Ultraviolet and light absorption spectrometry

Hargis, L. G.; Howell, J. A.

doi:10.1021/ac00036a004

Cited by 13 publications

(3 citation statements)

References 114 publications

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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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confidence: 99%

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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“…[17][18][19][20][21][22] Meanwhile, several multi-component determinations of inorganic substances based on the application of these methods to spectrophotometric data have been reported. [23][24] The main goal of the present report is developing a simple and proper method for simultaneous spectrophotometric monitoring of iron and cobalt traces in different water samples by using PAN as a sensitive chelating agent together with chemometric approaches such as PC-ANN, PCR and PLS. In the PC-ANN model the scores of the principal component analysis (PCA) of the response data of the calibration mixture were used as an input layer.…”

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Simultaneous Spectrophotometric Determination of Iron and Cobalt in Micellar Medium by Using a Principal Component Artificial Neural Network and Multivariate Calibration

Nekoei

Mohammadhosseini

2007

J Chinese Chemical Soc

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A simple and reliable method for simultaneous spectrophotometric determination of iron(II) and cobalt(II) has been established. The method is based on complex formation with 1‐(2‐pyridylazo)‐2‐naphtol (PAN) in a micellar medium. Despite a spectral overlap, Fe2+ and Co2+ have been simultaneously determined with chemometric approaches involving principal component artificial neural network (PC‐ANN), principal component regression (PCR) and partial least squares (PLS). Various synthetic mixtures of iron and cobalt were assessed and the results obtained by the applications of these chemometric approaches were evaluated and compared. It was found that the PC‐ANN method afforded relatively better precision than that of PCR or PLS. The proposed method permits detection limits of 0.05 and 0.07 ng mL−1 for Co and Fe, respectively. The influences of pH, ligand amount, solvent percentage and time on the absorbance were also investigated. The proposed method was also applied satisfactorily for the determination of Fe(II) and Co(II) in real and synthetic samples.

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“…Por outro lado, a compilação de espectros de absorção sob a forma de atlas ou bases de dados é usada para: i) identificação e verificação do grau de pureza de compostos; ii) cálculo da diferença de energia entre estados electrónicos e do momento dipolar da transição. O desenvolvimento da espectroscopia de absorção UV-Vis tem sido constante ao longo dos últimos anos, sendo a técnica revista em número especial da revista Analytical Chemistry, de dois em dois anos, desde 1945 [24].…”

Section: Espectroscopia Na Região Do Ultravioleta-visível (Uv-vis)unclassified

Aplicação de poli(anilina-co-3-aminobenzóico) e octadecil-trimetóxi-silano como revestimentos protetores de ligas de alumínio

Sinisterra¹

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Taking into account the constant problems that presents with corrosion processes, this research work has focused primarily on the change in surface properties of aluminum alloys used in aircraft, AA2024 and AA7075, with mono and bilayers using as a base octadecyl trimethoxy silane (ODTMS) + poly (aniline-co-3-aminobenzoic / PAni3ABA) to find optimum conditions for reducing corrosion punctiform. Later, it evaluates the protective features of the films through corrosion tests such as open circuit potential, anodic polarization curves and electrochemical impedance spectroscopy in order to characterize the electrochemical behavior of the samples. They were also carried out optical microscopy analysis to verify the efficiency of protection against corrosion of the coatings proposed before and after corrosion testing. The results obtained show that the layers used improve corrosion resistance in the following order:PAni3ABA> ODTMS + PAni3ABA> ODTMS, the first being the one that presented the best results as larger shifts towards more positive values, reduced and fewer corrosion points after performing the polarization curves. In addition to compliance tests for the films were also made characterizations of alloys by SEM.

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Ultraviolet and light absorption spectrometry

Cited by 13 publications

References 114 publications

Recent Developments of Derivative Spectrophotometry and Their Analytical Applications

Recent Developments of Derivative Spectrophotometry and Their Analytical Applications

Simultaneous Spectrophotometric Determination of Iron and Cobalt in Micellar Medium by Using a Principal Component Artificial Neural Network and Multivariate Calibration

Aplicação de poli(anilina-co-3-aminobenzóico) e octadecil-trimetóxi-silano como revestimentos protetores de ligas de alumínio

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