Visible spectrophotometer

Photolytic reactions were studied using Shimadzu UV-Visible spectrophotometer with Spectrum and Quantitative Mode. The pH measurements were performed by TOA Electronics pH meter at 20 °C. 

For ultraviolet/visible spectrophotometers the gratings employed have between 10000 and 30000 lines cm-1. This very fine ruling means that the value of d in equation (14) is small and produces high dispersion between wavelengths in the first-order spectrum. Only a single grating is required to cover the region between 200 and 900 nm. 

Double-beam spectrophotometers. Most modern general-purpose ultraviolet/ visible spectrophotometers are double-beam instruments which cover the range between about 200 and 800 nm by a continuous automatic scanning process producing the spectrum as a pen trace on calibrated chart paper. 

EXPERIMENTAL DETERMINATIONS WITH ULTRAVIOLET/VISIBLE SPECTROPHOTOMETERS... 

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). 

UV visible spectrophotometer. A1 (N03)3.9H20 monomer was prepared in same manner. In case of synthesis of dimer complex, 2 equivalent of the Co(salen) was taken with respect to AlX3.nH20. 

Ninhydrin Assays. Ninhydrin tests were performed using a modified procedme of Taylor et al. " APS Silica (10-75 mg) of various loadings (0.857, 0.571, and 0.343 mmol NH2/g Silica) was added to phosphate buffer (5 mL, 100 mM, pH 6.5), and 1 mL of a 5% w/v solution of ninhydrin in ethanol was added to the sluny. After stirring for an hour in a boiling water bath, the mixture was allowed to cool slowly to room temperature. The silica was then filtered and washed three times with 70°C distilled water. The filtrate was collected, added to a volumetric flask, diluted to 100 mL, and the absorbance of this solution at 565 mu was measured using a UV-visible spectrophotometer. The reference solution was prepared as above with unmodified amine-free silica. Calibration standards were prepared with aliquots of a 1 mg/mL solution of APS in ethanol. 

The ultraviolet-visible spectrophotometer is the most widely used detector for HPLC. The basis of UV-VIS detection is the difference in the absorbance of light by the analyte and the solvent. A number of functional groups absorb... 

Many different detectors are used in RPLC, including ultraviolet-visible spectrophotometers (UV-VIS), refractive index (RI) detectors, electrochemical (EC) detectors, evaporative light-scattering detectors, fluorimeters, and... 

Detection is also frequently a key issue in polymer analysis, so much so that a section below is devoted to detectors. Only two detectors, the ultra-violet-visible spectrophotometer (UV-VIS) and the differential refractive index (DRI), are commonly in use as concentration-sensitive detectors in GPC. Many of the common polymer solvents absorb in the UV, so UV detection is the exception rather than the rule. Refractive index detectors have improved markedly in the last decade, but the limit of detection remains a common problem. Also, it is quite common that one component may have a positive RI response, while a second has a zero or negative response. This can be particularly problematic in co-polymer analysis. Although such problems can often be solved by changing or blending solvents, a third detector, the evaporative light-scattering detector, has found some favor. 

The output signal of concentration-sensitive detectors is proportional to the concentration or weight of polymer in the column eluent. Examples of this type include the differential refractometer and the ultraviolet-visible spectrophotometer. Infrared and fluorescence detectors are used infrequently. None of the detectors described above is truly universal i.e., the response of these detectors varies with the chemical species, and, in case of the DRI, response is also a function of the chromatographic eluent.156 Recently, an... 

The ultraviolet absorption spectrum of miconazole nitrate in methanol (0.0104%) shown in Fig. 3 was recorded using a Shimadzu Ultraviolet-visible spectrophotometer 1601 PC. The compound exhibited three maxima at 264, 272, and 280 nm. Clarke reported the following Methanol 264 and 272 nm = 17a), 282 nm [2]. 

The UV spectrum of valproic acid (0.1% solution) in methanol is shown in Fig. 3, was recorded using a Shimadzu UV Visible Spectrophotometer 160 PC. The acid form of the drug has one maximum at 212 nm. In contrast, the sodium salt of the compound has no UV maximum between 800 and 205 nm, this in agreement with previous results reported by Chang [5]. 

