N E W S L E T T E R F R O M TO S H V I N A N A LY T I C A L P V T. LT D. AUGUST 204 TABLE OF CONTENTS Evaluation of Light Intensity Graph and Particle Size Distribution of Mixture Particle Application of Nuclear Magnetic Resonance (NMR) Spectroscopy for the Characterisation of Small Molecules Application of Photovisual DSC Evolved Gas Analysis by TG-FTIR... 2... 4... 7... 9
Evaluation of Light Intensity Graph and Particle Size Distribution of Mixture Particle Introduction The particle size distribution analyzer is useful to confirm the size, width and number of peaks. Shimadzu s laser diffraction particle size analyzers, the SALD series, obtain particle size distribution together with light intensity distribution. The light intensity distribution shows the scattered light intensity from sample particles on each sensor element. The peak intensity gives information on whether the sample concentration is suitable or not prior to measurement. The light intensity distribution graph is the raw data, has unique pattern for different size distribution, and it can be used in pre- and postmeasurement. Hence, it can be used to check whether the particle size distribution is correct or not, especially when measuring samples with unknown particle mixture. Here we introduce the analysis results of single and mixture samples with both the particle size distribution and the light intensity distribution. Samples Two samples of different particle size distribution were used for the measurement. Figure and 2 show the particle size distribution and light intensity distribution pattern of the sample with 0µm at 50% diameter size, whereas Figure 3 and 4 show µm particles at 50% diameter size. Samples are White Morundam/WA (Al O 99.6%) 2 3 #500 and #8000 by Showa Denko K.K. 0µm sample : WA#500 0.5±.0µm by Sedimentation measurement method µm sample : WA#8000.2±0.3µm by Electrical sensing zone method Results and Discussion Single size particle 0µm Figure : Particle size distribution of 0µm Al O 2 3 Figure 2: Light intensity distribution of 0µm Al O 2 3 Single size particle µm Figure 3: Particle size distribution of µm Al O 2 3 Measurement Condition Instrument Accessory Dispersing medium Dispersing agent Sample form Refractive index : SALD-2300 : SALD-MS23 : Pure Water : 0.% Sodium Hexametaphosphate : Suspension :.75-0.20i Figure 4: Light intensity distribution of µm Al O 2 3 The scattered light of bigger particles goes into smaller angle sensors, and smaller particles are detected by larger angle sensors. Particle size and distribution are estimated from raw data as shown in this light intensity graph. 2 AUGUST 204
Mixture of µm and 0µm Figure 5 shows six different particle distribution curves. These samples comprised a mixture of µm and 0µm of Alumina (Al2O 3) powder with different mixing ratio. When the amount of µm particle is more than 7%, the measurement results are accurate at µm vol.% on the accumulative curve (Q3). When the amount of µm particle is less than 3%, the results of concentration become lower than actual concentration. Figure 6 shows the light intensity distribution curves of six different samples having the same mixing ratio as in Figure 5. The light intensity distribution curve for 0µm and µm is shown in Figure 2 and Figure 4 respectively. The intensity of the peak between 60th and 65th (red arrow) shows the amount of µm powder has nearly equivalent intervals of µm mixing percentage. The light intensity graph in Figure 9 shows the clear difference among four different concentration samples. We can confirm the difference between 0% and % by the light intensity distribution curves. 7% µm, 93% 0µm 5% µm, 95% 0µm % µm, 99% 0µm 0%µm, 00% 0µm Figure 7: Overlay particle size distribution (0 7%) 23% µm, 77% 0µm 20% µm, 80% 0µm 7% µm, 83% 0µm 3% µm, 87% 0µm 9% µm, 9% 0µm 5% µm, 95% 0µm Figure 8: Particle size distribution of 7% µm sample Figure 5: Overlay particle size distribution (5 30%) 7% µm, 93% 0µm 5% µm, 95% 0µm % µm, 99% 0µm 0%µm, 00% 0µm 23% µm, 77% 0µm 20% µm, 80% 0µm 7% µm, 83% 0µm 3% µm, 87% 0µm 9% µm, 9% 0µm 5% µm, 95% 0µm Figure 9: Overlay light intensity distribution (0-7%) Figure 6: Overlay light intensity distribution (5 30%) Figure 7 shows four different lower concentrations. The particle size distribution curves of 0-5% are the same, and there is no peak around µm (blue arrow). However, in the particle size distribution of 7% sample, small peaks are observed around µm particle. Figure 8 shows the enlarged distribution graph of 7% sample. Conclusions The light intensity distribution pattern is an extremely useful tool to avoid inaccurate results in samples which contain smaller size contaminants or unknown samples. It is applicable in laser diffraction and scattering method to determine the accuracy of the results. References Abrasive Micro Grain Size JIS R600 AUGUST 204 3
