<PAGE>

                                                                   Exhibit 10.38

                    GENERAL RELEASE AND SEPARATION AGREEMENT

         This General Release and Separation Agreement (hereafter "Agreement")
is entered into as of this 10th day of October, 2002, (the "Effective Date")
between Joseph M. Limber (the "Executive"), and ACLARA BioSciences, Inc. (the
"Company"), effective eight days after the Executive's signature (the "Effective
Date"), unless the Executive revokes his acceptance as provided in Paragraph
9(c), below.

         WHEREAS, the Executive was the President and Chief Executive Officer of
the Company, and a Member of the Board of Directors;

         WHEREAS, the Executive tendered his resignation as President and Chief
Executive Officer of the Company, and the Company accepted such resignation
effective as of December 1, 2002 or such earlier date as the Company and the
Executive mutually agree;

         WHEREAS, the Company and the Executive now wish to document the
termination of their employment relationship and fully and finally to resolve
all matters between them;

         THEREFORE, in exchange for the good and valuable consideration set
forth herein, the adequacy of which is specifically acknowledged, the Executive
and the Company hereby agree as follows:

         1. Resignation as President and Chief Executive Officer. The Executive
hereby confirms his resignation of all positions that the Executive held as an
officer of the Company, including his positions as President and Chief Executive
Officer of the Company, and the Company confirms its acceptance of such
resignations, effective December 1, 2002 or such earlier date as the Company and
the Executive mutually agree (the "Resignation Date"). The Executive shall
receive a severance payment of $167,500 to be paid by the Company in a lump sum
on January 15, 2003. Such payment shall be subject to normal withholdings for
payroll taxes and similar amounts.

         2. Board Membership. The Executive agrees that he shall remain a member
of the Board of Directors of the Company (the "Board") following the Resignation
Date and until the date of the Company's annual meeting of stockholders in 2003.
The Executive hereby tenders his resignation as director effective the date of
the Company's annual meeting of stockholders in 2003, or such earlier date as
the Company and the Executive mutually agree.

         3. Continuing Employment; Resignation. For the period commencing on the
Resignation Date and ending on December 31, 2003 (the "Transition Period"), the
Executive shall remain an employee of the Company with the title of Executive
Director (while serving as a member of the Board) and make himself available to
the Company, as the Company may request, for up to five days per month in the
period ending January 31, 2003 and for up to one day per month thereafter, at
such times as the Company and the Executive mutually agree. During the
Transition Period, the Executive shall effect an orderly transition of his
duties to the Company's new Chief Executive Officer or Acting Chief Executive
Officer (the "CEO") and

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<PAGE>

perform such other services as the CEO or the Board may reasonably request. For
his availability and services during the Transition Period, whether or not the
Executive is requested to provide services, the Company shall pay the Executive
at his current annual base salary rate of $335,000 through December 31, 2002 and
at an annual salary rate of $167,500 for the remainder of the Transition Period,
such amounts to be paid in semi-monthly installments in accordance with the
Company's regular payroll practices. All such payments will be subject to normal
withholdings for payroll taxes and similar amounts. The Executive hereby agrees
that his resignation of employment with the Company shall be effective December
31, 2003. Nothwithstanding the foregoing, this Agreement shall not prohibit the
Executive from accepting additional employment during the Transition Period;
provided, however, that during the Transition Period the Executive may not,
without Board approval, accept additional employment with any company that the
Board reasonably determines is a competitor of the Company. Companies which may
be viewed as competitors include, but are not limited to, biotechnology tools
companies or other companies with a potentially adverse intellectually property
interest.

         4. Payment of Accrued Wages and Expenses. On or before December 1,
2002, the Company shall pay to the Executive an amount equal to all accrued
wages owed to him through that date, including accrued vacation through December
1, 2002, less applicable withholding, and all expenses submitted by the
Executive as of December 1, 2002. The Executive agrees to submit requests for
expense reimbursement, in accordance with the Company's expense reimbursement
policies, on or before December 1, 2002.

