Archive for the ‘Miscellaneous’ Category

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.

World Record Set for Longest Gas Chromatography Retention Time!

My colleague Jaap de Zeeuw holds a Guinness World Record certificate for making and applying the longest GC column ever, 1300m.  That’s quite a feat and I’ve often wondered what the retention times were for that column when you consider the holdup time was probably on the order of hours instead of minutes.  No matter how long the retention times were though on that 1300m GC column, I may have exceeded them on a simple 30m x 0.25mm x 0.25µm Stabilwax, which I’ve been using for a selectivity study conducted by colleagues James Harynuk and Teague McGinitie at University of Alberta.  This work will be presented at the 11th GCxGC Symposium (and 38th International Symposium on Capillary Chromatography) in Riva del Garda, Italy.

The study includes, Rxi-1ms, Rxi-17Sil MS, Rtx-200, and Stabilwax GC columns, which represent a variety of stationary phase polarities and selectivities.  The first 3 have temperature stabilities of 350, 360, and 340°C, respectively, but the Stabilwax only goes to 260°C.  I can chromatograph all of the molecules chosen for the study on the first 3 phases, but when I get to the polycyclic aromatic hydrocarbons (PAHs), some of which are notoriously involatile, I struggle on the Stabilwax.

The first figure below shows the Acquired Sample list for the Stabilwax work, and I purposely started with SV Calibration Mix #5 / 610 PAH Mix because I knew some of the compounds would be hard to elute from the wax GC column.  Well, how about almost impossible to elute?  As you can see in the first chromatogram, even though I had a 40 min final oven temperature hold time at 250°C, none of the PAHs with molecular weights of 252, 276, and 278 eluted.  In chromatogram 2, which is run 3 from the queue, I see carryover peaks for 252 PAHs (benzofluoranthenes, benzo[a]pyrene), but still didn’t get complete elution of the PAHs even though I pushed the final hold time up to 90 min.  OK, this isn’t going so well, this part of the selectivity study…

Eventually, after uninstalling the Stabilwax column, putting it in my office for a few days, and then reinstalling it to run different standards, I finally saw the first 276 and 278 PAHs eluting as massively broad peaks, almost 5 min wide at base.  When I calculate retention time (yeah, sure, I included the time in my office!) for indeno[1,2,3-cd]pyrene, it’s 7.25 days!

Your move, Jaap…

Sample Queue


Chro SV-5 01


Chro SV-5 03


Chro 8270-2 PAH carryover

Release of dangerous substances from Construction products – The Difficulty of harmonizing Methods in Europe

Indoor air quality is as important for human health as quality of food or drinking water. Most of us are spending a high percentage of our living time in closed rooms. If, during work time, we are exposed to concentrations of dangerous substances, released from the working process, measurements are mandatory which ensures that these concentrations do not exceed given MAC-values (maximum allowable concentration). At home we may be exposed to a large number of substances known as carcinogenic or toxic, which are released from different construction products like paints, glue, sealing materials, or carpets and other floor coverings. Despite the large amount of potentially dangerous substances around us in our homes, no regulation requires regular measurements. A suitable way out of this problem is to regulate the construction products prior to their introduction to the market.

In Europe the CE-mark of conformity is mandatory for every manufacturer or importer of a certain product, if this product is to be introduced into the European market. Herein the manufacturer or importer claims the product is developed and manufactured in accordance with the product related European Norms (EN).

The basic description in how construction products should be handled is part of the European Legislative Process. The European Community has governed the certification of construction products by the “Construction Products Regulation” (CPR – former CPD – Construction Products Directive).

CPR defines basic requirements for construction works (BWR3) as follows:

“…the construction works must be designed and built in such a way that they will, throughout their life cycle, not be a threat to the hygiene or health and safety of their workers, occupants or neighbours, nor have an exceedingly high impact, over their entire life cycle, on the environmental quality or on the climate, during their construction, use and demolition, in particular as a result of any of the following

a) the giving-off of toxic gas;
b) the emission of dangerous substances, VOC, greenhouse gases or dangerous particles into indoor or outdoor air;
c) the emission of dangerous radiation;
d) the release of dangerous substances into ground water, marine waters, surface waters, or soil;
e) the release of dangerous substances into drinking water or substances which have an otherwise negative impact on drinking water;
f) faulty discharge of waste water, emission of flue gases or faulty disposal of solid or liquid waste;
g) dampness in parts of the construction works or on surfaces within the construction works.”

