Use of Inductively‐coupled Plasma Spectrometry for the Simultaneous Determination of Macro‐ and Micronutrients in NH4HCO3‐DTPA Extracts of Soils

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Abstract
Twenty‐six soils were extracted with 1M NH4HCO3‐. 0.005M DTPA solution (Soltanpour and Schwab, 1977). Inductively‐coupled plasma optical emission spectrometry (ICP‐OES) was used to simultaneously determine P, K, Zn, Fe, Cu, and Mn in the extracts. These analytical results were compared with those obtained with a colorimetric method for P and flame atomic absorption spectrometry (AAS) for the cations. It was necessary to change the carbonate‐bicarbonate matrix (1M) to a more soluble matrix in order to prevent formation of crystals and clogging at the capillary tip. This was achieved by a 1:5 dilution with 0.5N HNO3 followed by shaking for 10 min. Results from the ICP‐OES and the flame AAS methods were comparable. Analysis of P by ICP‐OES gave larger values than analysis by a colorimetric method due to presence of organic P in the extracts.