         5. Bonus. The Executive agrees that he shall not be eligible for a
bonus for the calendar years ending December 31, 2002 and 2003.

         6. Benefits. Except as provided herein, the Executive will not be
eligible for any employer-sponsored benefits after the Transition Period. The
Executive acknowledges and agrees that he will not be entitled to accrue paid
vacation days or paid holidays during the Transition Period. The Executive will
be eligible for healthcare benefits during the Transition Period, after which
standard COBRA benefits will apply.

         7. Stock Options. Pursuant to the Amended and Restated ACLARA
BioSciences, Inc. 1997 Stock Plan (the "Plan"), the Executive has been granted
certain stock options (each an "Option"). Information concerning the number of
shares, the vesting schedule and certain other information with respect to each
Option is set forth on Exhibit A hereto. The Executive hereby acknowledges and
agrees that the information set forth on Exhibit A is complete and accurate as
to each of the Executive's Options. As provided in the Plan, the Executive's
Options shall continue to vest during the term of the Transition Period, so long
as the Executive remains an Employee of the Company (as defined in the Plan).
Concurrently herewith, the Executive is also entering into a Change In Control
Agreement with the Company, attached hereto as Exhibit B. Except as set forth in
this Agreement or in an Exhibit to this Agreement, each Option granted to the
Executive shall be governed by the terms of the applicable option agreement and
the Plan.

         8. Repayment of Loan Made to the Executive. The Executive entered into
certain secured, interest-bearing promissory notes (the "Notes") in favor of the
Company with an aggregate principal amount of $485,149.13 as of October 4, 2002.
The Executive acknowledges that Exhibit C accurately sets forth the outstanding
principal and interest amounts due and owing

                                        2

<PAGE>

as of October 4, 2002 and hereby agrees to repay such amounts to the Company
(plus additional interest accrued as indicated on a daily basis on Exhibit C)
within five days after the Effective Date.

          9.  General Release of Claims by the Executive. In consideration for
receiving the benefits set forth in this Agreement, the Executive agrees to
execute a release in the form attached as Exhibit D upon termination of the
Transition Period.

              (a)  The Executive, on behalf of himself and his executors, heirs,
          administrators, representatives and assigns, hereby agrees to release
          and forever discharge the Company and all predecessors, successors and
          their respective parent corporations, affiliates, related, and/or
          subsidiary entities, and all of their past and present investors,
          directors, shareholders, officers, general or limited partners,
          employees, attorneys, agents and representatives, and employee benefit
          plans in which the Executive is or has been a participant by virtue of
          his employment with the Company, from any and all claims, debts,
          demands, accounts, judgments, rights, causes of action, equitable
          relief, damages, costs, charges, complaints, obligations, promises,
          agreements, controversies, suits, expenses, compensation,
          responsibility and liability of every kind and character whatsoever
          (including attorneys' fees and costs), whether in law or equity, known
          or unknown, asserted or unasserted, suspected or unsuspected
          (collectively, "Claims"), which the Executive has or may have had
          against such entities based on any events or circumstances arising or
          occurring on or prior to the date hereof or on or prior to the
          Resignation Date, arising directly or indirectly out of, relating to,
          or in any other way involving in any manner whatsoever the Executive's
          employment by the Company or the changes in the terms and conditions
          of the Executive's employment as of the Resignation Date, and any and
          all claims arising under federal, state, or local laws relating to
          employment, including without limitation claims of wrongful discharge,
          breach of express or implied contract, fraud, misrepresentation,
          defamation, or liability in tort, claims of any kind that may be
          brought in any court or administrative agency, any claims arising
          under Title VII of the Civil Rights Act of 1964, the Age
          Discrimination in Employment Act, the Americans with Disabilities Act,
          the Older Workers Benefit Protection Act, the Fair Labor Standards
          Act, the Employee Retirement Income Security Act, the Family and
          Medical Leave Act, and similar state or local statutes, ordinances,
          and regulations.

