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The following video will walk you through the procedures of calibrating a Restek Veriflo flow controller to the tune of 10.5 mL/min, and then use that passive sampler to collect an 8 hr sample into a 6 L canister:
So why part III and where the heck are parts I and II? Well because this blog series is going George Lucas on you… stay tuned….
Determining your GC column length is important so that electronic pneumatic control of carrier gas flow is accurate, whether during initial installation of the column or after maintenance column trimming. Otherwise, you can have more flow going into the detector than you think (especially problematic in MS as you might lose sensitivity) or even see elution order changes in your chromatography. Calculation of GC column length is easy (or EZ!) with the EZGC Method Translator and Flow Calculator, just by performing a holdup time determination. Holdup time, the amount of time it takes an unretained compound to traverse the GC column from inlet to detector, can be determined by split injecting air (GC-MS), methane (GC-FID), or methylene chloride headspace (GC-ECD) and noting the “retention time”. In the last case, GC-ECD, make sure the oven temperature is at least 250° since methylene chloride will show some retention at lower column temperatures. Don’t overload the column with the compound, i.e., the peak should be symmetrical for an accurate determination. Start your work by entering the nominal value (e.g. 30m) for length in your GC control software, enter a flow, and then do the holdup time determination. I usually take the average “retention time” of three analyses.
I’ve outlined the rest of the procedure in the figures below. Note that I’ve used the Download-ed version, which has the “spinner” for easy adjustment of column length, but it will work for the web-based version, too, just by entering column length values instead of “spinning”. Shoot me an e-mail if you have any questions.
More and more laboratories are facing more and more pressure in both, time and price. More work has to be done in shorter time. Customers are deciding on a cent-to-cent base per analysis whether they will place an order to one contract laboratory or to another. Production laboratories are requested for shorter Turn-Around-Times (TAT) to let production be more precise or to shorten delay times for logistics. Due to increased potential of instrumental infrastructure like Triple Quads, Q-TOFs and other detection techniques as well as automated sample preparation possibilities there is a trend observable towards Multi/Multi Methods (MMM). A Multi/Multi Method is a combination of two or more Multi-Methods (Screening Methods).
During EPRW, Dr. Anna Romanotto and co-workers from the well known Eurofins-Sophia Food Safety Laboratory in Berlin published a poster with their method of “Simultaneous Clean Up and Measurement of 190 Pesticides, EPA PAHs, 18 Plasticizers, Bisphenol A and Non-Dioxine-Like PCBs in Fat and Oil Samples”.
Such a highly sophisticated method demands high end instrumentalization and has very dedicated demands to the chromatographic system, especially to the separation column. A suitable column needs to have sufficient separation power to produce an evenly spread chromatogram, with no clusters of compounds to make MS determination difficult, and must separate difficult pairs of compounds with isobaric fragmentation patterns.
For this method is designed as a high sample throughput method, dealing with difficult matrices, also a long term stability and a batch to batch reliability is requested.
For this fully validated method Dr. Romaotto and her crew has chosen a Restek Rxi-17 Sil MS column (L=30m; ID=0,25 mm; dF=0,25 µm) as best fit for this challenging task.
Please find more details about this Time and Cost saving method and the original published poster here
Environmental contract labs face a hard price pressure. To overcome this pressure, a trend into the direction of Multi/Multi Methods can be observed. If possible, more than one parameter group shall be determined and measured with one instrument without changing hardware. This implements a specific request for the separation power of the column used and the detection power of the installed instrument base.
The appearance of PAH and/or PCB contamination is a suitable indicator for industrial contamination of different matrices like Water, Sludge, Soil and Dust. Both parameters are among the most measured compound classes in environmental analysis in Europe.
To optimize this measurement and to improve their new TQ-8030 GC/Q³ system, Shimadzu Germany recently showed an application which determines both compound classes in one run within 11 minutes by using Hydrogen as carrier gas and a Pseudo-MRM technique to increase PAH sensitivity.
German and International Standards are requesting some frame conditions for the determination of these compounds.
The German Dump Regulation names ISO 18287 with GC/MS detection as method of choice. The alternative EN 15308 names GC/ECD detection and GC/MS detection as suitable, so the Q³ approach of the Shimadzu Scientists is according to the existing norms. The German sewage sludge ordinance asks for no interference between PCB 101 and o,p’-DDE or alpha-Endosulphane and between PCB 138 and p,p’-DDT. Most challenging, a good separation between PCB 28 and PCB 31 is required. The developed application used DIN 38 414–20 as base for sample preparation.
A lot of instrument companies rely on Restek Products, when it really matters. So, in this case, a Restek Rxi-XLB column (l= 20 m; ID = 0.18 mm; dF= 0.18 µm) was chosen to run the separation.
