Did everyone prepare their own capillary columns, or did they purchase ready-made ones?

There won’t be many people who can pair this with it, and it’s not easy to find a suitable match either. If you’re not into research, just buy it! We tried to do it before, but it didn’t work very well! Let me repost the preparation process; it seems to have been written by Pang Diding, and it’s quite detailed. Just take a look and you’ll know. Process of preparing the capillary column: Step 1: Create the column skeleton. Initially, it was planned to use a circular skeleton with a circumference of 60 centimeters, but this idea was rejected as it was not possible to secure the area around the column feet. In the end, the polygonal keel scheme was chosen. The polygon initially used a hexagon, but after testing it was found that with six points around the column, they would overlap rather than intersect when moving around the column; therefore it was changed to a heptagon. (The dragon skeleton must have an odd number of sides.) Each side of the heptagon is 7 centimeters long. (1) Markings: I purchased a roll of ordinary thick wire and a bunch of thin wire at Robam in Luohu. Cut a 105-cm length of thick iron wire, and use a flat-headed hammer to flatten and straighten it on a flat and hard surface. Use a ruler to measure 7, 3, 1, 3, 7, 3 centimeters and mark them with a highlighter, repeating this sequence 6 times; leave 5 centimeters at the end for easy connection between the beginning and the end. Length calculation: 7×7 + 7×(3+3+1) + 7 (or 5) = 105. (2) Bending: Use two pliers to bend the wire at each marked position, ensuring that each bend forms a perfect right angle and that all bends are at the same horizontal level; in other words, the wire after multiple bends should be able to lie flat on a surface without any protrusions. After bending at the last marked point, shape the wire into a heptagon by bending it in a crown-like manner, with the ends connected together. (3) Closing: Welding is preferred; if no welding tools are available, thin iron wire can be used to wrap around the connection point and tie it tightly. (4) Fixing crossbeam: Cut another 20-cm length of thick wire to use as the fixing crossbeam; bend 1 cm at each end, leaving a length of 18 cm in the middle. The fixed crossbeam is added after surrounding the column; its purpose is to prevent the column from spreading apart. (5) Precautions: After cutting the wire, file off the sharp ends at both sides first, otherwise it is easy to cut your hand. When flattening, straightening, or bending, avoid leaving mechanical marks on the surface of the wire. It takes about 70 minutes to prepare a dragon skeleton. Step 2: Circumference around the column. Although the framework of the dragon is polygonal with seven sides, it forms a circle when wrapped around the column; its circumference is 2×3.14×0.11 (actual measurement value) = 0.692. It is planned to use columns that are 15 meters long with an inner diameter of 0.53 mm; 21.7 turns should be sufficient, but 22 turns can also be used. Take the commercial quartz optical fiber (produced by Hebei Yongnian Optical Fiber Factory, with an inner diameter of 0.53 mm), and slowly pull it out while rotating it (make sure there are no bending or twisting movements!) ! ), while rotating the dragon skeleton to cause the quartz optical fiber to cross at every two winding points; after 22 turns, it was cut, and a fixing crossbeam was installed. Note: When moving around the column, avoid any scraping or rubbing to prevent damage to its outer surface. Step 3: Prepare the sealing glass tube. Take a regular glass tube with an inner diameter of 2–3 mm, cut it into small segments, each about 2–3 centimeters long, and seal the cracks using an alcohol burner. Place it in dilute nitric acid and perform ultrasonic cleaning; after that, rinse it with deionized water until it is clean, and use a pH test strip to ensure that there is no acidity left. Place it in an oven at 150 degrees to bake out the moisture. Finally, seal one end of each section with an alcohol burner. Tip: This task can be completed before preparing the column. Note: Sealing method: Dissolve the two-component adhesive in dichloromethane (the colorless and transparent type available at B&Q, made in Germany). Be careful that the container used to hold the solution should not have a lid; instead, a sealing film should be used. Drop it into the sealing tube so that there is at least half of the volume in the tube, insert the capillary into it; once the solvent has evaporated, the two-component adhesive begins to cure, completing the sealing process. Method to open the seal: Cut the capillary column right next to the seal tube opening. Step 4: Treat the inner surface: Use a capillary column cleaning device (available from Agilent**, or it can be made manually using a plastic tube with a lid and a sampling port from Shimadzu gas chromatography equipment); place a small glass tube inside it, with the inner diameter of the tube being just large enough to fit it in. The smallest type of forceps can be used to remove it. The tube is filled with 20% (W/W) nitric acid solution; one end of the capillary column is inserted into the bottom of the tube while the other end is left open. A short capillary column about 40 cm long is used to connect the injection port of the gas chromatograph at the gas-filled part of the setup (pay attention to the different connectors). The short capillary column must be carefully extended from the hinge of the gas furnace to prevent it from being crushed when the furnace door is closed. Turn on the gas chromatograph, set the temperature to room temperature, and set the flow rate to 1 ml/min (the minimum setting). When the volume is approximately 90% filled, stop supplying gas, remove the