Sensor array detection

Sensor array detection also is needed because these devices can be micro-fabricated with very low dead volumes they require no support gases for their operation, and they can be fabricated with a variety of selectivities, which can be used for vapor recognition and for the deconvolution of overlapping peaks. This can reduce the resolution requirements for the colunm. Sensor detectors usually have lower sensitivity than do detectors incorporated in laboratory gas chromatographic instruments. Low detector sensitivity, coupled with the very low concentrations often associated with air monitoring, requires the use of a sorption preconcentrator for sample enrichment prior to separation and detection. 

Multiple electrodes have been used to obtain selectivity in electrochemical detection. An early example involved the separation of catecholamines from human plasma using a Vydac (The Separation Group Hesperia, CA) SCX cation exchange column eluted with phosphate-EDTA.61 A sensor array using metal oxide-modified surfaces was used with flow injection to analyze multicomponent mixtures of amino acids and sugars.62 An example of the selectivity provided by a multi-electrode system is shown in Figure 2.63... 

Chitosan-clay bio-nanocomposites are very stable materials without significant desorption of the biopolymer when they are treated with aqueous salt solutions for long periods of time. In this way, they act as active phases of electrochemical sensors for detection of ions (Figure 1.8). The particular nanostructuration of the biopolymer in the interlayer region drives the selective uptake of monovalent versus polyvalent anions, which has been applied in electrode arrays of electronic tongues [132]. 

In addition, a linear dependence was found between the concentration of DNB and its fluorescence response profile. All these characteristics demonstrate that this sensor array is suitable for use in detecting explosive vapors. 

In contrast to other analytical methods, ion-selective electrodes respond to an ion activity, not concentration, which makes them especially attractive for clinical applications as health disorders are usually correlated to ion activity. While most ISEs are used in vitro, the possibility to perform measurements in vivo and continuously with implanted sensors could arm a physician with a valuable diagnostic tool. In-vivo detection is still a challenge, as sensors must meet two strict requirements first, minimally perturb the in-vivo environment, which could be problematic due to injuries and inflammation often created by an implanted sensor and also due to leaching of sensing materials second, the sensor must not be susceptible to this environment, and effects of protein adsorption, cell adhesion, and extraction of lipophilic species on a sensor response must be diminished [13], Nevertheless, direct electrolyte measurements in situ in rabbit muscles and in a porcine beating heart were successfully performed with microfabricated sensor arrays [18],... 

Zheng, G. F. Patolsky, F. Cui, Y. Wang, W. U. Lieber, C. M., Multiplexed elec trical detection of cancer markers with nanowire sensor arrays, Nat. Biotechnol. 2005, 23, 1294 1301... 

Bajaj A, Miranda OR, Kim I-B, Phillips RL, Jerry DJ, Bunz UHF, Rotello VM (2009) Detection and differentiation of normal, cancerous, and metastatic cells using nanoparticle-polymer sensor arrays. Proc Natl Acad Sci 106 10912-10916... 

Kirby R, Cho EJ, Gehrke B, Bayer T, Park YS, Neikirk DP, McDevitt JT, Ellington AD (2004) Aptamer-based sensor arrays for the detection and quantitation of proteins. Anal Chem 76 4066-4075... 

J.W. Gardner, A. Pike, N.E de Rooij, M. Koudelka-Hep, P.A. Clerc, A. Hierlemann, and W. Gopel. Integrated Array Sensor for Detecting Organic-Solvents , Sensors and Actuators B26 (1995), 135-139. 

M. Graf, U. Frey, S. Taschini, and A. Hierlemann. Microhotplate-Based Sensor Array System for the Detection of Environmentally Relevant Gases , Analytical Chemistry 78 (2006), 6801-6808. 

T. A. Dickinson, J. White, J. S. Kauer, and D. R. Walt. 1996. A Chemical-Detecting System Based on a Cross-Reactive Optical Sensor Array. Nature 382 697-700. 

Schalwig et al. have tested the feasibility of using a SiC MOS capacitor sensor containing a contact metal of 40-nm TaSi plus 45-nm Pt to detect NO and HC after the catalytic converter. This was carried out by simulating lean burn engine exhausts [116]. It was observed that the sensor signal increased for NO detection and decreased for HC detection. This could permit this sensor to be used in a sensor array to differentiate these two gases. 

Carvalho, E. R., Consolin Filho, N., Venancio, E. C., Osvaldo, N. O., Jr., Mattoso, L. H. C., and Martin-Neto, L. (2007). Detection of brominated by-products using a sensor array based on nanostructured thin films of conducting polymers. Sensors 7, 3258-3271. 

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