利用CLS定量同时监测大气中多组分气体的分析

典型的定量模型使用单个峰的高度或面积。CLS（经典最小二乘法）定量是一种多变量分析模型，使用整个光谱数据中的面积，这取决于浓度。因此，CLS是一种有效的定量方法，由于多组分的重叠光谱，很难找到用于定量的单个峰，并且需要同时定量多组分。CLS定量的优点如下所示。首先，由于整个波数区域用于定量计算并且降低了残余噪声水平，因此期望更高的精度。其次，使用CLS可以获得每种化合物的纯光谱。因此，更容易准确地分析多个成分。测量：使用光学路径长度为100m的OPEN-PATH FTIR系统反复监测大气中5种气体成分（CH4、N2O、CO、CO2和H2O）的平均浓度。图1显示了使用预先制备的CLS校准曲线获得的定量结果，对于每个成分，在指定的时间段（5分钟）内，这些结果显示为时间过程数据。显示了时间过程中的浓度变化。Application Note230-QU-0175 Simultaneous Monitoring Analysis of MulticomponentGas in the Atmosphere using CLS Quantitation2/2Application Note Simultaneous Monitoring Analysis of Multicomponen t Gas i n the Atmosphere using CLS Quantitation Introdu c tio n Typica l q u a n titat i on model s use eithe r t he heigh t or area of a single peak. CLS (Classical Least Square) quantitation is a m u lt i var i ate ana l ysis model tha t u ses the area in the enti r e spectra l data， which is dependent o n the concent r ation.Therefore， CLS i s an effect i ve quantitation method where it is di f ficu l t to f ind a single peak for q u a n titation because of ove r l a i d spectra of mult i -compone n ts， and simultaneous qu a ntitation of mu l t i -compone n t is requi r ed. The advantages of CLS quantita t ion are shown below. Fi r st， h i g h er accu r acy is expected because the entire wavenumber r egion is used for the quantitation ca l culation and the residua l noise leve l i s reduced. Second， pure spectra of each compound can be obta i ned using CLS. So， it is easier to a n alyze mu lt i-components accu r ate l y. Measu r ement T h e average concent r atio n s of 5 components of gases (CH4， N，O，co， co， a n d H，O) i n the atmosphere were r e p eatedly mo n itored using the OPEN-PATH F T IR system with an optic a l path leng t h of 100m. Figu r e 1 shows t h e quant i ta t ion r esu l ts o b t a ined using CLS cali b rat i on cu r ves prep a red i n advance， for s p ec i f i ed periods (5 m i n ) for each com p o n ent， which are shown as t i me-course data. The conce n tra t i on ch a nge du rin g the ti me -course is s h own. A ccu m ulatio n s： 200Res ol uti on ： 1c m-1Ap o di z ati o n： C osin e O p t ica l p a t h le n g th： 100 m (OP E N -PA T H FT-IR )S t a n d a r d gas cel l ： 3 m (c a l ib r at io n model ) Figure 1. CLS automatic meas ur eme n t m o n itor scree n Figure 2. Sta n dard gas (uti l izing 3 m cell) R esul t s Figure 2 Results for eac h st an dard gas (100 ppm) i n a sta n da r d gas cell (3m). The absor p tion spectra of t he following g a ses CO， CO， a n d N，O are overlapped. T o d e termine t h e detect i on l i mits， from a concentrat i on of 100 ppm of N，O gas cor r espond i ng to a n absor b ance 0.400， it can be ext r apola t ed t hat a conce n tration of 1 ppm， ha s 0.004 ABS， it i s est i mated th at qu a nt i tatio n to a conc e n trat i on <1 ppm i s possi bl e Figure 3 Calibration models (CH and CO gas) were meas u r ed using a stand a rd gas cell (3m). The calibration c u rves show good l inearity i n the range of 1-120 ppm. The cor r e l at i o n coefficient is better t h an 0.98. Calibration models for CO，，N，O and H，O gas were also created (not shown). The opt i cal path di f ference is cor r ected automat i cal l y in the measurement using the [OPEN-PATH FT-IR]. Figure 3. Cal i br ati on model： CH Figure 4. Cali b r a tion mo del： Co JASCO INC. 28600 Mary's Cour t ， E a s to n ， M D 21601US A T el ： (800) 333-5272， Fa x ： (410) 822-7526 A ppli c a tio n Lib r ary： htt p：//www.jas co in c .c o m/a pp l icatio n s