<PAGE>

                                                                   EXHIBIT 10.22

                           STOCK PURCHASE AGREEMENT
                           ------------------------


          STOCK PURCHASE AGREEMENT, dated as of July 30, 1999, by and between
SpectruMedix Corporation, a Delaware corporation (the "Company"), and PE
Corporation, a Delaware corporation (the "Purchaser").

                             W I T N E S S E T H:
                             - - - - - - - - - -

          WHEREAS, concurrently herewith, the Company and The Perkin-Elmer
Corporation, a New York corporation and wholly-owned subsidiary of the Purchaser
("Perkin-Elmer"), are entering into that certain License Agreement concerning
certain patents and technology in substantially the form set forth in Exhibit A
                                                                      ---------
hereto (the "License Agreement") and that certain Consulting Agreement in
substantially the form set forth in Exhibit B hereto (the "Consulting
                                    ---------
Agreement"); and

          WHEREAS, in connection with the License Agreement, the Purchaser has
agreed to purchase shares of preferred stock of the Company;

          NOW, THEREFORE, in consideration of the premises and of the mutual
representations, warranties and agreements set forth herein, the Company and the
Purchaser agree as follows:

                                   ARTICLE I

                        PURCHASE AND SALE OF THE STOCK

     1.1  Purchase and Sale.  Subject to the terms and conditions of this
          -----------------
Agreement, on the Closing Date, the Company shall issue and deliver to
Purchaser, and Purchaser agrees to purchase from the Company, 2,000 shares of
authorized but unissued shares of the Series A Preferred Stock, par value
$.00115 per share (the "Shares").

     1.2  Purchase Price.  The purchase price for each Share is $1,000 and the
          --------------
aggregate purchase price for all the Shares is Two Million Dollars ($2,000,000).
The Purchaser shall pay the Purchase Price on the Closing Date by wire transfer
of immediately available funds to the Company against the issuance and delivery
to Purchaser of a certificate evidencing the Shares.

     1.3  Time and Place of Transaction.  The consummation of the purchase and
          -----------------------------
sale of the Shares (the "Closing") shall take place at the offices of the
Company's counsel on or before July 30, 1999 at 10:00 A.M., New York time, or at
such other place or time or earlier date as the Company and Purchaser may
mutually agree (the "Closing Date").

                                  ARTICLE II

                 REPRESENTATIONS AND WARRANTIES OF THE COMPANY

          As a material inducement to Purchaser to enter into this Agreement and
purchase the Series A Preferred Stock, the Company represents and warrants that:
<PAGE>

     2.1  Due Organization and Qualification; Due Authorization.
          -------------------------------------------------------

          (a)  The Company is a corporation duly incorporated, validly existing
and in good standing under the laws of its jurisdiction of formation, with full
corporate power and authority to own, lease and operate its business and
properties and to carry on its business in the places and in the manner as
presently conducted or proposed to be conducted. The Company is in good standing
as a foreign corporation in each jurisdiction in which the properties owned,
leased or operated, or the business conducted, by it requires such qualification
except for any such failure, which when taken together with all other failures,
is not likely to have a material adverse effect on the business, properties,
financial condition or results of operations of the Company (a "Material Adverse
Effect").

          (b)  The Company does not own, directly or indirectly, any capital
stock, equity or interest in any corporation, firm, partnership, joint venture
or other entity.

          (c)  The Company has all requisite corporate power and authority to
execute and deliver this Agreement and the Additional Agreements and to
consummate the transactions contemplated hereby and thereby. The Company has
taken all corporate action necessary for the execution and delivery of this
Agreement and the Additional Agreements and the consummation of the transactions
contemplated hereby and thereby, and this Agreement and the Additional
Agreements constitute the valid and binding obligations of the Company,
enforceable against the Company in accordance with their respective terms,
except as may be affected by bankruptcy, insolvency, moratoria or other similar
laws affecting the enforcement of creditors' rights generally and subject to the
qualification that the availability of equitable remedies is subject to the
discretion of the court before which any proceeding therefor may be brought.

     2.2  No Conflicts or Defaults. The execution and delivery of this Agreement
          ------------------------
and the Additional Agreements by the Company and the consummation of the
transactions contemplated hereby and thereby do not and will not (a) contravene
the certificate of incorporation or by-laws of the Company or (b) with or
without the giving of notice or the passage of time, (i) violate, conflict with,
or result in a breach of, or a default or loss of rights under, any material
covenant, agreement, mortgage, indenture, lease, instrument, permit or license
to which the Company is a party or by which the Company or any of its assets is
bound, or any judgment, order or decree, or any law, rule or regulation to which
the Company or any of its assets is subject, (ii) result in the creation of, or
give any party the right to create, any lien, charge, security interest,
encumbrance or any other right or adverse interest ("Liens") upon any of the
capital stock or assets of the Company, or (iii) result in a violation of or
require any authorization, consent, approval, exemption or other action by or
notice or declaration to, or filing with, any court or administrative or
governmental body or agency (a "Governmental Entity") pursuant to, the
certificate of incorporation or by-laws of the Company or any law, statute, rule
or regulation to which the Company is subject, or any agreement, instrument,
order, judgment or decree to which the Company is subject.

