Abstract
The paper describes the development of a fully automated instrumental procedure for testing residual corrosion inhibitors in production waters in the field. Initial investigations were conducted in the laboratory to evaluate the suitability of ultraviolet and fluorescence spectrophotometric techniques to different types of corrosion inhibitors. Parameters for comparison included selectivity, sensitivity, speed, accuracy and precision of the methods under flowing conditions as in high performance liquid chromatography and static conditions as encountered in stand alone instruments. For the field, the number of personnel, technical experience and proximity of the district laboratory to the various leases were additional factors that were considered.
The laboratory evaluations showed that fluorescence is more suitable for the field application because errors from high salinity, contamination and matrix effect are minimized in fluorescence analysis. Although the development work included most of the nitrogen-containing corrosion inhibitors (quaternary amines, imidazolines, amides, etc.), the procedure for quaternary amines is used as the example and presented in detail.
Comparison of the automated fluorescence technique to the classic extraction/dye transfer technique showed the definite advantages of the former with respect to ease, speed, accuracy and precision. To the supplier, the new procedure has resulted in more timely and lower cost of analysis, more efficient utilization of field personnel, elimination of environmental and safety hazards and improved morale.
