EPA Method 6010, inductively coupled plasma atomic emission spectroscopy (ICP-AES), is undergoing interlaboratory evaluation for sludge-type wastes. The wastes included in the study are furnace ash, treatment sludge, mine waste, electroplating sludge, as well as contaminated soil and sediments. Twenty-three elements will be determined by conventional ICP-AES in digests of the spiked and unspiked waste materials.

The raw wastes as well as bulk digests will be analyzed by all participating laboratories so that the variation contributed by sample preparation can be distinguished from the variation contributed by the measurement process. Both sequential and simultaneous instruments will be used in the study to allow an assessment of performance as a function of instrument type. The study will include an analysis of variance to characterize the homogeneity of each waste material before distribution to the participating laboratories. Heterogeneous materials are not suitable for interlaboratory studies.

Method 6010, Version 1, includes quality control tests to assess the data quality. If the results for diluted samples or for spiked digest are not within the control limit of ±10% specified for this study, the method of standard additions is required to provide data of acceptable quality. For this interlaboratory study, a four-point method of standard additions is specified to allow a least-squares analysis to obtain the sample concentrations. Use of alternate wavelengths is recommended to confirm data quality when spectral overlap could be present.

While Method 6010, Version 1, will accurately reflect the element quantities solubilized by the digestion procedure used, it will not reflect the waste content of an element when components in the waste form insoluble compounds (such as barium and lead with sulfate). However, the quality control spike addition in Method 6010, Version 1, will indicate a data-quality problem for affected elements in such a situation so that data of known quality are obtained. Methods that are applied directly to solids (such as neutron activation analysis and X-ray fluorescence analysis) are called for to assess waste content (but not availability) when solubility limitations are present.