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                                                                     EXHIBIT 4.5


                                SIPEX CORPORATION

                             STOCK OPTION AGREEMENT


      SIPEX Corporation (the "Company") hereby grants the following option to
purchase Common Stock, $.01 par value per share (the "Common Stock"), of the
Company pursuant to an action of the Board of Directors (the "Board") of the
Company on 5/17/01. The terms and conditions attached hereto are also a part
hereof.



      Name of employee (the "Employee" or "Optionee"):          RAVI NANDAN

      Date of this option grant:                                  5/17/01

      Number of shares of the Company's Common Stock
      subject to this option ("Option Shares"):                    25,000

      Option exercise price per share:                           $12.1400

      Number of Option Shares subject to  vesting schedule:        25,000

      Vesting Start Date:                                         5/17/01

      Vesting Schedule. If the Employee has continued to be employed by the
      Company or any Related Corporation (as defined in Section 2 hereof) on the
      following dates, the Employee may exercise this option for the number of
      shares of Common Stock as set forth below.

      Prior to 5/17/02                         0 shares

      As of 5/17/02 but prior to 5/17/03       5,000 shares

      As of 5/17/03 but prior to 5/17/04       an additional 5,000 shares

      As of 5/17/04 but prior to 5/17/05       an additional 5,000 shares

      As of 5/17/05 but prior to 5/17/06       an additional 5,000 shares

      As of 5/17/06                            an additional 5,000 shares

      Payment alternatives:                    Section 6(a) (i) through
                                               (iv)


                                         SIPEX CORPORATION
 /s/Ravi Nandan
-------------------------------------
RAVI NANDAN  Signature of Optionee


------------------------------------
1296 JULY LYNN DRIVE

====================================     By:       /s/James E. Donegan
                                              ------------------------
SAN JOSE, CA   95120                             James E. Donegan
                                                Chairman and Chief Executive
                                                Officer
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SIPEX CORPORATION

STOCK OPTION AGREEMENT -- INCORPORATED TERMS AND CONDITIONS

         1. GRANT AS NON-QUALIFIED STOCK OPTION. This option is a non-statutory
stock option and is not intended to qualify as an incentive stock option under
Section 422 of the Internal Revenue Code of 1986, as amended, and the
regulations thereunder (the "Code").

         2. VESTING OF OPTION IF EMPLOYMENT CONTINUES. The Employee may exercise
this option for the number of shares of Common Stock set forth on the vesting
schedule on the cover page hereof if the Employee has continued to be employed
by the Company or any present or future parent or subsidiary of the Company
(collectively, "Related Corporations") in accordance with such vesting schedule.
Notwithstanding the foregoing, the Board may, in its discretion, accelerate the
date that any installment of this option becomes exercisable. The foregoing
rights are cumulative and (subject to Sections 3 or 4 hereof if the Employee
ceases to be employed by the Company) may be exercised only before the date
which is ten years from the date of this option grant.

         3. TERMINATION OF EMPLOYMENT.

            (a) TERMINATION OTHER THAN FOR CAUSE. If the Employee ceases to be
employed by the Company and all Related Corporations, other than by reason of
death or disability as defined in Section 4 or termination for Cause as defined
in Section 3(c), no further installments of this option shall become
exercisable, and this option shall terminate (and may no longer be exercised)
after the passage of three months from the Employee's last day of employment,
but in no event later than the scheduled expiration date. In such a case, the
Employee's only rights hereunder shall be those which are properly exercised
before the termination of this option.

            (b) TERMINATION FOR CAUSE. If the employment of the Employee is
terminated for Cause (as defined in Section 4(c)), this option shall terminate
upon the Employee's receipt of written notice of such termination and shall
thereafter not be exercisable to any extent whatsoever.

