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Trans fatty acids analysis part 2: Let’s look at actual samples with incurred TFAs

In my previous blog, I’ve tried and failed to acquire a sample that contained any trans fatty acids (TFAs). While this is a great news for everyone’s health, the scientist in me was somewhat disappointed. That’s why I first decided to cheat a little bit and look at different TFAs – ruminant TFAs. Ruminant TFAs are products of bacterial metabolism of polyunsaturated fatty acids in the rumen of cattle, sheep or goats, contributing up to 6% of total fat.1 They are present in both dairy products and meat. The major difference between artificial and ruminant TFAs is their distribution. Partial hydrogenation produces TFAs with almost Gaussian distribution, with highest abundance for trans-9 C18:1, while ruminant bacteria skews the distribution towards for trans-11 C18:1 (up to 42 wt%, Fig. 1). It’s also noteworthy that trans-C16:1 can contribute up to 20% of ruminant fats but it is not present in partially hydrogenated oils unless they originate in marine oil.1

Figure 1: Distribution of trans-C18:1 isomers. Adapted from Stender et al.1

The obvious choice for analysis was a dairy product with the most milk fat, i.e. butter. Butter contains up to 80% milk fat, therefore, theoretically, 5% of TFAs (about 0.5 g per serving). In many cases, TFA content is low enough that it doesn’t have to be declared on the label. Our analysis shows the trans-vaccenic acid (C18:1 trans-11), albeit in very small abundance (Fig. 2). While both columns perform well in terms of separating trans-vaccenic acid, the Rt-2560 provided better separation of C10:0 from the matrix. A different approach to sample preparation could result in better separation of C10:0 on Rtx-2330.

Figure 2: Separation of butter FAMEs using GC-FID

After analyzing butter, I decided to go back to a grocery store and take a good look at nutrition labels of more suspected products. Shelf-stable or frozen pastries were all in clear, but I had luck in the frosting aisle. I selected two types of chocolate frosting which declared 1g of TFAs per serving. The first frosting tested proved to be mislabeled since no TFAs were detected and the pattern of C12:0, C14:0 and C16:0 suggested replacement of partially hydrogenated oil by palm or palm kernel oil.

Fortunately for my analysis (not so fortunate for consumers), the second frosting showed a whole slew of TFAs. Figure 3 shows a close-up of the C18:1 region of chromatogram overlaid with cis/trans FAME standard mixture (#35079, in blue). Interestingly, Rtx-2330 was able to separate the standard mixture reasonably well but failed to separate the same isomers (namely C18:1 cis-6 and cis-9) in the real sample (Fig 3A). The second column (Rt-2560) separated those two peaks fairly well, moreover, it showed an additional peak directly following methyl oleate (C18:1 cis-9, Fig 3.B).

Figure 3: Separation of C18:1 isomers in frosting using GC-FID. The red trace is the frosting sample, blue trace is the cis/trans standard.

 

To conclude, while Rtx-2330 provides fairly good separation, it is crucial to use Rt-2560 to separate as much of cis/trans isomers as we can.

 

PS: Have you ever tried to use Rt-2560 on GC-MS? Coming up in my next blog post!

References:

  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2596737/

What’s in a name? A C18 by any other name would not be the ARC-18

You have probably read or been told numerous times and in numerous ways that not all C18 columns are the same. And that is very true. Particle morphology, bonding chemistry, and add-ons like end capping all influence the retention and selectivity of this workhorse LC phase. At Restek we have an interesting C18 phase that we call the ARC-18 that I would like extol upon if I may.

The name ARC-18 is descriptive of one of its most useful characteristics. I actually had the pleasure of coming up with this name (a love/hate task for any product manager). The “AR” in ARC-18 stands for “Acid Resistant” which is very descriptive of this C18 phase. Through steric hindrance or the add on of bulky side groups near the ligand connection to the silica the bond is protected from the attack of acidic mobile phases that can cleave off the C18 and cause your columns to lose retention.

