Ultrafiltration immunoaffinity

The aqueous or organic extract obtained at this step of analysis may be a very dilute solution of the analyte(s) of interest. It may also contain coextractives, which if allowed in the final extract will increase the background noise of the detector, making it impossible to determine trace level concentrations of the analyte(s). To reduce interferences and concentrate the analyte(s), the primary sample extract must be subjected to cleanup procedures such as liquid-liquid partitioning, solid-phase extraction, matrix solid-phase dispersion, ultrafiltration, immunoaffinity chromatography, and online trace enrichment. In many instances. 

Wieboldt R, Zweigenbaum J, Henion J immunoaffinity ultrafiltration with ion spray HPLC/MS for screening small-molecule libraries. Anal Chem 1997, 69, 1683-1691. 

Ultrafiltration (278, 279) and immunoaffinity chromatography (282) have also been described for removal of matrix components from milk extracts, while online trace enrichment has been reported for isolation/purification of tetracycline, oxytetracycline, demeclocycline, and chlortetracycline residues from animal tissues and egg constituents (305). The latter technique involves trapping of the analytes onto a metal chelate affinity preconcentration column (Anagel-TSK Chelate-5PW), rinsing of coextracted materials to waste, and finally flushing of the concentrated analytes onto the analytical column. 

The majority of reports have used electrospray ionization mass spectroscopy (ESI-MS) as an analytical detection method because of its sensitivity and the soft namre of its ionization procedure, which generally only leads to the detection of the molecular ions of the positive library members. Many separation techniques have been coupled to ESI-MS, including affinity chromatography (49), size exclusion chromatography (50, 51), gel filtration (52), affinity capillary electrophoresis (53-58), capillary isoelectric focusing (59), immunoaffinity ultrafiltration (60), and immunoaffinity extraction (61). ESI-MS has also been used alone (62) to screen a small carbohydrate library. Other examples reported alternative analytical techniques such as MALDI MS, either alone (63, 64) or in conjunction with size exclusion methods (65), or HPLC coupled with immunoaffinity deletion (66). 

R. Wieboldt, J. Zweigenbaum, J.D. Henion, Immunoaffinity ultrafiltration with LC-ESI-MS for screening small-molecule libraries. Anal. Chem., 69 (1997) 1683. 

Wieboldt, R. Zweigenbaum, J. Henion, J. Immunoaffinity Ultrafiltration with Ion Spray HPLC/MS for Screening Small-Molecule Libraries," Anal. Chem. 69, 1683-1691 (1997). 

Albumin, a major constituent in serum (60-80 mg/L), is known to act as a transport carrier for small proteins. Also, many antineoplastic drugs bind to albumin, often at the 80-95% level. Removal or depletion of albumin is a major problem there are problems with ultrafiltration (e.g., membrane binding of small proteins and drugs) and other approaches, e.g., Cibacron dye columns and immunoaffinity-based protein subtraction chromatography. Albumin removal using acetonitrile may be a simple alternative [54] however, there is no truly satisfying method at this time. 

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