An electronically controlled, high-voltage oscillatory spark source has been modified to deliver single oscillatory sparks, which may be terminated after one, two, three, four, or six complete current half cycles. This source can be tuned to give single half-cycle discharges of constant peak current and variable duration. Physical and chemical changes resulting from sampling a variety of alloys by sparks of varying numbers of half cycles have been studied by photomicrography and electron probe microanalysis. Physical effects of trains of sparks on polished electrode surfaces have been observed. The problem of preferential spark sampling of a volatile major element In an alloy has been quantitatively studied by electron probe microanalysis.The problems of physical and chemical changes which occur in a metal sample during a spectrochemical sparking procedure are important for several reasons:The composition of the sample surface may change with repeated sparking (1-3); the vapor composition may not represent the solid sample composition (1, 3-5);
The application of a magnetron glow discharge plasma, previously described, to the analysis of six zinc-base NIST Standard Reference Materials for a minor element, aluminum, and three trace elements, magnesium, nickel, and manganese, is described. The wide range of argon pressures, from 0.0007 to more than 2.5 Torr, over which the plasma can be operated, allows selection of optimum pressure for determination of each element. Line-to-background ratios are examined as functions of pressure for each element determined at discharge currents ranging from 100 to 400 mA. Sensitivities of net line intensities to discharge current show wide variations, depending on the element and line studied. Analytical curves for aluminum, magnesium, manganese, and nickel are shown. Detection limits for manganese and nickel are 0.0060% and 0.00055%, respectively.
Corroslon-reslstant Au thln fllms are routlnely produced for analysis of hlghly acldlc solutions by electrlcally vaporized thln fllm atomic emlsslon spectrometry. Dlrect determlnatlon of BI, Cd, Hg, Sb, Sn, and TI from 2 M HCI Is posslble, wlth detectlon llmlts ranglng from 0.085 to 6.5 mg/L, useful concentratlon ranges of about 2 decades, and relatlve errors of 4-5.7 % to -26 %. Slmple batch separatlon/preconcentratlon of Cd( I I ) wlth a mlcrobead strong base anion exchange resln allows determlnatlon of Cd In complex acldlc solutions near the 10 ng/mL (10 ppb) concentration level wlth relatlve errors of around 8 %. The method Is not expensive; materlals cost for a slngle cadmlum determlnatlon Is about $12, Including preparatlon of the analytlcal curve. Materials cost for preparation of the analytical curve plus flve cadmlum determinatlons Is about $20.00. The determination of traces of toxic heavy metals in very acidic or saline aqueous solutions has long been of interest (1-3). Seawater, other brines, acid mine waters, and plating bath liquors are among these solution types. Seawater, -0.5 M in NaCl, contains trace levels of a number of toxic heavy metals (I). The presence of high concentrations of group 1 and 2 salts can make determination of trace heavy metals difficult. Concomitant effects among trace metals have been reported in determinations by atomic absorption spectrometry with electrothermal atomization, a widely used method (4,5).Recent work (6-12) on electrically vaporized thin metal films as alternative vaporization and excitation sources for atomic emission spectrometry has shown their utility in analyses of refractory powder samples and ground solids such as coal, flour, dried spinach, and river sediments. In these investigations, using -350 pg Ag thin films, Goldberg and Sacks (12) found that aqueous solutions could be used as standards. They noted, however, that aqueous standards containing more than 500 ng of the element of interest were difficult to vaporize completely, because thick salt crusts formed when the solution droplets dried. Samples of more than 100 pg of particles suspended in 2-propanol were also not easy to vaporize. Goldberg and Sacks (12) also found that slightly acidic (-0.1 M HC1) aqueous solutions eroded Ag films badly.
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