Chlorate (ClO3-) is formed as a by-product when using chlorine, chlorine dioxide or hypochlorite for disinfection (European Food Safety Authority (EFSA), 2015). The presence of chlorate in food can arise from the use of chlorinated water for food processing and the disinfection of food-processing equipment (European Food Safety Authority (EFSA), 2015).
Perchlorate (ClO4−) is a chemical pollutant, which is released into the environment from natural and man-made sources (European Food Safety Authority (EFSA), 2014). Perchlorates are mainly derived from the use of natural fertilizers containing perchlorates (Cao et al., 2019; Du et al., 2019), industrial emissions of perchlorates (especially from the use of ammonium perchlorate in rocket and missile solid propellants) (Song et al., 2019; Lumen & George, 2017; Gan et al., 2015; Du et al., 2019) and naturally formed perchlorates in the atmosphere and surface water (European Food Safety Authority (EFSA), 2014). Perchlorate in foods of animal origin mainly come from the intake of food and feed containing perchlorate by animals. Perchlorate in plant-based foods mainly come from soil or irrigation water containing perchlorate. Processed foods could be contaminated with perchlorate during processing.
In 2014, the European Food Safety Authority (EFSA) assessed the public health risks of perchlorate in foods, especially fruits and vegetables, and found that acute exposure to perchlorate had no adverse effect on human health (except for fetal and infant health) (European Food Safety Authority (EFSA), 2014);Chronic exposure could cause long-term inhibition of thyroid uptake of iodine, lead to the development of toxic multinodular goitre and result in hyperthyroidism (Cao et al., 2019; European Food Safety Authority (EFSA), 2014; Pleus et al., 2018); In 2015, the risks to human health related to the presence of chlorate in food were assessed by the EFSA Panel on contaminants in the food chain (European Food Safety Authority (EFSA), 2015). The critical acute effect in humans identified in cases of poisoning is induction of methaemoglobinaemia, followed by lysis of red blood cells that can lead eventually to renal failure (European Food Safety Authority (EFSA), 2015; Al-Otoum et al., 2016). The chronic exposure harm of chlorate was consistent with that of perchlorate, Inhibition of iodine uptake in humans was identified as the critical effect for chronic exposure to chlorate (European Food Safety Authority (EFSA), 2015). A tolerable daily intake (TDI) of 3 µg/kg b.w. was set by read across from a TDI of 0.3 µg/kg b.w. derived for this effect for perchlorate, multiplied by a factor of 10 to account for the lower potency of chlorate (European Food Safety Authority (EFSA), 2015). In 2017, the European Food Safety Agency (EFSA) assessed the dietary exposure of perchlorate in European population, and found that the exposure of perchlorate in all age groups might possibly exceed the daily tolerance intake in Europe (European Food Safety Authority (EFSA), 2017). The maximum levels of chlorate and perchlorate in certain foods was amended by commission regulation (EU) 2020/749 (European Commission 749, 2020) and (EU) 2020/685 (European Commission 685, 2020), respectively.
For detection of chlorate and perchlorate in foods, several methods had been developed using ion chromatography (IC) (Sungur & Sangun., 2011; Canas et al., 2006; Niemann et al., 2006), ion chromatography-tandem mass spectrometry (IC - MS/MS) (Zhang et al.,2007; Aribi et al., 2006; Martinelango et al., 2006;Melton et al., 2019; Yang et al.,2011), liquid chromatography coupled to mass spectrometry (LC - MS) or liquid chromatography-tandem mass spectrometry (LC - MS/MS) (Xian et al., 2017; Constantinou et al., 2016; Zhao et al., 2018). The sensitivity of ion chromatography was low and the anti-interference ability was weak. The sample pretreatment in ion chromatography was complicated. Compared with IC - MS/MS, liquid chromatography coupled to a triple quadrupole mass spectrometry (LC - QqQ - MS/MS) had been widely used for its applicability and high sensitivity.
In this study, the analytical method of chlorate and perchlorate was improved by optimizing the method of instrument and sample pretreatment such as mobile phase, chromatographic column injection volume, extraction, and purification. Then, the improved method was validated and analyzed in drinking water and 16 types of foods. The performance of the method was compared with the published method (Table 1).
Table 1
The comparison of the developed method with previous reported methods.
Matrix | Detection method | Chlorate | Perchlorate | References |
LOD /µg/L(µg/kg) | LOQ/µg/L(µg/kg) | Recovery/% | RSD/% | Retention time/min | LOD /µg/L(µg/kg) | LOQ/µg/L(µg/kg) | Recovery/% | RSD/% | Retention time/min |
Flour | LC-MS/MS | - | - | - | - | - | 0.1 | 2.0 | 84.6–104.9 | 2.9–8.2 | 2.9 | Xian et al. (2017) |
Drinking water | LC-MS/MS | - | 10 | - | - | - | - | 5.0 | - | - | - | Constantinou et al. (2019) |
Fruit and vegetables | LC-MS/MS | - | 50 | 86.8–113 | 5.1–24.6 | 4.3 | - | 50 | 87.2–111 | 2.2–14.9 | 5.9 | Constantinou et al. (2019) |
Baby food | IC-HRMS | - | 2.0 | 85.0-105 | 8.0–11.0 | 12.0 | - | 2.0 | 78.0-108 | 8.0–12.0 | 23.4 | Panseri et al. (2020) |
Ozonated saline | IC-MS | 0.10 | 0.33 | 82.7–97.4 | 0.81–3.5 | 14.2 | 0.04 | 0.13 | - | 9.0–12.0 | 21.0 | Yin et al. (2020) |
Tea | UPLC-MS/MS | - | - | - | - | - | 1.0 | 10 | 79.2–105 | 1.3–16.3 | 1.7 | Liu et al. (2019) |
Drinking water | UPLC-MS/MS | 0.06 | 0.20 | 96.5–109 | 4.8 | 4.6 | 0.015 | 0.05 | 99.3–111 | 2.1 | 2.2 | This paper |
Fresh food | UPLC-MS/MS | 1.8 | 6.0 | 86.5–103 | 2.5–7.4 | 0.31 | 1.0 | 91.3–111 | 2.6–7.9 |
dry food | UPLC-MS/MS | 5.4 | 18.0 | 0.91 | 3.0 |
Note: -: not reported. |