Numerous products are available to the oil industry that dissolve barium sulfate and other field scales. Several commercial products were evaluated for dissolution behavior on actual field scale. Testing conditions included temperature, salinity of the make up water and exposure time. Inductively coupled argon plasma (ICAP) spectroscopy is usually the scientist's first choice for the analyses of cations. Matrix problems needed to be addressed as well as detection limits. An ion chromatographic (IC) method was developed to simultaneously analyze for monovalent and divalent cations. Data was compared to ICAP. The IC method gives an excellent separation and eliminates any need for matrix matching of samples and standards. Low levels of magnesium, calcium, strontium, and barium may be detected in samples with high sodium and/or potassium content. It works particularly well for the scale dissolver samples as the four divalent cations of interest are analyzed in a single chromatogram. Detection limits at or below 0.1 mg/l are possible in this complex matrix. The eluent, methanesulfonic acid (MSA), is certainly strong enough to displace cations from the nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) complexes and other possible complexes.
