This post shares information on our work in the area of matrix effects.  Matrix effects in LCMS can affect sensitivity, precision and accuracy.  We have developed a simple way to monitor phospholipids and lysophospholipids which yield matrix effects.  This approach is easily used in developing MRM LC-MS-MS analyses.

I have attached several links on the internet including:

ASMS Poster Sessions:

http://littledomain.com/james/files/matrix_part1.pdf

http://littledomain.com/james/files/matrix_part2.pdf

Prepress of Journal Article:

http://littledomain.com/james/files/text.pdf

A published copy of the article can be found at J. L. Little, M. F. Wempe, C. M. Buchanan, Journal of Chromatography B, 833 (2006) 219-230.

This post shows the reference in Analytical Chemistry of a method we find very useful in our laboratory for the identification of polyesters and the quantitation of their monomer compositions.  I don’t have a reprint or prepress for this article, so you would have to order a copy.

Preparation of polyester samples for composition analysis
By: Tindall, G. William; Perry, Randall L.; Little, James L.; Spaugh, Arthur T., Jr.
Analytical Chemistry (1991), 63(13), 1251-6.

http://pubs.acs.org/doi/abs/10.1021/ac00013a013

Abstract:  A mixture of hydroxide, MeOH (methanol), and DMSO (dimethyl sulfoxide) solvolyzes polyesters at rates much faster than any reagent previously described for hydrolysis to monomers prior to analysis.  Even highly crystalline polyesters can be solvolyzed to their corresponding monomers in a few minutes with this reagent.  Three methods for the analysis of polyesters are described that use this reagent for the rapid preparation of the polymer sample.  Methods for the determination of acids, diethylene glycol in poly(ethylene terephthalate), and glycols and diacids by NMR (nuclear magnetic resonance) are described.  The reagent can be used to prepare samples for analysis by chromatography or NMR.

I originally started my website to share my experiences sailing on Watauga Lake, a TVA lake in northeast Tennessee.  Over time, I devloped a website for our Watauga Lake Sailing Club.  During that time, we acquired a Catalina Capri 14.2, an O-Day 272, a Catalina 270, and a J40.  We currently regained some sanity and own only the latter two boats..

We currently own the J40 named Ragtime which we keep at Charleston Harbor Marina and the Catalina 270 name Wild Blue Yonder which we keep at Watauga Lake.  Take a look at 

Link to “Littles’ Fleet”

http://littledomain.com/wlsc/littles_fleet

Watauga Lake Sailing Club:

http://wlscjibsheet.wordpress.com/

 J/40 Users’s Site:

http://members.dslextreme.com/users/sded/

This posts describes techniques we find useful for the identification of a wide variety of surfactants in commercial products. More recently, I have found that accurate mass MS/MS data and molecular formulae searches in CAS can be very useful.  Especially in you search one of the lower MW species in a PEG series using “Known Unknown” approach in SciFinder.

We originally developed many different techniques for the identification of surfactants in commercial latex plants.  After we no longer needed the technology, I developed a course for PittCon and have included some links below:

List of Class Resources:

www.littledomain.com/pittcon.htm

Class Notes:

http://littledomain.com/james/files/pittcon/text.pdf

Class Powerpoint Presentation:

http://littledomain.com/james/files/pittcon/power_point.pdf

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SAFETY NOTE:  Diazomethane is a dangerous chemical.  Extreme caution should be taken in handling and using this compound.  Here is information on safety from Wikipedia:

“Diazomethane is toxic by inhalation or by contact with the skin or eyes (TLV 0.2ppm). Symptoms include chest discomfort, headache, weakness and, in severe cases, collapse.  Symptoms may be delayed. Deaths from diazomethane poisoning have been reported. In one instance a laboratory worker consumed a hamburger near a fumehood where he was generating a large quantity of diazomethane, and died four days later from fulminating pneumonia.  Like any other alkylating agent it is expected to be carcinogenic, but such concerns are overshadowed by its serious acute toxicity.”

“CH₂N₂ may explode in contact with sharp edges, such as ground-glass joints, even scratches in glassware.  Glassware should be inspected before use and preparation should take place behind a blast shield. Specialized kits to prepare diazomethane with flame-polished joints are commercially available.  The compound explodes when heated beyond 100 °C.”

 http://en.wikipedia.org/wiki/Diazomethane

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This post summarizes artficats (reaction by-products) noted in our laboratory.  It was a handout for an ASMS poster session from a conference.  Diazomethane and Trimethylsilyldiazomethane reactions are often employed to increase the volatility and stability of organic acids for gas chromatography mass spectrometry. Normally the reactions give the desired methyl ester derivatives. However, sometimes artifacts (by-products are noted.