The original paper shows the good separation between the two PCBs 28 and 31 (R>0.94), as shown in Picture 1, and no Interferences between the named PCB and PAH compounds, although measured in one run.
|Picture 1: Separation between PCB 28 and 31||Picture 2: Chromatogram of a PCB/PAH mixture (all 5 ng/µl)|
More details about the method, the usage of Hydrogen as carrier gas and how to optimize a Q³ by setting Pseudo MRMs for PAHs can be looked up in the original paper (in German), published in Nachrichten aus der Chemie| 62 | Mai 2014 |
Using the Restek EZGC Method Translator and Flow Calculator to Support Shoot-and-Dilute GC Method Development – Going from GC-ECD to GC-MS
Hopefully some of you are following the Shoot-and-Dilute GC work (split injection) we’ve been doing in our lab, as it offers a way to keep your GC systems up longer by reducing the impact of dirty samples on inlet liner and column integrity. After giving a lecture on the technique at the recent European Pesticide Residue Workshop in Dublin, Ireland, I was challenged by an audience member to tackle Captan and Folpet using Shoot-and-Dilute GC. Captan and Folpet are two notoriously unstable pesticides that must be determined by GC because they don’t ionize well under ESI conditions for LC-MS/MS. By unstable, I especially mean under hot splitless GC inlet conditions. In addition, they fragment heavily by electron ionization GC-MS, so selectivity in complex matrices can be poor enough to mandate their determination using GC-ECD. I’ve achieved some very promising results already for Captan and Folpet with Shoot-and-Dilute GC-ECD, but that’s not what I’m here to talk about…
I’m here to announce, for the first time on ChromaBLOGraphy, the release of our EZGCTM Method Translator and Flow Calculator (MTFC), a super cool tool for GC method development. And, I want to show you how I used it in my Shoot-and-Dilute GC work by translating a method from GC-ECD to GC-MS so I could confirm some Captan and Folpet results for strawberry extracts. In short, I’m using the same nominal length column, a 15m x 0.25mm x 0.25µm Rxi-5ms, for both GC-ECD and GC-MS work. If you’re thinking, “hey Jack, just use the same carrier gas flow and oven program and the chromatograms will essentially look the same”, nope, sorry. You need to account for the vacuum-outlet of the MS and adjust the GC oven program accordingly to elute compounds at the same temperatures to avoid elution order flip-flops that could occur otherwise. This is made exceedingly simple by using the MTFC! Review the screen capture below, and then download that MTFC and try it out and let me know what you think.
This poster was a summary of 5 publications which all focused on the sources of Ghost peaks.
We received several inquiries for a copy of the actual poster, as users would like to use it in the lab as a wall poster.
Please find here the PPT slide of the poster. It can be printed locally in A0 format. Poster ghost peaks as PPT
For those that want to read the details, here are the links to the 5 publications as PDF file, all featured at Separation Science technical magazine
1 The Carrier Gas and Carrier Gas Lines: 2013-Sep.Science-jan-Ghost Peaks part1
2 The Injection Port: 2013-Sep.Science-may-Ghost Peaks part2
3 Sample Contamination and Ghost Peaks Formed by The Stationary Phase Itself: 2013-Sep.Science-sep-Ghost Peaks part3
4 Reactivity in The Column While Doing Separations: 2013-Sep.Science-sep-Ghost Peaks part4
5 Impact of Injection and Oven Parameters During Injection: 2013-Sep.Science-sep-Ghost Peaks part5
Check out the first How Dirty Are You? blog about Parafilm.
The How Dirty Are You? pipet bulb blog showed some interesting data…mainly that I need to clean my pipet bulbs and periodically replace them. I am happy to report that I have changed my pipet bulb twice since and even do some solvent rinses.
The question I posed in the initial blog was about a high intensity peak found when a latex bulb was rinsed with acetonitrile. The question I asked was what type of common additive was responsible for producing such a high signal…
Was it a Dye, Antioxidant or UV Stabilizer?
Some people indicated that they thought it was a phthalate. This is a very good guess based on the numerous times phthalates appear in blank samples, but in this case the compound was identified as butylated hydroxytoluene (BHT).
BHT is an antioxidant compound that is used in everything from rubber to food, pharmaceuticals…even embalming fluid! This stuff is everywhere.
Freedom Industries, the company responsible for this January’s large MCHM spill in West Virginia, was fined $11,000 by OSHA. Read more at VICE News.
The OSHA fines only cover violations for endangering employee safety. Environmental fines may still be forthcoming.
