Abstract:
BACKGROUNDAfter the soil sample is extracted by organic acid, there are a lot of organic acids and organic matter in the solution. If these remaining materials are not destroyed, the central tube and rectangular tube of the atomizer are easily plugged after they have entered the inductively coupled plasma-optical emission spectrometry (ICP-OES) sampling system. Particles absorbed in the central tube wall and rectangular tube wall will result in poor analytical precision and accuracy, and further affect comprehensive evaluation of soil availability.
OBJECTIVESTo make the determination of available state in soil sample more stable and accurate, reduce the detection limit of the method, and prevent the sample from contamination and volatilization loss in the pretreatment.
METHODSSoil samples were extracted with organic acids (DTPA, oxalic acid-ammonium oxalate, citric acid, etc.), filtered or centrifuged, and the supernatant was absorbed into a high-pressure sealed digestion tank. The supernatant was treated by an electric heating plate and then added with 2mL concentrated nitric acid. The soil samples were heated for at least 3 hours in an oven at 180℃. The effective element contents of copper, zinc, iron, manganese, cadmium, lead, nickel, chromium, molybdenum and silicon were determined by ICP-OES.
RESULTSThe relative standard deviations in this method were 2.5%-9.8%, the relative errors were -2.1%-5.2%, the recoveries were 90.1%-103.2%, and the detection limits were 0.32μg/kg-0.038mg/kg. Using the method of burning in the high temperature furnace and the open digestion by nitric acid-perchloric acid (sulfuric acid), the recoveries were 89.2%-100.5%, and the detection limits were 0.50μg/kg-0.050mg/kg.
CONCLUSIONSThe method has stable measurement results, low blank and a short analysis period, and is especially suitable for continuous analysis of batch samples.
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