Archive for the ‘Miscellaneous’ Category

Electronic Cigarettes Part V: Vapor Analysis – Yes… we found formaldehyde too!

It has been over 3 months since the last electronic cigarette blog. I will spare you the excuses. However, I can proudly say that we will be releasing a full application note on electronic cigarettes in the very near future (i.e., 1 to 2 months hopefully). In the meantime I feel obliged to respond to all the various inquiries I have received from colleagues about the presence of formaldehyde in electronic cigarettes. Lately I hear things like “oh I just heard on NPR about formaldehyde in electronic cigarettes… is this true… did you know that?”  Well… obviously you already know my answer to this hot topic question. So allow me to indulge…

In parts I II III and IV of this blog series we covered analyzing the e-juice for nicotine and impurities. In the last e-cig blog we saw that electronic cigarette solutions contained numerous impurities. At that point in time we did not go into a lengthy discussion on what compounds were found and their potential implications for human health. Why you ask? Well because theoretically no one is drinking the e-juice… nor is anyone bathing in the e-liquid… and lastly I doubt anyone is injecting the e-solution. The main route of exposure to e-cigs and any compounds of interest is the direct result of the vaporization process, whereby with the use of a heated filament, the liquid is turned into a vapor which the end user inhales. Despite the aforementioned, the majority of e-cig research has focused on analyzing the e-juice. However, now that the knowledge of formaldehyde in the vapor has hit the mainstream media, perhaps that paradigm will change. FYI – Anyone interested in further reading or references should just reach out. Now… after much delay and teasing here is what we have seen in the e-cig vapor:

E-Cig Vapor A

I know… boring. So how about we zoom in:
E-Cig Vapor B

Based on the above chromatogram our e-cig vapor has a lot more constituents than the manufacturer’s juice listing of propylene glycol, glycerin, and nicotine. No surprise here, we already saw this trend when analyzing the raw solutions. NOTE: these vapor results are for the exact same e-juice results presented in our last e-cig blog. So what are all of these peaks? Well… the following table will hopefully help break down all the unknown compounds into several more digestible sections. Note: We only included tentative compounds with a mass spectral quality of 80% or greater according to the NIST 2005 database. Compounds with 100% quality have been confirmed with standards.

E-Cig Vapor Table A

We found 82 unidentified and identified (some only tentatively) compounds in the e-cigarette vapor for this manufacturer. Of particular interest was the presence of formaldehyde, acetaldehyde, acrolein, as well as several siloxanes. All of which we did not find in the raw e-juice.

So… what does this all mean? Oh… and how did we measure the vapor? This time I promise to come back sooner than three months to answer these questions.

QuEChERS – Where to start?

Food-art-22Enjoy the tip!*

I am often asked for QuEChERS product recommendations. Usually the request is something like, “I need to test pesticides in _____” and that blank can be just about anything…sometimes not even food.

Unless it is something I have tested before, I usually take a quick look online to determine the approximate composition of the food. I do this because standard QuEChERS methods work best for high water, low lipid, and low carbohydrate commodities. The general recommendation is that the sample should contain about 80% water. If this isn’t the case, then adding some water is helpful and often needed for the extraction to work properly. In addition, high lipid samples can be challenging and you want to have a high level of C18 in your dispersive cleanup step.

The USDA Nutrient Database is a great resource for finding this information. Many foods are included and values for water, protein, lipid, carbohydrate, fiber and sugar levels are typically listed. The really great part is that these values are listed on a 100 g basis so the values are the same as percent weight.

I started checking this every time I test a different food because looks can be deceiving. The first time I tested spinach, I thought it looked “dry”. When I checked the USDA nutrient database, I saw spinach was listed at ~90% water. I was surprised. I did not add any water and the extraction worked perfectly.

In addition to water content, I take a look at the lipid and sugar values. If the lipid is “high” (above ~5%), I want to make sure to have some C18 sorbent in my dSPE tube to help remove coextracted lipids. Sugar is removed by PSA sorbent so knowing this value will help determine the amount of PSA in your cleanup.

