Trends hand-held

Turner, R.B. Brokenshire, J.L., Hand-held ion mobility spectrometers. Trends Anal. Chem. 1994, 13(7), 281-286. 

In the medical field a trend toward hand-held devices based on either reusable or disposable glucose and lactate enzyme electrodes for home control of diabetics and for onsite monitoring of surgery and exercise is evident. 

Table 1 has proved to be useful to describe general trends with respect to field use of analytical instruments. Judgements with respect to the values entered in the matrix are those of the author based on evaluations of literature information and personal experience. GC-IMS [6] refers to a hand-held device based on a short column GC coupled to a CAM-based IMS instrument. A new technology, Transverse Field Compensation Ion Mobility Spectrometry [7], which has been subjected to only a limited amount of study has been included because of an indication of very good real time sensitivity. GC-FPD/FID refers to a gas chromatograph with a single column, a flame photometric detector (FPD), and a flame ionization detector (FID). GC-MS, a gas chromatograph - mass spectrometer, is well known. 

W. F. McClure. Hand-held near infrared spectrometry Status, trends and futuristic concepts. In Near Infrared Spectroscopy Proceedings of the 10th International Conference on Near Infrared Spectroscopy, Kyonjgu, Korea. A. M. C. Davies ed. NIR Publications, Chichester, UK, pp. 131-136, 2002. 

Similar dynamics play in other non-refinery petrochemicals that moved to fly-up conditions in 2004, such as monoethylene glycol (MEG) and styrene. Petrochemical producers had held back investments during the previous several years due to poor returns. The underlying upward trend in demand tightened the sup-ply-demand balance, and restored pricing power to producers hands, enabling them to harvest exceptional margins at this point in the cycle. 

It has already been noted that the flux of material to the rotating disc electrode is uniform over the whole surface, and it is therefore possible to discuss the mass transport processes in a single direction, that perpendicular to the surface (i.e. the z direction). Furthermore, it has been noted that the velocity of movement of the solution towards the surface, is zero at the surface and, close to the surface, proportional to Hence, even in the real situation it is apparent that the importance of convection drops rapidly as the surface is approached. In the Nernst diffusion layer model this trend is exaggerated, and one assumes a boundary layer, thickness 6, wherein the solution is totally stagnant and transport is only by diffusion. On the other hand, outside this layer convection is strong enough for the concentration of all species to be held at their bulk value. This effective concentration profile must, however, lead to the same diffusional flux to the surface (and hence current density) as it found in the real system. 

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