Ratioed spectra

Berzas-Nevado, J.J., Cabanillas, C.G., and Contento-Salcedo, A.M., Simultaneous spectrophotometric determination of three food dyes by using the first derivative of ratio spectra, Talanta, 42, 2043, 1995. 

Erk and Altun [24] used a ratio spectra derivative spectrophotometric method and a high performance liquid chromatographic method for the analysis of miconazole nitrate and metronidazole in ovules. The spectral method depends on ratio spectra first derivative spectrophotometry, by utilizing the linear relationship between substances concentration and ratio spectra first derivative peak amplitude. The ratio... 

For ratioed spectra, it is of interest to ascertain the effect of the various noise sources on the ratioed spectrum (i.e., the transmittance or reflectance spectrum as the case may be), on the absorbance spectrum, and also to determine, as was done previously [1, 2, 5], the optimum value for the sample to have that will give the minimum error of the calculated value. 

NMR spectroscopy is relatively insensitive compared to optical spectroscopies such as Fourier transform infrared, requiring acquisitions of several minutes to obtain high signal-to-noise ratio spectra adequate for process analytical applications. The linear response and low sensitivity of NMR also prevents its use for observing very low level contaminants (<1000ppm) in complex mixtures. 

Bahrain, M., T. Madrakian, E. Bozorgzadeh, and A. Afkhami. 2007. Micelle-mediated extraction for simultaneous spectrophotometric determination of aluminum and beryllium using mean centering of ratio spectra. Talanta 72 408-414. 

A ratio-spectra, zero-crossing, derivative spectrophotometric method was described for the analysis of spironolactone in presence of hydrochlorothiazide [16]. After extracting the drugs from their tablets with 1 1 0.1 N HC1 - methanol, the first derivative of the ratio of their absorption spectra to that of standard solution is computed at 270.7 and 269.9 nm. 

Organics and liquid 1 0 are intimately associated in skeletal carbonates, so much so that often the most obvious effect of bleaching or decay of organics on the spectral properties of biogenic carbonate samples is a decrease in the intensities of the liquid water bands. This is illustrated in ratio spectra in Figures and 6. A ratio of two spectra provides a spectrum of phases present in one sample but absent in the other. As can be seen, all the ratio spectra contain features due to liquid water. 

Ratio spectra of corals of differing ages are shown in Figure 6b. The ratio between spectra of living and Pleistocene samples clearly indicates loss of proteins. The ratio of spectra of living... 

Figure 6. (a) Ratio spectra of slices of Pleistocene Mercenaria, and (b) Ratio spectra for three slabbed specimens of the coral Diploria strigosa. All three samples are composed of aragonite, variations in organic content being the major compositional difference between them. Numbers indicate absorption features due to C-H (1), 0-H (2), N-H (3)> and organic pigments (4) ... 

Erk presented a ratio spectra derivative spectrophotometric method and a Vierordt s method for the simultaneous determination of hydrochlorothiazide in binary mixtures with benazepril hydrochloride, triametrene, and cilazapril [19]. A mass of powder equivalent to one tablet was dissolved in 1 1 methanol/0.1 M Hydrochloric acid (solvent A), shaken for 30 min, filtered and the residue was washed with 3x10 mL of solvent A. Combined solutions were diluted to 100 mL with solvent A, and then diluted with methanol for analysis by (i) Vierordt s method, and (ii) ratio spectra derivative spectrophotometry. For method (i), the absorbance of the solution was measured at 271.7, 238.1, 234.1, and 210.7 nm for hydrochlorothiazide, benazepril, triametrine, and cilazapril, respectively, and the corresponding concentrations were calculated using simultaneous equations. For method (ii), the absorption spectra of solutions containing different amounts of hydrochlorothiazide in a... 

Figure 5. Electron spin resonance spectrum of galactose oxidase (A) and galactose oxidase and Fe(CN)63 at a 1 1 (B) and 1 6 (C) molar ratio spectra were recorded at 100°K, with a power of 20 mw (9.115 GHz) and a modulation amplitude of 2G [galactose oxidase] = 0.5 raM.

The procedures described next were developed for the deconvolution of electronic absorption spectra (UV-visible spectra) but are equally applicable to the deconvolution of infrared, Raman or NMR spectra. UV-visible spectra differ from vibrational spectra in that the number of bands is much smaller and the bandwidths are much wider. Band shape may also be different. UV-visible spectra are also usually recorded under conditions of high resolution and high signal-to-noise ratio. Spectra from older instruments usually require manual digitization from a spectrum on chart paper, at e.g., 10 nm intervals. With the widespread use of computer-controlled instruments, it is a simple matter to obtain a file of spectral data at, e.g., 1 nm intervals. In fact, it may be necessary to reduce the size of the data set to speed up calculations. 

Ghasemi J, Abbasi B, Niazi A, Nadat E, Mordai A. Simultaneous spectrophotometric multicomponent determination of folic acid, thiamine, riboflavin and pyridoxal by using double divisor-ratio spectra derivative-zero crossing method. Anal Lett 2004 37 2609-23. 

The application of chemometric procedures coupled with derivative spectroscopy permits achievement of higher selectivity in determination of P-lactam antibiotics. Currently, chemometric procedures based on the estimated ratio of spectra derivative for the selective determination of P-lactam analogs are the most common. It was proved that the application of the ratio of different-order spectra derivatives permitted the separation of binary and tertiary mixtures of P-lactam antibiotics [22]. During the determination of concentrations of three components (e.g., penicillin-G sodium, penicillin-G procain and dihydrostreptomycin sulphate salts) in a mixture the equation describing the ratio spectra derivative spetrophotometry is as follows ... 

Fig. 6. The application of ratio spectra of derivative spectrophotometry in analysis of p-lactam antibiotics.

Lin Z. Liu J. Chen G. A new method of Fourier-transform smoothing with ratio spectra... 

Murillo J. Lemus J. Garcia L. Application of the ratio spectra derivative... 

Derivative spectrophotometry was applied in different than pharmaceutical analysis areas of analysis. This method was utilised for the determination of amphothericin in various biological samples like plasma, serum, urine and brain tissue [40]. The combination of ratio spectra with their derivatisation allowed to remove spectral interferences caused by a presence of bilirubin in plasma [40]. 

Oxybutynin hydrochloride First derivative of ratio spectra was used for determination of analyte in presence of its degradation product. 24... 

Ertapenem First derivative and first derivative of ratio spectra methods were applied for determination of ertapenem in the presence of its degradation product. The analyte was assayed by the first method at 316 nm in the range 4-60 pg mL-i. The second method allowed ertapenem determination at 298 nm and 316 nm in the same concentration range using spectrum of degradant at 28 pg mL-ias a divisor. 25... 

First derivative of ratio spectra was applied for determination of strontium, magnesium and calcium in Portland cement [44]. The proposed procedure was based on complexation of studied ions with Alizarin Complexone. 

Zhang, Z. and Marshall, A. G. A universal algorithm for fast and automated charge state deconvolution of electrospray mass-to-charge ratio spectra. /. Am. Soc. Mass Spectrom., 9, 225, 1998. 

---