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

Abstract

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.