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8 mm screw caps (ND8)

8 mm black polypropylene screw caps for 8-425 vials, with a 5.5 mm centre hole or closed top, fitted with red or blue PTFE/white silicone or white PTFE/red silicone septa, plain or pre-slit.

How to choose

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4
Quick orderPaste SKUs and quantities from your spreadsheet or PO

One line per product: SKU, then the number of packs. Up to 60 lines.

4 of 4 products

Products

Compare 8 mm screw caps (nd8)

Rows that differ are in bold.

The vial decides the cap. Match the neck and closure type first, then choose the septum material and the cap style.

Step 1: Match the cap to the vial neck

Vial neckTypical vialsCap to order
8-425 screw2 ml, 11.6 × 32 mm8 mm screw cap (ND8)
9 mm short thread2 ml and 0.3 ml, 11.6 × 32 mm9 mm short-thread screw cap (ND9)
11 mm crimp2 ml and 0.3 ml, 11.6 × 32 mm11 mm aluminium crimp cap (ND11)
13-425 screw4 ml, 14.5 × 45 mm13 mm screw cap (ND13)
15-425 screw8 ml and 12 ml15 mm screw cap (ND15)
18 mm precision screw10 ml and 20 ml headspace18 mm magnetic screw cap (ND18)
20 mm crimp6, 10 and 20 ml headspace20 mm crimp cap (ND20)
24-400 screw20 to 60 ml EPA vials24 mm screw cap (ND24)

Thread systems are not interchangeable: a 9 mm cap will not seal an 8-425 or 10-425 vial, even though the sizes look close. Crimp caps need a hand crimper, and a decapper to remove them.

Step 2: Septum material

SeptumUse it forNote
PTFE/siliconeMost HPLC and GC work, repeat injectionsThe PTFE face meets the sample; the silicone reseals after the needle is withdrawn
PTFE/silicone/PTFESamples that may contact both faces of the septumPTFE on both sides for extra chemical resistance
PTFE onlySingle injectionsVery inert, but does not reseal after piercing
PTFE/butylHeadspace GC and volatile samplesButyl rubber has low gas permeability; rated for lower temperatures than silicone
PE foam linerClosed caps for storageNot intended for needle piercing

Temperature ratings are on each product page. In this range, PTFE/silicone septa are listed for -60 to 200 °C and PTFE/butyl for -60 to 120 °C.

Step 3: Cap style

  • Centre hole or closed top: caps with a centre hole leave the septum open to the needle; closed-top caps are for storage and transport.
  • Pre-slit septa: easier needle entry, less coring and no vacuum in the vial during sampling. They reseal less well, so avoid them for volatile samples left in the tray for a long time.
  • Bonded septa: the septum is fixed in the cap, so it cannot fall out or turn during handling.
  • Magnetic caps: for autosamplers that pick up vials with a magnet, which is common in headspace GC.
  • Pressure-release caps: 20 mm headspace caps that vent excess pressure when the vial is heated.

Caps and septa are sold in packs of 100. Order caps with vials: on EROHE, equal packs of 9 mm vials and caps get 5% off both. Not sure which cap fits your vial? Email sales@erohe-lab.com with the vial part number.

Questions buyers ask

Do 8 mm caps fit 9 mm short-thread vials?

No. 8 mm caps fit only vials with an 8-425 thread.

When should I use a closed-top 8 mm cap?

For storing or transporting samples. Use a cap with a 5.5 mm centre hole for autosampler injection.

Are pre-slit septa worth it?

They reduce needle wear and stop a vacuum forming, which helps with repeat injections from the same vial. Use plain septa for volatile samples that wait in the tray for a long time.