Determination of iodine and bromine in plasma and urine by inductively coupled plasma mass spectrometry

The simultaneous determination of iodine and bromine in plasma and urine by inductively coupled plasma mass spectrometry, using a Nermag prototype instrument, is described. The sample preparation involves only a 10-fold dilution with a diluent containing europium as an internal standard followed by direct nebulisation in the plasma. The iodine, bromine and europium ions are measured at m/z = 127, 79, and 153, respectively. The sensitivity of the method, with detection limits of 1.6 and 52 micrograms l-1 for iodine and bromine, respectively, is satisfactory for clinical applications. The calibration graphs were linear over the ranges 0-400 micrograms l-1 and 0-40 mg l-1 for iodine and bromine, respectively, which are wide enough for most assays. The recoveries were close to 100% with coefficients of variation of less than 3%. The within-day and between-day reproducibility was about 5%. The concentrations of iodine and bromine in the plasma of 26 healthy individuals were 58 +/- 12 micrograms l-1 and 4.1 +/- 0.9 mg l-1, respectively. The amounts of iodine and bromine eliminated in urine were 94 +/- 97 micrograms per 24 h (range 27-403 micrograms per 24 h) and 3.6 +/- 1.7 mg per 24 h, respectively. These results are in agreement with reported values.