Ultratrace Analysis in Food Safety

 Concern about Food Safety

Nowadays, food safety has gained increasing attentions, which is generally defined as a scientific discipline describing the ways of handling, preparation and storage of food products to prevent food-borne illness. Contaminants might be leaded into food products in diverse processes (production, transport and storage), such as the excessive use of pesticides or veterinary drugs, introduction of illegal additives to the food industry and toxin generation from the long-time storage.

The occurrence of these contaminants can enter the food chain and further cause potential risk to human health. Moreover, food safety is not only a hot topic to human health, but also concerns the international food trade. Therefore, ultra-trace analysis of the food contaminants is one of the most urgent tasks for food safety.

Ways Foods Can Be Contaminated

The classification of contaminants according to stages of the life cycle of foodstuffs is the most convenient, as it well agrees with the main critical control points of the control of the production process. The critical control points are stages of the assurance of the safety of foodstuffs at which measures aimed at the prevention, elimination, or decrease of danger to an acceptable level can be taken and remain important. The system of the control of the safety of foodstuffs based on hazard analysis and critical control points (HACCP) ensures control at all stages of the food production chain, at which a hazardous situation (including the contamination of foodstuffs) can arise, starting from the stage of the preparation of raw materials and finishing with the stages of storage and product sales.

Table: Ways of foodstuff contamination [1]

Monitoring of residual toxicant concentrations in foodstuffs is one of the most important aspects of the minimization of possible hazards to the health of the population. The basis for the assurance of the safety of food and its main tools are provided by the development of specific, sensitive, precise, reproducible, and available procedures for the quantitative chemical analysis of foodstuffs and raw materials with a possibility of the simultaneous determination of a great number of contaminants within one analytical cycle

How Fine is ‘Ultra-Trace’?

Analyses performed at parts per million (ppm) or microgram (μg) levels are generally defined as trace analyses - an analytical landmark that was attained approximately 30 years ago. Ultra-trace (ultra – beyond what is ordinary) analyses are defined as analyses performed below ppm or sub-microgram levels [2]. In biochemistry, an ultra-trace element is a chemical element that normally comprises less than one microgram per gram of a given organism (i.e. less than 0.0001% by weight), but which plays a significant role in its metabolism.

Why Ultra-Trace Analysis Is So Important?

Ultra-trace analysis is so much important for a better food screening that without performing it no food item can be called as ‘safe’ due to the toxins and heavy metals being present in the food items in such a little margin that it is quite impossible to detect them with traditional analytical methods, yet this little amount of heavy metal or toxin can cause diseases very much difficult to cure.

From Cr6+ to radioactive heavy metal contamination, plants and crops very much carries such hazardous materials due to the deleterious activity done by us humans on the environment. After the nuclear bombing on Hiroshima, all the crops that grow there contains highly radioactive elements, use of antibiotic and veterinary medicines and other industrial excretes used in the farming process cause foods to be very inimical to health. By the pragmatic application of ultra-trace analysis, it is possible to detect toxic substances that are present in a margin less than μg per kg of food sample.

As an example of how dangerous food poisoning is, we can look at the history, the poisoning of ‘methyl mercury’, also known as the ‘Minamata disease’, a neurological disease that even affect the fetus in its congenital form. From the first detection in 1956 till 2001, thousands of people have suffered and 1,784 have died [3]. It was caused by ‘Chisso Corporation’, situated at a bay in Japan, dumped mercury sulfate in the water which was turned into ‘methyl mercury’ by the fish and reached to people by it.

Highly reputed foodstuff manufacturing companies try to assure their consumers that their products are safe and as a proof they do explicit quality analysis before the products reach the market, by the use of ultra-trace analysis it is possible to even detect beyond trace amount of impurity, heavy metal and poisonous substances that are being produced during the manufacturing process, as mentioned above, which will eventually help them to improve their products and their business too.

Novel Methods in Ultra-Trace Analysis

There are several novel methods that have been developed by the scientists to ensure better screening of the food, most widely used methods are based on spectroscopy and chromatography. Beside these two, nanomaterials have also been developed to detect food toxins present in ultra-trace amount.

Carbon nanomaterials were endowed with strong affinity toward target analytes through pi-pi stacking and hydrophobic interaction. Carbon nanomaterials have been widely employed to enrich many kinds of contaminants, such as bisphenols A (BPA), aflatoxins (AFs), polyaromatic hydrocarbons (PAHs) and sulfonamides (SAs). The magnetic nitrogen doped carbon nanotube was prepared to detect bisphenol A in fruit juice [4]. As a new 2-D graphene analogue, graphitic carbon nitride (g-C3N4) has attracted increasing attentions in recent years. The g-C3N4 showed a highly π-conjugated structure, which made it as an adequate candidate to complement graphene in food analysis field.

Weller et al. [5]  developed a method for the determination of ultra-traces of radionuclides, including 134+137Cs, radiosilver and 9079 Sr and applied it to food samples obtained from Japan. The method is very groundbreaking for the people of Japan, since their foods are in high probability of getting contaminated by Fukushima-derived radionuclides.

ICP-MS is a very frequently used method to detect metals in the food sample. MS combining with HPLC and GC are now a very handy tool for ultra-qualitative analysis. Nagae et al.[6] developed an LC-MS/MS method to detect pacific siguatoxins in fish, with the detection limit being <0.01μg/kg. Scientists are still working long and hard to develop more facile methods in the field of food quality analysis.

References

1.  Amelin, V.G., Lavrukhina, O.I. Food safety assurance using methods of chemical analysis. J Anal Chem 72, 1–46 (2017).
2. S. Ahuja (1988) Trace and Ultratrace Analysis by HPLC, Journal of Liquid Chromatography, 11:9-10, 2175-2197,
3. Harada M. Minamata disease: methylmercury poisoning in Japan caused by environmental pollution. Crit Rev Toxicol. 1995; 25 (1):1-24.
4. Y. Zhang, G. Li, D. Wu, X. Li, Y. Yu, P. Luo, J. Chen, C. Dai, Y. Wu, Recent advances in emerging nanomaterials based food sample pretreatment methods for food safety screening, Trends in Analytical Chemistry
5. Weller A., Hori M., Shozugawa K. & Steinhauser G., Rapid ultra-trace determination of Fukushima-derived radionuclides in food, Food Control (2017),
6. Nagae, M., Igarashi, T., Mizukoshi, K., Kuniyoshi, K., Oshiro, N., & Yasumoto, T. (2021). Development and Validation of an LC-MS/MS Method for the Ultra-Trace Analysis of Pacific Ciguatoxins in Fish. Journal of AOAC International.