A Cary 500 Scan UV-visible spectrophotometer was used to evaluate the amount of ibuprofen adsorbed and released by the MCM-41-IBU. 

Pigments from cells or thylakoid membranes were extracted in 80 % acetone and debris was removed by centrifugation at 10,000 g for 5 min. The absorbance of the supernatant at 652 nm was measured by a Shimadzu UV-visible spectrophotometer. The chlorophyll (a and b) concentration of the samples was determined according to Amon [1949], with equations corrected as in Melis et al. [2000],... 

Some commercially available instruments, in addition to visible spectrophotometers, can also perform measurements in the UV and near IR regions of the spectrum. 

Suppliers of visible spectrophotometers are reviewed in Table 1.1. Spectroscopic methods are applicable to the determination of phenols, chlorophenols, amines, mixtures of organics, boron, halogens, total nitrogen and total phosphorus in soils, cationic surfactants, carbohydrates, total nitrogen, phosphorus and sulphur in non-saline sediments, boron, total organic carbon, total sulphur and arsenic in saline sediments, cationic surfactants, adenosine triphosphate and total organic carbon in sludges. 

Lambda 2 Ultraviolet-visible double-beam spectrophotometer Lambda 3 Ultraviolet-visible double-beam spectrophotometer Lambda 5 and Lambda 7 Ultraviolet visible spectrophotometers Lambda 9 Ultraviolet visible—near infrared spectrophotometer Lambda Array 3430 Spectrophotometer... 

Using one of your standards and the Spectronic 20, or other single-beam visible spectrophotometer, obtain an absorption (or transmittance) spectrum of the Fe-o-phenanthroline complex ion (instructor will demonstrate use of instrument). Determine the wavelength of maximum absorbance from the spectrum and use this wavelength to obtain absorbance readings of all the solutions. (Use the blank for the 100% transmittance setting.)... 

Nitrite is determined by diazo-coupling with sulfanilamide and NEDA (see below for full name), forming a reddish color that can be determined with a visible spectrophotometer. 

The initial mixture and each time point are then assayed for doxorubicin and lipid. Lipid concentrations can be quantified by the phosphate assay (see above) or by liquid scintillation counting of an appropriate radiolabel. Doxorubicin is quantified by an absorbance assay (see below). The percent uptake at any time point (e.g., t = 30 minutes) is determined by %-uptake = [(D/L), =30minutes] x 100/[(D/L) inuiai]. Doxorubicin can be assayed by both a fluorescence assay and an absorbance assay, but we find the latter to be more accurate. The standard curve consists of four to five cuvettes containing 0 to 150 nmol doxorubicin in a volume of 0.1 mL samples to be assayed are of the same volume. To each tube is added 0.9 mL of 1% (v/v) Triton X-100 (in water) solution. For saturated lipid systems such as DSPC/Chol, the tubes should be heated in a boiling water bath for 10 to 15 seconds, until the detergent turns cloudy. Samples are allowed to cool, and absorbance is read at 480 nm on a UV/Visible spectrophotometer. 

Figure 5 Temperature-dependent turbidimetry profiles for solutions of poly(Lys-25) at pH 7.0 and 11.0. These measurements were performed on a Pharmacia Biotechnology Ultrospec 3000 UV/visible spectrophotometer equipped with a programmable Peltier cell and temperature control unit.

Experimental methods for determining 0 are well documented (2). These experiments are conveniently carried out and require only a method of producing reasonably narrow-bandwidth radiation, a method of measuring the flux of that radiation per unit area, and a UV-visible spectrophotometer. The quantum efficiency of typical diazonaphthoquinone sensitizers of the type that are used in the formulation of positive photoresists ranges from 0.2 to 0.3, whereas the quantum efficiency of the bis-arylazide sensitizers used in the formulation of two-component negative photoresists, ranges from 0.5 to 1.0. 

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