 

U.S. Department of Agriculture, Agricultural Research Service. 2014. USDA National Nutrient Database for Standard Reference, Release . Nutrient Data Laboratory Home Page, http://www.ars.usda.gov/nutrientdata

*Amazing food art found at http://myhoneysplace.com/food-art-pictures/food-art-22/

 

Determination of Chloropropanols in Soy Sauce: Part 1, Enter The Matrix

A while back I was doing some reading and came across an application of GC-MS in food safety that caught my attention. The analysis of food products, specifically soy sauce, for contamination with chloropropanols. So how do chlorinated alcohols end up in food?

During the production of a food ingredient known as  hydrolyzed vegetable protein (HVP) various vegetable protein feedstocks such as corn gluten, wheat gluten, and soybean meal are combined with dilute  HCl and heated at around 100° C. This process causes hydrolysis of the peptide bonds within the bulk protein leading to a mixture of short peptides and free amino acids. We perceive the presence of free amino acids as an umami flavor and so HVP is often added to foods in order to give a more rich or meat like taste.

Problems can arise when process parameters like the strength of the acid, reaction time, temperature, and  the level of residual lipids in the feedstock are not well controlled. Residual lipids can undergo the following reactions in which the released glycerol is chlorinated. formation mechanism

Most analytical work and regulations in this area focus on the compounds 3-chloro-1,2-propanediol (3-MCPD) and 1,3-dichloro-2-propanol (1,3-DCP) although other structural isomers are known to occur as well as species in which one or more fatty esters remain bound. The European Commission has set an upper limit of 0.02 mg/kg for 3-MCPD in soy sauce and HVP on a dry matter basis and requires analytical methods to achieve an LOQ of 0.01 mg/kg. Assuming our soy sauce under test is 40% dry matter, the LOQ would be 4 ppb on a liquid basis.

The state of analytical methods for these compounds in soy sauce and other food matrices has been  advancing in recent years, however many still rely on large volumes of extraction solvents which can be expensive and unfriendly to work with. My goal for this project is to develop a method for determining chloropropanols in HVP based soy sauce using a QuEChERS extraction with acetonitrile followed by dispersive sample cleanup, derivatization with heptafluorobutyric anhydride (HFBA), and finally GC-MS analysis. I also hope to incorporate the shoot and dilute concept which entails running the GC inlet in split mode to reduce buildup of nonvolatile sample components on the inlet liner and column.

A tall order indeed! I began by extracting 10 G portions of both traditionally brewed and HVP based soy sauce using the standard unbuffered QuEChERS procedure. Traditionally brewed soy sauce is made by fermentation and should be free of any incurred chloropropanols while HVP based products have the potential for contamination. The traditionally brewed sample will serve as a blank matrix for calibration and method development.

P1020850

Soy sauce extraction following 1 min shake, before addition of salts. HVP based on the left, traditionally brewed on the right.

P1020856

Soy sauce extraction after addition of salts, 1 min shake, and centrifugation. HVP based on the left, traditionally brewed on the right.

 

 

Giving those extracts the highly scientific eyeball test hints that we are in for quite a challenge. Keep following my series of blogs on this project as things progress and feel free to comment or contact me if you are interested in this analysis or perhaps have even run it yourself.

Here are some references for those  interested in reading up on the issue.

IARC Monograph, 2012, 101, 349

EFSA Journal, 2013, 11(9), 3381

AOAC official method 2000.01

Journal of Chromatography A, 952 (2002), 185–192

Food Control, 18 (2007), 81–90

 

HPLC columns for the European Pharmacopoeia methods

European Pharmacopoeia (EU) methods tend to be vague in their description for column requirements, which can make choosing the correct column a little tricky.   To simply things, I listed the Restek HPLC columns that best match the columns (phases) listed in the European Pharmacopoeia “Reagents” chapter. Hopefully this makes it a little easier to choose the correct column for your particular EU method. If you have any questions, simply send them to support@restek.com or contact your local distributor.  For GC column suggestions for the EU methods, refer to our GC capillary columns for the European Pharmacopeia methods post. Thank you.

