Chromatographic system, dual

An additional feature of CCC is its ability to be used in either normal or reversed-phase elution with the same two-phase partition solvent system (dual mode). Both polar and nonpolar compounds are certain to be retrieved in a single chromatographic run. These features prompted us to use CCC as the initial fractionation step for active microbial extracts. 

TWO INDEPENDENT COLUMN/DETECTOR SYSTEMS. This mode of operation actually provides two independent gas chromatographic systems operating simultaneously. Each detector has its own amplifier-electrometer and recorder. The recorders may consist of a dual pen recorder or two single pen recorders. Since the two chromatograms are normally not related to each other and the starts of the analyses do not necessarily have to be simultaneous, the use of two single pen recorders is usually preferred. 

For quantitative analysis, the cell constant k is determined with a weighed internal standard and then used in calculating the amount of other compounds present. Starting with Equation 2, Paul and Umbreit (1) derived the following equation for molecular weight determination in a dual chromatographic system ... 

The main benefits of the mass chromatographic system can be summarized as follows. (1) Precise quantitative analysis can be performed without individual peak calibration. (2) Molecular weights are readily determined for compounds that can be gas chromatographed. (3) Peak identification is usually possible by the combined use of molecular weight and retention data (when such data are available). (4) The unique trap design and dual aspects of the instrument are ideally suited for evolved gas analysis from thermal analyzers, catalyst studies, etc. These benefits will be discussed throughout the paper with emphasis oriented to the polymer field. 

A novel cleanup procedure was used for TMP residues in tissue and milk samples. Tis-sue/milk samples were homogenized/dissolved with phosphate buffer, and the supernatant was purified on a Cl8 SPE cartridge previously conditioned by MeOH, water, and phosphate buffer containing pentanesulphonic acid (PSA). The TMP was eluted with MeOH phosphate buffer and injected directly into the ion-pair chromatographic system followed by dual-wavelength UV detection. The comparison of both signals ratio-enhanced the identification of the TMP peak besides the monitored UV spectra. Recoveries ranging from 73% to 98% were presented, and an LOD below the MRL set for TMP residues was achieved (176,177). 

HPLC The sample was injected on to an ACS Model LC750 chromatograph with dual pumps (Applied Chromatography Systems Ltd, Luton, Beds, U.K.) by means of a loop injection valve,... 

Chromatographic System Use a suitable gas chromatograph that is equipped with independent dual flame-ionization detectors and contains a 0.6-m x 6.35-mm (od) stainless-steel U-tube packed with Porapak P or equivalent. Use helium as the carrier gas at a flow rate of 60 mL/min, hydrogen as the fuel gas at a flow rate of 52 mL/min for each flame, and air as the scavenger gas for both flames at a flow rate of 500 mL/min. To ensure that the relative standard deviation does not exceed 2.0%, chromatograph a sufficient number of replicates of each Standard Preparation, and record the areas as directed under Procedure (see Chromatography, Appendix IIA). 

Figure 6-15 Cross-sectional view of a dual-piston reciprocating pump. (From Walker JQ, Jackson MT Jr, Maynard JB Chromatographic systems Maintenance and troubleshooting, 2nd edition, New York Academic Press. 1977.)...

A pump delivers the mobile phase through the chromatographic system. In general, either single-piston or dual-piston pumps are employed. A pulse-free flow of the eluent is necessary for the sensitive UV/Vis and amperometric detectors. Therefore, pulse dampeners are used with single-piston pumps and electronic circuitry with dual-piston pumps. 

M. Goto, N. Nakamura and D. Ishii, Micro high-performance liquid chromatographic system with micro precolumn and dual electrochemical detector for direct injection analysis of catecholamines in body fluids, J. Chromatogr, 226, 33 42 (1981). 

In another method (ASTM D-4420) for the determination of the amount of aromatic constituents, a two-column chromatographic system connected to a dual-filament thermal conductivity detector (or two single-filament detectors) is used.The sample is injected into the column containing a polar liquid phase. The nonaromatics are directed to the reference side of the detector and vented to the atmosphere as they elute. The column is back-flushed immediately before the elution of benzene, and the aromatic portion is directed into the second column containing a nonpolar liquid phase. The aromatic components elute in the order of their boiling points and are detected on the analytical side of the detector. Quantitation is achieved by utilizing peak factors obtained from the analysis of a sample having a known aromatic content. 

Dionex also offers visible, fluorescence, and pulsed amperometric detectors for use with the series 4000i. Dionex also supply a wide range of alternative instruments, e.g., single channel (20101) and dual channel (2020i). The latter can be upgraded to an automated system by adding Autoion 100 or Autoion 300 controllers to control two independent ion chromatograph systems. Dionex also supply 20001 series equipped with conductivity pulsed amperometric, UV/visible, visible, and fluorescence detectors. 

In general, a comprehensive separation strategy implies the desire to resolve/analyze all components within a sample. In the specific context of a multidimensional chromatographic method, the term is more narrowly applied to indicate that all analytes introduced to the first-dimension separation are also subjected to a second-dimension separation. There are two basic configurations used by our laboratory to carry out comprehensive multidimensional (IEX/RP) protein separations—IEX— Dual Column RP system and IEX—Dual Trap RP system (Figs. 13.1 and 13.2), respectively. 

This work was done with a Waters Model 244 liquid chromatograph having two Du Pont Blmodal IIS columns (29,000 plates/meter) and a Linear dual-pen recorder. Also used was a Waters Model 440 UV absorbance detector. Samples were run at 0.1% (w/v) using an Injection volume of 25-pL and a flow rate of 1 mL/mln. The system was calibrated with polystyrene standards from Pressure Chemical Co. according to the universal callbaratlon procedure. Data collection and computation were done with an Intel 80/30 microprocessor. 

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