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                          COMMITTED LINE OF CREDIT NOTE
                          -----------------------------

$5,000,000                                                           May 5, 2000

      FOR VALUE RECEIVED, STRATEGIC DIAGNOSTICS INC., a Delaware corporation
(the "Borrower"), with an address at 111 Pencader Drive, Newark, Delaware 19702,
promises to pay to the order of PNC BANK, DELAWARE (the "Bank"), in lawful money
of the United States of America in immediately available funds at its offices
located at 222 Delaware Avenue, Wilmington, Delaware 19801, or at such other
location as the Bank may designate from time to time, the principal sum of FIVE
MILLION AND 00/100 DOLLARS ($5,000,000) (the "Facility") or such lesser amount
as may be advanced to or for the benefit of the Borrower hereunder, together
with interest accruing on the outstanding principal balance from the date
hereof, as provided below:

      1. Rate of Interest. Amounts outstanding under this Note will bear
interest at a rate per annum which is at all times equals the (a) Prime Rate
plus (b) the Applicable Margin for the Line of Credit (as defined in the Loan
Agreement (hereinafter defined)) minus (c) an amount equal to the Prime Rate
minus the Index on the date of the termination of the Working Cash Line of
Credit, Investment Sweep Rider between the Borrower and the Bank dated of even
date herewith, as the term Index is defined therein. Interest will be calculated
on the basis of a year of 360 days for the actual number of days in each
interest period. As used herein, "Prime Rate" shall mean the rate publicly
announced by the Bank from time to time as its prime rate. The Prime Rate is not
tied to any external rate or index and does not necessarily reflect the lowest
rate of interest actually charged by the Bank to any particular class or
category of customers. If and when the Prime Rate changes, the rate of interest
on this Note will change automatically without notice to the Borrower, effective
on the date of any such change. In no event will the rate of interest hereunder
exceed the maximum rate allowed by law.

      2. Advances. The Borrower may borrow, repay and reborrow hereunder until
the Expiration Date, subject to the terms and conditions of this Note and the
Loan Documents (as defined herein). The "Expiration Date" shall mean May 4,
2001, or such later date as may be designated by the Bank by written notice from
the Bank to the Borrower. The Borrower acknowledges and agrees that in no event
will the Bank be under any obligation to extend or renew the Facility or this
Note beyond the initial Expiration Date. In no event shall the aggregate unpaid
principal amount of advances under this Note exceed the face amount of this
Note.

      3. Advance Procedures. A request for advance made by telephone must be
promptly confirmed in writing by such method as the Bank may require. The
Borrower authorizes the Bank to accept telephonic requests for advances, and the
Bank shall be entitled to rely upon the authority of any person providing such
instructions. The Borrower hereby indemnifies and holds the Bank harmless from
and against any and all damages, losses, liabilities, costs and expenses
(including reasonable attorneys' fees and expenses) which may arise or be
created by the acceptance of such telephone requests or making such advances,
except to the extent attributable to the gross negligence or wilful misconduct
of Bank. The Bank will enter on its books and records, which entry when made
will be presumed correct, the date and amount of each advance, as well as the
date and amount of each payment made by the Borrower.



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      4. Payment Terms. Accrued interest will be due and payable monthly in
arrears on the last day of each month, beginning with the payment due on May 31,
2000. The outstanding principal balance and any accrued but unpaid interest
shall be due and payable on the Expiration Date.

If any payment under this Note shall become due on a Saturday, Sunday or public
holiday under the laws of the State where the Bank's office indicated above is
located, such payment shall be made on the next succeeding business day and such
extension of time shall be included in computing interest in connection with
such payment. The Borrower hereby authorizes the Bank to charge the Borrower's
deposit account at the Bank for any payment when due hereunder. Payments
received will be applied to charges, fees and expenses (including reasonable
attorneys' fees), accrued interest and principal in any order the Bank may
choose, in its sole discretion.

