Teledyne UA-6, Инструкция по установке и эксплуатации

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UA-6 Detector
Section 3 Operation
3-10
3.7.2 Flow Rate
The Teledyne Isco high flow rate cell is designed to handle liquid
flows up to about 3 liters/min with negligible pressure drop.
Liquids with viscosities much greater than water may present
difficulties at high flow rates, while most cells can handle higher
flow rates of water or other non-viscous liquids if some pressure
drop across the flow cell is not objectionable. In principle, flow
rates can be as high as that which does not result in a pressure
drop exceeding the rated pressure limit of either the flow cell or
fittings. However, an excess of pressure drop across the flow cell
requires higher total pressure for the chromatographic system,
which may present difficulty for some chromatographic pumps.
With 60% aqueous sucrose solutions at 800 ml/min as an
example of a viscous liquid (58 cP), UA-6 preparative cells show
about 6 psi pressure drop. With water at 50 ml/min, the prepar-
ative cells show about 2 psi pressure.
UA-6 preparative flow cells can often be applied in experiments
where flow rates exceed 1 liter/min.
At extremely low flow rates (e.g. below 10 ml/hr), preparative
flow cells are recommended because of their better gas bubble
expelling properties. At very low flow, bubble problems will be
increased because of greater increased heating of the eluent as it
passes through the detector.
3.7.3 Preparative Cells
In low pressure liquid chromatography where the peak volume of
eluted components is large (over 1 ml), preparative flow cells are
best. These cells have a straight-through vertical flow design to
quickly expel trapped bubbles due to outgassing. The larger illu-
minated volumes of preparative flow cells do not affect the
intensity, resolution, or the shape of larger peaks.
3.8 Avoiding Bubble
Formation and
Retention
Bubbles form in a flow cell when it is warmer than the temper-
ature of the column and because the cross-sectional area of the
flow path is changing rapidly. The following steps, taken sepa-
rately or combined, should deal with most bubble problems.
1. Degas the buffer or solvent prior to eluting the column by
applying a vacuum. Heating or ultrasound treatment dur-
ing vacuum degassing is beneficial.
2. Warm the buffer or solvent, if possible, to about 3°C above
the column temperature. This decreases the ability of the
mobile phase to absorb and hold gases.
3. Be sure the direction of flow through the flow cell is from
bottom to top.
4. Be sure the flow cells are clean. Material from a previous
application that coats the inside of a flow cell may provide
a surface for bubble formation and adhesion. Excellent
cleaning results can usually be obtained by using isopropyl
alcohol (IPA), water, detergent solution, water, IPA, hex-
ane, IPA, and finally water. In some cases, it may be neces-
sary to remove the flow cell windows and clean them
separately (see Section 5.6.2).
5. Select the appropriate flow cell.