Elsevier

Chemosphere

Volume 243, March 2020, 125311
Chemosphere

A direct injection liquid chromatography tandem mass spectrometry method for the kinetic study on iodinated contrast media (ICMs) removal in natural water

https://doi.org/10.1016/j.chemosphere.2019.125311Get rights and content

Highlights

  • Rapid and sensitive direct injection method for analysis of seven target ICMs.

  • The method was validated in complex aqueous matrices such as secondary effluent, groundwater and drinking water.

  • Removal of seven target ICMs by LPUV/H2O2, LPUV/Cl2 and LPUV/NH2Cl.

Abstract

Iodinated contrast media (ICMs) are a class of X-ray contrast media worldwide utilized for radiographic procedures. Since they cannot be removed efficiently during water treatment, they can be found in surface and groundwater. In this work, a rapid and sensitive direct injection liquid chromatography-tandem (LC-MS/MS) method for the simultaneous analysis of seven ICMs media (iopamidol, ioxitalamic acid, diatrizoic acid, iothalamic acid, iohexol, iomeprol and iopromide) in complex aqueous matrices has been developed and validated. The MDLs for the analytes ranged from 0.7 to 21 ng L−1 in ultrapure water, and recoveries ranged from 86 to 100% in drinking water, 85–103% in groundwater and 84–105% in WWTP effluent. A stereo-isomer for iopromide was separated. This analytic method was applied to investigate the removal of target ICMs by low pressure ultra violet light (LPUV) advanced oxidation processes with three oxidants, hydrogen peroxide, free chlorine and monochloramine in groundwater. Results showed that the addition of oxidants did not enhance attenuation of ICMs, since fluence-based decay apparent rate constants were similar (KUV = 3.2 × 10−3, KUV-Cl2 = 3.6 × 10−3 and KUV-NH2 = 3.4 × 10−3 10−3 cm2 mJ−1). This yielded direct photolysis is the main mechanism to attenuate target ICMs.

Introduction

A current major challenge for water analysis is to develop a simple, sensitive and robust method for the detection and quantification of emerging contaminants at trace levels in complicated matrices such as surface water and wastewater effluents. In recent years, iodinated contrast media (ICMs) as the most widely administered intravascular pharmaceuticals in medical X-ray have become one of the most prevalent emerging contaminants. Owing to their high polarity and biological stability, ICMs are usually difficult to remove by conventional wastewater treatment (Busetti et al., 2008, Pauwels and Verstraete, 2006). Hence ICMs have been detected at μg L−1 levels in aqueous environments, including surface water, groundwater, and even drinking water (Ternes and Hirsch, 2000, Weissbrodt et al., 2009). Although ICMs are non-toxic to the human body, they have received increasing attention as potential precursors of iodinated disinfection by-products (I-DBPs) which have been proven to be highly cytotoxic and genotoxic to mammalian cells (Duirk et al., 2011). It has been reported in recent years that I-DBPs are generally of much higher developmental toxicity and growth inhibition than their bromo- and chloro-analogues (Richardson et al., 2008). There are two types of ICMs based on their charges at a neutral pH. Non-ionic ICMs have been more heavily studied than ionic ones since they are more abundant in surface waters (Pérez and Barceló, 2007, Westerhoff et al., 2005). The most common methods involve liquid chromatography coupled to an ultra violet detector (LC-UV) or tandem mass spectrometry (LC-MS/MS). Tian et al. (2014) developed a method utilizing LC-UV detector for quantification of iopamidol, with a detection limit of 5  μg L−1. Ternes and Hirsch (2000) developed a sensitive LC-MS/MS method with solid-phase extraction (SPE) step using a non-polar cartridge and achieved a level of quantification of 10 ng L−1. In addition, Sacher et al. (2005) developed a method to analyze six ICMs using ion chromatography (IC) for separation and inductively coupled plasma mass spectrometry (ICP-MS) for quantification which obtains limits of detection of about 0.2 μg L−1 without pre-concentration. Table 1 shows a summary of different methods developed for ICM quantification.

Most current analytical methods for the determination of ICMs in aqueous matrices include a SPE as a pre-concentration step in order to enrich the analytes, clean them up from the interfering matrices, and achieve lower detection limits (Ternes et al., 2005). However, SPE procedure is costly and time-consuming, and may result in a loss of analytes (Sacher et al., 2005). Large volume injection LC-MS/MS methods have become popular since they do not require a pre-concentration step with SPE. They also increase the overall recoveries of the analysis, whereas achieve lower limits of detection (LOD) (Anumol et al., 2013).

The objective of this study was to develop a rapid, sensitive and robust direct injection LC-MS/MS method for the simultaneous analysis of seven ICMs (iopamidol, ioxitalamic acid, diatrizoic acid, iothalamic acid, iohexol, iomeprol and iopromide) in environmental waters such as secondary effluent, ground water and drinking water. This current method was applied to investigate the removal of target ICMs by low pressure ultra violet (LPUV) advanced oxidation processes with three oxidants (hydrogen peroxide, free chlorine and monochloramine) in groundwater.

Section snippets

Chemicals

Diatrizoic acid (DTZ) was purchased from Sigma-Aldrich (St. Louis, MO, USA). Iothalamic acid (IOT) and ioxitalamic acid (IOX) were purchased from Toronto Research Chemicals (Ontario, Canada). Iohexol (IOH), iopamidol (IOD), and iopromide (IOP) were obtained from the United States Pharmacopeial Convention Inc. (Rockville, MD, USA). Iomeprol (IOM) was purchased from LGC Standards (Manchester, NH, USA). The isotopically labeled surrogate standards (ILSS), iohexol-d5 (IOH-d5) and iopamidol-d3 (IOD-d

Optimization for liquid chromatography conditions

To maximize separation efficiently of the seven target ICMs, Agilent Poroshell 120 EC-C8 column (4.6 × 100 mm, 2.7 μm particle size) was chosen, while water containing 0.1% (v/v) formic acid and methanol containing 0.1% (v/v) formic acid were applied as mobile phases. As shown in Fig. 1, under the optimized LC conditions, baseline separation was achieved for the isomers—DTZ and IOT, which were difficult to separate (Ens et al., 2014). Also, the two stereoisomers of IOP were separated. However,

Conclusion

This direct injection method yielded lower method detection limits of 0.7–21 ng L−1 and recoveries above 95% in groundwater, drinking water and secondary effluent. Validation experiments under LPUV illustrated that direct photolysis is the main mechanism to attenuate seven target ICM in groundwater. Oxidants such as hydrogen peroxide, free chlorine and monochloramine did not enhance the removal of ICM. The use of free chlorine and monochloramine as a radical under AOP may have some adverse

Acknowledgments

The authors would like to acknowledge The University of Arizona, Department of Chemical and Environmental engineering for providing the facility for UV experiments. We especially wish to acknowledge Xylem Wedeco for providing collimated beam device low-pressure ultra violet light reactor. We also appreciate Agilent Technologies for their assistance with the acquisition and maintenance of the instrumentation used in this study.

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