Improved Speed, Sensitivity, and Accuracy of Baby Food Analysis with Triple Quadrupole ICP-MS

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Foods contain an abundance of nutrients, such as calcium, potassium and phosphorus, which are essential for the proper functioning and growth of the body. Along with this, foods can also contain heavy metal contaminants such as arsenic, mercury, and lead. These toxic elements can either occur naturally (as a result of absorption from the soil in which the food is grown) or be introduced through contamination during production, and can have negative effects on human health. Children are particularly vulnerable to these toxins due to their low body mass and underdeveloped immune system. A study has shown that daily exposure to even small amounts of toxic elements can lead to a decline in brain function and other long-term negative effects in children.

Based on these health concerns, it is essential to be able to accurately determine the levels of different elements in foods intended for babies and young children to ensure that they are safe for consumption. In this article, we describe current regulations regarding heavy metal contamination and how triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS) can help quantify nutrients and toxins to meet these regulations and support the human health.

The importance of an accurate and sensitive determination

To protect consumers, there are strict limits on the amounts of toxic elements in food. These vary from country to country, and several regulations exist to define these limits: for example the Federal Food, Drug, and Cosmetic Act (FDCA) in the United States, and GB-2762-2017 in China. Due to the vulnerability of infants, specific European regulations EC 609/2013 and EC 1881/2006 have set very low limits for arsenic, lead and cadmium in foods for babies and young children. These stricter regulations should be adopted worldwide, as illustrated by the Baby Food Safety Act of 2021which offers extremely low levels of elements such as lead and mercury.

Globally, the current lowest limits for toxic elements set in the aforementioned regulations are 10 μg kg-1 for arsenic, 5 μg kg-1 for cadmium and lead, and 2 μg kg-1 for mercury. With such low limits (which are likely to decrease further), very sensitive techniques are required to ensure that samples comply with regulations and protect consumers. Moreover, food is a very complex matrix with many different components. Analytical methods must therefore be able to detect and correct for interferences caused by this sample matrix to be truly able to accurately quantify toxin levels in baby food.

The problem of false positives

Single quadrupole ICP-MS is a generally accepted standard technique for the analysis of nutrients and toxic elements in foods. This approach consistently provides elemental analysis in a wide range of samples and facilitates high sample throughput through rapid sample scanning. However, false positives in the data can occur using this technique, reducing confidence in the results. For example, molybdenum and tungsten in samples can form 95month16O+ and 186O16O+ interferences in the ICP that cause false positive results for 111CDs and 202Hg. While a kinetic energy discrimination approach can generally be used to reduce the effect of polyatomic interference, this approach is less effective for interference with masses greater than 100 amu. Additionally, obtaining accurate results with a single quadrupole ICP-MS can be time-consuming, as multiple modes of operation must be used to measure all elements. Therefore, techniques that have improved sensitivity and accuracy are essential to meet regulatory performance requirements.

Improved analysis with triple quadrupole ICP-MS

Triple quadrupole ICP-MS is a promising approach that can overcome the disadvantages of single quadrupole ICP-MS, providing many advantages when used for baby food detection. Most notably, the technique is highly sensitive and accurate as it has improved interference elimination capabilities compared to single quadrupole ICP-MS. This is because it can be used with oxygen collision/reaction cell gas, which removes MoO+ and WO+ interferences on Cd and Hg mentioned previously (as well as the suppression 40Ar35CL+ interference on 75As) thus eliminating false positive results. The technique has a linear dynamic range similar to that of single quadrupole ICP-MS, being able to measure from 0.005 μg kg-1 at 100,000 μg kg-1 for major elements, which means that all target elements can be analyzed at once without any additional dilution or calibration steps. However, using only one mode of operation means that the method can achieve high accuracy in less time.

Accurate and sensitive results

A unique method has recently been developed to analysis of 30 elements (toxic and nutritional) present in baby food, using an ICP-MS triple quadrupole (Table 1). Ten different samples of commercially available baby foods were analyzed by this method, including powdered milks, purees and cereals.

Detection limits below 1 μg L-1 were achieved for 29 of the elements analyzed, and 1.5 μg L-1 for calcium. The minimum limit of quantification (MLOQ) of As, Cd, Hg, and Pb in real samples was at least 70% lower than global regulatory limits, showing the method’s exceptional sensitivity and suitability for future stringent regulations. The validity and accuracy of the method have been determined, giving results between 85 and 120% of the certified concentration. Finally, excellent run times of 1 minute 19 seconds per sample were achieved, giving comparable sample throughput to the single quadrupole ICP-MS method.

Table 1: Compositions of ten different baby food samples analyzed by triple quadrupole ICP-MS. The values ​​of the toxic heavy metals As, Cd, Hg and Pb (in blue) are in μg kg-1and all other values ​​are in mg kg-1.

Improving baby food safety

The Triple Quadrupole ICP-MS is a valuable tool for analyzing a multitude of essential nutrients and harmful heavy metals in baby food in a single analysis. The method is accurate, sensitive, and fast, making it perfect for high-throughput testing labs. This approach will help laboratories quantify these elements to meet increasingly stringent requirements, now and in the future, and ensure the food safety of children and babies for generations to come.

About the authors:

Dr Sukanya Sengupta is an ICP-OES and ICP-MS Application Specialist at Thermo Fisher Scientific.

Dr Daniel Kutscher is an ICP-MS product specialist at Thermo Fisher Scientific.

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