SCHEDULED MAINTENANCE
Measurements of44Ca:43Ca and 42Ca:43Ca Isotope Ratios in Urine Using High Resolution Inductively Coupled Plasma Mass Spectrometry
Abstract
A method is described for the measurement of calcium isotopic ratios
(
42
Ca
+
:
43
Ca
+
and
44
Ca
+
:
43
Ca
+
) in human urine
using high resolution inductively coupled plasma mass spectrometry
(HR-ICP-MS). Relative standard deviations (RSD) of 0.33 and 0.41% were
found for
44
Ca
+
:
43
Ca
+
and
42
Ca
+
:
43
Ca
+
, respectively.
Using a mass spectrometric resolution setting of 4000, the calcium peaks
were resolved from interfering polyatomic ions
(
40
Ar
2
H
+
and
40
ArH
2
+
on
42
Ca
+
and
28
Si
16
O
+
and
12
C
16
O
2
+
on
44
Ca
+
). Interferences from Sr
2+
, which
cannot be resolved even using high resolution, were corrected for
mathematically using the
43.5
Sr
2+
peak. The sample
preparation step consisted of a simple 50-fold dilution of the urine
sample with 0.14 M HNO
3
, which ensured a relatively
high sample throughput of 6 samples per hour.
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