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Chromatograms are like fingerprints.  If you can “read” chromatograms well, you often can find a plausible cause.
A peak shape is observed as shown in figure 1.  It just took 15 injections to get the bottom chromatogram.
Dead volume the system; Column may be broken in bottom of injection port or in the bottom of the detection port liner. Activation of the system 1:  this can be the detection port, as stated above, but many times is the first section of the capillary column used. Activation of the system 2:  if water or oxygen enters the system, often at higher temperatures the inlet section for GC columns gets activated. If connection with uniliner is not sealing well:  when using this liner for direct injection technique, a good seal is required.
If the tail develops in time, the column may also be activated by sample matrix or carrier gas contamination.
Note: If purchasing one of our Silcosteel regulators, don’t forget to purchase treated fittings and treated tubing. This phenomena will occur with all types of PLOT columns (Porous Layer Open Tubular), as well as their packed equivalents. A peak shape is observed as shown in figure 1.  Peaks start to rise slow, reach their maximum height and sharply fall down.
If the component elutes well-resolved from neighbor peaks, you can work with that as the total area will represent the absolute amount brought on to the column.
Use a column with higher loadability: loadability is increased by having more stationary phase in the column.
Use a phase with better solubility for the target analytes; sometimes peaks elute like shark-fins because the solubility is very low. Figure 1: Analysis of underivatized amphetamines solvent standard after 71 injections of liver, blood and urine, 65 HFAA Derivatized amphetamines with no cleanup.
A peak shape is observed as shown in figure 1.  Here an interesting peak shape develops after the analysis of underivatized amphetamines solvent standard after 71 injections of liver, blood and urine, 65 HFAA Derivatized amphetamines with no cleanup.
Originally the peak shape for amphetamine and methamphetamine was good (red trace) , but it developed in time into the shape shown by the green trace.  Same as in previous blog on peak shape, a “reaction platform” seems to be formed. First suspect is the liner, which for sure can be a problem-maker, but it usually will not give us a platform. Here the matrix is changing (contaminating) the first section of the analytical column, which makes it more reactive.
Couple the column with a guard column:  one can use deactivated fused silica for that, but in case of reactivity one can also use a coated guard for that.
If a component is formed that has less retention, the reaction platform will be in front of the main component. Any time such a “reaction platform” is seen, we need to find conditions to reduce this effect.  The component must elute at a lower temperature. Let’s say you are starting your next GC project and realize that it is a packed column method.  However, you normally use capillary columns, and are not familiar with what you need to know before you order a new packed column. The first thing you should do is to review our Packed Column FAQ’s, which can be found at this link.
If we don’t list a column which matches what is specified in the method, or your instrument is not listed above (especially true for In-Line and Process GCs), you will need to complete our Custom Packed Column Form. In summary, purchasing a packed column and necessary fittings (for installation) can be a time consuming, and sometimes frustrating task for those who normally use capillary columns, but spending a little extra time prior to any purchases can save you days, or even weeks, and frustration. There are many fake products out there including foods like “virgin” olive oil, honey and branded liquor. But other types of products like dietary supplements can prove more dangerous, particularly items like weight loss supplements.
A few years ago I got a notice that one such product had been pulled from the market because it contained drugs that were considered dangerous. Throwing caution to the wind, I found a website still offering the product and ordered it immediately. We found fenfluramine, sibutramine, propranolol and ephedrine, which were reported by the FDA. We also found niacinamide which is part of vitamin B and a popular supplement often found in energy drinks. You can read the product instructions here…seems to me like it calls for a lot of this cocktail. Restek’s on-line version of EZGC is a selectivity tool that relies on a pre-loaded library of thermodynamic retention indices.
Since its introduction there have been thousands of searches across a broad range of compound classes. For compounds that are not in Restek’s library but are in our chromatogram database there is a recommendation and links to those chromatograms.  Methane is commonly searched and while there is not a library for this analyte we have a variety of applications and chromatograms that are linked to this search. In EZGC’s webinar we talk about the power of EZGC, but we never put the pedal to the metal.
Clicking on the magnifying glass in the compound list will display the spectra of each compound — coelutions can be displayed to easily reveal interferences. A collaborative research program, the Consortium for the Restoration of the Olifants Catchment (CROC), is ongoing to investigate the cause of the problem and hopefully slow the disappearance of this sentinel animal from the park ecosystem by improving water quality.
To set up a GC-MS detection system, it always takes considerable time to stabilize the system once the vacuum is applied.
