Results of an Interlaboratory Comparison of Analytical Methods for Contaminants of Emerging Concern in Water

Abstract

An evaluation of existing analytical methods used to measure contaminants of emerging concern (CECs) was performed through an interlaboratory comparison involving 25 research and commercial laboratories. In total, 52 methods were used in the single-blind study to determine method accuracy and comparability for 22 target compounds, including pharmaceuticals, personal care products, and steroid hormones, all at ng/L levels in surface and drinking water. Method biases ranged from <10% to well over 100% in both matrixes, suggesting that while some methods are accurate, others can be considerably inaccurate. In addition, the number and degree of outliers identified suggest a high degree of variability may be present between methods currently in use. Three compounds, ciprofloxacin, 4-nonylphenol (NP), and 4-tert-octylphenol (OP), were especially difficult to measure accurately. While most compounds had overall false positive rates of ≤5%, bisphenol A, caffeine, NP, OP, and triclosan had false positive rates >15%. In addition, some methods reported false positives for 17β-estradiol and 17α-ethynylestradiol in unspiked drinking water and deionized water, respectively, at levels higher than published predicted no-effect concentrations for these compounds in the environment. False negative rates were also generally <5%; however, rates were higher for the steroid hormones and some of the more challenging compounds, such as ciprofloxacin. The elevated false positive/negative rates of some analytes emphasize the susceptibility of many current methods to blank contamination, misinterpretation of background interferences, and/or inappropriate setting of detection/quantification levels for analysis at low ng/L levels. The results of both comparisons were collectively assessed to identify parameters that resulted in the best overall method performance. Liquid chromatography-tandem mass spectrometry coupled with the calibration technique of isotope dilution were able to accurately quantify most compounds with an average bias of <10% for both matrixes. These findings suggest that this method of analysis is suitable at environmentally relevant levels for most of the compounds studied. This work underscores the need for robust, standardized analytical methods for CECs to improve data quality, increase comparability between studies, and help reduce false positive and false negative rates.

Interlaboratory comparison of in vitro bioassays for screening of endocrine active chemicals in recycled water

“…Interlaboratory agreement for targeted chemical analyses using environmental samples can range from single digit to more than 50% RSD, depending on the analyte, matrix and measured concentration (Vanderford et al, 2014). It should be noted that the present study addresses only the reproducibility of bioassay responses since a single laboratory collected and processed all the samples.…”

Evidence that bisphenol A (BPA) can be accurately measured without contamination in human serum and urine, and that BPA causes numerous hazards from multiple routes of exposure

“…Similarly, the issue of assay performance was also examined using a round robin validation process in Europe for a number of chemicals, including BPA, which identified that some laboratories were able to accurately assay BPA and other chemicals without contamination, while other laboratories were unable to assay BPA or other chemicals accurately (Vanderford et al, 2014). …”

Rapid analysis of trace organic compounds in water by automated online solid-phase extraction coupled to liquid chromatography–tandem mass spectrometry

“…Considering the high degree of temporal [18] and geographical [19] variability, high-throughput time-sensitive analytical screening methods would greatly advance the resolution of environmental monitoring. Also, considering the variability of methods currently used for TOrC analyses [20], the reproducibility and accuracy of the data must be enhanced by introducing automation into the entire analytical procedure.…”