Throughout this summer I have the pleasure of working with our intern, Colton Myers. The soon-to-be chemistry senior at Juniata College joined Restek for some practical laboratory experience. We wanted him to work on something “cool” and “interesting,” so what better project is there than electronic cigarettes?You do not have to look very hard to find someone “vaping” on an e-cig, so these things are definitely gaining traction. Despite their explosive popularity, we have only been able to scrape up a few published reports. In fact, a fairly exhaustive peer-reviewed literature search only turned up a couple of articles. So… needless to say Colton has now spent the past month working on the analysis of electronic cigarettes. As a starting point, we worked on the analysis of the “e-juice” only (note, this is a teaser for more to come later).
So we developed an analytical method for a quick screening of e-cig solutions. We utilized SOF and our approach was KISS (keep it simple, stupid). The table below contains all the specifics of interest:
As a first pass, we tore open an e-cig; used 10 mL of methylene chloride to extract out the juice; concentrated the extract down to 1 mL; and here is what it looks like when using the above parameters:
Now… the aforementioned approach was a simple, qualitative pass for determining what was in the e-juice. We did not use any surrogate standards; however, this could be easily done in the future. In fact, these results indicated that nicotine was ~35% of the total solution, which is a far cry off from the manufacturer’s claim of 1.8%. This we attributed to our extraction/concentration procedure, but this did not matter to us, because our next approach was to just purchase some e-juice straight up (that’s right, keep up with the lingo) and analyze the raw solution, thereby cutting out any errors associated with extraction/concentration, etc… And here is what we got for a raw (i.e., unprocessed) 1.8% nicotine solution:
So what does all this mean? Well… our method worked well for the rapid analysis of the major electronic cigarette components and our analyte list matches up “fairly” well with what the manufacturer lists on their website. I say fairly because they do not list ethanol, but we clearly found it; and yes, we ran blanks to ensure this was not a contamination issue (hence, how we found water as a “contaminant”). In addition, according to our results this sample is slightly (yes, not orders of magnitude) off from the manufacturer’s claim of 1.8% nicotine in solution. However, our observation is consistent with what Trehy et al. observed in 2011 (“the nicotine content labeling was not accurate with some manufacturers”). Perhaps this is well within the manufacturer’s tolerances or maybe they do not actually test any of this, because as of now not much of the e-cig business is regulated.
Now… you may be asking “why the thick film volatiles column?”…. well I am glad you asked. Remember my teaser from before? See no one actually drinks, bathes in, or injects (I hope) the e-juice. They “vape” it (i.e., draw the solution over an atomizer and inhale the resulting vapor). So honestly, from my point of view I could really care less about what is in the raw e-cigarette solution. I am more interested in what is found in the vapor. So can you take a guess as to what may be found in later parts of this series? Stay tuned…
Trehy, M.L.; Ye, W.; Hadwiger, M.E.; Moore, T.W.; Allgire, J.F.; Woodruff, J.T.; Ahadi, S.S.; Black, J.C.C; Westenberger, B.J. Analysis of electrongic cigarette cartridges, refill solutions, and smoke for nicotine and nicotine related impurities. J. Lig. Chromatogr. Relat. Tech. 2011, 34, 1442-1458.
I recently returned from the Brominated Flame Retardant Workshop in Indianapolis, Indiana. Going to a conference that covers analytical, occurrence and fate, biological and toxicology really puts what Restek does and the products that we make into perspective. Being able to analyze flame retardants in biotic and abiotic matrices is only the first challenge. The analytical methodology and data is used to monitor the levels in humans and the environment, and that data is then used for toxicology studies. Finally, and hopefully, that data is used to form policy that will in turn protect the environment and human health. The BFR meeting covers each of these important links surrounding flame retardants and I always come home from that conference and think about the work that I do to hopefully help the analytical scientist, and the changes I can potentially make around my home and office to reduce exposure to flame retardants (and other persistent organic pollutants).
I enjoyed many of the presentations at the BFR workshop, but one in particular stood out because it is a real problem, but not one that I normally think about. Where do you send your old electronics? With the rapid pace of new technology there is now a rapid increase of electronics waste. Electronic waste (e-waste) recycling in concept is a good thing. We really don’t want all of that in our landfills and electronics contain many precious metals that can be re-used. However, as Li Li from The College of Environmental Sciences and Engineering, at Peking University presented, the process of recycling the e-waste is, in many cases, rudimentary at best. Much of our waste is being shipped to developing nations that use children for labor. The e-waste is being burned in open areas, often very close to where the working families are living. Burning the electronics and plastic casings that are coated with flame retardants and other chemicals creates a toxic smoke that contains lighter brominated diphenyl ether congeners (PentaBDE), dioxins and furans, mixed brominated and chlorinated dioxins and furans, polycyclic aromatic hydrocarbons and heavy metals (just to name a few).