Document:

<PAGE>   1
                                                                    Exhibit 10.6

         The following Executive Officers are parties to an Employment Agreement
in the form of Exhibit 10.5, which Employment Agreements differ with respect to
the terms indicated:

<TABLE>
<CAPTION>
             EXECUTIVE OFFICER                                  POSITION                             SALARY
             -----------------                                  --------                             ------
<S>                                           <C>                                                   <C>

Frank H. Jellinek, Jr.                        President and Chief Executive Officer                 $750,000
Jeffrey C. Leathe                             Chief Financial Officer                               $315,000
Michael K. Bresson                            General Counsel                                       $310,000
Yuh-Geng Tsay                                 Group President, Immunoassay Diagnostics              $310,000
Verner Andersen                               Group President, Labware and Life Sciences            $305,000

</TABLE><PAGE>   1

                                                                   Exhibit 10.23

                       FIRST AMENDMENT TO LEASE AGREEMENT

                  THIS FIRST AMENDMENT TO LEASE ("Amendment") is made and
executed as of December 11, 2000 by and among CORPORATE PROPERTY ASSOCIATES - 7
A CALIFORNIA LIMITED PARTNERSHIP, a California limited partnership and CORPORATE
PROPERTY ASSOCIATES 8, L.P., A DELAWARE LIMITED PARTNERSHIP, a Delaware limited
partnership (collectively, the "Landlord"), both with an address c/o W. P. Carey
& Co. LLC, 50 Rockefeller Plaza, 2nd Floor, New York, New York 10022 and
BARNSTEAD THERMOLYNE CORPORATION, a Delaware corporation ("Tenant"), with an
address c/o Sybron International Corporation, d/b/a Apogent Technologies, 10
Pleasant Street, Suite 300, Portsmouth, New Hampshire 03801.

                                  WITNESSETH:

                  WHEREAS, pursuant to the terms of a certain Lease made as of
December 21, 1988 ("Lease"), Landlord leased to Tenant and Tenant leased from
Landlord certain property situate in Dubuque, Iowa (the "Leased Premises"); and

                  WHEREAS, the parties wish to amend and modify the terms of the
Lease as set forth herein.

                  NOW, THEREFORE, incorporating the recitals hereinabove set
forth by reference and intending to be legally bound hereby, and in
consideration of the mutual covenants contained herein and other good and
valuable consideration, the receipt whereof is hereby acknowledged, the parties
hereto covenant and agree as follows:

                1. Capitalized Terms.  Any capitalized terms used herein and not
otherwise defined herein shall have the respective meanings assigned thereto in
the Lease.

                2. Paragraph 2 - Financial Covenants.  The definition "Financial
Covenants" after the definition "Fair Market Value" contained in Paragraph 2 is
hereby deleted in its entirety.

                3. Paragraph 2 - "Guarantor". The party "Sybron Acquisition
  Company" contained in the definition of "Guarantor" in Paragraph 2 is hereby
  deleted and in lieu thereof, substituted with the party "Sybron International
  Corporation". Any references in the Lease to "Sybron Acquisition Company" are
  hereby deleted and in lieu thereof, substituted with "Sybron International
  Corporation".

                4. Paragraph 2 - "Guaranty".  The definition "Guaranty"
contained in Paragraph 2 is hereby deleted in its entirety and in lieu thereof,
substituted with the following:
<PAGE>   2

                   ""Guaranty" shall mean the Amended and Restated Guaranty
                   and Suretyship Agreement dated as of December 11, 2000 from
                   Guarantor to Landlord."

                5. Paragraph 2 - "Loan".  The definition "Loan" in Paragraph 2
is hereby deleted and in lieu thereof, substituted with the following:

                  ""Loan" shall mean any loan made by one or more Lenders to
                  Landlord, which loan is secured by a Mortgage and an
                  Assignment and evidenced by a Note, the principal of which
                  shall not exceed eighty (80%) percent of the then estimated
                  fair market value of the Leased Premises and all of the
                  premises leased by Landlord under the Other Leases, as
                  determined by a qualified real estate appraiser selected and
                  relied upon in good faith by Lender."