            (c) DEFINITION OF CAUSE. "CAUSE" shall mean conduct involving one or
more of the following: (i) the substantial and continuing failure of the
Employee, after notice thereof, to render services to the Company or any Related
Entity in accordance with the terms or requirements of his employment or
business relationship; (ii) disloyalty, gross negligence, willful misconduct,
dishonesty, fraud or breach of fiduciary duty to the Company or any Related
Entity; (iii) the commission of an act of embezzlement or fraud; (iv) deliberate
disregard of the rules or policies of the Company or any Related Entity, or
breach of an employment or other agreement with the Company or any Related
Entity, which results in direct or indirect loss, damage or injury to the
Company or any Related Entity; (v) the unauthorized disclosure of any trade
secret or confidential information of the Company or any Related Entity; or (vi)
the commission of an act which constitutes unfair competition with the Company
or any Related Entity or which induces any customer or supplier to breach a
contract with the Company or any Related Entity.

         4. DEATH; DISABILITY.

            (a) DEATH. If the Employee dies while in the employ of the Company
or any Related Corporation, this option may be exercised, to the extent
otherwise exercisable on the date of his or her death, by the Employee's estate,
personal representative or beneficiary to whom this option has been assigned
pursuant to Section 9, at any time within 180 days after the date of death, but
not later than the scheduled expiration date.
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            (b) DISABILITY. If the Employee ceases to be employed by the Company
and all Related Corporations by reason of his disability, this option may be
exercised, to the extent otherwise exercisable on the date of the termination of
his employment, at any time within 180 days after such termination, but not
later than the scheduled expiration date. The term disability means "permanent
and total disability" as defined in Section 22(e)(3) of the Code.

            (c) EFFECT OF TERMINATION. At the expiration of the 180-day period
provided in paragraph (a) or (b) of this Section 4 or the scheduled expiration
date, whichever is the earlier, this option shall terminate (and shall no longer
be exercisable) and the only rights hereunder shall be those as to which the
option was properly exercised before such termination.

         5. PARTIAL EXERCISE. This option may be exercised in part at any time
and from time to time within the above limits, except that this option may not
be exercised for a fraction of a share.

         6. PAYMENT OF ALTERNATIVES. (a) The exercise price shall be paid in the
following manner:

                  (i)      in cash or by check;

                  (ii)     subject to paragraph 6(b) below, by delivery of
                           shares of the Company's Common Stock having a fair
                           market value equal, as of the date of exercise, to
                           the option exercise price;

                  (iii)    by delivery of an assignment satisfactory in form and
                           substance to the Company of a sufficient amount of
                           the proceeds from the sale of the Option Shares and
                           an instruction to the broker or selling agent to pay
                           that amount to the Company; or

                  (iv)     by any combination of the foregoing.

                   In the case of (ii) above, fair market value as of the date
      of exercise shall be determined as of the last business day for which such
      prices or quotes are available prior to the date of exercise and shall
      mean (i) the average (on that date) of the high and low prices of the
      Common Stock on the principal national securities exchange on which the
      Common Stock is traded, if the Common Stock is then traded on a national
      securities exchange; or (ii) the last reported sale price (on that date)
      of the Common Stock on the Nasdaq National Market, if the Common Stock is
      not then traded on a national securities exchange; or (iii) the closing
      bid price (or average of bid prices) last quoted (on that date) by an
      established quotation service for over-the-counter securities, if the
      Common Stock is not reported on the Nasdaq National Market. If the Common
      Stock is not publicly traded at the time of exercise, "fair market value"
      shall mean the fair value of the Common Stock as determined by the Board
      after taking into consideration all factors which it deems appropriate,
      including, without limitation, recent sale and offer prices of the Common
      Stock in private transactions negotiated at arm's length.

