Detectors, UV-visible

A stainless steel column (4.6 mm internal diameter by 250 mm length) packed with 7 micron Zorbax ODS (Dupont) was equilibrated with 82 % Acetonitrile in water at a flow rate of 2.0 ml/min. provided by a Spectra Physics Model 87(X) pump and controller. The effluent was monitored at 230 nm using either a Tracor UV-Visible detector Model 970A or a Jasco Uvidec UV detector Model 1(X)-V. Peaks were recorded and calculated on a SpectraPhysics recording integrator. Model 4200 or Model 4270. Samples of 0.5 mg/ml in toluene were applied to the column automatically with a Micromeritics Autosampler Model 725 equipped with a 10 pi loop. 

Torsi, G., Chiavari, G., Laghi, C., and Asmudsdottir, A., Responses of different UV-visible detectors in high-performance liquid chromatographic measurements when the absolute number of moles of an analyte is measured, /. Chromatogr., 518, 135, 1990. 

Esquivel, J. B., Wavelength accuracy testing of UV-visible detectors in liquid chromatography, Chromatogmphia, 26, 321, 1988. 

Both fixed and variable wavelength uv/visible detectors are available. The variable types use a deuterium and/or a tungsten filament lamp as the radiation source and can operate between about 190-700 nm. They will have a number of absorbance ranges (ranges are given... 

There are several types of RI detector, all of which monitor the difference between a reference stream of mobile phase and the column effluent. Any solute whose presence alters the refractive index of the pure solvent will be detected, but sensitivity is directly proportional to the difference between the refractive index of the solute and that of the solvent. At best they are two orders of magnitude less sensitive than UV/visible detectors. All RI detectors are highly temperature-sensitive, and some designs incorporate heat exchangers between column and detector to optimize performance. They cannot be used for gradient elution because of the difficulty in matching the refractive indices of reference and sample streams. 

Series 10 chromatography LC-95 variable wavelength UV/visible detector, LC-90 variable wavelength UV detector, LC-135 and L-235 diode array detectors, LC 1-100 computing integrator, 1SS-100 intelligent amjj in s stjm, Series 410 LC pump... 

Chromo-A-Scope comprising UV visible detector and data processing system only Barspec Ltd Barspec Ltd... 

Specifications, Agilent 1100 Series UV-Visible Detectors, Agilent Technologies, 5980-1532e, 2001. 

A typical HPLC system set to a flow rate of 1 ml/min, indicating a column back pressure of 1265 psi and connected to a UV/visible detector which is set to monitor the column effluent at 260 nm. 

This area of analytical chemistry includes a great number of instruments that range from colour comparators and other visual comparison devices to automated spectrophotometers that can carry out multicomponent analysis. Liquid chromatography and capillary electrophoresis have accelerated the development of improved UV/Visible detectors, which are at the origin of the current mode of acquiring chromatograms, accompanied by the possibility of identification and quantification of compounds. 

Improved separation of natural oil TGs using short columns packed with 3-//m alkyl bonded-phase particles was reported by Dong and DiCesare (88). The HPLC columns used were HS-3 high-speed columns packed with 3-/um C18 bonded-phase particle (100 X 4.6-mm ID) with a column void volume of ca. 0.8 ml and efficiencies in the range of 13,000-15,000 theoretical plates (measured under optimized conditions) and HS5 C,8 columns (125 X 4.6-mm ID packed with 5-yttm particles). Two detectors were used a modified refractive index detector having an 8-/rl flow cell and 0.007-in. ID inlet tubing and a variable-wavelength UV/visible detector. 

Figure 2. Flow Sheet of the HPLC Unit for Rapid Protein Analysis. A binary gradient system with gradient controller, Model 21500 pumps,Model 2152 controller, Pharmacia, Piscataway, NJ, U.S.A. (A), Variable wavelength UV-Visible detector, Model LC 95, Perkin Elmer, Norwalk, CT, U.S.A (B), Constant temperature circulating bath, Model DL-8 Haake Buchler, Saddlebrook, NJ, USA (C), Heat exchangers (D), Sampling valve,...

With a low-dose dmg product, the absorptivity of dmg substance is a key property. If it is intense, conventional detection methodology may be viable, typically with a UV-Visible detector using HPLC instrumentation. However, LC/MS may be another option when increased sensitivity is needed.23... 

Zavitsanos, P., and Goetz, H. (1991). The practical application of diode array UV-visible detectors to high-performance liquid chromatography analysis of peptides and proteins. In High-Performance Liquid Chromatography of Peptides and Proteins Separation, Analysis,... 

From the Requirements Specifications, the nser can derive the instrnment type and its minimal Functional Specifications. For example, if an instrument is schednled to rnn overnight, the number of samples should be specified so that the system can inject antomatically. The UV/visible detector s baseline noise specification can be determined from the specified detection and quantitation limit of an HPLC analysis. The required data evaluation will determine the demands on the evaluation software. 

Operating devices may become miscalibrated after a while (e.g., the temperature accuracy of a gas chromatography [GC] column oven or the wavelength accuracy of a UV/visible detector s optical unit). This can have an impact on the performance of an instrument. Therefore, a calibration program should be in place to recalibrate critical items of an instrument. 

Noise and drift are measured in static (dry detector cell) and in dynamic mode at different wavelengths, e.g., 200, 254, and 390 nm. The change in the absorbance as a function of flow rate at the same wavelengths reflects flow sensitivity. Noise is expressed in AU/cm, drift in AU/hr, and flow sensitivity in ALf min/mL. Some equipment units can automatically perform calibration for accuracy. For example, some HPLC-UV/Visible detectors include holmium oxide filters for measurement and calibration of the wavelength accuracy. 

Figure 8. Direct photolysis of 4-chlorophenol. Hydroquinone and 4-chloroca-techol were analyzed by GC-MS p-benzoquinone was analyzed by HPLC with UV-visible detector at a wavelength of254 nm. Experimental conditions 4-chlo-rophenol = 10 3 M, pH = 4.0, I = 5 X 10 2 M NaN03, oxygen atmosphere, and temperature = 25 °C.

UV/visible detector) is on-line (actually measuring the analytes whilst they are still in the analytical capillary). 

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