                6. Paragraph 2 - "Other Leases".  The definition "Other Leases"
is hereby deleted in its entirety and in lieu thereof, substituted with the
following:

                  ""Other Leases" shall mean (i) the Lease Agreement dated as of
                  the date hereof between Landlord, as lessor, and Nalge
                  Company, as lessee, with respect to certain premises located
                  in Penfield, New York, and (ii) the Lease Agreement dated as
                  of the date hereof between Landlord, as lessor, and Erie
                  Scientific Company, as lessee, with respect to certain
                  premises located in Portsmouth, New Hampshire, as may be
                  amended or modified from time to time."

                7. Paragraph 21 - Notices. The designations for notice for
Landlord and Reed Smith Shaw & McClay LLP contained in Paragraph 21 are hereby
deleted in their entirety and in lieu thereof, substituted with the following:

                  "if to Landlord, to:      Corporate Property Associates 7 -
                                            A California Limited Partnership and
                                            Corporate Property Associates 8,
                                            L.P.- A Delaware Limited Partnership
                                            c/o W. P. Carey & Co., LLC
                                            50 Rockefeller Plaza, 2nd Floor
                                            New York, New York  10020

                  With a copy to:           ReedSmith LLP
                                            2500 One Liberty Place
                                            Philadelphia, PA  19103
                                            Attn: Chairman, Real Estate
                                            Department"

The designations for notice for Tenant and Guarantor contained in Paragraph 21
are hereby deleted in their entirety and in lieu thereof, substituted with the
following:

                                       2
<PAGE>   3
                  "and if to Tenant, to:    Barnstead Thermolyne Corporation
                                            c/o Sybron International Corporation
                                            d/b/a Apogent Technologies
                                            10 Pleasant Street, Suite 300
                                            Portsmouth, New Hampshire  03801
                                            Attn:  Secretary"

                  "and if to Guarantor, to: Sybron International Corporation
                                            d/b/a Apogent Technologies
                                            10 Pleasant Street, Suite 300
                                            Portsmouth, New Hampshire  03801
                                            Attn:  Secretary"

                8. Paragraph 27 - Determination of Value. The word "or" after
the punctuation mark "," and before the parenthetical "(C)" contained in the
thirteenth (13th) line of Subparagraph 27(a)(i) of the Lease is hereby deleted.
The following phrase is hereby inserted after the word "hereof" and before the
punctuation mark "," contained in the seventeenth (17th) line of Subparagraph
27(a)(i):

                  "or (D) Tenant provides Landlord with notice of Tenant's
intention to purchase the Leased Premises pursuant to Paragraph 32"

                9. Paragraph 28 - Option to Purchase.  Paragraph 28(a) is hereby
deleted in its entirety and in lieu thereof, substituted with the following:

                  "(a) Landlord does hereby give and grant to Tenant the option
                  to purchase the entire Leased Premises on any date (the
                  "Option Purchase Date") between June 1, 2008 and May 31, 2009
                  selected by Tenant upon not less than sixty (60) days prior
                  written notice to Landlord and upon payment of the Purchase
                  Price (as defined in the last paragraph of this Paragraph
                  28(a)). Tenant must exercise its option to purchase the Leased
                  Premises by giving Landlord written notice of Tenant's
                  intention to purchase the Leased Premises no later than one
                  hundred eighty (180) days prior to December 1, 2007."

               10. Paragraph 31 - Subordination.  The first full sentence of
Paragraph 31 is hereby deleted in its entirety and in lieu thereof, substituted
with the following:

                  "At Landlord's election, this Lease shall become and
                  thereafter remain subject and subordinate to any and all
                  mortgages, charges or deeds of trust affecting the Leased
                  Premises which may be executed and placed on public record on
                  or after the date of this Lease, or any renewals,
                  modifications, consolidations, supplements, replacements or
                  extensions thereof, for the full amount of all advances made
                  or to be made thereunder and without regard to the time or
                  character of such advances, so long as the Lender holding the
                  security instrument to which this Lease is to be

                                       3
<PAGE>   4
                  subordinated agrees that it will recognize Tenant's rights
                  under this Lease and not disturb its quiet possession of the
                  Leased Premises as long as no Event of Default has occurred
                  and is continuing hereunder, and provided that any such
                  mortgage, charge or deed of trust shall with respect to the
                  Leased Premises and all of the premises leased by Landlord
                  under the Other Leases secure an original principal amount no
                  greater than eighty (80%) percent of the then estimated fair
                  market value of the Leased Premises and all of the premises
                  leased by Landlord under the Other Leases, as determined by a
                  qualified real estate appraiser selected and relied upon in
                  good faith by the Lender."