 

The acid resistance of a sterically protected C18 is well documented. We often describe this in comparison to non-protected C18s. And its advantages are highly sought after. Especially when you want a long lasting and stable column for LC-MS/MS where the mobile phases are typically acidic. An area where that is particularly important is in the analysis of peptides. My colleagues here at Restek did some fantastic research to demonstrate how the acid resistance of the ARC-18 allows for the flexibility of acidic adjustments to optimize peptide analysis.   http://www.restek.com/pdfs/PHAN2615-UNV.pdf

While there are other sterically protected C18s on the market you may find that these phases are also end capped. Encapping is typically done to prevent analyte interaction with the silica surface which can cause secondary retention exhibited as peak tailing. We found that C18s that were both sterically hindered and end capped (e.g. TMS) could take longer to equilibrate and therefore increase your run time. The endcapping can also cause the peak shape of some basic compounds to suffer. We wanted a C18 with a well-balanced retention profile for many different types of compounds like pesticide panels.

Another area where this phase shines is in cannabis potency analysis. We have demonstrated excellent LC-UV separation for 16 Cannabinoids on both our Raptor 2.7 (shown below) and 1.8µm columns utilizing the unique selectivity of the ARC-18 phase.

16 Cannabinoids on Raptor 2.7µm ARC-18

So if you need a robust C18 column for LC-MS/MS, a selective column for cannabis potency, a well-balanced C18 for a wide array of pesticides, or a versatile column for peptides, have a look at the ARC-18. It is truly ahead of the curve.

How often do I need to get my electronic flowmeter recalibrated?

The answer is it depends. It depends on how often you use it. It depends on the environment it has been exposed to. It depends on what your company’s, industry’s or government’s regulations on recalibration are. It depends on whether you have accidentally dropped or banged the device. It depends on how confident you are of the results your are getting.

 

 

 

 

 

 

 

 

 

All instruments degrade with time
Most measuring devices drift out of tolerance, and some devices need more frequent calibration than others.  The reasons depend on the technologies used in the device and where the device is being used.  When the device is primarily electronic in nature, the resistors, capacitors, and solid-state components that comprise it will deteriorate with time and exposure to heat, cold, and radiation.  As a result, the accuracy of the measurements made by the device also degrade with time until its specifications are exceeded.  Usually, the calibration process can compensate for this degradation through electrical adjustments to the device.  When calibration cannot bring the instrument back into specification, some repairs or part replacements may be needed.

Restek spent a lot of time developing and testing our Proflow 6000 flowmeter.  Under the controlled lab conditions we subjected our devices to we found that our devices stayed within acceptable calibration ranges for at least a year.  However, not all customers use or store the devices in the same way in which we tested them.  Therefore it is up to customers to determine there own frequency of testing.

When customers return devices for recalibration the collection of as-found data gives a good snapshot of how out of calibration a device is (this data is given in the recalibration certificate).  In most cases one or two calibration points are slightly out of range.  This is a good indication that the device was still providing accurate data up to that date.  If, however, the as found data shows significant drift from the calibration then it is an indication that there is damage to the flow sensor manifold.  In our experience this has occurred from exposure to too high a flow rate, even it if is a short burst (always establish flow before applying the flowmeter to measure the flow), or that the device has been dropped or banged.

To always get the most accurate flow measurements, contact Customer Service to send in your flowmeter for recalibration (cat.# 22656-R).

The Chromatography Picture-Show

If you’re caught up on all your favorite shows, might I suggest the Restek Video Library for your next binge. Most of the episodes only run about two minutes, so there are few extraneous subplots. (And, so far, no car chases. Not a single one in over 50 videos! But new episodes are added all the time, so who knows?)

screen shot showing the library and its menu location

The cast is superb, and delivers performances packed with practical wisdom. Their costumes probably won’t dominate the awards, but the concise and helpful info they’re providing outshines such considerations. Also of note is the use of exotic filming locations such as laboratories and even the abstract realm of cyberspace. You feel like you’re right there. The cinematographer’s boldness is most apparent in the unflinchingly informative depictions of the guts of LC and GC instrumentation.

