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Vacuum Distillation


SW-846 Method 8261A
SW-846 Method 5032
SW-846 Method 8260C
PATENTS
REFERENCES

1,4 DIOXANE
VOC's in Milk
VOC's in Soil
TRAINING
VACUUM DISTILLATION
ADVANTAGES OF VACUUM DISTILLATION
SUPERFUND EVALUATION
INTERNAL STANDARDS FOR METHOD 8261
 
 

1,4 – DIOXANE ANALYSIS

Analytical Methods

U.S. EPA Fact Sheet

Comparison - VOC  Methods

Florida DEP Report On VOC Methods Comparison

Basic Information On 1,4 Dioxane

COMPARISON OF COMMONLY USED VOC TECHNIQUES FOR THE ANALYSIS OF 1,4-DIOXANE



EPA 8261A

 

EPA 8270
EPA 8260C
Selected Ion
Monitoring
EPA 8260C
Modified
Method

EPA 1624
MDL
0.5ug/L-Soils
1.1ug/L-Water

1.0-0.23 ug/L


0.5-10.0 ug/L

20-100 ug/L


-

PQL
1 ug/L
0.5-0.2 ug/L
30 ug/L
30-100 ug/L
1 ug/L
Sample
Volume

5 mL or
25 mL


1000 mL

 2 samples
40 mL each

2 samples
40 mL each
2 samples
40 mL each
Sample prep
technique

Vacuum distillation
Liquid-Liquid extraction

Purge & Trap


Purge & Trap
Purge & Trap
Heated
Method drawbacks

NONE

Very time consuming
Poor Purging efficiency
Poor Purging efficiency Poor Purging efficiency
Method reliability
Most reliable
Built in QA


Reliable

UNRELIABLE
Hit-and-miss

UNRELIABLE
Hit-and-miss
UNRELIABLE
Hit-and-miss
Cost per sample

LOWEST


HIGHEST


HIGH


HIGH

HIGH
EPA Approval

APPROVED

NOT APPROVED

APPROVED

APPROVED

APPROVED

Vacuum distillation using EPA Method 8261A addresses all the shortcomings of Purge & Trap and Static headspace. Especially the issue of 'matrix effects'.

The main advantages of using Method 8261A for 1,4-Dioxane analysis are:

  • No method modifications are required to analyze 1,4-Dioxane. In fact, a suite of 90 plus VOCs, including 1,4-Dioxane, are analyzed in a single run.
  • Method detection limits of 0.2 ppb with QA are possible, using vacuum distiller model VDC1012 in conjunction with HP5973 or newer mass spectrometer.
Vacuum Distillation using Method 8261A can very efficiently & routinely analyze 1,4-Dioxane from all types of matrices, including ground and drinking water samples. EPA Method 8261A has been shown to be far superior and very accurate for the analysis of 1,4-Dioxane.

Florida Department of Environmental Protection comparison study of EPA Methods 8261A, 8270 and 8260C

Recently, Florida Department of Environmental Protection conducted a comparison study of EPA Methods 8261A, 8270 and 8260C, for the analysis of 1,4-Dioxane. Ref: "1,4-Dioxane - Environmental and Measurement issues" - Timothy W. Fitzpatrick & Dr. Kerry Tate of Florida Department of Environmental Protection"

The study conculded that:

  "8261A is an excellent quantitative method"

ADVANTAGES OF METHOD 8261A
  • MDL < 2.0 ug/L or better with SIM
  • Minimal sample preparation
  • 1,4-Dioxane can be analyzed within allowable method constraints (no alternate test procedures)
DISADVANTAGES OF METHODS  8260C & 8270
  • EPA recommends against the use of method 8270
  • Labs can not be accredited for 1,4-Dioxane by means of 8270
  • 'Salting' has very little effect on purging efficiency using 8260C
  • Low recovery for 1,4-Dioxane despite using heated purge and SIM
  • Method 8260C is prone to interferences
  • Heated purge temperature shortens trap life
  • Method 8260C recoveries are temperature & matrix dependent (consequently unreliable}




WHAT IS 1,4-DIOXANE?

  • This is an 'Emergent Pollutant' of concern to the US EPA.
  • 1,4-Dioxane is a man made compound and does not occur naturally.
  • Mostly used as a chlorinated solvent stabilizer.
  • About 10% of 1,4-Dioxane produced, is used in personal care products.
  • Millions of pounds of 1,4-Dioxane are manufactured in the US alone.
  • Other names - 1,4-diethylenedioxide, p-dioxane, 1,4-dioxacyclohexane, Diethylene ether.
  • 1,4-Dioxane is classified as a probable carcinogen by the US EPA
CHEMICAL / PHYSICAL PROPERTIES
  • Highly soluble in water & not easily biodegradable
  • Molecular weight - 88.11
  • Density - 1.03
  • Boiling point(760) - 101.1C
  • Vapor Pressure - 29 mm of Hg @20C
  • Flammable liquid

For the past few years, there has been considerable interest in this little known compound in the United States. 1,4-Dioxane is a solvent commonly found in cosmetics, toiletries, paints and varnishes. 1,4-Dioxane is also used as a stabilizer for volatile compounds such as TCA.

The US EPA classifies 1,4-Dioxane as a probable carcinogen. 1,4-Dioxane can enter the subsurface and potentially impact drinking  water aquifers when it's host solvent TCA is released through spills, leaks or existing disposal practices. Unlike TCA, 1,4-Dioxane readily leaches into ground water and does not adsorb significantly into soil particles.

One of the most disturbing aspects of 1,4-Dioxane is that it is a man made compound that is not easily biodegradable.

Existing VOC techniques(except 8261A) such as Purge & Trap, in spite of their widespread use, are neither reliable nor accurate. The same types of samples when analyzed by different laboratories using Purge & Trap, can produce results that vary by as much as three orders of magnitude. Many states in the U.S., like California and Massachusetts  now require detection of 1,4-Dioxane between 1 and 5 ppb levels. These levels are not detectable reliably using Purge & Trap or any other existing method except liquid-liquid extraction using SIM mode and Method 8261A. A comparison  table of currently used methods (shown below) clearly demonstrates the superiority of the new EPA Method 8261A for 1,4-Dioxane analysis.

In spite of severe drawbacks with the existing methods, most laboratories continue to use Purge & Trap for 1,4-Dioxane analysis, thereby doing a great disservice to their customers. This is understandable if no other methods, or better options were available. However, over the last few years, this is no longer the case for analyzing 1,4-Dioxane or  for that matter, all VOCs in general.

Fortunately, recognizing the shortcomings of Purge & Trap and static headspace, the US EPA has developed a new VOC analytical technique using vacuum distillation in conjunction with GC/MS. This rugged new VOC technique has built-in quality assurance features and has been adopted as an official method in RCRA's SW-846 manual of Methods.



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