|Range||MDL||Method||Kit Catalog No.||Refill Catalog No.|
|0-1 & 1-10 ppm||0.05 ppm||Phenanthroline (total & ferrous)||K-6210||R-6201|
|0-1 & 1-10 ppm||0.05 ppm||Phenanthroline (total & soluble)||K-6010||R-6001|
|0-30 & 30-300 ppm||5 ppm||Phenanthroline (total & ferrous)||K-6210D||R-6201D|
|0-30 & 30-300 ppm||5 ppm||Phenanthroline (total & soluble)||K-6010D||R-6001D|
|0-60 & 60-600 ppm||10 ppm||Phenanthroline (total & soluble)||K-6010A||R-6001A|
|0-120 & 120-1200 ppm||20 ppm||Phenanthroline (total & soluble)||K-6010B||R-6001B|
|0-1200 & 1200-12,000 ppm||200 ppm||Phenanthroline (total & soluble)||K-6010C||R-6001C|
|0-100 & 100-1000 mg/L||5 mg/L||Ferric Thiocyanate (Iron in brine)||K-6002||R-6002|
|Range||Method||Kit Catalog No.|
|0-2.50 ppm||PDTS (total)||K-6023|
|0-6.00 ppm||Phenanthroline (total & ferrous)||K-6203|
|0-6.00 ppm||Phenanthroline (total & soluble)||K-6003|
Iron is present in nature in the form of its oxides, or in combination with silicon or sulfur. The soluble iron content of surface waters rarely exceeds 1 mg/L, while ground waters often contain higher concentrations. The National Secondary Drinking Water Standard for iron is 0.3 mg/L, as iron concentrations in excess of 0.3 mg/L impart a foul taste and cause staining. High concentrations in surface waters can indicate the presence of industrial effluents or runoff.
Iron contamination in oil field brines are typically a result of corrosion processes of iron-containing metallic components and equipment. Accumulation of insoluble iron salts in a brine completion fluid can result in substantial formation damage and can significantly affect the productivity of an oil well. Quantifying total iron in brine is critical.
The Phenanthroline Method (total & soluble; total & ferrous)
References: APHA Standard Methods, 22nd ed., Method 3500-Fe B - 1997. ASTM D 1068-77, Iron in Water, Test Method A. J.A. Tetlow and A.L. Wilson, "The Absorptiometric Determination of Iron in Boiler Feed-water," Analyst. Vol. 89, p. 442 (1964).
With the Phenanthroline method, ferrous iron reacts with 1,10-phenanthroline to form an orange-colored chelate. To determine total iron, thioglycolic acid solution is added to reduce ferric iron to the ferrous state. The reagent formulation minimizes interferences from various metals. Results are expressed as ppm (mg/L) Fe.
The PDTS Method (total)
Reference: G. Frederick Smith Chemical Co., The Iron Reagents, 3rd ed., p. 47 (1980). J. A. Tetlow and A. L. Wilson, "The Absorptiometric Determination of Iron in Boiler Feed-water," Analyst. Vol. 89, p. 442 (1964).
CHEMetrics' colorimetric method for determining total iron uses thioglycolic acid to dissolve particulate iron and to reduce iron from the ferric to the ferrous state. Ferrous iron then reacts with PDTS (3-(2-pyridyl)-5,6- bis(4-phenylsulfonic acid)-1,2,4-triazine disodium salt) in acid solution to form a purple-colored chelate. Results are expressed as ppm (mg/L) Fe.
The Ferric Thiocyanate Method (Iron in Brine)
Reference: D. F. Boltz and J. A. Howell, eds., Colorimetric Determination of Nonmetals, 2nd ed., Vol. 8, p. 304 (1978). Carpenter, J.F. "A New Field Method for Determining the Levels of Iron Contamination in Oilfield Completion Brine", SPE International Symposium (2004).
The Iron in Brine test employs the ferric thiocyanate chemistry. In an acidic solution, hydrogen peroxide oxidizes ferrous iron. The resulting ferric iron reacts with ammonium thiocyanate forming a red-orange colored thiocyanate complex, in direct proportion to the iron concentration.
Results, expressed in mg/L, can be converted to mg/kg by dividing by the density of the brine.