     2.3  Capitalization.  As of the date hereof, the authorized capital stock
          --------------
of the Company consists of 23,000,000 shares of Common Stock, of which 3,530,214
shares were issued and outstanding on July 28, 1999, and 2,000,000 shares of
preferred stock (the "Preferred Stock"), of which none are issued and
outstanding.  Except as set forth on Schedule 2.3, neither the Common Stock nor
the Preferred Stock is subject to any preemptive or subscription right, any
voting trust agreement or other contract, agreement, arrangement, option,
warrant, call,

                                      -2-
<PAGE>

commitment or other right of any character obligating or entitling the Company
to issue, sell, redeem or repurchase any of its securities, and there is no
outstanding security of any kind convertible into or exercisable or exchangeable
for Common Stock. Except as set forth on Schedule 2.3, there are no agreements
or arrangements pursuant to which the Company is or could be required to
register shares of the Company's capital stock or other securities under the
Securities Act or other agreements or arrangements (including voting agreements)
with or, to the knowledge of the Company, among any securityholders of the
Company with respect to any securities of the Company. The offer, sale and
issuance of the Series A Preferred Stock pursuant to Section 1.1 this Agreement,
and the Common Stock issuable upon conversion of the Series A Preferred Stock,
do not and will not, as the case may be, require registration under the
Securities Act or any applicable state securities laws.

     2.4  Validity of Shares.  The Shares, when issued, sold and delivered in
          ------------------
accordance with the terms and for the consideration expressed in this Agreement,
shall be duly and validly issued (including, without limitation, issued in
compliance with applicable federal and state securities laws), fully paid and
non-assessable and free of any liens, encumbrances or preemptive or similar
rights (or agreements for any such rights).  The shares of Common Stock issuable
upon conversion of the Shares are not subject to any preemptive or similar
rights (or agreements for any such rights) and, assuming such Common Stock is
issued to the Purchaser, upon issuance in accordance with the Amended Charter
shall be duly and validly issued (including, without limitation, issued in
compliance with all applicable federal and state securities laws), fully paid
and non-assessable.

     2.5  SEC Documents.  Except as set forth on Schedule 2.5, the Company has
          -------------
filed with the SEC all reports, schedules, forms, statements and other documents
required pursuant to the Securities Act and the Exchange Act since September 1,
1997 (collectively, and in each case including all exhibits and schedules
thereto and documents incorporated by reference therein, the "SEC Documents").
As of their respective dates, the SEC Documents complied as to form in all
material respects with the requirements of the Securities Act or the Exchange
Act, as the case may be, and the rules and regulations of the SEC promulgated
thereunder applicable to such SEC Documents.  As of their respective dates, (i)
none of the SEC Documents (including any and all financial statements included
therein) filed pursuant to the Securities Act or any rule or regulation
thereunder contained any untrue statement of a material fact or omitted to state
a material fact required to be stated therein or necessary in order to make the
statements therein not misleading and (ii) none of the SEC Documents (including
any and all financial statements included therein) filed pursuant to the
Exchange Act or any rule or regulation thereunder contained any untrue statement
of a material fact or omitted to state a material fact required to be stated
therein or necessary in order to make the statements therein, in the light of
the circumstances under which they were made, not misleading.  Except to the
extent that information contained in any SEC Document has been revised or
superseded by a later filed SEC Document, none of the SEC Documents (including
any and all financial statements included therein) contains any untrue statement
of a material fact or omits to state a material fact required to be stated
therein or necessary in order to make the statements therein, in the light of
the circumstances under which they were made, not misleading.  The consolidated
financial statements of the Company included in all SEC Documents filed since
September 1, 1997 (the "SEC Financial Statements") comply as to form in all
material respects with applicable accounting requirements and the published
rules and regulations of the SEC with respect thereto, have been prepared in
accordance with generally accepted accounting principles (except, in the case of
unaudited consolidated quarterly statements, as permitted by Form 10-Q of the
SEC),

                                      -3-
<PAGE>

applied on a consistent basis during the periods involved (except as may be
indicated in the notes thereto). The SEC Financial Statements fairly present the
consolidated financial position of the Company as of the dates thereof and the
consolidated results of its operations and cash flows for the periods then ended
(subject, in the case of unaudited quarterly statements, to normal recurring
audit adjustments).