            (b) LIMITATIONS ON PAYMENT BY DELIVERY OF COMMON STOCK. If the
Employee delivers Common Stock held by the Employee ("Old Stock") to the Company
in full or partial payment of the option price, and the Old Stock so delivered
is subject to restrictions or limitations imposed by agreement between the
Employee and the Company, an equivalent number of Option Shares shall be subject
to all restrictions and limitations applicable to the Old Stock to the extent
that the Employee paid for the Option Shares by delivery of Old Stock, in
addition to any restrictions or limitations imposed by this Agreement.
Notwithstanding the foregoing, the Employee may not pay any part of the exercise
price hereof by transferring Common Stock to the Company unless such Common
Stock has been owned by the Employee free of any substantial risk of forfeiture
for at least six months.

         7. METHOD OF EXERCISING OPTION. Subject to the terms and conditions of
this Agreement, this option may be exercised by written notice to the Company at
its principal executive office, or to such
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transfer agent as the Company shall designate. Such notice shall state the
election to exercise this option and the number of Option Shares for which it is
being exercised and shall be signed by the person or persons so exercising this
option. Such notice shall be accompanied by payment of the full purchase price
of such shares, and the Company shall deliver a certificate or certificates
representing such shares as soon as practicable after the notice shall be
received. Such certificate or certificates shall be registered in the name of
the person or persons so exercising this option (or, if this option shall be
exercised by the Employee and if the Employee shall so request in the notice
exercising this option, shall be registered in the name of the Employee and
another person jointly, with right of survivorship). In the event this option
shall be exercised, pursuant to Section 4 hereof, by any person or persons other
than the Employee, such notice shall be accompanied by appropriate proof of the
right of such person or persons to exercise this option.

         8. SECURITIES LAWS RESTRICTIONS ON RESALE. Until registered under the
Securities Act of 1933, as amended, or any successor statute (the "Securities
Act"), the Option Shares will be of an illiquid nature and will be deemed to be
"restricted securities" for purposes of the Securities Act. Accordingly, such
shares must be sold in compliance with the registration requirements of the
Securities Act or an exemption therefrom. Unless the Option Shares have been
registered under the Securities Act, each certificate evidencing any of the
Option Shares shall bear a legend substantially as follows:

      "The shares represented by this certificate are subject to restrictions on
      transfer and may not be sold, exchanged, transferred, pledged,
      hypothecated or otherwise disposed of except in accordance with and
      subject to all the terms and conditions of a certain Stock Option
      Agreement dated as of 5/17/01, a copy of which the Company will furnish to
      the holder of this certificate upon request and without charge."

         9. OPTION NOT TRANSFERABLE. This option is not transferable or
assignable except by will or by the laws of descent and distribution. During the
Optionee's lifetime only the Optionee can exercise this option.

         10. NO OBLIGATION TO EXERCISE OPTION. The grant and acceptance of this
option imposes no obligation on the Optionee to exercise it.

         11. ADJUSTMENTS. In the event of any stock split, stock dividend,
extraordinary cash dividend, recapitalization, reorganization, merger,
consolidation, combination, exchange of shares, liquidation, spin-off, split-up,
or other similar change in capitalization or event, the number and class of
securities, vesting schedule and exercise price per share of this option shall
be adjusted by the Company (or a substituted option may be granted) to the
extent the Board shall determine, in good faith, that such an adjustment (or
substitution) is appropriate. Except as is expressly provided in this Section
11, no adjustment shall be made for dividends or similar rights for which the
record date is prior to such date of exercise.

         12. WITHHOLDING TAXES. If the Company or any Related Corporation in its
discretion determines that it is obligated to withhold any tax in connection
with the exercise of this option, or in connection with the transfer of, or the
lapse of restrictions on, any Common Stock or other property acquired pursuant
to this option, the Optionee hereby agrees that the Company or any Related
Corporation may withhold from the Optionee's wages or any other remuneration the
appropriate amount of tax. At the discretion of the Company or Related
Corporation, the amount required to be withheld may be withheld in cash from
such wages or other remuneration or in kind from the Common Stock or other
property otherwise deliverable to the Optionee on exercise of this option. The
Optionee further agrees that, if the Company or Related Corporation does not
withhold an amount from the Optionee's wages or other remuneration sufficient to
satisfy the withholding obligation of the Company or Related Corporation, the
Optionee will make reimbursement on demand, in cash, for the amount
underwithheld.