One can also consider using a 4-port valve which is connected like shown in figures 1 and 2. When the valve is changed in position 2, column 2 is directly coupled with the MS, without any introduction of air. The valve will have a higher heat capacity, which can cause peak broadening due to thermal lag.
Especially when implementing vacuum GC, where a restriction is used in front of a 0.53mm column, such a valve system would be of interest. This is a common question we get asked in tech service, and although this is a better question for the instrument manufacturer, I will try and provide our blog readers some general information.
This question pops up a number of times every year.  The joking answer my former colleague Dick Zwiep (when we both worked at Chrompack time) used to make was:  No and No-two!
NO,  (Nitric Oxide), is more challenging to measure.  When exposed to oxygen, NO is converted into NO2 (Nitrogen Dioxide), which has a dark brown color.
It is retained on Molecular sieve type adsorbents and  can be measured, but peak shapes are usually not symmetrical, which challenges elution and detection  of low levels.
Does Hydrogen as the Carrier gas, Negatively Impact the Peak Shape when using Siltek or Sulf-Inert Deactivated surfaces?
Use of hydrogen is often perceived as dangerous which is highly exaggerated if you understand the physics and practical risks involved. This is not the theme here: here we like to take away a concern that was mentioned by a practitioner of GC, who claimed that Siltek deactivated surfaces could not be used with hydrogen. As this was a challenge because in our experience we have very positive reactions for inertness of Siltek type surfaces, especially related to reactive compounds like H2S, methyl mercaptan and even mercury. Also after 24 hours at 405 C, the MXT column showed near perfect inertness, which is due to the Siltek deactivation.


It became very clear that the hydrogen had no measurable negative effect at all on the performance of the Siltek deactivated MXT column.  If there would have been any development of activity, it would immediate be visible on the peak symmetry, especially the highly polar, acidic and base- analytes as listed above. 1) Overnight: Our recommendation if using a column daily is to leave the carrier gas on overnight and set the GC oven temperature to 110°C. 2) Up to one week: This is considered the transitional time-frame since depending upon the specifics of your carrier gas flow rate, column, detector, and analysis, it may be better to follow #1 above or #3 below. 3) More than one week: Normally we recommend that all heated zones of the GC (injection port, oven, and detector) be cooled to room temperature. On February 3rd, a surprise party was organized on behalf of professor Sandra, who is retiring from University Gent. A funny overview of Pat’s special preferences was shared by Peter Myers who also included a song which was supported by a famous choir (photo 1). Pat received an award from the Pfizer group for his role in the Pfizer research centre and the many students that have been graduated since under his coaching.
On behalf of Restek, Pat received a Star award for all his contributions and inspiration for separation sciences to make young people grow and innovate. For Pat it was difficult to find the right words to be put suddenly in the spotlight like this, but he highly appreciated the gesture. It was a very appropriate reception for a scientist that has made firm contributions to the science of micro separation technologies.
Tadeusz Gorecki , University of Waterloo, Waterloo, ON; GC?GC 20 years later: Where are we now? Frank Dorman, The Pennsylvania State University, State College, PA ; Realizing the potential of GCxGC: What role does column choice play? January 8-10  the 20th edition of the Norwegian Symposium on chromatography was organized in Sandefjord, Norway.  This symposium takes place every 2nd year and has developed into a successful event where around 240 chromatographers get together to present and learn developments on chromatography.
The symposium offers a nice combination of scientific and commercial developments with a strong social program that allows for many informal contacts and networking. Besides running 3 parallel sessions to accommodate the different presentation, there is also a poster session, which grows bigger every year. Restek presented on latest developments in GC and also on obtaining faster GC using existing instrumentation. It would be nice if a focused, low threshold, meeting like this would be possible in other countries. Additionally you will like Norway because of the clean air, the beautiful nature and everybody speaks English.
The guard column protects the analytical column for contamination, which dramatically increases the column life time. Deactivated fused silica tubing can be used as guard column and can purchased per meter of which a defined length. Integrated Guard columns have been first introduced by Restek® Corporation around 1990 and have been widely used since. Such Integra-Guard® columns are typically 5 – 10 m in length and can be made for most standard stationary phases and mostl column diameters. In this series, we will show a series of GC-chromatograms that are obtained from users and discuss some potential causes for the phenomena. In splitless injection the injection port must be flushed immediate after the injection time. They can be manufactured of either chrome-plated brass or stainless steel, they can be single or dual stage, and they will have a specific CGA (Compressed Gas Association) fitting on one end. Leave the end-fitting (shown by the red arrow) attached to the regulator and install a tube-end reducer to this end fitting.