              (b)  THE EXECUTIVE ACKNOWLEDGES THAT HE HAS BEEN ADVISED OF AND IS
          FAMILIAR WITH THE PROVISIONS OF CALIFORNIA CIVIL CODE SECTION 1542,
          WHICH PROVIDES AS FOLLOWS:

              "A GENERAL RELEASE DOES NOT EXTEND TO CLAIMS WHICH THE CREDITOR
              DOES NOT KNOW OR SUSPECT TO EXIST IN HIS FAVOR AT THE TIME OF
              EXECUTING THE RELEASE, WHICH IF KNOWN BY HIM MUST HAVE MATERIALLY
              AFFECTED HIS SETTLEMENT WITH THE DEBTOR."

                                        3

<PAGE>

                BEING AWARE OF SAID CODE SECTION, THE EXECUTIVE HEREBY EXPRESSLY
            WAIVES ANY RIGHTS HE MAY HAVE THEREUNDER, AS WELL AS UNDER ANY OTHER
            STATUTES OR COMMON LAW PRINCIPLES OF SIMILAR EFFECT.

                (c)  In accordance with the Older Workers Benefit Protection Act
            of 1990, the Executive acknowledges that he is aware of the
            following:

                     (i)   He has a right to consult with an attorney before
                           accepting this offer;

                     (ii)  He has 21 days from the date this offer is received
                           to consider this offer; and

                     (iii) He has seven days after accepting this offer to
                           revoke his acceptance, and his acceptance will not be
                           effective until that revocation period has expired.

            10. The Company, on behalf of itself and its respective successors,
agents, attorneys and representatives, hereby agrees to release and forever
discharge the Executive and his executors, heirs, representatives and assigns,
from any and all claims, debts, demands, accounts, judgments, rights, causes of
action, equitable relief, damages, costs, charges, complaints, obligations,
promises, agreements, controversies, suits, expenses, compensation,
responsibility and liability of every kind and character whatsoever (including
attorneys' fees and costs), whether in law or equity, asserted or unasserted
(collectively, "Claims"), which the Company has or may have against the
Executive based on any events or circumstances known to the Company's Board of
Directors or executive officers as of the date of execution of this Agreement by
the Company. Notwithstanding the generality of the foregoing, the Company does
not release the Executive from his obligation to repay certain loans described
in Paragraph 8 of this Agreement or from his continuing obligations to the
Company under the terms of the Company's Employee Confidentiality and Invention
Assignment Agreement.

            11. Nondisparagement. The Executive agrees that neither he nor
anyone acting by, through, under or in concert with him shall disparage or
otherwise communicate negative statements or opinions about the Company, its
Board members, officers, employees or business. The Company agrees that neither
its Board members nor officers shall disparage or otherwise communicate negative
statements or opinions about the Executive.

            12. Cooperation. The Executive agrees to give reasonable
cooperation, at the Company's request, in any pending or future litigation or
arbitration brought against the Company and in any investigation the Company may
conduct. The Executive shall be reimbursed for all time spent, after the
Transition Period, at an hourly rate of $300 per hour. The Company shall
reimburse the Executive for all expenses reasonably incurred by him in
compliance with this Paragraph. Notwithstanding the foregoing, the Company shall
have no obligation to pay the Executive for time spent and expenses incurred by
the Executive in any pending or future litigation or arbitration where the
Executive is an unindemnified co-defendant

                                        4

<PAGE>

or party to the arbitration or litigation.

       13. Confidential Information; Return of Company Property.

           (a) The Executive hereby expressly confirms his continuing
       obligations to the Company pursuant to the Confidential Information and
       Invention Assignment Agreement executed by the Executive on [insert date
       of agreement] (the "Confidentiality Agreement").

           (b) The Executive shall deliver to the Company within 10 (ten)
       business days of the Company's request, all originals and copies of
       correspondence, drawings, manuals, letters, notes, notebooks, reports,
       programs, plans, proposals, financial documents, or any other documents
       concerning the Company's customers, business plans, marketing strategies,
       products, processes or business of any kind and/or which contain
       proprietary information or trade secrets which are in the possession or
       control of the Executive or his agents or representatives.

