Argon flows

This chapter should be read in conjunction with Chapter 6, Coronas, Plasmas, and Arcs. A plasma is defined as a gaseous phase containing neutral molecules, ions, and electrons. The numbers of ions and electrons are usually almost equal. In a plasma torch, the plasma is normally formed in a monatomic gas such as argon flowing between two concentric quartz tubes (Figure 14.1). 

In operation, a spark source is normally first flushed with argon to remove loose particulate matter from any previous analysis. The argon flow is then reduced, and the cathode is preheated or conditioned with a short bum time (about 20 sec). The argon flow is then reduced once more, and the source is ran for sufficient time to build a signal from the sample. The spark is then stopped, and the process is repeated as many times as necessary to obtain a consistent series of analyses. The arc source operates continuously, and sample signal can be taken over long periods of time. 

This arrangement provides a thin film of liquid sample solution flowing down to a narrow orifice (0.007-cm diameter) through which argon flows at high linear velocity (volume flow is about 0.5-1 1/min). A fine aerosol is produced. This particular nebulizer is efficient for solutions having a high concentration of analyte constituents. 

Having removed the larger droplets, it may remain only to encourage natural evaporation of solvent from the remaining small droplets by use of a desolvation chamber. In this chamber, the droplets are heated to temperatures up to about 150 C, often through use of infrared heaters. The extra heat causes rapid desolvation of the droplets, which frequently dry out completely to leave the analyte as small particles that are swept by the argon flow into the flame. 

Cupric phthalocyanine [147-14-8] M 576.1. Precipitated twice from cone H2SO4 by slow dilution with water. Also purified by two or three sublimations at 580° in an argon flow at 300-400Pa. 

The most widely used nebuliser system in ICP is the crossed-flow nebuliser shown in Fig. 20.12. The sample is forced into the mixing chamber at a flow rate of 1 mL min 1 by the peristaltic pump and nebulised by the stream of argon flowing at about 1 Lmin-1. 

Reagent setting Argon cylinder pressure Argon flow rate... 

A convenient synthesis of InjS4 from In and S uses molten Sn as solvent. Other In-S phases, InS (red crystals) and In(,S7 (black), are obtained from the melt when InjSj is reduced with In in a sealed tube. To prepare In Se, the Iu2Se3 phase is heated to 1000°C in an argon flow, resulting in the loss of Se as the more volatile component. ... 

Charrette and Lebel [24] developed a catalytic enantioselective cyclopropa-nation of trans-cinnamate esters with diazomethane. Their procedure involves an argon-flow-mediated diazomethane addition, leading to high yields (up to 80%) in products with up to 80% ee, by using the bis(oxazoHne) arising from phenylglycinol (Scheme 10). 

CuOTf.PhCHa (5 mol %) CH2N2 / CH2CI2 (argon flow) CH2CI2 -40°C... 

TPR Experiments. They were performed with O.lOOg of catalyst with an OkuraTP-2002 S instniment, with a heating rate of 8°C/min, using as reducing gas a 4.8% in argon flow. All samples... 

Raw materials were ground to a particle size less than 630 pm. Physical mixtures of solid KOH and a given precursor at 2 1, 3 1, 4 1 and 5 1 weight ratios were activated in the temperature range of 600-900°C for 1-5 h under argon flow of 15 dm3/h. The treatments were carried out in a horizontal furnace using a nickel boat placed in a 36 mm diameter quartz tube. The heating rate was 10°C/min. The resultant materials were washed with 10% solution of HC1 and distilled water and next were dried at 110°C for 6 h. 

The thermally expanded graphite was used without any preliminary treatment the carbon was synthesized by carbonation of the raw material in an argon flow at 500°C with subsequent thermal treatment. Carbon residues strongly differing in the crystallinity degree were obtained as depends on the temperature which ranged from 500°C to 1300°C. The identity of each material was checked by X-ray spectroscopy. 

Argon flow rates Coolant 11 L/min, plasma 1.2 L/min, carrier 1 L/min, light path purge 1.5 L/min... 

Bishop [75] determined barium in seawater by direct injection Zeeman-modulated graphite furnace atomic absorption spectrometry. The V203/Si modifier added to undiluted seawater samples promotes injection, sample drying, graphite tube life, and the elimination of most seawater components in a slow char at 1150-1200 °C. Atomisation is at 2600 °C. Detection is at 553.6 nm and calibration is by peak area. Sensitivity is 0.8 absorbance s/ng (Mo = 5.6 pg 0.0044 absorbance s) at an internal argon flow of 60 ml/min. The detection limit is 2.5 pg barium in a 25 ml sample or 0.5 pg using a 135 ml sample. Precision is 1.2% and accuracy is 23% for natural seawater (5.6-28 xg/l). The method works well in organic-rich seawater matrices and sediment porewaters. 

Rhodobacter capsulatus B10 Chemostat wih ammonium limitation, lactate, continuous argon flow (100 ml/min), light saturation 88 0.115 97 Tsygankov et al., 1998... 

Figure 2.4 Schematic diagram of an ICP torch. The sample is carried into the torch by the carrier argon gas, and is ignited by radio-frequency heating from the RF coils. The tangential argon flow lifts the flame from the burner, preventing melting. The position of the detector in axial or radial mode is shown. (From Pollard et al., 2007 Fig. 3-3, by permission of Cambridge University Press.)...

In this manner an argon flow could be used to strip the generated hydride from solution and carry it out of the top of the cell where it was directed, via a 1mm i.d. xl.5mm o.d. quartz tube, into the sample introduction port of a... 

Fig. Z12 DSC curve of a commercial, as-received and nonactivated Tego Magnan powder obtained under argon flow and a heating rate 4°C/min...

Fig. 2.48 DSC traces of Tego Magnan MgH powder doped with m- and n-Ni, and (a) mixed for 1 h without milling (no steel balls) and (b) mixed for 1 h with Tego Magnan MgH which was premilled for 20 h (heating rate 4°C/min argon flow rate 25 ml/min)...

Fig. 2.57 DSC traces of ABCR MgH + 5 wt.% n-Ni after milting for 15 min. (a) spherical and (b) filamentary morphology (heating rate 10°C/min argon flow rate 50 ml/min). The range of onset temperatures of n-Ni containing mixtures is circled in red...

Fig. 3.4 DSC traces of 2Mg-Fe mixtures milled sequentially for 210 and 270 h and continuously for 270 h (heating rate of 4°C/min and argon flow rate of 16 ml/min)...

Fig. 3.7 DSC trace of as-received, undoped NaAlH (purity 90%) and (b) the same hydride after milling for 5 h in the magneto miU Uni-Ball-Mill 5 under HES57 mode (two magnets at 5 and 7 o clock positions). Heating rate 10°C/min at argon flow 50 ml/min...

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