The use of a synthetic zeolite (type 4A, Union Carbide Corp., Linde Div., New York, N.Y.) in a procedure for the preparation of pure cell wall fractions proved successful for many gram-positive, gram-negative, and acid-fast bacteria, as well as for some fungi. The technique, however, was found to be limited in effectiveness for Rhodospirillum rubrum, Gaffkya tetragena, and Sarcina lutea, and not applicable to preparations of heat killed microorganisms. The possible mechanisms of zeolite action, together with the effect of the disruptive procedure on the chemical composition of cell wall fragments, were investigated also. The zeolite (type 4A) used in these experiments was obtained from the Union Carbide Corp., Linde Div., New York, N.Y. It is a synthetic crystalline zeolite, of a type not found in nature, that has a structure completely different from the gel type aluminosilicates usually referred to as
Liquid flow cells have been fabricated to prepare an array of QCMs operating simultaneously for detection and identification of VOCs in water. Two signals, a tlequency response and a damping voltage response, were obtained per resonator. A blank QCM was used as a reference to account for changes in liquid density and viscosity. Nine different polymer coatings applied using a spin coat technique have been examined for VOC response under liquid flow conditions. A matrix of three classes of VOCs were examined for each coating with four chemicals in each class. The three classes of VOCs are polar, nonpolar and chlorinated. A pattern recognition technique, called visually empirical region of influence (VERI), was used to cluster the responses in n-dimensional space. Chemicals within a class varying by only one methyl group ( e g , toluene and xylene) are easily discriminated using only two different coatings with three different QCM responses. All chemicals were easily separated and detected with a total of 5 films and 6 responses with >99% accuracy.Keywords: quartz crystal microbalance (QCM), thickness-shear mode (TSM) resonator, volatile organic compound (VOC), visually empirical region of influence (VERI).
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