MUHWA 50-Hole Vial Rack — 4mL, 16mm Diameter, PP, Stackable
If you work with HPLC autosamplers, you handle 4mL vials by the dozen. They're short, squat, and surprisingly easy to knock over — especially when you've got ten of them lined up on a crowded bench next to the solvent bottles and the waste container. This rack gives them a home.
Fifty holes in a 5-row by 10-column arrangement. Each hole is 16mm in diameter, which matches the standard 4mL HPLC vial body (the common 15x45mm format with a 13-425 or 15-425 neck). The vials sit in the rack up to about two-thirds of their height, which gives enough lateral support to prevent tipping while leaving the cap area accessible for opening, closing, and labeling.
Why a dedicated 4mL rack matters
Most "universal" vial racks try to accommodate everything from 1.5mL tubes to 50mL Falcon tubes, and they do none of it well. A 16mm hole on a 4mL rack is snug — there's maybe 0.5mm clearance around the vial body. This means vials don't rattle when you move the rack across the bench. When you're transferring vials between the autosampler tray and the rack, you want predictable positioning, not vials leaning at odd angles because the holes are too big.
Polypropylene and solvents
PP stands up to the mobile phase solvents that inevitably drip onto the rack: acetonitrile, methanol, water, phosphate buffer. Short-term contact won't degrade the plastic. The rack won't absorb water — it comes out of a wash cycle dry. If you're working with light-sensitive compounds, note that natural PP is translucent, not opaque — wrap the rack in aluminum foil or store in a dark cabinet for UV-sensitive analytes.
Stacking system
The top rim has four raised corner posts that interlock with recesses on the underside of the rack above it. Stack three high and the column is stable — the interlock prevents horizontal shifting. This matters in storage: a stack of three racks holds 150 vials in roughly the same bench footprint as a single rack. The stacking also keeps vial caps clean — the rack above acts as a dust cover for the vials below.
Specifications
| Holes | 50 (5 rows x 10 columns) |
| Hole diameter | 16mm |
| Vial compatibility | Standard 4mL HPLC vials (15x45mm format) |
| Material | Polypropylene, autoclavable |
| Dimensions | ~180mm x 95mm x 35mm |
| Base | Drip-through, raised feet |
| Stackable | Yes, interlocking corner posts |
On the autosampler bench
Keep one rack for "to be run" and another for "completed." The 5x10 layout matches the way many autosampler trays organize their vials. When you're setting up a sequence, transfer vials from the rack to the tray in order — row 1 of the rack becomes positions 1-10 on the tray, row 2 becomes 11-20, and so forth. It's a simple system but it prevents the "which vial went where" confusion that happens when you rush a sequence setup.
