o-Phthalaldehyde Reagent


Courtesy of Pickering Laboratories, Inc.


Primary amines form highly fluorescent adducts when reacted with o-Phthalaldehyde (OPA) and a mercaptan under basic conditions. At a pH>9 and ambient temperature, reaction is generally complete within 30 seconds. The products of this reaction, 1-alkyl-2-alkylthio-substituted isoindoles, exhibit optimal excitation at 330 nm and maximal emission at 465 nm. The reagents described below are intended for postcolumn derivatization of primary amines such as:

  • amino acids in native samples and protein or tissue digests
  • those formed by post-column cleavage of carbamate insecticides or glyphosate herbicide
  • those derived from other sources.

Reagent Components

o-Phthalaldehyde, Chromatographic Grade

Pickering’s OPA is specially prepared to meet the demanding requirements of highsensitivity pre- and post-column HPLC derivatization methods. Our repurification process actually begins with commercially available 99% material.

The entire process is controlled to prevent trace amine contamination. Lot quality is verified by post-column HPLC
using a high-sensitivity fluorescence detector.

Thiofluor, Chromatographic Grade
Pickering’s Thiofluor, a solid, nearly odorless nucleophile, is a superior substitute for 2-Mercaptoethanol in the preparation of OPA reagents. It forms a more stable reagent and longer-lasting fluorophore with OPA than does 2-Mercaptoethanol, yet it has the same fluorescence properties. Unlike the volatile 2-Mercaptoethanol, Thiofluor will not migrate through the gas manifold and regulator of the OPA reagent pressurization system. Two grams of Thiofluor is equivalent to 1 mL of 2-Mercaptoethanol.

o-Phthalaldehyde Diluents, Chromatographic Grade

Three application-specific diluents are available from Pickering Laboratories: CB910 and GA104 for carbamate and
glyphosate analyses, and OD104 for amino acid analysis.

These borate solutions are produced from starting materials which are free of heavy metals and amines. As with most other products of Pickering Laboratories, the quality of the OPA Diluents is verified by actual post-column HPLC analysis.

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