Development and validation of a reversed-phase HPLC method for analysis of radiochemical purity in [¹²³I]IBZM

[¹²³I]IBZM is used widely for in vivo imaging of D₂ receptors in human brain and shows relatively fast kinetics and a greater susceptibility to synaptic dopamine release than other single-photon emission computed tomography (SPECT) radioligands. A reliable and reversed-phase HPLC method using UV/VIS and radiometric detectors has been developed for qualitative analysis of BZM and IBZM and radiochemical purity in [¹²³I]IBZM preparations. The method uses gradient elution on a Zorbax XDB C-18 column with a mobile phase that consists of 10mM 3,3-dimethylglutaric acid (DMGA), pH 7.0 and acetonitrile (ACN). The flow rate was 1.0mL/min with detection at λ=254nm. The method was validated for system suitability, precision, accuracy, specificity, linearity, robustness, limit of detection (LOD) and limit of quantification (LOQ), as described in ICH guidelines. The results are described as follows: (1) The system suitability includes the tailing factor, theoretical plate number and resolution, which are 0.962, 10656.11 and 9.367, respectively. (2) For specificity, the BZM and [¹²³I]NH₄I did not interfere with the retention time of the [¹²³I]IBZM. (3) The percentage coefficient of variation for analysis of precision, including repeatability and intermediate precision, is less than 2.0%. (4) Accuracy of the method is within the range of 85-100%. (5) The range of linearity is from 100% to 70% radiochemical purity (%RCP) of [¹²³I]IBZM, with the correlation coefficient (R) always being above 0.995. (6) The data of method robustness are within acceptance criteria. (7) The LOD and LOQ for impurity (BZM) are 0.145 and 0.50μg/mL, respectively. All of the analysis results demonstrate that this method is sensitive, specific and suitable for routine analysis of the radiochemical purity in [¹²³I]IBZM preparations.