September 6, 2006	Certified Mail – Return receipt Requested

Mr. Keith Lamb	

Pennsville Township Water Department

2 Sanderlin Road

Pennsville, NJ 08070

RE: 	Pennsville Township Water Department

	Water Supply Well and Distribution Sampling Results

Dear Mr. Lamb:

As you requested, this letter documents our August 22, 2006 phone
conversation:

DuPont has been using Exygen Research for PFOA analyses since October
2001.

The LC/MS/MS Laboratory Spike Recovery data provided on pages 8 through
18 of Attachment B of Exygen Research Laboratory Report No. L0008561
(transmitted to Mr. Jack Lynch by my July 21, 2006 letter) is derived
as follows:

Each sample was analyzed.

A portion of each analyzed sample received a 50 ng/L (part per trillion)
spike of PFOA.

The resulting blend was analyzed and the results reports under the
heading “Matrix Spike Result”.

The Matrix Spike Recovery in percent is calculated from:

		Matrix Spike Recovery, %  =  	Matrix Spike Result  x  100

							(Sample Conc + Spiked Amount)

The analytical technique was deemed to be satisfactory if the calculated
Matrix Spike Recovery was between 70% and 130%, as was the case for all
11 samples.

3. The analytical method differences between Axys and Exygen Research
are:

	Axys	Exygen

a.	Sample Volume, mL	500	40

b. 	Volume Concentration	125:1	8:1

c. 	Solid Phase Extraction on 	mixed bed	C18 resin

d.	 Solid Phase Extraction Cleanup	none	40% methanol solution

e. 	Analytical Column	75 mm C18	50 mm C18



In addition, the labs use different internal standards for quantifying
results.  Axys routinely analyzes for a longer list of compounds whereas
the method used by Exygen is validated for PFOA in water.

Very truly yours,

Cynthia N. McManus

Environmental Manager

cc:	M. Aucoin

	M. Kaiser

	A. Masse

	J. Strait

Mr. Keith Lamb

Pennsville Township Water Department

September 6, 2006

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