Application of Nuclear Magnetic Resonance (NMR) Spectroscopy for the Characterisation of Small Molecules Background There are a variety of spectroscopic techniques that will give information about the structure of a molecule. Techniques such as FT-IR and Raman can give information about the functional groups and molecular backbone respectively. However, they cannot give all of the information about the molecule and the environment of the nuclei. Nuclear Magnetic Resonance (NMR) is a powerful technique for providing information about functional groups, molecular backbone AND the chemical environment of the nuclei in the molecule. The principle of NMR is that the resonance frequency of a nucleus is determined by its gyromagnetic ratio and the strength of the static magnetic field. If this was the only factor determining resonance then nuclei of the same type would have identical frequencies. However, the resonance frequency of a nucleus also depends subtly on its location within a molecule. More precisely it depends on the electron distribution in a molecule and the shielding effect of the surrounding electrons. The shielding is the result of the static magnetic field inducing electron orbital motion. This motion generates a small magnetic field in the opposite direction to the main field. Thus each nucleus experiences a slightly different magnetic field depending on their location in a molecule. This effect is referred to as chemical shift and is the basis for the chemical specificity that is one of the great strengths of NMR spectroscopy. Chemical shift is not the only information contained in a NMR spectrum. The magnetic interaction between neighbouring nuclei mediated through the bonding network is referred to as J-coupling or scalar coupling. This coupling between nuclei results in multiplets in the NMR spectrum. The number of spectral lines and spacing between them in a multiplet provides additional information about the structure of a molecule. In addition, NMR has the advantage that the amplitude of the NMR signal is directly proportional to the concentrations of the contributing nuclei. Therefore, the ratio of the area under the different peaks corresponds to the number of nuclei per molecule contributing to a resonance. The spectral peak integrals are useful additional information that helps confirm spectral assignments. Analysis To demonstrate the quality of spectra that can be obtained at.4 T corresponding to a H resonance frequency of 60 MHz, the H spectrum from 5 small molecules are shown in Figure. The molecules all have the same chemical formula C6H0O 2 and contain a double bond and a carboxyl group (-C(=O)O) in the form of an ester (R-C(=O)O-R ) or a carboxylic acid (R-C(=O)O-H). 500 mm solutions of each molecule were prepared in CDCl and 00 µl were transferred 3 to a 5 mm NMR tube.. Detailed Interpretation of the Ethyl Crotonate spectrum Figure : Spectra of 5 small molecules with the chemical formula C H O 6 0 2 4 Figure 2: chemical structure of ethyl crotonate AUGUST 204
The H spectrum of ethyl crotonate (figure 2) acquired at 60 MHz is shown in figure 3. The spectrum shows a singlet resonance at 9.23 ppm which can be attributed to the triazine added to the solution to provide a reference signal. There are five other resonances labelled A to E with a range of coupling patterns which can be used for spectral assignment. Resonance A centred at.25 ppm is a triplet with a splitting of 7. Hz. Resonance B centred on.84 is a doublet of doublets with splittings 6.8 Hz and.56 Hz. Resonance C centred at 4.6 ppm is a quartet with splitting 7. Hz. Resonance D centred 5.8 ppm is a doublet of quartets splitting 5.46 Hz and.56 Hz. Resonance E is a doublet of quartets centred at 6.99 ppm with splittings 5.46 Hz and 6.8 Hz. The spectral information is summarised in table. Considering the chemical shifts only and comparing them to typical values for H nuclei, resonance A and B are likely to originate from the two methyl groups (-CH ), with 3 resonance C originating from the methylene group (-CH2-) and the source of resonances D and E is the two alkene H nuclei. The splitting pattern of resonances A and B can be used to assign the appropriate methyl groups. The triplet pattern of resonance A and the single splitting imply that the nuclei assigned to resonance A should have two identical neighbouring H nuclei, while the doublet of doublets structure in resonance B implies two non- identical neighbouring H nuclei with two different splittings. It is now possible to assign resonance A to the methyl H nuclei of the ethyl group (CH3-CH2-). Further evidence for this assignment. is resonance C which has been assigned to the methylene hydrogens of the ethyl group. The quartet structure implies three identical neighbouring H nuclei with the same splitting as resonance