         13. ARBITRATION. Any dispute, controversy, or claim arising out of, in
connection with, or relating to the performance of this Agreement or its
termination shall be settled by arbitration in the
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Commonwealth of Massachusetts, pursuant to the rules then obtaining of the
American Arbitration Association. Any award shall be final, binding and
conclusive upon the parties and a judgment rendered thereon may be entered in
any court having jurisdiction thereof.

         14. PROVISION OF DOCUMENTATION TO OPTIONEE. By signing this Agreement
the Optionee acknowledges receipt of a copy of this Agreement.

         15. MISCELLANEOUS.

            (a) NOTICES. All notices hereunder shall be in writing and shall be
deemed given when sent by certified or registered mail, postage prepaid, return
receipt requested, if to the Optionee, to the address set forth on the cover
pages hereof or at the address shown on the records of the Company, and if to
the Company, to the Company's principal executive offices, attention of the
Corporate Secretary.

            (b) ENTIRE AGREEMENT; MODIFICATION. This Agreement constitutes the
entire agreement between the parties relative to the subject matter hereof, and
supersedes all proposals, written or oral, and all other communications between
the parties relating to the subject matter of this Agreement. This Agreement may
be modified, amended or rescinded only by a written agreement executed by both
parties.

            (c) FRACTIONAL SHARES. If this option becomes exercisable for a
fraction of a share because of the adjustment provisions contained herein, such
fraction shall be rounded down.

            (d) NO RIGHTS AS STOCKHOLDER. The Optionee shall not have any rights
as a stockholder with respect to any shares of Common Stock for which this
option is exercisable until such Optionee becomes the record holder of such
shares of Common Stock.

            (e) NO OBLIGATION OF CONTINUED EMPLOYMENT. This Agreement imposes no
obligation on the Company or Related Corporation to continue the employment of
the Employee. The Company expressly reserves the right any time to dismiss or
terminate its relationship with the Employee free from any liability or claim
under this Agreement.

            (f) ISSUANCES OF SECURITIES; CHANGES IN CAPITAL STRUCTURE. Except as
expressly provided herein, no issuance by the Company of shares of stock of any
class, or securities convertible into shares of stock of any class, shall
affect, and no adjustment by reason thereof shall be made with respect to, the
number or price of shares subject to this option. No adjustments need be made
for dividends paid in cash or in property other than securities of the Company.
If there shall be any change in the Common Stock of the Company through merger,
consolidation, reorganization, recapitalization, stock dividend, stock split,
combination or exchange of shares, spin-off, split-up or other similar change in
capitalization or event, the restrictions contained in this Agreement shall
apply with equal force to additional and/or substitute securities, if any,
received by the Optionee in exchange for, or by virtue of his or her ownership
of, Option Shares, except as otherwise determined by the Board.

            (g) DISSOLUTION OR LIQUIDATION. In the event of the proposed
dissolution or liquidation of the Company, then the Board shall, as to
outstanding options, at its discretion provide, upon written notice to the
Optionee (i) that all options must be exercised, to the extent then exercisable,
within a specified number of days of the date of such notice, at the end of
which period, the options shall terminate or (ii) that such options (including
those which have not yet vested) shall be exercisable within a specified number
of days of such notice, at the end of which period the options shall terminate.

            (h) SEVERABILITY. The invalidity, illegality or unenforceability of
any provision of this Agreement shall in no way affect the validity, legality or
enforceability of any other provision.
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            (i) SUCCESSORS AND ASSIGNS. This Agreement shall be binding upon and
inure to the benefit of the parties hereto and their respective successors and
assigns, subject to the limitations set forth in Section 9 hereof.

            (j) GOVERNING LAW. This Agreement shall be governed by and
interpreted in accordance with the laws of the Commonwealth of Massachusetts,
without giving effect to the principles of the conflicts of laws thereof.