High-pressure liquid chromatographic detector

Assay of Endogenous NE. Endogenous NE release from the guinea pig vas deferens was measured by means of a high pressure-liquid chromatograph with an ODS column and an electrochemical detector as described previously (16). 

Sugars were estimated by using a Beckman 344 gradient high-pressure liquid chromatograph with an Altex 156 refractive index detector and a Spherogel 7.5% carbohydrate column with a flow rate of 0.5 ml/min in the mobile phase of water at 80 C. The sugar samples were appropriately diluted before injection. 

Because N-nitroso compounds can have such a wide variety of physical and chemical properties, and because they can be formed from a wide variety of precursors. analysis at the trace level is difficult. The most widely used technique is the use of a nitrosamine specific detector, called a TEA, which can be interfaced to either a gas chromatograph (GC) or a high pressure liquid chromatograph (HPLC) (31,32). General screening procedures which have been designed to detect all N-nitroso compounds have been developed (33,34). Structural confirmation of N-nitroso compounds is gen-... 

It is for these reasons that a recommendation is made to avoid, wherever possible, concentration and cleanup steps that involve "column chromatography" of this nature, that is, chromatography where an in-line detector is not involved. This distinction is made to eliminate any implied criticism of instrumented high pressure liquid chromatographic systems which have not to date been used extensively for this particular purpose. 

A schematic diagram of a typical high-pressure liquid chromatograph is shown in Figure 3.12. The basic components are a solvent reservoir, high-pressure pump, packed column, detector, and recorder. A computer is used to control the process and to collect and analyze data. The similarities between a gas chromatograph and an HPLC are obvious. The tank of carrier gas in GC is replaced by the solvent reservoir and high-pressure pump in HPLC. 

Chromatographic System - Typically, a high-pressure liquid chromatograph, operated at room temperature, is fitted with a 30-cm x 4-mm stainless steel column packed with chromatographic column packing L3. An ultraviolet detector that monitors absorption at the 254-nm wavelength is used. 

THIS SYSTEM IS COMPOSED OF XXX SUBPROGRAMS WHICH ACQUIRE DATA FROM A DUAL BEAM MULTIPLE WAVELENGTH DETECTOR IN A CONFIGURATION FOR USE WITH A HIGH PRESSURE LIQUID CHROMATOGRAPH. 

Chromatographic System Use a suitable high-pressure liquid chromatograph equipped with a detector measuring at 210 nm and a 250- x 4.6-mm column packed with octadecyl silanized silica (10-pm Partisil ODS-3, or equivalent) and operated under isocratic conditions at 40°. The flow rate of the Mobile Phase is about 2 mL/min. 

Chandler and McNair (Hercules Inc.) [278] discussed the requirements for the basic parts of a high pressure liquid chromatographic system. These include a solvent reservoir, pump, injection system, column detector and recorder. They listed some of the different models available and described their major features. The developments in HPLC apparatus have also been reviewed by Martin and Guiochon [279] and the basic requirements also described by Bombaugh (Chromatec Inc.) [280]. The pumps and injectors available have been reviewed [281]. Some detectors currently used in HPLC have also been reviewed [282]. 

A widely used photometer used as a high-pressure liquid chromatographic (HPLC) detector uses the intense 254-nm resonance line produced by a mercury arc lamp (see Chapter 6). Others employ a miniature hollow cathode lamp as a very-narrow-wavelength intense source. For example, a zinc hollow cathode lamp gives a line at 214nm that is adequately close to the maximum wavelength of peptide bond absorption (206 nm) so that it can be used to measure peptides and proteins. Details on the hollow cathode lamp are found in the section on Atomic Absorption Spectrophotometry. The hollow cathode lamp also has a long, useful Hfetime if a lower-current, nonpulsed power supply is used. j... 

The detector is another of the critical components of a high pressure liquid chromatograph, and in fact, the practical application of liquid chromatography had to await a good detector system. Many types of detectors are now on the market. The four most common, the ultraviolet absorption (uv), fluorescence, refractive index (RI), and electrochemical (EC) detectors, will be discussed as well as the newer light scattering mass sensitive detector. 

Analytical Methods. In 1980 where carbaryl/captan were applied in combination, a simultaneous quantitative analysis for the mixture was developed using a Water s system (model M-45 pump, 6K injector and Model 450 variable wavelength detector) high pressure liquid chromatograph system and Hewlett-Packard 3380-A integrator. A 25 cm... 

In specific circumstances where there happen to be no interferences, the simple voltammetric response of an electrode can be a Very convenient monitor in process streams and effluents. Such applications, however, have little generality. An application of electrochemical celts of increasing importance is as a detector for high-pressure liquid chromatographs. Here, the chromatographic column should have already separated the components of the mixture and the ability to record complete i-E responses quite rapidly can be used to identify components and to confirm complete separation (does the curve change through a peak ),... 

Fig. 2.3. Chromatogram of a solution containing aisenite, arsenate, methylarsonic acid and dimethylarsinic acid (each 100 mg As 1 ) recorded with a differential refractive index detector and an ARL 34000 simultaneous inductively coupled argon plasma atomic emission spectrometer as the arsenic-specifier detector [Hamilton PRP-1 column, hexadecyltrimethylammonium bromide (HTAB) as ion-pairing reagent flow rate 1.5 ml min 0.1 ml injected Waters Associates high pressure liquid chromatograph integration time on ICP 5 sec. As 189.0 nm]. Redrawn from Marine Chemistry [10] by permission of Elsevier Science Publishers and the authors.

Element-specific detectors can and have been used in conjunction with gas chromatographs, with ion chromatographs, and with high pressure liquid chromatographs to great advantage. Most of the element-... 

Williams et al. used a high performance liquid chromatographic assay method for dipyridamole monitoring in plasma [71]. The HPLC system uses a Waters model 6000 A solvent delivery pump equipped with a U6K injector, a pBondapak C 9 column (30 cm x 39 mm 10 pm), and a Model 440 absorbance detector. The signal from the detector was quantified using a Shimadzu data processor and an Omni-Scribe recorder. A mobile phase flow rate of 1.5 mL/min was produced by a pressure of approximately 102 atm (1500 p.s.i.). The mobile phase was 50 50 mixture of acetonitrile and 0.01 M sodium phosphate in water (adjusted to pH 7). The absorbance reading of dipyridamole in methanol was made at 280 nm. 

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