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Optimzed Microsampling with Chromatography Vials

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Chromatography autosamplers use mostly vials which are 12 x 32 mm in size. These vials can take 1 ml sample. However, if there is only a limited sample volume available or as much sample as possible should be removed from the vial, an optimized solution is needed. A vial that stands without support and keeps the outer dimension so that it can still be used in common autosamplers.

We devolopped three ideal solutions for this problem. To find the right solution for a certain application means to ask one important question. How much sample volume do I have and how much sample do I need for the analysis. The difference between the two, the volume that remains in the vial, we call residual volume. This residual volume defines which vial is needed.

Many vial suppliers advertise the dead volume, the quantity of sample that cannot be withdrawn from the vial; however this volume cannot be defined as simply as that. The insertion depth of the needle, the geometry of the needle, how well the needle hole is covered with sample so that no air is sucked up, all these factors define the dead volume of an application. We find that the definition of the dead volume without the exact specification of those parameters is useless.

We define the volume in the foot of the vial at 4 mm filling level, with the provision that an autosampler needle inserts down to about 1-2 mm above base and that the needle should be covered with 2 mm sample to guarantee a reliable sampling. The actual dead volume of our vials is usually a lot smaller than the residual volume that we publish, yet if an autosampler with side hole needle is used, the published value can also be too small. A regular 12 x 32 mm standard vial for example has a residual volume of 400 µl.

Which one of our 3 microvials should be used?
Our vase vial or V15µ-Vial has the largest volume. It takes 1.5 ml up to it's shoulder and has 15 µl at the foot. Since our vase vial is the most economic solution, we recommend this vial for all applications that go with a residual volume of 15 µl. The vase is also the most versatile vial, it is available with all common closure versions including 8-425 screw top which we call "NM" or "Narrow Mouth" as these vials have a narrow opening. Notabene the vase vial is our very own invention and we patented the form as well as the production process. Now we also produce bigger vase vials, but this will make another news article.

Our first microvial, historically speaking, is the i3µ type with a fused insert that has one base with the outer vial. It's like a vial and insert combination, only that vial and insert are pre-assembled, fused and the insert well centred. The total volume is 350 µl with 10 µl at the foot.

Our latest microvial is the iV2µ type. It's different because the insert wears the head of the vial so that the insert itself is closed. That means no sample can escape into the outer vial. The body of the vial is a simple tube that is fused with the base of the insert. We produce these vials on a one-station machine, we especially developed, a machine that allows us to draw the insert longer and more narrow than is possible with common techniques. The total volume is 250 µl with 8 µl at the foot. The iV2µ is espcially suited for volatile micro samples or gas chromatography applications and rounds our limited volume range off at the bottom.

Part of our service, besides assisting you in the proper choice of vial for your application, is offering a wide selection of closures. We are happy to send you samples so that you can test the vials and closures with your application.