To read more about fittings, please review my previous post I need a fitting, but which one?   If you are looking for the appropriate gas regulator, review my post Need some help in choosing the correct gas regulator? The impact of overload is very clear.  Also note that the peak maximum of the overloaded peak, elutes at a shorter retention time. As for PLOT columns, there are limitations on layer thickness, this is not always an option.
2 If we allow only 50% of the sample onto the column, the separation improves as peaks will be more symmetrical. This can be done by dilution of sample,  injecting less or using a higher split-ratio; Figure 2 shows the separation if 50% of the sample is injected on to the column.
Typical reactivity in a liner provides a sharp decomposition peak, which is also focused by the splitless injection. Believe me when I say “you are not alone.” Hopefully this post will help simplify the transition from a capillary column method to a packed column method.
Restek Customer Service is here to help you with your questions prior to purchase, and Technical Service after your purchase. My colleague Jack Cochran and I took a look using GC-TOFMS and GCxGC-TOFMS to see if we could find the same compounds as the FDA reported as well as anything else that looked interesting. Fenfluramine was part of the weight loss drug Fen-Phen that was pulled from the market in 1997 because it is a stimulant that caused heart valve problems.
This makes it possible to predict retention times and optimize chromatographic methods without the need to analyze compound sets under many different conditions. The program outputs: compound retention time, resolution and peak width along with the column conditions and dimensions.
While EZGC will accept many different names for the same compound; the most common challenge for the user to date has been mis-spellings or combinations of compounds entered.
This pumping down and stabilization can take from several hours to some days to a night,  before a decent calibration is possible and the instrument is in good shape to run the methods. This restriction limits the flow, which allows only a limited amount of air into the MS during column changes.
In position 1, column 1 (injector 1) is connected with the transfer line to the MS.  The effluent of column 2 (injector 2) is going to a second detector or to vent. Maintenance here is usually done by replacing the entire restriction on the front of the column, meaning the MS vacuum and power has to be turned off.
First, let me define my definition of permanent (fixed) gases; I consider hydrogen, helium, oxygen, nitrogen, argon, carbon monoxide and carbon dioxide the common permanent gases.
This maybe a way to measure NO2 indirectly by converting the NO2 into ethylene in a hot inlet, however, the conversion is believed not to be quantitative. Not only because of its guaranteed availability, it also gives a significant benefit in analysis time.
IT was shared that these surfaces will do for neutral analyte like hydrocarbon or halogenated compound, but not for polar analytes. This column contains a 0.16 micron film of a non-polar phase, of which the first 2 meters are only deactivated. As we did not see any difference in chromatography, we conditioned the same column for 24 hours at 405?C. 3 Test result of tge 16m x 0.53mm MXT-Biodiesel TG column with 2 m Integra-Gap, after 24 hrs 380C + 24 hrs 405C under hydrogen.
This prevents water vapor from condensing inside the column and minimizes the time before the column is ready to use the following day. This is especially true of packed columns because if you don’t allow the pressure in the column to equilibrate with the outside air, the surge when the column is removed from the inlet may cause the bed to collapse.


At the party, a large number of scientist participated, all friends, colleagues and co-workers with the many projects Pat did during the past 30 years. We hope to keep on seeing Pat, and his wife Martina, during the future meetings on separation science technologies. Poster prizes are there to stimulate young scientists and there is also a trip to Pittcon (this time Orlando)  to win, which is announced during the official diner. Such a guard column can be trimmed when polluted and eventually be replaced.  Depending on the application  guard columns have a life time of 1 week up to 6 months. Since it happens after 15 injections, you may consider to use a column with more tolerance for matrix.
The catalog numbers for these male connectors are 23136 for brass and 23186 for stainless steel. In gas liquid chromatography, using bonded siloxane or polyethylene glycol-type phases, this peak shape is typically obtained if a component is overloaded. Using an acid deactivated polar phase, like a Stabilwax-DA, offers highly increased loadability for these highly polar compounds, see fig.4. Please verify everything is correct before ordering, because custom products are non-returnable and non-refundable. Food fraud seems to be on the rise…at the very least governments and researchers are devoting more resources to finding and tracking incidents. Sibutramine has a similar story; it was prescribed as a weight loss drug until being withdrawn from the market in 2010 due to heart health concerns.