           (c) The Executive shall return to the Company within 10 (ten)
       business days of the Company's request, all equipment of the Company in
       his possession or control.

       14. Non-Solicitation of Company Employees. For the period commencing on
the Effective Date and ending on December 31, 2004, the Executive shall not,
directly or indirectly, solicit, induce, recruit or encourage any of the
Company's employees or consultants to leave their employment or consulting
relationship with the Company, or take away such employees or consultants, or
attempt to solicit, induce, recruit, encourage or take away employees or
consultants of the Company, either for the benefit of the Executive or for any
other person or entity.

       15. Taxes. To the extent any taxes may be payable by the Executive for
the benefits provided to him by this Agreement beyond those withheld by the
Company, the Executive agrees to pay them himself and to indemnify and hold the
Company and the other entities released herein harmless for any tax claims or
penalties, and associated attorneys' fees and costs, resulting from any failure
by him to make required payments.

       16. In the Event of a Claimed Breach. All controversies, claims and
disputes arising out of or relating to this Agreement, including without
limitation any alleged violation of its terms, shall be resolved by final and
binding arbitration before a single neutral arbitrator in Santa Clara County,
California, in accordance with the Employment Dispute Resolution Rules of the
American Arbitration Association ("AAA"). The arbitration shall be commenced by
filing a demand for arbitration with the AAA within 14 (fourteen) days after the
filing party has given notice of such breach to the other party. The arbitrator
shall award the prevailing party attorneys' fees and expert fees, if any.
Notwithstanding the foregoing, it is acknowledged that it will be impossible to
measure in money the damages that would be suffered if the parties fail to
comply with any of the obligations imposed on them under Section 13(a) hereof,
and that in the event of any such failure, an aggrieved person will be
irreparably damaged and will not have an adequate remedy at law. Any such person
shall, therefore, be entitled to injunctive relief, including specific
performance, to enforce such obligations, and if any action shall be brought in

                                        5

<PAGE>

equity to enforce any of the provisions of Section 13(a) of this Agreement, none
of the parties hereto shall raise the defense that there is an adequate remedy
at law.

         17. Choice of Law. This Agreement shall in all respects be governed and
construed in accordance with the laws of the State of California, including all
matters of construction, validity and performance, without regard to conflicts
of law principles.

         18. Notices. All notices, demands or other communications regarding
this Agreement shall be in writing and shall be sufficiently given if either
personally delivered or sent by facsimile or overnight courier, addressed as
follows:

             (a)      If to the Company:

                      ACLARA BioSciences, Inc.
                      1288 Pear Avenue
                      Mountain View, California 94043
                      Attn:  Chief Financial Officer
                      Phone: (650) 210-1200
                      Facsimile: (650) 210-9271


             (b)      If to the Executive:

                      Joseph M. Limber
                      1515 Arriba Court
                      Los Altos, California 94024

         19. Severability. Except as otherwise specified below, should any
portion of this Agreement be found void or unenforceable for any reason by a
court of competent jurisdiction, the parties intend that such provision be
limited or modified so as to make it enforceable, and if such provision cannot
be modified to be enforceable, the unenforceable portion shall be deemed severed
from the remaining portions of this Agreement, which shall otherwise remain in
full force and effect. If any portion of this Agreement is so found to be void
or unenforceable for any reason in regard to any one or more persons, entities,
or subject matters, such portion shall remain in full force and effect with
respect to all other persons, entities, and subject matters. This paragraph
shall not operate, however, to sever the Executive's obligation to provide the
binding release to all entities intended to be released hereunder.

         20. Understanding and Authority. The parties understand and agree that
all terms of this Agreement are contractual and are not a mere recital, and
represent and warrant that they are competent to covenant and agree as herein
provided.

