Analytical Methods for Measuring Endocrine Disruptors and Pharmaceuticals

Endocrine-disrupting compounds (EDCs) have been detected in natural waters globally. Additionally, trace concentrations of Pharmaceuticals and personal care products (PPCPs) have also been detected in various waters, primarily as the result of incomplete wastewater treatment. Some PPCPs are known to act as EDCs as they can have impacts on the endocrine systems of animals. The detection of EDCs and PPCPs in source water is of great concern since some of these compounds have known physiological responses at low concentrations. The majority of EDCs and PPCPs are more polar than traditional contaminants, such as polychlorinated biphenyls (PCBs) and organochlorine pesticides, and several have acidic or basic moieties. These properties, coupled with trace quantities, create unique challenges for both removal processes and analytical detection. There are two general approaches for monitoring EDCs and PPCPs in water: 1) direct measurement of target compounds via analytical instrumentation and 2) biological assays. The use of liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) has provided highly sensitive and selective analysis of a great diversity of emerging contaminants [1,2]. LC-MS/MS can also be advantageous as it does not require labor intensive derivatization for polar compounds that is necessary for traditional gas chromatography (GC) analysis and does not require additional sample clean-up or solvent transfer steps [3]. This presentation will describe using isotope dilution and LC-MS/MS for the analysis of EDCs and PPCPs. Samples are spiked with isotopically-labeled versions of target compounds and extracted using automated solid-phase extraction (SPE). The resulting extracts are analyzed by LC-MS/MS using both electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) in positive and negative modes. Isotopically labeled standards can be a useful tool for the correction of recovery loss, instrument variability and matrix suppression or enhancement [4]. Although APCI does not exhibit significant matrix suppression as compared to ESI, it can be less sensitive and compound dependent. Method reporting limits ranged from 0.25 – 10 ng/L in a variety of water matrices based on a 1 to 1000 concentration factor (Table 1). Percent recoveries ranged from 91 – 116% with percent relative standard deviations (%RSDs) from 0.7 – 10% for all three water matrices. Figure 1 illustrates how recovery loss from solid phase extractions in DI water can be corrected by the use of isotope dilution. Figure 2 compares occurrence data of pharmaceuticals detected in surface water that was quantified using external calibration versus isotope dilution. External calibration data appears to be suppressed by recovery loss and matrix suppression. This can result in data that underestimates environmental concentrations or reports them as non-detect. Although there are some limitations, LC-MS/MS using isotope dilution can be used to measure EDCs and pharmaceuticals in a variety of matrices with exceptional sensitivity and selectivity while generating data with better precision and accuracy.