Quality assurance in operating a multielement ICP emission spectrometer

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In the industrial laboratory environment, quality assurance in the operation of a multielement inductively coupled plasma emission spectrometer (ICPES) must often be entrusted to laboratory technicians with little or no technical background in spectrochemical analysis. Therefore, to be successful, a quality assurance program must be reduced to a simple, routine practice. Essential components of the quality assurance program described in this paper are (1) An atom-to-ion emission intensity ratio for multielement optimization and for reproducing optimum analysis conditions. (2) A concise, easily applied specification for sensitivity and for precision. (3) A regimen for monitoring of, and correcting for, calibration and background drift. (4) A set of comprehensive spectral interference calibrations maintained using the emission intensity ratio. (5) A high resolution spectrometer for minimizing spectral interferences. (6) A program of long term performance monitoring and maintenance/record keeping. Each of these components is described in detail. Adherence to this program enhances analytical reliability by helping to ensure that raw concentrations are generated consistently under optimum instrumental conditions, and that corrections for spectral interferences are applied accurately even though interference calibrations may be several months old. The importance of adequate resolution and the proper choice of positions for off-line background measurements is borne out by a detailed study of the determination of toxic trace elements in National Bureau of Standards fly ash samples. As, Be, Cd, Pb, Sb, and Se were determined accurately without isolation/preconcentration from the aluminosilicate matrix. Several determinations required corrections for residual spectral interferences amounting to 100–500% of the resultant concentration, underscoring the accuracy of the interference correction procedures.