         21. Integration Clause. This Agreement and the Exhibits hereto contain
the entire agreement of the parties with regard to the changes in terms and
conditions of and separation of the Executive's employment, and supersedes any
prior agreements as to that matter. This Agreement shall not supersede the
Indemnification Agreement between the Executive and the

                                        6

<PAGE>

Company, including limitations on the Company's obligation to indemnify the
Executive, which shall remain in effect. This Agreement may not be changed or
modified, in whole or in part, except by an instrument in writing signed by the
Executive and the Chief Executive Officer or other responsible officer of the
Company.

     21. Execution in Counterparts. This Agreement may be executed in
counterparts with the same force and effectiveness as though executed in a
single document.

     The parties have carefully read this Agreement in its entirety; fully
understand and agree to its terms and provisions; and intend and agree that it
is final and binding on all parties.

     IN WITNESS WHEREOF, and intending to be legally bound, the parties have
executed the foregoing on the dates shown below.

JOSEPH M. LIMBER                                     COMPANY


/s/ Joseph M. Limber                          /s/ Thomas R. Baruch
--------------------------------              ----------------------------------
                                              By:  Thomas R. Baruch


                                              Title:  Chairman

Date October 11, 2002                         Date_____________________________

                                        7

<PAGE>

                                    Exhibit A

                                  Stock Options
                              as of October 4, 2002

<TABLE>
<CAPTION>
------------------------------------------------------------------------------------------------------------------------------------

    Number of Shares     Grant Date     Exercise Price   Shares Vested    Shares Exercised              Vesting Schedule
    ----------------     ----------     --------------   -------------    ----------------              ----------------
------------------------------------------------------------------------------------------------------------------------------------
<S>                     <C>             <C>             <C>            <C>               <C>
         600,000         May 6, 1998         $0.40          600,000           600,000        fully vested
------------------------------------------------------------------------------------------------------------------------------------
         150,000        Mar. 19, 1999         0.40          128,125           150,000      1/4/th/ one year from the vesting
                                                                                           commencement date, followed by 1/48/th/
                                                                                           per month thereafter
------------------------------------------------------------------------------------------------------------------------------------
         232,500        Dec. 1, 1999          0.63          232,500           232,500      fully vested
------------------------------------------------------------------------------------------------------------------------------------
         112,500        Jan. 16, 2000         3.33           75,000               0        1/4/th/ one year from the vesting
                                                                                           commencement date, followed by 1/48/th/
                                                                                           per month thereafter
------------------------------------------------------------------------------------------------------------------------------------
         250,000        Apr. 11, 2001         5.02              0                 0        in three annual increments on April 11,
                                                                                           2004, 2005 and 2006, with acceleration
                                                                                           based on the achievement of certain
                                                                                           prices for the Company's common stock,
                                                                                           as set forth in the stock option
                                                                                           agreement
------------------------------------------------------------------------------------------------------------------------------------
         100,000        Mar. 5, 2002          3.70              0                 0        1/4/th/ one year from the vesting
                                                                                           commencement date, followed by 1/48/th/
                                                                                           per month thereafter
------------------------------------------------------------------------------------------------------------------------------------
</TABLE>

                                        8

<PAGE>

                                    Exhibit B

                           Change in Control Agreement

                                        9

<PAGE>

                                    Exhibit C

                                Promissory Notes
                              as of October 4, 2002
<TABLE>
<CAPTION>
------------------------------------------------------------------------------------------------------------------------------------
    Date of Note      Maturity Date              Interest rate              Principal Amount     Accrued Interest      Total Due
    ------------      -------------              -------------              ----------------     -----------------     ---------
------------------------------------------------------------------------------------------------------------------------------------
<S>                   <C>                 <C>                               <C>                  <C>                   <C>
   Jan. 13, 2000      Apr. 13, 2002       5.8% compounded semiannually          $ 236,540.80          $ 39,979.80      $ 276,520.60
------------------------------------------------------------------------------------------------------------------------------------

   Jan. 13, 2000      Mar. 19, 2003       5.8% compounded semiannually             60,000.00            10,150.64         70,150.64
------------------------------------------------------------------------------------------------------------------------------------

