2.4. GC-ECD analysis
Nitrogen at a constant pressure of 11.258 psi was used as a
carrier gas. The injection temperature was maintained at
260C, and all injections were made in split mode with a split
ratio of 10:1. The injection volume was 1 mL. The GC oven
temperature was held at 50C for 3 minutes, raised to 220C at
30C/minute, then programmed to 250C at 30C/minute and
held for 5 minutes. The ECD detector temperature was
maintained at 300C. The makeup gas was nitrogen at a
makeup flow of 29 mL/minute. The GC chromatograms for
iodine standard solution and seaweed samples are shown in
Fig. 1. Seaweeds are known to contain both bromine and
iodine [36], which can also react with 3-pentanone [37]. The
peak at 12.08 minutes was identified as 2-iodo-3-pentanone by
comparison of the GC chromatogram of the KI standard solution
through the sample pretreatment step. The peak at 9.90
minutes was identified as 2-bromo-3-pentanone by comparison
of the GC chromatogram using the KBr solution as a
reference standard.