Diverse plotlines offer something for nearly everyone. From the heartbreak of tailing peaks to the triumph of a clean, square cut on a fused silica column, from the thrill of proper LC column storage to the drama of detector lamp replacement, it’s all there. There’s even a very special episode about finding the reference standards that match your requirements.

Although these gems have yet to show up on any of the major streaming services, they’re easy to track down. You can even use your phone and take them into the lab with you. Here’s the hookup:

http://www.restek.com/Technical-Resources/Technical-Library/Video-Library

https://www.youtube.com/user/RestekCorp

Have there been any new applications developed for Diquat and Paraquat?

I am happy to answer “yes” to this question. Those of you who have been doing this analysis might have been using our Ultra Quat column that I talked about in an earlier blog post here, “I have an Ultra Quat column and I know how to use it…”

 

This updated method uses the Raptor HILIC-Si, which is a newer product we are excited to have. Here is what the application looks like:

http://www.restek.com/images/cgram/lc_fs0512.pdf

 

We are pleased with this application, particularly since it does not require any ion pairing agents or chaotropic salts. The mobile phase modifiers are very common ones that most labs will have on hand and extended equilibration times are not needed (as compared to NaPF6 or Heptafluorobutyric acid). The run time is short and sweet.  :-)

Here is a link to the product information for the column we used:

http://www.restek.com/catalog/view/50802/9310A52

 

I hope you find this post helpful and thanks for reading.

Which Headspace Vial Cap Is Right For Me?

Today, I’d like to cover a question that I have been receiving from cannabis labs who are doing residual solvents analysis. This blog may not only help cannabis labs, but also help labs analyzing other matrices looking for residual solvents or very volatile compounds. The question is, “Which type of vial and vial cap combination should we use to do our analysis?”

This is referring to the screw-thread caps (18 mm) and crimp caps (20 mm) for 20 mL headspace (HS) vials. So instead of just recommending one or the other based on “feel” or price, we decided to run a little experiment to compare the performance of the two styles. The experiment was designed to analyze a few very volatile compounds and gather data on how well these two types of caps prevent the compounds from escaping the HS vial over the course of a specific period of time. To familiarize yourself with the products that we were working with, please reference Figures 1 & 2.

 

Figure 1. Screw Cap HS Vial: PN#23082 and Screw Cap: PN#23092

 

Figure 2. Crimp Cap HS Vial: PN#21162 and Crimp Cap: PN#21761

 

Sample preparation included adding propane, butane, and isobutane standards in N,N-Dimethylacetamide (DMA) along with α,α,α-Trifluorotoluene as the ISTD to a 20 mL HS vial. To model the vial cap’s ability to keep these volatile compounds from escaping the vial, we designed a time study. In this study, 14 samples were prepared for each vial type and the samples were split into two sets of 7. Set one (T0) was run immediately after the samples were prepared and set two (T6) was run 6 hours later. It should also be noted that the crimp cap pressure was set to model the tightness of a screw cap. This meaning that the amount of torque needed to remove a screw cap was similar to that of the torque needed to spin a crimped, crimp cap.

The average compound area count from T0 to T6 were compared by calculating the relative percent loss over the 6 hour period of time. The relative percent difference for each HS vial type can be seen in Figure 3.

 

Figure 3. HS Vial Cap Comparison

 

From the data shown in Figure 3, we can see that the screw caps (blue) did not seal as well from T0 to T6 compared to the crimp caps (red). It is also worth noting that we see very little change in our ISTD over the 6 hour time period for both the screw cap and the crimp cap.

After looking at the data and taking everything in, I think it is suffice to say that if you are working in a lab doing HS analysis of very volatile compounds (gases), you should be using crimp caps. However, even if crimp caps are being used, one still needs to be cautious of the fact that the lighter, more volatile compounds, like the compounds shown here, are still capable of escaping the HS vial. Now, with all this being said, I don’t want to give the impression that screw cap HS vials are worthless. They can definitely be used in HS analysis, especially if the compounds being analyzed are on the less volatile side or your time from sample preparation to analysis is kept to a minimum. As an example take a look at the minimal differences of α,α,α-Trifluorotoluene, so for many customers analyzing the standard list of solvents and volatiles a screw cap may be appropriate.

