Dispatches from Pittcon 2018 in Orlando

Waters tackles ‘challenging’ polar pesticides

By Joseph James Whitworth

- Last updated on GMT

Joe Romano of Waters Corporation at Pittcon
Joe Romano of Waters Corporation at Pittcon
Chromatographic analysis of polar pesticides, including glyphosate, can be challenging, according to Waters Corporation.

Analysis of the herbicide, its metabolites and similar compounds is difficult due to the lack of retention by reverse phase techniques. Alternatives include derivatization and ion chromatography.

However, due to time-consuming sample preparation, MS incompatible solvents and need for specialized equipment and/or reagents, the underivatized LC-MS/MS approach is preferred.

A December 2017 draft risk assessment​​ from the US Environmental Protection Agency​ concluded glyphosate 'is not likely to be carcinogenic to humans​​.'

In Europe late last year the license of glyphosate​ was renewed for five years. Glyphosate is an active ingredient in Roundup sold by Monsanto, which is one of the most commonly used weed killers in the EU.

Analyse without derivatization

Joe Romano, senior manager at Waters Corporation, said challenges are around separation and ionization.

“Traditionally glyphosate has been done by derivatization to get better sensitivity, however people want a better, more robust, reliable method that is more to direct injection,” ​he told FoodQualityNews at Pittcon.

"So what we've developed is a method to do direct injection of glyphosate and polar pesticides using sample preparation to remove and extract them from food using the QuPPe [Quick Polar Pesticides Method].

"We've come up with new column chemistry, called Torus, that allows us to get separation of the polar pesticides, get good peak shape and longevity.

"So we get a robust separation and reproducible retention times, we run it with small particle technology with our UPLC I-Class system with our Xevo tandem mass spectrometer (Xevo TQ-XS). We've been able to show low levels of detection for glyphosate and polar pesticides in crude food extracts.

No dice with normal multi residue analysis

Romano said experts doing this kind of work know they have to do analysis for glyphosate and its metabolites​ differently.

“These are difficult, challenging pesticides. They are not going to work in your normal multi residue analysis series where you are running a screen of 200-300 compounds. You are not going to be able to do it. You need a method dedicated to this class of pesticides. They are very challenging to do by LC-MS and by direct injection without derivatization.”

Chromatographic separation can be achieved on a weak ion exchange/ hydrophilic interaction liquid chromatography (HILIC) column applying an ammonium formate mobile phase gradient.

“We got many requests from customers saying ‘we don’t have a column that is robust enough to do this application’​,” said Romano.

“The traditional column chemistries used tend to wear out quickly or they cannot get good separation or peak shape. We went back and talked to our R&D group and looked at our capabilities and we came up with a chemistry that works and is robust.”

People want easier sample preparation and ways of performing multi residue analysis, said Romano.

“When you are dealing with a complex food matrix that is a challenge because it is very difficult to isolate the things you want to analyse from the things you don’t want to analyse,” ​he said.

“So coming up with a cheap and easy sample preparation method is a challenge. Eliminating the derivatization step saves time and money so they can perform the analysis faster and more efficiently and be more productive in the lab. Waters continues to invest in technologies and chemistries to provide better methods for food safety.”

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