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During a recent webinar I shared method details for mycotoxin analysis on the SCIEX 7500 system. In this blog i will share the Q&A for the submitted questions that we did not have chance to answer during the live webinar.

1. What were the challenges with this method?

Mycotoxins are wide ranged analytes in terms of their chemical and physical characteristics. To analyze them together in a single method is challenging overall.

Some are sensitive to temperature, some show different behaviour depending on the pH conditions, some are only detectable as adducts, hard to find in their protonated (pos) or deprotonated (neg) forms, and some are isobaric isomers.

So, it’s a complicated mixture and we needed to find the best compromise for this method to still meet the regulatory requirements.

As described in the presentation we tested different transitions, several columns and solvent systems and finally were looking for the best solution we had in mind.

2. Can you share any tips and tricks?

It’s hard to share just one for all mycotoxins.

The developed application works fine for the given scope, but if the scope is different (e.g. you just want to measure the aflatoxins) I would recommend using a different solvent system.

We learned a lot about the behaviour of every analyte in different conditions and had to evaluate a lot of data.

So, we need to adjust applications to the special needs of the customer. The scope, the matrix, the solvent system and the sample preparation.

Feel free to contact me (michael.zellmann@sciex.com) with your scope and your needs and we can talk about your specific solution and the best choice in terms of sample prep, column, and solvent system. 

3. Did you see any challenges with fumonisins and OTA?

Yes!

Regarding fumonisins:

The standard solutions are degrading within 12 to 24 hours after taking them out of the freezer. They are more stable in ACN/water conditions, but the stability is still insufficient for a long LC-MS/MS run.

Due to the growth of fumonisins in matrix (in clusters), it’s very hard to get a homogeneous sample.

The results will always vary a lot depending on the time range between homogenization of the sample and analysis.

From my experience a matrix matched calibration gives results with high uncertainty. Solvent calibration looks sufficient, if measured as soon as possibly after taking the standards out of the fridge.

My tip here:

Get rid of the matrix effect by injecting as low as possible.

Use a standard matrix from the supermarket as control material for your standards. Verify your values within a precision range of around 30-35%. This is not perfect. But let perfect be the enemy of good.

Over time you’ll find results, trustful enough for your routine analysis and for your customers.

OTA:

Unfortunately, I don’t have any experience from routine analysis over a long-time range.

We showed in the application we can measure OTA in pos and neg, so I would recommend doing so and quantify it via internal standard.

As shown in the application as well, OTA shows very different results. In pos it’s around 80% of recovery in matrix and in neg there could even be matrix enhancement depending on the matrix.

The most accurate way seems to be a matrix matched calibration with spiking before sample preparation.

The work on OTA is not finished, I guess. But this is only my small insight into this analyte. Perhaps there are already scientists out there who solved the OTA issues.