License: This is an open access protocol distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Protocol status: Working
We use this protocol and it's working
Created: July 21, 2023
Last Modified: March 27, 2024
Protocol Integer ID: 85320
Funders Acknowledgement:
Simons Foundation
Grant ID: 549937
Simons Foundation
Grant ID: 723789
Abstract
Here we describe a protocol for measuring chlorophyll-a and pheophytin-a from microalgae by using Turner Designs (10-AU)
Guidelines
The entire procedure should be carried out as much as possible in subdued light (Green) to prevent photodecomposition.
All glassware should be clean and acid free to prevent chlorophyll-a degradation.
Waste disposal:
Follow all laboratory waste disposal guidelines regarding the disposal of acetone, DMSO solutions.
Protocol materials
Chlorophyll-a from spinachMerck MilliporeSigma (Sigma-Aldrich)Catalog #C5753-1MG
100 mL clear “powder free” magnesium carbonate solution
900 mL HPLC grade acetone
AcetoneVWR InternationalCatalog #270725-4X2L
Mix in an amber reagent bottle.
Acetone/DMSO extraction solvent
Mix three parts 90% acetone and two parts of HPLC grade DMSO (Shoaf and Lium 1975)
DMSO (CAS grade)VWR International
0.1 N HCl
Dissolve one part of 12 Mass Percent HCl in 119 parts of MilliQ water
12 N Hydrochloric acidVWR International
Prepare Chlorophyll-a standard
Prepare Chlorophyll-a standard
Primary stock: ≅10 mg/L
Dissolve 1 mg Chlorophyll-a in a 100 mL glass volumetric flask by 90% acetone, top to 100 mL.
Chlorophyll-a from spinachVWR InternationalCatalog #C5753-1MG
Fill cuvette and place it in udrop plate, measure absorbance at 664 nm
Chlorophyll-a_mg/L = 11.42 X Absorbance at 664 nm, where 11.42 is the extinction coefficient of chlorophyll-a at 664 nm.
Label Amber vials with the actual concentration of chlorophyll-a stock solution
Aliquote 5 mL to Amber vial with glass serological pipet (5 mL)
Store at -80 °C to -50 °C
Second calibration standard: (≅400 ug/L)
Warm up primary stock to room temperature and transfer 4 mL primary stock to a 100 mL glass volumetric flask
Top with 90% acetone to 100 mL
Measure absorbance at 664 nm.
Chlorophyll-a_mg/L = 11.42 X Absorbance at 664 nm, where 11.42 is the extinction coefficient of chlorophyll-a at 664 nm.
Aliquote 5 mL to amber vials, label cryobox with actual concentration and store at -80 °C to -50 °C .
Working calibration standard (≅16 ug/L)
Warm up second calibration standard and transfer 2 mL solution to a 50 mL glass volumetric flask
Top with 90% acetone to 50 mL
Extract chlorophyll sample and blank
Extract chlorophyll sample and blank
Extract samples on the filter
Label 20 mL scintillation vials and place them in scintillation vial rack.
Transfer sample and blank filter into scintillation vial
Add 5 mL Acetone/DMSO extraction solvent
Cap the vial, and vortex.
Cover the scintillation vials with another scintillation rack.
Let samples be extracted for 00:20:00 at Room temperature
20m
Vortex samples and allow samples to be extracted for another00:10:00
10m
Extract liquid samples
Freeze liquid sample and blank
Add extraction solvent into frozen sample
Cap the vial, vortex and place sample in the dark at room temperature for 00:20:00
20m
Vortex and place sample in the dark for another 00:10:00
10m
Daily calibrate
Daily calibrate
Allow Turner to warm-up for at least 15 minutes.
Place the solid secondary standard in Turner, wait 15 seconds for the reading to stabilize.
Record the reading on the solid standard calibration record sheet.
Reading should be less than 10% of the previously determined post calibration value.
