Determination of the Concentration of Chlorella vulgaris Beij by Visible Spectrophotometer

[Objective]This study aimed to provide technical parameters for large-scale production and industrial development of Chlorella vulgaris Beij.[Method]By using 721 visible spectrophotometer,the transmitted light intensity of different concentrations of C.vulgaris liquid under different wavelengths was measured to normalize the absorbance data,thus determining the optimal wavelength for the growth of C.vulgaris and the concentration of C.vulgaris liquid under the optimal wavelength.The regression equation of absorbance at the optimal wavelength and C.vulgaris concentration was obtained to derive the formula between equivalent concentration C and transmitted light intensity I,thus calculating the equivalent concentration of 0.25-fold C.vulgaris liquid under different transmittance.[Result]The transmitted light intensity of C.vulgaris reached the peak at 670 nm,indicating that 670 nm is the optimal wavelength for measuring C.vulgaris concentration.The regression equation between absorbance and C.vulgaris concentration was y=-1.479 7＋0.987x,with a correlation coefficient of 0.991,suggesting a high correlation between these two factors.The formula of equivalent concentration C and transmitted light intensity I was C=-ln（I/I0）/LK,where L indicates the optical path length（cuvette width）and K indicates the average cross-sectional area of C.vulgaris cells.[Conclusion]It is feasible to investigate indirectly the concentration of C.vulgaris with a spectrophotometer,which can be used to determine the optimal dehydration time of C.vulgaris.

Spectroscopy and Light Emitting Diodes Based System in Characterizing External Beam Therapy 3 Films for Solar Ultraviolet Measurement

Gafchromic external beam therapy 3(EBT3)film has widely been used in medical field applications.Principally,the EBT3 film’s color gradually changes from light green to darker color under incremental exposures by ionizing or even non-ionizing ultraviolet(UV)radiation.Peak absorbance of the EBT3 film can be used to predict absorbed doses by the film.However,until today,related researches still rely on spectrometers for color analysis of EBT3 films.Hence,this paper presents a comparative analysis between results produced by the spectrometer and a much simpler light-emitting diode-photodiode based system in profiling the color changes of EBT3 films after exposure by solar UV radiation.This work has been conducted on a set of 50 EBT3 samples with incremental solar UV exposure(doses).The wavelength in the red region has the best sensitivity in profiling the color changes of EBT3 films for low solar UV exposure measurement.This study foresees the ability of blue wavelength to profile films with a large range of solar UV exposure.The LED(light emitting diode)-based optical system has produced comparable measurement accuracies to the spectrometer and thus,with a potential for replacing the need for a multipurpose spectroscopy system for simple measurement of light attenuation.