<PAGE>
 
                                                                     EXHIBIT 3.8

  AMENDED CERTIFICATE TO SET FORTH DESIGNATIONS, VOTING POWERS, PREFERENCES,
               LIMITATIONS, RESTRICTIONS, AND RELATIVE RIGHTS OF
                                        
              SERIES A 6% CUMULATIVE CONVERTIBLE PREFERRED STOCK,
                        $0.001 PAR VALUE PER SHARE, AND

              SERIES B 6% CUMULATIVE CONVERTIBLE PREFERRED STOCK,
                          $0.001 PAR VALUE PER SHARE



     It is hereby certified that:

     I.   The name of the corporation is ChemTrak Incorporated (the
"Corporation"), a Delaware corporation.

     II.  Set forth hereinafter in this Article II is a statement of the voting
powers, preferences, limitations, restrictions, and relative rights of shares of
Series A 6% Cumulative Convertible Preferred Stock hereinafter designated as
contained in a resolution of the Board of Directors of the Corporation pursuant
to a provision of the Certificate of Incorporation of the Corporation permitting
the issuance of said Series A 6% Cumulative Convertible Preferred Stock by
resolution of the Board of Directors:

     Series A 6% Cumulative Convertible Preferred Stock, $0.001 par value.

     1.   Designation: Number of Shares.  The Corporation shall have 2,000
          ------------------------------                                  
shares designated as Series A 6% Cumulative Convertible Preferred Stock, $0.001
par value, as part of the authorized class of preferred shares (the "Series A
Preferred Stock").  Each share of Series A Preferred Stock shall have a stated
value equal to $1,000 (as adjusted for any stock dividends combinations or
splits with respect to such shares) (the "Stated Value").

     2.   Dividends.
          ----------

          (a) The holders of outstanding shares of Series A Preferred Stock
shall be entitled to receive preferential dividends in cash out of any funds of
the Corporation legally available at the time for declaration of dividends
before any dividend or other distribution will be paid or declared and set apart
for payment on any shares of any Common Stock or other class of stock junior to
the Series A Preferred Stock (the Common Stock and such junior stock being
hereinafter collectively the "Junior Stock") at the rate of 6% simple interest
per annum on the Stated Value per share payable quarterly when as and if
declared; provided however that dividend payments may be made in the sole
discretion of the Board of Directors of the Corporation in additional fully paid
and non-assessable shares of Series A 
<PAGE>
 
Preferred Stock at a rate of one share of Series A Preferred Stock for each
$1,000 of such dividend not paid in cash, and the issuance of such additional
shares shall constitute full payment of such dividend.

          (b) The dividends on the Series A Preferred Stock at the rates
provided above shall be cumulative whether or not earned so that if at any time
full cumulative dividends at the rate aforesaid on all shares of the Series A
Preferred Stock then outstanding from the date from and after which dividends
thereon are cumulative to the end of the quarterly dividend period next
preceding such time shall not have been paid or declared and set apart for
payment, or if the full dividend on all such outstanding Series A Preferred
Stock for the then current dividend period shall not have been paid or declared
and set apart for payment, the amount of the deficiency shall be paid or
declared and set apart for payment (but without interest thereon) before any sum
shall be set apart for or applied by the Corporation or a subsidiary of the
Corporation to the purchase redemption or other acquisition of the Stock and
before any dividend or other distribution shall be paid or declared and set
apart for payment on any Junior Stock and before any sum shall be set aside for
or applied to the purchase, redemption or other acquisition of Junior Stock.

          (c) Dividends on all shares of the Series A Preferred Stock shall
begin to accrue and be cumulative from and after the date of issuance thereof.
A dividend period shall be deemed to commence on the day following a quarterly
dividend payment date herein specified and to end of the next succeeding
quarterly dividend payment date herein specified.

     3.   Liquidation Rights.
          -------------------

          (a) Upon the dissolution, liquidation or winding-up of the
Corporation, whether voluntary or involuntary, the holders of the Series A
Preferred Stock shall be entitled to receive before any payment or distribution
shall be made on the Junior Stock, out of the assets of the Corporation
available for distribution to stockholders, the Stated Value per share of Series
A Preferred Stock and all accrued and unpaid dividends to and including the date
of payment thereof.  Upon the payment in full of all amounts due to holders of
the Series A Preferred Stock then the holders of the Junior Stock of the
Corporation shall receive, ratably, all remaining assets of the Corporation
legally available for distribution.  If the assets of the Corporation available
for distribution to the holders of the Series A Preferred Stock shall be
insufficient to permit payment in full of the amounts payable as aforesaid to
the holders of Series A Preferred Stock upon such liquidation, dissolution or
winding-up, whether voluntary or involuntary, then all such assets of the
Corporation shall be distributed to the exclusion of the holders of shares of
Junior Stock ratably among the holders of Series A Preferred Stock.

          (b) Neither purchase nor the redemption by the Corporation of shares
of any class of stock nor the merger nor consolidation of the Corporation with
or into any other corporation or corporations nor the sale or transfer by the
Corporation of all or any part of its assets shall be deemed to be a
liquidation, dissolution or winding-up of the Corporation for the purposes of
this Section 3.

     4.   Conversion into Common Stock.  Shares of Series A Preferred Stock
          -----------------------------                                    
shall have the following conversion rights and obligations:

                                       2
<PAGE>
 
          (a) Subject to the further provisions of this Section 4, each holder
of shares of Series A Preferred Stock shall have the right at any time and from
time to time after sixty (60) days from the date on which a share of Series A
Preferred Stock was issued, to convert some or all such shares into fully paid
and non-assessable shares of Common Stock of the Corporation (as defined in
paragraph 4(i) below) determined in accordance with the Conversion Rate provided
in paragraph 4(b) below (the "Conversion Rate"); provided, that the aggregate
Stated Value to be converted shall be at least $25,000 (unless if at the time of
such conversion the aggregate Stated Value of all shares of Series A Preferred
Stock registered to the Holder is less than $25,000, then the whole amount may
be converted).

