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1st Quarter 2000 - Vol.8, No.1 - Circulation 4471 - Editor: Eric W. Lindsay

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Acrylamide, Acrylonitrile, and Acrolein by EPA 8316

Acrylamide, acrolein, and acrylonitrile are common monomers used in polyacrylamide (used in contact lenses), ABS rubber, and other acrylic polymers.  EPA  method 8316 can be used to test water samples or leachates for acrylamide, acrylonitrile, and acrolein.  The method uses reverse phase HPLC (high pressure liquid chromatography) with a C18 column, water as the eluant, and a UV detector at 195 nm.

While the sensitivity of this method is good, the specificity of the method is not.  This method should only be used for relatively clean water samples.   The reason why the method is subject to interferences is due to the short wavelength chosen for the UV detector.  Many organic compounds absorb in the region of 195-200 nm.  Detection limits for this method are approximately 10-30 ug/L.

Alternative test methods which offer better specificity (fewer interferences) are EPA 8315 for acrolein using DNPH derivatives and HPLC,  acrolein and acrylonitrile using purge and trap GC (EPA 8030) or GCMS (EPA 8260 or 524), and EPA 8032 for acrylamide using bromination followed by GC-ECD.  These alternatives are very sensitive methods with detection limits in the ug/L range.  The alternatives can all be applied to much more complicated samples, even chemical wastes.

WCAS offers EPA 8316 as well as some of these alternatives.  Contact us if you need help in choosing the best alternative for your environmental testing.

Using Isotope Dilution in Chemical Analysis

The technique of isotope dilution is being used more and more in our lab to improve precision and accuracy by reducing the problems with calibration and sample preparation matrix effects.  Some analytes are not well behaved during chromatography or sample extraction. Variability caused by such problems is usually compensated for in part or monitored by using internal standards and surrogate analytes.  An isotope dilution standard is the "perfect" internal standard or surrogate. 

How can that be?  An internal standard or surrogate is a compound similar to the analyte of interest.  An isotope dilution standard is an isotope of an element or a molecular compound labeled with an isotope.  Good examples of both of these are ²⁰⁴Pb and benzene-d₆.   ²⁰⁴Pb is a minor isotope of lead (Pb).  The Pb isotopes which are stable and occur naturally have atomic masses of 204 (1.4%), 206 (24.1%), 207 (22.1%), and 208 (52.4%) where the natural abundances appear in parenthesis.  By adding a known amount of ²⁰⁴Pb to a sample before testing for total Pb and by testing for each of the lead isotopes, one can accurately determine how much total Pb was in the sample.   There are a couple of catches, because nothing is ever "perfect".   One catch is that you need to use a mass spectrometer to separate analyte masses.   A second catch are that enriched isotopic standards are expensive.  The other catches are beyond the scope of this article.

In the example benzene-d₆, the hydrogens (H) normally attached to the benzene ring are replaced by deuteriums (D), an isotope of  hydrogen (²H), thus the -d₆.  In both these cases, the isotopes have almost exactly the same chemical properties as the original or naturally occurring isotopes.  They just differ in mass.  This is as close as it gets to a "perfect" internal standard or surrogate.

To give you an idea of how much the error can be reduced in a chemical analysis, consider the following.  In a gas chromatography analysis, the error from injection can be approximately 5%.  By adding an internal standard, the error can be reduced by half to approximately 2-3%.  With isotope dilution, the error should be half of that again, approximately 1%.  In the analysis of sub-ppm levels of lead (Pb) in supplements, errors from traditional approaches using ICPMS and GFAA can be 25% or more, characteristic of a trace analysis in a solid matrix.  With isotope dilution, the error is generally less than 5%.  Where ever a mass spectrographic technique can be used for analysis, isotope dilution should minimize the error.  Because of this, NIST commonly uses isotope dilution mass spectrometry for certifying reference samples.

Below are links to other WCAS articles on isotope dilution techniques using either gas chromatography-mass spectrometry (GCMS) or inductively coupled plasma-mass spectrometry (ICPMS).

• Lead in Supplements by ICPMS

• Boron by ICPMS

• 1,4-Dioxane by GCMS

• Ethylene Glycol and Ethylene Chlorohydrin by GCMS

• Volatile Organics Analysis by EPA 1666 (pdf file)

EPA 1664 vs. 413.1, 413.2, and 418.1

Many of you have asked us to explain the differences between EPA 1664 and 413.1, 413.2, and 418.1. Here is our understanding: 

418.1 is Total Recoverable Petroleum Hydrocarbons. This method includes an extraction with Freon followed by a cleanup to remove non-petroleum hydrocarbons and analysis by FTIR. This can NOT be replaced by1664.

413.2 is Oil & Grease by FTIR. This method includes an extraction with Freon and analysis by FTIR. This can NOT be replaced by 1664.  

413.1 is Oil & Grease by gravimetry. This method includes an extraction with Freon and a determination of the weight of the residue.  This CAN be replaced by 1664 although you may want to check with the regulator to make sure they will accept it.  

1664 is Hexane Extractable Materials. This method includes an extraction with hexane and then determine the weight of the residue. This is to replace 413.1.  The reason for 1664 is to lessen the use of Freon due to its harm to the environment. The bottom line in our opinion is that you need to ask your regulator if they will accept EPA 1664 to replace what you are doing now.

Laboratory Tidbits

A new phone system has been installed at our laboratory. First of all, you can always hit "0" and get the operator. Everyone now has a three digit extension which you can either ask the operator for or access the directory and spell the last name. Remember!! Hit "0" if you want help. 

Here are the extensions of some of the most frequently asked for people:

Eric - Client Services 300
Mary - Client Services 301
Craig - Client Services 302
Jack Northington - Audits 103
Ramona Northington - Lab Dir. 102

Please remember that you can always just hit "0" and access the operator, and she will be more than happy to connect you to the person you need to talk to.

Visit our web site! We are always making changes and adding articles. At the present time we are averaging about 300 visitors per day. Due to our web site we have received samples from all over the world.

Quick Quotes

A college education seldom hurts a man if he's willing to learn a little something after he graduates.  Author unknown

It is the province of knowledge to speak, and it is the privilege of wisdom to listen. Oliver Wendell Holmes

Nothing ever becomes real till it is experienced. John Keats