Multi-residue Analysis of PPCPs in Water

Personal care products (PPCPs) include a wide range of chemicals. PPCPs and its metabolites continue to enter the environment and are generally detected in surface water, groundwater and drinking water. Their concentration is very low, usually at the level of ng/L~μg/L, posing potential risks to water environment quality and ecosystem safety.

Due to the wide variety of PPCPs, their physical and chemical properties, biological activities and other properties are different, and their concentration in water is low. Therefore, the detection method adopted must be able to shield the interference of a large number of other impurities and have sufficient sensitivity to low concentration. To date, there is no universally adopted method for the analysis of PPCPs in the water. If the detection limit of ng/L level or lower is expected, the samples must be enriched with high multiple (100~10000 times) and the highly sensitive detection method should be adopted.

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Extraction and Enrichment

Sample concentration and enrichment is a key part of PPCPs analysis, and the selection of methods will affect the sensitivity and accuracy of the whole test program. For Liquid samples, the usual extraction methods are Liquid-Liquid Extraction (LLE), Solid Phase Extraction (SPE) and Solid Phase Microextraction (SPME). LLE can be used for non-polar and semi-polar analysis of liquid samples. LLE has been applied to the analysis of steroids and anti-inflammatory drugs in water samples. SPE has replaced many classic LLE methods and become one of the most commonly used methods to enrich PPCPs in water. SPME, which can be viewed as a miniature version of classic SPE, has been applied to the analysis of drugs and estrogen.

Purification

The analyte is separated from the interference matrix component by LLE or SPE, but in many cases the interference matrix component remains in the sample after extraction. In this case, advanced purification steps such as silica gel column (SGC) or gel permeation chromatography (GPC) must be used.

SGC: silica gel can remove the polar co-extraction matrix with strong retention value (such as protein in biological tissue, humic acid, fatty acid, etc.). The solid phase extract was transferred to a single silica gel column, the analyte was cleaned with appropriate solvent to extract, and the substrate impurities were retained on the adsorbent material.

GPC: this method separates the analyte according to its molecular size. At present, various types of materials with different apertures are used. When the analyte passes through the gel permeation chromatographic column, the large molecule cannot pass through the pore while the small molecule can pass and intercept. Therefore, large molecules are washed out before small ones.

Analysis Methods

Analysis methods currently used of PPCPs in water have Gas Chromatography/ Mass Spectrometry (GC/MS) and Liquid Chromatography/ Mass Spectrometry (LC/MS), etc.

GC/MS is the most commonly used high-sensitivity method for the detection of volatile and semi-volatile organics. It can be used for both quantitative and qualitative analysis and can meet the requirements of trace organics analysis. GC/MS has a high separation efficiency and is able to obtain abundant information about chemical structure from trace samples. It can not only separate organics with complex and multi-component traces, but also further enhance the ability of mass spectrometry identification. T. A. Ternes et al. used GC/MS to detect the activated sludge and freshwater sediments from domestic sewage treatment plants, indicating that the average recovery rate of estrogen mainly exceeded 70% in sludge and 90% in sediments. The results showed that the GC/MS was effective in quantitative and qualitative analysis of samples, as well as been widely used.

Since the 1990s, HPLC/MS has been widely used based on the development of strong interfaces. Because PPCPs often contain polar functional groups or are subject to thermal instability, they must be derivatized before they are analyzed by gas chromatography. Liquid chromatography does not require derivatization, makes up for the deficiency of gas chromatography in the analysis of polar substances. Jeffery D. Calhill et al. used HPLC/MS to routinely detect surface water and groundwater in the United States, and detected 22 different types of drugs with a recovery rate of more than 60%, method of the detection limit was 0.022μg/L. They found that the HPLC/MS can analyze polar substances well.

References

• T. A. Ternes, H. Andersen, D. Gilberg, et al. (2004) ‘Determination of estrogens in sludge and sediments by liquid extraction and GC/MS/ MS’, Analytical Chemistry, 74(14): 3498-3504.

• Edward T. Furlong, Jeffery D. Cahill, Mark R. Burkhardt, et al. (2004) ‘Determination of pharmaceutical compounds in surface- and ground-water samples by solid-phase extraction and high- performance liquid chromatography-electrospray ionization mass spectrometry’, Journal of Chromatography A,1041: 171- 180.

• B. J. Vanderford, R. A. Pearson, D. J. Rexing, et al. (2003) ‘Analysis of endocrine disruptors, pharmaceuticals, and personal care products in water using liquid chromatography/tandem mass spectrometry’, Analytical Chemistry, 75(22): 6265-6274. ?

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