          (b) The number of shares of Common Stock issuable upon conversion of
each share of Series A Preferred Stock shall equal (i) the sum of (A) the Stated
Value per share and (B) accrued and unpaid dividends on such share, divided by
(ii) the Conversion Price.  The Conversion Price shall be equal to the lesser
of: (i) seventy-five percent (75%) of the average of the Closing Bid Price (as
hereinafter defined) of the Corporation's Common Stock for the five (5) trading
days immediately preceding the date of issuance of the Series A Preferred Stock;
or (ii) seventy-five percent (75%) of the average of the Closing Bid Price for
the five trading days immediately preceding conversion of the Series A Preferred
Stock.  The Closing Bid Price shall mean the closing bid price of the
Corporation's Common Stock as reported from the NASDAQ SmallCap Market (or if
not reported by NASDAQ as reported by such other exchange or market where
traded).

          (c) The holder of any certificate for shares of Series A Preferred
Stock desiring to convert any of such shares may give notice of its decision to
convert the shares into common stock by telecopying an executed and completed
notice of conversion to the Corporation and delivering within three business
days thereafter, the original notice of conversion and the certificate for the
Preferred Stock properly endorsed for or accompanied by duly executed
instruments of transfer (and such other transfer papers as said Transfer Agent
may reasonably require) to the Corporation.  Each date on which a notice of
conversion is telecopied to and received by the Corporation in accordance with
the provisions hereof shall be deemed a Conversion Date.  The Corporation will
transmit the certificates representing the shares of common stock issuable upon
conversion of any Preferred Stock (together with the Preferred Stock
representing the shares not converted) to the Holder via express courier, or
otherwise, for receipt by the holder within three business days after receipt by
the Corporation of the original notice of conversion and the Preferred Stock
representing the shares to be converted.  The holder of the shares so
surrendered for conversion shall be entitled to receive (except as otherwise
provided herein) a certificate or certificates which shall be expressed to be
fully paid and non-assessable for the number of shares of Common Stock to which
such stockholder shall be entitled upon such conversion registered in the name
of such holder or in such other name or names as such stockholder in writing may
specify.  In the case of any Series A Preferred Stock which is converted in part
only the holder of shares of Series A Preferred Stock shall upon delivery of the
certificate or certificates representing Common Stock also receive a new share
certificate representing the unconverted portion of the shares of Series A
Preferred Stock.  Nothing herein shall be construed to give any holder of Series
A Preferred Stock surrendering the same for conversion the right to receive any
additional shares of Common Stock or other property which results from an
adjustment in conversion rights under the provision of paragraph (d) or (e) of
this Section 4 until 

                                       3
<PAGE>
 
holders of Common Stock are entitled to receive the shares or other property
giving rise to the adjustment.

          In the case of the exercise of the conversion rights set forth in
paragraph 4(a) the conversion privilege shall be deemed to have been exercised
and the shares of Common Stock issuable upon such conversion shall be deemed to
have been issued upon the date of receipt by such Transfer Agent for conversion
of the certificate for such shares of Series A Preferred Stock.  The person or
entity entitled to receive Common Stock issuable upon such conversion shall, on
the date such conversion privilege is deemed to have been exercised and
thereafter, be treated for all purposes as the record holder of such Common
Stock and shall on the same date cease to be treated for any purpose as the
record holder of such shares of Series A Preferred Stock to be converted.

          Notwithstanding the foregoing, if the stock transfer books are closed
on the date such shares are received by the Transfer Agent, the conversion
privilege shall be deemed to have been exercised and the person or entity shall
be treated as a record holder of shares of Common Stock on the next succeeding
date on which the transfer books are open, but the Conversion Rate shall be that
in effect on the date such conversion privilege was exercised.  The Corporation
shall not be required to deliver certificates for shares of its Common Stock or
new certificates for unconverted shares of its Series A Preferred Stock while
the stock transfer books for such respective classes of stock are duly closed
for any purpose; but the right of surrendering shares of Series A Preferred
Stock for conversion shall not be suspended during any period that the stock
transfer books of either of such classes of stock are closed.

          Upon the conversion of any shares of Series A Preferred Stock no
adjustment or payment shall be made with respect to such converted shares on
account of any dividend on shares of such stock or on account of any dividend on
the Common Stock, except that the holder of such converted shares shall be
entitled to be paid any dividends declared on shares of Common Stock after
conversion thereof.

          The Corporation shall not be required in connection with any
conversion of Series A Preferred Stock to issue a fraction of a share of its
Common Stock nor to deliver any stock certificate representing a fraction
thereof.  For administrative efficiency and simplicity, in the event the number
of shares issuable to a shareholder results in a fractional share, said number
shall be rounded up to the next higher whole number of shares.  No cash shall be
paid for any fractional share.

          (d) The Conversion Rate shall be subject to adjustment from time to
time as follows:

              (i) In case the Corporation shall at any time (A) declare any
dividend or distribution on its Common Stock or other securities of the
Corporation other than the Series A Preferred Stock, (B) split or subdivide the
outstanding Common Stock, (C) combine the outstanding Common Stock into a
smaller number of shares, or (D) issue by reclassification of its Common Stock
any shares or other securities of the Corporation, then in each such event the
Conversion Rate shall be adjusted proportionately so that the holders of Series
A Preferred Stock shall be entitled to receive the kind and number of shares or
other securities of the Corporation which such holders would have owned or have
been entitled to receive after the happening of any of the events described
above had such shares of Series A Preferred Stock been converted immediately
prior to the happening of such event (or any record 

                                       4
<PAGE>
 
date with respect thereto). Such adjustment shall be made whenever any of the
events listed above shall occur. An adjustment made to the Conversion pursuant
to this paragraph 4(d)(i) shall become effective immediately after the effective
date of the event retroactive to the record date, if any, for the event.