column, and seal both ends of the column with sealing tubes (see Section 3 for the method). Then place it in a gas chromatograph and heat it to 160 degrees Celsius for 4–8 hours. Note: It is recommended that Shimadzu use a GC-17A gas chromatograph with a constant current mode, as its graphite gasket can be easily removed from the screw cap and is quite small in size. Step 5: Washing. Open both ends of the treated column, reinsert it into the cleaning device, fill the small tube with ionized water, and perform inflation-based cleaning to remove the acid from within the column; afterwards, blow dry it using nitrogen gas. During the process, water begins to leak out from the other end only when the liquid level in the small tube of the cleaning device drops by one-third; formic acid is flushed out at a flow rate of 20 ml/min, and it takes 8 minutes to completely flush it out. Then dry it with an air flow rate of 40 ml/min, continuing until no water droplets remain at the outlet, and keep it in that state for about 10 minutes. Remove the column and place it in a gas chromatograph; connect one end to the gas inlet and leave the other end open. Set the temperature to 250 degrees and ventilate for 2–4 hours to thoroughly dry the inner wall of the column. Step 6: Modification. Again, use the cleaning device with a small tube inside; fill this tube with 0.8 ml of a 6% (W/W) PEG-20M solution in dichloromethane. Insert a capillary column at the top of the tube, extending it down to the bottom of the tube. Set the gas flow to a constant flow at the minimum level, and maintain the temperature at room temperature. Allow dynamic coating by passing gas through the system. When the solution in the tube is nearly at the bottom, stop the gas flow, open the device, remove the tube using small forceps, then close the device again and continue to pass gas for about 40 minutes. After the solution has moved through the column, keep passing gas for another hour to ensure complete cleaning. Next, seal both ends of the column, place it in a gas phase furnace, raise the temperature to 280 degrees, and treat it for 2–4 hours. After that, open both ends again, connect a cleaning device; fill the small tube with dichloromethane to remove any unreacted fixing agent, and then dry it out before using it for coating. Note: Add 0.3 grams of PEG-20M to 5 ml of dichloromethane to obtain a concentration of 6%. Step 7: Cross-linking coating. Weigh 0.1 grams of OV-1 fixing solution and dissolve it in 10 ml of dichloromethane to obtain a 1% OV-1 solution (note: it must be prepared in advance as it is difficult to dissolve). Next, weigh 0.0030 grams of BP and add it to 3 ml of dichloromethane; then take 1 ml of this mixture and add it to the 1% OV-1 solution, mixing well. Then BP is also 1%. After preparation, sonicate for 5 minutes to remove gas, yielding the filling fluid. Fill the cleaning device’s small tube with the filling liquid, insert a capillary column at the top, then inflate it. Stop inflating once the liquid level in the tube drops by 1 centimeter. Remove the small tube using small forceps and continue inflating for about 1 hour. Step 8: Baking. Connect the capillary column to the injection port, set the oven temperature to 50 degrees, and bake for 2 hours; then increase the temperature in sequence to 100 degrees, 130 degrees, and 150 degrees, with a total baking time of 1.5 hours. Step 9: Washing. Remove the capillary column and attach a cleaning device; fill the small tube with dichloromethane. Use a total of 20 ml of dichloromethane for rinsing (add more if one tube is not sufficient), then blow it clean using nitrogen at a flow rate of 20–30 ml/min until no liquid droplets more come out, and maintain this condition for 20 minutes. Step 10: Aging – Perform aging at 40 degrees for 5 minutes, then at a rate of 20 degrees per minute, up to 280 degrees; hold at 280 degrees for 1 hour. Equipment used: HP5890, head pressure: 4 psi. Step 11: Testing – The specifications for the capillary column are a length of 15 meters and a diameter of 0.53 mm; the column head pressure is 4.8 PSI, and the detector used is FID. Heating sequence: 80°C – (1.5 min) – 20°C/min – 250°C. The retention times for the various substances being tested are as follows: BHA: 3.54 min; BHT: 1.88 min; TBHQ: 5.38 min; Benzoic acid: 2.71 min (with slight tailing). Additionally, isobutanol and isopentanol can be separated, while methanol cannot be detected. Addendum: (1) 5 small tubes are required to make one column: 2 for nitric acid, 2 for PEG20M, and 1 for dynamics. (2) If columns are to be used, cross-linked columns must be employed; the other types of columns described in books generally have little significance. This post was last edited by chengjingbao on 2009-3-2 17:34]

It’s really troublesome. Pasted it. Saved. I’ve learned it.* Thank you.

The capillary columns we use are all purchased directly!

Filling columns can generally be made by oneself, while capillary and column tubes need to be purchased

1. As manufacturers of instruments, they rarely produce capillary chromatography columns on their own. 2. The procedures for production mentioned on the second floor can be compiled and stored as useful reference material. 3. There are several companies in China that do a good job in this area: Qingdao, Tianjin, Shanghai, Hangzhou. 4. When using FFAP capillary columns, it is important to deoxidize the carrier gas; we have encountered problems using FFAP columns in the past. Currently, FFAP is recommended for the detection of o-nitro compounds according to national standards, but we have switched to using HP-5 columns instead

Capillary columns are generally provided by the manufacturer; it is necessary to agree on this when purchasing the instrument, including the free provision of certain accessories