3.2 Instrument
Operation and
Quantification of
Nitrogen Content
1. Turn on furnace and bring all necessary delivered gases to their
desired flow rate, then wait until furnaces have stabilized at
their desired temperature (see Note 2).
2. Enter sample identifiers in the software console and include in
the sequence the reference standard, calibration check standard, and appropriate number of blanks (see Note 3).
3. Transfer samples to the autosampler tray and set up the
sequence run (see Note 2).
3.3 Data Analysis
1. Total nitrogen concentration of the biomass is determined via
calibration of the instrument (see Notes 5 and 6) and the
quality of the data is assessed via the rigorous quality control
charting established by the respective laboratories (see Note 7).
2. The nitrogen content is used to determine the crude protein
content using a nitrogen-to-protein conversion factor
(see Notes 8 and 9). In the absence of a custom species-specific
nitrogen-to-protein conversion factor, an average factor of
4.78 can be used for algal biomass:
Algae Crude protein, % w=w
ð
Þ¼%N Â 4:78
}
} this factor represents either an average factor from the literature [3] or alternatively, a custom calculated factor for respective algae species can be used [4].
4 Notes
1. All microalgal biomass samples must be freeze-dried or oven
dried (40
C vacuum oven) and fully homogenized before
analysis and final moisture content should be <10%. Care
should be taken to ensure a representative and ground/homogenized (ideally of a particle size <0.5 mm) sample is taken for
analysis. Storage of samples should be under an inert (nitrogen)
atmosphere and at least at À20
C.
2. The instrument used may differ between individual laboratories and available instrumentation. The methodology
described here is instrument agnostic and can be translated to
be used for any combustion nitrogen instrument available,
assuming the respective analytical controls and QC guidelines
are followed. Typical instrument settings for a LECO TruSpec
CHN Analyzer are as follows; use of an external PC, which uses
a Windows
®
-based software program; an autoloader; helium
carrier gas (99.99% pure) at 35psig; oxygen combustion gas
(99.99% pure) at 35psig; max oxygen flow of 6.3 L/min. In the
236
L. M. L. Laurens et al.
Operation and
Quantification of
Nitrogen Content
1. Turn on furnace and bring all necessary delivered gases to their
desired flow rate, then wait until furnaces have stabilized at
their desired temperature (see Note 2).
2. Enter sample identifiers in the software console and include in
the sequence the reference standard, calibration check standard, and appropriate number of blanks (see Note 3).
3. Transfer samples to the autosampler tray and set up the
sequence run (see Note 2).
3.3 Data Analysis
1. Total nitrogen concentration of the biomass is determined via
calibration of the instrument (see Notes 5 and 6) and the
quality of the data is assessed via the rigorous quality control
charting established by the respective laboratories (see Note 7).
2. The nitrogen content is used to determine the crude protein
content using a nitrogen-to-protein conversion factor
(see Notes 8 and 9). In the absence of a custom species-specific
nitrogen-to-protein conversion factor, an average factor of
4.78 can be used for algal biomass:
Algae Crude protein, % w=w
ð
Þ¼%N Â 4:78
}
} this factor represents either an average factor from the literature [3] or alternatively, a custom calculated factor for respective algae species can be used [4].
4 Notes
1. All microalgal biomass samples must be freeze-dried or oven
dried (40
C vacuum oven) and fully homogenized before
analysis and final moisture content should be <10%. Care
should be taken to ensure a representative and ground/homogenized (ideally of a particle size <0.5 mm) sample is taken for
analysis. Storage of samples should be under an inert (nitrogen)
atmosphere and at least at À20
C.
2. The instrument used may differ between individual laboratories and available instrumentation. The methodology
described here is instrument agnostic and can be translated to
be used for any combustion nitrogen instrument available,
assuming the respective analytical controls and QC guidelines
are followed. Typical instrument settings for a LECO TruSpec
CHN Analyzer are as follows; use of an external PC, which uses
a Windows
®
-based software program; an autoloader; helium
carrier gas (99.99% pure) at 35psig; oxygen combustion gas
(99.99% pure) at 35psig; max oxygen flow of 6.3 L/min. In the
236
L. M. L. Laurens et al.