An analytical method for the simultaneous determination of five booster biocides (Sea-Nine 211, Dichlofluanid, Duiron, Irgarol 1051 and Pyrithiones) and degradation product of Irgarol 1051 (M1) in sediment from Vietnam was developed by LC/MS-MS. The recovery rates and relative standard deviation of the booster biocides in the sediment were in the range of 71–108% and 1.5–12%, respectively, and the detection limits were in the range of 0.04–2 μg kg−1 dry. An analytical method for the simultaneous determination of three booster biocides (Sea-Nine 211, Duiron and Irgarol 1051) and M1 in clams was also developed by LC/MS-MS. The recovery rates and relative standard deviations of the booster biocides in the biological samples were in the range of 60–99% and 3.4–6.8%, respectively, and the detection limits were in the range of 0.24–1.1 μg kg−1.

The booster biocides in sediment from the coastal area of northern and central Vietnam were measured using this analytical method. Sea-Nine 211, Dichlofluanid, Duiron, Irgarol 1051, M1 and Pyrithiones were detected in the range of 0.09–1.3 μg kg−1 dry, <0.10–13 μg kg−1 dry, 0.11–3.0 μg kg−1 dry, 0.05–4.0 μg kg−1 dry, <0.1–0.43 μg kg−1 dry and <2–420 μg kg−1 dry, respectively. The detection frequencies of Dichlofluanid, M1 and Pyrithiones were low. The species and levels of detected booster biocides varied between sampling stations.

Irgarol 1051 and its degradation product M1 were not detected in clams.