Tailing solvent peak during split injection? Check your column installation distance!

When performing splitless injections, it is not uncommon to witness a tailing solvent peak, given the large amount of solvent introduced onto the column over a relatively long period of time.  For split injections, however, only a small portion of the solvent loads onto the column and it occurs very quickly. This results in a relatively sharp solvent peak.

Recently, I set up a method with a 20:1 split and upon my first injection I noticed a badly tailing solvent peak, which I wasn’t expecting (Figure 1 red trace).  My gut feeling told me something was occurring within the inlet and the solvent wasn’t split properly.  I removed my column from the inlet to find that the installation distance was too low. The recommended installation distance for an Agilent split/splitless inlet is 4-6mm above the ferrule and my column was only 1-2mm above it.  This would lead to the column being below the inlet seal surface, creating an area of dead volume, where residual solvent would not get swept away by the higher split flow.  After correcting the installation distance, my problem disappeared (Figure 1 blue trace)!

Figure 1: Improper installation distance of column can create excess dead volume, leading to tailing.

Figure 2: Capillary installation gauge

 

Generally, I pre-swage my ferrule to the column at the proper distance using a capillary installation gauge, but I was in a rush and didn’t do that this time. I probably bumped the column while installing, inadvertently pushing it down.  I highly recommend using a capillary installation gauge, which allows you to pre-swage your ferrule to the column at the exact specified distance for installation (Figure 2).  It only takes a few seconds and greatly improves consistency of installation.  The table below shows the capillary installation gauges that Restek carries for various instrument makes.

 

Are My Shut-off Valves Contaminated?

Figure 1: Experimental set-up for testing valve contamination (plug valve shown). Gas flow was set at 20mL/min for 1 hour (1200mL total extraction volume) with oven held at 35⁰C and the split vent closed. After a one hour hold, oven was ramped to 330⁰C @ 20⁰C/min. An Agilent 7890A was used with an Rxi-5MS (30m x 0.53mm x 0.25µm) (cat. #: 13425) to allow for high flows. Inlet liner was a Topaz 4mm single taper liner with wool (cat #: 23303).

Shut-off valves provide a convenient means to control gas flows and are often used in conjunction with gas chromatography systems.  There are several types of shut-off valves including ball valves, plug valves, and diaphragm-sealed valves.  Some of these valves, ball and plug valves included, use a silicone-based lubricant to make opening and closing the valve easier and to extend lifetime by reducing wear on moving parts.  Unfortunately, this lubricant can off-gas into the flow path and lead to system contamination, causing baseline interferences.

Use a gas filter containing a hydrocarbon trap between lubricated valves and the GC to prevent any off-gassed components from entering your system.

I performed an experiment where I attached ball valves (cat. #: 23144) and plug valves (cat. #: 23146) directly behind the GC EPC and set a high flow of carrier gas for one hour (1200mL of Helium total volume), while leaving the split vent closed (Figure 1).  The GC oven was left at 35⁰C to trap off-gassed components on the head of the column.  Following this, I ran a series of “no-injection” blanks, with a temperature program, to qualitatively see if anything was off-gassing from the valves.  This experiment was also performed with a Super Clean Triple Gas filter (cat. #: 22019) installed between each valve and the instrument.

I found that the plug valves introduced a significant amount of contamination to the system (Figure 2).  Ball valves produced some contamination, as well, but at a much lower level than the plug valves (Figure 3).  This is likely due to the different opening and closing mechanisms of each valve and the much larger surface area of the lubricated plug.  Based on this, I would never recommend using a plug valve without a filter for carrier gas lines and would encourage the use of filters even with a ball valve.  Testing of multiple valves of each type showed similar results.

