Sampling pumping system

A flow scheme for the basic form of ion chromatography is shown in Fig. 7.3, which illustrates the requirements for simple anion analysis. The instrumentation used in IC does not differ significantly from that used in HPLC and the reader is referred to Chapter 8 for details of the types of pump and sample injection system employed. A brief account is given here, however, of the nature of the separator and suppressor columns and of the detectors used in ion chromatography. 

For capillary columns, the usual practice is to insert the exit end of the column into the ion source. This is possible because under normal operating conditions the mass spectrometer pumping system can handle the entire effluent from the column. It is then only necessary to heat the capillary column between the GC and the MS ion source, taking care to eliminate cold spots where analyte could condense. The interface must be heated above the boiling point of the highest-boiling component of the sample. 

Lazar, I. M., Karger, B. M., Multiple open-channel electroosmotic pumping system for microfluidic sample handling. Anal. Chem. 74 (2002) 6259-6268. 

Sampling artifacts. The use of in situ pumps to collect water samples for " Th analysis permits simultaneous collection (and separation) of different particle fractions as well as dissolved Th. As pumping systems have been modified to permit determination of POC on the pump filters, it became possible to compare POC determined from the pump samples with conventional POC determinations made on small volume samples (0.5 - 2 L) taken from hydrocasts. The JGOFS data from multiple studies show large discrepancies between these two sample collection methods, with pump POC values 3 to 100 times lower than bottle POC values. Possible artifacts with each approach have been identified. For example Moran et al. (1999) have suggested that DOC is adsorbed onto... 

Gel permeation chromatography was performed in tetrahydrofuran using a Waters pump system and a Model 410 differential refractive index detector for the eluant. Five Ultrastyragel columns with nominal porosities ranging from 500 to 105 angstroms were used for all the samples and the polystyrene standards. 

For the pumping system, seawater was pumped up from 9 m and collected in the appropriate bottles on the raft and returned to the shore clean laboratory for preservation and/or analysis. For the other four sampling devices, the sampler was lowered to 9 m, allowed to equilibrate for 10 min, closed by triggering mechanism activated by the Teflon messenger, raised to the surface, transferred into the container, transported back by boat and trucked back... 

Livingston and Cochran [50] collected large seawater samples by using a cable-supported electrical pumping system for subsequent determination of thorium, americium, and plutonium isotopes. Particles were removed by filtration and actinides were collected by absorption on manganese dioxide-coated filters. The samples were then analysed by standard radiochemical and a spec-trometric techniques. 

Pressurized sample infusion An easily calibrated, low volume pumping system for ESI-MS analysis of reactions... 

High Performance Liquid Chromatography (HPLC) (Chapter 30) gives an elaborate discussion of theoretical aspects. Instrumentation encompasses the various important components e.g., solvent reservoir and degassing system pressure, flow and temperature pumps and sample injection system ... 

Note The detection of signals from previously measured samples in the mass spectrum of the actual analyte is usually termed memory or memory effect. It is caused by contaminations of ion source or sample introduction system. The best way to reduce memory effects is to use the lowest amount of sample necessary to produce good spectra, to keep ion source and ion source housing at elevated temperature, and to allow some minutes for pumping between subsequent measurements. 

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