     2.6  Financial Statements; Undisclosed Liabilities.  The Company has
          ---------------------------------------------
furnished to the Purchaser its audited balance sheet as of March 31, 1998 and
the corresponding audited statements of income, cash flows and stockholders'
equity for the fiscal year then ended and its unaudited balance sheet as of
December 31, 1998 and the corresponding unaudited statements of income, cash
flows and stockholders' equity for the nine months ended December 31, 1998
(collectively, the "Financial Statements").  The Financial Statements (i) have
been prepared in accordance with generally accepted accounting principles,
applied on a consistent basis throughout the periods indicated, (ii) are
complete and correct in all material respects, and (iii) are consistent with the
books and records of the Company and fairly present the consolidated financial
position of the Company as of the dates thereof and the consolidated results of
operations of its operations and cash flows for the periods then ended (subject,
in the case of unaudited quarterly statements, to normal recurring audit
adjustments). The Company does not have any liabilities or obligations of any
nature (whether accrued, absolute, contingent or otherwise) required by
generally accepted accounting principles to be recognized or disclosed on a
consolidated balance sheet of the Company or in the notes thereto, except (i)
liabilities reflected in the consolidated unaudited balance sheet of the Company
as of December 31, 1998 or the notes thereto (subject to ordinary year-end
adjustments), and (ii) liabilities incurred since December 31, 1998 in the
ordinary course of business consistent with past practice.

     2.7  Absence of Certain Changes or Events.  Except as disclosed on Schedule
          ------------------------------------
2.7, since December 31, 1998, the Company has conducted its business only in the
ordinary course consistent with past practice, and there is not and has not
been:  (i) since December 31, 1998, any condition, event or occurrence which has
had a Material Adverse Effect with respect to the Company; (ii) since December
31, 1998, any condition, event or occurrence which as of the date of this
Agreement, individually or in the aggregate, could reasonably be expected to
have a Material Adverse Effect with respect to the Company; or (iii) since
December 31, 1998, any condition, event or occurrence which, individually or in
the aggregate, could reasonably be expected to prevent or materially delay the
ability of the Company to consummate the transactions contemplated by this
Agreement or the Additional Agreements or perform its obligations hereunder or
thereunder.

     2.8  Litigation. Except as disclosed on Schedule 2.8, there is (a) no suit,
          ----------
action, arbitration or proceeding pending, and (b) to the knowledge of the
Company, no suit, action, arbitration or proceeding threatened against or
investigation pending with respect to the Company that, individually or in the
aggregate, could reasonably be expected to have a Material Adverse Effect with
respect to the Company or prevent or materially delay the ability of the Company
to consummate the transactions contemplated by this Agreement or the Additional
Agreements or to perform its obligations hereunder or thereunder, nor is there
any judgment, decree, citation, injunction, rule or order of any Governmental
Entity or arbitrator outstanding against the Company which, individually or in
the aggregate, has or could reasonably be expected to have, any such effect.

                                      -4-
<PAGE>

     2.9  Compliance with Laws.  The Company holds all permits, licenses,
          --------------------
variances, exemptions, orders and approvals of all Governmental Entities which
are material to the operation of the businesses of the Company (the "Company
Permits").  The Company is in compliance with the terms of the Company Permits,
except where the failure so to comply, individually or in the aggregate, would
not have a Material Adverse Effect with respect to the Company.  The businesses
of the Company are not being conducted in violation of any law (domestic or
foreign), ordinance or regulation of any Governmental Entity, except for
possible violations which, individually or in the aggregate, do not and could
not reasonably be expected to have a Material Adverse Effect with respect to the
Company.

                                  ARTICLE III

                  REPRESENTATIONS AND WARRANTIES OF PURCHASER

          The Purchaser represents and warrants to the Company that:

     3.1  Due Authorization; Valid Obligation.  The Purchaser or Perkin-Elmer,
          -----------------------------------
as the case may be, has or prior to the Closing Date will have taken all
corporate action necessary to authorize it or Perkin-Elmer, as the case may be,
to execute and deliver this Agreement and the Additional Agreements, and to
consummate the transactions contemplated hereby and thereby, and this Agreement
and the Additional Agreements constitute the valid and binding obligations of
the Purchaser or Perkin-Elmer, as the case may be, enforceable against the
Purchaser or Perkin-Elmer, as the case may be, in accordance with their
respective terms, except as may be limited by bankruptcy, insolvency, moratoria
or other similar laws affecting the enforcement of creditors' rights generally
and subject to the qualification that the availability of equitable remedies is
subject to the discretion of the court before which any proceeding therefor may
be brought.

     3.2  No Conflicts.  The execution and delivery by the Purchaser of this
          ------------
Agreement and by Perkin-Elmer of the Additional Agreements and the consummation
of the transactions contemplated hereby and thereby do not and will not (a)
contravene the certificate of incorporation or by-laws (or similar governing
instruments) of the Purchaser or Perkin-Elmer, as the case may be, or (b) with
or without the giving of notice or the passage of time, violate, conflict with,
or result in a breach of, or a default or loss of rights under, or require any
authorization, consent, approval or other action under, any material covenant,
agreement, mortgage, indenture, lease or instrument to which the Purchaser or
Perkin-Elmer, as the case may be,  is a party or by which the Purchaser or
Perkin-Elmer, as the case may be, or any of its assets is bound, or any
judgment, order, decree, law, rule or regulation to which the Purchaser or
Perkin-Elmer, as the case may be, or any of its assets is subject.