          (e) The Conversion Rate shall also be subject to adjustment from time
to time as follows:

              (i) In case of any merger of the Corporation with or into any
other corporation (other than a merger in which the Corporation is the surviving
or continuing corporation and which does not result in any reclassification,
conversion, or change of the outstanding shares of Common Stock) then as part of
such merger lawful provision shall be made so that holders of Series A Preferred
Stock shall thereafter have the right to convert each share of Series A
Preferred Stock into the kind and amount of shares of stock and/or other
securities or property receivable upon such merger by a holder of the number of
shares of Common Stock into which such shares of Series A Preferred Stock might
have been converted immediately prior to such consolidation or merger. Such
provision shall also provide for adjustments which shall be as nearly equivalent
as may be practicable to the adjustments provided for in paragraph (d) of this
Section 4. The foregoing provisions of this paragraph 4(e) shall similarly apply
to successive mergers.

              (ii) In case of any sale or conveyance to another person or entity
of the property of the Corporation as an entirety, or substantially as an
entirety, in connection with which shares or other securities or cash or other
property shall be issuable, distributable, payable, or deliverable for
outstanding shares of Common Stock, then, unless the right to convert such
shares shall have terminated, lawful provision shall be made so that the holders
of Series A Preferred Stock shall thereafter have the right to convert each
share of the Series A Preferred Stock into the kind and amount of shares of
stock or other securities or property that shall be issuable, distributable,
payable, or deliverable upon such sale or conveyance with respect to each share
of Common Stock immediately prior to such conveyance.

          (f) Subject to the provisions of this section, if the Corporation at
any time shall issue any shares of Common Stock prior to the conversion of the
entire Stated Value of the Series A Preferred Stock (otherwise than as: (i)
provided in paragraphs (d) and (e) of this Section 4; or (ii) pursuant to
options, warrants, or other obligations to issue shares, outstanding on the date
hereof as described in public filings made by the Corporation prior to the date
hereof with the Securities and Exchange Commission including all shares reserved
for issuance pursuant to the Corporation's existing option and stock plans ((i)
and (ii) above, are hereinafter referred to as the "Existing Option
Obligations") for a consideration less than the Conversion Price that would be
in effect at the time of such issue, then, and thereafter successively upon each
such issue, the Conversion Price shall be reduced as follows: (i) the number of
shares of Common Stock outstanding immediately prior to such issue shall be
multiplied by the Conversion Price in effect at the time of such issue and the
product shall be added to the aggregate consideration, if any, received by the
Corporation upon such issue of additional shares of Common Stock; and (ii) the
sum so obtained shall be divided by the number of shares of Common Stock
outstanding immediately after such issue. Except for the Existing Option
Obligations and options that may be issued under any employee incentive stock
option and/or any qualified stock option plan adopted 

                                       5
<PAGE>
 
by the Company, for purposes of this adjustment, the issuance of any security of
the Corporation carrying the right to convert such security into shares of
Common Stock or of any warrant, right or option to purchase Common Stock shall
result in an adjustment to the Conversion Price upon the issuance of shares of
Common Stock upon exercise of such conversion or purchase rights.

          (g) Whenever the number of shares to be issued upon conversion of the
Series A Preferred Stock is required to be adjusted as provided in this Section
4, the Corporation shall forthwith compute the adjusted number of shares to be
so issued and prepare a certificate setting forth such adjusted conversion
amount and the facts upon which such adjustment is based, and such certificate
shall forthwith be filed with the Transfer Agent for the Series A Preferred
Stock and the Common Stock; and the Corporation shall mail to each holder of
record of Series A Preferred Stock notice of such adjusted conversion price.

          (h) In case at any time the Corporation shall propose:

              (i)   To pay any dividend or distribution payable in shares upon
its Common Stock or make any distribution (other than cash dividends) to the
holders of its Common Stock; or

              (ii)  To offer for subscription to the holders of its Common Stock
any additional shares of any class or any other rights; or

              (iii) Any capital reorganization or reclassification of its
shares or the merger of the Corporation with another corporation (other than a
merger in which the Corporation is the surviving or continuing corporation and
which does not result in any reclassification, conversion, or change of the
outstanding shares of Common Stock); or

              (iv) The voluntary dissolution, liquidation or winding-up of the
Corporation; then, and in any one of more of said cases, the Corporation shall
cause at least fifteen (15) days prior notice of the date on which (A) the books
of the Corporation shall close for such stock dividend, distribution, or
subscription rights, or (B) such capital reorganization, reclassification,
merger, dissolution, liquidation or winding-up shall take place, as the case may
be, to be mailed to the Transfer Agent for the Series A Preferred Stock and for
the Common Stock and to the holders of record of the Series A Preferred Stock.

          (i) So long as any shares of Series A Preferred Stock shall remain
outstanding and the holders thereof shall have the right to convert the same in
accordance with provisions of this Section 4 the Corporation shall at all times
reserve from the authorized and unissued shares of its Common Stock a sufficient
number of shares to provide for such conversions.


          (j) The term Common Stock as used in this Section 4 shall mean Common
Stock of the Corporation as such stock is constituted at the date of issuance
thereof or as it may from time to time be changed or shares of stock of any
class of other securities and/or property into which the shares of Series A
Preferred Stock shall at any time become convertible pursuant to the provisions
of this Section 4.

                                       6
<PAGE>
 
          (k) The Corporation shall pay the amount of any and all issue taxes
(but not income taxes) which may be imposed in respect of any issue or delivery
of stock upon the conversion of any shares of Series A Preferred Stock, but all
transfer taxes and income taxes that may be payable in respect of any change or
ownership of Series A Preferred Stock or any rights represented thereby or of
stock receivable upon conversion thereof shall be paid by the person or persons
surrendering such stock for conversion.

     5.   Mandatory Conversion/Redemption.
          --------------------------------

          (a) Subject to the provisions of paragraph 5(e) below, the shares of
Series A Preferred Stock not previously converted into shares of Common Stock
shall be converted into shares of Common Stock without further action of the
Holder on the date that is two years from the date of issuance thereof, at the
Conversion Price and on the conversion terms specified in paragraph 4(b).

          (b) Notice of conversion of Series A Preferred Stock by the
Corporation pursuant to this Section 5 shall be given by mail or in such other
manner as may be prescribed by resolution of the Board not less than thirty (30)
days prior to the applicable date of mandatory conversion (the "Mandatory
Conversion Date").  As applicable, the notice shall specify the number of shares
to be converted, the date fixed for conversion, and the conversion price per
share.

