High pressure liquid chromatography detector

Figure 11.21 A design of electrochemical cell for a high-pressure liquid chromatography detector.

Steichen, J. C., A dual-purpose absorbance-fluorescence detector for high-pressure liquid chromatography, /. Chromatogr., 104, 39, 1975. 

Francesconi, K.A., P. Micks, R.A. Stockton, and K.J. Irgolic. 1985. Quantitative determination of arsenobe-taine, the major water-soluble arsenical in three species of crab, using high pressure liquid chromatography and an inductively coupled argon plasma emission spectrometer as the arsenic-specific detector. Chemosphere 14 1443-1453. 

Infrared spectra were recorded on a Perkin Elmer Model 567 Spectrophotometer. Ultraviolet spectra were obtained on a Cary 1756 Spectrophotometer. Gas chromatograms were recorded on a Tracor Model 220 with electron capture detector. High pressure liquid chromatography studies were conducted with a Waters Model ALC-200 with ultraviolet and refractive index detectors. 

This chapter presents an overview of current trends in high-pressure liquid chromatography (HPLC) instrumentation focusing on recent advances and features relevant to pharmaceutical analysis. Operating principles of HPLC modules (pump, detectors, autosampler) are discussed with future trends. 

High pressure liquid chromatography (HPLC) was used for the quantitative measurement of quinones and hydroquinones in the cultures. 20 pi of supernatant were injected in a Merck-Hitachi HPLC system 655A-12 equipped with a 4.6 x 250 mm Nucleosil C18 column (5 pm, RP 18). The system was run at a flow rate of 1 ml min-1 with a methanol/water gradient (10 to 20% methanol in 15 min, then 20 to 100% methanol in 5 min). The UV detector was operated at 281 nm or 275 nm to follow the reduction of quinones 13 and 14, respectively (37). 

For the analyses discussed here, we have used Gas Chromatography-Thermal Energy Analysis (GC-TEA ) and/or High Pressure Liquid Chromatography-Thermal Energy Analysis (HPLC-TEA). The TEA has been used as the detector... 

The application of atomic spectroscopic instruments as element-specific detectors in chromatography has been reviewed by van Loon More recently, Krull has extensively reviewed their use in high pressure liquid chromatography (HPLC). Atomic spectrometry has found wide acceptance in the field of liquid chromatography because, in most cases, the fractions can be directly analysed after elution from the column. However, it is possible to use the technique for the analysis of solid samples without first dissolving the matrix. This is particularly useful after electrophoresis, where the fractions are fixed either in a gel or on paper. Kamel et al. have shown that it is possible to cut the appropriate sections and insert them into the carbon furnace for analysis. The disadvantage of this approach is that the precision is usually poorer (about 10%) and it is difficult to calibrate the instrument. Nevertheless, this approach is very useful if it is used for qualitative speciation. 

The apparatus used for high pressure liquid chromatography was by Pye-Unicam (Cambridge), HJ-—4oll equipped with a FU-4o2o UV detector. The co-... 

Apart from the above reasons derivatisation is also required in the analyses of many of the newer pesticides which have one or more functional groups which need protection in order to facilitate GC work. Also the increased use of high pressure liquid chromatography (HPLC) necessitates pre- or post-column derivatisation since the choice of HPLC detectors is limited compared with GC. 

Fig. 14.8 A thin-layer cell for use as a high pressure liquid chromatography electrochemical detector (courtesy of Bioanalytical Systems).

By high-pressure liquid chromatography, using a UV absorbance detector, cyclohexaselenium has been detected in various selenium solutions in equilibrium with Se7 and Se8 (see also Section II,D) (14). Cyclohexaselenium is also formed by thermal decomposition of Se7 in inert organic solvents like CS2 according to the equation... 

High Pressure Liquid Chromatography This method is of value for dealing with compounds which are thermally labile and therefore are not suitable for gas Chromatography. However, reported methods have usually described the analysis of specific pesticides, or groups of pesticides, and screening methods are not yet available, partly because pesticides which do not absorb in the ultraviolet cannot be detected with the commonly-used UV detector. 

Derivatives may also be used to m e the molecule capable of detection by selective detectors. The reaction may be carried out during extraction (e.g. extractive methylation), on the dry residue (e.g. silylation), or during injection (e.g. methylation). If a compound requires derivatisation in order to reduce its polarity, the use of high pressure liquid chromatography should be considered instead of GLC, assmning that sensitivity is not the limiting factor. 

The D4 content of the samples was determined by reverse-phase high-pressure liquid chromatography (HPLC) with a Varian 5500 liquid chromatograph. A DuPont Zorbax ODS (Cis) column was used with a Wilmad infrared detector set at 12.45 xm to monitor the Si-CHa vibration. The mobile phase was an 83 17 mixture of acetonitrile and acetone at a flow rate of 0.8 mL/min. A Rheodyne injector valve operating on compressed air was used with a 10-p,L sample loop for reproducible injection volumes. Ethyl acetate was used to dissolve the samples for analysis. 

Fleet, B. Little, C.J. Design and evaluation of electrochemical detectors for HPLC [high-pressure liquid chromatography]. J. Chromatogr. Sci. 1974,12, 747-752. 

High pressure liquid chromatography (HPLC) was used to identify phenols and separate the products of the reaction. The system included a Dupont 870 pump module, 850 absorbance detector, and a 4.6 mm x 25 cm Zorbax ODS liquid chromatography column (all from DuPont and Co., Wilmington, DE). Analysis of 2-CP was achieved under the following conditions mobile phase 33% MeOH in water at 1.5 mL/min PCP analysis mobile pliase 50% MeOH in water at 1.5 mL/min UV detection for 2-CP and PCP at 254 nm. 

High-pressure liquid chromatography is often referred to as high-performance liquid chromatography today. Both terms can be abbreviated as HPLC, and the terms are used interchangeably by chromatographers. The applications of this very effective technique have been significantly expanded for the pharmaceutical chemist by the use of a variety of detectors such as fluorescence, electrometric, MS, and so forth. 

Waters High Pressure Liquid Chromatography apparatus (pump 6000 A, injector U6K, UV detector 440, u-styragel columns set 10 - 10 - 10 - 500 A), =254 nm, flow rate ... 

After air sampling the sorbents are subsequently extracted (seldom thermally desorbed) and the pesticides were analyzed using gas chromatrography (GC) or high-pressure liquid chromatography (HPLC). For HPLC quantification is done by UV absorption at an appropriate wavelength, whereas for GC either an electron capture detector (LCD) or a mass spectrometer (MS) are used for quantification. Depending on the sampled air volume detection limits for HPLC methods are about 0.1-1 pg m for GC-ECD methods about 0.01-0.02 pg m and for MS methods about 0.001 pg m ... 

---