Column connection

Place 146 g. of adipic acid, 360 ml, (285 g.) of absolute ethyl alcohol 180 ml. of toluene and 1 - 5 g. of concentrated sulphuric acid in a 1-litre round-bottomed flask, attach a short fractionating column connected to a downward condenser, and heat in an oil bath at 115°, When the acid... 

HCl and 50 ml of water. The upper layer was separated off and the aqueous phase was extracted five times with small portions of THF. After drying the combined solutions over magnesium sulfate the solvent was removed in a water-pump vacuum. The residue was distilled through a 30-cm Vigreux column, connected to an air condenser. After a preliminary aqueous fraction of the carboxylic acid the main fraction passed over at 100°C/15 mmHg. The compound solidified in the receiver and (partly) in the condenser. The yield was almost quantitative. 

Apparatus. 1-1 three-necked, round-bottomed flask, provided with a dropping funnel, combined with a thermometer, reaching into the liquid, a mechanical stirrer and a 40-cm Widmer column, connected with a condenser and a receiver, cooled at -20°C or lower. 

Figure 4.3 Schematic diagram of a thermal sweeper system located between two columns in the gas cliromatograph Cl, C2 and C3 are column connections, with C2 being small enough to allow the slotted heater S to pass over the connection. The accumulator column A retards the travel of solutes tlnough this section until the sweeper expels them out to the uncoated column (called a pigtail (P)), wliich then delivers them as a naixow band to the second column. The modulation drive, M, is external to the GC oven.

On the other hand, supposing that we have n identical columns connected in series, the peak capacity is given, in analogy to equation 5.3, by the following expression (10) ... 

The experimental conditions are shown in Table 13.1, while Figure 13.9 shows the chromatogram of a soil sample extract spiked with fenpropimorph obtained by this method, plus the chromatogram from the two columns connected in series without column switching. 

Figure 13.9 Coupled-column RPLC-UV (215 nm) analysis of 100 p.1 of an extract of a spiked soil sample (fenpropimoiph, 0.052 mg Kg ). LC conditions C-1, 5 p.m Hypersil SAS (60 m X 4.6 mm i.d.) C-2, 5 p.m Hypersil ODS (150 m X 4.6 mm i.d.) M-1, acetonitrile-0.5 % ammonia in water (50 50, v/v) M-2, acetonitrile-0.5 % ammonia in water (90 10, v/v) flow-rate, 1 ml min clean-up volume, 5.9 ml transfer volume, 0.45 ml. The dashed line represents the cliromatogram obtained when using the two columns connected in series without column switcliing. Reprinted from Journal of Chromatography A, 703, E. A. Hogendoom and R van Zoonen, Coupled-column reversed-phase liquid cliromatography in envir onmental analysis , pp. 149-166, copyright 1995, with permission from Elsevier Science.

GC-GC has typically been employed for complex samples or those requiring additional chemistry, such as chiral recognition, to be employed along with classical GC separation. Typical GC-GC systems employ multiple capillary columns connected... 

In the SMB operation, the countercurrent motion of fluid and solid is simulated with a discrete jump of injection and collection points in the same direction of the fluid phase. The SMB system is then a set of identical fixed-bed columns, connected in series. The transient SMB model equations are summarized below, with initial and boundary conditions, and the necessary mass balances at the nodes between each column. 

When a problem is noted, it is generally best to look for solutions in easy-to-check-out areas. For example, check for leaks at all column connections and external fittings. Once the simple checks are completed, attempt to isolate the problem to the injector, column, detector (or transfer line), or instrument. 

As an alternative, sampling BW from a point just below the extra-low-level alarm point usually is also suitable. However, the BW is not always at its most concentrated point at the water column connection. A sample taken from this point may contain a mix of BW and steam, which leads to errors in sampling and hence, testing, reporting, interpretation, and subsequent actions. 

The column packing proced ire strongly influences the retention of large sized particles. The percentage of unretained particles of any size can be estimated from the ratio of its chromatogram areas obtained with and without the columns connected to the chromatograph. 

