Sensor based analyses

Should the sample be filtered/treated to remove large particles, cells, or other potential interferants Many samples may require carefully optimized strategies for pretreatment prior to analysis. This is not just a requirement for sensor-based analysis and much food/environmental samples have well-established protocols for cleanup. Such elements can affect the analysis as they may block microfluidic devices or cause nonspecific binding to a number of commercially available systems. These factors are critical in sample preparation and should be investigated, where relevant. However, where possible for ease of analysis/reduction of costs pretreatments need to be kept to a minimum. 

Sensor-based methods. Whilst many methods use sensors, the simplest being temperature measurement, this terminology is often used to cover viscosity, pH, oxygen and humidity determination, etc. These are true in-line techniques and offer rapid, inexpensive real-time analysis. Humidity determination in drying ovens is a common example. 

Y. Ermolenko, T. Yoshinobu, Y. Mourzina, K. Furuichi, S. Levichev, M.J. Schoning, Y. Vlasov, and H. lwasaki, The double K+/Ca2+ sensor based on laser scanned silicon transducer (LSST) for multi-component analysis. Talanta 59, 785—795 (2003). 

Munson MS, Hasenbank MS, Fu E, Yager P (2004) Suppression of non-specific adsorption using sheath flow. Lab Chip 4 438 145 Munson MS, Hawkins KR, Hasenbank MS, Yager P (2005) Diffusion-based analysis in a sheath flow microchannel the sheath flow T-sensor. Lab Chip 5 856-862... 

The most thoroughly developed sensor based on a solid electrolyte is the oxygen sensor using a stabilised zirconia electrolyte. This type of sensor is one of the most successful commercial sensors to date. They are widely used in industry, especially in the analysis of exhaust gases from combustion engines. The following configuration is used in the Oj sensors ... 

G. C. Nenninger, M. Piliarik and J. Homola, Data analysis for optical sensors based on spectroscopy of surface plasmons, Meas. Sci. Technol. 13 2038-2046 (2002). 

Sensors based on integrated reaction and detection are the most varied and numerous among flow-through sensors and those that will predictably experience the greatest development in the near future. Both enzyme sensors and immunosensors are bound to become virtually irreplaceable tools in some areas of social interest including clinical and environmental analysis. While other sensors inspired by those discussed in Sections 3.4 and 3.5 may... 

The aim of the study was to create high-sensitive point-contact type gas sensors based on derivatives of 7,7,8,8-tetracyanoquinodimethane (TCNQ) and to test them in analysis of exhaled air for diagnosis and monitoring of human organism state. 

Ammonia Gas Sensor. The determination of ammonia is important in process analysis. An ammonia gas electrode is usually used for this purpose. However, volatile compounds such as amines often interfere with the determination of ammonia. Therefore, a sensor based on amperometry is desirable for the determination of ammonia. 

The use of ISEs with ion-selective membranes based on plasticized PVC, as well as glass pH electrodes, is limited to the analysis of aqueous solutions. On the other hand, sensors based on conducting polymer membranes are usually insoluble in organic solvents, which extends the range of possible applications. Electrosynthesized polypyrrole doped with calcion works as a Ca2+ sensor that can be applied as indicator electrode in the titration of Ca2+ with NaF in mixed solvents, such as water-methanol (1 1) and water-ethanol (1 1) [52], Another example is the use of polyaniline as indicator electrode in order to follow the acid-base precipitation titration of trimeprazine base with tartaric acid in isopropanol solution (see Procedure 5). 

Solid-state ion sensors with conducting polymers as sensing membranes have also proved useful in some applications. Of particular importance are the pH sensors based on polyaniline that can be also applied in non-aqueous solutions. Polypyrrole-based sensors for nitrate also show great promise for water analysis. However, in addition to these two excellent examples, a large number of functionalized conducting polymers have been synthesized already, and these materials may offer unique possibilities for fabrication of durable, miniaturized ion sensors. 

The objective is to describe a new non-enzymatic urea sensor based on catalytic chemical reaction. The sensor consists of screen-printed transducer (IVA, Ekaterinburg, Russia) and catalytic system which is immobilized on the transducer surface as a mixture with carbon ink. The sensor is used for measuring concentration of urea in blood serum, dialysis liquid. Detection limit is 0.007 mM, while the correlation coefficient is 0.99. Some analysis data of serum samples using the proposed sensor and urease-containing sensor (Vitros BUN/UREA Slide, Johnson Johnson Clinical Diagnostics, Inc.) are presented. 

There is a continuing demand for the application of electrochemical sensors with a good quality/cost performance not only in comparison to sensors based on other transducer mechanisms but also to some standard analytical methods. Electrochemical Sensor Analysis (ECSA) presents novel theoretical considerations along with detailed applications of electrochemical (bio)sensors. The combination of both theoretical and practical aspects provides a comprehensive forum that integrates interdisciplinary research and development, presenting the most recent advances in applications in various important areas related to everyday life. Additionally ECSA reflects that electrochemical sensor analysis is already a well established research and applied area of analytical chemistry. 

Egorov, O. B., Fiskum, S. K., O Hara, M. J., and Grate, J. W., Radionuclide sensors based on chemically selective scintillating microspheres Renewable column sensor for analysis of 99Tc in water, Anal. Chem., 71, 5420-5429, 1999. 

Semiconductor nanocrystals are being used as fluorescent biological labels. It is likely that sensors based on nanotechnology will revolutionize health care, climate control and detection of toxic substances. It is quite possible that we will have nanochips to carry out complete chemical analysis. Such nano-total analysis systems will have to employ new approaches to valves, pipes, pumps, separations and detection. 

During the last decade the number of application of MIP-based sensors has increased dramatically. The high selectivity and affinity of MIPs for target analytes make them ideal recognition elements in the development of sensors. Capacitive (Panasyuk etal., 2001), conductimetric (Piletsky et al., 1995), field effect (Lahav et al., 2004), amper-ometric (Kritz and Mosbach, 1995), and voltammetric (Pizzariello et al., 2001), electrochemical transduction systems have been used. Sensors based on conductimetric transduction have been developed by Piletsky et al. (1995) for the analysis of herbicides. A system using a TiC>2 sol-gel system, and with a linear range of 0.01-0.50 mg L-1 for atrazine, without interference of simazine, and chloroaromatic acids has been described by Lahav et al. (2004). 

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