AccQ-Tag

AccQ-Tag ) system mentioned in the section on amines has also been used for amino acids.90... 

Anon (1996a) The successful use of UV detection with the AccQ-Tag method. Waters AccQ-Tag solutions March, 2 pages. Available as a downloadable file from the Waters website (http //www.waters.com). 

Figure 7.30. HPLC analysis of pre-column derivatized amino acids (50 pmoles) using Waters AccQ.Tag reagents with reversed-phase chromatography separation and fluorescence detection. Chromatogram courtesy of Waters Corporation.

HPLC (AKTA-design system (Pharmacia) using a AccQ Tag column)... 

Aminoquinolyl-N-hydrosuccinimidyl carbamate reacts quickly with amino acids in a simple procedure to give stable derivatives that can be detected by fluorescence or absorption after separation on a reversed phase at 37°C. The reagents and buffers are commercially available (AccQ-TAG). 

We find that the precolumn labeling AccQ-tag (Waters, Corp.) method is a good compromise for labs with a need to determine a reference material protein concentration on an infrequent basis. The labeling procedure is relatively simple, with very little sample manipulation and a short reaction time. This, combined with the high resolution and rapid analysis time of a UHPLC system, allows for a relatively rapid, accurate, precise, and convenient method (See Figure 9). 

FIGURE 9 Amino acid analysis of a monoclonal antibody (mAb) using liquid-phase acid hydrolysis (6 M HCI), followed by AccQ-tag labeling and UHPLC separation. The top panel shows a chromatogram of amino acid standards. 

There have been many other precolumn derivatization methods developed, each with its own list of pros and cons. Table 9.3 lists some of the other derivatization methods. Some of these methods are available in commercial kits such as Waters Corporation s (Millford, MA) Pico-Tag and AccQ-Tag. These kits ensure quality reagents and very reproducible results. Commercial kits can be of benefit to the laboratory that does not conduct routine analysis of amino acids. However, these kits are not foolproof, nor do they guarantee good results. These kits may not work for all matrices, or the conditions may need modification with different matrices. No kit can completely replace experience. 

---