      5. Late Payments; Default Rate. If the Borrower fails to make any payment
of principal, interest or other amount coming due pursuant to the provisions of
this Note within 15 calendar days of the date due and payable, the Borrower also
shall pay to the Bank a late charge equal to the lesser of five percent (5%) of
the amount of such payment or $100 (the "Late Charge"). Such 15 day period shall
not be construed in any way to extend the due date of any such payment. The late
charge is imposed for the purpose of defraying the Bank's expenses incident to
the handling of delinquent payments and is in addition to, and not in lieu of,
the exercise by the Bank of any rights and remedies hereunder, under the other
Loan Documents or under applicable laws, and any fees and expenses of any agents
or attorneys which the Bank may employ. Upon maturity, whether by acceleration,
demand or otherwise, and at the option of the Bank upon the occurrence of any
Event of Default (as hereinafter defined) and during the continuance thereof,
this Note shall bear interest at a rate per annum (based on a year of 360 days
and actual days elapsed) which shall be two percentage points (2.0%) in excess
of the interest rate in effect from time to time under this Note but not more
than the maximum rate allowed by law (the "Default Rate"). The Default Rate
shall continue to apply whether or not judgment shall be entered on this Note.
Both the Late Charge and the Default Rate are imposed as liquidated damages for
the purpose of defraying the Bank's expenses incident to the handling of
delinquent payments, but are in addition to, and not in lieu of, the Bank's
exercise of any rights and remedies hereunder, under the other Loan Documents or
under applicable law, and any fees and expenses of any agents or attorneys which
the Bank may employ. In addition, the Default Rate reflects the increased credit
risk to the Bank of carrying a loan that is in default. The Borrower agrees that
the Late Charge and Default Rate are reasonable forecasts of just compensation
for anticipated and actual harm incurred by the Bank, and that the actual harm
incurred by the Bank cannot be estimated with certainty and without difficulty.

      6. Prepayment. The indebtedness evidenced by this Note may be prepaid in
whole or in part at any time without penalty.

      7. Other Loan Documents. This Note is issued in connection with a loan
agreement between the Borrower and the Bank dated as of the date hereof, and the
other agreements and documents executed in connection therewith or referred to
therein, the terms of which are incorporated herein by reference (as amended
from time to time, collectively the "Loan Documents"), and is secured by the
property described in the Loan Documents and by such other collateral as
previously may have been or may in the future be granted to the Bank to secure
this Note.



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      8. Events of Default. The occurrence of any of the following events will
be deemed to be an "Event of Default" under this Note: (i) the nonpayment of any
principal, interest or other indebtedness under this Note when due; (ii) the
occurrence of any event of default or default and the lapse of any notice or
cure period under any Loan Document or any other debt, liability or obligation
to the Bank of any Obligor; (iii) the filing by or against any Obligor of any
proceeding in bankruptcy, receivership, insolvency, reorganization, liquidation,
conservatorship or similar proceeding (and, in the case of any such proceeding
instituted against any Obligor, such proceeding is not dismissed or stayed
within 90 days of the commencement thereof, provided that the Bank shall not be
obligated to advance additional funds during such period); (iv) any assignment
by any Obligor for the benefit of creditors, or any levy, garnishment,
attachment or similar proceeding is instituted against any property of any
Obligor held by or deposited with the Bank; (v) a default with respect to any
other indebtedness of any Obligor for borrowed money, if the effect of such
default is to cause or permit the acceleration of such debt and such
acceleration would have a material adverse effect upon Borrower's business,
operations, property (including, the Collateral) or prospects; (vi) the
commencement of any foreclosure or forfeiture proceeding, execution or
attachment against any collateral securing the obligations of any Obligor to the
Bank; (vii) the entry of a final judgment against any Obligor and the failure of
such Obligor to discharge or bond the judgment within thirty (30) days of the
entry thereof; (viii) any material adverse change in any Obligor's business,
assets, operations, financial condition or results of operations; (ix) any
Obligor ceases doing business as a going concern; (x) the revocation or
attempted revocation, in whole or in part, of any guarantee by any Guarantor;
(xi) the death or legal incompetency of any individual Obligor or, if any
Obligor is a partnership, the death or legal incompetency of any individual
general partner; or (xii) any representation or warranty made by any Obligor to
the Bank in any Loan Document, or any other documents now or in the future
evidencing or securing the obligations of any Obligor to the Bank, is false,
erroneous or misleading in any material respect; or (xiii) any Obligor's failure
to observe or perform any covenant or other agreement with the Bank contained in
any Loan Document or any other documents now or in the future evidencing or
securing the obligations of any Obligor to the Bank. As used herein, the term
"Obligor" means any Borrower and any Guarantor, and the term "Guarantor" means
any guarantor of the Borrower's obligations to the Bank existing on the date of
this Note or arising in the future.

