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Abstract. Fiber-optic sensors were developed for monitoring dissolved carbon dioxide in water samples in the 0 to 900 ppm concentration range. A pH-sensitive fluorescent dye (HPTS) was reacted with a cationic quaternary ammonium salt to form an ion pair which was electrostatically bound to the surface of particles of aminocellulose which then were dispersed into a gas-permeable silicone polymer. The green fluorescence of the base form was monitored using a fiber optic fluorometer. The use of the aminocellulose enhanced the stability and lifetime of the sensor and also increased the fluorescence of the sensor membrane because the particles act as scattering centers. The characteristics of the sensors are described with respect to dynamic range, reproducibility, long-term stability and temperature dependence.

Within the last several years Archibald has indicated how molecular weights and sedimentation coefficients may be calculated from the ultracentrifuge data during the period of ap roach toward sedimentation equilibrium in a sector shaped cell. Applications of this method have been made to smat molecules by Porath and by Brown, Kritchevsky and Davies. Gutfreund and Ogston, and Baldwin have devised an independent method fqr the determination of sedimentation coefficients based on the flow of solute past a fixed surface in the cell, and have applied this to the study of polypeptides. In the present study we have correlated the two methods so that they may be applied simultaneously to the data obtained in a single experiment. The method employs phase-contrast schlieren optics of Wolter, Armbruster, Kossel and Strohmeier and Trautman and Burns. A two-coordinate comparator is used to measure diagrams from standard ultracentrifuge cells as well as from a boundary-forming cell described by Kegeles, and used here as a refractometer. We have found that both molecular weights and Sedimentation coefficients may be determined reliably within one hour of centrifugntion for raffinose and for bovine plasma albumin, by the proper choice of speed.

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