Assessment of Leco CNS-2000 analyzer for simultaneously measuring total carbon, nitrogen, and sulphur in soil

The effectiveness of Leco CNS-2000 automated dry combustion instrument to measure total carbon, nitrogen, and sulphur in soils was determined by comparison with measurements by standard single-element methods and with reference materials. Initial studies were made on the effect of a combustion catalyst (Leco COMCAT material) and of the degree of sample grinding. Increasing the amount of catalyst added increased the amount of carbon and nitrogen measured in a sediment reference material, but not the amount of sulphur. Although there was a very small but measurable quantity of nitrogen in the catalyst, the addition of 1 g catalyst to 0.2 g soil sample is recommended. Fine grinding (<100 mesh) resulted in small decreases in nitrogen and sulphur measured in soil samples, showing that coarse (<2 mm) grinding is actually preferred. The CNS-2000 instrument provided carbon and sulphur measurements that were equivalent to measurements by commonly used wet digestion (Walkley–Black and sodium hypobromite, respectively) methods for soils from a variety of sources in coastal British Columbia, and equivalent to certified values for reference materials. Both Leco CNS-2000 and FP-428 dry combustion instrument measurements of a variety of soil samples were slightly lower but proportional to Kjeldahl measurements of total nitrogen. It was concluded that the CNS-2000 instrument provided good to excellent total carbon and sulphur, and reasonably acceptable total nitrogen measurements of soils. Although the initial capital cost is a disadvantage, the CNS-2000 is capable of measuring total carbon, nitrogen and sulphur in soils quickly and simply. Acknowledgments Some of this work was conducted with funding from Program for Energy Research and Development (PERD) of Canadian Energy Mines and Resources. The technical assistance of D. Babuin and C. Van Laerhoven is much appreciated. Contribution number 630 of PARC.