Based on this CPR regulation European Norms are developed by Technical Commitees (TC) related to a specific construction product, e.g. CEN/TC 134 “Resilient, textile and laminate floor coverings”, responsible for “Standardization of definitions, requirements, classification and test methods and provision of guidance documents and reports for resilient and textile floor coverings and for laminated floor coverings”.

It is the task of these TC’s to harmonize existing National Normings and develop a harmonized European Norm (hEN) which specifies the named construction products. The CPR/BWR3 is one of the great challenges to the TCs which also have to harmonize national ideas of construction products with these basic requirements.

Being part of such a complicated process, TCs often develop their own methods and standards, even if similar behaviours are surveyed, e.g. the release of Volatile Organic Compounds from different construction products. Since indoor air quality is determined by the behaviour of all different construction products, one of the big challenges for the European Community is to standardize tests and analysis methods between different TCs. This process is called “Horizontal Standardization”.

The process of Horizontal Standardization starts with Expert Groups of the Member States of the European Union, organized in one of the Commission’s “Directorate-General (DG)”. For the regulation of construction products the most involved Directorate-General would be the DG Enterprise and Industry. However, since we are talking about risks stemming from the release of dangerous substances into the environment, the DG Environment and possibly also the DG Energy have to be involved.

These DGs will decide to give a mandate to the European Norming Commission (CEN), and then to a leading TC, to horizontally standardize the norms describing the different construction products. The mandate for Horizontal Standardization and Harmonization of the considered European Norms (EN) for construction products is named M/366 and it was assigned to the CEN/TC 351, responsible for construction products.

The full name of this mandate is: “Horizontal complement to the mandates to CEN/CENELEC concerning the execution of standardization work for the development of horizontally standardized assessment methods for harmonised approaches relating to dangerous substances under the Construction Products Directive (CPD)”

During this process of Horizontal Standardization and Harmonization the people in charge had to handle:

  • Over 65 product TCs and environmental TCs
  • European Commission: SCC, DG Enterprise, DG Environment
  • 27 Member States / 30 CEN Members
  • Industry, industrial sectors
  • CEN bodies: CMC, CSN, CSNPE, SABE
  • Regulators, experts from various fields
  • Liaisons with interest groups

To keep workload of the acting people manageable, TC 351 has decided to divide the work into 5 Working Groups (WG).

Working group
CEN/TC 351/WG 1 Release from construction products into soil, ground water and surface water
CEN/TC 351/WG 2 Emissions from construction products into indoor air
CEN/TC 351/WG 3 Radiation from construction products
CEN/TC 351/WG 4 Terminology
CEN/TC 351/WG 5 Content and eluate analysis in construction products

Table 1: Technical Bodies of CEN/TC 351 – taken from the homepage of CEN – European Committee for Standardization. HTTP://

As a company of chromatographers, Restek is mostly interested in the results of the Working Group 2 (WG 2) “Emission into Indoor Air” and how the classification of construction products are realized for this approach.

During the last years WG 2 has developed a horizontal testing standard for the emission of volatile compounds from construction products. This CEN/TS 16516 now has to be adopted into the product standardizations by the TCs of the specific construction products. Until now the CEN/TS 16516 is not a European Norm, but a Technical Specification (TS), seen as a preliminary stage of a European Norm. The complete norming process is promised to be finished during 2015/16.

The CEN/TS 16516 is described as follows:

“This Technical Specification specifies a horizontal reference method for the determination of emissions of regulated dangerous substances from construction products into indoor air. This method is applicable to volatile organic compounds, semi-volatile organic compounds, and volatile aldehydes. It is based on the use of a test chamber and subsequent analysis of the organic compounds by GC-MS or HPLC.” The quoted text was cited from the CEN Homepage.

One of the big International Laboratory Associations, the Eurofins Group, announced in January 2014: “CEN/TS 16516 will become the “mother of all VOC emissions testing standards” for construction products in Europe within the next months and years. It will form the basis of VOC emissions testing for CE marking as soon as the criteria for CE marking have been specified in near future.” (Eurofins Homepage).