          (c) The holder of any certificate for shares of Series A Preferred
Stock that is converted pursuant to this Section 5 shall surrender such
certificate at the principal office of any transfer agent for said stock (the
"Transfer Agent") properly endorsed for or accompanied by duly executed
instruments of transfer (and such other transfer papers as said Transfer Agent
may reasonably require). The holder of the shares so surrendered for conversion
shall be entitled to receive (except as otherwise provided herein) a certificate
or certificates which shall be expressed to be fully paid and non-assessable for
the number of shares of Common Stock to which such stockholder shall be entitled
upon such conversion registered in the name of such holder or in such other name
or names as such stockholder in writing may specify.

          (d) On and after the applicable Mandatory Conversion Date (subject to
paragraph 5(e) below), and notwithstanding that any certificate for shares of
Series A Preferred Stock so called for conversion shall not have been
surrendered for cancellation, all dividends on the Series A Preferred Stock
called for conversion shall cease to accrue and the shares represented thereby
shall no longer be deemed outstanding and all rights of the holders thereof as
stockholders of the Corporation shall cease and terminate, except the right to
receive the shares of Common Stock upon conversion as provided herein.

          (e) In no event shall a Mandatory Conversion occur at any time unless
the Common Stock to be delivered upon conversion will be immediately upon
delivery and thereafter, unlegended, freely tradable, and freely transferable on
the transfer books of the Corporation.

                                       7
<PAGE>
 
          (f) The Corporation may elect to redeem all or part of the Stated
Value of the Preferred Stock upon payment of an amount of dollars equal to the
Stated Value of the Preferred Stock plus accrued but unpaid dividends and any
other sum payable in respect of the Series A Preferred Stock, multiplied by the
greater of: (i) the average of the Closing Bid Price (as herein defined) of the
Corporation's Common Stock for the five (5) trading days immediately preceding
the date of issuance of the Series A Preferred Stock; or (ii) the average of the
Closing Bid Price for the five trading days immediately preceding the date
notice of redemption is given to the Holder (the "Redemption Price"). The date
notice of redemption is given to the Holder is the Redemption Date. The
Corporation shall effect a Redemption by written notice to the Holder. The
Redemption Price must be paid by the Corporation to the Holder not sooner than
five business days, but not later than ten business days after such notice is
sent. The Corporation may not redeem any amount which the Holder has elected to
convert, including a notice of conversion given after the Redemption Date but
prior to receipt by the Holder of the Redemption Price. In the event the
Corporation gives written notice to affect a redemption, but fails to timely pay
the Redemption Price, then the Holder may elect to void the Redemption Notice.
After such failure, the Corporation will no longer have the right to affect any
Redemption. At the election of the Holder, such default shall be deemed an
additional Event of Default under Section 6 hereof.

     6.   Event of Default.  The occurrence of any of the following events of
          -----------------                                                  
default ("Event of Default") shall cause the dividend rate of 6% described in
Section 2 hereof to become 15% from and after the occurrence of such event, and
at the option of the Holder, the Series A Preferred Stock shall be redeemed by
the Corporation at its Stated Value and accrued dividends and the Holder may
rescind any unfilled Notice of Conversion:

          (a) The Corporation fails to pay any dividend payment required to be
paid pursuant to the terms of Section 2 hereof and such failure continues for a
period of ten (10) days.

          (b) The Corporation breaches any covenant or other term or condition
of the Subscription Agreement entered into between the Corporation and holder
relating to Series A Preferred Stock (the "Subscription Agreement") or in this
Certificate to Set Forth Designations, Voting Powers, Preferences, Limitations,
Restrictions, and Relative Rights of Series A 6% Cumulative Convertible
Preferred Stock, $0.001 Par Value Per Share, and such breach continues for a
period of seven (7) days after written notice to the Corporation from the
holder.

          (c) Any representation or warranty of the Corporation made in the
Subscription Agreement, or in any agreement, statement or certificate given in
writing pursuant thereto shall be false or misleading.

          (d) The Corporation shall make an assignment for the benefit of
creditors, or apply for or consent to the appointment of a receiver or trustee
for it or for a substantial part of its property or business; or such a receiver
or trustee shall otherwise be appointed.

          (e) Any money judgment, writ or similar process shall be entered or
filed against the Corporation or any of its property or other assets for more
than $100,000, and shall remain unvacated, unbonded or unstayed for a period of
forty-five (45) days.

                                       8
<PAGE>
 
          (f) Bankruptcy, insolvency, reorganization or liquidation proceedings
or other proceedings or relief under any bankruptcy law or any law for the
relief of debtors shall be instituted by or against the Corporation.

          (g) The delisting of the Common Stock from the NASDAQ SmallCap Market
or such other principal exchange on which the Common Stock is listed for
trading.
 
          (h) A concession by the Company of a default under any one or more
obligations in an aggregate monetary amount in excess of $100,000.

          (i) An SEC stop trade order or NASDAQ trading suspension, if either
applies for a period of ten days or longer.

          (j) The Corporation's failure to timely deliver Common Stock to the
holder pursuant to Section 4 hereof and Section 9 of the Subscription Agreement.

          (k) The occurrence of a Registration Default as described in Section
10.2(j) of the Subscription Agreement.

     7.   Voting Rights.  The shares of Series A Preferred Stock shall not have
          --------------                                                       
voting rights.

     8.   Status of Converted Stock.  In case any shares of Series A Preferred
          --------------------------                                          
Stock shall be converted pursuant to Section 4 hereof or otherwise repurchased
or reacquired, the shares so converted, or reacquired shall resume the status of
authorized but unissued shares of Preferred Stock and shall no longer be
designated as Series A Preferred Stock.

     9.   Additional Restrictions.  For as long as any shares of the Series A
          ------------------------                                           
Preferred Stock are outstanding, the Corporation will not issue any preferred
stock that is senior to the Series A Preferred Stock, and will not amend the
terms of the Series A Preferred Stock without the consent of the holders of the
Series A Preferred Stock.

