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                                                                  Exhibit 10.8.1


                                 FIRST AMENDMENT

                                     TO THE

                  MASTER SEPARATION AND DISTRIBUTION AGREEMENT



                  This First Amendment to the Master Separation and Distribution
Agreement (this "Amendment") is entered into effective as of August 1, 2001, by
and among SeraCare, Inc., a Delaware corporation ("SeraCare") and SeraCare Life
Sciences, Inc., a California corporation ("Life Sciences").

                  WHEREAS, SeraCare and Life Sciences are parties to that
certain Master Separation and Distribution Agreement, dated June 10, 2001 (the
"Separation Agreement");

                  WHEREAS, SeraCare has changed the ratio of shares of Life
Sciences that will be issued in the Distribution (as such term is defined in the
Separation Agreement) from a ratio of one share of Life Sciences common stock
for every one share of SeraCare common stock held by a stockholder as of the
record date for the Distribution, to a ratio of two shares of Life Sciences
common stock for every five shares of SeraCare common stock held by a
stockholder as of the record date for the Distribution (the "Distribution
Ratio"); and

                  WHEREAS, SeraCare and Life Sciences wish to amend the
Separation Agreement with the consent of Instituto Grifols, S.A., a company
organized under the laws of Spain, a third party beneficiary to the Separation
Agreement, in order to reflect the revised Distribution Ratio.

                  NOW, THEREFORE, in consideration of the foregoing premises and
for good and valuable consideration, the receipt of which is hereby
acknowledged, the parties hereto agree as follows:

5.   Amendments to the Separation Agreement.

     a.   Section 3.2(b) of the Separation Agreement is hereby replaced in its
          entirety as follows:

          "Shares Received. Subject to Section 3.3, each holder of common stock
           ---------------
          of SeraCare on the Record Date (or such holder's designated transferee
          or transferees) will be entitled to receive in the Distribution a
          number of shares of common stock of Life Sciences equal to forty
          percent (40%) of the number of shares of common stock of SeraCare held
          by such holder on the Record Date."

     b.   Section 3.2(c) of the Separation Agreement is hereby replaced in its
          entirety as follows:

          "Options and Warrants Received. Subject to Section 3.3, each holder on
           -----------------------------
          the Record Date of stock options (the "SeraCare Options") or warrants
          (the "SeraCare Warrants") to purchase the common stock of SeraCare
          will be entitled to receive in connection with the Distribution new
          options or warrants, as applicable, (i) to purchase a number of shares
          of Life Sciences Common Stock equal to forty percent (40%) of the
          number of shares underlying the SeraCare Options or SeraCare Warrants
          held by such holder on the Record Date, with an exercise price equal
          to the Calculated Exercise Price multiplied by

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          two and one-half (2.5), and (ii) to purchase a number of shares of
          SeraCare Common Stock equal to the number of shares underlying the
          SeraCare Options or SeraCare Warrants held by such holder on the
          Record Date, with an exercise price equal to the Adjusted Exercise
          Price."

6.   Governing Law. This Amendment shall be governed by and construed in
accordance with the laws of the State of Delaware, without regard to its rules
regarding conflicts of laws.

7.   Counterparts. This Agreement may be executed by the parties hereto in
separate counterparts, each of which when so executed and delivered shall be an
original, but all such counterparts shall together constitute one and the same
instrument.



                         [SIGNATURES ON FOLLOWING PAGE]


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                  IN WITNESS WHEREOF, SeraCare and Life Sciences, with the
acknowledgment and consent of Instituto Grifols, S.A., have caused this
Amendment to be signed by their respective officers thereunder duly authorized
all as of the date first written above.



SERACARE, INC.


By:  /s/ Barry D. Plost
     ------------------
     Print Name:  Barry D. Plost
                  --------------
     Title: President
            ---------


SERACARE LIFE SCIENCES, INC.


By:  /s/ Jerry L. Burdick
     --------------------
     Print Name: Jerry L. Burdick
                 ----------------
     Title: Executive V.P.
            --------------


AGREED AND ACCEPTED:

INSTITUTO GRIFOLS, S.A.


By:  /s/ Victor Grifols
     ------------------
     Print Name: Victor Grifols
                 --------------
     Title: CEO
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