When these experiments were repeated using a filter in between the valve and the instrument, this contamination was effectively captured, as can be seen in Figure 2 and Figure 3, for each respective valve.  Note that I used a triple filter (traps hydrocarbons, moisture, and oxygen); however, a hydrocarbon filter is most critical for trapping this specific type of contamination.  Nonetheless, gas lines should have moisture and oxygen traps prior to the instrument, as well, hence my choice of the triple filter.

Figure 2: Contamination introduced from plug valve (red trace), measured with a GC-FID. By contrast, using a filter between the valve and the instrument (blue trace) produced a clean baseline.

Figure 3: Contamination introduced from ball valve (red trace), measured with a GC-FID. Note that this is at a much lower level than the plug valve, but could still interfere with trace analyses. Using a filter between the valve and the instrument (blue trace) produced a clean baseline.

 

I was surprised at the amount of contamination witnessed, especially from the plug valves.  Many GC gas plumbing guides show shut-off valves downstream from the filters, placed directly before the instrument.  Keep in mind that with the large volume of gas passed over the filter with the split vent closed, this was designed to be somewhat of a worst-case scenario; however, similar results could be witnessed simply from letting an instrument sit idle for a period of time.

For these experiments I used an oven temperature of 35⁰C to trap off-gassed components on the column.  There are undoubtedly additional volatile components that are not effectively captured using this method.  Off-gassing of these volatile components could potentially create major contamination issues with sampling techniques where valves are placed before analytical traps for volatiles, such as thermal desorption units, purge and trap, etc.

 

The usage of Reference Standards in MOSH/MOAH Analysis

Abstract

The unintended migration of mineral oil compounds into food, e.g from packing materials or from production processes are a raising topic in industry and scientific discussions. For a first screening, an LC-GC/FID method was established in the last years. In collaboration with Axel Semrau, Restek has developed ready to use standards for quantification and and identification of the different fractions to be controlled. Saturated Hydrocarbons and Aromatic Hydrocarbons have to be cut of from LC fraction before transferred into the GC and the different areas which have to be taken into consideration have to be identified properly. The Blog entry gives an overview about how to use the different available standards correctly.

MOSH/MOAH

Food may be contaminated with mineral oil compounds by unintended migration from different sources. One of the most common sources for such an unintended contamination is coming out of recycled paperboards, but also during production processes such a failure may occure.

Due to their different toxicological capability, mineral oil compounds are subdivided into two fractions:

  • MOSH: Mineral Oil Saturated Hydrocarbons
    -saturated hydrocarbons
    -paraffines & naphthenes (cyclic)
    -highly alkylated
  • MOAH: Mineral Oil Aromatic Hydrocarbons
    -highly alkylated mono- and polyaromatic compounds
    -also saturated ring linked to aromatic rings
    consistence often unknown

The toxicity of both groups are described as follows:

  • MOSH:
    –accumulated in Human Tissue
    –toxicological relevance unknown
  • MOAH
    -most substances unknown and toxicological nonvaluated
    -carcinogenic potential can not be excluded
    -unaccepted risk
    -unaccepted in food

The different toxicological risks have found its expressions in different legal restrictions, as to be found in the EU Commission  Recommendation (EU) 2017/84 of 16 January 2017 or in the German Mineral Oil Regulation, wherein the concentration in food contact material (recycling paper & cardboard) is limited for MOAH to 6 mg/kg or, if limits in the material does not comply, it has to be verified that limits in the food comply to MOAH C16-C35  less than  0,5 mg/kg.

For the MOSH fraction the ALARA Principle has to be applied.

  • ALARA Principle
    –In Europe the ALARA principle is regulated by the European Food Safety Agency EFSA and translates to “As Low As Reasonably Achievable”

Analytical Aspects

In both fractions, MOSH and MOAH, a tremendous amount of different compounds have to be covered with an analytical method. Therefore both fractions can only be described as a sum parameter method.