     III. Set forth hereinafter in this Article III is a statement of the voting
powers, preferences, limitations, restrictions, and relative rights of shares of
Series B 6% Cumulative Convertible Preferred Stock hereinafter designated as
contained in a resolution of the Board of Directors of the Corporation pursuant
to a provision of the Certificate of Incorporation of the Corporation permitting
the issuance of said Series B 6% Cumulative Convertible Preferred Stock by
resolution of the Board of Directors:

     Series B 6% Cumulative Convertible Preferred Stock, $0.001 par value.

     1.   Designation: Number of Shares.  The Corporation shall have 3,000
          ------------------------------                                  
shares designated as Series B 6% Cumulative Convertible Preferred Stock, $0.001
par value, as part of the authorized class of preferred shares (the "Series B
Preferred Stock").  Each share of Series B Preferred Stock shall have 

                                       9
<PAGE>
 
a stated value equal to $1,000 (as adjusted for any stock dividends combinations
or splits with respect to such shares) (the "Stated Value").

     2.   Dividends.
          ----------

          (a) The holders of outstanding shares of Series B Preferred Stock
shall be entitled to receive preferential dividends pari passu with the holders
of outstanding shares of Series A Preferred Stock, in cash out of any funds of
the Corporation legally available at the time for declaration of dividends
before any dividend or other distribution will be paid or declared and set apart
for payment on any shares of any Junior Stock at the rate of 6% simple interest
per annum on the Stated Value per share payable quarterly when as and if
declared; provided however that dividend payments may be made in the sole
discretion of the Board of Directors of the Corporation in additional fully paid
and non-assessable shares of Series B Preferred Stock at a rate of one share of
Series B Preferred Stock for each $1,000 of such dividend not paid in cash, and
the issuance of such additional shares shall constitute full payment of such
dividend.

          (b) The dividends on the Series B Preferred Stock at the rates
provided above shall be cumulative whether or not earned so that if at any time
full cumulative dividends at the rate aforesaid on all shares of the Series B
Preferred Stock then outstanding from the date from and after which dividends
thereon are cumulative to the end of the quarterly dividend period next
preceding such time shall not have been paid or declared and set apart for
payment, or if the full dividend on all such outstanding Series B Preferred
Stock for the then current dividend period shall not have been paid or declared
and set apart for payment, the amount of the deficiency shall be paid or
declared and set apart for payment (but without interest thereon) before any sum
shall be set apart for or applied by the Corporation or a subsidiary of the
Corporation to the purchase redemption or other acquisition of the Stock and
before any dividend or other distribution shall be paid or declared and set
apart for payment on any Junior Stock and before any sum shall be set aside for
or applied to the purchase, redemption or other acquisition of Junior Stock.

          (c) Dividends on all shares of the Series B Preferred Stock shall
begin to accrue and be cumulative from and after the date of issuance thereof.
A dividend period shall be deemed to commence on the day following a quarterly
dividend payment date herein specified and to end of the next succeeding
quarterly dividend payment date herein specified.


     3.   Liquidation Rights.
          -------------------

          (a) Upon the dissolution, liquidation or winding-up of the
Corporation, whether voluntary or involuntary, the holders of the Series B
Preferred Stock shall be entitled to receive before any payment or distribution
shall be made on the Junior Stock, out of the assets of the Corporation
available for distribution to stockholders, the Stated Value per share of Series
B Preferred Stock and all accrued and unpaid dividends to and including the date
of payment thereof.  Upon the payment in full of all amounts due to holders of
the Series B 

                                       10
<PAGE>
 
Preferred Stock then the holders of the Junior Stock of the Corporation shall
receive, ratably, all remaining assets of the Corporation legally available for
distribution. If the assets of the Corporation available for distribution to the
holders of the Series B Preferred Stock shall be insufficient to permit payment
in full of the amounts payable as aforesaid to the holders of Series B Preferred
Stock upon such liquidation, dissolution or winding-up, whether voluntary or
involuntary, then all such assets of the Corporation shall be distributed to the
exclusion of the holders of shares of Junior Stock ratably among the holders of
Series B Preferred Stock.

          (b) Neither purchase nor the redemption by the Corporation of shares
of any class of stock nor the merger nor consolidation of the Corporation with
or into any other corporation or corporations nor the sale or transfer by the
Corporation of all or any part of its assets shall be deemed to be a
liquidation, dissolution or winding-up of the Corporation for the purposes of
this Section 3.

     4.   Conversion into Common Stock.  Shares of Series B Preferred Stock
          -----------------------------                                    
shall have the following conversion rights and obligations:

          (a) Subject to the further provisions of this Section 4, each holder
of shares of Series B Preferred Stock shall have the right at any time and from
time to time after ninety (90) days from the date on which a share of Series B
Preferred Stock was issued, to convert some or all such shares into fully paid
and non-assessable shares of Common Stock of the Corporation (as defined in
paragraph 4(i) below) determined in accordance with the Conversion Rate provided
in paragraph 4(b) below (the "Conversion Rate"); provided, that the aggregate
Stated Value to be converted shall be at least $25,000 (unless if at the time of
such conversion the aggregate Stated Value of all shares of Series B Preferred
Stock registered to the Holder is less than $25,000, then the whole amount may
be converted).

          (b) Each share of Series B Preferred Stock shall have a stated value
equal to $1,000 (as adjusted for any stock combinations or splits with respect
to such shares) (the "Stated Value").  The Company may elect to redeem all of
part of the Series B Preferred Stock upon payment of the Stated Value (plus any
dividends accumulated thereon) multiplied by 1.333 (the "Redemption Price") to
the Holders for each share to be redeemed.  The date notice of redemption is
given to the Holder is the Redemption Date.  The Company shall effect a
Redemption by written notice to the Holder.  The Redemption Price must be paid
by the Company to the Holder not sooner than five business days, but not later
than ten business days after such notice is sent.  The Company may not redeem
any amount that the Holder has elected to convert, including a notice of
conversion given after the Redemption Date but prior to receipt by the Holder of
the Redemption Price.  In the event the Company gives written notice to affect a
redemption, but fails to timely pay the Redemption Price, then the Holder may
elect to avoid the Redemption Notice.  After such failure, the Company will no
longer have the right to affect any Redemption.

