bill.r.miller@gm.com 

02/17/2006 10:14 AM

	

To

James Michael/DC/USEPA/US@EPA

cc

Subject

Comparison of Formaldehyde Methods AOAC 931.08 and SW-846 Method 8315









Jim,

Attached is John Gumpper's (John has a company in Salt Lake City, UT
called ChemVal and he has done our data validation on the most recent 8

delistings) assessment of the two (2) formaldehyde methods. I believe
this supports what we discussed during our call on 1-31-2006 with Todd
Williams (GM Worldwide Facilities Group).

Please let me know if this meets your needs.

Best Regards,

Bill

William R. Miller III, Ph.D.

General Motors Corporation

Worldwide Facilities Group

GM Technical Fellow

100 Saturn Parkway (MC M-20)

Spring Hill, TN 37174

E-Mail Bill.R.Miller@GM.Com

Desk: (931) 486-7471

Mobile: (931) 206-0549

Fax (931) 486-5069

(See attached file: Formadehyde Paper from John Gumpper 2-17-20062.doc)

Comparison of AOAC Method 913.08 and EPA Method 8315 for analysis of
Formaldehyde

Introduction

Formaldehyde has been included on the list of required target analytes
for F019 Wastewater Treatment sludge delisting petitions at many of the
automotive assembly plants that have been delisted.  In some of the
earliest delistings, the method used to determine formaldehyde was an
adaptation of the AOAC Method 931.08.  Later delistings relied up on EPA
Method 8315.  Sludge analyzed by the AOAC method yielded results for
formaldehyde that were significantly higher than those obtained by the
EPA method.  This paper describes and contrasts the two methods and
offers the opinion that the AOAC method probably gave much higher
results due to formaldehyde off-gassing and, to a lesser extent, other
interferences that would not be operative in the EPA method.

Description of Methods

The AOAC International includes as part of their mission the development
of “fit for purpose” methods.  Many of these methods have been
developed in support of food and cosmetics analyses for use complying
with regulations of the Food and Drug Administration.  It should be
noted that AOAC does not consider themselves a developer of
environmental chemistry methods.  

AOAC Method 931.08 is a colorimetric method developed to analyze for
formaldehyde in food, including milk.  Sample preparation for solids
begins with mixing the sample with water, acidifying with phosphoric
acid and then slowly distilling the sample until 50 mL of distillate
have been collected.  One milliliter of the distillate is mixed with 5
mL of a saturated solution of 1,8-dihydroxynaphtalene-3,6-disulfonic
acid (“chromotropic acid”) in 72% sulfuric acid and heated in a
boiling water batch.  This reagent is also called
4,5-dihydroxy-2,7-naphthalenedisulfonic acid sodium salt.  The presence
of formaldehyde is indicated by the development of a purple color.  The
intensity of the color is proportional to the concentration of
formaldehyde.  The exact nature of the chromaphore is not known.  OSHA
has adapted this method to analyze formaldehyde trapped in sorbent
systems and has postulated a possible reaction mechanism. The method
does not prescribe or even suggest how the color should be measured or
what types of quality control should be included.  

The AOAC method was adapted for use with F019 sludge samples by an
analytical laboratory supporting early F019 sludge delisting petitions. 
The laboratory prepared the sample using the distillation procedure and
measured the intensity of the purple color with a UV-Vis spectrometer.

EPA Method 8315 uses derivatization followed by HPLC separation to
analyze for formaldehyde (and many other aldehydes).  A solid sample is
first leached in an acetate buffer solution to remove the formaldehyde
from the solid.  The leachate is treated with 2,4-dinitrophenylhydrazine
to derivatize the aldehydes, which are then solvent extracted from the
leachate with methylene chloride, solvent exchanged to acetonitrile and
analyzed by HPLC with UV detection.

Evaluation

There are two distinct differences in the methods that probably account
for the large differences seen in the results.  First, and probably less
important, is that the AOAC method is less selective in both the sample
preparation phase and in the detection phase.  Second, and probably more
important, the AOAC method requires that the sample be heated to
approximately 215 oF in order to distill off formaldehyde and probably
causes off-gassing of formaldehyde.

The use of distillation to prepare samples in the AOAC method allows
many organic compounds, particularly those that are chemically close to
formaldehyde, to become part of the distillate and then to potentially
react with the chromotropic acid to either enhance or mask the color
reaction. If positive interferences distill over with the formaldehyde,
then the general colorimetric technique will not be able to distinguish
between these compounds and formaldehyde.  3M Company has documented
that metatrioxane and paraformaldehyde as well as dimethoxymethane
represent positive interferences.  Additionally, it should be noted that
phenol, alcohols, ethylene, propylene, and some aromatic hydrocarbons
have been documented as negative interferences.  Obviously, the presence
of negative interferences would not account for the differences noted in
the F019 delisting analyses.

With EPA Method 8315, the derivatization procedure followed by analysis
by HPLC is much more selective.  Some interferences will still appear,
but using HPLC to separate compounds prior to detection will greatly
reduce the possible compounds that would be detected in the proper
retention time window and be reported as formaldehyde.

It does seem possible that some interferences would be detected as
formaldehyde when using the AOAC method to analyze F019 sludge as
compared to the EPA method.  However, it is estimated that these
interferences would be small compared to the large difference reported
in actual results.  It is known that F019 waste contains paint resins
that have moved through the wastewater treatment systems from the
painting area.  These resins do contain formaldehyde as part of the
polymer system for delivering pigment.  These resins are known to
release formaldehyde when heated as part of the curing process to the
point that curing areas of the assembly plants have air-handling systems
designed to trap formaldehyde that is off-gassing from the resins. 
Curing temperatures routinely used are in the high 200s (oF), but it is
clear that temperatures in the low 200s also cause the resins to release
a significant amount of formaldehyde.  This is probably the most
prominent source of the high formaldehyde results.  When the samples is
distilled, the resins are heated and release significant additional
formaldehyde during the distillation.  This formaldehyde is trapped with
the distillate and is detected.

 Formaldehyde in Workplace Atmospheres, Method ID-205, OSHA Technical
Center, Salt Lake City, UT

 Standard Operating Procedure for Formaldehyde (GC-E-049-REV0), General
Engineering Laboratories, Charleston, SC, November, 1993.

 Determination of Formaldehyde Vapors in Air Using 3M 3721 Formaldehyde
Monitors, 3M Company, Occupational Health and Environmental Safety
Division, May 2002.

