Analysis of Chlorophyll in Leaf and Lichens
Goal:
Assess the feasibility of using OOI hardware to detect chlorophyll in lichens through glass and underwater
Method:
Fluorescence
Introduction:
Customer is hoping to use a probe to measure chlorophyll in water (algae) and on rocks (lichens). He currently has a USB2000-VIS-NIR and a 400 micron optical fiber. He would like to purchase a reflection probe and light source for measuring chlorophyll in situ.
Experimental Conditions:
Measurements were made with the reflection probe held in our probe holder at 90 degrees relative to the sample surface. The probe holder was placed on the leaf or lichens sample for the fluoresence measurements.
Hardware Used:
USB2000-FLG (USB2E4876)
LS-450
R400-7-VIS/NIR
RPH-1
Experimental Parameters:
Integration Time (msec): 25 – 200
Spectra Averaged: 1 – 10
Boxcar Smoothing: 3
Measurement Mode:
Fluorescence
Results:
For the leaf measurements shown in Figure 1, we were able to make measurements through glass and in water. The large peaks you see at 470 nm and 920 nm are related to the LED with the peak at 920 nm due to second order effects from the grating. Order sorting filters are not included on our fluorescence spectrometers because the filter will decrease your sensitivity to low level fluorescence. When the measurements are made through glass, there is a lot of LED light scattered back into the reflection probe.
For the lichen samples shown in Figure 2, the peaks were not as high intensity or resolved. This may be related to either the type or concentration of chlorophyll in the samples. When you compare the lichen spectra to the spectra measured for the other side of the lichen samples (bark and bark2), there are spectral differences which seem to be related to the presence of chlorophyll. When I tried to measure the lichen samples through glass, I didn’t see a lot of difference between the bark and lichen side of the sample. With the lower level of fluorescence observed for the lichen samples, we may not be sensitive enough to detect the chlorophyll in the lichen samples when we are making measurements through glass.
Figure 1:
Figure 2:
