Vapor Generation Accessory VGA–77 Operation manual

VGA–77Always stabilize the solution by first adding sodium hydroxide(NaOH—0.5% w/v). Since sodium borohydride will decomposesignificantly in one or two days, you should not prepare more than500 mL at a time. At a flow rate of about 1 mL per minute, this shouldbe enough for continuous operation over a typical working day.Stability may be improved by passing the solution through a 5 micronfilter. You can also extend the working life of the solution by storingat 5 °C. (The solution should remain stable for approximately oneweek if stored at 5 °C.) Allow the solution to reach room temperatureprior to analysis.4.3.4 Pump tubingThe pump tubing should be checked regularly by checking theflow-rate (refer to section 3.1.2 ‘Pump adjustment’). Note When concentrated acid is first pumped through the acid tube, theinside of the tubing may turn white, but this does not impair theefficiency of the tube.Ensure samples, reagents and standards are at room temperature priorto analysis. The VGA-77 pump will not operate correctly with hot orcold solutions as the pumping rate may vary with solutiontemperature.4.3.5 Sources (AA only)4.4 Basic methodsHollow cathode lamps or UltrAA lamps can be used for all VGA-77methods for AA analysis.The hydride-forming elements may exist in more than one oxidationstate in samples and standards. (Refer also to section 4.2.2.) Thefollowing analytical methods for sample and standard have beendeveloped to ensure samples and standards are present in the correctoxidation state.4-6 Publication date: May 2004