      Upon the occurrence and during the continuance of an Event of Default: (a)
the Bank shall be under no further obligation to make advances hereunder; (b) if
an Event of Default specified in clause (iii) or (iv) above shall occur, the
outstanding principal balance and accrued interest hereunder together with any
additional amounts payable hereunder shall be immediately due and payable
without demand or notice of any kind; (c) if any other Event of Default shall
occur, the outstanding principal balance and accrued interest hereunder together
with any additional amounts payable hereunder, at the Bank's option and without
demand or notice of any kind, may be accelerated and become immediately due and
payable; (d) at the Bank's option, this Note will bear interest at the Default
Rate from the date of the occurrence of the Event of Default; and (e) the Bank
may exercise from time to time any of the rights and remedies available under
the Loan Documents or under applicable law.

         9. Right of Setoff. In addition to all liens upon and rights of setoff
against the Borrower's money, securities or other property given to the Bank by
law, the Bank shall have, with respect to the Borrower's obligations to the Bank
under this Note and to the extent permitted by law, a contractual possessory
security interest in and a contractual right of setoff against, and the Borrower
hereby assigns, conveys, delivers, pledges and transfers to the Bank all of the
Borrower's right, title and interest in and to, all of the Borrower's deposits,


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moneys, securities and other property now or hereafter in the possession of or
on deposit with, or in transit to, the Bank or any other direct or indirect
subsidiary of PNC Bank Corp., whether held in a general or special account or
deposit, whether held jointly with someone else, or whether held for safekeeping
or otherwise, excluding, however, all IRA, Keogh, and trust accounts. Every such
security interest and right of setoff may be exercised without demand upon or
notice to the Borrower. Every such right of setoff shall be deemed to have been
exercised immediately upon the occurrence of an Event of Default hereunder
without any action of the Bank, although the Bank may enter such setoff on its
books and records at a later time.

         10. Power to Confess Judgment. The Borrower hereby empowers any
attorney of any court of record, during the existence of any Event of Default
hereunder, to appear for the Borrower and, with or without complaint filed,
confess judgment, or a series of judgments, against the Borrower in favor of the
Bank or any holder hereof for the entire principal balance of this Note, all
accrued interest and all other amounts due hereunder, together with costs of
suit and an attorney's commission of the greater of 10% of such principal and
interest or $1,000 added as a reasonable attorney's fee, and for doing so, this
Note or a copy verified by affidavit shall be a sufficient warrant. The Borrower
hereby forever waives and releases all errors in said proceedings and all rights
of appeal and all relief from any and all appraisement, stay or exemption laws
of any state now in force or hereafter enacted. Interest on any such judgment
shall accrue at the Default Rate.

         No single exercise of the foregoing power to confess judgment, or a
series of judgments, shall be deemed to exhaust the power, whether or not any
such exercise shall be held by any court to be invalid, voidable, or void, but
the power shall continue undiminished and it may be exercised from time to time
as often as the Bank shall elect until such time as the Bank shall have received
payment in full of the debt, interest and costs. Notwithstanding the attorney's
commission provided for in the preceding paragraph (which is included in the
warrant for purposes of establishing a sum certain), the amount of attorneys'
fees that the Bank may recover from the Borrower shall not exceed the actual
attorneys' fees incurred by the Bank.

