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Appendix B
5/20/2009
1
Chesapeake Biological Laboratory
University of Maryland Center for Environmental Science
Nutrient Analytical Services Laboratory
Determination of Carbon and Nitrogen in Particulates and Sediments of
Fresh/Estuarine/Coastal Waters, Plant and Animal Tissue, and Soils Using
Elemental Analysis
1.
SCOPE and APPLICATION
1.1. Elemental analysis is used to determine particulate carbon (PC), and particulate
nitrogen (PN) in fresh, estuarine and coastal waters and sediments as well as for
plant and animal tissue and soils. The method measures the PC and PN irrespective
of source (organic or inorganic.)
1.2. A Method Detection Limit (MDL) of 0.0759 mg C/l and 0.0123 mg N/l, for filtered
samples, and 0.130 %C and 0.008% N for sediment samples, were determined using
three times the standard deviation of seven replicates.
1.3. The quantitation limit for PC and PN has not been determined.
1.4. This procedure should be used by analysts experienced in the theory and application
of elemental analysis. A minimum of 3 months experience with an elemental
analyzer is recommended.
1.5. This method is for use by all programs that require analysis of particulate carbon and
nitrogen in water and sediment, soils and tissues. The need to determine the organic
fraction of the total particulate carbon and nitrogen in samples depends on the data-
quality objectives of the study. Section 11.2.5 outlines the procedure used to
ascertain the organic fraction.
2.
SUMMARY
2.1.
In the Exeter Analytical, Inc. Model CE-440 Elemental Analyzer, the carbon and
nitrogen content in organic and inorganic compounds can be determined.
Combustion of the sample occurs in pure oxygen under static conditions. The
combustion train and analytical system are shown below in the CE-440 flow
diagram. Helium is used to carry the combustion products through the analytical
system to atmosphere, as well as for purging the instrument. Helium was selected
for this purpose because it is chemically inert relative to tube packing chemicals, and
it has a very high coefficient of thermal conductivity. The products of combustion
are passed over suitable reagents in the combustion tube to assure complete
oxidation and removal of undesirable by-products such as sulfur, phosphorus and
halogen gases. In the reduction tube, oxides of nitrogen are converted to molecular
nitrogen and residual oxygen is removed. In the mixing volume the sample gasses
are thoroughly homogenized at precise volume, temperature, and pressure. This
mixture is released through the sample volume into the thermal conductivity
detector. Between the first of three pairs of thermal conductivity cells an absorption
trap removes water from the sample gas. The differential signal read before and after
the trap reflects the water concentration and, therefore, the amount of hydrogen in