Fig. 4.

RP-separation of long-chain aldehydes according to chain length. Aldehydes (1-3 nmol, based on derivatization with 2,4-dinitrophenylhydrazine) with different chain lengths (13–18 carbon atoms) were mixed, converted to CHD derivatives, separated by RP-HPLC, and detected by fluorimetry (Ex 390 nm, Em 460 nm). The insert shows the relationship between elution time and aldehyde chain length. The drop in fluorescence near 1.8 min is due to a transient closure of the emission filter to protect the detector against too high intensity.