Author Archive

Need help in selecting replacement weldments and shell weldments for your Agilent 5890/6850/6890 GC?

When you need a replacement weldment and/or shell weldment for your Agilent 5890/6850/6890 GC, we have the parts. However, selecting the correct catalog numbers can be a little confusing for many of us.  As a result, I decided to try and simplify the selection process below.  I hope you find it helpful.


5890 Weldment catalog numbers are 20265 for stainless and 20267 for Siltek –Treated.




5890 Shell Weldment catalog numbers are 20266 for stainless and 20268 for Siltek-Treated.






6850 & 6890 Weldment:  If your GC has one of the split vent traps shown below (Restek kit 23031, commonly called large canister filter),




and your instrument does have electronic pressure control (EPC), then the associated Restek weldment replacements are 22686 for stainless and 22670 for Siltek-Treated.




If your 6850 and/or 6890 GC has a split vent trap like shown below (Restek 22820, sometimes called a split vent pencil trap or chemical trap),




and your 6850 and/or 6890 does not have EPC, then the weldment catalog numbers are 20265 for stainless and 20267 for Siltek-Treated.  Please note that these are the same weldments used on the 5890 injection ports.


If your 6850 and/or 6890 GC has a split vent trap like shown above (Restek 22820), but it does have EPC, then the Restek weldment replacements are 22674 for stainless and 22672 for Siltek-Treated.




6850 & 6890 Shell Weldment catalog numbers are 22673 for stainless and 22671 for Siltek-Treated.



Did I just break my hydrocarbon trap (22012 and/or 22013)?

Once in a while we (tech service) get a call from a customer who went to refill their hydrocarbon trap (Restek #’s 22012 & 22013) and noticed that when they turn the nut shown below by the red arrow, that the end-cap (shown by the blue arrow) is the part which turns.  It was designed this way to make the refill process much easier, and is not a result of a defect, or anything being broken.

Now that you are aware of this feature, the instruction sheet may make a little more sense.   A few other things you may not know about these traps; they have a black anodized aluminum body, contain Viton O-rings, and have nickel-plated brass end fittings.



SDS (MSDS) for VICI® Mat/Sen® Gas-Specific Purifier Modules

Once in a while we (tech service) get asked for a SDS (MSDS) for VICI® Mat/Sen® Gas-Specific Purifier Modules.  Even though we are not required to provide one with the product, sometimes customers need to know their contents.  Simply click on the links below of the appropriate purifier to obtain your SDS (MSDS).


For the Helium, Hydrogen, and Nitrogen Purifier Module  Helium, Hydrogen, and Nitrogen Purifiers

For the Air Module   Air Purifier


Here are a few other related links (if interested).

Contents inside your baseplate trap

Changes are coming to the MSDS; um, I mean the SDS


What is the difference between Restek nitrogen generators which use electricity and those which do not?

You may have reviewed our product webpage for Parker Balston® Nitrogen Gas Generators for LC-MS and noticed that is states: Models N2-04, N2-14, N2-22, and N2-35 require no electricity.  So why don’t these models require electricity but models N2-14A, N2-22A, and N2-35A do?

The simple answer is: those which use electricity have an oxygen sensor and audible alarm built into them, and the others don’t.  The oxygen sensor monitors the oxygen content in the nitrogen process stream.  When the oxygen level increases above the set-point, an alarm will sound letting you know that gas output does not meet purity specifications.




Some other things you may not know about the nitrogen generators we sell:


22129 has a built-in air compressor.

*  If you are going to use nitrogen for GC carrier gas, choose an Ultra-High Purity generator like 21653 and 21654.

*  We also sell maintenance kits.

  Maintenance Kits for Parker Balston® Nitrogen Gas Generators for LC-MS

  Annual Maintenance Kits for Parker Balston® Nitrogen Gas Generators




Dimensions of NORM-JECT® syringes

We often get asked for dimensions of our NORM-JECT® syringes.  As a result, I decided to take the information tech service has been provided and put it in a convenient place for our customers.  Below is the information for Restek part #’s 22766 through 22778.  For those of you who need it, I hope you find this information useful.


Fatty Acid Methyl Esters (FAMES) – converting % by weight to µg/mL

The first time I was asked by a customer about how to convert % by weight of one of our FAME reference standards to µg/mL, I needed to ask for some help.  Because we (tech service) occasionally get asked this question, I thought I would show the calculation in a post.


Let’s take Restek catalog number 35077 as an example.  The overall concentration of this Food Industry FAME Mix is 30mg/mL.   Individual compound concentrations range from 2 to 6% by weight.   So what are the individual compound concentrations in µg/mL?   I’m not going to list them all, but rather show you how to perform this calculation.

We list the first compound as C4:0 and at 4% by weight.  Since the total concentration of 35077 is 30mg/mL, to determine the concentration of C4:0 in µg/mL:

4/100 x 30mg/mL = 0.04 x 30mg/mL = 1.2mg/mL

To convert to µg/mL:  1.2mg/mL x 1000µg/mg = 1200µg/mL




If you purchase a neat standard like 35066, then there will be one extra step to obtaining the final answer.   This catalog number contains approximately 100mg.  For the sake of simplicity, let’s say you remove exactly 100mg and dissolve this material into 10mL of methylene chloride.  This will produce a solution with a concentration of 10mg/mL.   Once again, I will use the first listed compound (C14:0 in this case) for an example calculation.

C14:0 is in the neat material at 6% by weight.  Since the total concentration of the solution you prepared is at 10mg/mL:

6/100 x 10mg/mL = 0.06 x 10mg/mL = 0.6mg/mL

To convert to µg/mL:  0.6mg/mL x 1000µg/mg = 600µg/mL


I hope you have found these examples helpful the next time you need to perform similar calculations.  Thanks for reading.

