Application of comprehensive two-dimensional gas chromatography coupled with mass spectrometry in screening of emerging contaminants

In recent years, many new synthetic chemicals have emerged. When these chemicals are used, contaminants are released into the environment, posing a threat to the ecosystem and human health. However, information on the risks of some contaminants is limited or missing. Thus, the human health effects of unknown toxic contaminants might be overlooked. Hence, identifying emerging contaminants with high environmental risk is crucial. With the advent of high-resolution mass spectrometry (HRMS), complex compounds in the environment can be identified, fulfilling a prerequisite for screening priority contaminants with high toxicity and potential risk. Comprehensive two-dimensional gas chromatography (GCxGC) has a large peak capacity and strong separation ability, and is suitable for separating and analyzing complex samples. As a result, it has been increasingly used in conjunction with HRMS for screening emerging contaminants in the environment. This paper reviews the screening methods for emerging contaminants by comprehensive two-dimensional gas chromatography coupled with mass spectrometry. These screening methods are divided into two types: Nontarget analysis and suspect screening. The screening workflow of the aforementioned methods consists of five steps: sample preparation, instrumental analysis, data processing, substance identification, and risk assessment. Furthermore, the applications for screening emerging contaminants in various matrices by comprehensive two-dimensional gas chromatography coupled with mass spectrometry since 2013 are summarized, including water, air, soil, sediment, and organisms. Water samples include drinking water, surface water, wastewater, rainwater, cloud water, and snow. Many corresponding pretreatment techniques have been developed to extract as many compounds as possible. The main emerging contaminants that are typically screened include pharmaceuticals and personal care products, phenolic compounds, and polycyclic aromatic hydrocarbons (PAHs). Air samples refer to gas and particle phases. PAHs other than the 16 PAHs listed by the U.S. Environmental Protection Agency are often the subject of screening. Several other contaminants are also commonly screened, including organonitrogen compounds, halogenated organic compounds (HOCs), and the compounds from the Toxcast database. Soil and sediment samples are commonly the most contaminated. The matrix of soil and sediment is complex, and there are many types of contaminants. GCxGC enables separation of these complex compounds. PAHs, N-containing compounds, and HOCs are commonly screened most frequently. Finally, studies on screening biological samples for emerging contaminants are summarized. There are few studies on human samples, and only few pertinent studies have been conducted on breast milk and human urine. Regarding other biological samples, most studies have screened HOCs in marine organisms, ranging from plankton at low trophic levels to dolphins at high trophic levels. Then, the challenges and solutions of screening for emerging contaminants are presented. Finally, screening of emerging contaminants by comprehensive two-dimensional gas chromatography coupled with mass spectrometry is an active area of environmental research. For example, comprehensive two-dimensional gas chromatography coupled with mass spectrometry can identify emerging contaminants in contaminated sites. The identified compounds can be included in the list of priority emerging contaminants in a manner that provides a basis for national efforts to control emerging contaminants. Furthermore, screening for emerging contaminants by comprehensive two-dimensional gas chromatography coupled with mass spectrometry can be combined with chemical environmental risk assessments. The toxicity of identified high-level or high detection frequency compounds can be predicted by quantitative structure-activity relationship or other models. Environmental risk assessment of such compounds, based on their toxicity and concentration, enables screening of high-risk contaminants.