Cleaning the MCGV (G1311-67701) for the Agilent 1100 Quaternary Pump Kenny Sharp March 16, 2011 The MCGV, or Multi-Channel Gradient Valve, is the device that controls the proportioning of mobile phases going into your HPLC system. Located upstream from the pump, it features four inlet lines (A, B, C and D) and one outlet line which connects to the pump’s AIV (active inlet valve). It ensures that each intake stroke of the first piston contains the specified mobile phase composition. The controller divides the length of the intake stroke into certain fractions, in which the MCGV connects the specified solvent channel to the pump input. The flow of each mobile phase is controlled by a solenoid valve, which is activated by the board according to the values programmed by the user. That clicking sound you hear from your pump all the time? That’s the MCGV toggling the solenoids to open or close the valves. Chances are that at some point, you’ll notice problems with your solvent delivery or gradient. Maybe the wrong mobile phase will enter your system, or the correct mobile phase won’t, or the gradient is messy. Most often we find a problem during OQ/PV when the composition tests fail – that is, the system tells us about a problem we didn’t even know about! A replacement MCGV can cost $1500$2500 – you might as well buy a new pump! Before you get out the credit card and shell out for a replacement, why not give your MCGV a quick cleaning? You will need a #2 Phillips head screwdriver, a 2.5mm hex key (or a 3/32”), some fine-tipped forceps, some isopropanol or cleaning solvent of your choice, and some lint-free wipes. Each of the four valves takes about 10 minutes, with 5 minutes to remove or re-attach the MCGV. Ready? First off, shut off your pump and remove the front cover. Disconnect the outlet tube, waste tube and the solvent tubes from the MCGV, unclip them from the tube clips and place them into the solvent cabinet to avoid them flooding your work area. Press in the lower sides of the cover and pull out to remove it. 1. Disconnect the MCGV cable and the two holding screws, and lay the MCGV out on a clean work surface. 2. Use the hex key to remove the four small screws securing the solenoid to the hub. There will be some slight pressure on account of the spring in the mechanism. Here it is with the screws removed and the solenoid off to the side. Do not adjust or move the central screw or nut which are marked with paint (more on that later). 3. Here’s the plunger. Give this guy a nice little batch in isopropanol. Sonicate it if you need to. Set aside for later. 4. This black plastic piece lifts off the hub. On the underside you can see that it secures a clear plastic membrane (see arrow) over the ball valve. Give it a nice wipedown with isopropanol. 5. Here’s the membrane. Give it an isopropanol bath. That little guy is like a contact lens if you lose it, so don’t drop it! 6. Here’s the ball valve. Be really careful not to lose the jewel (see arrow) as you clean it out. 7. Back to the solenoid. There can be a lot of crud in here. Make sure you rinse it out well. 8. Put the membrane back in the plastic cover and place gently back onto the hub to secure the ball valve. Then put the solenoid onto the cover. Make sure the solenoid is oriented correctly. 9. Pop those screws back in. Don’t overtighten, they just need to be snug. As I mentioned, do not turn the nut or hex screw in the centre (see arrow), it controls the depth of the solenoid chamber, and if you change that, the solenoid might not function properly (might not open or might never close). They are marked with orange paint to indicate how the two must line up – don’t remove that paint! Lastly, screw back into the pump unit and reconnect the cable. Put the plastic cover back on and replace the tubing – obviously, take care not to mix them up. Put the cover back on, power up the unit and you’re off to the races. It goes without saying that the MCGV might not function properly despite this cleaning. Nonetheless, at least you can say that you did your best to save the company/lab some money!