Analytes Certified for in 2022
Initially, milled air-dry soil is extracted for 1 h with 2M KCl at a 1:10 soil/solution ratio. For 7C1a to 7C1h methods, mineral-N components are quantified by steam distillations and subsequent titrations. For 7C2 methods, mineral-N fractions in the clarified soil extract are determined by automated colorimetric procedures. Ammonium ions (NH4+) are measured by a modified Berthelot indophenol reaction, while the Griess-Ilosvay reaction is used for NO3-N (and NO2-N). The methods specify reporting results for NH4-N and NO3-N [plus NO2-N if present], respectively, as mg N/kg on an oven-dry (105oC) basis. Specifically, method 7C2a relates to an automated colour, continuous segmented flow analytical finish, while Method 7C2b codes an automated colour finish by flow injection analysis. Little difference is expected in results due to choice of colorimetric finish.
Analysis of Mehlich 3 extract using inductively-coupled atomic emission spectroscopy (ICP-AES)
Microwave Digestion - closed system without HF, and final medium HNO3 and/or HCl. ICP-AES finish.
Microwave Digestion - closed system without HF, and final medium HNO3 and/or HCl. ICP-MS finish.
Finely divided dry sample. Dumas combustion.
Extraction with acid(s). Titrimetric finish.
Extraction with acid(s). Spectrophotmetry (automated) finish.