A. In fact the triplet, quartet pair of resonances is typical of an ethyl group. Resonance B can be assigned to the second methyl group that is adjacent to the double bond, where the two alkene H nuclei are the source of the two different splittings. Splittings across a double bond are typically larger than those across a single bond and the mutual coupling between the two alkene H nuclei accounts for the 5.46 Hz splitting. The coupling between two H nuclei becomes weaker the greater the number of bonds between them. Resonance E can be assigned to the alkene H nuclei closest to the methyl group, accounting for the 6.8 Hz splitting. Resonance D, therefore, can be assigned to the alkene hydrogen nuclei closest to the carboxyl group with the weaker coupling to the methyl group. Further evidence for the assignments can be obtained by integrating the area under each of the resonances. Normalising the integral of resonance C to a value of 2 it can be shown that the other resonance correspond to the correct number of nuclei. The integrals for Resonances A and B show inaccuracies due to the overlap in the spectrum. It is notable in figure 3 that the multiplet patterns of the resonances are not symmetrical and in the case of the ethyl groups (-CH2-CH 3) do not conform to the binomial pattern, :3:3: and :2:, of peak amplitudes. The asymmetry is particularly obvious in resonance D and resonance E, although it is still noticeable in the other resonances. The source of the asymmetry is strong coupling. At 60 MHz the differences in chemical shift between two neighbouring nuclei is not necessarily much larger than the scalar coupling between them. Under these conditions the weak coupling assumption is no longer valid and coupling patterns associated with weak coupling should not be expected. Table : Summary of the spectral information and peak assignments for ethyl crotonate Label A δh (ppm).25 multiplicity triplet Splitting (Hz) 7. Integral 3.29 (3) assignment ethyl CH 3 B.84 doublet of doublets 6.8,.56 3.24 (3) crotonyl -CH 3 C 4.6 quartet 7. 2 (2) ethyl CH - 2 D 5.80 doublet of doublets 5.5,.56 0.96 () =CH C(=O)- E 6.99 doublet of quartets 5.5, 6.8 0.98 () -CH= Figure 3: H spectrum of 0.5 M ethyl crotonate in CDCl 3 acquired at 60 MHz triazine 9.23 singlet - - triazine reference AUGUST 204 5
Application of Photovisual DSC Photovisual DSC is a differential scanning calorimetry (DSC) system with a transparent quartz glass window in the furnace cover to permit direct observations of changes in the sample status during measurements. A microscope and CCD camera offer magnified images in realtime. These images can be stored, if required. This system is effective for confirming the sample status corresponding to the endothermic and exothermic peaks obtained by DSC. This Application News introduces examples of the application of Photovisual DSC, particularly to foods and drugs. Fig. System Configuration of Photovisual DSC Measurement of Margarine Margarine was sampled in an aluminum cell and heated from -70 C. A feature of this system is the ability to operate in the subzero temperature region and to observe samples undergoing DSC while cooled by a coolant, such as liquid nitrogen. Fig. 3 Fig.2 Photovisual DSC shows the results of DSC measurements on margarine. Multiple endothermic peaks are observed due to the melting of the oils and fats in the margarine. Fig. 4 to Fig. 6 show the sample status at the positions indicated by the arrows. Fig.4 Fig.5 Fig.3 DSC Curve for Margarine Fig.6 AUGUST 204 7
Measurement of Sulfathiazole Fig. 7 shows the result of a DSC measurement from the heating of sulfathiazole after it is pulverized in a mortar and pestle. Sulfathiazole exists in many crystal forms. The peak near 57 C is thought to be a crystal transition from Form 3 to Form. The peak at 202 C is thought to result from the melting of Form. Fig. 8 to Fig. 0 show images of the sample during heating. Observations before and after the 57 C peak (thought to be a crystal transition) indicate no difference in the sample status. After the peak at 202 C, the sample has melted to a liquid. Fig.7 DSC Curve for Sulfathiazole Measurement of Whisky Fig. shows a DSC measurement result from heating whiskey chilled and frozen at -20 C. The endothermic peak at -66 C is due to ethanol and the endothermic peak at -26 C is thought to result from the melting of water. The white cloudy areas increase due to the melting of ethanol at -66 C, as shown in Fig. 3 and 4. Subsequently, the sample becomes transparent after the water melts at-26 C, as shown in Fig. 5 and 6. The white cloudiness is believed to result from separation of a liquid phase within the solid phase due to the melting of ethanol. The irregular lines apparent in Fig. 2 are due to cracking of the frozen sample. Fig. DSC Curve for Whisky 8 AUGUST 204