Residual scale inhibitor analysis in produced waters, particularly for the sulphonated co-polymers is recognised as an ongoing challenge for many operators and chemical suppliers. Early benchtop methods have been well used and documented (e.g. dialysis / Hyamine based techniques etc.) however are considered time-consuming and laborious. This is one of the key problems faced when assaying residual sulphonated polymers to ppm and sub ppm levels as separation of the inhibitor from the brine is often a difficult operation. This has led to the development of improved solid phase extraction techniques using anion exchange cartridges for sulphonated species in our labs as detailed in our previous works in SPE 131100.  In addition, chromatographic techniques including Gel Permeation Chromatography (GPC)  and various other methodologies (described in the literature as 2nd and 3rd generation approaches [3, 4]) have been developed. These have all focused on improving accuracy, speciation (assay of specific polymers in solutions containing residual levels of different polymers) and automation, thereby reducing the labour intensive nature and reducing the potential for human error.
This paper describes significant progression for the analysis of sulphonated co-polymers. The new methodology, based on ion pair (IP) chromatography, is more robust and utilises conventional C18 reverse phase columns which were previously disregarded as being completely ineffective for separation of the anionic sulphonated co-polymers. This marks a step change in our ability to isolate and detect sulphonated polymers utilising standard robust (and long wearing) C18 columns together with an ion-pair reagent.
This breakthrough followed an extensive search for alternative columns (including a variety of anion exchange columns) all of which proved fruitless for separation and repeatable, reliable assay of sulphonated polymers. This paper describes the development and effectiveness of this new technique and summarises the various alternative columns and HPLC approaches trialed prior to our successful development. Results from validation exercises and further developments have also been described.