汽车中流体检测方案(红外光谱仪)

scoIRAPPLICATION NOTE 03-03Analysis of Automotive FluidsUsing with FTIRContact：8649 Commerce Dr. Easton， MD 21601800-333-52722Fax：410-822-7526www.jascoinc.com Introduction The liquid sample is one of the most common types ofsamples submitted for analysis and comprises a vast array ofpure compounds and solutions. As an example， severalliquids are used in an automobile to sustain critical elementssuch as lubricating the engine or drive train and to supplymundane functions like washing the windows or generatingelectrical power.This paper will describe the analysis ofseveral solutions used in automobiles. Figure 1. Transmission and ATR spectra of methanol. The traditional infrared analysis method for fluid samples is tocollect an infrared transmission spectrum of a thin film of theliquid contained between the windows of an infrared liquidcell. Not all liquids， however， can be analyzed with infraredspectroscopy in this manner. For samples that are aqueous，viscous or chemically reactive， an infrared liquid cell iscumbersome and labor intensive. Frequently， specialwindows with a reduced spectral range must be used and thecellcan be difficult to|keepclean to preventcrosscontamination. Figure 2. Spectrum of windshield washing solution.Infrared analysis using Attenuated Total Reflectance (ATR)accessories like the diamond single-reflection micro-ATR require no sample preparation and greatly simplify thecollection of FT-IR spectra. The liquid sample is placed ontothe ATR crystal and the sample spectrum is collected. Avolatiles cover supplied with the accessory can be used tocover the sample to prevent evaporation during analysis. Thesample is then cleaned from the crystal surface and theaccessory is ready to collect additional spectra. ATRanalysis methods are less complicated than using liquid cells，are fast and a very small amount of the sample is needed. Figure 3. Spectra of two samples of anti-freeze， normal-blue and the extended lifetime-purple. The resulting data can be searched against a digitaldatabase of ATR spectra for positive identification. Despitechanges in the relative peak intensity of the absorptionbands， due to the internal reflection mechanism of ATRaccessories， spectra can also be compared to transmissiondata. As an example， Figure 1 is a plot of the transmissionand ATR spectra of methanol. Figure. 4. Extended mileage antifreeze minus the normal. Spectra were collected using a Jasco FTIR-460 Fouriertransform infrared spectrometer equipped with a GoldenGateTM micro-ATR accessory.Sample volumes of 20microliters were pipetted onto the ATR surface and thespectra collected. No sample preparation was necessary toobtain the various spectra and the liquid sample is simplywiped from the crystal surface after data collection. Ifnecessary， a solvent that will remove the sample is used toclean the diamond crystal surface. Figure 5. Analysis of 10W30 engine oil (green)， powersteering fluid and two transmission fluids (red) FT-IR spectra of 64 scans at 4 cm"'resolution were coaddedand averaged to obtain the single-beam background andsample spectra. Figure 2 is a spectrum of windshieldwashing solution and it can be readily observed thatmethanol (Figure 1) is the major component. The watersolvent increases the intensity and band broadening for theO-H stretch and bending modes. Figure 6. Spectrum of brake fluid. Figure 3 illustrates the spectra of two samples of anti-freeze.While the spectra for the "normal" anti-freeze and theextended lifetime solution appeared identical， a subtraction ofthe standard ethylene glycol solution from the extendedmileage formulation reveals a spectrum of the component(s)that presumably extends the anti-freeze lifetime. Analysis of 10W 30 engine oil， power steering fluid and twoautomatic transmission fluids (ATF 3 and ATF 4) all yieldedspectra representative of long-chain aliphatics as illustratedin Figure 5. The only discernible difference is the additionalpeaks at 1730 and 1151 cm"， which highlight a similaradditive in the ATF and power steering samples. Figure 6 isa spectrum of brake fluid and was interpreted as a complexalcohol or possibly a diol， providing the requisite lubricationand compression characteristics. The most challenging sample was battery acid. Mainlysulfuric acid， battery acid is extremely corrosive andwill etch or react with almost every standard infraredwindow or ATR element. By contrast， the diamondelement of the ATR is not damaged during analysis.The spectrum of the acid solution is displayed asFigure 7. Figure 7. Battery Acid. Conclusions The Golden GateTM single reflection micro-ATR is a simple，easy-to-use accessory for the analysis of liquids andsolutions. The ATR technique is simple， rapid and veryreliable for sample characterization. The analysis method isnon-destructive and can be used to collect data from aminimal amount of sample. Acknowledgements： Pine Belt Automotive， Lakewood， NJ. and Specac Inc， 500Technology Court， Smyrna， GA 30082 Tel： 800 447 2558Fax： 770 319 2488 www.specac.com， for the ATR. Jasco， Inc.