nitrogen-to-protein factor is determined, a rapid, total nitrogen
determination can be carried out on a routine basis. The use of a
dedicated nitrogen conversion factor then relates the nitrogen
content back to a calculated total protein content.
2 Materials
2.1 Sample
Preparation
1. Analytical balance, accurate to 1 mg or 0.1 mg.
2. Drying oven (40
C vacuum) or lyophilizer (see Note 1).
3. Tin foil cups [e.g., Cat. No. 502-186-100 (small), or 502-397
(large), LECO].
2.2 Combustion
Nitrogen Apparatus
(See Note 2)
1. Furnace to maintain minimum operating temperature of
950
C for combustion of sample in pure (99.99%) oxygen.
2. An isolation system is typically in place to isolate nitrogen gas
from other combustion products for subsequent measurement
by a thermal conductivity detector (TCD). A device for converting NO x products to N 2 or measuring N as NO 2 may be
required and included in the system. In the case of the LECO
TruSpec CHN Analyzer, the flow is passed through hot copper
to remove residual oxygen and convert NO x to N 2 . Then, CO 2
and H 2 O are removed via absorption using various sorbents
(e.g., Lecosorb, Cat. No. 502-174-HAZ; Anhydrone, Cat.
No. 501-171-HAZ, LECO), before the N 2 is analyzed via
the TCD.
2.3 Reagents and
Standards
Ethylene diamine tetraacetic acid (EDTA) is typically used as a
reference standard to interpret the detector response as % nitrogen.
The theoretical N concentration for EDTA is 9.586%.
3 Methods
3.1 Sample
Preparation for
Combustion Nitrogen
Analysis
1. Record the weight of all labeled vials to the nearest 0.1 mg.
2. Weigh 50–100 mg (record exact weight to the nearest 0.1 mg)
of freeze-dried and finely homogenized algal biomass into
tared sample containers (see Note 1). Record the weight of
the sample to the nearest 0.1 mg.
3. Dry samples in vials overnight to obtain an oven dry weight
before proceeding with the analysis to obtain a dry matter
(DM) number to express the nitrogen concentration, alternatively after collecting a sample in the respective containers
(see Note 4).
Protein Content Determination in Microalgae
235
determination can be carried out on a routine basis. The use of a
dedicated nitrogen conversion factor then relates the nitrogen
content back to a calculated total protein content.
2 Materials
2.1 Sample
Preparation
1. Analytical balance, accurate to 1 mg or 0.1 mg.
2. Drying oven (40
C vacuum) or lyophilizer (see Note 1).
3. Tin foil cups [e.g., Cat. No. 502-186-100 (small), or 502-397
(large), LECO].
2.2 Combustion
Nitrogen Apparatus
(See Note 2)
1. Furnace to maintain minimum operating temperature of
950
C for combustion of sample in pure (99.99%) oxygen.
2. An isolation system is typically in place to isolate nitrogen gas
from other combustion products for subsequent measurement
by a thermal conductivity detector (TCD). A device for converting NO x products to N 2 or measuring N as NO 2 may be
required and included in the system. In the case of the LECO
TruSpec CHN Analyzer, the flow is passed through hot copper
to remove residual oxygen and convert NO x to N 2 . Then, CO 2
and H 2 O are removed via absorption using various sorbents
(e.g., Lecosorb, Cat. No. 502-174-HAZ; Anhydrone, Cat.
No. 501-171-HAZ, LECO), before the N 2 is analyzed via
the TCD.
2.3 Reagents and
Standards
Ethylene diamine tetraacetic acid (EDTA) is typically used as a
reference standard to interpret the detector response as % nitrogen.
The theoretical N concentration for EDTA is 9.586%.
3 Methods
3.1 Sample
Preparation for
Combustion Nitrogen
Analysis
1. Record the weight of all labeled vials to the nearest 0.1 mg.
2. Weigh 50–100 mg (record exact weight to the nearest 0.1 mg)
of freeze-dried and finely homogenized algal biomass into
tared sample containers (see Note 1). Record the weight of
the sample to the nearest 0.1 mg.
3. Dry samples in vials overnight to obtain an oven dry weight
before proceeding with the analysis to obtain a dry matter
(DM) number to express the nitrogen concentration, alternatively after collecting a sample in the respective containers
(see Note 4).
Protein Content Determination in Microalgae
235