Solid samples are analyzed on a LECO Tru-Spec CN analyzer (Leco Corp., St. Joseph, MI, USA). The instrument is primarily used to analyze total C and N concentrations in soil and vegetation samples although it has also been used for fertilizer, animal feeds, animal tissue, plant litter, fecal matter, and wastewater effluents.
Organic C concentrations can be determined on samples following acid digestion, or can be calculated by difference following off-line inorganic C analysis. Both analyses can be performed at the facility.
The instrument is a dry combustion type with infrared detection for carbon and thermal conductivity detection for nitrogen. It is computer driven with an interfaced balance and a 30 position auto-sampler, which allows up to 2 hours of unattended operation.
|Sample size (upper and lower limits)||soils||0.2-0.5 g|
|Detection limit||100 ppm (at 0.5g sample)|
|Observed precision (CV%)1
|Analysis time||4 min/sample|
1Typical precision is a coefficient of variation of about 2.5% at nominal sample size (assuming %C = 2.5 and %N= 0.25 for soils, %C = 42 and %N = 2.5 for plants). Lower concentrations will have lower precision.
The facility recently purchased a Shimadzu TOC-L for total, organic and inorganic C, and total N in aqueous samples. The system is currently being installed and tested, but we expect full operation in the coming weeks.
The combustion type TOC eliminates salt interferences and ensures complete oxidation even with high molecular weight compounds, suspended particles, and refractory compounds. The system incorporates a Non-Dispersive Infrared (NDIR) detector for maximum sensitivity and durability. The measuring range is from 4 ppb to 30,000 ppm.
The Total Nitrogen Module permits carbon and nitrogen analysis simultaneously. The TNM-L utilizes a chemiluminescence detector to measure Total Nitrogen (TN) in the range of 5 ppb to 10,000 ppm.
It is computer driven with a 68 position autosampler for 40-mL vials.
The instrument can be configured to measure:
- Total carbon
- Total organic carbon
- Non-purgeable organic carbon
- Total inorganic carbon
- Total nitrogen
- Total carbon/total nitrogen
- Total organic carbon/total nitrogen
- Dissolved organic carbon and dissolved nitrogen may be measured by filtering the samples first.
- Organic nitrogen can be determined by measuring the total nitrogen on this instrument and the inorganic nitrogen on the Alpkem.
The instrument will be used to analyze C and N concentrations in lake water, stream water, and soil microbial biomass extracts.