UHPLC–MS/MS Used to Characterize Contaminants in Water and Solids

A recent study from scientists at Henan Normal University and the Yellow River Conservancy Technical Institute in Henan, China explored how quaternary phosphonium compounds (QPCs) and phosphine oxides (POs) were characterized in water and solid samples using ultrahigh performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS). Their findings were published in the Journal of Chromatography A (1).

Jiuzhaigou scenery, China - June 15, 2017: this is located in China's jiuzhaigou scenic area, a famous tourist destination in China.Most of it is pristine. The color of the lake is the color of nature. | Image Credit: © ChuanSheng - stock.adobe.com

One of the critical environmental issues affecting human existence and global biodiversity is the increasing contamination of water systems with emerging contaminants (ECs). ECs are synthetic or naturally occurring chemicals or microorganisms that, while not commonly monitored, can potentially enter the environment and cause known or suspected adverse effects on the environment and human health (2). ECs have become a global concern due to their potential risks to humans and aquatic ecosystems, even at very low concentrations. Increasing environmental ECs result primarily from human activities, including industrial discharge, untreated sewage discharge, household and municipal wastewater discharge, and modern agricultural practices. This has led to various classes of ECs, such as pharmaceuticals, personal care products, and microplastics, have been discovered in aquatic environments.

In 2015, a new class of ECs was identified in Germany: quaternary phosphonium compounds (QPCs), the scientists wrote. QPCs are chemicals primarily applied to synthesize alkenes by the chemical industry. Further, other special QPC applications, such as phase transfer catalysts and ionic liquids (IL), have been reported. Though there have been studies published about QPCs, minimal research has been conducted on their environmental presence as contaminants; rather, they have all focused on their syntheses and properties. However, QPC occurrence in German water and land has been studied. Environmental QPC environment is probably related to the occurrence of phosphine oxides (POs), which are phosphorus compounds with the formula OPX3 (3). POs are one of the most frequently used groups of photoinitiators (PIs), with PI contamination, including POs, having been reported in food packaging materials, indoor dust, and breast milk.

In this study, a method for quantifying QPCs and POs in multiple environmental media was developed using UHPLC–MS/MS. Analytes were extracted from water samples using solid-phase extraction, with ultrasonic extraction being used for the solid samples. According to the scientists, this approach is more suitable for quantitatively analyzing compounds than other previously established analytical methods, in addition to having high sensitivity.

The method quantification limit reached 0.12–2.55 ng⋅L^–1 in water samples and 0.004–0.10 ng⋅g^–1 in solid samples. The recoveries of target analytes spiked at low, medium, and high concentrations in water and solid samples ranged from 56.4–120%, with relative standard deviations being below 20% (n = 6). Further, the validated method was able to apply to the analysis of eight QPCs and four POs in real environmental samples. The UHPLC–MS/MS method’s sensitivity was optimized, detecting QPCs in wastewater, sludge, and road dust for the first time. This method shows great promise in environmental analysis; further, the evidence shows that QPCs and POs deserve more attention, with the proposed method being valuable to future research into these substances’ presence in the environment.

References

(1) Guo, S.; Zhang, C.; Li, B.; Zhang, F.; Han, J.; et al. Simultaneous Determination of Quaternary Phosphonium Compounds and Phosphine Oxides in Environmental Water and Solid Samples by Ultrahigh Performance Liquid Chromatography–Tandem Mass Spectrometry. J. Chromatogr. A 2024, 1733, 465280. DOI: 10.1016/j.chroma.2024.465280

(2) Emerging Contaminant. Elsevier B.V. 2024. https://www.sciencedirect.com/topics/earth-and-planetary-sciences/emerging-contaminant (accessed 2024-8-23)

(3) Phosphine Oxide. Haz-Map 2024. https://www.haz-map.com/Agents/16591 (accessed 2024-8-23)