使用拉曼光谱仪测定乙醇浓度

乙醇通常存在于多种材料中，如酒精饮料、灭菌/消毒溶剂和燃料。其浓度会根据应用情况进行调整。例如，在医疗机构中用于手消毒的乙醇被设置为70-83 vol%，以便消毒有效。最近，作为对抗新型冠状病毒的临时措施，在乙醇难以获得乙醇时，允许使用60vol%*1。当需要使用除一般防腐剂以外的高浓度乙醇产品时，在使用前必须用纯化水稀释。确认稀释后的产品的正确的乙醇浓度是很重要的。FTIR光谱仪通常用于测量浓度，但在本申请说明中，我们介绍了使用拉曼光谱仪对封闭小瓶中样品的乙醇浓度进行定量的结果。Application Note260-AN-0029 Determination of ethanol concentration using a2/4Application NoteRaman spectrometer Determination of ethanol concentration using a Raman spectromete r Ethanol i s commonly found i n a wide r ange of ma t e ri als suc h as alcoholic beve r ages，ster i l izat i on /sani t izat i on so l vents and fue l s. Its co n centration is adjusted d epe n di n g on t h e a p plication. Fo r e xamp l e ， ethanol for h a n d sanit i zat i on us e d i n m edical institut i o n s i s set to 70-83 vo l % so t h at sani t izing i s ef f ective. Rece n tly， as a temporary m easure against the novel coro n avir u s， the u se of 60 vol% ha s been al l owed when et h anol is di ff icu l t to obtai n ". When i t is necess a ry to use high co n centr at i o n ethan o l products other th an general antiseptics， t hey m us t be d il uted with puri f ied wate r pr i or to use. I t i s impo rt ant to co n fir m the co r rect e thanol co n c ent rat i on for t h e di lute d p roduct. An FTIR s pe ctromet e r is often u s e d to m e as u r e t h e conc e ntratio n2， but in this app li catio n n ote， we int r oduce the results f or the qu ant if i cat i o n o f etha n ol concent r ation with the sample i n a c l osed v i al usi n g a Raman spectrometer . Keywords R ama n spe ctr o sc op y， e th a n o l， quanti f i ca ti o n， m a cr o Expe r imental Samples Commercial ethanol-based ant i septics 3High co n centrat i on beverage alco h ol 1Alco h o l beverages 4 V m e a s u remen t u n i t ial co nt a i n ing sa m pl e Figure 1. N RS-4500 R a m a n s p e c tro m e t e r an d ma c r o me a s u r e m en t u n it w it h sa m p l e i n side the sa m pl e co m pa r tm e n t Measuremen t Condi t ions The m acro measureme n t accesso r y was used for th is meas u rement . With t h is unit ， me a su r eme n t can be m a de by s im ply placi n g a closed vial* containing a liquid sample i n the sa m ple c h amber as shown in Figu r e 1. T hi s i s part i cular l y usefu l for m easuri n g h i g hly volati le sampl e s suc h as e thanol. I n add i tion， th e m e a s urem en t time pe r sampl e is as s h o rt as 2seconds ， enab l ing quic k evaluation . * The vial must allows excitation light to pass through. Measurement Conditions Instruments NRS-4500 Raman spectrometer Excitation Wavelength 532 nm Exposure Time 1 second Accumulations 2 Resu l ts 1) Calibration curve A 99.5 vol% ethanol and ul t rapure water were mixed to prepare a standard sample of 0 to 99.5 vol%. A good calibration curve was obtained when i t was created with the peak area near 880 cm' attributed to the C-C-O symmetric stretching vibration shown by the arrow in the ethanol spectrum in Figure 2. Figure 2. R a m a n spec tr um of e t h a no l (l eft) a n d c al ib ra t i on cu r v e (ri ght ) 2) Quantification result Table 1 shows the quantitative results of the ethanol concentrations of three types of commercial antiseptics， a high concentration beverage alcohol ， and four types of alcohol beverages. From high to low ethanol concentrations， it was shown to be similar to the ethanol concentrations listed on the product. Table 1. Et ha n o l c onc e n t r a ti on q u a n t i ta ti v e re s u l ts. Sample [Ethanol concentration stated (vol%)] Ethanol quantitative results (vol%) Ethanol-based antiseptic A (77) 78 Ethanol-based antiseptic B (75) // Ethanol-based antiseptic C (75) 76 High concentration beverage alcohol (66) 64 Distilled spirits [Shochu]X(35) 35 Distilled spirits [Shochu]Y (12) 12 Japanese Sake (13-14) 14 Liqueur (4) 5 Concl u sion Using a Raman spectrometer， the ethanol concentration can be quickly and easily measured in samples such as antiseptics and beverage alcohol. While FTIR can be used to measure in small amounts， Raman spectrometers can be used to measure the solution in a glass or other sealed vial， minimizing the effects of volat i lization. According to materials released by the Ministry of Health， Labor and Welfare， Japan 2 FT/IR Application Note 200-AT-0266 (Quantification of Ethanol in Ethanol-based antiseptics) System Configuration Model Description Part Number Main Unit NRS-4500-532 Raman Spectrometer 7118-JO51A Options RMC-457-115 Macro measurement unit 6882-J601A 3NRS-5500/7500 can also be used. 28600 M ary's C ou r t， East on ， MD 21601 USA JS.CO Supplementary Information Al l samples were put in the same type of glass bottle， placed in the same position and measured. If the shape of the vial differs for different samples， or if an overlapping peak is present from the sample vial， it may be necessary to consider evaluation by peak ratio or multivariate analysis. If the sample is colored (for example， whiskey)， the excitation wavelength needs to be considered to avoid fluorescence. In this application note the calibration curve was created using Excel . Differences from other i nstruments are as follows： FT/IR Can be measured with a small amount of sample， but cannot be measured through a vial. UV/Vis Spectrometer Ethanol has no absorption in the UV-Vis region and must be quanti f ied colorimetrical l y.