Sulfur dioxide sensors

Worrell, W.L. and Liu, Q.G. (1984) A new sulfur dioxide sensor using a novel two-phase solid-sulfate electrolyte. 

Yan, Y, Miura, N. and Yamazoe, N. (1996) Construction and working mechanism of sulfur dioxide sensor utilizing stabilized zirconia and metal sulfate. J. Electrochem. Soc., 143 (2), 609-13. 

An on-line analyzer must be packaged much more robustly than a laboratory instrument to withstand the process environment which, for example, may have an explosive atmosphere and significantly variable ambient temperature. It must also be capable of continuous, unattended operation over long periods of time. Clearly, the simpler the instrument the better. Of the methods listed in Table 1, WDXRF, polarized EDXRF, and Pyro-microcoidometry have not been adsqrted to on-line process instrumentation, whereas the other methods have. The relative simplicity of Pyro-EC makes it particularly suitable for adaptation to process instrumentation. The sulfur dioxide sensor is a small, plug-in, low cost electrochemical cell, easily replaceable and with an expected lifetime of over one year. The UV lamp, UV optics, and photomultiplier used in Pyro-UVF are not required. The X-ray tube (or radioactive source). X-ray detector, and X-ray optics used in all the XRF instruments are not required. 

Figure 9.45. Stable response of a Sn02sintered sensor that has been treated with sulfur dioxide. Sensor placed in a tunnelfor 1 month...

Chiou CY, Chou TC (1996) Amperometric sulfur dioxide sensors using the gold-deposited gas-diffusion electrode. Electroanalysis 8 1179-1182... 

A leak in a sulfur dioxide system can be detected by odor, or sulfur dioxide sensors may be used as an alarm in case of leaks in areas where there are no personnel. A small leak can be lo-... 

A leak in a sulfur dioxide system can be detected by odor, or sulfur dioxide sensors may be used as an alarm in case of leaks in areas where there are no personnel. A small leak can be located by the dense white fumes resulting when a 10 percent ammonia solution is dispensed from an aspirator or squeeze bottle in the region where the leak is suspected. A leak can also be located by using an ammonia swab prepared by securing a small piece of cloth or sponge to a wire and soaking it in a 10 percent solution of ammonia. When ammonia vapor is passed over points of leaks, dense white fumes will form where the sulfur dioxide and ammonia come in contact. 

By using different membranes, it is possible to obtain potentiometric sensors for gases such as sulfur dioxide or nitrogen dioxide. Such sensors employ similar (acid-base) or other equilibrium processes. These devices, along with their equilibrium processes and internal electrodes, are summarized in Table 6-2. Membrane coverage... 

Stangelmayer A., Klimant I., Wolfbeis O.S., Optical sensors for dissolved sulfur dioxide, Fresenius J. Anal. Chem. 1998 362 73. 

A new solid state chemical sensor for sulfur dioxide utilizing a sodium sulfate/rare earth sulfates/silicon dioxide electrolyte has been developed. The addition of rare earth sulfates and silicon dioxide to the sodium sulfate electrolyte was found to enhance the durability and electrical conductivity of the electrolyte. The electrolyte exhibits a Nernstian response in the range of SC gas concentrations from 30 ppm to 1 %. 

Figure 6. Characteristic patterns of response of an array of six sensors coated with different phthalocyanines to various vapor exposures. The maximum concentration was 100 ppm for ammonia, sulfur dioxide, and DMMP and 1000 ppm for water, ethanol, air and benzene. The central metal of each phthalocyanine is shown at the top.

Two disparate translation methods are investigated for the measurement of sulfur dioxide. Both involve interaction with an aqueous solution. In the first, collected S(IV) is translated by the enzyme sulfite oxidase to which is then measured by an enzymatic fluorometric method. The method is susceptible to interference from i CWg) efforts to minimize this interference is discussed. The second method involves the translation of SO2 into elemental Hg by reaction with aqueous mercurous nitrate at an air/liquid interface held in the pores of hydrophobic membrane tubes. The liberated mercury is measured by a conductometric gold film sensor. Both methods exhibit detection limits of 100 pptv with response times under two minutes. Ambient air measurements for air parcels containing sub-ppbv levels of SO2 show good correlation between the two methods. 

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