               11. Paragraph 32 - Financial Covenants.  Paragraph 32 of the
Lease is hereby deleted in its entirety and in lieu thereof, substituted with
the following:

                  "32. Change in Control Credit Event. Tenant hereby
                  acknowledges (1) that for itself and for any assignee of this
                  Lease including a Tenant Affiliate but excluding any other
                  assignee who complies with the requirements of clause (b) of
                  the second full paragraph of Paragraph 17, it hereby consents
                  to and agrees to be bound by the obligations of Guarantor
                  under Section 6 of the Guaranty to cause Tenant to make a
                  rejectable offer to purchase the Leased Premises in the event
                  of a Change in Control Credit Event (as defined under the
                  Guaranty), and (2) that if Landlord accepts such rejectable
                  offer, Tenant will pay to Landlord an amount ("Covenant Offer
                  Amount") equal to the Fair Market Value as determined in
                  accordance with Paragraph 27 of this Lease and will acquire
                  the Leased Premises in accordance with Paragraph 16 of this
                  Lease. Terms not otherwise defined in the Lease are as defined
                  in the Guaranty."

               12. Paragraph 33 - Restriction on Landlord Debt.  Paragraph 33 is
hereby deleted in its entirety.

               13. Full Force and Effect.  Except as expressly set forth herein,
nothing herein is intended to or shall be deemed to modify or amend any of the
other terms or provisions of the Lease.  Except as specifically amended herein,
the terms and conditions of the Lease shall remain in full force and effect.

               14. Counterparts.  This Amendment may be executed in any number
of and by different parties hereto on separate counterparts, all of which, when
so executed, shall be deemed an original, but all such counterparts shall
constitute one and the same agreement.

               15. Entire Understanding. This Amendment and the Lease
together contain the entire understanding between the parties hereto and
supersedes all prior agreements and understandings, if any, relating to the
subject matter hereof or thereof. Any promises, representations, warranties or
guarantees not herein or therein contained and hereinafter made shall have no
force and effect unless in writing, and executed by the party or parties making
such representations, warranties or guarantees. Neither this Amendment nor the
Lease nor any portion or provisions hereof or thereof may be changed, modified,
amended, waived,

                                       4
<PAGE>   5
supplemented, discharged, cancelled or terminated orally or by any course of
dealing, or in any manner other than by an agreement in writing, signed by the
party to be charged.

                                       5
<PAGE>   6

                  IN WITNESS WHEREOF, the Parties hereto intending to be legally
bound and to so bind their respective representatives, successors and assigns,
set their hands and seals the day and year first above written.

                                       LANDLORD:

                                       CORPORATE PROPERTY ASSOCIATES 7, L.P. -
                                       A CALIFORNIA LIMITED PARTNERSHIP,
                                       a California limited partnership

                                       By:  W.P. CAREY & CO., LLC,
                                            Managing General Partner

                                            By: /s/ GORDON F. DUGAN
                                               --------------------------------
                                            Name:
                                            Title:

                                       CORPORATE PROPERTY ASSOCIATES 8 -
                                       A DELAWARE LIMITED PARTNERSHIP,
                                       a Delaware limited partnership

                                       By:  W.P. CAREY & CO., LLC,
                                            Managing General Partner ___________

                                            By: /s/ GORDON F. DUGAN
                                               --------------------------------
                                            Name:
                                            Title:

                                       TENANT:

                                       BARNSTEAD THERMOLYNE CORPORATION,
                                       a Delaware corporation

                                            By: DENNIS BROWN
                                               --------------------------------
                                            Name: Dennis Brown
                                            Title: Assistant Treasurer

                                       6

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00018-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00018-of-00352.parquet"}]]