Devices for Addition of Releasing Agents, etc

Generally in analytical flame spectrometry, the pneumatic nebulizer functions as a sample pump, as well as to produce aerosol. Most nebulizers pump sample solution at a rate somewhere between 4 and 8 ml min-1. If the nebulizer is connected, via a suitable capillary T piece, to two pieces of aspiration capillary rather than just one, one capillary may be used to aspirate sample and the other a releasing agent, ionization buffer, or even simply a diluent.20,21 Turbulent mixing occurs at the T  

Care is needed to make sure that the relative flow rates in the two arms of the T are as desired. Equal flow rates will be obtained only if both uptake tubes are 

Cresser, Solvent Extraction in Flame Spectroscopic Analysis , Butterworths, London, 1978. 

A more expensive alternative is to use standard AutoAnalyser type systems, based on multichannel peristaltic pumps, to pump samples and reagents and/or diluents at the desired rates to give automatic mixing at the desired ratio. Flame photometric detectors have been used for many years with AutoAnalysers, especially in clinical laboratories. Curiously, in the past, this approach has less often been routinely used in environmental analytical laboratories employing flame spectrometry, perhaps because an attractive feature of flame spectrometry is the speed of response when used conventionally. Over the past few years, however, there has been an increasing tendency towards fully automated, unattended operation of flame spectrometers. This undoubtedly reflects, at least in part, the improvements in safety features in modern instruments, which often incorporate a comprehensive selection of fail-safe devices. It also reflects the impact of microprocessor control systems, which have greatly facilitated automation of periodic recalibration. 

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