准确测定系列15:ICP-OES Measurement

Line Selection The first step in line selection is to simply choose the line(s) that meet the sensitivity requirements for your measurement. More than one line may be necessary due to spectral interferences.Sensitivity: Make sure that the line is not too sensitive (i.e. - going outside the linear working range). Dilutions are easy and hopefully you'll have more than one line that meets your lower limit of detection and quantitative measurement requirements. If you do not have line tables, we have listed the three most popular lines for each element (also included are detection limits for radial and axial view, as well as major interferences) in our Analytical Periodic Table.Precision: The precision of an ICP measurement is a function of many factors that are beyond our control. However, if you require an improvement in precision, consider the following:Try to keep the analyte concentration well within the linear working range. When the concentration falls 100 times the detection limit, the precision begins to fall.Avoid lines requiring spectral correction.Avoid lines that are in spectrally complex regions requiring sophisticated background correction algorithms.Increasing the integration time to as high as 5 seconds should improve the precision. It should not be increased any higher.Use an all glass introduction system including a glass concentric nebulizer. Your washout times will improve along with your precision.Be weary of salting out effects when analyzing high salt containing solutions, but do not use high solids nebulizers unless necessary.If your samples and standards have the same background then you should skip background correction.If the matrices of the samples and standards can be matched then eliminate the peristaltic pump and go 'free flow'. The pump introduces pulsing and the pump tubing stretches, causing the introduction rate to gradually change. If you can avoid the pump then make sure the liquid levels of your samples and standards are the same.NOTE:? Slight differences in hydrostatic pressure will make a difference.Do not begin the measurement unless the instrument has been allowed to warm up for at least an hour. Additionally, working in a temperature-controlled atmosphere is very advantageous.Clean your introduction system and replace the tubing when a) you notice an increase in precision when using glass introduction systems, b) you notice a 'bend or crink' in the Teflon tubing, c) the torch begins to build up residue.