COMPARISON OF THE ANALYTICAL PERFORMANCE OF A
TEMPERATURE CONTROLLED HOT BLOCK, MICROWAVE AND
CONVENTIONAL OPEN VESSEL DIGESTION FOR MULTIELEMENT
ANALYSIS OF EFFLUENTS USING AXIALLY-VIEWED ICP-AES
Ruth Lerner, Assia Averbuch, Roni Chazan, Daniel Solomon and Isaac (Joe) Brenner1
Dan Region of Cities for the Environment and Effluents, 9 Congress Street, Tel-Aviv
Email: ruthi-l@egodan.org.il
1. Environmental Analytical Enterprises, 9 Dishon St., Malkha, Jerusalem, Israel, 96956
Email: Brenner@cc.huji.ac.il
Environmental monitoring of wastes for toxic trace metals involves routine decomposition and
subsequent multielement analysis for large sample batches. In the Dan Region laboratories, United
States Environmental Protection Agency (USEPA) Solid Waste (SW846) procedures are applied for
determination of acid extractable elements in industrial and domestic wastes. These procedures
specify various conventional and microwave-assisted acid decomposition routines to extract metals
with different efficiencies. One of the disadvantages of the open-dish procedure is the possibility of
contamination and inconsistent decomposition processes. In the case of microwave techniques the
cost of the apparatus is large, and in the case of reactive samples – limited sample size and hazard of
pressure release and as a consequence sample loss. Accordingly the use of a thermally controlled
inert hot block capable of decomposing tens of samples simultaneously at relatively low cost was
evaluated with emphasis on extraction efficiency.
Typical duplicate homogeneous liquid and semi-solid waste samples collected form the Dan region,
were treated by hot block, conventional open dish and microwave (MW) assisted techniques and
analyzed using a high-solids Sturman Masters conical spray chamber, a PEEK V-groove nebulizer
and a Varian Vista Pro (Varian, Melbourne, Australia) axially viewed charge coupled (CCD)
multielement simultaneous ICP spectrometer. A SCP Digiprep (SCP Science, Montreal, Quebec,
Canada) temperature-controlled inert hot block (105OC) was used. The microwave system was a
CEM MARS 5 (CEM Corporation Matthews NC, USA) USA) The complaint USEPA Solid Waste
(SW 846) 6010C and a total nitric acid total recoverable procedure akin to 3005a were used.
In all cases, analytical data were validated using EPA 6010C criteria and ISO 17025 guidelines e.g.,
IDLs, MDLs, LDR, ICV, CCV, spiked LCS, replicates, addition method, spectral interference
solutions, memory effects, CRMs etc to ensure that analytical performance is within the defined
figures of merit and that corrective actions are not required
Statistical tests indicated that there were no significant differences in concentrations of Ag, Al, Ba,
Cd, Cr, Cu, Mn, Mo, Ni, Pb, Sn and Zn using the specified dissolution techniques. Consequently, we
can conclude that the hot block procedure has advantages over conventional hotplate and MW
procedures. When using an MW, appropriate steps must be taken in all analyses to ensure that
potential interferences due to reactive organic matter are avoided. i.e., smaller volumes of sample
should be taken. In the case of the DigiPrep, large volumes of reactive samples can be taken and in
the case of low analyte concentrations and low-salt, samples can be concentrated by evaporation in
their disposable polypropylene vials without airborne contamination.