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Soil Analysis
We analyze all types of soils for nitrogen and carbon stable isotopes and total content. We can also analyze soil samples for total nitrogen (TN), total phosphorus (TP) and a variety of metals and offer a variety of digestion and extraction techniques.
Total Nitrogen and Total Carbon
Overview of technique
Micro-Dumas combustion analysis for total carbon and total nitrogen in solid-phase samples (plant tissue, soils, sediments, etc.) is based on transformation to gas phase by extremely rapid and complete flash combustion of the sample material. More details of the process are found below.
Sample prep considerations
Samples must be oven-dried, ball-milled to less than 250 um particle size and weighed (~3 mg, with ug digits significant) into 5 x 5 mm tin capsules before combustion. Poor precision can often be traced to inadequate grinding that leaves fibrous matter or visible granules in the sample. Sample prep for total-C/total-N analysis is found below. Clients may send us unprocessed samples (e.g. litterbag contents) or may provide any of the above processing themselves at a major reduction in price.
Nitrogen-15
Method Summary
Isotope-ratio analysis for 15N in solid-phase samples such as animal tissue starts with transformation to gas phase by extremely rapid and complete flash combustion of the sample material. Ionized combustion product (dinitrogen) is mass-analyzed by means of differing mass/charge ratios among the various isotopic species of N2. More details of the process are found here.
Sample prep considerations
Samples must be oven-dried, ball-milled to less than 250 um particle size and weighed (~3 mg, with ug digits significant) into 5 x 5 mm tin capsules before combustion. Poor precision can often be traced to inadequate grinding that leaves fibrous matter or visible granules in the sample. Sample prep for plant 15N analysis is found below. Clients may send us unprocessed samples (e.g. leaves, stems, roots) or may provide any of the above processing themselves at a major reduction in price.
Carbon-13
Overview of technique
Isotope-ratio analysis for carbon-13 in solid-phase samples such as plant tissue starts with transformation to gas phase by extremely rapid and complete flash combustion of the sample material. Ionized combustion product (carbon dioxide) is mass-analyzed by means of differing mass/charge ratios among the various isotopic species of CO2. A great many more details of the process are available here.
Sample prep considerations
Samples must be oven-dried, ball-milled to less than 250 um particle size and weighed (~3 mg, with ug digits significant) into 5 x 5 mm tin capsules before combustion. Poor precision can often be traced to inadequate grinding that leaves fibrous matter or visible granules in the sample. Sample preparation for 13C analysis is detailed here.
Clients may send us unprocessed samples (e.g. leaves, stems, roots) or may provide any of the above processing themselves at a major reduction in price.
Nitrate/ Ammonium
Overview of technique
This method describes the extraction of nitrogen as nitrate from soil by potassium chloride (KCl) extraction using Soil Science Society of America Methods of Soil Analysis section 33-3 and colorimetric analysis using APHA 4500-NO3 F.
Method Description
A 4-g aliquot of homogenized moist material is shaken for 1 hour with 20 mL of 2 molar KCl at room temperature in plastic centrifuge tubes. The tubes are centrifuged for 10 minutes at 3000 rpm and the supernatant is pipetted into scintillation vials. Nitrate (NO3-N) is then analyzed by continuous-flow colorimetry. Concentration is calculated by multiplying the colorimetrically-measured N-value by the volume of added KCl extract and divided by the wet weight of the sample. Nitrogen content per dry mass requires additional processing available for a fee upon request.
Reference
Keeney, D. R. and D. W. Nelson. 1987. Nitrogen–Inorganic Forms, sec. 33-3, extraction of exchangeable ammonium, nitrate, and nitrite. pp.648-9. In A. L. Page et al., eds., Methods of Soil Analysis: Part 2, Chemical and Microbiological Properties. Agronomy, A Series of Monographs, no.9 pt.2, Soil Science Society of America, Madison, Wisconsin USA.
Detailed soil extraction protocol can be found below.
Phosphate
More information coming soon.
Total Phosphorus
More information coming soon.