Improving Speed, Sensitivity and Accuracy of Baby Food Analysis With Triple Quadrupole ICP-MS
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Food contains an abundance of nutritional elements, such as calcium, potassium and phosphorus, that are essential for proper bodily function and growth. Alongside these, food can also contain heavy metal contaminants such as arsenic, mercury and lead. These toxic elements can occur either naturally (as a result of them being absorbed from the soil in which the foodstuff is grown) or be introduced through contamination during production, and can cause negative effects on human health. Children are particularly vulnerable to these toxins due to their low body mass and underdeveloped immune systems. A study showed that daily exposure to even small quantities of toxic elements can lead to brain function decline and other negative long-term effects in children.
Based on these health concerns, it is essential to be able to accurately determine levels of different elements in foods intended for babies and young children to ensure that they are safe for consumption. In this article, we outline the current regulations regarding heavy metal contamination, and how triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS) can help quantify both nutrients and toxins to meet these regulations and support human health.
The importance of accurate and sensitive determination
To protect consumers, there are stringent limits on the quantities 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 US, and GB-2762-2017 in China. Due to the vulnerability of infants, the specific European regulations EC 609/2013 and EC 1881/2006 have set very low limits for arsenic, lead and cadmium in food for babies and young children. These stricter regulations are expected to be adopted worldwide, as illustrated by the Baby Food Safety Act of 2021, which proposes extremely low levels of elements such as lead and mercury.
Globally, the lowest current limits for toxic elements set in the above-mentioned 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 (that are likely to decrease further), highly sensitive techniques are required to ensure that samples comply with regulations and protect consumers. In addition, food is a very complex matrix with many different components. Analytical methods must therefore be able to detect and correct any interferences caused by this sample matrix to truly be capable of quantifying accurate levels of toxins in baby food.
The false positive problem
Single quadrupole ICP-MS is a generally accepted standard technique for analyzing nutrients and toxic elements in food. This approach routinely provides elemental analysis in a wide range of samples and facilitates high sample throughput through rapid sample scanning. However, false positives in the data may occur using this technique, reducing confidence in the results. For example, molybdenum and tungsten in the samples can form 95Mo16O+ and 186W16O+ interferences in the ICP which cause false positive results for 111Cd and 202Hg. While a kinetic energy discrimination approach can generally be used to reduce the effect of polyatomic interferences, this approach is less efficient for those interferences with masses larger than 100 amu. In addition, obtaining accurate results with single quadrupole ICP-MS can be time consuming, as multiple operation modes need to be used to measure all elements. Therefore, techniques that have improved sensitivity and accuracy are essential for meeting regulatory performance requirements.
Improved analysis with triple quadrupole ICP-MS
Triple quadrupole ICP-MS is a promising approach that can overcome the drawbacks of single quadrupole ICP-MS, offering many benefits when used for baby food detection. Most notably, the technique is highly sensitive and accurate as it has enhanced interference removal capabilities compared to single quadrupole ICP-MS. This is because it can be operated with oxygen collision/reaction cell gas, which removes the MoO+ and WO+ interferences on Cd and Hg mentioned earlier (as well as removing 40Ar35Cl+ interference on 75As) thereby eliminating false positive results. The technique has a similar linear dynamic range to single quadrupole ICP-MS, being capable of measuring from 0.005 μg kg-1 to 100,000 μg kg-1 for major elements, meaning that all target elements can be analyzed in one run without any extra dilution or calibration steps. However, use of a single operation mode means the method can achieve high accuracy in less time.
Accurate and sensitive results
A single method was recently developed for the analysis of 30 elements (both toxic and nutritional) present in baby foods, using triple quadrupole ICP-MS (Table 1). Ten different commercially available baby food samples were analyzed by this method, including milk powders, purees and cereals.
Detection limits of 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 quantitation (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 method validity and accuracy were determined, giving results between 85–120% of the certified concentration. Finally, excellent run times of 1 minute 19 seconds per sample were achieved, giving a sample throughput comparable to that of the single quadrupole ICP-MS method.
Table 1: Compositions of ten different baby food samples analyzed by triple quadrupole ICP-MS. Values of the toxic heavy metals As, Cd, Hg, and Pb (in blue) are in μg kg-1, and all other values are in mg kg-1.
<DL = below detection limit. N.A. = not applicable.
Improving baby food safety
Triple quadrupole ICP-MS is a valuable tool for analyzing a host of essential nutrients and harmful heavy metals in baby food in a single analysis. The method is accurate, sensitive and rapid, making it perfect for high throughput testing laboratories. This approach will support laboratories to quantify these elements to meet increasingly stringent requirements, both now and in the future, and ensure food safety for children and babies for generations to come.
About the authors:
Dr. Sukanya Sengupta is an application specialist for ICP-OES and ICP-MS at Thermo Fisher Scientific.
Dr. Daniel Kutscher is a product specialist for ICP-MS at Thermo Fisher Scientific.
