Spectrometers UV/VIS

The Au contents were analyzed by ICP. UV-vis diftuse reflectance spectroscopy (DRS) was performed on a Varian Cary IE UV-VIS Spectrometer. X-ray diftfaction patterns were coUected using a Rigaku dififtactometer with Cu radiation. The surface area and the pore size distribution was obtained using nitrogen adsorption. 

UV/VIS absorption spectroscopy, pioneered by Beckman (1941), is one of the oldest and most widely used instrumental techniques, despite being regarded by some analysts as obsolete. Recently there has been a renaissance in UV spectroscopy with many new techniques, instruments and data processing methods [8]. Modem highest specification UV/VIS absorption and fluores-cence/phosphorescence spectrometer instruments extend their wavelength region from the far UV (175 nm) into the NIR region (1100 nm). Small footprint UV/VIS spectrometers (200-1100 nm) are now available. Paul [9] has traced the history of UV/VIS instrumental developments. 

As for miniaturisation, examples are UV/VIS spectrometers using a linearly variable filter rather than a diffraction grating as the wavelength separation device (matchbox size), and double-focusing mass sensors (postage stamp size). 

A UV-Vis spectrometer that reads optical density in individual wells of a microtiter plate. 

The nature and the distribution of different types of Fe species in calcined (C) and steamed (S) samples were investigated by means of UV-vis spectroscopy. UV-vis spectra of Fe species were monitored on UV-vis spectrometer GBS CINTRA 303 equipped with a diffuse reflectance attachment with an integrating sphere coated with BaS04 and BaS04 as a reference. The absorption intensity was expressed using the Schuster-Kubelka-Munk equation. 

Fig. 5.16. A schematic diagram of a single beam instrument, the Genesis 2000 produced by Thermo Spectra. Layout of parts for a UV-Vis spectrometer (with permission of Thermo inc.).

Measurements IR spectra were recorded on a Perkin Elmer Model 1800 spectrometer and UV spectra on a Hitachi Model 330 UV/VIS spectrometer. Samples were spun onto KRS or quartz plates with a film thickness of ca. 1.0 jim. NMR spectra were recorded on a Varlan XL-200. Measurements were done at 23°C. GPC measurements were made on a Toyo Soda Model HLC802UR equipped with four GMHXL-type columns at 40 In THF. The molecular weight (Mw) was determined by polystyrene standards. 

Trypsin inhibition The ability of the various trypsin inhibitors Allium extracts) to prevent tiypsin hydrolysis of BAPNA is measured spectrophotometrically (405 nm, = 9.96 cm pmoT ) [11] at 25°C, with a Jasco UV-Vis spectrometer by time course measurement of AAbs. One trypsin unit hydrolyzes 1.0 pmol of A-ft-benzoyl-DL-arginine /i-nitroanilide (BAPNA) per minnte at pH 7.8 and 25°C and one Trypsin Inhibitor Unit (TIU) will decrease the activity of 2 trypsin units by 50%. 

The supernatant was replaced after 3 days of exposure of cells (tumor and normal) to plant extracts and the cells were washed with PBS, then 500 pL MTT solution (0.25 mg/mL) was added to each well. The cells were washed after 3 h of incubation at 37 C, the formazan crystals formed in hving cells solubilized with 1 mL isopropanol, and the absorbance measured at 570 run with a Jasco UV-Vis spectrometer. Cell viability was expressed as a percentage of control treated with different concentrations of plant extracts. 

A further level of sophistication is illustrated by a submersible UV/vis spectrometer, currently being developed for batch process analysis but potentially also applicable to continuous processes. This instrument also overcomes the sensor-fouling problem by using an auto cleaning system based on pressurised air [76]. 

Figure 1. Comparison of leaching solution with standards using UV-Vis spectrometer. (Leaching test was carried out at 150°C, and 85 psig pressure).

Fortunately, this requires no additional investment (apart from a UV-vis spectrometer that is, however, available anyway in most laboratories), because highly polished salt (KBr or Csl) windows are sufficiently transparent down to 200 nm so that high-quality UV-vis spectra can be obtained with the exact same sample configuration as is used for IR absorption spectroscopy. As in IR spectroscopy, it is often useful to look at difference spectra, but as bands due to different compounds have much more of a tendency to overlap in this case, which may lead to distortions in the difference spectra, one has to be cautious in assigning band maxima from difference spectra. 

