Document:

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                                                                  EXHIBIT 10.6.1

                                September 9, 1999

Serologicals Corporation
780 Park North Boulevard, Suite 110
Clarkston, Georgia 30021
Attention: Board of Directors

To the Board of Directors:

         Effective as of the date hereof, I am hereby resigning all positions as
officer and/or director which I hold with Serologicals Corporation (the
"Company") and all subsidiaries of the Company. By executing below, we mutually
agree that the Company shall (a) reimburse me for up to $10,000 for
out-placement expenses incurred by me in connection with an employment search
and (b) compensate me and provide me benefits as if I were terminated by the
Company pursuant to Section 6(d)(2) of the Employment Agreement by and between
the Company and me, dated as of March 8, 1993, and as amended on December 28,
1994 (the "Employment Agreement"). We mutually acknowledge and agree that the
terms of the following written agreements by and between the Company and me
remain in effect: (i) the Employment Agreement (except that the words "after the
termination of this Agreement" in the first paragraph of Section 8 of the
Employment Agreement shall be interpreted to mean "after the termination of his
Employment"), (ii) the Indemnification Agreement, dated as of May 9, 1995, by
and between the Company and me, and (iii) the stock option agreements by and
between the Company and me (and for the purposes of each such stock option
agreement this resignation shall be considered a termination without cause).

         Upon your signature and return of this Letter Agreement, this Letter
Agreement will be effective, enforceable and irrevocable.

                                   Sincerely,

                                   /s/ Harold J. Tenoso
                                   ---------------------------------
                                   Harold J. Tenoso

Agreed to and Accepted
as of the date hereof:

By: /s/ Lawrence E. Tilton
    ------------------------
Name:   Lawrence E. Tilton
Title:  Director

By: /s/ Matthew C. Weisman
    ------------------------
Name:   Matthew C. Weisman
Title:  Director

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         The Company, at its sole discretion, may elect to pay to the Employee,
         in lieu of the periodic installments, a single lump-sum payment that is
         equal to the aggregate amount of the severance pay to which the
         Employee is entitled. If made in a lump-sum form, such single payment
         shall be made within thirty (30) days after the Termination Date. The
         date on which the Company makes the final installment payment, or the
         single lump-sum payment, as applicable, to the Employee shall be
         referred to below as the "Completion Date." Regardless of the manner in
         which the Company elects to make these payments (i.e., installment or
         single lump-sum), for purposes of Sections 2(c), 3(b) and 3(c), the
         Completion Date will remain the last day on which the final installment
         of the periodic payment would have been made. If the Employee dies
         before the Completion Date, any unpaid installments, or such lump-sum
         payment, as applicable, shall be paid to the Employee's estate at the
         same time and in the same amounts as such installments or payment would
         have been paid to the Employee if he or she had survived.

         (b)      401(k) Plan. Upon the Termination Date, the Employee will
         receive any automatic vesting of matching contributions that the 401(k)
         Plan in effect as of the Termination Date provides for.

         (c)      Welfare Benefits. Between the Termination Date and the
         Completion Date, the Employee shall continue to receive health, life,
         accidental death and dismemberment insurance, and disability coverage
         under any benefit plan or arrangement of the Company that the Employee
         was receiving immediately prior to the Termination Date. It is
         provided, however, that the Employee's coverage under any such plan or
         arrangement shall continue only to the extent that the Employee
         promptly pay through elective premium deductions from his/her severance
         payments, his/her share of the cost of such coverage that he or she
         would have so paid if he or she had still been employed by the Company.
         Upon the Completion Date, the Employee will be eligible to continue
         group health insurance coverage under COBRA for a period of eighteen
         (18) months, or up to the maximum period of time permitted by law.

         (d)      Stock Options. Upon the Termination Date, vesting of any
         unvested stock options will cease effective on the Termination Date.
         Employee may exercise any vested stock options previously granted to
         him by the Company under the terms and conditions outlined in the
         applicable Stock Option Agreement(s).

         (e)      Bonus. The Employee will remain eligible to participate in the
         Company's special executive bonus plan, provided the Employee remains
         through the date in which the Company releases him from employment (the
         "Completion Date").

3.       Conditions. Notwithstanding the above, the Company's obligation to
provide the benefits described in Section 2 are conditioned upon, and subject
to, the requirements set

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forth in subsections (a), (b) and (c) below. If the Employee fails to comply
with any of these requirements, the Company shall cease to provide such
benefits.

         (a)      Confidential Information and Conduct. During the term of this
         Agreement or at any time thereafter, the Employee shall not (i) divulge
         or disclose to any third party any confidential, non-public,
         proprietary information or any trade secret of, or pertaining to, the
         Company or any of its affiliates, or (ii) knowingly act or conduct
         himself or herself in any manner which is detrimental to the Company or
         any of its affiliates.

