250 analyzer for nitrate/nitrite, Shimadzu TOC-V CPH with
ASI-V auto sampler, and TNM-1 Total Nitrogen detector for
TDN and Europa Scientific ANCA 20-20 Stable Isotope Analyser with a Roboprep-CN Biological Sample Converter
for PON.
2. Calibration curve is prepared by plotting measured absorbance
or area of standards versus standard concentrations (linear
regression).
3. Start each sample run with blank(s) and reference material to
verify proper operation of the instrument. Analyze samples in
sequences of max 20 samples followed by a blank and reference
material. Insert also standards in the sequence to test accuracy
and drift during the analytical runs.
4. Determine concentration in the sample by the slope of the
calibration curve. Reduce the absorbance of the blank/reference from the absorbance of the sample.
5. If concentration is >100 μg/l, prepare diluted sample.
6. These can be stored short term (2–3 weeks) in refrigerator or
alternatively in the freezer for 6 months.
7. Use ca. 5–10 different dilution steps for calibration depending
on the concentration span of the samples.
8. This is to prevent contamination of other samples in case of
bubbles forming during measurements.
9. In Shimadzu TOC-V CPH system, the sample is purged with
CO 2 free air to remove inorganic purgeable species, then an
aliquot is injected onto a combustion tube filled with platinumcoated alumina beads, and combustion products are measured
by the analyzer. Non-purgeable dissolved nitrogen compounds
are converted to NO, which is mixed with ozone chemiluminescence and detected by a photomultiplier.
10. Using a large filtration device (e.g., 50 mm Ø) you may place
several filters on top of each other and suck ultrapure water
through the filters.
11. There should be a clear color on the filter, but not forming a
“cake” of biomass.
12. This is to minimize the water content as much as possible.
13. Make sure to use lids not closing the Petri dish completely, or
alternatively use some aluminum foil, to let the filter dry
completely. The dried filter can be stored at room temperature
in a desiccator.
14. Note, marking the sample name with well plate name makes it
easy to follow the samples.
Determining Inorganic and Organic Nitrogen
79
ASI-V auto sampler, and TNM-1 Total Nitrogen detector for
TDN and Europa Scientific ANCA 20-20 Stable Isotope Analyser with a Roboprep-CN Biological Sample Converter
for PON.
2. Calibration curve is prepared by plotting measured absorbance
or area of standards versus standard concentrations (linear
regression).
3. Start each sample run with blank(s) and reference material to
verify proper operation of the instrument. Analyze samples in
sequences of max 20 samples followed by a blank and reference
material. Insert also standards in the sequence to test accuracy
and drift during the analytical runs.
4. Determine concentration in the sample by the slope of the
calibration curve. Reduce the absorbance of the blank/reference from the absorbance of the sample.
5. If concentration is >100 μg/l, prepare diluted sample.
6. These can be stored short term (2–3 weeks) in refrigerator or
alternatively in the freezer for 6 months.
7. Use ca. 5–10 different dilution steps for calibration depending
on the concentration span of the samples.
8. This is to prevent contamination of other samples in case of
bubbles forming during measurements.
9. In Shimadzu TOC-V CPH system, the sample is purged with
CO 2 free air to remove inorganic purgeable species, then an
aliquot is injected onto a combustion tube filled with platinumcoated alumina beads, and combustion products are measured
by the analyzer. Non-purgeable dissolved nitrogen compounds
are converted to NO, which is mixed with ozone chemiluminescence and detected by a photomultiplier.
10. Using a large filtration device (e.g., 50 mm Ø) you may place
several filters on top of each other and suck ultrapure water
through the filters.
11. There should be a clear color on the filter, but not forming a
“cake” of biomass.
12. This is to minimize the water content as much as possible.
13. Make sure to use lids not closing the Petri dish completely, or
alternatively use some aluminum foil, to let the filter dry
completely. The dried filter can be stored at room temperature
in a desiccator.
14. Note, marking the sample name with well plate name makes it
easy to follow the samples.
Determining Inorganic and Organic Nitrogen
79