Development of a flow injection analysis method for the determination of acrylamide copolymers in brines

Two primary methods are available for the measurement of polyacrylamide concentration in oilfield brines. One of these is a flow injection analysis (FIA) method based on the reaction of acrylamides with bromine (the starch–iodide method). The FIA method provides rapid sample throughput and high reproducibility, but may be sensitive to interferences or changes in the sample matrix. In this work, systematic optimization of the FIA method was conducted to improve analytical stability, reproducibility, and sensitivity. The effects of potential sources of interference from brines were examined in detail. These included Na+, Ca2+, Cr3+, Al3+, ZrIV, NH4+, Cl−, OH−, CO32− ions, sample coloration, and commonly used surfactants. Since the FIA method measures amide group concentration, the linearity of response for a series of partially hydrolysed polyacrylamides was measured. The range of the method is 2 to 1200 mg/l. Sample throughput is 30 samples/h with triplicate analysis. Relative standard deviations of 0.2% are readily obtained from standard solutions and 0.5% from complex samples (at 1000 mg/l).