Assistance Needed On Reducing Union Zero Dead Volume

[ooiuniscience]

Dear all and respective expert,

Good days to everyone!

Does anyone have idea to share experience on using Reducing Union with zero dead volume (click below link & refer to 2nd page?
http://www.swagelok.com/downloads/WebCa ... 02-173.PDF

1. For reducing union of low volume and zero volume in page 2 of attachment, it comes with a "VARIETY TYPES OF FRITS". and it seems like it can give zero dead volume for my sample (label with light blue). Is it true?

2. But i heard the purpose is frit is to filter the particle. Is there any function for this frit in addtional to this (such as reduce the dead volume for my gas sample???)P/s let me know.

3. If i buy SS-200-6-1ZV, base on your experience, is it suit my appliction as i tends to reduce dead volume for my sample. But i wondering it will increase the pressure for my sample to pass through it since the frit have a very small pore size (in micrometer range as shown in the bottom table of page 2).

Hopefully anyone of you can shed a light on this.

Jeff Ooi

[uzman]

The important point is , do you really need a ZDV union ?

Practically , it does not make a sensable difference on chromatograms ; unless you deal with 0.1µl or less .

If it is important for you , you must also deal with the tubing lenghts , inner diameters etc, and these are more important than the ZDV union.

In order to make a ZDV connections , the end of tubing which you will use must have a very flat surface and must be cut perpendicular , otherwise you have more dead volume at the bottom of the connection than the union itself.

During fixing the tubing , the tube must touch to the surface of the frit , and tightened in this position.

Regarding the choice of frits , it depends on what you will like to '' hold ''.
The function of the frit is to prevent something to escape , mostly the chromatographic particles , so you will chose it smaller than the smallest particle size used.

[chromatographer1]

SS frit in a union ?

Why would you need this?

You have been very silent about WHAT you are doing. This actually has great bearing on answering any questions you have posed.

I can only assume you are doing some strange GC work.

Again I ask, why would you need a zero union with a frit?

Rod

[ooiuniscience]

Dear Uzman chromatographer1,

Thanks for your patience in explaining all this out. I truly appreciate it.

I'm producing hydrogen from water splitting reaction. The H2 gas generated will be transferred into GC by using peristaltic pump. Minimum H2 gas range is 50ppm. Hence, i choose zero volume fitting to avoid loss of sample. But if i choose SS-400-6-1ZV with nominal pore size 25, i worry it will give very high pressure for sample to go in. OR i actually do not need this ZDV fitting?

P/s correct me.

Jeff

[Peter Apps]

The fittings that you are referring to are designed to go at the end of packed columns - the frit is there to hold the packing in place. Unless you have particles in your gas stream you do not need a frit, and you can use an ordinary Swagelok compression fitting - if they are connected properly the internal volumes in this type of fitting are not "dead" since they are swept by the gas flow.

Peter

[chromatographer1]

The frit will give you little back pressure as long as no particles will clog it up.

There are other unions (Valco) which have minimal internal volume using a 0.010 inch ID passageway in the union.

Call, Swagelock and ask them if they have a union without the frit if you are concerned.

best wishes,

Rod

[ooiuniscience]

Thanks Chromatographer1, Peter Apps and Uzman,

All your inputs are truly important for my work.

Have a great day! Thanks once again for all of you who response. We truly appreciate your help.

Jeff