Single-band method

It is usually easy to apply the single-band method to ultraviolet-visible absorption spectra, as only one or two bands of the analyte are observed. In ultraviolet-visible absorption measurements, it is possible to use a solvent that has no absorption band within this spectral region. By contrast, it is not always so easy to apply the single-band method to infrared absorption spectra, which usually consist of a number of bands arising not only from the solute but also from the solvent. If a sample contains two or more dissolved substances as solutes, the observed spectrum becomes even more complex. Many bands may overlap other bands at least partially. In such a case, a key band for quantitative analysis should be selected with care and its intensity should be measured in an appropriate manner as described in Section 3.4.2. It is necessary to make the signal-to-noise ratio of... 

In addition to these problems in applying the single-band method to quantitative infrared spectroscopic analysis, the single-band method is not suitable for determining the molar ratios of two or more substances existing in a sample. The single-band method, which depends only on the selected key band, does not utilize all the other bands in the observed infrared spectrum. Thus, it is reasonable to seek an alternative method that makes the optimum use of an entire infrared absorption spectrum for quantitative analysis. 

Chemometrics [2-6], a suite of the multivariate data analyses techniques, has been developed to overcome the hmitations of the single-band method. These techniques utilize all the infrared absorption bands over a wide wavenumber region as multivariate data for quantitative analysis, and can handle multicomponent samples simultaneously. In other words, the methods of chemometrics in quantitative infrared spectroscopic analysis are mathematical procedures to apply the concept of Beer s law to various problems in order to extract from them as much usefiil information as possible. In this chapter, the term spectroscopic calibration or just calibration is used to represent such procedures. 

In quantitative analysis by the single-band method, the concentration c of an analyte is determined by measuring the absorbance A of a key band of the analyte. For this purpose, the relationship between c and A should be determined in advance from sample solutions with known values of c, as illustrated in the example calibration plot shown in Figure 7.1. The result in Figure 7.1 indicates that a linear relationship exists between c and A. This means that A is proportional to c, and Equation (7.1) is applicable to the sample. The molar absorption coefficient e can be calculated from the gradient of the linear relationship obtained (usually called the calibration line). 

PGE was isolated as desribed in Material and Methods. SDS-PAGE electrophoresis of purified protein showed a single band migrating at approximately 60 kDa. This observation is not in the agreement with the calculated molecular weight of 35 584. However a similar effect has been observed previously in case of PGI and PGC. Apart of the N-glycosylation which plays role in all PGs (Fig. 3), O-glycosylation may also be present as indicated by the band size shift after a treatment of PGE with O.IM NaOH (data not shown). 

Copper selenide is also used in solar cells [200]. TOPO-capped CuSe nanoparticles were synthesized from Cu(Se2CNEt2)2 using a single-source method [201]. Copper selenide nanoparticles have also been prepared and XPS spectra, valence bands and Auger transitions reported for the molecular clusters Cui46Se73(PPh(3))(202) and Cu2Se [203]. Photoemission features were reported for both species. 

This method measures total unsaturation in a sample by the multivariate analysis of Fourier transform infrared spectra. It correlates the absorbance in the spectral regions corresponding to two major types of unsaturation with their concentrations. This is an extension of univariate least squares analysis that correlates a single band absorbance height or area with concentration. 

Mesohemin IX prepared by this method shows a single band on polyamide tic (benzene/methanol/formic acid, 110 15 1 and methanol/acetic acid 100 2)10 and on silica gel tic14 (benzene/methanol/formic add, 110 30 1). The electronic spectrum of the pyridine hemochrome, prepared by reducing the mesohemin (in pyridine) with an aqueous solution of sodium dithionite, contains the bands (4 N pyridine, 0.2 N KOH) Xmax 407.5, 516, 546.2 nm. e 139.5,20.9,35.8 (mAT1). 

On gel electrophoresis, the purified antibody preparations yield single bands when the gel is stained for proteins. However, on gel isoelectrofocus-ing, differences in the results maybe noted, as shown in Fig. 15. Several protein isomers were present in each antibody preparation, with 7 isomers being detected in the anti-BSA antibodies (B) and 11 isomers in the anti-fucose antibodies (F). The coupled electrofocusing-agar diffusion method showed that each isomer of the anti-fucose set possessed the same antibody activity with the antigen, a-L-fucosyl-BSA. 

One other system investigated in detail by TRIR is the photolysis of Rh(> -C5Mes)(CO)2 in Kr(l) and Xe(l). Both the TRIR technique with an IR laser and the method with the FTIR spectrometer synchronized to the pump laser pulse have been reported. The photoproducts are assigned as Rh(> -C5Me5)(CO)Ng on the basis of their IR spectra in the carbonyl-stretching [v(CO)] region (a single band at ca. 1945 cm ) and their reactivity toward CO and alkanes. The krypton complex proves to be far more reactive than the xenon complex even at lower temperature. Toward CO, there is a difference in reactivity of a factor of ca. 200 at comparable temperatures ... 

The main band in Figured, upon redistribution, gives a single band. The active principle of bacitracin is therefore unquestionably a unique polypeptide of considerable complexity. A very unusual observation in our experience with the method of countercurrent distribution as applied to such materials is the fact that so far, only a single active band appears. Can it be that this organism produces only a single antibiotic If not, this is the first instance where the distribution method has failed to reveal the presence of more than one active principle. 

HPLC analysis on individuals with Hb D Punjab trait shows two peaks, one at the A position and the other at the D position, with Hb D forming 30% to 40% of the total Hb. The Hb F and Hb A2 concentrations are within or slightly above the reference intervals. Electrophoresis at alkaline pH shows two bands, one in the A position and the other in the S position. On electrophoresis at acid pH, a single band in the A position is noted. HPLC is the preferred method for identification of Hb D, because a similar electrophoretic pattern, on both alkaline and acid pH, is seen with Hb G. CBC analysis is unremarkable except for the presence of target cells on the blood smear. 

The results of Shankar and Lehnhoff [77] confirm the validity of the procedures currently used for the interpretation of HPLC data, which are based on moment analysis of the experimental data and on the additivity of the first and second moments of the distributions (see next section). These results also show that this approach is not valid for short systems. Multiple peaks or shoulders on a single band may appear, due to the interaction between transport and retention phenomena. Then the method of moment analysis is inadequate to characterize the... 

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