         (b)      No Competition. The Employee may not, for a period beginning
         on the Termination Date and ending twenty-four (24) months thereafter,
         become employed with, or an owner of any interest in, any business
         which is a competitor of the Company or Serologicals, as detailed in
         Paragraph 12 of the Amended and Restated Shareholders Agreement, dated
         August 31, 1993.

         (c)      Job Performance and Continued Assistance. Between the date of
         this Agreement and the Termination Date, the Employee shall perform his
         or her duties in good faith, and using his or her best efforts, and in
         the manner expected of an individual who is employed in the same
         capacity with the Company as the Employee. During the period beginning
         on the Termination Date and extending for a period of six (6) months
         thereafter, the Employee shall make himself or herself reasonably
         available by telephone, or in person, during regular business hours,
         for up to four (4) hours per week to provide the Company with advice,
         of a type and quality that would be expected from an individual
         employed in the same capacity with the Company that Employee had
         immediately prior to the Termination Date.

         (d)      Return of Signed Agreement. The Employee must return a signed
         copy of this Agreement to the Director, Human Resources no later than
         ten (10) days from the date of receipt of this Agreement.

4.       Waiver. By accepting and retaining any of the benefits provided under
this Agreement, the Employee waives any employment-related claims he may have
against the Company or Serologicals.

5.       Arbitration. Any controversy or claim arising out of, or relating to,
this Agreement or the breach thereof shall be settled by arbitration in the City
of Atlanta in accordance with the laws of the State of Georgia by three
arbitrators, one of whom shall be appointed by the Company, one by the Employee
and the third of whom shall be appointed by the first two arbitrators. If the
first two arbitrators cannot agree on the appointment of a third arbitrator,
then the third arbitrator shall be appointed by the Chief Judge of the United
States Court of Appeals for the Eleventh Circuit. The arbitration shall be
conducted in accordance with the rules of the American Arbitration Association,
except with respect to

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the selection of arbitrators which shall be as provided in this Section 5. The
decision of the arbitrators shall be final and binding. The costs of
arbitration, including the reasonable attorney's fees of the prevailing party,
shall be borne by the losing party.

6.       Non-Alienation. No person may pledge, hypothecate, anticipate or in any
way create a lien upon any benefits provided under this Agreement; and no
benefits provided hereunder shall be assignable in anticipation of payment or
provision thereof either by voluntary or involuntary acts, or by operation of
law.

7.       Source of Payments. All benefits paid or provided to any person under
this Agreement shall be so paid or provided from the general funds of the
Company. This Agreement shall constitute a mere promise by the Company to pay or
provide benefits in the future. The parties hereto intend that this Agreement be
treated as unfunded for tax purposes, as well as for purposes of Title I of
ERISA. To the extent that any person acquires a right to receive a benefit from
the Company hereunder, such right shall be no greater than the right of a
general unsecured creditor of the Company.

8.       General Withholding. The Company may withhold, from any amount payable
under this Agreement, any tax or other deductions that are required to be
withheld by applicable law, as well as the employee portion of any
benefit-related premiums for which the employee is eligible and elected to
participate in.

9.       Partial Invalidity. If any provision of this Agreement is held by a
court of competent jurisdiction to be invalid, void or unenforceable, the
remaining provisions shall nevertheless continue in full force without being
impaired or invalidated in any way.

10.      Agreement Supersedes Any Inconsistent Prior Agreements or
Understandings. The terms of this Agreement supersede any inconsistent prior
promises, policies, representations, understandings, arrangements or agreements
between the parties with respect to the subject matter hereof; provided, that if
the Employee is a party to any other current severance agreement with the
Company pursuant to which the Employee would be entitled to benefits upon the
occurrence of a Transaction, the Employee shall be entitled to receive the
greater of the severance benefits thereunder or hereunder (but not under both).
It is further provided, however, that the conditions imposed under Section 3 of
this Agreement are in addition to, and not in substitution of, any conditions or
requirements that the Employee must satisfy under any written employment
agreement or written confidentiality agreement between the Company and the
Employee.

In the event the Employee has another active Severance Agreement in place with
the Employer that would trigger in the event of a Transaction, as described in
Paragraph 1 above, the Employee will be eligible to receive the greater of the
severance benefits provided by such Agreement (but not both).

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11.      Notices. All notices required or permitted to be given by either party
hereunder, including notice of change of address, shall be in writing and
delivered by hand, or mailed, postage prepaid, certified or registered mail,
return receipt requested, to the other party as follows:

         If to the Company:         Serologicals Corporation
                                    780 Park North Blvd., Suite 110
                                    Clarkston, GA 30021
                                    Attn:  Director, Human Resources

         If to the Employee:        3001 Brookmonte Lane
                                    Lexington, KY 40515

12.      Governing Law. This Agreement shall be governed by and construed in
accordance with the internal laws of the State of Georgia applicable to
contracts executed in and to be performed solely within such State.

13.      Further Assurances. The parties hereto agree that, after the execution
of this Agreement, they will make, do, execute or cause to permit to be made,
done or executed all such further and other lawful acts, deeds, things, devices,
conveyances and assurances in law whatsoever as may be required to carry out the
true intention and to give full force and effect to this Agreement.

