Herein, we describe the highly efficient photochemical
vapor generation
(PVG) of a volatile species of Ir (presumably iridium tetracarbonyl
hydride) for subsequent detection by inductively coupled plasma mass
spectrometry (ICPMS). A thin-film flow-through photoreactor, operated
in flow injection mode, provided high efficiency following optimization
of identified key PVG parameters, notably, irradiation time, pH of
the reaction medium, and the presence of metal sensitizers. For routine
use and analytical application, PVG conditions comprising 4 M formic
acid as the reaction medium, the presence of 10 mg L–1 Co2+ and 25 mg L–1 Cd2+ as
added sensitizers, and an irradiation time of 29 s were chosen. An
almost 90% overall PVG efficiency for both Ir3+ and Ir4+ oxidation states was accompanied by excellent repeatability
of 1.0% (n = 15) of the peak area response from a
50 ng L–1 Ir standard. Limits of detection ranged
from 3 to 6 pg L–1 (1.5–3 fg absolute), dependent
on use of the ICPMS reaction/collision cell. Interferences from several
transition metals and metalloids as well as inorganic acids and their
anions were investigated, and outstanding tolerance toward chloride
was found. Accuracy of the developed methodology was verified by analysis
of NIST SRM 2556 (Used Auto Catalyst) following peroxide fusion for
sample preparation. Practical application was further demonstrated
by the direct analysis of spring water, river water, lake water, and
two seawater samples with around 100% spike recovery and no sample
preparation except the addition of formic acid and the sensitizers.
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