Detectors for high pressure liquid chromatography

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

Fig. lUl Electrochemical detector cells for high-pressure liquid ctiromatography. (a) Porous lectrode cell for coulometric detection in high-pressure liquid chromatography (Courtesy Coulochem). (b) Thin-layer ampcrometric detector for high-pressure liquid chromatography, (c) The Wall jet ampcrometric odl. (Courtesy EDT Research.)... 

F.E. Brinckman, K.L. Jewett, WR Iverson, K.J. Irgolic, K.C. Ehrhardt, and R.A. Stockton. Graphite furnace atomic absorption spectrophotometers as automated element-specific detectors for high-pressure liquid chromatography. The determination of arsenite, arsenate, methylarsonic acid and dimethylarsinic add. J. Chromatogr., 191, 31 (1980). 

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

Yao and Wasa (1988a) assembled modified electrodes for amino acids by crosslinking L- or D-amino acid oxidase with glutaraldehyde on silanized platinum probes. The sensors were employed as detectors in high pressure liquid chromatography. Whereas the L-amino acid oxidase electrode responded to L-tyrosine, L-leucine, L-methionine, and L-phenylalanine in amounts as low as 2 pmoles, the D-amino acid electrode measured only D-methionine and D-tyrosine. The response time in steady state measurements was only 5-10 s. 

Inc. System (two model 6000A pumps model 440 UV detector with a 254 filter model 680 gradient controller model 746 data module and a RCM 8 X 10 cm Radial Compression Cartridge Holder) was used for high pressure liquid chromatography. Injections were made with a model 7125 Rheodyne injector. 

The major application of porous, three-dimensional electrodes has been in metal removal from dilute process liquors (Chapter 7) although inorganic and organic dectrosynthesis applications continue to be explored (see, for example, the Dow-Huron cell for production in Chapter S). Many battery and l el cell electrodes utilize an active material which is (or is supported by) a porous, three-dimensional matrix (Chapter 11), while miniature porous electrodes have found use in electrochemical detector systems for high-pressure liquid chromatography analysis (Chapter 12). 

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. 

Shultz and Mathis [39] developed an ion-selective electrode detector for high-pressure ion-exchange chromatography. The detector was based on a commercial liquid-membrane ion-selective electrode, and was sensitive to nanomole amounts of inorganic and organic species. These electrodes have much potential for the analysis of ionizable species in column effluents. 

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

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. 

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. 

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 ... 

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