          (c) The holder of any certificate for shares of Series B Preferred
Stock desiring to convert any of such shares may give notice of its decision to
convert the shares into common stock by telecopying an executed and completed
notice of conversion to the Corporation and delivering within three business
days thereafter, the original notice of conversion and the certificate for the
Preferred Stock properly endorsed for or accompanied by duly executed
instruments of transfer (and such other transfer papers as said Transfer Agent
may reasonably require) to the Corporation.  Each date on which a notice of
conversion is telecopied to and received by the Corporation in accordance with
the provisions hereof 

                                       11
<PAGE>
 
shall be deemed a Conversion Date. The Corporation will transmit the
certificates representing the shares of common stock issuable upon conversion of
any Preferred Stock (together with the Preferred Stock representing the shares
not converted) to the Holder via express courier, or otherwise, for receipt by
the holder within three business days after receipt by the Corporation of the
original notice of conversion and the Preferred Stock representing the shares to
be converted. The holder of the shares so surrendered for conversion shall be
entitled to receive (except as otherwise provided herein) a certificate or
certificates which shall be expressed to be fully paid and non-assessable for
the number of shares of Common Stock to which such stockholder shall be entitled
upon such conversion registered in the name of such holder or in such other name
or names as such stockholder in writing may specify. In the case of any Series B
Preferred Stock which is converted in part only the holder of shares of Series B
Preferred Stock shall upon delivery of the certificate or certificates
representing Common Stock also receive a new share certificate representing the
unconverted portion of the shares of Series B Preferred Stock. Nothing herein
shall be construed to give any holder of Series B Preferred Stock surrendering
the same for conversion the right to receive any additional shares of Common
Stock or other property which results from an adjustment in conversion rights
under the provision of paragraph (d) or (e) of this Section 4 until holders of
Common Stock are entitled to receive the shares or other property giving rise to
the adjustment.

          In the case of the exercise of the conversion rights set forth in
paragraph 4(a) the conversion privilege shall be deemed to have been exercised
and the shares of Common Stock issuable upon such conversion shall be deemed to
have been issued upon the date of receipt by such Transfer Agent for conversion
of the certificate for such shares of Series B Preferred Stock.  The person or
entity entitled to receive Common Stock issuable upon such conversion shall, on
the date such conversion privilege is deemed to have been exercised and
thereafter, be treated for all purposes as the record holder of such Common
Stock and shall on the same date cease to be treated for any purpose as the
record holder of such shares of Series B Preferred Stock to be converted.

          Notwithstanding the foregoing, if the stock transfer books are closed
on the date such shares are received by the Transfer Agent, the conversion
privilege shall be deemed to have been exercised and the person or entity shall
be treated as a record holder of shares of Common Stock on the next succeeding
date on which the transfer books are open, but the Conversion Rate shall be that
in effect on the date such conversion privilege was exercised.  The Corporation
shall not be required to deliver certificates for shares of its Common Stock or
new certificates for unconverted shares of its Series B Preferred Stock while
the stock transfer books for such respective classes of stock are duly closed
for any purpose; but the right of surrendering shares of Series B Preferred
Stock for conversion shall not be suspended during any period that the stock
transfer books of either of such classes of stock are closed.

          Upon the conversion of any shares of Series B Preferred Stock no
adjustment or payment shall be made with respect to such converted shares on
account of any dividend on shares of such stock or on account of any dividend on
the Common Stock, except that the holder of such converted shares shall be
entitled to be paid any dividends declared on shares of Common Stock after
conversion thereof.

          The Corporation shall not be required in connection with any
conversion of Series B Preferred Stock to issue a fraction of a share of its
Common Stock nor to deliver any stock certificate 

                                       12
<PAGE>
 
representing a fraction thereof. For administrative efficiency and simplicity,
in the event the number of shares issuable to a shareholder results in a
fractional share, said number shall be rounded up to the next higher whole
number of shares. No cash shall be paid for any fractional share.

          (d) The Conversion Rate shall be subject to adjustment from time to
time as follows:

              (i) In case the Corporation shall at any time (A) declare any
dividend or distribution on its Common Stock or other securities of the
Corporation other than the Series B Preferred Stock, (B) split or subdivide the
outstanding Common Stock, (C) combine the outstanding Common Stock into a
smaller number of shares, or (D) issue by reclassification of its Common Stock
any shares or other securities of the Corporation, then in each such event the
Conversion Rate shall be adjusted proportionately so that the holders of Series
B Preferred Stock shall be entitled to receive the kind and number of shares or
other securities of the Corporation which such holders would have owned or have
been entitled to receive after the happening of any of the events described
above had such shares of Series B Preferred Stock been converted immediately
prior to the happening of such event (or any record date with respect thereto).
Such adjustment shall be made whenever any of the events listed above shall
occur. An adjustment made to the Conversion pursuant to this paragraph 4(d)(i)
shall become effective immediately after the effective date of the event
retroactive to the record date, if any, for the event.

          (e) The Conversion Rate shall also be subject to adjustment from time
to time as follows:

              (i) In case of any merger of the Corporation with or into any
other corporation (other than a merger in which the Corporation is the surviving
or continuing corporation and which does not result in any reclassification,
conversion, or change of the outstanding shares of Common Stock) then as part of
such merger lawful provision shall be made so that holders of Series B Preferred
Stock shall thereafter have the right to convert each share of Series B
Preferred Stock into the kind and amount of shares of stock and/or other
securities or property receivable upon such merger by a holder of the number of
shares of Common Stock into which such shares of Series B Preferred Stock might
have been converted immediately prior to such consolidation or merger. Such
provision shall also provide for adjustments which shall be as nearly equivalent
as may be practicable to the adjustments provided for in paragraph (d) of this
Section 4. The foregoing provisions of this paragraph 4(e) shall similarly apply
to successive mergers.

