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Development of a small volume (2-4 liter) technique for measuring ²³⁴ Th in sea water has been instrumental in bringing to light small-scale structures in upper-ocean particle removal processes previously missed by standard ²³⁴ Th measurement techniques. Further development of this method to evaluate removal efficiencies of ²³⁴ Th via MnO ₂ precipitation quantified using ICP-MS are presented in this work. Advantages to this approach are precise knowledge of ²³⁴ Th recovery, while maintaining high sample throughput afforded by ICP-MS analyzes. The improved technique includes the acidification of 4-liter sea water samples and the addition of ²³⁰ Th as a yield monitor prior to MnO ₂ precipitation. Subsequent filtration and beta-counting of the high-energy daughter, ^234m Pa, was …