 

Nomenclature Reference Code Restek HPLC Column
Silica gel for chromatography 1076900 Ultra Silica
Silica gel for chromatography, octadecylsilyl 1077500 Ultra C18
Silica gel for chromatography, octdecylsilyl R1 1110100 Ultra C18
Silica gel for chromatography, octadecylsilyl, base-deactivated 1077600 Ultra C18
Silica gel for chromatography, octadecylsilyl, end-capped 1115400 Ultra C18
Silica gel for chromatography, octylsilyl 1077700 Ultra C8
Silica gel for chromatography, octylsilyl R1 1077701 Ultra C8
Silica gel for chromatography, octylsilyl, base-deactivated 1131600 Ultra C8
Silica gel for chromatography, octylsilyl, end-capped 1119600 Ultra C8
Silica gel for chromatography, trimethylsilyl 1115500 Ultra C1
Silica gel for chromatography, aminopropylsilyl 1077000 Ultra Amino
Silica gel for chromatography, nitrile 1077300 Ultra Cyano
Silica gel for chromatography, nitrile R1 1077400 Ultra Cyano
Silica gel for chromatography, nitrile R2 1119500 Ultra Cyano

 

How Dirty Are You? Part 4…Manual Syringe Rinsing…The Answer

So how many times do you need to rinse a syringe?

Well, I can tell you the answer for the experiment we did. Let me first refresh your memory on specifically what we did.

Sequence of manual syringe rinsing:

1. 20 µL draw of a 500 ppm hydrocarbon standard and expel it
2. 20 µL draw of acetonitrile – eject into sample vial – test via GC-FID
3. Repeat step 2 many times

Each “rinse” was tested via GC-FID.

How many 20 µL acetonitrile rinses were needed to show no signal (FID)?

The answer is 4.

 

I want to thank everyone that commented when I posed the question. Most people were right on track with about 4 rinses. It is also funny that people tended to do “extra” rinsing regardless of what they thought was required. I still do this with about 6 to 10 rinses depending on the situation.

I wanted to share some helpful hints from people who commented:

  • Use more than one rinse solvent especially in situations were analytes have a wide range of polarity
  • Use more than one rinse vial
  • Use the same solvent for rinsing as is used for the sample and standard solutions

Here is a chromatogram of a 50 ppm hydrocarbon standard followed by chromatograms of consecutive rinses. The 50 ppm chromatogram can be used as an intensity reference because the y-axis is the same for all chromatograms.

50ppm

rinse1v2rinse2v2rinse3v3rinsetable

How Dirty Are You? Part 4…Manual Syringe Rinsing…The Question

reanimator

I don’t even want to guess how many times you would need to rinse this syringe before removing all traces of reanimation “reagent”

This How Dirty Are You? blog should really be credited with inspiring the entire project. I was discussing the number of times I rinse my syringes with a colleague, Michelle Misselwitz, a few years ago. We were working in the same hood and I noticed that she rinsed her syringe a lot…I do too. I was even reminded of my rather obsessive rinsing at Thanksgiving this year. I was washing a few dirty dishes by hand and my mother mentioned that I was rinsing them a lot…and that my grandmother would have been upset because I was wasting so much water…but “What about the soap residue?” I said.

Over the years, I have been told different things about the number of times a syringe should be rinsed to prevent carryover/contamination…and I have been asked the same question many times. I was told early in my lab career that 7 was the magic number…so just to be sure, I got in the habit of using 10 rinses.