   Jan. 13, 2000      Apr. 13, 2002       5.8% compounded semiannually            147,250.00            24,912.08        172,162.08
------------------------------------------------------------------------------------------------------------------------------------

   Jul. 28, 2000      Apr. 13, 2002         6.6% compounded annually               41,358.33             5,921.72         47,280.05
------------------------------------------------------------------------------------------------------------------------------------
</TABLE>

   Payment after October 4, 2002 will cause interest to accrue at an aggregate
                      total of $88.39 per day for all loans

                                       10

<PAGE>

                                    Exhibit D

                                 GENERAL RELEASE

                  Joseph M. Limber (the "Executive"), on behalf of himself and
his executors, heirs, administrators, representatives and assigns, hereby agrees
to release and forever discharge the Company and all predecessors, successors
and their respective parent corporations, affiliates, related, and/or subsidiary
entities, and all of their past and present investors, directors, shareholders,
officers, general or limited partners, employees, attorneys, agents and
representatives, and employee benefit plans in which the Executive is or has
been a participant by virtue of his employment with the Company, from any and
all claims, debts, demands, accounts, judgments, rights, causes of action,
equitable relief, damages, costs, charges, complaints, obligations, promises,
agreements, controversies, suits, expenses, compensation, responsibility and
liability of every kind and character whatsoever (including attorneys' fees and
costs), whether in law or equity, known or unknown, asserted or unasserted,
suspected or unsuspected (collectively, "Claims"), which the Executive has or
may have had against such entities based on any events or circumstances arising
or occurring on or prior to the date hereof, arising directly or indirectly out
of, relating to, or in any other way involving in any manner whatsoever the
Executive's employment by the Company or the separation thereof, and any and all
claims arising under federal, state, or local laws relating to employment,
including without limitation claims of wrongful discharge, breach of express or
implied contract, fraud, misrepresentation, defamation, or liability in tort,
claims of any kind that may be brought in any court or administrative agency,
any claims arising under Title VII of the Civil Rights Act of 1964, the Age
Discrimination in Employment Act, the Americans with Disabilities Act, the Older
Workers Benefit Protection Act, the Fair Labor Standards Act, the Employee
Retirement Income Security Act, the Family and Medical Leave Act, and similar
state or local statutes, ordinances, and regulations.

                  THE EXECUTIVE ACKNOWLEDGES THAT HE HAS BEEN ADVISED OF AND IS
FAMILIAR WITH THE PROVISIONS OF CALIFORNIA CIVIL CODE SECTION 1542, WHICH
PROVIDES AS FOLLOWS:

                  "A GENERAL RELEASE DOES NOT EXTEND TO CLAIMS WHICH THE
                  CREDITOR DOES NOT KNOW OR SUSPECT TO EXIST IN HIS FAVOR AT THE
                  TIME OF EXECUTING THE RELEASE, WHICH IF KNOWN BY HIM MUST HAVE
                  MATERIALLY AFFECTED HIS SETTLEMENT WITH THE DEBTOR."

                  BEING AWARE OF SAID CODE SECTION, THE EXECUTIVE HEREBY
EXPRESSLY WAIVES ANY RIGHTS HE MAY HAVE THEREUNDER, AS WELL AS UNDER ANY OTHER
STATUTES OR COMMON LAW PRINCIPLES OF SIMILAR EFFECT.

                                       11

<PAGE>

                  In accordance with the Older Workers Benefit Protection Act of
         1990, the Executive acknowledges that he is aware of the following:

                         (i)     He has a right to consult with an attorney
                                 before accepting this offer;

                         (ii)    He has 21 days from the date this offer is
                                 received to consider this offer; and

                         (iii)   He has seven days after accepting this offer
                                 to revoke his acceptance, and his acceptance
                                 will not be effective until that revocation
                                 period has expired.

JOSEPH M. LIMBER                                      Dated:  __________, 2003

                                       12