Microdialysis sampling detection

Ahn JK, Koh EM, Cha HS, Lee YS, Kim J, Bae EK (2008) Role of hypoxia-inducible factor-lalphain hypoxia-induced expressions of IL-8, MMP-1 and MMP-3 in rheumatoid fibroblast-tike synoviocytes. Rheumatology (Oxford) 47(6) 834-839 Ao X, Wang X, Lennartz MR, Loegering DJ, Stenken JA (2006) Multiplexed cytokine detection in microUter microdialysis samples obtained from activated cultured macrophages. J Pharm Biomed Anal 40(4) 915-921... 

Mei, D.A., Gross, G.J., and Nithipatikom, K., Simultaneous determination of adenosine, inosine, hypoxanthine, xanthine and uric acid in microdialysis samples using microbore column liquid chromatography with diode array detection, Analyt. Biochem., 238,34,1996. 

Piepponen TP, Skujins A. 2001. Rapid and sensitive step gradient assays of glutamate, glycine, taurine and y-amino-butyric acid by high-performance liquid chromatography-fluorescence detection with o-phthalaldehyde-mercap-toethanol derivatization with emphasis on microdialysis samples. J Chromatogr B 757 277-283. 

The potential of 4-p F]FMR for the imaging of sympathetic innervation is further confirmed by the development of analytical methods such as planar chromatographic analysis for the detection of its metabolites. This analytical method is well suited for microdialysis samples which have small volumes and low concentrations of compounds [177],... 

One of the advantages of CE, which is also a disadvantage, is the very small volume needed for analysis. Typical injection volumes are 1-10 nL. This ability to inject small volumes has been shown to be useful in the analysis of single cells and microdialysis samples. Although the concentration-based detection limits of LCEC and CEEC are similar, detection limits based on actual mass analyzed are much lower for CEEC. Typical mass limits of detection for an electroactive compound are in the attomole range. 

Most electrode materials that are employed in LCEC can also be used for CEEC. The most commonly employed working electrode is a carbon fiber. Carbon fibers come in many different sizes and can also be etched to smaller diameters. Common applications of CEEC with carbon fiber electrodes are the detection of catecholamines in single neuronal cells and amino acids in brain microdialysis samples following derivatization with NDA/CN. 

S Mannino, MS Cosio. Determination of benzoic and sorbic acids in food by microdialysis sampling coupled with HPLC and UV detection. Ital J Food Sci 8 311 —316, 1996. 

R.W. Min, V. Rajendran, N. Larsson, L. Gorton, J. Planas and B. Hahn-Hagerdal, Simultaneous monitoring of glucose and L-lactic acid during a fermentation process in an aqueous two-phase system by on-line FIA with microdialysis sampling and dual biosensor detection, Anal. Chim. Acta, 366(1-3) (1998) 127-135. 

A Stipstik column (53 cm x 1 mm i.d.) with ChO/AChE reactor and guard columns. 29 mM NaH2P04-22 mM sodium acetate-5 mM Kathon of pEi 8.5. Electrochemical detection ACh in microdialysis samples. [190]... 

Coupling of microdialysis sampling with hiosensing detection modes... 

Despite the complexity of the system, this was the first apparatus that successfully used chemiluminescent detection for the on-line monitoring of glucose with in vivo microdialysis sampling. 

Even though much work still remains to be done to achieve practical applications in glucose sensing, these examples demonstrate the interest and efforts of scientists in coupling the microdialysis sampling technique with the ever-increasing array of detection modes. 

A first report appeared in 1992 from Flentge [153] who developed an enzyme reactor for the amperometric detection of both metabolites, but only the detection system for choline was coupled with microdialysis. The enzymes (one or both) were physically entrapped between two cellulose nitrate filters, and the sandwich reactor was put on-line after an HPLC column for the separation step, or else placed directly after the microdialysis probe for the online measurement of choline. The sensitivity of this system was sufficient to measure acetylcholine and chohne in rat striatum when used after the HPLC column, while the dilution due to the microdialysis sampling only permitted determination of choline, even if in a continuous mode. 

A related issue is that while microdialysis is a continuous process, it is coupled to an analytical separation step that requires discrete sample volumes. Individual samples can be collected off-line with a fraction collector and assayed later (Fig. 3). The temporal resolution is defined by the time interval at which the microdialysis samples are collected. Without the need for further sample cleanup, the temporal resolution for off-line analysis will ultimately be dependent on the perfusion rate and the volume of sample needed for quantitation. If the analytical method does not have sufficient limits of detection, larger sample volumes must be collected, decreasing the temporal resolution of the method. 

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