What We Did

There are a lot of variables to consider…sample matrix, compound concentration, sample solvent, rinse solvent(s), rinse volume etc. But to keep things simple, we used a hydrocarbon standard at a high level and rinsed with the same solvent as the sample solution, acetonitrile. We also defined the volume of a “rinse” as 20 µL. We started the experiment with a 20 µL draw of a 500 ppm hydrocarbon standard. The hydrocarbon standard was expelled and then consecutive rinses were performed. Each rinse was tested by GC-FID.

Sequence of manual syringe rinsing:

1. 20 µL draw of a 500 ppm hydrocarbon standard and expel it
2. 20 µL draw of acetonitrile – eject into sample vial – test via GC-FID
3. Repeat step 2 many times

Question

Post or Email me with your answers and look for the data in my next blog.

1. How many 20 µL acetonitrile rinses were needed to show no signal (FID)?

 (Hint: The answer is between 1 and 15…I didn’t say it was a good hint.)

 

 

 (photo credit: http://philosophicalasides.blogspot.com)

Lab Hack: Quickly Reducing GC Inlet Pressure on an Agilent GC Prior to Changing the Septum and/or Inlet Liner

Have you ever been changing your Agilent GC inlet liner (you do change that routinely, right?), particularly a single taper with wool type, and pulled it out to see the wool at the top of the liner (Figure 1) when it should be at the bottom of the liner (Figure 2), the proper placement where injected sample can hit it and be transferred to the GC column?  How does this occur?  Sudden depressurization of the GC inlet can cause the wool to pop to the top of the liner.  It probably doesn’t matter if this happens when you’re changing the liner, since you’re going to throw the old liner away, but it can also happen when you’re changing the GC inlet septum if you haven’t properly depressurized the inlet, and then unknowingly you’re left with the liner wool at the top of the inlet, where it’s not effective for its purposes of keeping the sample from hitting the bottom seal (where compounds like DDT can degrade), heat transfer, and preventing nonvolatile “dirt” from collecting on the head of the more expensive GC column.

In the following sets of figures, I’ll show you how I depressurize my Agilent 6890 GC inlet to prevent the inlet liner wool from jumping up.  As always, it is much better to completely cool all heated zones before inlet maintenance procedures.

Go to the Agilent GC Keyboard, and press “Col 1” (Figure 3), depending on the Column and Inlet in use.  You’ll see the Display showing similarly to Figure 4.  If necessary, use the “Up” or “Down” symbol key on the Keyboard to move the Display arrow to “Pressure” (it is on “Flow” in the Figure 4 example).   When the Display arrow is on “Pressure”, use “0.1 Enter” (or even “0 Enter”) from the Keyboard (Figure 5), which should cause the Pressure to drop down relatively quickly, but not so quickly that it causes the inlet liner wool to move (the pressure does not drop all the way to zero, typically, Figure 6).  [Note:  On newer Agilent GCs you may hear the “rattlesnake” as the pressure drops.]  Use the “Up” symbol key to move the Display back to “Pressure” and then press “Off” on the Keyboard (Figure 7).  Again, the “Pressure” may not completely zero out, but the GC inlet is now ready for a septum and/or liner change.  Why don’t we just use “Off” immediately instead of “0.1”.  When you use “Off” the pressure bleeds off very, very slowly through the GC column and if you open the inlet too soon the liner wool can move in the liner.

Don’t forget to restore pressure/flow before you heat the GC inlet and column up, and it’s always good to leak check after inlet maintenance.

Fig 1x


Fig 2x




Fig 3


Fig 4


 


Fig 5xx


Fig 6



Fig 7


Fig 8

Need help finding the correct ferrule to install your GC column? Part 1: Agilent GC ferrules

You’re ready to install a column into your GC and realize you do not have ferrules to do the job. But which ferrule do you choose?  The parameters to consider when choosing the correct ferrule are instrument make and model, nut size and type, ferrule material, and column ID size. A visit to our ferrules home page will provide a general overview of variety of ferrules offered by Restek.  By navigating the page, you can narrow the selection by choosing these parameters. This is the first in a series of posts that will hopefully make this selection process easier. We begin with Agilent systems because they have more choices available.