     3.3  Purchase for Investment.
          -----------------------

          (a)  The Purchaser is acquiring the Shares for investment for the
Purchaser's own account and not as a nominee or agent, and not with a view to
the resale or distribution of any part thereof, and the Purchaser has no present
intention of selling, granting any participation in, or otherwise distributing
the same. The Purchaser further represents that it does not have any contract,
undertaking, agreement or arrangement with any Person to sell, transfer or grant
a participation to such Person or to any third Person, with respect to any of
the Shares.

                                      -5-
<PAGE>

          (b)  The Purchaser understands that the Shares are not registered
under the Act on the ground that the sale and the issuance of securities
hereunder is exempt from registration under the Act pursuant to Section 4(2)
thereof, and that the Company's reliance on such exemption is predicated on the
Purchaser's representations set forth herein. The Purchaser is an "accredited
investor" as that term is defined in Rule 501(a) of Regulation D under the Act.

     3.4  Investment Experience.  The Purchaser acknowledges that it can bear
          ---------------------
the economic risk of its investment in the Shares, and has such knowledge and
experience in financial and business matters that it is capable of evaluating
the merits and risks of the investment in the Shares.

     3.5  Information. The Purchaser has been given the opportunity to review
          -----------
such information as it deemed necessary to evaluate an investment in the Series
A Preferred Stock. The Purchaser has been afforded the opportunity to ask
questions of representatives of the Company concerning the terms and conditions
of the offering.

     3.6  Restricted Securities.  The Purchaser understands that the Shares and
          ---------------------
the shares of Common Stock issuable upon conversion of the Series A Preferred
Stock (the "Restricted Shares") may not be sold, transferred, or otherwise
disposed of without registration under the Act or an exemption therefrom, and
that in the absence of an effective registration statement covering the Shares
or any available exemption from registration under the Act, the Restricted
Shares must be held indefinitely.  The Purchaser is aware that the Restricted
Shares may not be sold pursuant to Rule 144 promulgated under the Act unless all
of the conditions of that Rule are met.  Among the conditions for use of Rule
144 may be the availability of current information to the public about the
Company.

                                  ARTICLE IV

                CONDITIONS TO THE OBLIGATIONS OF THE PURCHASER

          The obligations of the Purchaser under this Agreement are subject to
the satisfaction, on or prior to the Closing Date, of the following conditions,
any of which may be waived in whole or in part by the Purchaser:

     4.1  Due Performance.  The Company shall have performed and complied in all
          ---------------
material respects with all agreements and conditions required by this Agreement
to be performed or complied with by it on or prior to the Closing Date.

     4.2  Accuracy of Representations and Warranties.  All representations and
          ------------------------------------------
warranties of the Company set forth in this Agreement shall be true and correct
in all material respects on and as of the Closing Date, as though made on and as
of the Closing Date.

     4.3  Amended Charter.  The Company shall have duly adopted, executed and
          ---------------
filed with the Secretary of State of Delaware the Amended Charter providing for
rights and preferences establishing the terms and the relative rights and
preferences of the Series A Preferred Stock in the form set forth in Exhibit C
                                                                     ---------
hereto, and the Company shall not have adopted or filed any other document
designating terms, relative rights or preferences of the Series A Preferred
Stock. The Amended Charter shall be in full force and effect as of the Closing
under the laws of the state of Delaware and shall not have been amended or
modified.

                                      -6-
<PAGE>

     4.4  Securities Law Compliance.  The Company shall have made all filings
          -------------------------
under all applicable federal and state securities laws necessary to consummate
the issuance of the Series A Preferred Stock pursuant to this Agreement in
compliance with such laws.

     4.5  License Agreement.  The Company shall have executed and delivered the
          -----------------
License Agreement.

     4.6  Consulting Agreement.  The Company shall have executed and delivered
          --------------------
the Consulting Agreement.

     4.7  Closing Documents.  The Company shall have delivered to the Purchaser
          -----------------
all of the following documents:

          (a)  an Officer's Certificate, dated the date of the Closing executed
by the President of the Company with respect to the representations and
warranties set forth in Article II of this Agreement and the due performance and
satisfaction of the obligations and conditions hereunder to be performed and
satisfied by the Company;

          (b)  certified copies of the resolutions duly adopted by the Company's
board of directors (the "Board") authorizing the execution, delivery and
performance of this Agreement, the filing of the Amended Charter, the issuance
and sale of the Series A Preferred Stock, the reservation for issuance upon
conversion of the Series A Preferred Stock of an aggregate of 800,000 shares of
Common Stock and the consummation of all other transactions contemplated by this
Agreement;

          (c)  certified copies of the Amended Charter and the Company's by-
laws, each as in effect at the Closing and a certificate as to the good standing
of the Company in the state of its formation and each state where the Company is
required to be qualified as a foreign corporation; and

          (d)  such other documents relating to the transactions contemplated by
this Agreement as the Purchaser or its counsel may reasonably request.

