on the thickness s 1 of the reagent 704 fig9 a shows a portion of that diffraction pattern at a time before immersion of the bioprobe 700 shown on a portion of the one dimensional ccd of the spectrometer 820 fig9 b shows a portion of a diffraction pattern at a time after immersion of the bioprobe 700 shown on the portion of the one dimensional ccd of the spectrometer 820 as a comparison of fig9 a and 9b shows the diffraction pattern has shifted based on the amount of shift whether or not antibodies 736 which are complementary with the antigen reagent 704 are present in the sample solution 734 can be determined by sampling the one dimensional ccd of the spectrometer at various times after immersion of the bioprobe 700 the rate of change of the shift and thus the concentration of any complementary antibodies 736 in the sample solution 734 can be derived in the first embodiment of my invention described with reference to fig8 the optical waveguides 806 810 814 816 and 828 are preferably single mode optical fiber such as communications grade optical fiber for example for example 630 nm single mode fiber sold by spectran or corning may be used however multi mode optical fiber may be used instead for example graded index fiber sold by spectran or corning may be used the optical fiber is preferably at least 3 u03bcm in diameter and more preferably 100 u03bcm in diameter the light coupler 808 and 812 are preferably 34 y 34 or two by one optical couplers for example two by one optical couplings.