Second-order Derivative Spectra Research Articles

Second-order derivative spectrophotometric assay for imipramine hydrochloride and diazepam in pure admixtures and in dosage forms

The determination of imipramine HCl and diazepam in tablets by derivative spectrophotometry is described. The drugs in combined preparations have been quantified using the second-order derivative spectra of their solutions in 0.1 M HCl. The method has been applied to pure drug mixtures as well as commerical preparations and was found to be precise and reproducible. Compliance of Beer's Law was observed in the concentration range of 10–70 μg ml −1 for imipramine HC1 and 2–8 μg ml −1 for diazepam. Lower limits of detection at the 95% confidence level were 1.96 μg ml −1 for imipramine HCl and 0.21 μg ml −1 for diazepam.

Identification of tryptophan and tyrosine residues in peptides separated by capillary electrophoresis by their second-derivative spectra using diode-array detection

The use of diode-array detection allows the non-destructive identification of tryptophan and tyrosine residues in complex peptide mixtures separated by capillary electrophoresis. Second-order derivative spectra of both amino acids show significant differences while zero-order spectra are overlapping to a great extent. A mixture of peptides containing tryptophan and/or tyrosine residues was used to evaluate this method. Tryptic peptide maps of carbonic anhydrase and of the bacterial chaperonin protein GroEL, and of an autodigest of trypsin were characterized for tryptophan- and tyrosine-containing peptides. Automated spectra library search was performed successfully.

Determination of atenolol, nifedipine, aspirin and dipyridamole in tablet preparations by second-order derivative spectrophometry

The paper discusses the quantitation of atenolol, nifedipine, aspirin and dipyridamole in tablet preparations by derivative spectrophotometry. Atenolol and nifedipine in combined preparations have been quantified using the second-order derivative spectra of their solutions in 0.1 N hydrochloric acid. Aspirin and dipyridamole were quantified using the second-derivative difference spectra obtained by scanning equimolar drug solutions in 0.1 N HCl and 0.1 N NaOH. The method has been applied to pure drug mixtures as well as commercial preparations and is found to be precise and reproducible. The detection limits at 2.5% level of significance for the drugs of atenolol, nifedipine, aspirin and dipyridamole were found to be 1.53, 0.72, 1.30 and 1.46 μg/ml respectively.

Application of Normal and Second-Order Derivative Spectroscopy in Identifying Organic Acids and Sugar Acids in Liquid Chromatography with On-Line Photodiode Array Detection

Abstract The UV-spectra of 16 compounds including organic acids and sugar acids were recorded at pH 2.5 using photodiode array detection in three different chromatographic systems: an ion exchange column with phosphate buffer as eluent (I), a C-S reversed-phase column with sulphuric acid as eluent (II) and a C-8 reversed-phase column with hydrochloric acid as eluent (III). Differences in the normal spectra in each of the systems were evaluated by calculating match factors between the spectra. Normal spectra and the second-order derivative spectra gave match factor ranges of 603–1000 and 0.1–999. respectively. The similarity between the normal spectra was very good and excellent between chromatographic systems I and II On the other hand, the similarity between the second-order derivatives of the spectra was not as good. Thus the normal UV-spectra can be used, together with the retention times, for reliable identification despite of the spectral similarity of some acids. Molecular connectivity indices up to...

Second-derivative spectrophotometric determination of naproxen in the presence of its metabolite in human plasma.

A second-derivative spectrophotometric method for the determination of naproxen in the absence or presence of its 6-desmethyl metabolite in human plasma is described. The method consists of direct extraction of the non-ionized form of the drug with pure diethyl ether and determination of the naproxen by measuring the peak amplitude (mm) in the second-order derivative spectrum at a wavelength of 328.2 nm. The efficiency of the extraction procedure expressed by the absolute recovery was 94.6 +/- 0.7% (mean +/- s) for the concentration range tested, and the limit of quantification attained according to the IUPAC definition was 2.42 mg l-1. The linear dynamic range for naproxen was 5.0-100.0 mg l-1, the correlation coefficient for the calibration graphs was excellent, r = 0.99993 (n = 6), the precision (Sr) was better than 4.58% and the accuracy was satisfactory (Er < 2.32%). The results obtained by the proposed method were in good agreement with those found by an HPLC method.

