Determination of urinary iodine by inductively coupled plasma mass spectrometry.
BACKGROUND
Mild iodine deficiency is endemic in many countries of Europe including Belgium. Fast, accurate and specific methods for quantification of urinary iodine are needed. We describe in this report a specific ICP-MS method for the quantification of urinary iodine.


METHODS
Samples and iodate calibrators were diluted 20 times into aqueous solution containing triton X-100, 1.5% HCl and (103)Rh as an internal standard. Prior digestion or oxidation was not necessary. Results were compared with those obtained by Sandell-Kolthoff (S-K) spectrophotometric method.


RESULTS
Comparison of both methods showed good agreement. The Passing-Bablok regression between both methods was ICP-MS=0.986 (S-K)-7.51. The Bland-Altman difference plot showed a small but significant mean difference of -13.3 microg/L for ICP-MS. The between-day coefficient of variation (CV) was 13% at 89 microg/L. Limit of detection was 4 microg/L and limit of quantification was 20 microg/L. No carryover effect has been observed on series containing up to 50 samples.


CONCLUSIONS
The ICP-MS method described here is fast, accurate and specific for the quantification of urinary iodine. Compared to the S-K method the urinary iodine concentrations measured by the ICP-MS method were slightly, but significantly lower. Consequently, the results of studies using S-K method should be compared with caution with those using the ICP-MS method.
Macours
P
P
Laboratory of Clinical Chemistry, Hôpital Erasme, Université Libre de Bruxelles, Route de Lennik 808, 1070 Bruxelles, Belgium.
Aubry
J C
JC
Hauquier
B
B
Boeynaems
J M
JM
Goldman
S
S
Moreno-Reyes
R
R
D006801:Humans; D007455:Iodine / Q000652:urine*; D013058:Mass Spectrometry / Q000379:methods*; D015203:Reproducibility of Results
D007455:Iodine