Variable UV detector

The MS detector is more sensitive and requires much less sample than UV detection. The LC/MS system is often designed either with an in-line secondary detector or with a splitter system before the interface and a second detector so that additional information can be obtained on the sample. Figure 15.10 compares the chromatographic signals from a variable UV detector and the full-scan total ion chromatogram (TIC) from a MS detector run in series for detection of an adhesive extract. 

A refractive index detector can see both of these types of compounds. A variable UV detector at 206 nm or 195 nm will work for both at reasonable concentrations. I would recommend either a CAD (see Chapter 5) or a mass spectrometer (see Chapter 15) if you need to do gradients or high-sensitivity detection. Both are expensive but give good results. The MS will give you molecular weight data for your separated peaks as well. 

In order to calculate particle size distributions in the adsorption regime and also to determine the relative effects of wavelength on the extinction cross section and imaginary refractive index of the particles, a series of turbidity meas irements were made on the polystyrene standards using a variable wavelength UV detector. More detailed discussions are presented elsewhere (23) > shown here is a brief summary of some of the major results and conclusions. 

Kratos Spectroflow 400 LC pumps ABI Model 783 variable-wavelength ultraviolet (UV) detector... 

Omura et al.21 used a reverse phase high performance liquTcT cEromatographic column, JASCO PACK SV-02-500, for macrolide antibiotics with methanol, M/15 acetate buffer pH 4.9, and acetonitrile (35 60 5) as solvent. A variable wavelength UV detector using the absorption of the individual compounds gave the required sensitivity. Alterations of buffer pH and the composition ratio of the mobile phase gave selectivity for separation of individual macrolide antibiotics. 

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... 

Model RR/066 351 and 352 pumps models 750/16 variable-wavelength UV monitor detector 750/11 variable filter UV detector, MPD 880S multiwave plasma detector, 750/14 mass detector 750/350/06 electrochemical detector refractive index detector HPLC columns column heaters, autosamplers, pre-columns derivatization systems, solvent degassers, preparative HPLC systems... 

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. 

Distinguish between the fixed-wavelength UV detector and the variable-wavelength UV detector in terms of design and use. 

With a modern variable-wavelength or PDA detector, it is safe to use a maximum absorbance of up to 1.0-1.5 absorbance units (AU). A typical UV detector today should have a baseline noise in the order of 10 micro absorbance units (10 AU). Therefore, modern UV detectors should have a dynamic range of 4-5 orders of magnitude. The sample concentration and injection volume can be adjusted to make it possible to quantify the major component and impurities at the 0.05% level in the same chromatographic run without changing detection wavelength, sample concentration, or injection volume. 

High Performance Size Exclusion Chromatography (HPSEC) A Varian Model 5000 liquid chromatograph equipped with a variable wavelength UV detector, two columns in series (PL gel, 300 x7.5 mm, particle size 5/im, porosity of 50 and 500A), was used, THF being the eluent. 

For the majority of analyses of drugs in formulations, variable wavelength UV or diode array UV detectors are used. A typical UV dector has a narrow cell about 1 mm in diameter with a length of 10 mm, giving it an internal volume of about 8. ... 

Answers Selectivity electrochemical detector, variable wavelength UV detector, ELSD,... 

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