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Don’t forget about your lab’s moisture traps/filters, especially when it’s summer

One of the common issues which arise in laboratories during the summer is moisture in the gas lines. Although I never quite understood how this would happen when using gas cylinders, it does, especially when a manifold system is used, or if the length of tubing from the gas source to the instrument is longer than several feet/meters.  Common observations when this happens are:

  1. Unstable instrument detectors (especially TCDs, HIDs, ECDs and mass specs).
  2. Less than ideal chromatography (shifting retention times, unusual peak shapes, etc.).
  3. Unusual activity issues in the injection port and/or ghost peaks.

 

So what is an inexpensive way to minimize these issues, especially in the summer when many locations experience hot and humid conditions? Install an indicating moisture trap/filter on all gas lines.

 

So how would you know which trap filter would be best for you laboratory? Ask yourself the following questions:

Q1. What is the gas?

Q2. Is the gas line tubing copper or stainless steel?

Q3. What is the maximum gas flow rate the trap/filter may be subjected to?

Q4. What is the maximum gas pressure the trap/filter may be subjected to?

 

Here are my suggestions to aid in trap/filter selection based upon the questions listed above:

S1. Generally speaking, the traps/filters we sell are for use with laboratory grade (high purity) inert gases.  If you plan to use a Restek trap/filter with a corrosive, flammable or reactive gas, email us first at support@restek.com

S2. Most use traps/filters containing brass end-fittings with copper tubing and stainless steel end-fittings with stainless steel tubing.  For additional information on the topic, I suggest you review I need a fitting, but which one?

S3. Published flow rates can vary among manufacturers, so make sure you are aware of exactly what a published value represents.  For example, is the published flow rate the maximum flow rate the trap/filter can handle, or is it the maximum flow rate in which the trap/filter can effectively clean (scrub) the gas?  In the context of this post, what is the maximum gas flow rate through the trap/filter that can effectively remove much of the moisture?

S4. For obvious safety reasons, make sure the published maximum trap/filter pressure is not exceeded.

 

Several of the popular indicating moisture filters are shown below.

 

Indicating Moisture Trap

 

 

Restek Super Clean Ultra-High Capacity Moisture Filter

 

 

Don’t forget the baseplate.

Of course we also sell a wide variety of other filters including non-indicating moisture filters, and others for the removal of oxygen and/or hydrocarbons.   To view all of your options, click on the link below.

http://www.restek.com/Supplies-Accessories/GC-Accessories/Gas-Purification

 

Or for removal of a specific contaminant(s), the links below may be quicker to navigate:

Moisture Removal

Oxygen Removal

Hydrocarbon Removal

Multiple Gas Removal

 

You may also find these links (below) informative. If you have any questions, you may email me directly or technical service at support@restek.com .

 

SDS’s for 22010, 22011, 22014 and 22015 (Indicating Oxygen & Moisture traps/filters)

Several things you may not know about our Super-Clean® Gas Filters

Contents inside your baseplate trap

Indicating Oxygen and Moisture Traps-“Hey, it looks like my trap arrived partially spent”

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

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

Is the column shown on the COA for a chemical reference standard the best column for these compounds?

 

In some cases the answer is “yes”. In most cases the answer is “no”.

 

So why would we choose a column that is not the optimal for a specific standard?

It’s because of the large number of reference standards we sell. Each mix needs to have its own validated method. If we were to test each standard with their own column and/or method, production would slow to a crawl.

 

Stated another way by a product development specialist:

In order to provide certified reference materials, each product manufactured at Restek needs to be analyzed using a validated method.  It is impractical to have an optimized, validated method for each manufactured standard and be able to deliver certified reference materials to our customers that meets their needs in terms of cost and delivery time.

 

Because some customers are not aware of this, most chromatograms contain following statement (printed directly below the chromatogram):

This chromatogram represents a general set of testing conditions chosen for product acceptance. For optimal results in your lab, conditions should be adjusted for your specific instrument, method, and application.

Also keep in mind that we may sell a standard which was designed for a GC method, but actually test it using a HPLC column, and vice versa. An example of this would be Restek #31607 which was designed for EPA Method 8095 (Explosives by Gas Chromatography) but was tested at Restek using HPLC.

 

So how would you know which would be the best column choice? I suggest first looking through our application chromatograms using the online search feature http://www.restek.com/chromatogram/search/

The way I use it is the following: I type in a compound name, followed by a comma, then a space, then another compound name…  For example, if I type methane, ethane, propane, butane the following link shows the results I receive: http://www.restek.com/chromatogram/search?s=type:GC::methane::ethane::propane::butane

 

You can also try ProEZGC http://www.restek.com/proezgc   Please note that this is only for GC columns, and is limited to capillary liquid phase partition (Rtx-1, Rtx-5, Stabilwax, etc…) and not capillary solid phase adsorption (PLOT) or packed or micropacked.