Unfortunately, in Europe the situation for the regulation of products is a bit more complicated than in other economic areas. Responsiblity for the risk assessment of dangerous substances lie with the National Authorities (e.g. for Germany the National Authority is the Federal Institute for Risk Assessment (BfR) in Berlin).

National Authorities may choose different ways of assessing the risk of the release of dangerous substances from construction products. Up to now several quality rating systems are established in Europe. The following parameters are included for testing:

Formaldehyde and acetaldehyde are mandatory for all EU countries. In France a “Compulsory VOC emissions labelling” is installed with 10 VOCs and TVOC (Total Volatile Organic compounds) as basic testing values to run into an ABCD label, classifying the construction products. Germany bases his classifying system on a List of more than 200 compounds, published by the Committee for Health-Related Evaluation of Building Products (AgBB), latest version in 2012. This LCI-list (Lowest Concentration of Interest) includes VOC and SVOC compounds as well as a maximum TVOC value. The Belgium classifying system, at the moment, is referring to another list, the EU-LCI-list, including 177 VOC and SVOC compounds of interest. All other EU countries, at the moment, do not have any classification system.

In a country without regulation on VOC emissions, a CE marked product can be sold with the NPD option (“no performance declared”), in a country with existing regulation on VOC emissions this product only can be marked with a CE label if the declaration of performance includes VOC emissions test data, in conformity with the national regulation.

Regarding the production of reference materials, the situation is not easy to overcome. A certified Multi Parameter Reference Material Kit, as Restek has done for VOCs in water or Pesticides in Food (MegaMix) could be possible but a clear European strategy about which components should be targeted and how many countries will participate on a common European LCI list is needed.

Separating and determining VOC’s and SVOC’s out of air is a well-known and well used application at Restek. If someone needs assistance, everybody is welcome to discuss their challenges with our Technical Service group.


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







How Dirty Are You? Part 1 Parafilm®…the Answers!



Please take a look at the question I posed about Parafilm® and potential contamination.

A quick reminder…I was warned against using Parafilm® because it would cause contamination. At the time, I was working with acetonitrile and I didn’t think there was much risk of contamination. We decided to perform a quick test to see what would happen if we exposed Parafilm® to different solvents. See the original blog for more details.

There were two questions posed in the last blog…

1. Which solvent produced the most intense signal?

2. Which solvent produced the smallest signal?

The solvents tested included (in alphabetical order) acetone, acetonitrile, ethyl acetate, hexane, isopropyl alcohol, methanol, methylene chloride and toluene.

The Answers…Drum roll please…

Hexane produced the most intense signal.

Acetonitrile produced the least intense signal.



Although soaking Parafilm® in solvent is not typical, it does show that background contamination can occur if Parafilm® contacts solvents. Characteristically, hydrocarbon type contamination is observed as in the chromatograms below. My initial thought was to look at solvent polarity and assume that Parafilm® would be most soluble in a non-polar solvent. Polarity was also a key consideration of the people who sent me their answers. (THANK YOU for the emails!) One person actually used polarity and dielectric permittivity (ɛ). I have to confess I had to google dielectric permittivity because I forgot what it was exactly.




Signal intensity, generally but not strictly, follows the polarity (and dielectic constants which had a similar trend as polarity) of the solvents tested with the most non-polar solvents producing the most intense signals. Also, you will see from the chromatograms below that hexane, methylene chloride and toluene show high contamination at very similar levels. After these three solvents, there is a significant decline in contamination. Methanol and acetonitrile produce the lowest signals – about two orders of magnitude lower than hexane, methylene chloride and toluene.




example chromatogram

example chromatogram





Samples of solvents post- Parafilm® soak were tested with a 50 ppm hydrocarbon standard as a signal reference, see the blue dashed line in each chromatogram. Click on the image to the right for a closer view.







Here are the chromatograms from highest to lowest contamination signal…

hexane 50ppm

MeCl2 50ppm

toluene 50ppm

ethyl acetate 50ppm

acetone 50ppm

IPA 50ppm

MeOH 50ppm

ACN 50ppm




It is difficult to see the level of contamination for these more polar solvents…so let’s take a closer look.