     4.8  No Claims.  No claim, action, suit, investigation or proceeding shall
          ---------
be pending or threatened by any Person or Persons against any of the parties
hereto or any of their respective affiliates which, if adversely determined,
could (a) prevent, hinder or enjoin consummation of the transactions
contemplated by this Agreement or the Additional Agreements or (b) materially
and adversely affect the business of the Company.  No party to this Agreement
shall have received written notice from any Governmental Entity of its intention
to (i) institute any action or proceeding to restrain, enjoin, nullify or render
ineffective this Agreement or any Additional Agreement or the transactions
contemplated hereby or thereby or (ii) commence any investigation into the
consummation of this Agreement or any Additional Agreement or the transactions
contemplated hereby or thereby, which, in the reasonable opinion of the
Purchaser, would make it inadvisable to consummate any such transactions.

                                      -7-
<PAGE>

                                   ARTICLE V

                 CONDITIONS TO THE OBLIGATIONS OF THE COMPANY

          The obligations of the Company under this Agreement to issue and
deliver Shares to the Purchaser are subject to the satisfaction, on or prior to
the Closing Date, of the following conditions, any of which may be waived in
whole or in part by the Company:

     5.1  Due Performance.  Such Purchaser shall have fully performed and
          ---------------
complied with all agreements and conditions required by this Agreement to be
performed or complied with by it on or prior to the Closing Date.

     5.2  Accuracy of Representations and Warranties.  All representations and
          ------------------------------------------
warranties of such Purchaser set forth in this Agreement shall be true and
correct on and as of the Closing Date in all respects, as though made on and as
of the Closing Date.

     5.3  Certificate.  The Company shall have received a certificate executed
          -----------
by an officer of the Purchaser with respect to the representations and
warranties of the Purchaser set forth in this Agreement and the due performance
and satisfaction of the obligations and conditions hereunder to be performed and
satisfied by the Purchaser.

     5.4  License Agreement.  The Perkin-Elmer Corporation shall have executed
          -----------------
and delivered the License Agreement.

     5.5  Consulting Agreement. The Perkin-Elmer Corporation shall have executed
          --------------------
and delivered the Consulting Agreement.

     5.6  No Claims.  No claim, action, suit, investigation or proceeding shall
          ---------
be pending or threatened by any Person or Persons against any of the parties
hereto which, if adversely determined, would (a) prevent or hinder consummation
of the transactions contemplated by this Agreement or any Additional Agreement,
or (b) result in the payment by the Company of substantial damages as a result
of the transactions contemplated hereby or thereby which would materially and
adversely affect the business of the Company.  No party to this Agreement shall
have received written notice from any Governmental Entity of its intention to
(i) institute any action or proceeding to restrain, enjoin, nullify or render
ineffective this Agreement or any Additional Agreement or the transactions
contemplated hereby or thereby or (ii) commence any investigation into the
consummation of this Agreement or any Additional Agreement or the transactions
contemplated hereby or thereby, which, in the reasonable opinion of the Company,
would make it inadvisable to consummate any such transactions.

                                  ARTICLE VI

                             AFFIRMATIVE COVENANTS

     6.1  Meetings of the Board of Directors.
          ----------------------------------

          (a)  The Company covenants and agrees that so long as the Purchaser
shall continue to hold at least 500 shares of Series A Preferred Stock, the
Purchaser shall have the right to designate a representative reasonably
acceptable to the Company to attend and observe

                                      -8-
<PAGE>

each meeting of the Board of the Company and its committees (the "Observer").
                                                                  --------
The Company shall also provide to the Observer a copy of all notices and other
written materials prepared for and provided to the Board of the Company at the
same time and in the same manner as such notices and written materials are
provided to members of the Board. Notwithstanding the foregoing, the Company
shall be entitled to (x) withhold from the Observer any confidential written
materials dealing with commercial matters involving the Purchaser, and (y)
exclude the Observer from any portion of any meeting of the Board of Directors
dealing with commercial matters involving the Purchaser. The rights provided to
the Purchaser herein are personal to the Purchaser and are not transferable in
connection with a sale of all or any portion of the Series A Preferred Stock.