 

In summary, you should not assume that the column and/or instrument method parameters on the chemical reference standard COA are for the optimal analysis of that reference standard. Instead, one of our other references, such as the chromatogram search tool and/or ProEZGC are better choices for choosing the correct column and method parameters.

 

Below are additional links which you may find useful, especially the chromatograms. Thank you for reading.

Industry Pages – Environmental Solutions

Industry Pages – Foods, Flavors & Fragrances Solutions

Industry Pages – Clinical, Forensic & Toxicology Solutions

Industry Pages – Food Safety

Industry Pages – Pharmaceutical Solutions

Industry Pages – Medical Marijuana

Industry Pages – Petrochemical & Chemical Chromatography

 

Cross reference lists for GC columns and other useful links

With everyone in such a hurry these days, when you cannot find what you need in a few minutes, how often do you give up and move onto your next project?   I’m the same way, so when I find a way to group commonly referenced information into one convenient area, I usually do it.  Below is one of these areas if you are trying to find the correct Restek column from a description listed in a method or cross reference another manufacturer’s GC column to a Restek column.  I hope it saves you time like it does for me.

 

GC Column Cross-Reference: Columns by Phase

USP Phase and Support Cross Reference Chart

GC capillary columns for the European Pharmacopoeia methods

1s 5s Waxes Column Cross-Reference Tool

ASTM Petrochemical Method Chromatography Product Guide

Organic Volatile Impurities: Retention Time Index

Can’t find the GC column you are looking for? Try using our Online Tools

Column Selection Poster

Structures for Capillary Column Phases

Upcoming revisions to three wastewater methods reviewed at NEMC 2017

Monday morning, representatives from the EPA’s wastewater office reviewed the significant changes for the three major GC wastewater methods: 608.3, 624.1, and 625.1.

The overarching goals were to modernize the methods and bring the language and QC requirements in line with the methods from the drinking water and hazardous waste offices. The methods have been modified to include capillary columns, and the QC requirements have been updated to reflect this. Maximum calibration RSDs have been dropped to 20% from 35%, and they want to see full list QC spikes.

The most disappointing change is the requirement that the CCV be prepared from a 2nd source. The 500 and 8000 series methods have recently and explicitly moved away from this practice because a 2nd source doesn’t so much verify ICAL stability (precision) as it does accuracy. I’m including the relevant sections for 8270D Rev 5 below:

9.3.2 There must be an initial calibration of the GC/MS system as described in Sec. 11.3. In addition, the initial calibration curve should be verified immediately after performing the standard analyses using a second source standard (prepared using standards different from the calibration standards). The suggested acceptance limits for this initial calibration verification analysis are 70-130%. Alternative acceptance limits may be appropriate based on the desired project-specific DQOs. Quantitative sample analyses should not proceed for those analytes that fail the second source standard initial calibration verification. However, analyses may continue for those analytes that fail the criteria with an understanding these results could be used for screening purpose and would be considered estimated values.

11.4.3 The initial calibration (Sec. 11.3) for each compound of interest should be verified once every twelve hours prior to sample analysis, using the introduction technique and conditions used for samples. This is accomplished by analyzing a calibration standard (containing all the compounds for quantitation) at a concentration either near the midpoint concentration for the calibrating range of the GC/MS or near the action level for the project. The results must be compared against the most recent initial calibration curve and should meet the verification acceptance criteria provided in Secs. 11.4.5 through 11.4.7.

You’ll notice that the ICV acceptance criteria when using a 2nd source is 70-130%, while the daily (or 12 hour) CCV acceptance criteria is ± 20%. This is because the 2nd source brings additional uncertainty.

I’m making the revised methods available for anyone to review.

Method 608.3 – Organochlorine Pesticides and PCBs by GC/HSD

Method 624.1 – Purgeables by GC/MS

Method 625.1 – Base/Neutrals and Acids by GC/MS

A little extra information for installing/conditioning a new packed/micropacked column

Even though we include instruction sheets with most of our packed/micropacked columns which contain enough information for most customers, some customers (many who are new to using packed columns) contact us routinely asking for some additional assistance. As a result, I decided to add some additional information to our current instruction sheets hoping it helps those customers who may benefit from the extra guidance.  I hope you find them useful.

If you have any additional questions or concerns, email me directly or support@restek.com

 

For 1/8″ OD and 3/16″ OD packed   2017 Packed Instructions 2.0mm 3.2mm

For 0.95mm OD and 1/16″ OD micropacked  2017 Micropacked 0.75mm 1mm

 

You may also find these links useful.

Micropacked Columns: 0.53mm ID Instruction Sheet (PDF)

Molecular Sieve 5A & 13X packed columns – Installation / Conditioning / Helpful Hints

ShinCarbon columns – Installation / Conditioning / Helpful Hints

How do I condition a new packed or micropacked column?

