Detecting Organotin in Food Using Chromatography

Organotin compounds are man made compounds that can find their way into the environment and the food we eat. They have many different uses ranging from keeping ships hulls clear of barnacles to biocides and glass coatings. It is important that we can ensure our foods are clear of contaminants, especially ones that can potentially cause us harm. A recent paper - published in the Journal of Chromatography A - reports on a newly developed method of testing for organotin compounds using chromatography.

No barnacles here

The five main uses of organotin compounds are biocides, PVC coatings, catalysts, agrochemicals and glass coatings. Perhaps the most widely known organotin compound is tributyltin (TBT) - it is used in marine antifoulant paints to stop the growth of organisms such as barnacles on the hulls of ships. This use has led to TBT being found in both marine and freshwater environments all over the world. Recent studies have shown that TBT in these environments has caused reproductive damage to several species of marine organisms.

Organotin compounds are simply organic compounds that have tin atoms bonded to carbon atoms. The bond between carbon and tin is relatively stable, which is useful in the products they are used in to make them long-lasting and stable. But unfortunately, this means that the organotin compounds can also persist in places where they are less welcome and where they can cause damage and harm.

Improving GC and LC methods

Historically, both gas and liquid chromatography are used to analyse samples for organotin compounds. But they both have their deficiencies. Before gas chromatography can be used, the organotin compounds have to be changed into a form that can be separated by GC, and this is a complex and time-consuming step.

Liquid chromatography can also be used to analyse samples for organotin compounds, but LC should be coupled with mass spectrometry to get the sensitivity required for organotin compounds. The use of LC-MS is discussed in the article, SFC-MS versus LC-MS - advantages and challenges. But a new method developed by researchers - and reported in the paper referenced above - uses liquid chromatography but without the need for MS.

Chromatography with spectroscopy to detect the tin

The team of Chinese researchers based the method on atomic emission spectroscopy. This analysis is based on analysing the spectra of infrared light emitted by compounds when they are excited by a flame or plasma. The team first used liquid chromatography to separate a sample into its constituents using hydrochloric acid in the mobile phase.

The team analysed several foods including chicken, lettuce and tomatoes. Although they didn’t detect organotin samples in unadulterated samples, the method did detect organotin compounds in food samples that were spiked with organotin compounds.