Table 6. A program wriUen in FORTH, to drive a UV-VIS spectrometer...

Figure 10.9—Schematic diagram of various infrared spectrometers, a) Single beam model its principle is still used for measurements at a single wavelength b) double beam model c) single beam Fourier transform instrument. Contrary to UV/VIS spectrometers, the sample is placed immediately after the light source. Since photon energy in this range is insufficient to break chemical bonds and degrade the sample, it can be permanently exposed to the full radiation of the source.

Figure IS. Electronic spectra of Santonin 0, 6, 12, 30 and 206 in 90% ethanol obtained against blank 90% ethanol with a UV- VIS spectrometer (Shimadzu UV-1061)...

Figure 18. Electronic spectra of water 30 (a) and Nux vomica 30 (b) in water against blank distilled water obtained with a UV-VIS spectrometer (Beckman DU 640). Both water 30 and Nux vom 30 were freshly prepared in distilled water...

All UV spectral data were obtained by measurement using a conventional UV / vis spectrometer (HP8458) with either aqueous or acetonitrile solutions of the benchmark chemicals. The spectrum of DBP was assumed to be the same as the spectrum of 2,6-di-t-butyl-4-methylphenol. Since DBP differs from this compound by only a para methyl group, the assumption of identical spectra is a good approximation and the absence of absorbance above 300 nm quite certain. Values of were calculated from the absorption at the wavelength centers X (shown in Table 15.1, and the concentration using Equation (2). 

The ultraviolet (UV) absorption spectrum of donepezil in methanol was scanned from 200 to 400 nm, using UV/VIS spectrometer (Shimadzu ultraviolet-visible spectrophotometer 1601 PC). The compound exhibited four maxima at 313, 269, 230, and 209 (Fig. 3.1). Clarke [2] reported the following aqueous acid 230, 271, and 316 nm [2],... 

For slow, bad mixing there will be local acid and base excesses [36], The excess of the acid can promote the redox reaction mentioned above. This acid-catalyzed reaction is much faster than the redox reaction without acid. Thus measurable contents of iodine are formed. These quantities can be detected photometrically using a UV-Vis spectrometer. 

The experimental setup for the PDMS-E microreactor system is shown in Fig. 5. Reactor effluent was analyzed by a Hewlett Packard 1100 HPLC (UV-Vis detector) and an Ocean Optics SD 2000 UV-Vis Spectrometer with fiberoptic flow analysis "Z" cells (FIA Lab). 

All UV/vis spectra were recorded on a Varian Cary 50 Scan spectrophotometer and a PERKIN ELMER UV/vis Spectrometer Lambda 2 (double beam) in solution. Absorption maxima Xmax are given in nm. 0.4 cm quartz cuvettes were used for all measurements. 

Accurate self-consistent thermochemical data for the copper chlorides up to 200°C are required, in order to improve solubility calculations and electrochemical modelling capabilities for Aspen Plus and OLI software. Experimental work has been initiated at the University of Guelph, Canada and UOIT to determine a comprehensive thermochemical database, for solubility limits of OMIT, and aqueous cupric chloride versus chloride concentration and temperature using UV-VIS spectroscopy (Suppiah, 2008). The chloride ion is obtained by adding LiCl OMIT. The conditions of tests are primarily 25-200°C, up to 20 bars. Specialised equipment for this task is needed to reach elevated temperatures and pressures, because cupric chloride is chemically aggressive, and because changes in the solution concentrations must be made precisely. A titanium test cell has been custom made, including a UV-VIS spectrometer with sapphire windows, HPLC pumps and an automated injection system. The data acquired will be combined with past literature data for the cuprous chloride system to develop a self-consistent database for the copper (I) and copper (II) chloride-water systems. 

Turbidity measurements were made with an HP 8451A diode array UV-VIS spectrometer. Since styrene has an absorbance peak of 250 nm, only the data in the region of 300-800 nm was used. 

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