 

Maximum temperatures of packed columns – Porous Polymers

Maximum temperatures of packed columns – Liquid Phases

Maximum temperatures of packed columns – Hydrocarbon Analysis

Maximum temperatures of packed columns – Molecular Sieves

Maximum temperatures of packed columns – Sulfur Gases

 

How to Condition a New Capillary GC Column

PLOT Columns Instruction Sheet (PDF)

Robustness = Confidence

When you see an analytical chemist confidently swagger through the laboratory, you cannot help but ask yourself “is he/she using SPME Arrows?” You say this now, because you know that the SPME Arrow bolsters copious amounts of confidence, which all stems from the increased mechanical robustness and phase volumes, over traditional SPME fibers that is. But let us get a little more detailed about the SPME Arrow size. The following Figure and accompanying Table provides you with everything you need to know:

I will not bore you with discussing the nitty-gritty details, so let us talk about what this all really means. For me it means two things. The first is that I can have a lapse in judgement and decide to close my SPME Arrow as if it were a retractable (clicker) ball-point pen by pushing the Arrow tip down on the laboratory bench. It looks like so after:

But that is okay, because I always carry my Victorinox SwissTool for moments like this. So, I simply bent the Arrow back like this:

Ultimately my Arrow looked like this when I was done:

You will notice I circled the one part of the Arrow. This is the back side of the bend, and during the bend and repair the carbon was clearly discolored in this section. But I still took this very Arrow and racked it up and ran it just like I had done before the bend. And I still had close to 100% collection efficiency. Try that with your Traditional SPME… I dare you!!! When you have this kind of SPME mechanical robustness, you cannot help but strut across the lab. Stay tuned for next time where I talk more about SPME Arrow dimensions and how this corresponds to an increase in sensitivity and even more swagger.

Extractable Petroleum Hydrocarbons (EPH) Method – Why it is important?

Spills and releases of petroleum fuels are the largest source of environmental contamination in the United States. Massachusetts published a method that addresses the need to account for semi-volatile aliphatic and aromatic fractions of gasoline using gas chromatography (GC) analysis and a flame ionization detector (FID). This method was designed to measure the collective concentrations of extractable aliphatic and aromatic petroleum hydrocarbons in water and soil/sediment matrices. Extractable aliphatic hydrocarbons are collectively quantitated within two ranges, C9 – C18 and C19 – C36. Extractable aromatic hydrocarbons are collectively quantitated within the C11 – C22 range.

Aromatic and aliphatic compounds are separated from each other by processing the sample through silica gel cartridges. The extracts are then analyzed using two separate calibrations. The reason for this stems from data suggesting that aromatic compounds are more toxic than aliphatic compounds. This approach, known as Extractable Petroleum Hydrocarbons (EPH) Method, characterizes sites according to their toxicity. Because this method is unique in its ability to determine human health hazards, and yet can still be used to calculate diesel range organics; it has been adopted by other states in the US and in Canadian provinces.

Resprep EPH Fractionation SPE Cartridges (cat # 25859) provide method-specific performance for EPH analysis of soil and water samples through complete separation of aliphatic and aromatic compounds into distinct fractions, while providing extractable background levels guaranteed to fall under the strict reporting limits of Massachusetts and New Jersey EPH methods. Restek’s newly optimized silica gel cartridges have superior lot-to-lot reproducibility and storage stability ensured by rigorous QC testing and moisture-resistant packaging. Resprep EPH Fractionation SPE Cartridges from Restek are manufactured in a strictly controlled environment with the simple goal of giving you consistent results – every day, every time. Resprep cartridges provide easy, reproducible, and guaranteed EPH analysis.

The fractionation process is very critical to accurately determine the amount of aliphatic versus aromatic compounds. As shown in Figure 1, the fractionation of aliphatic compounds includes C9 – C36 and the surrogate 1-Chlorooctadecane (COD). COD is a good marker for the end of the aliphatic range. The beginning of the aromatic range starts a couple milliliters later with the first compound, 2-Methylnaphthalene, starting to elute.

The importance of a reproducible and background free silica gel cartridge will be shown in the next segments of this EPH blog series.

Does that SPME Arrow come with a free lunch?

Here at Restek our company has a core value referred to as “In the Light.” For me, I like to think of it as no skeletons in the closet. So, time for me to shine a little light. I already introduced you to the SPME Arrow. I also addressed the SPME Arrow’s larger diameter and if there are any associated issues of septa coring. Today I reveal how much lunch costs.

