Perkin-Elmer heated graphite

Figure 3.4. Perkin-Elmer heated graphite atomizer...

The sensitivity achieved should enable seawater samples to be analysed for molybdenum, because the concentration of molybdenum in seawater is usually 2.1 -18.8 pg/1. The selected temperature of 1700-1850 °C during the charring stage permits separation of the seawater matrix from the analyte prior to atomisation with the Perkin-Elmer Model 603 atomic absorption spectrometer equipped with a heated graphite atomiser (HGA-2100). 

A Perkin-Elmer 372 atomic absorption spectrometer with a HGA74 graphite furnace was used with temperature-controlled heating of the graphite tube . Good recoveries were obtained from the artificial seawaters, even at the 0.05/igl level, but for natural seawater samples the recoveries were lower (74-85%). This effect could be attributed to organic sample components that eluted from the column together with dimethyl arsinate. 

To overcome these problems, we have developed an empirical interference correction technique. The technique was studied for the four elements in sea water cadmium, copper, iron, and lead. A Perkin-Elmer 503 Atomic Absorption Spectrophotometer equipped with a heated graphite furnace (HGA2100) and a deuterium arc background corrector was used. The instrumental settings for each element are hsted in Table I. 

Fig. 8.1. Typical graphite furnaces (A) longitudinally heated model, (B) transversely heated model. For details, see text. (Reproduced with permission of Perkin-Elmer.)...

A Perkin Elmer model 503 atomic absorption spectrophotometer, equipped with Perkin Elmer HGA-2100 heated graphite atomizer (Figure 2), a deuterium arc background corrector (12), and a strip chart recorder, was used. The HGA-2100 graphite furnace was purged with argon. Hollow cathode lamps were used except for cadmium for which an electrodeless discharge lamp (Perkin Elmer) was used. 

After being dried, the samples were reexamined by nitrogen sorption and mercury intrusion, and a portion of the material was analyzed to determine the residual mercury levels. This analysis was achieved by acid digestion (10 mL of 50% aqua regia sample sizes were approximately 0.2 g in all cases) in pressure-sealed poly(tetrafluoroethylene) (PTFE) tubes heated to 140 °C for 10 min in a microwave oven (CEM). The solutions were analyzed after suitable dilution in distilled water with a graphite furnace atomic absorption spectrometer (Perkin Elmer 5100-PC). The detection limit for this method is estimated to be 6 ppm of mercury on the dry solid. 

Figure 49 Modem longitudinally heated graphite furnace (HGA-500, Perkin Elmer Corp.)...

Figure 20-5 (a) Electrically heated graphite furnace for atomic spectroscopy. Sample is injected through the port at the top. LVov platform inside the furnace is heated by radiation from the outer wall. Platform is attached to the wall by one small connection hidden from view. [Courtesy Perkin-Elmer Corp., Norwalk, CT.] (b) Heating profile comparing analyte evaporation from wall and from platform. 

FIG. 4. Schematic design of an electrothermal atomizer transversely heated graphite tube and graphite contacts (Courtesy of Perkin-Elmer). 

Table 12-3. Example of graphite furnace heating conditions for selected metal solutions in 0.1 mol/L HNO3 (Perkin-Elmer THGA furnace in conjunction with AA spectrometer 4100 ZL protection gas is argon, 99.998 % with internal flow rate of 250 mL/min).

The FID collector assembly was modified to connect, via Swage-lok fittings, to a small bore (0.027-inch i.d.), heated, programmable, stainless steel transfer tube, manufacured by Chemical Data Systems, Inc., Oxford, Pa. 19363. The GC injection ports, FID detector, and transfer tube were maintained at lOO C for all experiments conducted. The total column effluent from the GC was conducted through the transfer tube to the detector, a Perkin-Elmer model 360 atomic absorption spectrophotometer fitted with a deuterium background corrector and a HGA-2100 graphite furnace atomizer employing a temperature dial control power supply. 

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