Raman 激光拉曼光谱仪定量校准混合样品的稳定性

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Application Note Raman Quantitative Calibration Stability for a2/2 Raman Quantitative Calibration Stabilitvfor a Sample Mixture Recent advances in technology for Raman spectroscopy has resulted in a wealth of applicationcapabilities. Raman spectroscopy is ideal for routine sample quantitative analysis due to the lackof sample preparation， the ability to utilize various sample vials and the rapid speed of spectralcollection. The use of Raman spectroscopy for routine quantitativeanalysis is desirable due to the simple sample handlingrequirements for sample analysis. Due to the manyvariables associated with Raman spectroscopy， specifically，laser power， Raman cross-section， wavelength andintensity stability， Raman is rarely used for quantitativeanalysis. Compared to Raman analysis， there are othermethods that can provide a repeatable quantitativeprediction of unknowns， but these methods can requireextensive sample preparation or extended time for analysis.To demonstrate the capabilities of Raman spectroscopyfor quantitative analysis， a 2 component mixture of liquidsamples was analyzed using a Raman spectrometer andthe results reported. NRS Series Raman Spectrometers Several mixtures of benzonitrile dissolved in ethanol were prepared at 0.1，0.3，0.5， 1.0， 3.0 and 5.0%concentration as standards for development of the multi-component calibration model including a 0.2%mixture to be used as an ‘unknown’for analysis using the calibration model. A Jasco NRS-3100 Ramanspectrometer was used to collect triplicate spectra of the standards using 532 nm excitation and a 60 secondintegration of the CCD with 2 accumulations to obtain spectra with a spectral resolution of slightly less than4 cm-1resolution. Samples were contained within 2 mL HPLC sample vials and a macro accessory used forexcitation/collection of the sample volumes. No further correction of the Raman spectra was performed priorto development of the calibration model or analysis of ‘unknown'spectra. Sample Mixture The various standard spectra as well as an ethanol ‘blank'were used to develop the quantitative calibrationmodel using Jasco's Spectra Manager Quantitative Analysis package. A peak ratio method using the 2234cm-C-N stretch of benzonitrile vs. the 1455 cmC-H bend of the ethanol was used for the development ofthe linear calibration curve. Preliminary calibration results based on the initial triplicate spectra of each standardprovided a calibration curve with a fit of 0.9998 and an R2 of 0.9996， indicating an excellent fit of the data.To evaluate the repeatability of the calibration method， additional spectral data sets of all standards werecollected again after 1 and 2 weeks， providing a total of at least nine spectra of each standard for calculationof the calibration curve. The final calibration curve also provided a linear calibration curve with very little scatter，offering a fit of 0.9997 and an R? (residual) of 0.9995 (Figure 1). As well， the analysis of the‘unknown’samplethat was prepared indicated errors of less than 0.5% for the replicate analyses conducted over the 2 weekperiod. Figure 1. Calibration model for quantitative standard mixtures， including2nd and 3rd week standards analysis. Conclusions The results demonstrate that a reliable calibration model can be developed from Raman spectra of a mixturewithout further correction. The results demonstrate a correlation of 0.999 or better for the quantitativecomponent over a range of concentrations from approximately 0.1 to 5%. Further， the Raman methodprovides repeatable， reproducible results and proves to be stable for extended periods. ( A pplication L ibrary： http：//www. j ascoinc.com/applic a tions ) JASCO INC.Mary’s Court， Easton， MD USATel： ( Fax： ( pplication Library： http：//www.jascoinc.com/applications