         11. Miscellaneous. All notices, demands, requests, consents, approvals
and other communications required or permitted hereunder must be in writing
(except as may be agreed otherwise above with respect to borrowing requests) and
will be effective upon receipt. Such notices and other communications may be
hand-delivered, sent by facsimile transmission with confirmation of delivery and
a copy sent by first-class mail, or sent by nationally recognized overnight
courier service, to the addresses for the Bank and the Borrower set forth above
or to such other address as either may give to the other in writing for such
purpose. No delay or omission on the Bank's part to exercise any right or power
arising hereunder will impair any such right or power or be considered a waiver
of any such right or power, nor will the Bank's action or inaction impair any
such right or power. No modification, amendment or waiver of any provision of
this Note nor consent to any departure by the Borrower therefrom will be
effective unless made in a writing signed by the Bank. The Borrower agrees to
pay promptly after demand, to the extent permitted by law, all costs and
expenses incurred by the Bank in the enforcement of its rights in this Note and
in any security therefor, including without limitation reasonable fees and
expenses of the Bank's counsel. If any provision of this Note is found to be
invalid by a court, all the other provisions of this Note will remain in full
force and effect. The Borrower and all other makers and indorsers of this Note
hereby forever waive presentment, protest, notice of dishonor and notice of
non-payment. The Borrower also waives all defenses based on suretyship or


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impairment of collateral. If this Note is executed by more than one Borrower,
the obligations of such persons or entities hereunder will be joint and several.
This Note shall bind the Borrower and its successors and assigns, and the
benefits hereof shall inure to the benefit of the Bank and its successors and
assigns; provided, however, that the Borrower may not assign this Note in whole
or in part without the Bank's written consent and the Bank at any time may
assign this Note in whole or in part.

         This Note has been delivered to and accepted by the Bank and will be
deemed to be made in the State where the Bank's office indicated above is
located. THIS NOTE WILL BE INTERPRETED AND THE RIGHTS AND LIABILITIES OF THE
BANK AND THE BORROWER DETERMINED IN ACCORDANCE WITH THE LAWS OF THE STATE WHERE
THE BANK'S OFFICE INDICATED ABOVE IS LOCATED, EXCLUDING ITS CONFLICT OF LAWS
RULES. The Borrower hereby irrevocably consents to the exclusive jurisdiction of
any state or federal court in the county or judicial district where the Bank's
office indicated above is located; provided that nothing contained in this Note
will prevent the Bank from bringing any action, enforcing any award or judgment
or exercising any rights against the Borrower individually, against any security
or against any property of the Borrower within any other county, state or other
foreign or domestic jurisdiction. The Borrower acknowledges and agrees that the
venue provided above is the most convenient forum for both the Bank and the
Borrower. The Borrower waives any objection to venue and any objection based on
a more convenient forum in any action instituted under this Note.

         12. WAIVER OF JURY TRIAL. THE BORROWER IRREVOCABLY WAIVES ANY AND ALL
RIGHTS THE BORROWER MAY HAVE TO A TRIAL BY JURY IN ANY ACTION, PROCEEDING OR
CLAIM OF ANY NATURE RELATING TO THIS NOTE, ANY DOCUMENTS EXECUTED IN CONNECTION
WITH


                           SIGNATURE ON FOLLOWING PAGE


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THIS NOTE OR ANY TRANSACTION CONTEMPLATED IN ANY OF SUCH DOCUMENTS. THE BORROWER
ACKNOWLEDGES THAT THE FOREGOING WAIVER IS KNOWING AND VOLUNTARY.

         The Borrower acknowledges that it has read and understood all the
provisions of this Note, including the confession of judgment and waiver of jury
trial, and has been advised by counsel as necessary or appropriate.

         WITNESS the due execution hereof as a document under seal, as of the
date first written above, with the intent to be legally bound hereby.

                                         STRATEGIC DIAGNOSTICS INC.



                                      By: /s/ Arthur Koch                 (SEAL)
                                          --------------------------------
                                          Print Name: Arthur Koch
                                          Title: COO


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