Mass-sensitive sensor arrays

MIP sensor elements are also suitable for the analysis of multicomponent samples. The cost-effective, miniaturised, non-covalent MIP sensor arrays, when combined with computational data evaluation, make weak artificial recognition phenomena highly applicable for smart sensors. In comparison to gas or liquid chromatography, the results with mass-sensitive MIP sensors are faster and cheaper to obtain [32]. For effective on-line monitoring, the ideal MIP sensor or actuator should allow reversible analyte enrichment without dependencies on intermediate washing procedures (with organic solvents, for example). 

The typical dimensions of these microcantilevers are 50-200 pm long, 10-40 pm wide and 0.3-2 pm thick. The mass of the microcantilever is a few nanograms. The primary advantage of the microcantilever method originates from its sensitivity that is based on the ability to detect cantilever motion with sub-nanometer precision as well as the ease with which it may be fabricated into a multi-element sensor array. 

Presearch is a British-based company, which offers a variety of instruments from different manufacturers. These include the Prometheus SAS-FMS system, which is billed as the first odor and volatile organic compounds (VOC) analyzer, which combines a sensitive fingerprint mass spectrometer (FMS) with a sensor array system (SAS). This system allows direct analysis of samples without pretreatment [25]. In addition, the company offers the Astree II e-tongue sensor array, which consists of seven sensors on a probe, which can be automatically lowered into a vessel containing the sample to be analyzed. The process is electrochemically based on the response of the sensors being dependent on the type and quantity of molecules present in the sample [26]. 

Lange D, Hagleitner C, Hierlemann A, Brand O, Baltes H (2002) Complementary metal oxide semiconductor cantilever arrays on a single chip mass-sensitive detection of volatile oigrmic compounds. Anal Chem 74 3084-3095 Lange U, Roznyatovskaya NV, Mirsky VM (2008) Conducting polymers in chemical sensors and arrays. Anal Chim Acta 614 1-26... 

Mass-produced cantilever sensors, however, have the potential to satisfy the conditions of selectivity, sensitivity, miniature size, low power consumption, and real-time operation [5, 6], Microcantilevers are micromachined from silicon or other materials and can easily be fabricated in multiple-element arrays. They resemble miniature diving boards measuring 100 to 200 pm long by about 20 to 40 pm wide by 0.3 to 1 pm thick and having a mass of a few nanograms. Their primary advantage originates from their sensitivity, which is based on the ability to detect their motion with subnanometer precision. 

Because quartz crystal microbalances are compact and sensitive, a large literature has developed on their use as sensors of both chemical and biomolecular reactions and processes at surfaces. A current review of this literature, with 176 references, is by Marx [44]. To quote from the abstract of this review The technique possesses a wide detection range. At the low mass end, it can detect monolayer surface coverage by small molecules or polymer films. At the upper end, it is capable of detecting. ..complex arrays of biopolymers and biomacromolecules, even whole cells. Another important and unique feature of the technique is the ability to... 

HPLC with UV-based diode array detection (DAD-UV) or electrochemical detection is normally used to determine ascorbic acid. Many types of electrochemical determinations of ascorbic acid have been proposed. Although the electrochemical determinations using enzyme-based biosensors exhibited high specificity and sensitivity, these methods suffer in the fabrication of the electrodes and in automatic analysis. Recently, chemically modified screen-printed electrodes have been constructed for the determination of ascorbic acid. This is one of the most promising routes for mass production of inexpensive, reproducible, and reliable electrochemical sensors. 

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