Vapor Generation Accessory VGA–77 Operation manual

VGA–77Caution1. Disconnect the black fuoro-elastomer tubing from the cell inlet.2. Release the spring clips and remove the absorption cell from thecell support.3. Soak the absorption cell in dilute nitric acid for at least30 minutes.4. Rinse thoroughly with distilled water and allow it to air dry in adust-free location.5. If the cell has been exposed to contamination with potassiumiodide, soak the cell in sodium hydroxide solution (0.5% w/v) forat least 30 minutes. Wash thoroughly with dilute hydrochloricacid and then wash thoroughly with distilled water. Allow to airdry in a dust-free location.Do not leave the cell in the sodium hydroxide for too long becausethis solution may accelerate cell devitrification.Avoid handling the central part of the quartz cell with bare handsafter it has been cleaned or while it is in use.The working life of the cell will depend on the type of analyticalprograms carried out. At some stage, the quartz will start to turnwhite indicating the onset of devitrification. Initially, devitrificationwill not degrade the analytical performance, but eventually thedevitrified area will extend over most of the cell at which point it maybe necessary to discard the cell.If devitrification is excessive, the cell will eventually crackspontaneously or fail through thermal shock.Whether the cell becomes devitrified or not, and even with meticulouscleaning, the inside surface may deteriorate to the extent that theanalytical signal will be suppressed. You should regularly monitor theperformance of the cell using absorbance measurements obtainedfrom standard solutions. Discard the cell as soon as the results of thismonitoring become unacceptable.✒ Note When a significant number of samples are being analyzed, the use ofa drierite trap inserted between the absorption cell and the output ofthe gas/liquid separator will protect the absorption cell and extend itslifetime. (Refer to Varian AA-at-Work, 1986, October, No. 65.)5-2 Publication date: May 2004