Application of HPLC-MS to the analysis of a black tea liquor was studied in a paper by Bailey 39 a great deal of useful information could be obtained without sample pretreatment. A tea liquor was applied to a wide-pore HPLC column connected to a mass spectrometer by a VG Plasmaspray interface. Pseudo-molecular ions were obtained from the flavanols, flavanol gallates, chlorogenic acids, 4-coumarylquinic acids, and caffeine, but the flavanol glycosides were extensively fragmented by the interface. Fragments were obtained from unresolved polymer that supported its previous designation as a flavanol polymer. 

We should therefore use small bore tubing in short lengths for making the injector-column and the detector-column connections, and the injector and detector must be designed so that their internal volume is as small as possible. Dead volume before the introduction of the sample should also be minimised, to facilitate rapid changes of mobile phase composition that may be required during gradient elution. 

Phenylthiocarbamoyl derivatives of 18 chiral amino acids were separated on a C8 column connected in series to a phenylcarbamoylated (3-cyclodextrin column (Iida et al., 1997). The Cg column separated the derivatized amino acids from one another entering the chiral column. Under this configuration several enantiomers of adjacent amino acids coeluted resulting in poor resolution. However, this configuration was successful in determining the amino acid sequence and chirality of the amino acids in a D-amino acid containing peptide. 

Achiral-chiral chromatography has also been accomplished using subcritical fluid chromatography (Phinney et al., 1998). In this work, the structurally related [3-blockers, 1,4-benzodiazepines, and two cold medicines were separated using methanol or ethanol modified carbon dioxide mobile phases. The (3-blockers were separated using cyanopropyl and Chiracel OD columns connected in series. Likewise, an amino bonded phase and Chiracel OD column were used for the separation of the 1,4-benzodiazepines. Guaifenesin and phenylpropanolamine from cough syrup were separated on cyanopropyl and Chiralpak AD columns in series. 

Noncondensable gases leaving the condensation vessels were depressurized (by means of an electronic back-pressure, Brooks Instrument model 5866), totalized (by means of an on-line flow gas meter, Ritter model TG05-5), and periodically analyzed with an on-line GC (Hewlett-Packard model 6890) equipped with three columns and two detectors for the analysis of Cj-C10 hydrocarbons (A1203 plot capillary column connected to a flame ionization detector), H2, CH4,... 

CO (molecular sieve packed column connected to a thermal conductivity detector), and C02 (porapak Q packed column connected to a thermal conductivity detector). 

The concentrates were subsequently analysed for arsenic using Varian-Techtron AAS atomic absorption spectrophotometer fitted with a Perkin-Elmer HGA 72 carbon furnace, linked to a zinc reductor column for the generation of arsine (Fig. 5.3). A continuous stream of argon was allowed to flow with the column connected into the inert gas line between the HGA 72 control unit and the inlet to the furnace. Calcium sulfate (10-20 mesh) was used as an adsorbent to prevent water vapour entering the carbon furnace. The carbon tube was of 10 mm id and had a single centrally located inlet hole. 

FIGURE 11.4 AASP fluidics showing guard and analytical column connection with the same valve. (Source From Kabra, P.M. et al. Clin Chem. 33, 2274, 1987. With permission.)... 

Other combinations are available. For example, liquid chromatographs connected to mass spectrometers (known as liquid chromatography-mass spectrometry [LC-MS]) are fairly common. Almost any combination of two instruments that can be thought of has been built. In addition, two of the same instruments can be connected so that the output from one is fed directly into the other for further separation and analysis. Examples include two mass spectrometers in an MS-MS arrangement and two different gas chromatography columns connected in a series, known as GC-GC. To keep up with these advances, one needs to have a working knowledge of the fundamental principles involved in the techniques and of the abbreviations used for the various instrumentation methods. 

The experimental facility is a pilot-scale distillation column connected to an industrial ABB MOD 300 distributed control system, which in turn is connected to a VAX cluster. The control system consists of a turbo node (configuration, history, console) remote I/O, and an Ethernet gateway, which allows communication with the VAX-station cluster through the network. This connection allows time-consuming and complex calculations to be performed in the VAX environment. Figure 10 shows the complete setup. 

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