CD的同时多探头SMP测量和使用积分球测量丙氨酸粉末样品

Application Note 2/3Simultaneous Multi-Probe (SMP) Measurement of CD and LD using DiffuseApplication NoteReflectance (DRCD) Simultaneous Multi-Probe [SMP] Measurement of CD and LDusing Diffuse Reflectance [DRCD] for Alanine powder samples Introduction Generally， a sample for CD measurement needs to be in aliquid state to allow transmission measurement， more recentlythere has been increasing requirement for CD measurementof samples that are insoluble or may change structure insolution. These types of sample are best measured insolid state. Although CD measurement can be made intransmission for solid samples， there is a requirement forsample preparation； such as making a pellet and if sampledilution is required， sample recovery can be difficult. As analternative， measurement using Diffuse Reflection (DR) CDis recommended. 1)， 2) This application note illustrates theuse of DRCD measurement with the DRCD-575 diffusereflectance accessory (See Fig. 1.) optimized for the J-1500CD spectrometer with the multi-probe simultaneous CD/LDmeasurement. DRCD uses incident light to illuminate a solid sample andan integrating sphere to collect the diffusely reflected lightwhich is focused onto a detector (See Fig. 2.) However， CDmeasurement of solid samples can be influenced by LD (lineardichroism) derived from optical anisotropy， this needs to beevaluated and removed in order to minimize artifacts in the CDmeasurement. The J-1500 CD spectrometer allows the estimation of artifactsin the CD signal by using a quad digital lock-in amplifierwhich offers the Simultaneous Multi-Probe function (SMP)measurement of both CD and LD. In this example of DRCD measurement， samples of L-andD-alanine powder were used. Keyword ： powder sample， amino acid， Diffuse reflectancecircular dichroism， DRCD method，L-Alanine， D-Alanine 28600 Mary's Court， Easton， MD 21601 USA Fig. 1 Model DRCD-575 Powder CD Unit Fig. 2 Optical layout， DRCD-575 DRCD-575 Diffuse Reflectance Accessory As shown in Figure 2， Diffuse Reflectance CD (DRCD) can be measured by placing a powder sample inthe measurement position for diffuse reflection (opposite to the inlet port of incident light) and by locatingthe detector in close contact with the integrating sphere at 90 degrees to the incident light axis. Also， Diffuse Transmission measurement can be made by setting the sample at the inlet port of incidentlight and a diffuse plate (white plate) is located at the sample position for diffuse reflection measurement.In diffuse transmission measurement mode， dilution is often required and it is sensitive enough formeasurement of very small amounts of sample. Measurement In order to minimize the influence from optical anisotropy， the alanine powder sample was well groundusing a pestle and mortar and then the simultaneous CD and LD measurement was performed using themulti-probe function of the J-1500 CD spectrometer. System configuration： Conditions： P/N：7000-J006AJ-1500-150ST CDWavelength range：300-200 nmSpectrometerCD/LD sensitivity：10000 mdeg/1.0 delta ODScan speed：100 nm/minP/N： 7069-J034APML-534 FDCD PMTResponse：1 secDetectorPhotometric mode：DRCD， DRLDData interval：0.1 nmP/N： 7069-J025AFLM-525 N2 gas flowSpectral2 nmmeterbandwidth [SBW]：Number of5P/N： 7069-J075ADRCD-575 Solidaccumulation：state(powder)CD measurement unit (powder cell incl.) ( Application L i b rary： http：//www.jascoinc.com/applications ) Results The DRCD and DRLD spectra of L- and D-alanine powder samples are shown in Fig. 3. In the CD mode，L- and D-alanine spectra obtained are mirror images showing the same intensity of plus and minus signrespectively. In the LD mode， the signal intensity of each L and D spectrum obtained is less than +/-0.005 AOD. These results indicate that the influence from optical anisotropy can be considered to be at anegligible level. This application confirms that the J-1500 CD spectrometer fitted with the DRCD-575 diffuse reflectanceaccessory with multi-probe function is an excellent tool for the analysis of solid-state powder materials. This powerful technique can be expanded to CD measurement of other solid-state materials such asmetal complexes and super molecules. Fig.3 CD and LD spectra of L-and D-alanine (accumulated) References Ettore Castiglioni and Paolo Albertini， CHIRARITY， 2000， 12，291-294.Huibin Qiu， Yoshihira Inoue and Shunai Che， Angew. Chem. Int. Ed.2009， 48， 3069-3072 JASCO INC. ( Application L i brary：http：//www.jascoinc.com/applications ) JASCO INC.Tel： ( Fax： ( pplication Library： http：//www.jascoinc.com/applications JASCO INC.Mary's Court， Easton， MD USATel：( Fax： (opyright O JASCO Corporation