(full paper is archived in the Miller Library)
Title: HPLC analysis of squid ink: a quantification of L-DOPA and dopamine in the ink of Loligo opalescens
Student Author(s): Farrington, Heraldo M.
Location: Final Papers Biology 175H
Date: June 1992
Abstract: Potential chemical cues in squid ink were identified and quantified using high-performance, reverse-phase, liquid chromatography (HPLC). Primary amines in squid ink were conjugated with the fluorescent compound ortho-phthaldialdehyde (OPA). Upon separation by the column, l-dopa and dapamine were detected by an end-column fluorometer. Crude ink was manually extracted from the dissected ink sacs of freshly-killed Loligo opalescens collected from Monterey Bay, California. Protocols for preventing the oxidation of the active compounds were developed, thereby allowing for the storage of ink for later analysis. Fresh ink was never analyzed. Standard curves were established for both l-dopa (r^2 = .967; CV of slope = 8.2%) and dopamine (r^2 = .939; CV of slope = 9.0%). These standard curves were used to transform the integrated peak areas from the HPLC analysis into absolute quantities. Ten ink sacs, collected from 8 adult males and 2 adult females, were used to create four discrete samples for analysis. For l-dopa we report a mean concentration of 1.40 (+/- 0.43) nanomoles per milligram of extracted ink. For dopamine we report a mean concentration of 0.70 (+/- 0.14) nanomoles per milligram of extracted ink.