UV spectrophotometers

For detection and quantitative determination a differential refractometer can generally be used. The detection limit is about 10 pg/ml. If only alkylphenol ether carboxylates are to be determined, a UV spectrophotometer can also be used whereby the detection limit is lowered to about 0.1 pg/ml. 

Figure 2.4. Graph of the linear regression line and data points (left), and the residuals (right). The fifty-fold magnification of the right panel is indicated the digital resolution 1 mAU of a typical UV-spectrophotometer is illustrated by the steps.

Diode-array UV-spectrophotometer with powerful software (although the spectra overlapped in part, quantitation could be effected in the... 

Stability of 2,3,7,8-Tetrachlorodibenzo- >-dioxin Towards Air Oxidation Under Simulated Conditions. Air was bubbled through two borosilicate glass gas absorption bottles equipped with fritted glass bubblers. The first bottle contained 1-octanol for presaturation of the air, and the second bottle contained 1-octanol solutions of the dioxin treated as follows (1) octanol only, (2) octanol mixed with 74-105ju, glass beads to increase the surface area, and (3) octanol mixed with magnesium oxide to simulate a basic soil. The original solution and the sample solutions were scanned with a UV spectrophotometer at various time intervals for 4 days to determine the stability of 2,3,7,8-tetrachlorodibenzo-p-dioxin. 

The apparatus employed for chromatographing particle suspensions in this laboratory has been reported in detail elsewhere (ll). A sample loop of approximately O.U ml was used. The detector was a Pharmacia UV-spectrophotometer with a cell of 1 cm path length and an operating wavelength of either 25, 280 or 350 nm. The volume counter had a capacity of 1 ml. 

Heller and Tabibian (13) noted that errors, due to laterally scattered light and the corona effect, as large as to cause a 30 reduction in measured turbidity, may result if instruments which are perfectly suitable for ordinary absorption measurements are used for turbidity measurements without proper modifications. To evaluate the performance of our turbidity detector, particle suspensions of various concentrations of several polystyrene latex standards were prepared. Their extinction coefficients were measured using both a bench-top UV spectrophotometer (Beckman, Model 25) and the online detector (Pharmacia). 

UV spectroscopy can be used to detect low levels of organic corrosion inhibitors in produced water. An analytic method has been developed using a diode array UV spectrophotometer [630]. 

Parallel methods using scanning 96/384-well plate UV spectrophotometers are inherently faster [292]. They will become 50-fold faster with the imminent introduction of diode-array plate readers. 

A known quantity of sample is added to a known volume of a universal buffer solution of sufficient capacity and of known pH. The amount of sample must be sufficient to cause precipitation to occur in the formed saturated solution. After waiting for a period of time to allow the saturated solution to reach the desired steady state, the solution is filtered to remove the solid and obtain a clear solution, whose spectrum is then taken by the UV spectrophotometer. Mathematical treatment of the spectral data yields the area-under-the-curve of the filtered sample solution, AUQ. 

A reference solution is prepared by a dilution method. A known quantity of sample is dissolved in a known volume of the system buffer of known pH the amount of sample is X times less than in the above case in order to avoid precipitation in the formed solution. The spectrum is immediately taken by the UV spectrophotometer, to take advantage of the possibility that solution may be supersaturated (i.e., solid should have precipitated, but because not enough time was allowed for the solid to precipitate, the solution was temporarily clear and free of solid). Mathematical treatment of the spectral data yields the AUC of the reference sample solution, AUQ . The ratio R = AUCS/AUCS is used to automatically recognize the right conditions for solubility determination when the reference has no precipitate, and the sample solution is saturated with precipitate. Under these conditions, solubility is determined from the expression... 

The ultraviolet spectrum of bromocriptine mesilate was recorded on a Philips 1700 uv spectrophotometer in 0.1 M me-thanolic methanesulphonic acid solution. It is given in fig. 