Due to EFSA “Currently, the most efficient methods for analysis of MOSH and MOAH in food and feed comprise extraction followed by pre-separation by high performance liquid chromatography (HPLC) on-line coupled to GC with flame ionisation detection (FID).” – EFSA Journal, 2012, 10(6):2704, is the best choice for this analysis.

This method was first described by K. Grob and M. Biedermann from the Kantonales Labor Zurich. (BIEDERMANN M., GROB K. On-line coupled high performance liquid chromatography-gas chromatography (HPLC-GC) for the analysis of mineral oil: Part 1: method of analysis. J. Chromatogr. A. 2012, 1255 pp. 56–75)  and has found its way into a European norm via EN 16995:2017 (Foodstuffs – Vegetable oils and foodstuff on basis of vegetable oils – Determination of mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH) with on­line HPLC­GC­FID analysis).

Restek is accompanying the development of an automated system for the analysis of MOSH and MOAH of the German company Axel Semrau GmbH since years, adding our knowledge in separation science as well as in LC and GC but also by preparing the needed reference materials.

The method uses a “Normal Phase” HPLC with a Silica column to separate both fractions, MOSH and MOAH, from sample matrix, than transfers either the MOSH or the MOAH fraction as a large volume injection onto a 7 to 10 m retention gap, which uses solvent focusing and a solvent vapor vent to get rid of most of the used solvent. This approach delivers both fractions, MOSH and MOAH as a chromatographic hump, as shown in the chromatograms below. Both chromatograms were provided by Axel Semrau GmbH

 

Sunflower Oil MOSH Fraction

 

Sunflower Oil MOAH Fraction

Reference Standards

For quantification, to prevent losses of low boiling compounds and to make sure that the complete fraction was transferred to the GC, an internal standard (IS) is used. (Restek cat. No. #31070). The 9 compounds included are used as shown in the chromatograms below.

Sunflower Oil MOSH fraction, spiked with IS, courtesy of Axel Semrau GmbH

CyCy: Cyclohexyl Cyclohexane, standard for Quantification, not present in mineral oil products
C13: Tridecane, proves no coelution with CyCy. Peak Identification. Has to be a peak pair with CyCy.
C11: Undecane, detection of losses of volatile compounds
Cho: Cholestane, end of MOSH Fraction

Sunflower Oil MOAH Fraction, spiked with IS, courtesy of Axel Semrau GmbH

2-MN, 1-MN: 1-/2-Methylnaphtalene: standard for Quantification, peak pair for better identification
5B: n-Pentylbezene: detection of losses of volatile compounds
TBB: Tri-tert.-butylbenzene: start of MOAH Fraction
PER: Perylene: end of MOAH fraction. Can be determined also with UV detection in automated approaches

Different regulations are looking for different integration limits for the detection of the two fractions. Restek therefore has developed a Retention Time Standard (Restek cat. No. #31076), This standard has to be run before and after every Sequenz to avoid retention time shifts and therefore wrong results by using the wrong integration limits.

The compounds are used as follows:

  • C10 = lowest boiling compound to be detected
    C11 = Marker out of Restek-Mix #31070 – retention time stability
    C13 = Internal Standard out of Restek-Mix #31070 – ret. Time stability
    C16 = requested boiling point limit for fraction quantification
    C20 = requested boiling point limit for fraction quantification
    C24 = nowadays requested boiling point limit for fraction
    quantification
    C25 = New supposed requested boiling point limit for fraction
    quantification. If C24 or C25 will be used is not yet fully
    determined (both included gives future proof)
    C35 = requested boiling point limit for fraction quantification
    C40 = todays detection limit
    C50 = desired new detection limit

 

MOSH/MOAH Analysis helps to improve our Food Quality

 

Annual Replacement of Cartridge Gas Filters

A significant number of instrument and column complaints are carrier gas related, which could be caused by breakthrough from filters that are not replaced in time.

