cooking-oilWe’ve blogged previously about the importance of robust gas chromatography (GC) workflows to ensure food oils are free from pesticides, contaminants and cheaper oil adulterants. But even once the pure product is safely in the bottle, there’s another family of analytes that the food safety labs need to screen for – and it’s the bottle that’s the problem.

Phthalate acid esters, more commonly known as phthalates, are widely used as plasticizers to increase the flexibility of plastics used in food packaging and other food contact materials (FCMs). However, because these compounds are not chemically bound to the parent polymer matrix, they can transfer from the material into the food products they come into contact with, potentially in significant amounts.

Robust GC-MS phthalate screening in food testing workflows

Growing evidence links phthalates to a wide range of human health problems. Classified as endocrine disruptors, phthalates can effectively mimic hormones and alter the normal function of the endocrine system. As a result, phthalates have been associated with a range of fertility issues, as well as the development of autism in children.

To safeguard consumer health, global food safety agencies have established guidelines to control phthalate transfer from FCMs into foodstuffs. The European Food Safety Authority, for example, has set limits for specific migration of chemicals in plastic material intended to come in contact with food at 0.1 percent in final FCM products. Similarly, regulatory bodies in China and Taiwan have set limits of one part per million (ppm) in food products, corresponding to 1000 μg/kg.

To accurately quantify phthalates at these low levels, food testing laboratories require highly sensitive and robust analytical techniques, capable of tolerating a broad range of food matrices. On-going improvements in GC-MS technologies are delivering more sensitive, selective and robust phthalate testing workflows.

Sensitive GC-MS analysis of phthalates in cooking oil

Due to their lipophilic nature, phthalate contamination is a particular problem for fatty foods such as cooking oil. Studies have revealed consistently high levels of phthalates in vegetable oils sold in North America, Europe and Asia consumer markets.

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GC-MS analysis of phthalates in cooking oils can present a significant challenge for food testing laboratories. Vegetable oils contain complex mixtures of triacylglycerides, making samples difficult to chromatograph and analyze. The presence of easily ionizable matrix compounds means distinguishing phthalate analytes from background ions can be extremely challenging, especially using full-scan acquisition workflows.

One way to reduce this complexity is by using selective ion monitoring (SIM) acquisition methods. Timed-SIM is an excellent choice for quantitative phthalate analysis as it enables more sensitive analyte detection, and because data is obtained only for specific masses of interest, rather than across the full mass range, spectral complexity is significantly reduced.

To demonstrate the power of SIM acquisition, we recently evaluated the performance of the Thermo Scientific ISQ 7000 single quadrupole AEI GC-MS system for sensitive phthalate determination in vegetable oil. By optimizing scan rates and dwell times using Thermo Scientific Chromeleon Chromatography Data System software, phthalates such as di-(2-ethylhexyl)-phthalate (DEHP) and dibutylphthalate (DBP) were detected at levels as low as 0.01 ng/mL (0.1 μg/kg). Estimated limits of quantitation for various key phthalate analytes ranged from 5 to 25 µg/kg.

Underpinning this exceptional sensitivity and selectivity is the system’s advanced electron ionization (AEI) source. Its innovative source geometry leads to increased ionization efficiency and a narrower ion beam. The enhanced sensitivity achieved using the AEI source enabled the use of more dilute samples and increased split ratios, minimizing contamination in the GC flow path. This reduced the need for extensive (and expensive) sample preparation, as well as instrument maintenance and consumable replacement.

The latest GC-MS workflows are playing a powerful role in protecting consumers from the health risks associated with food packaging materials. Thanks to AEI sources and timed-SIM acquisition techniques, these workflows are providing the levels of sensitivity, selectivity and robustness that modern food testing standards demand.

Learn more about sensitive, selective and robust phthalate quantitation in cooking oils by downloading our application note ‘Routine determination of phthalates in vegetable oil by single quadrupole GC-MS.’