Evaluation of alternative methods for radiochemical purity testing of indium-111 capromab pendetide

To evaluate alternative methods for radiochemical purity testing of indium (In)-111 capromab pendetide after the discontinuation of instant thin-layer chromatography silica gel (ITLC-SG) strips.

Descriptive experimental study.

United States in 2009.

Not applicable.

Paper chromatography using Whatman 3MM strips, paper chromatography using Whatman 31ET strips, and mini-column chromatography using silica Sep-Pak cartridges were evaluated in the radiochemical purity testing of 13 consecutive vials of In-111 capromab pendetide prepared for clinical patient imaging procedures. These methods also were evaluated by testing seven aliquots of In-111 capromab pendetide that had been spiked with 5% to 15% In-111 pentetate (diethylene triamine pentaacetic acid).

Correlation coefficients, radiochemical purity values for each method compared with ITLC-SG, and procedure times.

Correlation coefficients of 0.988, 0.996, and 0.979 were found for ITLC-SG compared with Whatman 3MM, Whatman 31ET, and silica Sep-Pak, respectively. Compared with ITLC-SG, mean (±SD) radiochemical purity values differed by -0.8 ± 0.8 (range -2.5 to 0.4) for Whatman 3MM, -0.8 ± 0.6 (-2.3 to 0) for Whatman 31ET, and -0.5 ± 1.2 (-3.6 to 0.7) for silica Sep-Pak. The approximate time required to develop the chromatography strip or elute the mini-column was 3, 14, 5, and 6 minutes for ITLC-SG, Whatman 3MM, Whatman 31ET, and silica Sep-Pak, respectively.

All three methods evaluated were acceptable alternatives to ITLC-SG for radiochemical purity testing of In-111 capromab pendetide. Based on its slightly higher correlation to ITLC-SG, slightly tighter SD and range, and slightly shorter development time, Whatman 31ET is preferred in our facility.