EXHIBIT 99.2


                            CERTIFICATION PURSUANT TO
                             18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

         In connection with the Quarterly Report of O.I. Corporation (the
"Company") on Form 10-Q for the period ended June 30, 2002, as filed with the
Securities and Exchange Commission on the date hereof (the "Report"), I, Juan M.
Diaz, Corporate Controller of the Company, certify, pursuant to 18 U.S.C.
Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of
2002, that:

         (1) The Report fully complies with the requirements of Section 13(a) or
15(d) of the Securities Exchange Act of 1934; and

         (2) The information contained in the Report fairly presents, in all
material respects, the financial condition and results of operations of the
Company.

/s/ Juan M. Diaz
- ------------------------------------
Name:  Juan M. Diaz
Title: Corporate Controller
Date:  August 13, 2002

This certification is made solely pursuant to Section 906 of the Sarbanes-Oxley
Act of 2002, and not for any other purpose.