          (b)  The Purchaser shall, and shall cause its Affiliates, officers,
directors, employees, agents and representatives to, keep secret and not divulge
to any third party or otherwise use for the Purchaser's benefit (other than in
connection with the transactions contemplated by this Agreement) any
confidential or proprietary information of the Company to which the Purchaser
obtains access pursuant to this Section 6.1; provided, however, that such
                                             --------  -------
obligation shall not apply to any information to the extent that (a) it is or
becomes part of public or industry knowledge or literature as a result of causes
other than the acts or omissions of the Purchaser or its Affiliates, officers,
directors, employees, agents or representatives, (b) can be demonstrated to have
been known to the Purchaser prior to its receipt from the Company, (c) is
received by the Purchaser in good faith from a third party or (d) can be
demonstrated to have been independently developed by the Purchaser.

     6.2  Reservation of Common Stock.  The Company shall at all times reserve
          ---------------------------
and keep available out of its authorized but unissued shares of Common Stock,
solely for the purpose of issuance upon the conversion of the Series A Preferred
Stock, such number of shares of Common Stock issuable upon the conversion of all
outstanding Series A Preferred Stock. All shares of Common Stock which are so
issuable shall, when issued, be duly and validly issued, fully paid and non-
assessable and free from all taxes, liens and charges. The Company shall take
all such actions as may be necessary to assure that all such shares of Common
Stock may be so issued without violation of any applicable law or governmental
regulation or any requirements of any domestic securities exchange upon which
shares of Common Stock may be listed (except for official notice of issuance
which shall be immediately transmitted by the Company upon issuance).

     6.3  Filing of Reports with the SEC.  With a view to making available to
          ------------------------------
the Purchaser the benefits of Rule 144 and any other rule or regulation of the
SEC that may at any time permit the Purchaser to sell securities of the Company
to the public without registration or pursuant to a registration on Form S-3,
the Company agrees to (a) use its best efforts to file with the SEC in a timely
manner all reports and other documents required of the Company under the
Securities Act and the Exchange Act and (b) furnish to the Purchaser, so long as
it owns any Shares or Common Stock issued upon conversion of the Shares,
forthwith upon request (i) a written statement that it has complied with the
reporting requirements of Rule 144, the Securities Act and the Exchange Act, or
that it qualifies as a registrant whose securities may be resold pursuant to
Form S-3, (ii) a copy of the most recent annual or quarterly report of the
Company and such other reports and documents so filed by the Company and (iii)
such other information as may be reasonably requested in availing the Purchaser
of any rule or regulation of the SEC that permits the selling of any such
securities without registration or pursuant to such Form S-3.

                                      -9-
<PAGE>

     6.4  Delivery of Stockholder Information.  The Company covenants and agrees
          -----------------------------------
that so long as the Purchaser shall hold any shares of Series A Preferred Stock,
the Company shall furnish to the Purchaser a copy of all notices of stockholder
meetings and other written materials prepared for and provided to holders of its
Common Stock at the same time and in the same manner as such notices and written
materials are provided to holders of its Common Stock.

                                  ARTICLE VII

                                    TRANSFER

     7.1  General Restrictions on Transfer.
          --------------------------------

          (a)  The Purchaser shall not directly or indirectly effect a Transfer
of any Restricted Shares owned or held by it unless (i) such Transfer is
consummated after compliance with the provisions of Section 7.1(b) and Section
7.2 hereof, and (ii) the certificate or certificates representing such
Restricted Shares bear a legend as provided in, and subject to, Section 7.3
hereof.

          (b)  The Purchaser shall not directly or indirectly effect a Transfer
of any Restricted Shares owned or held by it if such action would constitute a
violation of any federal securities laws or any state securities or blue sky
laws. In connection with any Transfer of Restricted Shares not effected through
a Public Sale, the Purchaser shall deliver to the Company a written opinion of
counsel reasonably acceptable to the Company (it being understood that the
General Counsel of the Purchaser is acceptable to the Company), in form and
substance reasonably satisfactory to the Company, to the effect that the
transfer of such Shares is exempt from registration under the Securities Act and
applicable state securities laws.

          (c)  The Company shall refuse to record in its stock transfer books a
Transfer by the Purchaser of any Restricted Shares that are not effected in
compliance with this Agreement, and any such attempted Transfer shall be null
and void.

     7.2  First Offer Right. At least 14 calendar days prior to making any
          -----------------
Transfer of any Restricted Stock (other than in a Public Sale or a Transfer to
an Affiliate of the Purchaser), the Purchaser shall deliver a written notice (an
"Offer Notice") to the Company, which shall disclose in reasonable detail the
proposed number of shares of Restricted Stock to be transferred (the "Offered
Stock"), the proposed terms and conditions of the Transfer and the identity of
the prospective transferee(s) (if any). The Company may elect to purchase all
(but not less than all) of the Offered Stock specified in the Offer Notice at
the price and on the terms specified therein by delivering written notice of
such election (the "Election Notice") to the Purchaser as soon as practical but
in any event within ten calendar days after the delivery of the Offer Notice
(the "Election Notice Deadline"). If the Company has elected to purchase all
(but not less than all) Offered Stock from the Purchaser, the purchase of the
Offered Stock shall be consummated as soon as practical but not later than 15
calendar days after the delivery of the Election Notice to the Purchaser. If the
Company elects not to purchase all of the Offered Stock, the Purchaser may, for
a period of 60 days after the Election Notice Deadline, transfer such Offered
Stock to one or more third parties at a price no less than the price per share
specified in the Offer Notice and on other terms no more favorable to the
transferees thereof than offered to the Company. Any Offered Stock not
transferred within such 60 day period shall be re-offered to the Company under
this Section 7.2 above prior to any subsequent Transfer.