The possible consequences of a filter breakthrough are:

  • Gas distribution system behind the filter will be contaminated (fast cleaning nearly impossible, bleeds for months)
  • Instrument gets contaminated, expensive maintenance required
  • Column lifetime reduced, bad analytical results, high cost of ownership, unnecessary changing of column brands
  • MS source gets contaminated, expensive maintenance required, long system shutdown.

This article explains why it is important to replace your gas filters annually instead of waiting for the indicators to change color.

Filter Media Types

A typical GC-MS laboratory gas filter system contains three types of filtering media:

  • Oxygen Catalyst for absorbing traces of oxygen
  • Activated Carbon for adsorbing hydrocarbons
  • Molecular Sieve for adsorbing moisture

These filter media types can be divided into two groups:

  • Chemically absorbent media

Like a Venus fly trap, when it comes in contact with a contaminate it absorbs it and does not let it go. Adsorption differs from absorption, which also removes things, but the result is swelling of the media. The media size increase equals the amount of material removed

 

 

 

 

 

 

  • Surface adsorbent media

Like a floor mop, where the contaminant is trapped onto the surface of the media and retained. The material doing the adsorption does not change in size.

 

 

 

 

 

Filter Media Breakthrough Indicators

The visual indicators are mainly for urgent situations such as a leak or high amount of impurities breaking through.

Indicators are typically placed behind the filter media bed. When they change color shortly after installation of the filter it usually means there is a leak or that the gas distribution system including the manifold to which the filter is connected was not flushed properly prior to – or during – installation of the filter.

When the indicator changes color during normal operation of the filter it indicates that the filtration media has reached its capacity, and the filter should be replaced immediately to avoid contaminant breakthrough.

Other components such as branched hydrocarbons which are also trapped by the molecular sieve are not shown by the moisture indicator.

Also note that most filters do not provide an indicator for hydrocarbons, so you would never know whether the activated carbon has reached its adsorption capacity.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Filter Media Breakthrough

Both adsorption and absorption media have fixed capacities, meaning they hold just so much, since they are storing the material removed from the gas, not destroying it.

Normal situation

Hydrocarbon breakthrough

Over time, the pores of the activated carbon fill up. The molecules that are adsorbed with higher energy (larger mass) can displace the lower-energy molecules that are less tightly held. This phenomenon, called displacement, may knock the smaller particles off the media, straight to the column and into the instrument.

Moisture breakthrough

The molecular sieve adsorbs moisture until it cannot adsorb anymore. If the humidity level of the gas is lower than in the molecular sieve, it will de-adsorb its moisture until it is in “balance” with the lower humidity level of the gas, which means the filter could increase the amount of moisture in your gas.

Oxygen breakthrough

The media size increase equals the amount of material removed. When the media has reached its absorption capacity it will not release the already trapped contaminants but it will also not absorb any new ones.

Replace your filter before the indicators start changing color to prevent breakthrough and to avoid high maintenance and repair cost of your instrument

As explained previously, filters which are not maintained on a regular interval can cause the outgoing gas to become more contaminated than the original source gas.

The color indicators used in gas filters are so called ‘last minute’ indicators and require quick action.

You can compare it to the engine oil indicator in your car. When the engine oil indicator is blinking on your dashboard, the car should not be driven and ignition should be switched off unless topped with engine oil – In event of taking risk to drive – high probability of engine getting seized causing high expenditure to repair or replace the engine.

The same is valid for gas filters. When one of the indicators starts to change color, the filter should not be used and instrument should be switched off unless the filter is immediately being replaced with a new one – In event of taking risk to continue – there will be a high probability of contaminant breakthrough causing high expenditure on instrument maintenance as compared to planned annual preventive maintenance on your instrument and gas filters.

So what you can do as an end-user is to always buy an additional set of filters to keep on standby in case the indicator starts changing color or to use a good preventive maintenance plan or tool (such as the electronic indicator) to replace your filters at least once a year.

Find out more about cartridge filter and details on the product offering by following the following weblink: http://www.restek.com/Supplies-Accessories/GC-Accessories/Gas-Purification?s=type:baseplate