Calibration of an integrating sphere for determining the absorption coefficient of scattering suspensions.

Measuring the absolute absorption of suspensions of absorbing particles with unknown scattering characteristics is not possible in conventional spectrophotometers or in integrating spheres that have the sample located outside the sphere. A method for the calibration and use of an integrating sphere with a centrally located sample to measure absolute absorption coefficients of scattering suspensions is presented. Under the tested conditions the integrating sphere used in this study was insensitive to changes in the scattering coefficient of the sample but had a nonlinear response to increasing absorption of the sample, which could be corrected with an empirically derived function. This response was analyzed by using a Monte Carlo simulation, and results indicated that amplification of the absorption signal was primarily due to photons reflected from the sphere surface and the baffle reentering the cuvette. The calibration procedure described here may be generally applicable to spheres of different configurati n. An example of the use of the sphere for determining the absorption and scattering coefficients of marine phytoplankton samples is presented.

[1]  Robert R. Bidigare,et al.  Phytoplankton light absorption and the package effect in California coastal waters , 1993 .

[2]  T. T. Bannister.  Estimation of absorption coefficients of scattering suspensions using opal glass , 1988 .

[3]  J. Kirk,et al.  Monte Carlo study of the nature of the underwater light field in, and the relationships between optical properties of, turbid yellow waters , 1981 .

[4]  Annick Bricaud,et al.  Optical efficiency factors of some phytoplankters1 , 1983 .

[5]  Helmut Maske,et al.  Specific in vivo absorption coefficient of chlorophyll a at 675 nm , 1987 .

[6]  Warren L. Butler,et al.  Absorption Spectroscopy In Vivo Theory and Application , 1964 .

[7]  F. P. Incropera,et al.  Absorption, extinction and phase function measurements for algal suspensions of chlorella pyrenoidosa , 1978 .

[8]  B. G. Mitchell,et al.  Algorithms for determining the absorption coefficient for aquatic particulates using the quantitative filter technique , 1990, Defense, Security, and Sensing.

[9]  B. Osborne,et al.  Light and Photosynthesis in Aquatic Ecosystems. , 1985 .

[10]  T. J. Petzold.  Volume Scattering Functions for Selected Ocean Waters , 1972 .

[11]  A. Roos,et al.  Interpretation of integrating sphere signal output for nonideal transmitting samples. , 1991, Applied optics.

[12]  Warren L. Butler,et al.  Absorption of light by turbid materials , 1962 .

[13]  B. Prézelin,et al.  Chromatic light effects and physiological modeling of absorption properties of Heterocapsa pygmaea (=Glenodinium sp.). , 1990 .

[14]  A. Bricaud,et al.  Light attenuation and scattering by phytoplanktonic cells: a theoretical modeling. , 1986, Applied optics.

[15]  D. G. Goebel.  Generalized integrating-sphere theory. , 1967, Applied optics.

[16]  André Morel,et al.  Chlorophyll-specific scattering coefficient of phytoplankton. A simplified theoretical approach , 1987 .