CaF2板中硬脂酸钙检测方案(红外光谱仪)

Application Note280-SO-0006 2/2Minimizing the Effects of Water Vaporand Carbon Dioxide in IR SpectraApplication Note Minimizing the Effects of Water Vapor and CarbonDioxide in IR Spectra Introduction Atmospheric water vapor and carbon dioxide (CO，) strongly absorb in the infrared regionand can interfere with the analysis and detection of weak sample peaks due to the additionalpeaks in the spectrum. In order to reduce the effect of the background peaks associated withH，0 and CO， it is important to maintain the concentration of water vapor and CO， at the samelevel when measuring both the background and sample. In this application note， we would liketo introduce a couple measurement options to minimize the effects of CO， and water vapor，including “Shuttle Measurement”and“Purge and Vacuum” Measurement Method ATR PRO ONESpectrometers 1.Shuttle Measurement In this method the sample is placed in a sample shuttle (with background and sample positions) in the samplecompartment， this allows background and sample measurements to be made without opening the sample compartmentlid. Using a sample shuttle allows measurements to be made without the effect of changes in the atmosphere. Improvedspectra are obtained with reduced background peaks from water vapor and CO， by making the measurements one afteranother in short time. This is an easy to use and effective method for transmission measurement. 2. Purge and Vacuum +Interval Measurement Program This is useful for transmission measurement or for use with sampling accessories such as ATR or DRIFTS. Both purgeand vacuum reduce the amount of water vapor and CO， in the instrument by removing them from the optical path. Whenusing this method， the level of purge or evacuation has to be constantly maintained between background and samplemeasurements. Purge or vacuum are useful when using the Interval Measurement Program to provide continuousmeasurement of aprocess without the effects of changing water vapor or CO， levels. The data obtained using purge orvacuum under constant conditions allows much easier acquisition of spectra without the effects of vapor and CO，. Examples of Measurement Measurement examples obtained with methods 1 and 2 above are introduced below. Method 1 was used to measure a thin film of calcium stearate on the surface of a CaF，plate. Figure1 shows the results ofmeasurement with and without using the shuttle. When measuring peaks with low absorption such as in thin films， watervapor and CO， greatly influence the acquired spectrum. When using the shuttle， it can beobserved that the effects ofwater vapor and carbon dioxide are significantly decreased. Method 2 was used to measure a vinyl chloride film using a full vacuum system with an ATR accessory. The resultsof interval measurement are displayed in Figure 2. It can be observed that the data where the level of vacuum wasnot maintained shows the effects of water vapor and CO，.In this case， measurement usually has to be repeated afterreleasing the vacuum. During interval measurement， it is easy to continuously measure spectra without the effects ofvapor and CO， using a full vacuum FTIR spectrometer. Figure 1. Shuttle measurement result Figure 2. Full vacuum+interval measurement result JASCO USA 28600 Mary's Court， Easton， MD 21601 USATel： (800) 333-5272， Fax： (410) 822-7526Application Library： jascoinc.com/applications JASCO USAMary’s Court， Easton， MD USATel： ( Fax： ( pplication Library： jascoinc.com/applications Copyright O JASCO Corporation Atmospheric water vapor and carbon dioxide (CO2) strongly absorb in the infrared region  and can interfere with the analysis and detection of weak sample peaks due to the additional  peaks in the spectrum. In order to reduce the effect of the background peaks associated with  H20 and CO2 it is important to maintain the concentration of water vapor and CO2 at the same  level when measuring both the background and sample. In this application note, we would like  to introduce a couple measurement options to minimize the effects of CO2 and water vapor,  including “Shuttle Measurement” and “Purge and Vacuum”.