Determination of Bromine and Iodine in Brine by Ion Exchange Resin Separation and Inductively Coupled Plasma-Mass Spectrometry

Natural brine contains abundant resources, including bromine (Br) and iodine (I). However, the large number of cations such as sodium (Na⁺), potassium (K⁺), calcium (Ca²⁺) and magnesium (Mg²⁺) present in the high-salt matrix, which causes severe matrix interference in the determination of Br and I by inductively coupled plasma-mass spectrometry (ICP-MS) and affect the accuracy of detection. In this work, a novel method for the accurate determination of Br and I in high-salt brine was established by using strongly acidic and high-capacity ion exchange resin to dynamically adsorb and remove of cations from the brine. The interference degree of high-salt matrix on the determination of Br and I and the influence of dilution factor on the determination results were systematically studied. The results showed that, when the total dissolved solids (TDS) of the brine exceeded 3960 mg/L, significant matrix interference occurred. While the dilution method reduced interference to a certain extent, the relative deviation of the measured values under different dilution factors was significant, resulting in low precision. After ion exchange resin treatment, the total removal rate of cations such as Na⁺ in the brine was up to 99.4%, TDS was significantly reduced and matrix interference was effectively eliminated. The detection limits for bromide and iodine were 0.36 μg/L and 0.23 μg/L, respectively, with relative standard deviations (RSD) of less than 3.64% (n=7) for both. Spike recovery rates ranged from 82.7% to 116.1%, meeting the DZ/T 0130-2006 specification requirements. This method is suitable for high-salinity brine with a TDS higher than 60 g/L, enabling the accurate determination of bromide and iodine without large multiple dilution (dilution ＜30 times). Advantages include simple pretreatment, a high matrix removal rate and accurate results. This provides reliable technical support for evaluating Br and I in high-salinity brine resources, and also provides practical basis for the application of ion exchange resin in the analysis of trace elements in complex brine system.