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Spectrophotometers automatic recording

As shown in Figure B2.1, double-beam spectrophotometers automatically record the true absorbance by measuring log(IR/Is), thanks to a double compartment containing two cuvettes, one filled with the solution and one filled with the solvent. Because the two cuvettes are never perfectly identical, the baseline of the instrument is first recorded (with both cuvettes filled with the solvent) and stored. Then, the solvent of the sample cuvette is replaced by the solution, and the true absorption spectrum is recorded. [Pg.26]

Discussion. Potassium nitrate is an example of an inorganic compound which absorbs mainly in the ultraviolet, and can be employed to obtain experience in the use of a manually operated ultraviolet/visible spectrophotometer. Some of the exercise can also be carried out employing an automatic recording spectrophotometer (see Section 17.16). [Pg.708]

The absorbance and the percentage transmission of an approximately 0.1M potassium nitrate solution is measured over the wavelength range 240-360 nm at 5 nm intervals and at smaller intervals in the vicinity of the maxima or minima. Manual spectrophotometers are calibrated to read both absorbance and percentage transmission on the dial settings, whilst the automatic recording double beam spectrophotometers usually use chart paper printed with both scales. The linear conversion chart, Fig. 17.18, is useful for visualising the relationship between these two quantities. [Pg.708]

Procedure. The study can be carried out using either a manually operated single-beam spectrophotometer, or an automatic recording double-beam spectrophotometer. In both cases the wavelengths at which HMR and MR-exhibit absorption maxima are readily obtained from the spectra. [Pg.719]

Nearly all methemoglobln variants exhibit absorption spectra that are different from that of normal ferrlhemoglobln The absorption spectra are determined after the hemolysate Is dialyzed overnight at 4 0 against an 0 1 M phosphate buffer, pH 6 4 or 7 1, using an automatic recording spectrophotometer ... [Pg.34]

The spectrophotometer which gives the whole spectral composition of a colour has every advantage other than simplicity. The visual spectrophotometer is the least sophisticated instrument but is tedious to operate and has, therefore, been replaced by automatic recording systems for industrial use. A description of the comparatively primitive visual apparatus is, however, justified because it affords an illustration of the principles involved. [Pg.639]

Chlorophyll. A spectrophotometrie procedure described by Vernon (14) was followed except the thawed samples were homogenized in an cold environment. A Varlan DMS 100 UV Visible Spectrophotometer with automatic recorder was used for absorbance readings at the different wavelengths of 536, 645, 662 and 666 nm. [Pg.228]

Fig. 11. Comparison of absorption spectra of alkaline solutions of proteins and of mixtures of tyrosine and tryptophan. The curves, obtained with an automatic recording spectrophotometer, are displaced along the vertical axis to avoid overlapping. Fig. 11. Comparison of absorption spectra of alkaline solutions of proteins and of mixtures of tyrosine and tryptophan. The curves, obtained with an automatic recording spectrophotometer, are displaced along the vertical axis to avoid overlapping.
Determinations of dehydrogenase activities by the O.t. are now conveniently performed in an automatic recording spectrophotometer, so that the change in absorbance at 340 nm is monitored continuously with time, e.g. the activity of malate dehydrogenase is measured from the rate of increase of absorbance at 340 nm due to the production of NADH in the reaction NAD + Malate -> Oxaloacetate + NADH + H. ... [Pg.474]

The acquisition of UV-vis absorption spectra for use in the elucidation of organic molecular structure is now carried out with instmmentation that is typically an automatic-recording photoelectric spectrophotometer. The optical components of one of the classic spectrophotometers is given in Figure 8.43. This system is typical of a high-quality double-beam double-monochromator instrument. The instrument consists of a number of components the radiation source, monochromator, sample compartment, detector, amplifier, and recorder. [Pg.604]

Kenyon et al. devised the Scanalyzer, a Cary spectrophotometer wedded to a gradient elution chromatographic column. The Scanalyzer automatically records hundreds of ultraviolet spectra of the chromatographic effluents in unattended overnight operation. Stark et al. described a similar device. Kuchler et al. modified a Beckman DK-1 to provide automatic repetitive scanning of absorption spectra and described its application to steroid hormone analysis and to studies of reaction kinetics. [Pg.261]

Compounds 1,2,3,5,10,11,12,13,14 were dissolved in EPIP (diethyl ether, petroleum ether, isopropanol 5 5 2)whereas compounds 4,6,7,8,9,15 were dissolved in THF-DE (tetrahydrofurane, diethyl ether 1 1). These solvent mixtures can be frozen as glassy samples at 77 K. The absorption spectra were recorded on a standard spectrophotometer SF-10 or Beckman-5270. The measurements of fluorescence excitation and emission spectra were made with the aid of a spectrofluorometer SLM-4800 with automatic correction of spectral response. Fluorescence lifetimes were measured with the aid of a pulse fluorometer PRA-3000. Magnetic circular dichroism (MCD) measurements were carried out in a 8 kG magnetic field using a JASCO J-20 circular dichrometer. Triplet state formation was observed for investigated compounds at the experimental set up, whose detailed description can be found in our paper (27). The optical experiments were carried out with a porphyrin concentration of 4.10- - 4.10 mol.l". In NMR investigations (Bruker WM-360) we used higher concentrations ( 5.10" raol.l ) and dried solvents (CDCl, C 2 and toluene-d0). [Pg.76]

Six tablets were subjected to. dissolution using the USP dissolution apparatus (Vanderkamp 600, Van-Kel Ind., NJ, USA) in 500 ml buffer pH 1.2 (the first hour) and 650 ml buffer pH 6.8 (1-14 h), maintained at 37°C and rotated with paddles at 50 rev min-1 (first hour) and 130 rev min-1 (1-14 h). The dissolution apparatus was connected to a UV-visible spectrophotometer (Uvikon 810, Roxche Bioelectronique Kontron, Marseille) and a computer (VAX 780 Digital). The absorbance of the dissolution medium at 275 nm was recorded automatically at intervals (1, 2, 4, 5, 8, 10, 12 and 14 h). The percentage of the drug released was calculated and the corresponding release profiles were obtained. [Pg.45]


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Spectrophotometers

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