Principle and usage of the soap film flow meter

(1) Connect the column outlet to the detector, and fill the soap film flow meter with an appropriate amount of soap solution. Adjust the liquid level to be exactly at the midpoint of the branch pipe opening, and connect it to the carrier gas using a rubber hose. (2) Turn on the carrier gas and adjust its pressure to the desired value. After one minute, gently pinch the rubber tip to cause the soap solution to rise and seal the branch tube, thereby creating a soap film. (3) Use a stopwatch to record the time it takes for the soap film to pass through a certain volume, and convert this value into the gas flow rate in mL/min. The carrier gas flow rate is one of the important operational parameters that affect chromatographic separation, and it must be measured regularly. The rotameter on the chromatograph is used to measure the volumetric flow rate of gases, but there is no simple linear relationship between the rotor height and the flow rate, and this relationship depends on the medium. Therefore, it needs to be corrected using a soap film flow meter. (1) Apparent volumetric flow rate (F’CO): The volume directly measured behind the column using a soap film flow meter is called the apparent volumetric flow rate. It includes not only the carrier gas flow rate but also the saturated vapor flow rate under the prevailing conditions. (2) Actual volumetric flow rate (FCO) PO: Atmospheric pressure, mmHg ； PW: Saturated vapor pressure at room temperature, in mmHg. (3) Corrected volumetric flow rate (FC): Since the volume of gas changes with temperature, and the column temperature is different from room temperature, a temperature correction is necessary. Pi: Carrier gas pressure at the column inlet ； Po: The pressure of the carrier gas at the column outlet; when performing calculations, Pi and Po must have the same units. The actual volumetric flow rate can be calculated using the following formula. The corrected volumetric flow rate of the carrier gas within the column under column temperature conditions is determined using the following formula

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This post was last edited by shakic on 2010-11-28 at 21:15. The era of glass soap film flow meters combined with stopwatches is over; nowadays, electronic soap film flow meters are used. Automatic measurement and calculation of test data; no need for manual timing by looking at the membrane. High measurement accuracy, reduced conversion time, and minimized human error. The liquid crystal display shows the flow rate under operating conditions and the measurement time directly, while also performing automatic calculations and statistics. http://www.shakic.com/cp/zaomollj.htm