The ultraviolet spectrum of triprolidine hydrochloride in 0.1N HC1 was taken with a Beckman ACTA CIII UV spectrophotometer and is shown in Figure 3.4 Table III gives the UV data for triprolidine hydrochloride in various solvents. 

Diagnosis UDPG consumption Specific and reliable for diagnostic purposes UV Spectrophotometer (A2)... 

Diagnosis UDPGal formation Modification of 2., more specific requires UDPGal-4-epimerase UV Spectrophotometer (M4)... 

Detection of heterozygote UDPG consumption Measures rate of reaction can combine with estimation of UDPGal formation good discrimination heterozygotes from normals UV Spectrophotometer (B17)... 

Monitoring of treatment UDPG consumption (no Gal-l-P added) Resembles 2. estimates Gal-l-P present in erythrocytes UV Spectrophotometer (Kll)... 

A light source used frequently for ultraviolet absorption studies is the deuterium lamp. If an instrument is meant strictly for ultraviolet work, then the deuterium lamp is the only light source present and the instrument is called a UV spectrophotometer. Often, both a tungsten filament lamp and a deuterium lamp are present and are individually selectable. Also, instead of having two independently selectable... 

Zero the UV spectrophotometer with the blank at 220 nm. Measure all solutions (calibration standards, unknowns, and control) as follows using quartz cuvettes. Measure the absorbances at... 

The ultraviolet (UV) absorption HPLC detector is basically a UV spectrophotometer that measures a flowing solution rather than a static solution. It has a light source, a wavelength selector, and a phototube like an ordinary spectrophotometer. The cuvette is a flow cell, through which the column effluent flows. As the mobile phase elutes, the chromatogram traces a line at zero absorbance, but when a mixture... 

FIGURE 13.8 The HPLC variable-wavelength UV detector—a UV spectrophotometer with a flow cell. A peak appears when a mixture component that absorbs the set wavelength elutes from the column. 

Transfer a portion of the chloroform layer to a 1 cm absorption cell and determine the absorbance at 470 nm in a UV-spectrophotometer, employing the solvent (chloroform) as a blank or reference, and... 

Measure the absorbance at 465 nm in a UV spectrophotometer against a 3-methyl butanol blank,... 

Despite the conflicting evidence, Heyes and Trahar (1984) believe there is sufficient evidence to confirm the presence of sulphur on mineral surface. They leached the surface of floated pyrrhotite from a typical test with cyclohexane and have examined the leach solution in a UV spectrophotometer. They found that sulphur could be extracted from the surface of pyrrhotite, which had been floated in the absence of collector. As can be seen from Fig. 2.26, the spectrum from the leached pyrrhotite was compared with the spectrum of sulphur dissolved in cyclohexane indicating that sulphur was present at the siuface. Kelebek and Smith (1989) used UV spectrophotometer to determine sulphur in the ethanol extract from the surface of floated galena and chalcopyrite showing that the amount of sulphur on the minerals can be correlated with their flotation rate which was found to be first order within the critical surface tension range. 

The entire receptor compartment was sampled and the dmg concentration was assayed at 248 nm using a UV spectrophotometer (Shimadzu, Japan). 

In reviews on the use of in situ sensors" or optical sensor systems" for bioprocesses, UV-vis does not play a major role. An example for the application of at-line UV-vis spectroscopy was presented by Noui et al. The selective flocculation processes of Saccharomyces cerevisiae homogenates were followed with a newly developed direct UV spectrophotometer. The results from a PLS regression model were in good agreement with those from off-line chemical assays. 

L. Noui, J. Hill, P.J. Keay, et al.. Development of a high resolution UV spectrophotometer for at-line monitoring of bioprocesses, Chem. Eng. Proc., 41, 107-114 (2002). 

Ultraviolet spectra were recorded on a Perkin-Elmer 402 UV spectrophotometer or Hitachi 150-20 UV spectrophotometer and Infrared spectra on a Perkin-Ehner 710B or a Perkin-Elmer 1600 series FTIR spectrometer. 

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