Portable analytical system

As regards general technical features, (bio)chemical sensors will foreseeably result in increased automation, simplification and miniaturization, three of their inherent attributes (Fig. 1.8). Operationally, those features assuring quality in the results (Fig. 1.16.B), as well as others including durability, expeditiousness, robustness, cost-effectiveness, compatibility with complex samples, and ease of incorporation into portable analytical systems... 

Current studies focusing on biosensing methods aim to achieve more sensitive, robust, reproducible, user-friendly, and portable analytical systems. To achieve these goals almost every biosensing format has ntilized immunoglobulins (antibodies) as the molecular recognition element, leading to the adoption of the term immunobiosensor. ... 

Portable Analytical Systems for On-Site Diagnosis of Exposnre to Pesticides and Nerve Agents... 

The prototype of the portable analytical system, shown in Figure 4, consists of a disposable electrode and a portable electrochemical analyzer. This system can also be integrated with a flow injection system or a senquential flow injection system for rapid and on-site detection of OP exposure. 

Figure 4. Calibration curve for serial dilution of phenol in pH=7 buffered water at an instrument-to-analyte distance of 10 m, using the portable field system.

In parallel with improvements in chemical sensor performance, analytical science has also seen tremendous advances in the development of compact, portable analytical instruments. For example, lab-on-a-chip (LOAC) devices enable complex bench processes (sampling, reagent addition, temperature control, analysis of reaction products) to be incorporated into a compact, device format that can provide reliable analytical information within a controlled internal environment. LOAC devices typically incorporate pumps, valves, micromachined flow manifolds, reagents, sampling system, electronics and data processing, and communications. Clearly, they are much more complex than the simple chemo-sensor described above. In fact, chemosensors can be incorporated into LOAC devices as a selective sensor, which enables the sensor to be contained within the protective internal environment. Figure 5... 

The choice of test equipment and methods has become extremely wide and, apart from large, integrated, electronic colorimetric and spectrophotometric instrumentation, field personnel can choose from miniburettes, direct-reading titrators (modified syringes), digital titrators, drop tests, tablet tests, permanent color standard comparators, indicator papers, portable colorimeters, immunoassays, etc. Today, field-test methods tend to be tailored by equipment manufacturers to their own analytical systems, and consequently the specified use of particular standard methods for the examination of water, from any one technology or official body, is probably not realistic. Rather it is the fitness-for-purpose rule that is more relevant. 

The technical development is still very rapid and addresses the growing need within process monitoring. The current trend includes further improvement of instrument design for smaller and more rugged equipment, integration into automated analytical systems and miniaturisation for multiple installations and portability. 

However, electrochemically based transduction devices are more robust, easy to use, portable, and inexpensive analytical systems [45]. Furthermore, electrochemical biosensors can operate in turbid media and offer comparable instrumental sensitivity. Many electrochemical sensing and biosensing devices were reported [46-48]. 

The first prototype of a technologically improved IWAO was developed and tested with a membrane based on a new H+-selective ketocyanine dye and a commercial cadmium ionophore [39]. Its incorporation in an IWAO allows a highly sensitive and portable optical system to be obtained for an situ chemical analysis as well. The authors propose a flow injection analysis (FIA) system for the determination of cadmium in water samples using a cadmium-selective IWAO, as an alternative method to the ones generally used in analytical control laboratories. It permits enhanced sensitive signals in short response times by taking advantage of the very thin membranes deposited over the circuit. 

One of the major advantages of SPME is that it is a solventless sample preparation procedure, so solvent disposal is eliminated [68,131], SPME is a relatively simple, straightforward procedure involving only sorption and desorption [132], SPME is compatible with chromatographic analytical systems, and the process is easily automated [131,133], SPME sampling devices are portable, thereby enabling their use in field monitoring. 

Analytical Procedure. The cold-trap gas phase mercury detection system was designed and used for both laboratory and shipboard measurements of mercury in seawater. The Coleman Instruments mercury analyzer (MAS-50) was incorporated into the analytical system because of its portable and convenient design. However, the effective use of this simple one-element atomic absorption unit requires scrupulous attention to blank determinations for each seawater sample. For example, the undetected presence of either naturally occurring or sampling induced volatile organics which may absorb at the mercury wavelength in the seawater sample can be a serious error. Such artifacts were observed when acidifled seawater samples were stored in low density polyethylene bottles (21), Therefore, the analytical procedure used to determine the mercury concentration in a seawater sample consists of the following steps ... 

The SCANS is used in conjunction with an analytical system such as a portable Raman spectrometer or a portable isotopic neutron spectrometer to identify the agent inside a vial or bottle so the correct reagent can be selected to neutralize it. A 4-liter bottle of reagent is placed in the reactor case,... 

Concerning the preanalytics that have to be used, two main concepts are available for the application of enzyme electrodes to different fields of analysis. Clinical chemists nowadays are interested in autoanalyzers characterized by high measuring frequency as well as in portable bedside-type analytical systems with extremely short lag time between sample withdrawal and analysis result. On the other hand the optimal control of food production as well as bioprocesses requires the analysis of the substances of interest in a continuous or quasicontinuous way. Therefore, enzyme-electrode-based analytical systems for the application of highly diluted as well as undiluted media have been developed and commercialized. 

---