Otherwise, calibrate Turner by liquid standard before measuring samples (Go to the last step: Calibrate Turner)
Measure chlorophyll-a and pheophytin-a of standard
Measure chlorophyll-a and pheophytin-a of standard
Use polypropylene pipet tip to transfer 5 mL 90% acetone to disposable glass tube, wipe the outside of the tube dry with kimwipe and place in the instrument. Replace the light cap.
Wait about 15 seconds for the reading to stabilize, and zero the instrument on the sensitivity setting.
Transfer 5 mL working calibration standard (prepared in ) to a disposable glass tube, measure the fluorescence. Log the reading as "standard before acidification (Rb)".
Add 150 ul 0.1N HCl to working calibration standard.
Carefully mix solution by vortexing for 10 seconds and measure the fluorescence again. Log the reading as "standard after acidification (Ra)".
Calculate the ratio, r, as follows:
r=Rb/Ra=7.66/3.70=2.07
Measure chlorophyll-a and pheophytin-a of samples
Measure chlorophyll-a and pheophytin-a of samples
Use extraction of blank filter to zero the instrument on the sensitivity setting that will be used for sample analysis.
Or simply log the reading of blank filter extraction and subtract the reading from reading of sample extraction.
Transfer sample extract to disposable glass tube.
If the display reads OVER, dilute the sample and reread. Log dilution factor (DF) and reading (Rb).
Add 150 ul 0.1N HCl. Carefully mix solution by vortexing for 10 seconds and measure the fluorescence again. Log the reading (Ra).
Calculation
Calculation
Chlorophyll−a[ug/L]=r∗(Rb−Ra)∗DF/(r−1)
pheophytin−a[ug/L]=r∗(rRa−Rb)∗DF/(r−1)
Calibrate Turner
Calibrate Turner
Standards Room temperature
Primary Chlorophyll a standardsChlorophyll-a standardVWR InternationalCatalog # E-541-0-850
Come as a set of one low (15 ~ 20 ug/L) and one high (140 ~ 160 ug/L) concentration in foil wrapped ampules. Use low concentration for the calibration only.
Break the ampule with breaker and pour directly into the test tube
Blank: 90% buffered acetone Room temperature
Press <ENT> to reach Main Menu screen.
Press <2> to reach the Calibration Menu screen. Set the concentration range control to AUTO.
From screen 2.0, press <4> to bring up screen 2.4, then <3> to bring up screen 2.43 (set conc. range control), and press <ENT> to toggle.
Press <Esc> to screen 2.0, press <2> to access screen 2.2 (standard solution concentration). Enter the actual concentration of the primary liquid calibration standard (e.g. the value from the certificate).
Press <Esc> to return to screen 2.0.
Press <1> to access screen 2.1 and confirm that option #2 on screen 2.1 reads YES.
Press <Esc> to return to HOME screen.
While on the HOME screen, fill a clean 13-mm culture tube with 90% acetone (the blank). Put the tube in the sample chamber and replace the light cap.
Press <ENT> , <2>, <1>, and <1> to access 2.11 After the Blank % reading is stable (“TC” on screen 2.11 cycles from 1 to 8 seconds) and assuming the Blank % is less than 200%, press <0>.
When “FINISHED” appears, press <ESC> all the way to HOME.
Remove the blank. Set tube aside.
While on the HOME screen, place the tube with the LOW primary chlorophyll a standard in the sample chamber and replace the light cap.
Pressing <ENT>, <2>, and <3> to access 2.3
Using UP and DOWN arrows to adjust Span% until the FS reading is the closest to actual value of primary standard.
Wait until reading is stable (“TC” on screen cycles from 1 to 8 sec.), then press <*>.
When “FINISHED” appears, press <ESC> all the way to HOME screen.
Read the primary liquid standard on the home screen by pressing <*>, to confirm that the calibration was properly set and record the calibrant and reading on the calibration log sheet.
Place the solid secondary standard in the instrument, read the LOW value. Record the reading on the solid standard calibration record sheet as the reference of daily check.
Citations
Step 3.1
Shoaf WT, Lium BW. Improved extraction of chl and b from algae using dimethyl sulfoxide