"For want of a nail, the battle was lost..."

When it comes to precision dispensing, poorly manufactured disposable components can hamstring the most sophisticated benchtop or automated system. The following is a checklist to ensure that you are being provided with quality components.

• Syringe Barrel Obstructions-High-quality barrels are free of molding "flash" and other debris, such as dust, lint, fibers or molding contaminants. Debris can block the luer opening at the tip of the barrel, creating variations in the size of fluid deposits.
• Uniform Syringe Barrel Thickness-Barrel walls should be uniformly thick and smooth, without bubbles, ripples or other imperfections that can cause air pockets, create weak spots or affect the fit of the piston.
• Uniform Taper and Well-defined Barrel Threads-The fitting at the end of the syringe barrel should have a taper that is uniform in diameter with crisp, clean threads for secure barrel-to-tip attachment.
• Well-defined Piston Edges-Pistons should have uniform, well-defined edges to wipe the barrel clean and prevent dripping between shots.
• Precision Piston-Barrel Fit-Pistons should fit snugly but smoothly in syringe barrels. Pistons that are too tight may deform the barrel causing air pockets, leaks and dripping. Pistons that are too loose may leave residue on the barrel, wasting fluid and possibly causing disposal problems.
• Obstruction-Free Tip Hubs-The core part of the tip, like the syringe barrel, needs to be free of flash or debris. This is especially important when making micro-deposits: Any variation due to blockages can reduce deposits by anywhere from 30 percent to 70 percent.
• Secure Tip Attachment-Dispense tips need to be strong and clean. Tips with double-start threads are made specifically for industrial use, as opposed to medical-type dispense tips that have only a single thread.
• Clean, Even Tip Ends-Stainless steel needle tips need to be carefully polished and free of burrs and dents. For maximum cleanliness, they should also be passivated (an acid etch cleaning process) to remove rust, grease and oil. Tapered plastic tips, should have clean, consistent, blunt-cut ends. In poorly made tips, the tooling used to make the tapered tips often lacks the proper maintenance, resulting in cutoffs that vary between rounded and blunt tips, adversely impacting the consistency of deposit size, shape and location.
• Consistent Tip Color-Dispense tips should be uniformly color coded for easy identification of each gauge and internal diameter, regardless of tip length and style.
• Adapter Fit-Ease of Installation-High-quality adapters provide safe, secure connection in a design that is easy to attach to the barrel flanges.
• End Cap-Tip Cap Fit-High-volume fluid users will often preload a shift's worth of syringe barrels in advance. Precision snap-on end caps provide a leak-proof seal and are easy remove.
• Clean, Lint-free Packaging-Disposable dispensing components should be packaged in antistatic plastic bags or see-through boxes to prevent debris and contamination. Packaging should be the correct size for each order to prevent damage to components in transit.
• Lot-to-Lot Traceability-High-quality dispensing components will be labeled with lot number for greater process control and traceability.

Editorial Note: Checklist comes courtesy of EFD Inc., a Nordson Co. For additional information call 800-556-3484 or visit www.efd-inc.com.