Metrohm has linked ion chromatography to an inductively coupled plasma mass spectrometer (IC-ICP/MS) to create a tool to determine different species of organic and inorganic compounds in a single run.
However, during sample preparation, some of these species undergo interconversion.
These interconversions can be reliably monitored using speciated isotope dilution mass spectrometry (SIDMS), which was recently described in EPA method 6800.
Depending on the pH and the redox potential, chromium, for example, can interconvert bi-directionally between Cr3+ and the highly toxic and carcinogenic Cr6+.
Similarly, mercury tends to undergo various transformations when released into the environment.
It is found in several forms, particularly as elemental mercury (Hg0), inorganic mercury (Hg2+) and biologically active organic mercury (methylmercury CH3Hg+).
By introducing enriched isotopic species spikes into the analytical process, users can correct for and measure those interconversions to derive true concentrations of the species.
While arsenic compounds can be analysed without applying SIDMS, several commonly used extraction techniques used for mercury speciation in biological samples (such as tuna fish tissue as in EPA 6800) are evaluated by applying both SIDMS and external calibration.
