A Day in the Lab: Chemical Analysis
Today we set about analysing the samples collected from the R.V. Calanus on Monday, to do this we split into three groups of two.
Chlorophyll
Measuring the chlorophyll gives an indication of the phytoplankton concentration at depth. It would be expected to decline with depth with the decreasing light. However certain conditions can lead to a deep chlorophyll maximum developing, a chlorophyll maximum indicates the euphotic zone.
Procedure:
1.      Used exact samples of Chlorophyll to create regression graph and equation
2.      Pour the acetone from the Chlorophyll vials taken on Calanus into the test tube
3.      Place test tube into the fluorometer and read the fluorescence value on the screen
4.      After repeating each reading 5 times and entering data into spreadsheet, pour the liquid into the waste bucket
5.      Use acetone to rinse the test tube and pour into waste bucket
6.      Repeat steps 2-5 for each of the 50 Chlorophyll vials
7.      Use the slope equation in order to calculate the Chlorophyll values
Dissolved Oxygen
For the oxygen measurements, we titrated the samples with thiosulphate to allow us to calculate the dissolved oxygen concentrations for each depth. If there is stratification (no mixing) we would expect higher oxygen concentrations near the surface, decreasing with depth.
Procedure:
1.      Add 1ml sulphuric acid to each oxygen sample bottle and shake
2.      Transfer 50ml of this acidified solution to a conical flask
3.      Titrate the sample with thiosulphate until the sample is a faint yellow colour
4.      Add starch dye to darken sample colour
5.      Titrate again until sample is colourless
6.      Make a note of how much thiosulphate is used to titrate each sample to give the titration value
7.      Titrate standards and blanks for accuracy
Inorganic Phosphate
Phytoplankton uptake phosphate in its inorganic form, the measuring of its quantities in our collected samples can help to relay phytoplankton distribution throughout the water column.
Procedure
1.      Label flasks from sample 1-30 and include a ‘blank’.
2.      Filter samples and then measure 50ml into corresponding flask.
3.      5 standards made for calibration (6.45ᶮmol L-1,3.22ᶮmol L-1,1.29ᶮmol L-1,0.52ᶮmol L-1,0.26ᶮmol L-1).
4.      Use pipette to add 5ml of mixed reagent to each flask.
5.      Place in the helios spectrometer and record data produced.
6.      Plot a calibration curve of phosphate with standard concentrations. Using the equation of this line calculate your actual phosphate amounts.
Today was a good day for science.
See you next with more boating activities.... xxx