High resolution spectroradiometry: Spectral reflectance of field bean leaves infected by Botrytis fabae

The spectral leaf reflectance properties of field bean ( Vicia faba) infected by the fungus Botrytis fabae were investigated over the wavelength range 400–1100 nm. The percentage of leaf surface affected by lesions was estimated, as well as fresh weight, and content of photosynthetic pigments per unit leaf area. Measurements of photosynthetic rates and stomatal conductance were conducted on groups of diseased and control leaves. Chlorophyll b content increased significantly as the proportion of leaf surface infected increased, but no statistically significant change was observed in chlorophyll a content. Rates of leaf photosynthesis were reduced significantly compared to healthy leaves even at low levels of infection (<10 %). Reduced photosynthesis may be attributed to decreased stomatal conductance. No changes in spectral reflectance were evident before visual symptoms were observed. The most significant changes in spectral reflectance associated with the disease were a flattening of the response in the visible region and a decrease in the near-infrared reflectance shoulder at 800 nm. Both these responses may be attributed to collapse of leaf cell structure as the fungus spread. Correlations between percentage infection and reflectance in the visible region (peaks at 525 nm and 580 nm) were higher in the first-order derivative spectra than for the original, zero-order reflectance spectra, whereas the red-edge location was poorly correlated with infection. Second-order derivative spectra gave lower correlations with infection. First-order derivatives of leaf reflectance could therefore be useful for remote sensing of this disease and other diseases and stresses which result in necrosis of leaf tissue, if detectable at the canopy level.

Application of an automated interpretation system for infrared spectra: Part I. Automated qualitative analysis of polymers

This paper describes the automated generation of interpretation rules for the characterization of aromatic polymers. Peak tables obtained from diffuse reflectance and attenuated total reflectance spectra are used to generate these rules. In order to improve the information content of the peak tables the role of second-order derivative spectra is investigated. Spectral windows, characteristic for a particular fragment, tend to become less specific due to an increase in the number of peaks. Application of interpretation rules obtained from homopolymers to spectra of copolymers and blends yields satisfactory results. Further improvement in the rule generation process is achieved by using mixture spectra.

Determination of captopril and captopril-hydrochlorothiazide combination in tablets by derivative UV spectrophotometry

Assay procedures based on derivative spectrophotometry have been developed for the determination of captopril alone or in combination with hydrochlorothiazide in tablets. Captopril (5.0–25.0 μg/ml) can be determined by measuring the amplitude of the maximum D 2,258nm of the second-order derivative spectrum. Combinations of captopril (6.0–14.0 μg/ml) and hydrochlorothiazide (3.0–7.0 μg/ml) in a ratio of 2:1 can be determined using the simultaneous equations method with measurements of the amplitudes of the maximum-minimum of the first-order derivative spectrum D 1,278–260nm and D 1,213nm. The linearity of the calibration curves was excellent ( r>0.9997), the precision (RSD) better than 1.6% and the relative errors ( E r) less than 2.6%. The methods were succesfully applied to commercial tablets containing captopril alone or captopril in combination with hydrochlorothiazide.

Use of scanning diode array detector with reversed-phase microbore columns for the real-time spectral analysis of aromatic amino acids in peptides and proteins at the subsmicrogram level: Applications to peptide and protein microsequencing

The characteristic zero- and second-order derivative spectra of phenylalanine, tyrosine and trytophan are described and used to identify aromatic residues contained in sub-microgram amounts of polypeptides and proteins during their elution from reversed-phase short microbore columns under gradient conditions. Spectral data were acquired with a commercially available scanning diode array detector. The method allows the non-destructive identification of tryptophan residues in complex polypeptide mixtures such as tryptic maps and enables the selection and isolation of such peptides for amino acid sequence analysis. The sub-microgram level of sensitivity is due to the small peak volumes and cosequent elevated solute concentrations obtained on short (< 10 cm), microbore (2 mm I.D.) reversed-phase columns.

Direct determination of cis-dichlorodiammineplatinum(II) in urine by derivative spectroscopy.

A derivative spectrophotometric method for the determination of the antitumor agent cis-dichlorodiammineplatinum (II) in urine has been developed. The method is based on the complexation of cis-dichlorodiammineplatinum (II) with N, N'-bis (3-mercapto-2-quinoxalinyl)-1, 3-propanediamine. Optimum conditions for quantification of cis-dichlorodiammineplatinum (II) were established. The complex formed was stable in urine, and the recovery of platinum from urine was 92-95%. Interference arising from urine can be avoided by measurement of the second-order derivative spectrum. The relative standard deviations of the present method were 3.9% and 1.9% for the determination of 0.2 and 2.0 ppm of platinum in urine, respectively.