                                      -10-
<PAGE>

     7.3  Legend.
          ------

          (a)  A copy of this Agreement shall be filed with the permanent
records of the Company and shall be kept at all times at the principal place of
business of the Company. The Purchaser agrees that all certificates representing
shares of Restricted Stock shall have affixed thereto a legend substantially in
the following form:

     "THE SHARES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED
     UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"), OR ANY
     STATE SECURITIES LAWS AND MAY NOT BE OFFERED, SOLD, TRANSFERRED OR
     OTHERWISE DISPOSED OF OR PLEDGED OR HYPOTHECATED UNLESS REGISTERED
     UNDER THE ACT AND ANY APPLICABLE STATE SECURITIES LAWS OR UNLESS AN
     EXEMPTION FROM REGISTRATION UNDER THE ACT AND ANY SUCH LAWS IS
     AVAILABLE (AND, IN SUCH CASE, AN OPINION OF COUNSEL REASONABLY
     ACCEPTABLE TO THE COMPANY, IN FORM AND SUBSTANCE REASONABLY
     SATISFACTORY TO THE COMPANY, SHALL HAVE BEEN DELIVERED TO THE COMPANY
     TO THE EFFECT THAT THE OFFER, SALE, TRANSFER, DISPOSITION, PLEDGE OR
     HYPOTHECATION THEREOF IS EXEMPT FROM REGISTRATION UNDER THE ACT AND
     ANY SUCH LAWS)."

          (b)  Notwithstanding the foregoing, the legend contained in this
Section 7.3 may be removed from a certificate upon receipt by the Company of a
written opinion of counsel reasonably acceptable to the Company (it being
understood that the General Counsel of the Purchaser is acceptable to the
Company), in form and substance reasonably satisfactory to the Company, to the
effect that such legend is no longer required under the Securities Act and
applicable state securities laws.

                                 ARTICLE VIII

                                 MISCELLANEOUS

     8.1  Survival of Representations, Warranties and Agreements.  All
          ------------------------------------------------------
representations and warranties and statements made by the Company in this
Agreement or in any document or certificate delivered pursuant hereto shall
survive the Closing Date for a period of one year.

     8.2  Expenses.  Each party shall bear its own fees and expenses in
          --------
connection with consummating the transactions contemplated hereby.

     8.3  Notice.  All communications, notices, requests, consents or demands
          ------
given or required under this Agreement shall be in writing and shall be
delivered personally or sent by facsimile or by a nationally recognized
overnight courier, and shall be deemed to have been duly given when so delivered
personally or sent by facsimile, with receipt confirmed, or one business day
after the date of deposit with such nationally recognized overnight courier. All
such communications, notices, requests, consents or demands shall be addressed
to the party for whom intended, as follows, or to such other address or
facsimile number as may be furnished by such party by notice in the manner
provided herein:

                                      -11-
<PAGE>

          If to the Company:

               SpectruMedix Corporation
               2124 Old Gatesburg Road
               State College, Pennsylvania  16803
               Attention:  Dr. Joseph Adlerstein
               Tel:  (814) 867-8600
               Fax: (814) 867-4513

          with a copy to:

               McDermott, Will & Emery
               50 Rockefeller Plaza
               New York, New York  10020
               Attention:  Stephen B. Selbst
               Tel.: (212) 547-5362
               Fax: (212) 547-5444

          If to Purchaser:

               PE Corporation
               761 Main Avenue
               Norwalk, CT  06859-0313
               Attention:  Secretary
               Tel.:  (203) 762-1000
               Fax: (203) 761-5000

     8.4  Entire Agreement.  This Agreement and the schedules and the exhibits
          ----------------
thereto, sets forth the entire understanding of the parties hereto with respect
to its subject matter, merges and supersedes all prior and contemporaneous
understandings with respect to its subject matter and may not be waived or
modified, in whole or in part, except by a writing signed by each of the parties
hereto.  No waiver of any provision of this Agreement in any instance shall be
deemed to be a waiver of the same or any other provision in any other instance.
Failure of any party to enforce any provision of this Agreement shall not be
construed as a waiver of its rights under such provision.

