Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Spectrophotometry”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 829 records · Page 46Linked to original sources
PubMedDate not supplied

Determination of trace cadmium in waters by flame atomic absorption spectrophotometry after preconcentration with 1-nitroso-2-naphthol-3,6-disulfonic acid on Ambersorb 572.

A procedure for the determination of trace amount of cadmium after adsorption of its 1-nitroso-2-naphthol-3,6-disulfonic acid chelate on Ambersorb 572 has been proposed. This chelate is adsorbed on the adsorbent in the pH range 3-8 from large volumes of aqueous solution of water samples with a preconcentration factor of 200. After being sorbed, cadmium was eluted by 5 mL of 2.0 mol L(-1) nitric acid solution and determined directly by flame atomic absorption spectrophotometery (FAAS). The detection limit (3sigma) of cadmium was 0.32 microg L(-1). The precision of the proposed procedure, calculated as the relative standard deviation of recovery in sample solution (100 mL) containing 5 microg of cadmium was satisfactory (1.9%). The adsorption of cadmium onto adsorbent can formally be described by a Langmuir equation with a maximum adsorption capacity of 19.6 mg g(-1) and a binding constant of 6.5 x 10(-3) L mg(-1). Various parameters, such as the effect of pH and the interference of a number of metal ions on the determination of cadmium, have been studied in detail to optimize the conditions for the preconcentration and determination of cadmium in water samples. This procedure was applied to the determination of cadmium in tap and river water samples.

Cadmium↗
PubMed1990

Quantitative IR spectrophotometry of peptide compounds in water (H2O) solutions. I. Spectral parameters of amino acid residue absorption bands.

Infrared spectra of the amino acid residues in H2O solution have been obtained in the 1800-1400-cm-1 region. It has been established that amino acid residues of arginine, asparagine, glutamine, aspartic and glutamic acids, lysine, tyrosine, histidine, and phenylalanine have intensive absorption in this spectral region. Infrared spectra for a set of model compounds have been measured. On the basis of these data, spectral parameters of amino acid residue absorption bands have been determined.

Amino Acids↗
PubMed1990

Quantitative IR spectrophotometry of peptide compounds in water (H2O) solutions. II. Amide absorption bands of polypeptides and fibrous proteins in alpha-, beta-, and random coil conformations.

Infrared spectra of poly(D,L-alanine), poly(L-glutamic acid), poly(L-lysine), silk fibroin, and tropomyosin have been registered for various conformations of the polypeptide chain. Assuming additivity of the main- and side-chain absorption, spectral parameters of amide I and II absorption bands corresponding to alpha-, beta-, and random coil conformations have been derived. The amide I band parameters for H2O and D2O have been compared.

Amides↗
PubMed1990

Quantitative IR spectrophotometry of peptide compounds in water (H2O) solutions. III. Estimation of the protein secondary structure.

Infrared spectra of 13 globular proteins have been obtained in the 1800-1480-cm-1 region for H2O solutions. A method for estimating protein secondary structure from the ir spectrum has been developed. The method can also be used for estimating polypeptide and fibrous protein conformation. For the globular and fibrous proteins and polypeptides analyzed, the correlation coefficients between the ir and x-ray estimates of ordered helix, disordered helix, ordered beta-structure, disordered beta-structure, turns, and remainder were 0.98, 0.80, 0.99, 0.87, 0.90, and 0.92 respectively.

Animals↗
PubMed1990

A rapid evaluation of tetracycline and its dehydration products by UV derivative spectrophotometry.

This paper described a rapid ultraviolet spectrophotometric assay for simultaneous determination of tetracyclines (TC + ETC) and their anhydroderivatives (ATC + EATC), by using third- or fourth-derivative spectra recorded on samples in ethanol or dioxane. The analytical procedures are based on linear relationships between specific peak-trough values and the relative concentrations of tetracycline and of ATC-EATC, in mixtures containing TC, ATC and EATC. The toxic EATC can be estimated about half of the anhydrotetracyclines concentration values. The determination limit of anhydroderivatives is 0.05%. A simple purity test of the antibiotic is also reported. Accuracy, precision and linearity are discussed. The method is particularly applicable to routine analysis of products containing TC, in bulk and in some pharmaceutical formulations.

Capsules↗
PubMed1978

[Determination of trace elements in dietary fats and emulsifiers by flameless atomic absorption spectrophotometry. 1. Determination of the ionogenically bound heavy metals copper, iron, nickel, zinc, lead and cadmium in dietary fats].

The knowledge of the trace metal contents in dietary fats is of considerable interest from the viewpoints of food hygiene and and storage stability. In the framework of the present paper, it is dealt with the determination of the ionogenically bound heavy metals copper, iron, nickel, zinc, lead and cadmium by means of flameless atomic absorption spectrometry (AAS). Problems related to trace analysis in dietary fats are discussed. Problem-oriented surveys in the form of tables inform about:--analytical conditions of the AAS technique,--metal contents as compared to data with the approved standard method,--contents of the ionogenically bound toxic trace elements cadmium, zinc and lead in samples of various dietary fats currently used in the German Democratic Republic.

Cadmium↗
PubMed1984

[The quantitative determination of protein content in milk by means of ultraviolet spectrophotometry. 2. The suitability of the difference of absorbance at 235 and 280 nm for quantitative milk protein analysis].

The protein content of skimmed milk was determined by measuring the absorbance at 235 and 280 nm after dilution with alkylpolyglycolethersulphate solution. The difference of absorbance A235-A280 shows a high correlation to the values of KJELDAHL nitrogen analysis (r = 0.99). The protein content of casein and milkserum solutions could be determined in the same way. The method has the advantage, that their results are approximately independent of the amino acid composition of proteins, the content of nucleic acids, salts, lactose and non protein nitrogen. Both absorbances are obtainable from one solution. The dependence of the absorbance difference from the age of solution, the age of milk and from the temperature was investigated as well as the influence of preservatives.

Animals↗