On-line connector for microcolumns: application to the on-column o-phthaldialdehyde derivatization of amino acids separated by capillary zone electrophoresis

Abstract

The design of a simple, on-column connector for microcolumn separations Is described. The connector, In the form of a cross or tee, Is fabricated from the fused silica capillary tubing, Itself, and has sufficiently low dead volume to be compatible with the tubing dimensions normally associated with microcolumn separation techniques. As a demonstration of one possible application, a mixture of amino acids Is separated by capillary zone electrophoresis (CZE), the amino acids are derlvatlzed on-column with o-phthaldialdehyde (OPA) Introduced from a cross connector, and the highly fluorescent adducts are detected downstream by laser-induced fluorescence. Zone broadening by the connector Is determined to be approximately 10% for CZE separations performed In 75 pm l.d. capillary tubes. Detector response Is found to be linear over more than 3 orders of magnitude with minimum limits of detection In the subfemtomole range.

Pulsed electrochemical detection of nonchromophoric compounds following capillary electrophoresis

“…Sugar alcohols and complex mixtures of neutral carbohydrates are difficult, if not impossible, to separate as charged species. Post-decoupler addition of NaOH to alter the pH of the operating buffer appears to be a viable option based upon studies with post-capillary addition of derivatization reagents [25]. Figure 8 shows the separation of five compounds under mildly alkaline conditions (i.e., 20 mM borate, pH 9.0).…”

Biomedical applications of capillary electrophoresis with laser‐induced fluorescence detection

“…There are several different derivatizing agents that have been used so far. The ophthaldehyde (OPA) that produces fluorescent isoindoles is detected in the fentomolar range [34]. Naphtalene-2,3-dicarboxaldehyde (NDA), an analog of OPA, with higher quantum yield, and 3-benzoyl-2-quinolinecarboxaldehyde (BQCA) have more stable derivatives than OPA [35,36].…”

A new post-column reactor-laser induced fluorescence detector for capillary electrophoresis

“…Being a non-fluorescent and rapid reacting reagent, OPA has been widely used as a post-column reagent in both HPLC [34,35] and CZE [22,25,27, 281. Instrumentation.…”

“…A low dead volume cross type connector was fabricated on a capillary by drilling holes into the capillary [25]. Reaction reagents have also been introduced into a gap between two closed aligned capillaries ( several micrometers apart).…”