Effectiveness of activated carbon disk for the analysis of iodine in water samples using wavelength dispersive X-ray fluorescence spectrometry

• A novel approach for the analysis of iodine in water samples was developed.
• Iodine preconcentrated on the AC disk was directly analyzed using WDXRF spectrometry.
• The AC disks were sufficiently durable for repeatable measurements until 8 days.
• The accuracy of the proposed AC-WDXRF method was confirmed by spike tests.

A novel approach using wavelength dispersive X-ray fluorescence (WDXRF) spectrometry combined with an activated carbon (AC) disk was developed for the determination of total iodine concentrations in water samples. Dissolved iodine species (i.e., I− and IO3−) in water samples were preconcentrated on the AC disk and directly analyzed by WDXRF spectrometry. The adsorption behavior of I− and IO3− on the AC disk was assessed at varying pH levels (4, 6, and 8). The AC disks completely retained the I− and IO3− for all the pH levels tested. The calibration curve obtained from the iodine concentrations (i.e., 0, 20, 200, and 400 μg) of AC disks and the measured X-ray intensity from the WDXRF analysis showed a good linearity (R2 = 0.9960), with a relatively low limit of detection (0.575 μg). The durability of the AC disk for repeatable measurements was also assessed to validate the sustainability of the proposed method and consequently the measured X-ray intensity for the AC disks was constant until 8 d of analysis time. The accuracy of the proposed AC-WDXRF method was confirmed by measuring iodine concentration spiked in drinking water using inductively coupled plasma-mass spectrometry (ICP-MS). The proposed method is simple, rapid, efficient, and environmental friendly for iodine analysis in water samples. As a precursor of disinfection by products (DBPs), it is important to determine the total iodine concentrations in raw water.