For solvents that produced relatively low signal, the y-axis scale is changed and 5 and 0.5 ppm hydrocarbon standards were used for reference levels.



parafilm cgrams 5 05 ppm




If you didn’t guess the correct answers, don’t worry, you aren’t alone. Only 8% of people had the correct answers.
My bet was on methylene chloride producing the highest signal and methanol producing the lowest…so i was close.

Remember that you are unlikely to see contamination from Parafilm® especially if there is no or little actual contact with your sample. But be aware that if contact with your sample does occur non-polar solvents can produce significant contamination.

At least we know what the contamination chromatogram looks like and this will likely be the most useful thing I have learned from this experiment… especially as we continue to use increasingly sensitive detectors that can easily detect trace level contamination.




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).


How Dirty Are You? Part 1 Parafilm®…Take a Quiz!


image from

A couple of years ago I gave a presentation about general lab practices.

How dirty are you? Common lab practices that may impact data quality are examined using various gas chromatography and gas chromatography-mass spectrometry techniques. (look for this presentation on the last How Dirty are You? blog…i cant give you the answers now!)

We work in very close quarters in our lab…we have grown in staff but not in space. This means that I sometimes have to squeeze into one of our hoods with a colleague or two.  I started to notice little differences in the way each person goes about their work. For example, some people always place syringes on a clean paper towel while others don’t or some people will use a Pasteur pipette more than once while some won’t. I realized that I have lab habits that could be more ritualistic than meaningful.

One of the funniest things is rinsing a glass syringe- everyone has a number and a story- but we will get to that in a future “How Dirty Are You?” blog. There will be at least six subjects covered in this blog series. These will discuss other sources of contamination like gloves, syringes, pipet bulbs, tubing…etc.  I will also post the percent of correct answers from the first audience to participate (FPRW 2012 Restek Vendor Seminar) and include answers I receive via email.



parafilmThis blog is about Parafilm®…personally, I love the stuff and have used it for years. One day a colleague of mine instructed to never use “that stuff” because it will contaminate your sample. Really, I thought…I have used it forever and it doesn’t seem like it would be too soluble in acetonitrile. I just couldn’t believe it. So I thought, “Heck, I am an analytical chemist, why don’t I test it?” Of course my colleagues were on board so this is what we did.



Parafilm® is often used to store samples or temporarily top open containers like beakers so to mimic a worst case scenario, we soaked approximately 25 mg Parafilm® directly in 3 mL of solvent for 60 minutes. The image below shows the eight solvents we tested and the Parafilm® submerged in the each vial.



After the 60 minute soak time, we tested each sample using GC-FID. We used a hydrocarbon standard for signal intensity reference. As a teaser, I will tell you that the highest contamination peak was about 3 times higher than our 50 ppm hydrocarbon peak!!

























See the Answers!



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).


Chemical Reference Standards; don’t just snap and pour

I still remember the first time I tried to prepare a chemical standard (back in the 80’s).  I failed miserably.  It was my first laboratory job and I was asked to snap open recently purchased ampules and dilute them to some concentration (which I don’t remember) for our 8270 analysis.  Back in those days there were no MegaMix® solutions, so I probably had eight or more ampules to dilute.  I double-checked my calculations, filled-out our laboratory notebook, measured the methylene chloride I was going to dilute the ampuled solutions into, and began snapping and pouring.  About halfway through the procedure I had a co-worker stop me and ask what I was doing.  Was this a trick question?  I was focused on the task and making good time, so I told him to back off (which he did).


Then the manager showed up to let me know why I was so rudely interrupted by my coworker.  He explained that just because the ampule listed 1mL on the label as the volume, chemical reference standard manufacturers actually put more than the listed volume into each ampule, so one needed to measure the volume removed and not assume the contents were exactly 1mL.  In summary, I learned that day that the proper process was to snap the ampule and precisely remove the volume of the solution needed for dilution.  The remaining contents should be immediately transferred into a screw-cap or crimp-cap vial and placed in storage according to the recommendations of the manufacturer.

So why did I write this post?  This week I spoke to two customers who were snapping and pouring.  I thought if they didn’t know the correct procedure, then maybe I should write a post to tell others who also may not know.

For additional information about our MegaMix® solutions and what separates our chemical reference standards from our competitors, please see the links below.  Thanks for reading.

8270 MegaMix®

8260B MegaMix®

World-Class Certified Reference Materials (CRMs) 10 CRITICAL STEPS