Capillary Column Ferrules

For this section, I will assume the GC is already configured to install capillary columns with 1/16 inch fittings. Restek offers two options on nuts and ferrules for Agilent capillary column installation. There are compact ferrules and standard ferrules, each with their own style of nut. The compact ferrule and nut are considered the Agilent-style. The broad taper on the compact ferrules was designed to match the taper on the bottom of the inlet seal. Standard ferrule and nut can also be used effectively on an Agilent system.

Here are the visual differences between the standard and compact ferrules:

Standard                                                                         Compact

standferrule                                                             Compferrules          

Capillary Ferrules                                   Compact Ferrules (Fit ≤ 0.28mm ID Fused Silica Columns)

                                                                Compact Ferrules (Fit 0.32mm ID Fused Silica Columns)

                                                                Compact Ferrules (Fit 0.45/0.53mm ID Fused Silica Columns)

 

Here are the catalog numbers of the corresponding applicable nuts:

FTnut                    capnut                 hotswapFT2nut

 

Finger-Tight Capillary Column Nuts Capillary Column Nuts Hot Swap Capillary Column Nuts Looped Finger-Tight Capillary Nuts
Brass Stainless Steel
Standard Ferrules 21041 21879 20883 22347 21312
Compact Ferrules 21040 21878 21884 22348 21311

 

This is a cross-cut look at the insides of the standard capillary nut and shows the length of the ferrule and the depth of the nut hole. This helps to show how necessary it is to match the ferrule with the proper nut; otherwise there will not be an adequate seal. If you are unsure which of these nuts you have on hand to install your columns, take note the Agilent style nut has a notch on the hex-nut portion, the standard does not.

 

comp                                     stand

 

“Compact”  Agilent-style Ferrule and nut                       Standard  ferrules and nut

 

Once you’ve matched the nut type to the correct ferrule type, now we need to match the capillary column ID to the ferrule ID. The table on sizes below gives an overview of how to match fused silica and MXT capillaries.

 20141121105433156

The next step in determining the correct ferrule is the material. The chart below explains the differences between the material choices. For installation into the inlet and most detectors, either graphite or the softer 60/40 vespel graphite should work fine. For GC/MS, it is recommended to use the standard, long ferrule vespel/graphite installed with an MSD source nut.  This material is a good fit for MS because it will not fragment or allow oxygen to permeate into the system under vacuum applications.

Agilent has suggested that 100% vespel ferrules be only used for isothermal analysis.

MSD Source Nut

20643_ph_co_msd

20141118133453588-21

A note on the Agilent TCD, it has an 1/8 inch compression fitting port. In order to use our Agilent style or standard design nuts and ferrules you would need to have the Agilent supplied adaptor fitting. Restek does not have that fitting. Alternatively, Agilent does supply a two piece ferrule to install capillary column with a 1/8 inch compression nut. Restek does not sell the two piece ferrule and we do not recommend using a one piece graphite reducing ferrule.

 

Packed Column Ferrules

Typical Agilent packed column inlets are sized to accommodate ¼ inch OD packed columns; verify the fitting size of your inlet and detector. Agilent systems generally use standard compression style nuts and ferrules. If you doing on column injections, installing a 3/16 or 1/8 inch OD column will require inlet adaptors to center the column inside the ¼ inch injection port. If your instrument is equipped with an adaptor with a glass insert, on column injection will not be necessary, therefore a nut and ferrule would be all that is required to connect the column. Again you will need to verify the size nut and ferrule required. If you are installing a packed column into a capillary column inlet and detector we suggest a pig-tail configuration.

Notes on Agilent detectors- verify the size of the fitting required to connect the column. Agilent TCD’s for example are 1/8 inch compression fittings. If you want to install a 3/16 packed column, make sure your detector is adapted to accommodate ¼ inch packed column so you can use a reducing ferrule and ¼ inch nut.

