VMax-Vial - the big „Vase“ for optimised microsampling

We can produce any standard vial up to 60 ml with our patented „Vase“ foot for optimised microsampling.

The VMax-Vial has a cylindrical foot. We chose a „cylindrical foot“ over a „cone foot“ as we think a cylindrical foot is technically superior for the sample taking in an autosampler.

A sampler usually pierces the sealing septum with a needle which descends to a defined height to take the sample. The needle has two functions, to pierce the septum and to withdraw the sample. The needle should be formed so that it easily pierces the septum. If the needle has a bevel tip it must not hit the bottom of the vial or the needle tip will be bent which will negatively influence the further piercing of the septum. If the needle has a cone tip it must not hit the bottom of the vial either as the needle whole could become sealed by the vial bottom so that no sample is taken. If a needle with side hole is used the system may be adjusted so that the needle tip rests on the bottom of the vial but still the needle hole is above the bottom of the vial. Independent of the needle geometry, the highest point at which the sample enters the needle defines the death volume of a vial.

In order to get the maximum sample return, air should usually not be sucked into the needle with the sample. This requires minimal sample coverage over the needle hole. For most samplers, it can be said that the needle descends to a defined level above the intended withdrawing level (commonly 2.5 mm above withdrawing level). As the withdrawing level is at the bottom of the vial, the vial producer must assure that the vial bottom has a reproducible inner height. The dead volume can be derived with the measure that the bottom of the vial has a radius r (=ø foot/2) and the needle hole is above the bottom at height h.

The death volume of the cone version forms a cone stump with the side angle a;

The death volume of the cone version results in
VKS = π * h/3 (3r2 + h2 tan2(a) + 2r * h* tan(a))

the cylindrical version, as produced by GTG, forms a cylinder.

The death volume of the cylindrical version results in:
VZyl = π * r2 * h

in this example applies: death volume to needle hole
r = 1.5 mm, h = 1.5 mm and a = 45° -> tan(a) = 1
VKS= 21.2 μl
VZyl = 10.6 μl

This means that the dead volume of the cone version is bigger by a share of π * h/3 (h2 * tan2 (a) + 2rh * tan(a)).

With an angle a bigger 45°, tan(a) > 1 and increases considerably.
The same results when the needle hole has to be covered with sample.
In this case height h = height h (needle above base) + ü (coverage with sample).

in this example applies:
death volume to coverage r = 1.5 mm, h = h + ü = 1.5 mm + 2.0 mm = 3.5 mm and a = 45° -> tan(a) = 1
VKS= 108.1 μl
VZyl = 24.7 μl

It can be concluded that in order to minimise death volume tan(a) one has to aim towards zero which means that a cylindrical solution is an advantage. The actual death volume has to be reduced by the displacement volume of the needle but the influence is the same for both cylindrical and conical and therefore is not shown in this calculation.

We are able to form the foot with a thorn such as is required by the geometry of the needle under the adherence of certain measurements.

Vials Index
VMax-Vial
Description
VMax-Vial
with screw & crimp top
© infochroma ag, Chräbelstr. 4, CH-6410 Goldau; Tel: +41 41 748 50 60, info@infochroma.ch