Assay Interconversions

PRO/II models all assays as one or more sets of pseudo-components. Each set of pseudo-components represents assay distillation curve data as a group of discrete components of increasing molecular weights having increasing boiling points. These pseudo-components loosely correspond to the cut-points used to characterize the assay data. See Assay Distillation Types for a description of the curves supported by PRO/II.

All assay distillation curves must be converted to a True Boiling Point basis (TBP) at 760 mm Hg pressure before being used to determine the pseudo-component normal boiling points. Several methods are provided for converting test data to a TBP 760 curve (and back to the original curve). These methods are supported through keywords by the CONVERSION entry on the ASSAY statement. The interconversion methods available in PRO/II include:

API94   Defined as procedure 3A3.1 in the 1994 API Technical Data Book. Different procedures apply when converting the various assay curves. (Starting with PRO/II version 8.1, this is the default method.)

API87   Defined as procedure 3A3.1 in the 1987 API Technical Data Book.

API63   Defined in the 1963 API Technical Data Book. This is comprised of the Edmister correlations recommended by the Americam Petroleum Institute prior to 1987.

EDOK   The Edmister-Okimoto correlation developed contemporaneously with the API63 method.

Not every conversion method is suitable for converting every type of distillation curve supported by PRO/II. Refer to the following topics for recommended interconversion methods for each supported type of distillation curve.

ASTM D86 to TBP Curve Interconversion

ASTM D2887 to TBP 760 Conversion

ASTM D2887 to ASTM D86 Conversion

Additional Information

Assay Processing Reference Help