              (ii) In case of any sale or conveyance to another person or entity
of the property of the Corporation as an entirety, or substantially as an
entirety, in connection with which shares or other securities or cash or other
property shall be issuable, distributable, payable, or deliverable for
outstanding shares of Common Stock, then, unless the right to convert such
shares shall have terminated, lawful provision shall be made so that the holders
of Series B Preferred Stock shall thereafter have the right to convert each
share of the Series B Preferred Stock into the kind and amount of shares of
stock or other securities or property that shall be issuable, distributable,
payable, or deliverable upon such sale or conveyance with respect to each share
of Common Stock immediately prior to such conveyance.

                                       13
<PAGE>
 
          (f) Subject to the provisions of this section, if the Corporation at
any time shall issue any shares of Common Stock prior to the conversion of the
entire Stated Value of the Series B Preferred Stock (otherwise than as: (i)
provided in paragraphs (d) and (e) of this Section 4; or (ii) pursuant to
options, warrants, or other obligations to issue shares, outstanding on the date
hereof as described in public filings made by the Corporation prior to the date
hereof with the Securities and Exchange Commission including all shares reserved
for issuance pursuant to the Corporation's existing option and stock plans ((i)
and (ii) above, are hereinafter referred to as the "Existing Option
Obligations") for a consideration less than the Conversion Price that would be
in effect at the time of such issue, then, and thereafter successively upon each
such issue, the Conversion Price shall be reduced as follows: (i) the number of
shares of Common Stock outstanding immediately prior to such issue shall be
multiplied by the Conversion Price in effect at the time of such issue and the
product shall be added to the aggregate consideration, if any, received by the
Corporation upon such issue of additional shares of Common Stock; and (ii) the
sum so obtained shall be divided by the number of shares of Common Stock
outstanding immediately after such issue.  Except for the Existing Option
Obligations and options that may be issued under any employee incentive stock
option and/or any qualified stock option plan adopted by the Company, for
purposes of this adjustment, the issuance of any security of the Corporation
carrying the right to convert such security into shares of Common Stock or of
any warrant, right or option to purchase Common Stock shall result in an
adjustment to the Conversion Price upon the issuance of shares of Common Stock
upon exercise of such conversion or purchase rights.

          (g) Whenever the number of shares to be issued upon conversion of the
Series B Preferred Stock is required to be adjusted as provided in this Section
4, the Corporation shall forthwith compute the adjusted number of shares to be
so issued and prepare a certificate setting forth such adjusted conversion
amount and the facts upon which such adjustment is based, and such certificate
shall forthwith be filed with the Transfer Agent for the Series B Preferred
Stock and the Common Stock; and the Corporation shall mail to each holder of
record of Series B Preferred Stock notice of such adjusted conversion price.

          (h) In case at any time the Corporation shall propose:

              (i)   To pay any dividend or distribution payable in shares upon
its Common Stock or make any distribution (other than cash dividends) to the
holders of its Common Stock; or

              (ii)  To offer for subscription to the holders of its Common Stock
any additional shares of any class or any other rights; or

              (iii) Any capital reorganization or reclassification of its shares
or the merger of the Corporation with another corporation (other than a merger
in which the Corporation is the surviving or continuing corporation and which
does not result in any reclassification, conversion, or change of the
outstanding shares of Common Stock); or

              (iv)  The voluntary dissolution, liquidation or winding-up of the
Corporation; then, and in any one of more of said cases, the Corporation shall
cause at least fifteen (15) days prior notice of the date on which (A) the books
of the Corporation shall close for such stock dividend, distribution, or
subscription rights, or (B) such capital reorganization, reclassification,
merger, 

                                       14
<PAGE>
 
dissolution, liquidation or winding-up shall take place, as the case may be, to
be mailed to the Transfer Agent for the Series B Preferred Stock and for the
Common Stock and to the holders of record of the Series B Preferred Stock.

          (i) So long as any shares of Series B Preferred Stock shall remain
outstanding and the holders thereof shall have the right to convert the same in
accordance with provisions of this Section 4 the Corporation shall at all times
reserve from the authorized and unissued shares of its Common Stock a sufficient
number of shares to provide for such conversions.

          (j) The term Common Stock as used in this Section 4 shall mean Common
Stock of the Corporation as such stock is constituted at the date of issuance
thereof or as it may from time to time be changed or shares of stock of any
class of other securities and/or property into which the shares of Series B
Preferred Stock shall at any time become convertible pursuant to the provisions
of this Section 4.

          (k) The Corporation shall pay the amount of any and all issue taxes
(but not income taxes) which may be imposed in respect of any issue or delivery
of stock upon the conversion of any shares of Series B Preferred Stock, but all
transfer taxes and income taxes that may be payable in respect of any change or
ownership of Series B Preferred Stock or any rights represented thereby or of
stock receivable upon conversion thereof shall be paid by the person or persons
surrendering such stock for conversion.

          (l) Notwithstanding any statement or provision to the contrary in this
Amended and Restated Certificate of Designation or in any other document, the
Corporation is not obligated to issue, in the aggregate, more than 19.9% of its
outstanding shares of Common Stock determined as of the date of first issuance
of the Series B Preferred Shares (such amount to be proportionately and
equitably adjusted from time to time in the event of stock splits, stock
dividends, combinations, reverse stock splits, reclassification, capital
reorganizations and similar events relating to the Common Stock) (the "Exchange
Cap") upon conversion of the Series B Preferred Stock, if issuance of a larger
number of shares of Common Stock would constitute a breach of the Corporation's
obligations under the rules or regulations of The Nasdaq Stock Market, Inc. or
any other principal securities exchange or market upon which the Common Stock is
or becomes traded.