The only columns capable of providing some separation (without cryo cooling) are molecular sieve columns (zeolite or carbon; just remember that carbon dioxide and moisture will get stuck in the pores of many zeolite molecular sieves like the 5A and 13X). The most common (that I am aware of) are TCD’s (Thermal Conductivity Detectors), µTCD’s, DID’s (Discharge Ionization Detectors) and HID’s (Helium Ionization Detectors).
This column is typically used for triglyceride measurement and because of the integrated retention gap, needed for correct on-column injection, a coupling is not required.
Chromatogram obtained is shown in Figure 2 and calculated column parameters are shown in Fig.3. The column should be removed, the ends plugged or capped, the column placed in an appropriate storage container (e.g. It was a very pleasant surprise for professor Sandra as he was really “surprised” by the party.
During the 2 days, there is also an exhibition showing the latest product developments, focusing on chromatography. Disadvantage of cutting parts of the guard column is that the column becomes shorter resulting in change of retention times. Make a 90-degree cut, (fig 2), by using a ceramic wafer and let the wafer slide one-way along your nail,  wet the column and guard ends with some methanol and push it into the PressTight . Rxi-XLB is a new generation phase that can take a lot of sample stress because of the solid stabilization of the polymer backbone. New generation columns like Rxi-series, tend to be more inert and will show improved peak shape. When replacing the end fitting, don’t forget to use PTFE tape, as described in the Installation and Instruction Manual. Using polymers like Rtx-1 as stationary phase, an overloaded peak slowly increases in response, and sharply falls back on the base line. Because of the wide variety of GCs manufactured, there is no way for us to know what you may need, so some preliminary planning on your part will prevent you from receiving a packed column that you cannot immediately install and use. Sometimes adulteration of foods can be dangerous, but often, fraud takes the form of mislabeling or misbranding, dilution or substituting lower quality, less expensive ingredients. Ephedrine is a CNS stimulant with a well-documented history of producing weight loss as well as recreational use. I found out that it is also a laxative that has been used for many years but has lost favor because it may be carcinogenic.
Users have the option to view compound mass spectral data with the added benefit of overlaying mass spectra for coeluting analytes. Due to most mass spec carrier gas flow rate limitations, packed columns usually cannot be used, so the analyst is usually limited to PLOT columns.
Any of these detectors are considered universal, but keep in mind that they won’t detect the compound that is also the same as the carrier gas (e.g. This mixture contains components like hexane diol, chloro phenol and  4-propylaniline.  Asymmetryfactors were measured at 5% peak height. By pushing it, an optical “ring” is observed (see fig.3) which is the actual seal made by the polyimide and the surface.
Lastly, you may use a 2x thicker film which will produce better peak shape as elution temperatures increase. Restek PTFE tape catalog number 22486 is commonly used for brass fittings and 22487 for stainless steel fittings. For every factor 2 increase in film thickness, the oven temperature must be set 15C higher to obtain a comparable retention time.  One can also use longer columns and larger diameter to increase loadability, but the effect will be the biggest if film-thickness is increased. It has been linked to a host of adverse effects resulting in partial bans, restricted levels or requiring a prescription. Sounds like you would be full of energy, have to stay near a bathroom and be relaxed all at the same time while taking this product! Specific searches can be saved and accessed at a later date and technical service is there to help every step of the way.
Because these (PLOT) columns contain particles, one needs to be careful not to get these particles into their mass spec, especially turbo pumps. When the component elutes, the signal increases rapidly, followed by a slow decrease, which results in a tail that starts at the top of the peak and continues until the signal is back to base line. Maximum film thickness for non polar phases is about 5-7 um; for polar phases it is about 2 um. Propranolol is a beta-blocker used to treat disorders like anxiety and panic as well as heart-related problems like hypertension and myocardial infarction. For example if the user is interested in an alternate carrier gas or has questions about a resulting column recommendation technical service can provide modeled chromatograms for other columns and carrier gas types.
Use of a particle trap will catch most of these particles, but I’m sure some will break through the trap and end up inside the mass spec.
If thicker films are used the efficiency of capillaries will rapidly decrease because of the increase of the Cl-term in the Van Deemter equation. Or, you can simply photocopy (onto an 8.5” x 11” piece of paper) a packed column you already own and send its silhouette to Customer Service.
In addition, the connector used to connect the particle trap to the end of the PLOT column can become another source of leaks.
Cochran.  Measurement of PCDDs, PCDFs, and non-ortho-PCBs by comprehensive two-dimensional gas chromatography-isotope dilution time-of-flight mass spectrometry (GC x GC-IDTOFMS).




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