Microwave emission standards

Unintentional radiators include industrial applications, such as RF sealers and welders, and microwave ovens. Many such devices have emission standards, promulgated by the FCC, the Food and Drug Administration (FDA), or some other agency, limiting radiation from the device generally to avoid electromagnetic interference (EMI). NIER exposure standards apply to unintentional radiators, as well. 

The nature of potential exposure ha2ards of low level microwave energy continues to be investigated (116—118). In the United States, leakage emission from microwave ovens is regulated to the stringent limit of 5 mW/cm at 5 cm (119). There is no federal limit on emission from industrial systems but the IMPI has set a voluntary standard which specifies 10 mW/cm at 5 cm (120). Emission values are equivalent to personnel exposures at several meters, well below limits that had previously prevailed in eastern Europe. This conclusion, derived for microwave ovens, should be vaUd for all microwave systems (121). 

HPLC-QFAAS is also problematical. Most development of atomic plasma emission in HPLC detection has been with the ICP and to some extent the DCP, in contrast with the dominance of the microwave-induced plasmas as element-selective GC detectors. An integrated GC-MIP system has been introduced commercially. Significant polymer/additive analysis applications are not abundant for GC and SFC hyphenations. Wider adoption of plasma spectral chromatographic detection for trace analysis and elemental speciation will depend on the introduction of standardised commercial instrumentation to permit interlaboratory comparison of data and the development of standard methods of analysis which can be widely used. 

The particulate material from the sediment traps was digested in aqua regia in a microwave digestion unit. Fe, Mn, Zn, Ca, Cr, and Cu were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) P was determined by the molybdate spectrophotometric method (28). A sediment standard (NBS No. 1645) was used regularly to check the accuracy of the sediment digestion procedure. 

Microwave-induoed plasma atomic emission speotrometry is a useful analytioal technique for the determination of alkali and alkaline earth metals (e.g. that of sodium in water-soluble organio pharmaceuticals [42] with detection limits of 0.91-3.0 ng/ml). Also, it allows samples with organio contents up to 5% to be inserted without a desolvation system. Beryllium in spiked water samples was determined in this way with detection limits at the level of parts per trillion (ppt) and a preoision of 1.8% as relative standard deviation (RSD) [43]. 

Because of its low specificity and sensitivity flame ionisation detection (FID) can only be used in the analysis of standard substances [37]. The same limited application is envisaged for the method with the microwave-induced plasma emission detector, which is not sensitive enough for environmental samples [2]. 

It can be said that microwaves constitute the standard treatment method for the analysis of ultratraces together with technical detection such as inductively coupled plasma-atomic emission spectrometry and inductively coupled plasma-mass spectrometry. 

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