X Series ICP-MS Clinical Applications Note1:Rapid and accurate measurement of As and Cr in urine
In comparison to blood, urine is a relatively simple
biological liquid. It is composed of 95% water, 2.5% urea
and 2.5% other substances, including major and trace
elements, such as Na and Cr, which are filtered from the
blood. With respect to the minor components, the
composition of urine changes day to day and throughout the
day, as a result of the individual’s diet and state of health.
For this reason, measuring the composition of urine aids
medical practitioners in their diagnosis of certain conditions
and also enables occupational exposure of workers in highrisk
industries to be monitored and assessed. Of particular
concern is occupational exposure to Cr (as CrVI ) and
exposure to As species through consumption of
contaminated foodstuffs. CrVI, which has been identified as
a carcinogen when inhaled, is used as a pigment in paints,
inks and plastics, as an anti-corrosion agent and as a major
component in chrome plating materials. The toxic effects of
As are also well-known, as is the fact that its toxicity
depends on the species which is present. It is a known
carcinogen2, used in wood treatment (to protect it from rot
and fungal attack), gun shot and some glass materials.
The salt content of urine is around 0.1% (m/v) so in
principle it could be aspirated directly into an ICP-MS, but
most users dilute it 1:10 prior to analysis, to reduce the
analyte signal suppression problems that such a matrix
induces. The detection limits achievable with ICP-MS for
the elements of biological interest are considerably below the
levels found in urine, so dilution in this way does not
compromise the analytical performance. Historically, flame
and graphite furnace AAS have been the techniques of
choice for this application, but in recent years ICP-MS has
been growing in popularity, mainly due to its fast, multielement
capability and its ease of operation and method
development. With the advent of collision cell technology,
the well-known Ar-based interference problems that
previously limited the detection limit capability of the
technique for elements such as Se (Ar2
+ interference), As
(ArCl+) and Cr (ArC+) have been overcome. In addition,
new developments in sample introduction technology have
made it possible to efficiently aspirate clinical samples for
long periods without causing nebuliser or torch injector
blockage, leading to improved data quality. This application
note describes the performance of the X Series ICP-MS for
measurement of the key elements As and Cr in urine.
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