Enantioselective LC-MS/MS for anthropogenic markers of septic tank discharge

Abstract

Households in rural locations utilize septic tanks for wastewater treatment and can cause surface water contamination. A new methodology was developed to help investigate the role septic tanks play in the dissemination of prescription and over-the-counter drugs, personal care products and stimulants in the aqueous environment. Simultaneous analysis of 16 chiral and achiral anthropogenic markers was achieved using a Chirobiotic V2® enantioselective column in polar ionic mode. The optimized method achieved quantitation limits for 16 compounds in the range 0.001–2.9 μg L−1 and 0.0002–0.43 μg L−1 for septic tank effluent and stream water, respectively. Application of the method to samples collected in North East Scotland found caffeine to be ubiquitous in all samples studied suggesting it as a good indicator of septic tank discharge. In rural streams studied, concentrations of all prescription drugs investigated were ≤0.02 μg L−1. However, analgesics and stimulants were at high concentration in one location indicating direct discharge of septic tank wastewater (i.e., not dissipated through a soak away). For example, paracetamol, cotinine and caffeine were measured at 1100 μg L−1, 31 μg L−1 and 200 μg L−1, respectively, which is comparable to septic tank effluents. Furthermore, S(+)-amphetamine and R(−)-amphetamine were present in this stream sample at 0.20 and 0.27 μg L−1. This corresponds to an enantiomeric fraction of 0.43, which is typical of untreated wastewaters in the UK. Findings illustrate further study on the diffuse impact of septic tanks to surface water is needed and can be supported using this new multi-residue enantioselective method.