Ultraviolet and Absorption Light Spectrometry

Howell, James A. S.; Sutton, R. E.

doi:10.1021/a19800040

Cited by 22 publications

(2 citation statements)

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“…5 Since derivative techniques have been widely applied: further development [6][7][8] and reviews were reported. [9][10][11][12][13][14][15][16][17] The main targets of reviews 17 were basic characteristics of DS and a few analytical applications of DS were given (The number of bibliographic references was 93).…”

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Recent Developments of Derivative Spectrophotometry and Their Analytical Applications

El‐Sayed

El-Salem

2005

ANAL. SCI.

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The zero-crossing derivative spectra method is the most common procedure for the simultaneous determination of binary mixtures of their overlapping spectra. As an example, the derivative spectra of binary mixtures of phospho-and silicomolybdenum blue are illustrated in Fig. 1. 23 By measuring the derivative values (heights h1 in Fig. 1) for mixtures of phosphate and silicate at 806 nm (zero-crossing wavelength of silicomolybdate complex), one can avoid the interference by silicate and the phosphate concentration can be determined. By measuring the derivative values (heights h2 in Fig. 1 Moreover, one disadvantage of the zero-crossing method is the necessity of selecting critical wavelengths for the measurements. This selection causes considerable loss of sensitivity and precision in case of binary mixtures. The so-called "ratio spectra derivative" permits the use of the wavelengths corresponding to maximum or minimum and also the use of the distance between consecutive maximum and minimum, thus avoiding these problems. 24 Salinas et al. 25 developed a derivative quotient spectra method with a standard divisor when the spectra of the components are overlapped. The method was based on dividing the spectrum for a mixture into the standard spectra for each of the analyses and driving the quotient to obtain a spectrum that is independent of the analyte concentration used as a divisor. The use of standardized spectra as divisors minimizes experimental errors and background noise. 26 An accurate choice of standard divisors and working wavelengths is fundamental for several reasons. 25,27,28 Easy measurements on separate peaks, higher values of the analytical signals and no need to work only at zero-crossing points (sometimes co-existing compounds have no maximum or minimum at these wavelengths) are advantages for ratio spectra derivative spectrophotometry in comparison with the zerocrossing derivative spectrophotometry. Also, the presence of a lot of maxima and minima in ratio spectra derivative data was another advantage, since these wavelengths give an opportunity for the determination of these compounds in the presence of other active compounds and excipients that possibly interfered with the assay. 29 2·1 Resolution of binary and ternary mixtures by applyingderivative ratio spectra (derivative quotient spectra) The absorption spectrum of a mixture of three compounds; A, B and C is determined by this equation:AM,λ i = εA,λ i CA + εB,λ i CB + εC,λ i CC (path-length is 1 cm)where, AM,λ i is the absorbance value of the mixture at wavelength λi, εA,λ i , εB,λ i and εC,λ i are the molar absorptivities of A, B and C at λi, CA, CP and CC are the molar concentrations of A, B and C, respectively. When we divide this spectrum by the spectrum of a standard solution of one of the components (e.g., A of concentration CA). That is bywe obtainThe first derivative of this spectrum ratio givesIf CC = 0, we have the binary mixture of A and B, and the spectrum in this case is:In Eq. (5) we can see that the derivative ratio spectrum of...

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Recent Developments of Derivative Spectrophotometry and Their Analytical Applications

El‐Sayed

El-Salem

2005

ANAL. SCI.

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“…Some photoacoustic analyzers based on this mechanism have been made in practice. 16,17 In this preliminary work, we further utilized such an instrument to determine directly the TIC existing in solids and waters. Moreover, the reaction kinetics can be monitored by built-in time history records, which are conducive to ascertaining visually the achievement of reaction equilibrium.…”

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A flexible method of carbonate determination using an automatic gas analyzer equipped with an FTIR photoacoustic measurement chamber

Liu¹,

Sun²,

Ranheimer³

et al. 1999

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A Fourier transform infrared spectrometer was employed to determine automatically the total inorganic carbonate (TIC) in solids and waters, based on active photoacoustic absorption of infrared light by carbon dioxide. A 2.0 l reactor, connected to the spectrometer, is immersed in water-bath at 20 °C. After purging with pure N 2 , 5 ml of 0.5 mol l 21 HClO 4 are injected into 50 ml of solid suspension or solution with continuous stirring. The specific absorption of infrared light by the CO 2 evolved induces corresponding fluctuations of temperature and pressure in a measurement chamber. Accordingly, photoacoustic signals, with frequencies dependent on the absorbed wavelengths, are generated and measured by the chamber microphones in the form of an absorption spectrum and concentration. For solids, the method exhibits a linear response up to 120 mg of CaCO 3 with a detection limit of 0.02 mg; in the case of waters, these figures of merit are 36.4 mmol l 21 and 3 µmol l 21 NaHCO 3 , respectively. Since proton consumption by TIC in clay minerals may commonly influence the evaluation of surface acid-base properties, the methodology was applied to determine TIC in three natural illite samples of different origins. In addition, some potential interferences and modifications of this method are discussed. Experimental ReagentsAll chemicals used in the experiments were of analyticalreagent grade or better. A 0.04 mol l 21 stock standard solution

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Absorptionsspektrophotometrie

Schmidt¹

2000

Optische Spektroskopie

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Ultraviolet and Absorption Light Spectrometry

Cited by 22 publications

References 88 publications

Recent Developments of Derivative Spectrophotometry and Their Analytical Applications

Recent Developments of Derivative Spectrophotometry and Their Analytical Applications

A flexible method of carbonate determination using an automatic gas analyzer equipped with an FTIR photoacoustic measurement chamber

Absorptionsspektrophotometrie

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