Experimental

Instrumentation

The basic design of the ICC and the L’vov platform are shown in Figs. 1 and 2. The entire ICC was manufactured from one single piece of graphite of RW0 quality (Ringsdorff-Werke GmbH, Bonn, Germany), with tube dimensions of 17 mm length and 5mm square section, and incorporated into a home-made furnace (Fig. 1). This furnace can also accomodate a separately-heated graphite cup situated under the tube [4, 7].

Fig. 1 Atomizer for ICC: (1) integrated contact cuvette interchangeable with tungsten tube; (2) contact area clamped in terminal block; (3) silicone rubber gasket; (4) connection for cooling water supply; (5) connection for upper gas flow supply; (6) connection for lower gas flow supply; (7) light beam aperture; (8) lower gas flow block and fibre - optic cable mount; (9) fibre - optic cable inlets; (10) base plate with electrical insulation; (A,B) end blocks; (C,D) tube terminal blocks. B and D are mounted on ball bearings to permit horizontal play. The furnace housing is covered by a quartz window. Fig. 2 The L'vov platform used for the integrated contact cuvette. Dimensions in mm.

For installing the tungsten furnace, two pairs of metal adaptor pieces were inserted into the terminal blocks (D). The dimensions of the tungsten furnace and platform used here have been described elsewhere [9, 10] and were obtained from Plansee Werke (Reutte, Austria). The furnace was installed in a Varian Techtron AA-6 atomic absorption spectrometer (Solna, Sweden), provided with a hydrogen lamp for background correction. Transformers capable of delivering 7.5 kW were connected to the furnace.

The signal damping of the AA-6 readout module was modified to obtain a faster response time from the electronics. The value of the DAMP A time constant was thus altered from the original 260 ms to 10 ms, as described earlier [11]. In order to study in detail the time dependence of the analytical signals as well as the temperature, a fast on-line data acquisition system was connected to the spectrometer [12]. This system was also used to calculate the peak height and peak area values.

For comparative experiments either a Perkin-Elmer 3030 atomic absorption spectrometer equipped with an HGA-500 (Überlingen, Germany) or a Varian Techtron SpectrAA-30 equipped with a GTA-96 were used. The instrumental parameters are summarized in Table I. Both systems had autosamplers and printers. For the emission measurements a Spectrametrics SMI-III echelle monochromator (Spectraspan, Andover, MA, USA) incorporating an oscillating quartz plate for background correction was used [13].

Table I a Instrumental parameters for the Perkin-Elmer 3030 - HGA-500 and ICC - Varian AA-6. Platform atomization for analyte in aqueous 0.1 % Cu(NO3)2 and 0.1 % CuCl2 solutions. Recommended spectral bandpasses and lamp currents used. Drying temperature 170 oC, ramp 15 s, hold 20 s. No ashing was used. 20 ul sample volume.
AnalyteWavelength/nm Atomizea/oC
0.1 ng Ag328.11600
1.0 ng Al309.32400
0.2 ng Mn279.52200
0.4 ng Pb283.32000
1.0 ng Sn286.42100
a Maximum heating rate, 5 s hold time, gas stop

Table I b Instrumental parameters for the Varian SpectrAA-30 - GTA-96 and ICC - Varian AA-6. Wall atomization for analyte in aqueous and 5 % HNO3 solutions. Recommended spectral bandpasses and lamp currents used. 20 ul sample volume.
AnalyteWavelength/nm Ash/oC Atomizea/oC
1.0 ng Au242.8700 2400
0.1 ng Cd228.8300 1800
1.0 ng Mo313.31000 2650
1.0 ng Pb283.3400 2000
4.0 ng V318.51000 2650
Normal injection:Dry 100 oC, 10 s ramp, 10 s hold
Dry 120 oC, 10 s ramp, 5 s hold
Ash, 10 s ramp, 12 s hold. Gas stop after 20 s
Hot injectionb:Temperature 130 oC, inject rate 4 (about 20 s)
Ash, 0.5 s ramp, 12 s hold. Gas stop after 10.5 s
a Maximum heating rate, 5 s hold time, gas stop
b Only used with the Varian SpectrAA-30 - GTA-96 system

Reagents and Materials

All solutions were prepared from SR-grade or higher purity. Only pyrolytically coated tubes were used (Ringsdorff-Werke GmbH). Platforms were manufactured from pyrolytic graphite (Ringsdorff-Werke GmbH). Argon of SR grade was used throughout.


Previous page
Next page
Return to the Conference Presentations page, or the Atomic Spectrometry Group home page