14.      Counterparts. This Agreement may be executed in one or more
counterparts, each of which shall be deemed to be an original but all of which
together will constitute one and the same instrument.

15.      Amendment of Agreement. This Agreement may not be modified or amended
except by an instrument in writing signed by the parties hereto.

16.      Successors and Assigns. This Agreement shall inure to the benefit of,
and be binding upon, the Company, its successors and assigns and any corporation
with which the Company merges or consolidates or to which the Company sells all
or substantially all of its assets, and upon the Employee and his or her
executors, administrators, heirs and legal representatives.

IN WITNESS WHEREOF, the Employee has executed this Agreement, and the Company
has caused this Agreement to be executed by a duly authorized officer, as of the
day and year first above written.

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                                                   SEROLOGICALS CORPORATION

                                                   By: /s/ Regina S. Bryant
                                                       -------------------------

                                                       14 OCT 99
                                                       -------------------------
                                                       Date

                                                       /s/ Timm M. Hurst
                                                       -------------------------
                                                       Employee Name

                                                       14 OCT 99
                                                       -------------------------
                                                       Date

                                       6<PAGE>   1
                                                                   EXHIBIT 10.23
                            SEROLOGICALS CORPORATION
                              780 PARK NORTH BLVD.
                                    SUITE 110
                            CLARKSTON, GEORGIA 30021

                                                   November 12, 1999

Desmond H. O'Connell, Jr.
971 South Lagoon Lane
Mantoloking, NJ 08738

Dear Desmond:

                  I am pleased, on behalf of Serologicals Corporation (the
"Corporation"), to confirm the offer to you ("you") of employment on the terms
set forth herein (the "Offer").

                  You shall serve as the President and Chief Executive Officer
of the Corporation on an interim basis at the pleasure of the Board of Directors
or your earlier request. You shall be subject to the supervision, control and
guidance of, and shall report to, the Board of Directors. You agree to be
available and provide services for one month after the hiring of a permanent
Chief Executive Officer to assist in transition. You may be terminated with or
without cause at any time without any severance or other financial obligation to
you for your service as President and Chief Executive Officer other than
payments for amounts accrued and unpaid to the date of termination of your
employment hereunder. You may resign at any point.

                  You shall be paid $2,000 for each full business day worked.
Such compensation shall be payable to you in the manner and on the date(s) on
which the Corporation pays its other executive officers, but in no event less
frequently than monthly.

                  It is contemplated that in connection with your employment
hereunder, you may be required to incur business, entertainment and travel
expenses. The Corporation agrees to promptly reimburse you in full for all
reasonable out-of-pocket business, entertainment and other related expenses
(including all expenses of travel and living expenses while away from home,
travel from your home to Atlanta and hotel, meals and transportation in Atlanta)
incurred or expended by you incident to the performance of your duties
hereunder. Reimbursement of these expenses shall be "grossed-up" to the extent
they are taxable.

                  You are hereby granted Options to purchase seventy-five
thousand (75,000) shares of the Corporation's common stock ($.01 par value) at
an initial exercise price equal to $4.8125 (the fair market value as of the
close of business on the date hereof). The Options shall have a term of six (6)
years. Thirty-seven thousand five hundred (37,500) of such Options shall vest on
the date hereof and the remainder shall vest on the earlier of the hiring by the
Corporation
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Desmond H. O'Connell, Jr.
November 12, 1999
Page 2

of a permanent Chief Executive Officer or March 10, 2000 (the "Second Vesting
Date"); provided, that in the event of the termination of your employment for
any reason prior to the Second Vesting Date, any unvested Options shall expire.
Such options shall be issued pursuant to a stock option agreement entered into
by you and the Corporation and shall be subject to all the other terms and
conditions contained in the Corporation's Amended and Restated 1994 Omnibus
Incentive Plan, including a provision providing for acceleration of the vesting
of these options upon a "change in control".

                  This letter is to be governed by and interpreted in accordance
with the laws of the State of Georgia applicable to agreements made and to be
performed within that State except as otherwise provided herein.

                  If any provision of this letter shall be determined to be
invalid, illegal or unenforceable in whole or in part, all other provisions
hereof shall remain in full force and effect to the fullest extent permitted by
law.

                  The Corporation advises you that it is not providing legal
advice in connection with your acceptance and execution hereof and that, if you
so elect, you should consult with an attorney prior to such execution.

                  Please indicate your acceptance of this Offer by signing in
the space provided below.

                                Very truly yours,

                                SEROLOGICALS CORPORATION

                                By: /s/ Lawrence E. Tilton
                                --------------------------------------------
                                Name:       Lawrence E. Tilton
                                Title:      Chairman, Compensation Committee

ACKNOWLEDGED AND AGREED

/s/ Desmond H. O'Connell, Jr.
-----------------------------
Desmond H. O'Connell, Jr.

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