As Hailey pointed out last time, the SPME Arrow has a larger sheath. With only one exception, all of the SPME Arrows have an outside diameter of 1.1 mm. We also have a 1.5 mm Arrow which sports 250 µm of PDMS. To put things in perspective, a traditional SPME fiber has an outside diameter of ~0.63 mm. So, in order to take advantage of the SPME Arrow’s mechanical ruggedness and increased phase volumes, you will have to install a GC Inlet Conversion Kit. Obviously, we have these available for you. In addition, your traditional SPME fiber holder will not work with the SPME Arrow. So you will have to use an appropriate SPME holder. And finally, if you are using a “rail” system (e.g., Gerstel MPS) on your GC, you will have to contact your rail manufacturer to secure an appropriate set-up for the SPME Arrow.

So there you have it… that is the catch! Relatively painless in my opinion. Especially when I know you have a drawer full of these:

It is important to keep in mind that these conversion kits do not render your inlet SPME Arrow only. You can continue to use the same inlet as usual for everything else. The problem is that the original inlet on your GC can not accommodate the increased SPME Arrow diameter.

Excellent question Hailey!!!

Last time, I told you I hunt for organic compounds with SPME Arrows, as opposed to the traditional SPME fibers, because I greatly appreciate the mechanical robustness and increased phase volumes afforded by the SPME Arrow. That blog has since received the following excellent comment/question from Hailey: The “sheath” part of the Arrow looks to be much thicker than the traditional setup; is septum coring an issue when injecting manually into a GC?

I thought this warranted the current blog. So first off, let me start by saying Hailey is spot on with her observation of the increased sheath. I plan to talk more about dimensions in a future blog, but for now you should know that everything but the hub (i.e., the screw end) on a SPME Arrow is bigger than a traditional SPME fiber. As my one colleague would say, the SPME Arrow is “heavy duty!” But if we take a look at the following picture, you will notice the SPME Arrow (left side) has an arrow-like tip, from which it garners its name.

This arrow tip accomplishes the following 2 things:

  1. Facilitates the smooth (i.e., core-free) penetration of vial and gc septa.
  2. Acts as a cap when the Arrow is retracted, thereby protecting the phase from any contamination.

You will also notice from the above picture that the traditional SPME fiber (right side) has an open-ended syringe-like tip, which is just begging to grab a hold of some septum and do some coring. So, truth is Hailey, we have more coring issues with traditional SPME fibers than the SPME Arrow.

BUT… like my father always said: a picture is worth a thousand words. So, let us take a look at the following septum, which has received over 150 injections from a SPME Arrow.

Here is the top side:

Here is the bottom side:

Do you see any coring? I do not! But let us take a closer look. The following picture is the same septum, but with me applying pressure:

When I apply pressure to the septum what you see is what I describe as a slit. The SPME Arrow’s tip appears to cut (not core) the septum and make its own “duckbill-like” lips, something you might be familiar with on a Merlin Microseal.

So Hailey… I greatly appreciate your question, as you touched on an excellent topic that I am sure other potential end users will be asking as well. Oh… the short answer to your question is “NO.” And yes, my fiancée says I tend to get a little long-winded.

 

 

I hunt with arrows… SPME that is!

When you say “I hunt with arrows” in central PA, you better be prepared for a long conversation about whitetail deer. So, I better clarify that I am talking about hunting for organic compounds with a SPME Arrow. What is all this I am talking about?

Time for a brief history lesson: Janusz Pawliszyn (University of Waterloo) developed solid phase microextraction (SPME) and published the first article on the technology back in 1990. After filing a patent on SPME fibers, the technology was later licensed to Supelco. The 17-year patent meant the following two things: 1. No one else could offer traditional SPME fibers and 2. No one could make any improvements to the technology. However, now that the patent has expired, Restek is able to offer traditional SPME fibers. In case you have not been paying attention to Restek’s product portfolio (not sure why not), we have been offering traditional Solid Phase Microextraction (SPME) fibers since the summer of 2016. A nice addition to our product offering; however, nothing incredibly revolutionary.

As I already told you, SPME technology has seen no improvements in the last two decades. BUT (bold and capitalized, so time to pay attention)… now Restek can finally offer something new and exciting. Cue the Restek PAL SPME Arrow! The SPME Arrow was designed to overcome the following two most significant disadvantages associated with traditional SPME fibers: 1. Limited mechanical robustness and 2. Small phase volumes. If you have been using traditional SPME fibers, then you know exactly what I am speaking of. In fact, I know you feel the following pain:

You sneeze on a traditional SPME fiber and the thing is bent. Now let us take a look at a SPME Arrow:

Here is a better image to give you a direct comparison between traditional and Arrow SPMEs:

 

Right off the bat you will notice the increased size of the SPME Arrow, which results in increased mechanical stability and phase volumes. All of which we can dive into next time. So stay tuned to this multi-part blog series, where I break down in detail what a SPME Arrow is and what kind of performance  you can expect from a SPME Arrow.