's),
• semi-quantitative formats (ELISA or immunoaffinity column technology without specialised reading equipment) or
• qualitative (enzyme-linked immunoassay or membrane-based kits) formats

There are kits available for

For use in a non-laboratory environment /non-specialist laboratory these kits have both advantages and disadvantages, which vary between the kits:

Advantages	Disadvantages
For use in a non-laboratory environment /non specialist laboratory
Sensitivity - most kits give results at a detection limit required by EC legislation, or national or international guidelines.	Precision may not be as good as some laboratory methods.
Rapid results - often confirming presence or absence of toxin.	False positives are possible, and positive results on which decisions are made, require confirmation using more expensive laboratory methods.
No need for expensive equipment.	Most test kits do require some simple laboratory apparatus (e.g. for sample preparation).
Easy to use by semi-trained or non-trained personnel.	A laboratory environment for carrying out the testing is highly recommended.
No need for large quantities of solvents, toxic standards or expensive reagents.

When using test kits, it is important to carefully follow the instructions provided by the supplier in order to keep errors to a minimum. In particular storage of most kits requires refrigeration at a specified temperature. It is also important to be aware that these kits have a limited shelf-life.

A key point to note is that any analysis for mycotoxins is only as effective as the sampling procedure. Contamination of most food products by mycotoxins (notable exceptions are well-mixed liquids such as milk) can vary greatly throughout the product batch with hotspots of distribution - a small number of highly contaminated grains amongst low-level contamination or non-contaminated grains. The collection of a representative sample is therefore important and consideration should be made of the sample size. For more information on this subject, there will be shortly be a fact sheet available on sampling.

General Requirements for Testing in a Non-Laboratory Environment

Test kits are generally supplied with detailed instructions for performing the analysis. Additional equipment needed for use with the test kit is sometimes supplied or guidance may be given on the purchase of this equipment. There are though, some general requirements:

Sample preparation equipment:

• grinders for grain or nuts,
• homogenisers for liquid or semi-liquid products,
• analytical balances for varying ranges of weights,
• reagents of a certain purity,
• sample blenders,
• filtration equipment and other simple laboratory glassware
• (e.g. beakers, measuring cylinders),
• vacuum pump.

For some kits and rapid methods other more specialised equipment is necessary:

• pipettes accurate for measuring small quantities of liquids (ml or even µl),
• laboratory oven, heating block or source of heat
• instruments for measuring mycotoxin contamination quantitatively

N.B. it is important that both pipettes and instruments such as fluorimeters and spectrophotometers are calibrated regularly.

There are international bodies working in the field of evaluation, certification and/or standardisation of analytical methods including those for mycotoxins. A number of these bodies have, in recent years, run programmes to either produce rapid methods for the analysis of various mycotoxins, or to evaluate, certify or standardise established rapid methods or a small number of available test kits.

JOINT FAO/IAEA DIVISION: Co-ordinated Research Programme (CRP) on Evaluation of Methods of Analysis for Determining Mycotoxin Contamination of Food and Feed.

AOAC Research Institute, a subsidiary of AOAC International, administers the Performance Tested Methods Program providing independent third party review of test kit performance claims.

Currently Available Test Kits and Rapid Methods

Rapid Methods based on TLC There are TLC methods available for all the commonly occurring mycotoxins. Examples include: those evaluated by FAO/IAEA CRP and AOAC RI Performance Tested Methods Program (see above).

Technicians require some specialised training. However, no expensive equipment is required as quantitative or even semi-qualitative results can be obtained because most mycotoxin spots on TLC plates fluoresce when placed under UV light. In some cases, chemical reagents are required to make spots visible. A number of solvents and reagents are required, some of which are toxic and the toxin standards are needed for the test.

Test Kits based on immunoaffinity column format: In addition to being a widely used tool for HPLC or GC techniques, immunoaffinity columns may be used as the basis of a semi-quantitative test for some mycotoxins. The specificity of the column to a mycotoxin such as aflatoxin or ochratioxin A can be used to retain and concentrate the toxin analyte. Columns can only be used once. Immunoaffinity columns are available for aflatoxins, ochratoxin A, deoxynivalenol, T-2 toxin, fumonisins B₁ and B₂ and zearalenone. Most columns are for the analysis of single toxins, but there are also columns available for more than one mycotoxin.

Immunoaffinity columns are available from: R-Biopharm Rhone, Vicam, Neogen, and R-Biopharm.

ELISA's: These are generally used to screen for the presence of a mycotoxin in the test sample above a certain level, with the advantage that the clean-up procedures are not as intensive as for other analytical (eg HPLC) techniques. The principle of ELISA technology for mycotoxin analysis is described in Fact Sheet 1. Quantitative results are obtained by reading the colour by fluorimetry or photometrically, and semi-quantitative results can be obtained by determining concentration by measurement by visual comparison - the colour change of reaction is inversely proportional to the concentration of the toxin present.

ELISA's are available from R-Biopharme Rhone, Diagnostix, International Diagnostic Systems Corp., Diffchamb, Neogen, R-Biopharme, Tepnel, Romer Laboratories and ELISA-Technologies Inc.

Other Techniques: enzyme-linked immunoassay, radioimmunoassay, and lateral flow strip test are all techniques employed by manufacturers of test kits for mycotoxins. There are also SPE columns designed specifically for the analysis of mycotoxins and which are available commercially.

Charm Sciences Inc., Idexx Laboratories and Romer Laboratories all supply products of these types.