Samples, complex biological, online

Xiang, E, Lin, Y., Wen, J., Matson, D. W, and Smith, R. D. (1999). An integrated microfabricated device for dual microdialysis and online ESI-ion trap mass spectrometry for analysis of complex biological samples. Anal. Chem. 71, 1485—1490. 

Online Preparation Of Complex Biological Samples Prior To Analysis By HPLC, LC/MS And/Or Protein Sequencing... 

Xiang, R Lin, Y. Wen, J. Matson, D.W. Smith, R.D. An Integrated Microfabricated Device for Dual Microdialysis and Online ESI-Ion Trap Mass Spectrometry for Analysis of Complex Biological Samples, Anal. Chem. 71, 1485-1490 (1999). 

The online coupling of a separation device with mass spectrometry is an analytical approach that can help in the analysis of real-world samples such as environmental samples and biological tissues and fluids. This online marriage between two stand-alone analytical techniques can provide an unequivocal characterization of individual components of such complex samples and greatly increases the information content of those components. Several issues that must be addressed to achieve an ideal combination. A major concern is the pressure mismatch. The solvent incompatibility also becomes an issue in the coupling of LC and CE with mass spectrometry. Thus, online coupling requires an interface that can transport the separated components into the ion source without affecting their resolution or the performance of a mass spectrometer. Not all types of mass spectrometers... 

Online LC-MS is a good solution for separation, identification, and quantification because it permits the confirmation of polar and nonvolatile compounds without need for derivatization.4 The use of LC-MS for biological sample detection and data analysis has grown rapidly during the past few years. Many reliable and easy to use LC-MS systems are commercially available and have been adapted for solving analytical problems by scientists in proteomics research, metabolic study, complex natural product separation and characterization, and drug discovery. 

Most applications of online solid sorbent extraction for FAAS and ETAAS were for water and seawater samples. That is not surprising because this matrix is somewhat ideal to demonstrate the improvement brought about by the extraction procedure. Seawater causes a lot of problems, particularly in ETAAS, because of its high sodium chloride concentration. Sodium chloride is not retained at all at the packed columns used for sorbent extraction, so that only the trace elements are introduced into the atomizer. However, some biological materials contain fairly high concentrations of iron and copper, elements which may also be retained at the colunm and hence compete with the analyte element for active sites. Copper forms particularly stable complexes over a wide pH range and is retained very easily on a variety of solid sorbents. For this reason, values obtained for cadmium were low in samples with high copper content [52]. 

Restricted access materials (Figure 9.8) are mostly used with online sample cleanup and enrichment of protein-rich biological samples. The crude samples, even as complex as serum or plasma, can be injected without any pretreatment. The commercially available RAM cartridges are reusable. The sorbents (alkyl-diol sUica ADS) are hydrophilic on the outside, while the surface in the pores is modified with hydrophobic groups (C4, C8, or C18). 

Another attachment that can be effected to a Raman spectrometer is a remote probe. This consists of a fibre optic cable that passes the laser beam to a sample outside the conventional sampling chamber. This can be of use in many different applications, the most obvious of which is where the sample is too large or complex to fit into the instrument. In vivo biological studies utilize a fibre optic probe for the investigation of human tissue. Industrial process monitoring uses a Raman spectroscopic probe for online quality control during manufacture. 

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