Ultraviolet spectrophotometer

Figure 3.24 A typical double-beam recording visible and near-ultraviolet spectrophotometer...

Xue et al. [30] prepared a vaginal suppository formulation containing miconazole nitrate and determined its content by P-matrix ultraviolet spectrophotometry. The production of the suppository was finished with melting by the excipient of glyceryl esters fatty acid of artificial synthesis. Quantitative assay was conducted with a P-matrix ultraviolet spectrophotometer. The suppository was smooth and met the clinical requirement of vaginal disease treatment. The method of assay was accurate. 

The ultraviolet spectrum of pseudoephedrine hydrochloride in ethanol was obtained with a Beckman ACTA CIII ultraviolet spectrophotometer and is shown in Figure 3.4 Pseudoephedrine hydrochloride exhibits absorption maxima at 208, 251, 257, and 264 nm with extinction coefficients of 8300, 161, 201, and 161, respectively. 

In a further modification, Nordin and Bretthauer (N4) assay the residual UDPG by incubation with TNDPN. The final optical density is read at 400 mp, making an ultraviolet spectrophotometer unnecessary. 

For visible region the lenses and prisms of ordinary glass can be used but since glass is opaque to radiation of shorter wave lengths in ultraviolet spectrophotometers they are made of quartz. In infra red spectrophotometers they are made of large crystals of NaCl, CsF or KBr. 

The absorption spectrum data were obtained from measurements made with a Beckman Ultraviolet Spectrophotometer. The formulas employed in making the calculations use the term a, specific absorption coefficient. 

Capillary electrophoresis has been applied by Chen and Gu (281) for simultaneous determination of oxytetracycline, tetracycline, chlortetracycline, and doxycycline residues in bovine milk. Separation was performed on a noncoated capillary column, 57 cm total length with 50 cm effective length, 75 m internal diameter (i.d.) and 375 m outside diameter (o.d.), using a mobile phase containing 10 mM sodium dodecyl sulfate, 50 mM borate, and 50 mM phosphate, pH 8.5. Under these conditions, concentrations below 10 ppb could be determined in milk using an ultraviolet spectrophotometer set at 370 nm. 

FigurB 25-26 Application of the method development triangle to the separation of seven aromatic compounds by HPLC. Column 0.46 x 25 cm Hypersil ODS (C)e on 5-(j.m silica) at ambient temperature ( 22°C). Elution rate was 1.0 mL/min with the following solvents (A) 30 vol% acetonitrile/70 vol% buffer (B) 40% methanol/60% buffer (C) 32% tetrahydrofuran/68% buffer. The aqueous buffer contained 25 mM KH2P04 plus 0.1 g/L NaN3 adjusted to pH 3.5 with HCI. Points D, E, and F are midway between the vertices (D) 15% acetonitrile/20% methanol/65% buffer (E) 15% acetonitrile/16% tetrahydrofuran/69% buffer (F) 20% methanol/16% tetrahydrofuran/64% buffer. Point G at the center of the triangle is an equal blend of A, B, and C with the composition 10% acetonitrile/13% methanol/11% tetrahydro-furan/66% buffer. The negative dip in C between peaks 3 and 1 is associated with the solvent front. Peak identities were tracked with a photodiode array ultraviolet spectrophotometer (1) benzyl alcohol (2) phenol (3) 3, 4 -dimethoxyacetophenone (4) m-dinitrobenzene (5) p-dinitrobenzene ...

Ultraviolet spectrophotometers have been used as gas chromatographic detection systems mainly after condensation of the chromatographic effluent. Systems are capable of detecting naphthalene at 10 8g by scanning every 20 sec from 165 to 220 nm. Use of a monochrometer permits selectivity. Reactions producing chemiluminescence are known. 

New techniques and instruments, such as partition chromatography on paper strips and the photoelectric ultraviolet spectrophotometer, stimulate the development of biochemistry after World War II. New... 

R.C. Hirt and F.T. King, Use of micrometer baly cells with Beckman and Cary ultraviolet spectrophotometers, Analytical Chemistry 24 (1952) 1545-1548. For American Cyanamid Stamford see R. P. Chapman, "Organisation and functions of an analytical and testing group, Chemical Industries 65 (1949) 718-721. 

The assay method of Dalziel is convenient. In a recording ultraviolet spectrophotometer set at 340 nm is placed a 3-mL quartz cuvette containing 2.4 mL of 0.10 M glycine-sodium hydroxide buffer solution, pH 9, 500 pL of a 54 mM solution of ethanol 1n the same buffer, and 100 pL of a 15 nM solution of NAD, also in the same pH 9 buffer. The volume is made up to 3.0 mL, and the assay initiated by the addition of 10 pL of a 1 mg per mL solution of HLADH in 0.10 M "Tris-hydrochloric acid buffer", pH 7.4. The change in optical density at 340 nm 1s monitored at 25°C and the activity calculated from the following equation ... 

Apparatus. Contact angle measurements were made on a Model A-100 Rame-Hart version of the NRL Contact Angle Goniometer. Exposures were carried out in a forced-draft hood with the unfiltered radiation from a General Electric UA-3 medium-pressure mercury lamp. Spectra were recorded on a Perkin-Elmer Model 350 ultraviolet spectrophotometer, a Beckman IR-12 infrared spectrophotometer with a Wilks Model 7 internal reflectance attachment, and an Aminco-Bowman Spec-trofluorometer with a 1P28 photocell. 

Ultraviolet Absorbance (polynuclear hydrocarbons) Make all measurements in 1-cm cells using an ultraviolet spectrophotometer set in the wavelength range of 260 to 350 ran, under the same instrumental conditions. The standard reference absorbance is the absorbance, at 275 nm, of a standard reference solution of naphthalene (National Institute for Standards andTechnology StandardMaterial No. 577, or a solution of equivalent purity) containing a concentration of 7.0 mg/... 

Visible Spectra. These were taken on frozen isopentane solutions in a rectangular quartz cell cooled in liquid nitrogen in a quartz Dewar flask, using a Cary ultraviolet spectrophotometer. 

Visible-Ultraviolet Spectrophotometers. Many commercial spectrophotometers are suitable for the experiments in this text. Often, for instructional purposes, greater insight and more flexibility can be obtained by assembly of an instrument from modular components, available from such sources as Thermo Oriel, Optometries USA, Ocean Optics, or other companies. More commonly an integrated instrument is used to provide greater reliability under use by relatively large numbers of students of varying backgrounds. 

Ultraviolet spectra, notation used in monographs, xv, 308 Ultraviolet spectrophotometers, double-beam, 225 rapid-scanning, 226... 

Ultraviolet spectrophotometers cont.), single-beam, 225 standardisation, 226 Ultraviolet spectrophotometry, 221-232 absorption cells, 226 colorimetry, 228 derivative, 230 difference method, 229 dual-wavelength, 229 identification by, 231 influence of pH, 224 influence of solvent, 224 laws of absorption, 222 quantitative applications, 227 stray-light effects, 224 Ultraviolet-visible detector, 202 multiwavelength, 211 Unicontin, 1011 Unidiarea, 474 Unidone, 356 Uniflu, 557, 893 Unilobin, 709 Unimycin, 846 Uniphyllin, 1011 Uniprofen, 677 Unisom, 576... 

Figure 2-6. Block diagram of the components of a visible and ultraviolet spectrophotometer.

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