Packed Column Inlet Adaptor

inletadaptorkit_ph_co_pak

In summary, the key points to remember are:

  • Match the ferrule with the proper nut
  • Know the ID of your column to match with the correct ferrule size.
  • Know system requirements for the ferrule material.
  • For packed columns: Verify the fitting sizes of you inlets and detectors.

 

Look for future posts on nuts & ferrules for other instrument manufacturers. Thanks for reading.

I would like to thank my Colleague, Erin Herrold for her assistance and insight with this blog post.

How Dirty Are You? Part 3…Gloves…The Answers

Read The Question first…

Let’s review…we soaked small pieces of different gloves in acetonitrile for 30 minutes. The samples were tested using GC-TOFMS. For relative intensity, a dashed line at the peak height of a 2 ppm PAH standard is drawn on the chromatograms.

Which gloves produced the worst background? GREEN GLOVES

gloves1

Bright green, yellow latex and royal blue gloves had similar background levels even though the chromatograms look different. Baby blue gloves and green gloves had higher background. Green gloves had the highest intensity background peaks. Let’s look at the data…

brightgreen cgram

 

yellow glove

 

 

 

royalblue

 

 

 

babyblue

 

green2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I have to admit that I was a bit surprised at the answer to the next question. Several people emailed me answers and UV stabilizers was the most popular choice. However, we saw several antioxidant compounds in the glove samples. A couple of compounds are shown below. Check out the signal from antioxidant “Nocrack NS 6″ in the baby blue gloves!

Antioxidants are added to rubber to prevent oxidative damage that degrade the physical and mechanical properties of rubber materials.

q2 gloves

 

glove antiox 1 glove antiox 2

 

 

 

Philae: Goodnight but Not Goodbye. Unlocking the Origins of Life: Comet 67P/Churyumov-Gerasimenko

Rosetta's Philae on the surface of 67P/C-G. Photo Courtesy of ESA (European Space Agency).

Rosetta’s Philae on the surface of 67P/C-G. Photo Courtesy of the European Space Agency.

On September 28th, 1969 a bright fireball exploded, shaking houses as it lit up the daytime sky outside of Murchison, Australia. Over the next forty-five years scientists have studied the Murchison Meteorite and found 14,000 compounds to include 92 different amino acids. Of the amino acids discovered, only 19 are found on earth. This rock, and evidence from other encounters with space objects, reveals that life-forming amino acids may have originated deep in space even before the formation of the sun.  In addition amino acids have been found on Saturn’s moon Titan, comets and newly forming stars (Large Molecule Heimat, Sagittarius B2).

Comets are of specific interest because they are the oldest objects in the Solar System, preserving four-billion-year-old organic molecules. Comet 67P/Churyumov-Gerasimenko is a short period comet (Jupiter Family) with an orbital period of 6.5 years. These objects are believed to originate from the Kuiper belt, a region of icy rocks just outside of Neptune’s orbit. A collision with another object can cause these rocks to fall into orbit around the sun.

Philae’s COSAC (Cometary Sampling and Composition) experiment was able to analyze samples taken from below the surface of the comet before the batteries died from lack of sunlight. ESA (European Space Agency) reported the lander bounced and is located under a cliff where it only receives 90 minutes of sunlight every 12 hours. When Philae receives enough sunlight it will again power up and send a signal to Rosetta. The last transmission was received on Friday, November 15th but ground control confirmed that COSAC sent back analytical data.

Striking images of Philae's harrowing journey to 67P/C-G. Courtesy of European Space Agency.

Striking images of Philae’s harrowing journey to 67P/C-G. Courtesy of European Space Agency.

Restek in Space: http://www.restek.com/news/view/?p=851

Comet Impacts May Have Jump-Started Life on Earth

http://www.space.com/20102-comets-impact-earth-life.html

Amino Acid Detected in Space

http://physicsworld.com/cws/article/news/2003/aug/11/amino-acid-detected-in-space

New Organic Molecule in Space

http://www.mpg.de/567495/pressRelease20080325