Acrylamide and Other Toxic Substances Detected in Soil Using LC–MS/MS

Scientists from the International Corporate Accountability Roundtable (ICAR), mainly the Indian Agricultural Research Institute in New Delhi, India, have developed a new method using liquid chromatography tandem mass spectrometry (LC–MS/MS) for detecting trace amounts of acrylamide and other toxic substances in sandy loam soil. Their findings were published in the Journal of Chromatography A (1).

sandy loam soil ground By Dmytro - stock.adobe.com

Superabsorbent polymers (SAP) are crosslinked hydrophilic polymers or hydrogels comprising of a network of cross-linked polymer chains. When added into light textured soils like sandy loam soil, SAPs can alter the hydro-physical properties, increase the water holding capacity, reduce erosion, runoff, and irrigation frequency. The hydrophilic network containing polar functional groups absorbs and retains large quantities of water, which makes SAPs extensively used materials for industrial and agricultural applications. Agricultural SAP chemically comprise of potassium polyacrylate or sodium polyacrylate crosslinked networks. Polyacrylamide hydrogel (PAM) has been established non‐toxic to humans, animals, fish, and plants, though the toxicity of its residual monomer (acrylamide) is a matter of concern.

Acrylamide is a known neurotoxin and putative human carcinogen that is widely used during the manufacturing of paper, dye, and other industrial products (2). If present in its free form during SAP synthesis, it can pose a risk of entering the food chain due to its high-water solubility. In 2020, the Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives (JECFA) concluded that acrylamide is a human health concern; further, studies have showed cancer appearing in animals exposed to acrylamide in very high doses (3). Similarly, N, N-Methylene-bis-acrylamide (MBA) is known to be toxic in its free form.

In this study, the scientists developed a method based around liquid chromatography tandem mass spectrometry (LC–MS/MS) for the analysis of acrylamide (AD), acrylic acid (AA) and N,N-methylene-bis-acrylamide (MBA) in sandy loam soil. These soil samples were amended by two test hydrogels, the Pusa Hydrogel and SPG 1118 hydrogel, and prepared using AD and MBA. The multiple reaction monitoring (MRM) transitions were optimized for both compounds. The soil samples were extracted using dispersive solid-phase extraction (dSPE) with a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) technique, employing acetonitrile. All analytes were quantified at trace levels within a five-minute run using ultrahigh-performance liquid chemistry (UHPLC) equipped with a C-18 column.

From there, single laboratory validation of the developed method in soil matrix was conducted based on specificity, linearity, sensitivity, accuracy, precision, matrix effect and measurement of uncertainty. LC-MS/MS exhibited a linear response in the concentration range of 0.001 to 1 µg mL⁻¹, with a correlation coefficient >+ 0.99. Further, groundnut and wheat grown with application of the hydrogels showed no detectable residues of monomers in soil samples (total n = 60) near the root zone at the time of crop harvesting. When the developed method was employed in a 24 h cycle, the analysts were able to process approximately 24 samples. Overall, the instrumental method could acquire 40–50 samples per day, including the run of calibration standards for quantification. With its high-throughput efficiency, according to the scientists, this method is believed to be qualified for being termed as robust methodology for routine application in monitoring the trace release of toxic monomers/cross-linkers in soils amended with hydrogels and thus assure environmental safety.

References

(1) Talaviya, H.; Singh, A.; Singh, N.; Manna, S.; Banerjee, T. Development and Validation of LC-MS/MS Method for Trace Analysis of Acrylamide, Acrylic Acid and N, N-Methylene Bis Acrylamide in Sandy Loam Soil. J. Chromatogr. A 2024, 1729, 465012. DOI: 10.1016/j.chroma.2024.465012

(2) Acrylamide. National Institute of Environmental Health Sciences 2024. https://www.niehs.nih.gov/health/topics/agents/acrylamide (accessed 2024-6-24)

(3) Acrylamide Questions and Answers. FDA 2024. https://www.fda.gov/food/process-contaminants-food/acrylamide-questions-and-answers (accessed 2024-6-24)