Microscale analytical methodology for the monitoring of compounds of biological origin

The use of microscale analytical methodology for the analysis of biological samples has grown in popularity in recent years because of the added selectivity and sensitivity of made possible by these techniques. Capillary chromatography with electrochemical detection is used to monitor retinoids in tissue structures isolated from embryonic chickens. Retinoid gradients are thought to be important in cellular differentiation during early development in several tissue structures including the central nervous system and limbs. In this report, the development and application of a capillary chromatography system using electrochemical detection for the monitoring of retinoids is outlined. In developing limb tissue, little evidence for a retinoic acid gradient across the anterior to posterior axis was found contradicting earlier observations of a retinoic acid gradient. For samples obtained from the primitive streak showed high levels of retinoic acid localized in Hensen's node providing significant evidence for a gradient in the early central nervous system.;One of the central problems in microscale techniques is the lack of chemical information produced by common detection methods. One possibility to overcome this problem is the use of electrospray ionization mass spectrometry with capillary separations. However, a lack of sensitivity when compared to other methods has hampered the application of electrospray ionization where analyte is severely limited. A new spectral analysis algorithm was developed to increase the ability of accurate mass determinations when the analyte of interest produces low signal levels. This algorithm relies on the signal enhancement provided by multiplying data divided among several channels. In addition, two models for the production of gas phase ions differ in their predictions of the effects of sample contaminants on the signal intensity in electrospray ionization. Samples with a wide range of conditions were analyzed resulting in data that contradicts the charge residue model while remaining consistent with the ion evaporation model.