The paper linked below lists all the types of artifacts noted in our laboratory in the last 15 years and ones we have found in the literature. Also, convenient methods for producing small amounts of diazomethane and for utilizing both reagents are described.

http://www.littledomain.com/james/files/diazoalkanes.pdf

This post summarizes the identification of silylation artifacts from our laboratory and the literature.  Normally silylation derivatization reactions  give the desired derivative in high yields. However, sometimes artifacts (by-products) are formed.

The paper linked below lists all the types of artifacts noted in our laboratory in the last 20 years and ones we have found in the literature. It is a modified (not refereed) copy of a paper [J.L. Little, J. Chromatogr. A, 844 (1999) 1-22] containing additional examples found since the paper was published.

http://www.littledomain.com/james/files/silyl.pdf

This post describes the method we routinely employ to identify unknowns.  We refer to those known in the literature, but unknown to us as “known unknowns.”   The term originated from a speech by Donald Rumsfeld:

http://en.wikipedia.org/wiki/There_are_known_knowns

We published our findings in the Journal of Mass Spectrometry in 2011 and presented the initial results at the ASMS meeting in Salt Lake City, Utah in 2010.

The article was featured on the cover of the Feb 2011 JASMS:

Prepress Version of ASMS Article:

http://www.littledomain.com/james/files/known_unknowns_article.pdf

Poster Session ASMS 2010:

http://www.littledomain.com/james/files/known_unknowns.pdf

New July 2011!  Searching CAS Registry by Formula Weight:  A little known fact that can search SciFinder by formula weight by ”tricking” interface.  Not as good as being able to search by monoisotopic MW, but can be useful occasionally

http://www.littledomain.com/james/files/formula_weight_scifinder.pdf 

Prepress of ChemSpider Article:

http://littlemsandsailing.wordpress.com/2011/05/22/accurate-mass-measurements-identifying-%e2%80%9cknown-unknowns%e2%80%9d-using-chemspider/

Link to Work with NIST and New Exact Mass Software in Version 11:

http://littlemsandsailing.wordpress.com/2011/08/27/using-new-nist-exact-mass-search-to-identify-known-unknowns/

This post includes information on the choice of amines as chemical ionization reagent gases and the building of a CI manifold.  Also, see section in The Encyclopedia of Mass Spectrometry, Volume 4, Fundamentals of and Applications to Organic (and Organometallic) Compounds, Edited by M Gross et al,  “Deuterated Ammonia Chemical Ionization:  Use in Counting Exchangeable Hydrogen Sites on Organic Compounds,” p 772-780, D. M Parees, A. Z Kamzelski, J. L. Little, 2005

Ammonia is normally adequate for most applications.  However, gas mixtures of other alkylamines with methane can yield less fragmentation data and resolve ambiguous ammonia CI data.  Deuterated ammonia and alkyl amines can distinguish isomeric compounds in some cases.

Tips for Using CI Gasses:

http://www.littledomain.com/james/files/cigas.pdf

We use a wide variety of chemical ionization gases in our laboratory for the molecular weight determination of unknowns. In the link below, a versatile chemical ionization manifold is described that can be retrofitted to any commercial mass spectrometer. The paper includes plans for building it, operating it, and maintaining it.

Plans for Building Custom Manifold:

O manifolds supplied as by the manufacturer will not function properly. In many cases, it is due to the incompatibility of o-rings in the gas solenoids. We use a custom manifold on many of our GC-MS instruments.  Here is some information on building and using the manifold:

http://www.littledomain.com/james/files/manifold.pdf

The most current interface is easier to build than the one described in the above PDF document.  Here is a picture of the current interface which is utilized on our Thermo DSQ GC-MS:

Charter Communications totally destroyed my web page.  Here is an archived link to the old page, but some content was lost..

http://web.archive.org/web/20090122212357/http://users.chartertn.net/slittle/

Thus I decided to start all over with a new look in WebPress.  I had used the software to created our Sailing Club Webpage, and found easy to use:

Sailing Club Website:

http://wlscjibsheet.wordpress.com/