Specific features of methods for express control of liquid and viscous media in environmental monitoring

Abstract

Technological advances lead to emergence of factors and enhancement of factors that have a negative impact on the environment. Solid media are more stable and therefore the strongest influence is experienced by air and aquatic environments. In this situation the role of express control of liquid and viscous media becomes extremely important. Devices for analysis of such media (spectrometers etc.) are expensive and require laboratory conditions. So it is more reasonable to analyze liquid and viscous media in which a deviation from the normal condition has been revealed. This is the main task of express - control in on-site testing of media. The requirements to the express control methods are reliability and accessibility, they must not affect the condition of the medium tested. At present three methods are used:

1. Chemical, i.e., indicator testers. The drawback of this method is that each tester is used tocontrol one-two impact factors. In addition, each medium requires its own tester that has a limited application period.
2. Optical, i.e., exposure of a medium to UV, visible, and IR radiation. The medium must berelatively transparent. The drawback is a limited number of media that can be tested by this method.
3. The method based on the nuclear magnetic resonance (NMR). By measuring relaxationconstants Т₁ and Т₂ of a liquid or viscous medium, it is possible to find very quickly the deviation of its aggregate state from the “normal” one. The only condition for application of the NMR method is the presence of protons or nuclei having magnetic moments in the medium (fluorine, lithium, and sodium). The NMR method is almost universal because more than 90% of liquid and viscous media contain protons. The disadvantage is a large weight and a high cost of the magnetic system for detection of NMR signals. At present a considerable research effort is directed towards modification of the devices for the optical and NMR methods.

The authors have developed a small-size NMR spectrometer for express control of liquid and viscous media that can be connected to a laptop to process results of measurements. Our studies have shown a high efficiency of the NMR method for express control of liquid and viscous media as compared with the chemical and optical methods. A further modification of small-size NMR spectrometers can reduce their cost and make the method marketable.