14
Environmental Laboratory
Determination of Iopromide in Environmental Waters by Ion Chromatography-ICP-MS
Iopromide is an iodinated contrast medium (ICM), which is used to image internal body organs and blood vessels by x-ray or computerised tomography (CT) scan. Iopromide is generally given to patients in g/L concentrations and is excreted within 24 hours in the patient’s urine [1]. It is very hydrophilic (log Kow = –2.33) and non-ionic, properties that make it quite persistent in the environment. The molecular formula of iopromide is C18H24I3N3O8 and its chemical structure is shown in Figure 1.
wastewater contamination [8].
We have successfully quantified iopromide in a series of environmental water extracts using an Agilent 1260 LC coupled to an Agilent 7700x ICP-MS.
Figure 1: Chemical structure of iopromide Iopromide’s presence in surface waters and wastewaters has been widely
reported as ranging from several ng/L to as much as 10 µg/L in sewage treatment plant effluents [2–4]. Furthermore, ICMs are known to be resistant to sewage treatment and studies have shown they are relatively poorly removed by conventional treatment processes [2, 5–7]. Due to its presence and environmental persistence, it has also been suggested that iopromide be used as a potential indicator compound of
Recent studies indicate that iopromide and other ICMs can form toxic iodinated disinfection bi-products (I-DBPs) during oxidation and disinfection water treatment processes [4, 9, 10]. Certain I-DBPs are known to be several times more toxic than chlorinated and brominated disinfection bi-products [11–13] but are, as yet, not regulated by the US Environmental Protection Agency (USEPA) or other regulatory agencies.
Most analytical methods developed for iopromide and other ICMs involve the use of LC coupled to a mass spectrometer, generally a triple quadrupole mass spectrometer [9, 14–17]. Hybrid methods involving ion trap and nuclear magnetic resonance have also been employed. This application note describes the optimised conditions for sensitive and reproducible analysis of sub-ppb levels of iopromide in water extracts, using an Agilent 1260 LC coupled to an Agilent 7700x ICP-MS. With the use
of a 500 µL injection volume, we have established a lower method reporting limit (MRL) of 0.1 ppb for iopromide in the diluted methanol extracts in our assay; in theory this corresponds to a lower MRL of 2 ppt in our environmental water samples.
Experimental
Environmental water samples were collected at established monitoring points along the rivers and creeks in the state of California, including
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Figure 2: Comparison of the iodine chromatograms (m/z 127) obtained from injections of an aqueous blank extract (top) and an aqueous 0.1 ppb iopromide standard (bottom). The retention time of iopromide is 10.1 minutes.
AET Annual Buyers’ Guide 2013
www.envirotech-online.com
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