GC046 Temperature zones

The control of temperature is one of the easiest and most effective ways to influence separation. The control of temperature is necessary to achieve a good separation in a reasonable amount of time.

Comments

Post a Comment

Popular posts from this blog

GC069 Stationary Phases

 Two of the main decisions in setting up a chromatograph for an analysis are the stationary phase and the column temperature program. The selection of the stationary phase is less critical for open tubular columns than for packed columns, because of their much higher efficiency.
Read more

GC036 Flow Measurement

There are two ways of measuring the flows independently. The first one is an inexpensive soap-bubble flowmeter which consists of a calibrated tube (usually a modified pipet or buret) through which the carrier gas flows. With a rubber bulb we can create a bubble, which is raised into the path of the gas. After that, the ascension of a particular bubble to a defined volume is measured with a stopwatch. The carrier gas in mL/min is easily obtained from this measurement. There are also available electronic soap film flowmeters at a cost around $50. The second alternative is the use of a sophisticated device, composed of a solid-state sensor and a microprocessor to accurately flow measurements without using soap bubbles. Silicone-on-ceramic sensor can be used to measure flow rates of 0.1-500 mL/min for air, nitrogen, oxygen, helium, hydrogen and 5% argon in methane. The cost for this device is around $700. Very small flow rates, like the ones found in tubular columns, cannot be measured rel...
Read more

GC024 The Original Van Deemter Equation: Packed columns

Van Deemter identified three effects that contribute to peak broadening in packed columns: Eddy diffusion (term A), longitudinal molecular diffusion (the term B) and mass transfer in the stationary phase (the term C). The Van deemter Equation is: H = A + B/ µ + C µ Where H is the plate height, and µ the linear gas velocity. A small value indicates a narrow peak (the desired condition). Minimize each term is the way to maximize column efficiency.
Read more