Metal oxide-based semiconductor gas sensors have been exploited for detecting various odorous components generated in the process of aging and/or putrefaction of beef, such as ethyl acetate, isoamyl alcohol, acetoin, and so on. Among various sensor elements tested, WO₃(5wt%)-ZnO showed the highest sensitivity to ethyl acetate (20ppm in wet air) at 500°C. On the other hand, acetoin could be detected with excellent sensitivity and selectivity by WO₃(0.5wt%)-ZnO element at 300°C. The effect of WO₃ additive was evalutated in the catalytic oxidation of acetoin over ZnO-based materials. As a result, the increase in acetoin sensitivity was found to be correlated with the catalytic activity in oxidative dehydrogenation of acetoin to diacetyl. These two elements obtained appeared to be applicable to evaluate beef freshness. Actually, it was confirmed that the sensitivities of these sensors to the headspace volatiles of the beef kept at 5°C increased gradually during the preservation term of 5 days.

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Four kinds of tin-oxide gas sensors are installed in a home of a solitary elderly person and the sensor outputs are monitored to know the activity of the aged. These sensors are designed to detect a combustible gas(CGS), ammonia(AMS), carbon monoxide(COS) and nitrogen dioxide(NXS), respectively. As the monitoring results indicate, outputs of the sensors are related with daily living patterns. NDVA indeces especially have periodicity. NDVA is a value which is obtained by an output of AMS divided by an output of CGS, namely NDVA=V(AMS)/V(CGS). The periodical characteristics indicate the daily living patterns of the aged and the system can judge whether the person has been spending a normal life or not. The indoor activity(IA) is derived as a sum total of square of each slipped value from a mean value of a daily sensor-level. The average of IA is about 12 in the experimental house.

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There are few works on the distributed sensing of pH, although the point sensing of pH is well establishied. In this work, we propose a new distributed sensing system of pH based on color imaging of pH-indicator dye coatings. The RGB imaging data from a CCD color camera were related to pH using the x, y, z values of CIE chromaticity. The pH value at each pixel point was determined by artificial newral network pattern recognition method using the relationship between the xyz values and pH. It has been found that the use of phenol red/agar gel, methyl red/agar gel coatings shows satisfactory distributed sensing of pH on the coatings.

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A monolithically integrated taste sensor was constructed using a surface photovoltage(SPV) technique. The contactless approach of the SPV method provides a simple electrode structure with patterning flexibility. Polyvinylbutyral membrane was successfully used to immobilize artifitial lipid membranes as an ion sensitive material. For the sensitivity enhancement, an impedance measurement method combined with a new differential measurement method was proposed and the system was applied to discriminate the quality of sweet substances.
It was finally demonstrated by the preliminary experiment that different kinds of commertial sugars and wines were distinguishable.

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Simultaneous quantitative analyses of biochemical substances were carried out using attenuated total reflection and Fourier transform infrared spectroscopy (ATR/FT-IR) combined with partial least squares. The concentrations of glucose, cholesterol, and triglycerides in human serum were measured simultaneously using the low-temperature ATR/FT-IR. The infrared absorption band of proteins in human serum measured at -2.4°C increased 5 times as large as that measured at room temperature. The increase was based on segregation of biochemical components during solidification process. The correlation coefficients between the concentrations determined by the low-temperature ATR/FT-IR and those determined by the conventional method were over 0.86. The fundamental investigation of simultaneous analysis of two enzymes, amylase and creatine kinase, was performed using ATR/FT-IR at room temperature. The changes in the concentrations of the products specific to the enzymes were measured simultaneously. The correlation coefficients between the concentrations of the products and the enzyme activities were over 0.95. The ATR/FT-IR combined with chemometrics would be a useful technique for a biochemical sensing system with a short turn-around time and easy maintenance.

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A surface acoustic wave (SAW) propagating on 36 deg. rotated Y-cut, X-propagating LiTaO₃ is a pseudo mode with a shear horizontal polarized displacement (SH-SAW). Recent reports have shown that liquid-phase sensor using SH-SAW device can detect electrical properties of liquid with high sensitivity. This paper describes a novel technique for identifying the differences of ionic solutions by use of the SH-SAW sensor in a liquid flow system. The identification principle is based on the time responses of the samples obtained from the flow system. Several kinds of ionic solutions, such as aqueous solutions of HCl, LiCl, etc., are measured and observed evident difference in transient. Using pattern matching based on the transient responses, unknown samples are distinguished perfectly. Moreover, not only kind of ion but also the conductivity and the molar concentration are determined.

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