          (m) If  the Corporation cannot issue shares of Common Stock pursuant
to the conversion provisions of this Section 4 for any reason, including without
limitation the Exchange Cap, the holder of those shares of Series B Preferred
Stock for which the Corporation is unable to issue Common Stock, solely at such
holder's option, may elect to require the Corporation to redeem all of part of
such Series B Preferred Stock at the Redemption Price within ten business days
of receiving notice; provided the Corporation can make such a distribution to
such holders under the provisions of the state corporation laws then applicable.
In the event the Corporation receives a conversion notice from more than one
holder of Series B Preferred Stock on the same day, and the Corporation can
convert some, but not all, of such Series B Preferred Stock, the Corporation
will convert from each such holder of Series B Preferred Stock electing to have
Series B Preferred Stock converted at such time an amount equal to 

                                       15
<PAGE>
 
such holder's pro rata amount (based on the number of Preferred Shares held by
              --------
such holder relative to the number of Series B Preferred Stock outstanding) of
all Series B Preferred Stock being converted and the remaining shares that
cannot be converted will be redeemed pro rata at such time.
                                     --------              

     5.   Mandatory Conversion.
          ---------------------

          (a) Subject to the provisions of paragraph 5(e) below, the shares of
Series B Preferred Stock not previously converted into shares of Common Stock
shall be converted into shares of Common Stock without further action of the
Holder on the date that is two years from the date of issuance thereof, at the
Conversion Price and on the conversion terms specified in paragraph 4(b).

          (b) Notice of conversion of Series B Preferred Stock by the
Corporation pursuant to this Section 5 shall be given by mail or in such other
manner as may be prescribed by resolution of the Board not less than thirty (30)
days prior to the applicable date of mandatory conversion (the "Mandatory
Conversion Date").  As applicable, the notice shall specify the number of shares
to be converted, the date fixed for conversion, and the conversion price per
share.

          (c) The holder of any certificate for shares of Series B Preferred
Stock that is converted pursuant to this Section 5 shall surrender such
certificate at the principal office of any transfer agent for said stock (the
"Transfer Agent") properly endorsed for or accompanied by duly executed
instruments of transfer (and such other transfer papers as said Transfer Agent
may reasonably require). The holder of the shares so surrendered for conversion
shall be entitled to receive (except as otherwise provided herein) a certificate
or certificates which shall be expressed to be fully paid and non-assessable for
the number of shares of Common Stock to which such stockholder shall be entitled
upon such conversion registered in the name of such holder or in such other name
or names as such stockholder in writing may specify.

          (d) On and after the applicable Mandatory Conversion Date (subject to
paragraph 5(e) below), and notwithstanding that any certificate for shares of
Series B Preferred Stock so called for conversion shall not have been
surrendered for cancellation, all dividends on the Series B Preferred Stock
called for conversion shall cease to accrue and the shares represented thereby
shall no longer be deemed outstanding and all rights of the holders thereof as
stockholders of the Corporation shall cease and terminate, except the right to
receive the shares of Common Stock upon conversion as provided herein.

          (e) In no event shall a Mandatory Conversion occur at any time unless
the Common Stock to be delivered upon conversion will be immediately upon
delivery and thereafter, unlegended, freely tradable, and freely transferable on
the transfer books of the Corporation.

     6.   Event of Default.  The occurrence of any of the following events of
          -----------------                                                  
default ("Event of Default") shall cause the dividend rate of 6% described in
Section 2 hereof to become 15% from and after the occurrence of such event, and
at the option of the Holder, the Series B Preferred Stock shall be 

                                       16
<PAGE>
 
redeemed by the Corporation at its Stated Value and accrued dividends and the
Holder may rescind any unfilled Notice of Conversion:

          (a) The Corporation fails to pay any dividend payment required to be
paid pursuant to the terms of Section 2 hereof and such failure continues for a
period of ten (10) days.

          (b) The Corporation breaches any covenant or other term or condition
of the Subscription Agreement entered into between the Corporation and holder
relating to Series B Preferred Stock (the "Subscription Agreement") or in this
Certificate to Set Forth Designations, Voting Powers, Preferences, Limitations,
Restrictions, and Relative Rights of Series B 6% Cumulative Convertible
Preferred Stock, $0.001 Par Value Per Share, and such breach continues for a
period of seven (7) days after written notice to the Corporation from the
holder.

          (c) Any representation or warranty of the Corporation made in the
Subscription Agreement, or in any agreement, statement or certificate given in
writing pursuant thereto shall be false or misleading.

          (d) The Corporation shall make an assignment for the benefit of
creditors, or apply for or consent to the appointment of a receiver or trustee
for it or for a substantial part of its property or business; or such a receiver
or trustee shall otherwise be appointed.

          (e) Any money judgment, writ or similar process shall be entered or
filed against the Corporation or any of its property or other assets for more
than $100,000, and shall remain unvacated, unbonded or unstayed for a period of
forty-five (45) days.

          (f) Bankruptcy, insolvency, reorganization or liquidation proceedings
or other proceedings or relief under any bankruptcy law or any law for the
relief of debtors shall be instituted by or against the Corporation.

          (g) The delisting of the Common Stock from the NASDAQ SmallCap Market
or such other principal exchange on which the Common Stock is listed for
trading.

          (h) A concession by the Corporation of a default under any one or more
obligations in an aggregate monetary amount in excess of $100,000.

          (i) An SEC stop trade order or NASDAQ trading suspension, if either
applies for a period of ten days or longer.

          (j) The Corporation's failure to timely deliver Common Stock to the
holder pursuant to Section 4 hereof.

     7.   Voting Rights.  The shares of Series B Preferred Stock shall not have
          --------------                                                       
voting rights.

                                       17
<PAGE>
 
     8.   Status of Converted Stock.  In case any shares of Series B Preferred
          --------------------------                                          
Stock shall be converted pursuant to Section 4 hereof or otherwise repurchased
or reacquired, the shares so converted, or reacquired shall resume the status of
authorized but unissued shares of Preferred Stock and shall no longer be
designated as Series B Preferred Stock.

     9.   Additional Restrictions.  For as long as any shares of the Series B
          ------------------------                                           
Preferred Stock are outstanding, the Corporation will not issue any preferred
stock that is senior to the Series B Preferred Stock, and will not amend the
terms of the Series B Preferred Stock without the consent of the holders of the
Series B Preferred Stock.


              [The remainder of this page is intentionally blank]

                                       18
<PAGE>
 
        Signed on this 7th day of April, 1998.

                                        CHEMTRAK  INCORPORATED


                                        By: /s/ EDWARD F. COVELL
                                           ------------------------------
                                           President

ATTEST:

/s/ DONALD V. FLUKEN
----------------------------
Chief Financial Officer

                                       19