MUHWA 40-Hole Vial Rack — 20mL, 28mm Diameter, PP, Stackable
Twenty-milliliter vials are an awkward size. Bigger than standard HPLC vials, smaller than media bottles. They get used for headspace GC, for scintillation counting, for reagent aliquots — and they rarely have a dedicated rack that actually fits them. Most labs improvise with beakers or cut-down cardboard boxes. Here's the proper tool.
Forty positions, each 28mm in diameter, arranged in a 4-row by 10-column grid. That 28mm matches the body diameter of standard 20mL headspace vials (the 22.5x75mm format with a 20mm crimp neck) and 20mL scintillation vials. The holes are deep enough that the vial sits with its center of gravity below the rack surface — even a tall 75mm headspace vial won't tip when you nudge the rack.
Headspace GC workflow
Headspace vials get heated — sometimes to 90°C or higher — before injection. When you pull a hot vial out of the headspace sampler and need somewhere to put it, an improvised holder that melts or softens is a bad surprise. This PP rack has a softening point above 130°C; it handles post-run vial temperatures without deformation. The 4x10 layout also maps cleanly to a 40-vial headspace autosampler tray: one rack per tray, direct transfer.
Spill-through base design
The bottom of each well has a small drain hole. When you're washing vials and racking them wet, water drains through instead of pooling at the bottom of the well — no mineral deposits building up over time, no vial labels soaking off from standing water. The rack itself sits on four raised feet, so the drain holes have clearance from the bench surface and liquid can actually escape.
Materials and chemical exposure
Same autoclavable polypropylene as the rest of the rack family. Resistant to the organic solvents used in headspace sample preparation: methanol, ethanol, DMF, DMSO (room temperature). If you accidentally knock over a vial of dichloromethane onto the rack, wipe it off — PP will swell slightly with prolonged chlorinated solvent contact but won't dissolve or crack. The rack is not intended for direct solvent immersion or long-term solvent storage.
Specifications
| Positions | 40 (4 rows x 10 columns) |
| Hole diameter | 28mm |
| Vial compatibility | 20mL headspace vials, 20mL scintillation vials |
| Material | Polypropylene, autoclavable |
| Drainage | Drip-through holes in each well base |
| Stackable | Yes, interlocking corner system |
| Dimensions | ~300mm x 130mm x 48mm |
Labeling and organization
The rows and columns aren't pre-labeled — this is intentional. Use a permanent marker to number your own grid on the rack surface. Most labs write column numbers 1-10 across the top and row letters A-D down the side, then log "vial B7" in the lab notebook. The PP surface takes Sharpie marks well and they survive water and ethanol but come off with isopropanol if you need to relabel. For labs running multiple headspace methods, color-coding racks with tape works too — red rack for method A, blue for method B.
