PerkinElmer, Inc.

The determination of major and minor elements in air filters and urine for hazard assessment, using a new CCD DUAL-VIEWED ICP optical emission spectrometer

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This article describes the application of a new type of CCD-based, dualviewed ICP optical emission spectrometer for the analyses of industrial hygiene types of samples. Several trace elements in air filter media are determined by ICP-OES. Urinary electrolytes and trace elements are determined in a single dilution automatically in both the axial and radial plasma viewing orientations. Results of the analyses of certified reference materials are presented. Instrumental parameters and conditions are presented and discussed.

Many metal-based industries require the regular monitoring of their facilities to insure a safe and healthy working environment. OSHA has set exposure limits for many hazardous elements in workplace air (1). Often this task takes the form of air monitoring, whereby a known quantity of a building’s internal air is drawn through a membrane filter. The filter traps the metal-containing dust particles. The filter membrane and its contents are then digested or leached into a known volume of solution. Inductively coupled plasma optical emission spectrometry (ICP-OES) provides accurate and rapid quantitative elemental analyses of the solution, so that the amount of airborne metal (mg/m3) in the facility’s air can be determined (2-3).

Additionally, it may be desirable to periodically screen employees for evidence of exposure to toxicologically significant levels of hazardous elements. Measuring urinary levels of these elements by ICP-OES is a rapid and convenient means to assessing workers’ exposures. Historically, atomic absorption spectroscopy (flame and electrothermal atomization) has been the technique of choice for most analysts. High concentrations of the electrolytes, sodium, potassium, calcium, and magnesium have been measured in urine for many years by flame AAS (4-5), and more recently ICP-OES has been used to provide multielement determinations of these elements (6- 7). Very low concentrations of many trace elements in urine have been reported in the literature using electrothermal AAS (8-10), but very few trace elements provide sufficient signal for traditional photomultiplier tube-based ICP spectrometers using radial plasma viewing without a preconcentration step (11-12).

Since its introduction 30 years ago, ICP-OES has found wide application in many fields by providing efficient multielemental spectrochemical analysis. However, when compared with electrothermal atomic absorption, traditional or radially viewed ICPs have had the disadvantage of lower sensitivity. This is especially important in the application of ICP-OES to the determination of trace elements in urine, because many of the elements are toxicologically important at very low concentrations (mg/L). More recently, axially-viewed ICP-OES has extended the measurable concentration range into the sub-ppb area for many elements (13-14). Axial observation samples a larger volume of the plasma emission, potentially yielding improved detection limits by up to a factor of 10.

Solid-state charge-coupled device (CCD) detectors have been applied to the measurement of ICP spectra recently with great advantages (15- 16). The array detectors give the analyst the most flexibility in choice of analytical wavelengths and background correction points. These CCD detectors simultaneously measure the analytical line and the spectral background, thereby reducing background flicker noise and improving the measurement’s signalto- noise ratio.

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