G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
G01N1/00—Sampling; Preparing specimens for investigation
G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
G01N1/40—Concentrating samples
G01N1/405—Concentrating samples by adsorption or absorption
G—PHYSICS
G01—MEASURING; TESTING
G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
G01N31/002—Determining nitrogen by transformation into ammonia, e.g. KJELDAHL method