Collaborative study of the elemental analysis of plant tissue by direct reading emission spectroscopy

Eleven laboratories collaboratively studied the use of direct reading emission spectroscopy, with the solution rotating disk technique of excitation for the elemental analysis of plant tissues; aluminum, barium, boron, calcium, copper, iron, magnesium, manganese, molybdenum, phosphorus, potassium, sodium, strontium, and zinc in alfalfa, citrus leaves, orchard leaves, pine needles, and tomato leaves. Since not all direct reading emission spectrographs are alike in all features, provisions were made to accommodate these differences relating to sample preparation, selection of the internal standard, and method of sample excitation. The sample is dry ashed and the ash is dissolved in an acidic buffer solution. Coefficients of variation obtained in the collaborative study ranged from 3 to 50 percent. For most plant tissue samples and elements, the value is less than 20 percent. The results obtained with direct readers are generally better than those obtained on photographic instruments and comparable to those obtained by atomic absorption spectroscopy. Direct reading emission spectroscopy is rapid, providing 14 elemental analyses in generally less than 1 min for a prepared sample. The method has been adopted as official first action. (U.S.)