Hp plot u column

Measurements of the amount and the ¹³C enrichment of the CO₂ evolved were performed during the ¹³C-labeled 2,4-D experiments. At each sampling date, 3 gas samples were taken from the serum bottle headspace and the CO₂ was directly quantified with a micro-GC (Agilent 3,000A) equipped with a HP-Plot-U column with helium as the carrier gas. The gas sample was introduced into the micro GC via a built-in vacuum pump. The column and the detector were maintained at 80°C. The isotopic content of the CO₂ was measured with a GC-IRMS (Isochrom Optima, Micromass) on 3 other gas samples injected with a syringe into the GC. The GC was equipped with a Haysep Q column (Valco Instruments Co. Inc.) and helium as the carrier gas. The injector and detector were maintained at 180°C. The column temperature was programmed at 80°C then ramped at 30°C per min to 160°C. The δ¹³C standard deviations were 0.1‰or better. At the beginning of the experiment and after measuring CO₂, all the flasks were flushed with reconstituted air (19% O₂, 81% N₂).

Transport properties were studied using a pervaporation laboratory cell in steady-state regime at different temperatures (20, 30, 45, 60 °C) [38 (link)]. The composition of permeate and feed was analyzed by gas chromatography using a SHIMADZU GC-2010 chromatograph (SHIMADZU, Nancy, France) equipped with an HP-PLOT/U column (Agilent J&W GC Columns, Nancy, France) and a thermal conductivity detector.
The membrane permeation flux J (kg/(m²h)) was determined to be the amount of liquid transported through a unit of the membrane area per hour and was calculated as follows [41 ]: $J=\frac{W}{A\times t}$
where W (kg) is the weight of the liquids that permeated the membrane, A (m²) is the effective membrane area, and t (h) is the measurement time.
The separation factor (β) was calculated as follows [42 (link)]: $\beta =\frac{\raisebox{1ex}{$y_i$}\!\left/ \!\raisebox{-1ex}{$y_j$}\right.}{\raisebox{1ex}{$x_i$}\!\left/ \!\raisebox{-1ex}{$x_j$}\right.}$
where y_i and y_j are the weight fractions of components i and j in the permeate, and x_i and x_j are the weight fractions of components i and j in the feed.
Each measurement was performed at least three times to ensure good accuracy of the transport parameters, and the average value was recorded for later analysis. The mean accuracies for the transport parameters were as follows: for a dense membrane, ±0.5% for water content in the permeate and ±5% for permeation flux; for supported membranes, ±1% for water content in the permeate and ±6% for permeation flux.