     8.5  Successors and Assigns.  This Agreement shall be binding upon,
          ----------------------
enforceable against and inure to the benefit of, the parties hereto and their
respective heirs, administrators, executors, personal representatives,
successors and assigns, and nothing herein is intended to confer any right,
remedy or benefit upon any other Person.

     8.6  Governing Law; Submission to Jurisdiction. This Agreement shall in all
          -----------------------------------------
respects be governed by and construed in accordance with the laws of the State
of New York applicable to agreements made and fully to be performed in such
state, without giving effect to conflicts of law rules or provisions (whether of
the State of New York or any other jurisdiction) that would cause the
application of the laws of any jurisdiction other than the State of New York.
The parties hereto agree to submit to the jurisdiction of the state and federal
courts in the State of New York with respect to any claim or matter arising
under this Agreement, and hereby consent

                                      -12-
<PAGE>

that service of process with respect to all courts in and of the State of New
York may be made by registered mail to such Person at the address of such Person
set forth herein.

     8.7  Counterparts. This Agreement may be executed in multiple counterparts,
          ------------
each of which shall be deemed an original, but all of which together shall
constitute one and the same instrument.

     8.8  Construction. Headings contained in this Agreement are for convenience
          ------------
only and shall not be used in the interpretation of this Agreement.  References
herein to Articles, sections and exhibits are to the articles, sections and
exhibits, respectively, of this Agreement.  The schedules are hereby
incorporated herein by reference and made a part of this Agreement.  As used
herein, the singular includes the plural, and the masculine, feminine and neuter
gender each includes the others where the context so indicates.

     8.9  Severability. If any provision of this Agreement is held to be invalid
          ------------
or unenforceable by a court of competent jurisdiction, this Agreement shall be
interpreted and enforceable as if such provision were severed or limited, but
only to the extent necessary to render such provision and this Agreement
enforceable.

                                  ARTICLE IX

                                  DEFINITIONS
     9.1  Defined Terms.  As used in this Agreement, and unless the context
          -------------
requires a different meaning, the following terms have the meanings indicated:

          "Additional Agreements" shall mean the License Agreement and the
Consulting Agreement.

          "Affiliate" of any particular Person means any other Person
controlling, controlled by or under common control with such particular Person,
where "control" means the possession, directly or indirectly, of the power to
direct the management and policies of a Person whether through the ownership of
voting securities, contract or otherwise.

          "Agreement" shall mean this Stock Purchase Agreement, as the same may
be amended, supplemented or modified in accordance with the terms hereof.

          "Amended Charter" shall have the meaning given such term in Section
4.3(c).

          "Closing" shall have the meaning given such term in Section 1.3.

          "Closing Date" shall have the meaning given such term in Section 1.3.

          "Common Stock" shall mean common stock of the Company, par value
$.00115 per share.

          "Consulting Agreement" has the meaning given such term in the first
recital.

          "Exchange Act" means the Securities Exchange Act of 1934, as amended,
or any successor federal statute thereto.

                                      -13-
<PAGE>

          "License Agreement" has the meaning given such term in the first
recital.

          "Person" means an individual, a partnership, a corporation, a limited
liability company, an association, a joint stock company, a trust, a joint
venture, an unincorporated organization and a governmental entity or any
department, agency or political subdivision thereof.

          "Preferred Stock" has the meaning given such term in Section 2.3.

          "Public Sale" means any sale of Common Stock or Series A Preferred
Stock to the public pursuant to any offering registered under the Securities Act
or to the public through a broker, dealer or market maker pursuant to the
provisions of Rule 144 adopted under the Securities Act (or any similar or
analogous exemption).

          "Restricted Shares" has the meaning set forth in Section 3.6 hereof.

          "SEC" means the U.S. Securities and Exchange Commission.

          "Securities Act" means the Securities Act of 1933, as amended, or any
successor federal statute thereto.

          "Series A Preferred Stock" means the Series A Preferred Stock of the
Company, par value $.00115 per share.

          "Shares" shall have the meaning given such term in Section 1.1.

          "Transfer" means any sale, transfer, assignment, gift, exchange,
pledge, hypothecation, encumbrance or other disposition of any Restricted Shares
or any interest therein, whether voluntary or involuntary and regardless of the
nature or method thereof (other than an exchange, reclassification or other
conversion of Restricted Shares into cash, securities or other property pursuant
to a merger, consolidation or recapitalization of the Company).

                                      -14-
<PAGE>

          IN WITNESS WHEREOF, each of the parties hereto has executed this
Agreement as of the date first set forth above.

                                     COMPANY:

                                     SPECTRUMEDIX CORPORATION




                                     By: /s/ Joseph K. Adlerstein
                                         -------------------------------------
                                     Name:  Joseph Adlerstein
                                     Title:  President

                                     PE CORPORATION



                                     By: /s/ Michael W. Hunkapiller
                                         -------------------------------------
                                     Name:  Michael W. Hunkapiller
                                     Title:  Senior Vice President

                                      -15-