In algae i care about cyanobacteria
Perhaps "Standard procedure for the determination of chlorophyll a by spectroscopic methods" can be of use? Available as PDF.
Chlorophyll-a Equation (Jeffrey & Humphrey, 1975):
The chlorophyll-a concentration (chl-a) can be estimated using the following equation:
chl-a (µg/L) = 11.54 × A665 - 2.27 × A750
In this equation, A665 and A750 are the absorbance values measured at wavelengths of 665 nm and 750 nm, respectively.
Carotenoid Equation (Ritchie, 2008):
The carotenoid concentration can be estimated using the following equation:
Carotenoid (µg/L) = 1000 × [ (A470 - 0.014 × chl-a) / (78.8 - 3.88 × chl-a) ]
In this equation, A470 is the absorbance value measured at a wavelength of 470 nm, and chl-a is the chlorophyll-a concentration obtained from the previous equation.
DOSAGE DE CHLOROPHYLE PAR SPECTROPHOTOMETRE
1) Filtration
L’eau doit être filtrée le plus rapidement possible après le prélèvement par WHATMAN GF/C
(porosité : 1,2μm).
Placer une membrane sur le support ;
Appliquer le vide et filtrer l’Ech. en prenant soin de l’agiter ;
Laisser fluer l’air quelques instants ;
Mettre le filtre dans le tube prévu à cet usage et si possible commencer l’extraction ;
Placer aussitôt le filtre à l’abri de la lumière dans une feuille d’aluminium.
2) Extraction des pigments
Introduire le filtre dans un tube à centrifuger et ajouter 10 ml d’acétone à 90% ;
Déchiqueter le filtre à l’aide d’une baguette, boucher et ajouter ;
Laisser l’extraction se poursuivre, 20h au réfrigérateur dans l’acétone à 90% ;
Laisser revenir à température ambiante ;
Centrifuger 1min, retirer les tubes et agiter légèrement ;
Centrifuger à nouveau 5 à 10 min à 3000-4000 tr.min-1 ; les tubes doivent rester bouchés.
3) Mesures d’absorbance selon la méthode de Lorenzen
Transférer le surnageant dans la cuve à l’aide d’une seringue de verre ;
Mesurer les absorbances brutes des extrais non acidifiés (𝐴𝑏665
𝑛𝑎 et 𝐴𝑏750
𝑛𝑎 ) (𝐴𝑏750
𝑛𝑎 < 0,005) ;
Acidifier par l’addition d’une goutte d’ac. chlorhydrique (0,3 mol.l-1), attendre 2 à 3 min et
mesurer les absorbances (𝐴𝑏665
𝑎 et 𝐴𝑏750
𝑎 ).
Le blanc de cuve : remplir les deux cuves avec l’acétone 90% ; mesurer les absorbances
(bc750 , bc665) ;
Mesurer le blanc de turbidité sur chaque Ech. à λ=750 nm ; (Ab750 - bc750).
4) Calcules, Expression des résultats
Avant l’acidification : 𝐴665
𝑛𝑎 = (𝐴𝑏665
𝑛𝑎 – bc665) – (𝐴𝑏750
𝑛𝑎 – bc750).
Après l’acidification : 𝐴665
𝑎 = (𝐴𝑏665
𝑎 – bc665) – (𝐴𝑏750
𝑎 – bc750).
Les concentrations de chlorophylle a et de phéopigments a :
[Chlorophylle a] (mg.m-3) =
26,7(𝐴665
𝑛𝑎 −𝐴665
𝑛𝑎 )∗𝑣
𝑉∗𝑙
[Phéopigments a] (mg.m-3) = 26,7(1,7𝐴665
𝑉 ∗𝑙
V : volume d’eau filtrée (litres)
v : volume de solvant d’extraction (millilitres)
l : longueur du trajet optique de la cuve de mesure (centimètre)
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