Serpentine tubes

The low dispersion serpentine tube developed by Katz et e OO) was an alternative approach to the coiled tube and was designed to increase secondary flow by actually reversing the direction of flow at each serpentine bend. A diagram of a serpentine tube is shown in figure 3. In fact, the serpentine tubing shown in figure 3 was designed to be an interface 

Graphs of Peak Variance against Flow Rate for Coiled and Serpentine Tubes 

The flow rate is employed as the independent variable, an alternative to the more usual linear velocity, as the flow rate is defined by the column with which the low dispersion tubing is to be used. It will be shown in due course that the column flow rate is independently defined by the nature of the separation that is to be achieved by the column, It is seen that a similar curve is obtained for the serpentine tube, as that for the coiled tube, but the the maximum value of (H) is reached at a much lower flow rate than that with the coiled tube. Furthermore, the variance remains more or less constant over a wide range of flow rates that encompass those usually employed in normal LC separations. 

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As the flow rate is defined by the column with which the low dispersion tubing is to be used, the flow rate is employed as the independent variable as an alternative to the more usual linear velocity. In fact, as already noted, the column flow rate is independently defined by the chromatographic characteristics of the column. A 

The peaks shown were obtained using a low dispersion UV detector (cell volume, 1.4 pi) in conjunction with a sample valve with a 1 pi internal loop. All tubes were of 

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Alteration minerals in carbonaceous chondrites, ( ) image of twisted phyllosilicate plates in the Ivuna Cl chondrite. (b) image of hollow serpentine tubes in the Murchison CM chondrite. 

The pure anhydrous compound may be prepared by passing chlorine into a serpentine tube containing a solution of ammonium sulfate, carrying the volatile compound... 

Any conduit system that has low dispersion will also provide very fast heat transfer rates. Serpentine tubing has been also used in commercial column ovens to heat the mobile phase rapidly to the column oven temperature before it enters the column. The serpentine tubing allows effective heat exchange with a minimum of heat exchanger volume to distort the concentration profile of the solvent gradient. 

The width and asymmetry is reduced using a tube with an ID. of 0.18 mm but serious asymmetry remains. It is clear that under conditions where the tube length between the end of the column and the detector sensor can not be made sufficiently short to restrain dispersion, the use of low dispersion serpentine tubing may be a satisfactory alternative. 

Chromatograms of a Blood Sample Monitored by the UV Detector and the Atomic Absorption Spectrometer with the Serpentine Tube Interface... 

Katz and Scott [42] solved this problem by the use of low dispersion serpentine tubing as the interface between the exit from the UV detector of the liquid chromatograph and the spectrometer. A diagram of their interface is shown in figure 43. The principle of low dispersion tubing has already been discussed and it is sufficient to say that the outer interface tube was 49 cm long, 0.25 cm I.D. and merely protected the serpentine tube contained inside. The inner serpentine tube had a peak-to-peak amplitude of 1 mm. An example of the chromatograms obtained from a blood sample monitored by both a UV... 

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