Contents inside your baseplate trap

We often get asked in tech service for a list of materials contained inside our baseplate traps from customers who are concerned about disposal regulations.  They have read our FAQ How do I dispose of used gas traps or filters?, but before contacting their waste disposal company, a list of the trap contents is requested.  Normally this information would be contained in a SDS, but the traps we sell are considered “Articles”, they do not require that one be sent with the product (for more information, please see Changes are coming to the MSDS; um, I mean the SDS).

So without further ado, below is what is contained in the following Restek catalog numbers.

Notes:  g = grams.  CAS = Chemical Abstract Service


# 22020  and # 21983 Replacement Triple Gas Filter (removes oxygen, moisture, and hydrocarbons). 

Includes Helium-Specific Triple Filter.



# 22022  Replacement Fuel Gas Filter



# 22028  Ultra-High Capacity Moisture Filter



# 22029  Ultra-High Capacity Oxygen Filter



# 22030  Ultra-High Capacity Hydrocarbon Filter







Troubleshooting GC Syringe Issues – Part 2

In an earlier post titled Troubleshooting GC Syringe Issues, I discussed several things to try if sticking plungers are the problem.  In this post, I’ll discuss what to do if the syringe is not pulling up the sample properly (or at all).



So what can cause a syringe to have problems pulling up a sample?


The sample is too viscous.

If your sample is viscous, slow the plunger draw speed.  Many autosamplers have this functionality.

If this still doesn’t solve the issue, you may need to dilute your sample.


The syringe needle is plugged, or partially plugged.

Find out what is plugging your syringe needle.  Is it the sample or septa?

If it is particles in your sample, you may need to add a filtering step before injecting.  Sample Filtration

If you discover it is a piece of septum plugging your needle, try a different needle point style (Pt style #5 with side-hole are the least likely to plug).  Syringe Basics.

Pt Style 5




The plunger is not making a good seal with the syringe barrel.

How worn is the syringe?

Eventually the plunger to barrel sealing performance of syringes degrades as it gets older and worn-out.  This is especially true when using Gas-Tight syringes which have PTFE-tipped plungers.

Most syringe manufacturers recommend that you do not use a plunger from one syringe in another (unless using Gas-Tight syringes where plungers are usually interchangeable).


There is a leak between the needle and barrel.

If using a removable needle syringe, make sure the PTFE seal between the needle and barrel is installed properly and not worn out.

If using a fixed needle syringe, verify that the cement holding the needle to the barrel hasn’t degraded.


The autosampler is not working properly.

Watch the autosampler as it tries to inject the sample.  Is the autosampler programmed properly?  Does it actually penetrate the sample vial deep enough to withdraw an aliquot?  Does the autosampler actually lift the plunger?


Hopefully one of these suggestions will help you out the next time your syringe is not pulling up a sample.  Thanks for reading.

Understanding packed column mesh size ranges

If you have ever ordered a packed column, you are aware that mesh size of the solid support (packing) is one of the specifications you will need to know.  But have you ever wondered what mesh size actually means?

To find the answer, let’s look at the products and process.  The necessary products are ASTM Certified Standard Brass (or Stainless Steel) Test Sieves*, like shown below, and of course, the material to be screened.

* Depending upon the specific procedure, Compliance, Inspection or Calibration test sieves may be needed.



Photo from Fisher Scientific website


In order to obtain particles within specific a mesh size range, two screens are used in addition to a cover and a pan.  The pan is placed on the bottom, then the top and bottom screens are placed on the pan.  The top screen will have larger openings than the bottom screen.

Let’s assume in this example that the top screen is 80 mesh, which means that for every linear inch of screen, there are 80 little square openings.  Let’s also assume the bottom screen is 100 mesh, meaning that there are 100 little square openings for each linear inch of screen.  As you can guess, the openings in the 100 mesh screen are smaller than in the 80 mesh screen.  If interested in reviewing additional sieve screen specifications, click here.

The bulk material is loaded on the top screen, the cover is placed on top, and the sieves are shaken (manually or mechanically) side-to-side while gently tapped.  The particles which are small enough pass through the 80 mesh screen fall onto the 100 mesh screen, and if the particles are small enough, they also pass through the 100 mesh screen and are caught in the pan (these particles are referred to as “fines”).  The particles which are caught on the 100 mesh screen are the desired size, and are referred to as 80/100 mesh size particles.

You will notice that many test sieves are often designated using the term microns (µm) instead of mesh.  The relationship between these two terms can be found in this link.

So now that you know about particle mesh size, how does choosing a different range affect your analysis?  Generally speaking, using smaller particles (100/120 mesh) rather than larger particles (80/100 mesh) of the same packing in the same dimension column will provide more separation power (theoretical plates), but carrier gas head pressure will need be higher (to maintain constant flow rates) and longer analysis times are common (especially for isothermal analysis).


Need a replacement AC Adaptor/Charger for your Restek Leak Detector?

We all misplace items once in a while.  If you have misplaced your leak detector AC adaptor/charger, don’t worry, we sell replacements.  If you own leak detector catalog number 22655:



The replacement AC adaptor/charger catalog number is 22653.




We also sell a car charger for this leak detector.  It is catalog number 22652.

22652.jpg (2)




In addition, we sell the AC Adaptor/charger for the previous model leak detector 22839.



The replacement AC adaptor/charger catalog number for 22839 is 563816.


Note:  Some of the older 22839 units may be getting close to needing their batteries replaced.  When your batteries will no longer charge, or will not hold a charge, you will need to return the unit to Restek for battery replacement.  Call Customer Service for a service repair by ordering catalog number 22839-R (orders cannot be placed for this service using the website).