ASTM: D6501:  Phosphonates in Brines

  • Summary
  • Analytes
  • Revision
  • Data and Sites
Official Method Name
Standard Test Method for Phosphonate in Brines
Current Revision
Current edition approved Dec. 10, 1999. Published April 2000.
Media
WATER
Instrumentation
Spectroscopy (Colorimetry; Photometry)
Method Subcategory
Inorganic
Method Source
  ASTM
Citation
  Annual Book of ASTM Standards, Section 11, Water and Environmental Technology, Volume 11.01, Water (I)
Brief Method Summary
Phosphonate materials are converted to orthophosphate by potassium persulfate digestion. The orthophosphate is then reacted with ammonium molybdate to form a phosphomolybdate complex. The complex is extracted with a methyl isobutyl ketone/cyclohexane mixture and measured colorimetrically.
Scope and Application
This test method covers the colorimetric determination of phosphonate (PNA) in brines from gas and oil production operations in the range from 0.1 to 5 mg/L. This phosphonate method is intended for use to analyze low concentration of phosphonate in brine containing interfering elements.
Applicable Concentration Range
0.1-5 mg/L
Interferences
Sulfide interferes in this test method, but techniques described in the procedure (see Section 9.1.2) eliminate this interference. Concentrations less than 1000 mg/L copper (Cu+2) and silica (SiO2/SiO3-2/Si+4); and less than 200 mg/L of iron (Fe+2/Fe+3 can be tolerated.
Produced brines can contain high concentrations of dissolved solids. Some of these dissolved solids tend to precipitate when produced brines reach new equilibria at atmospheric temperature and pressure. Phosphonate will coprecipitate or adsorb onto these newly formed solids and become unavailable for analysis. This problem can be minimized by acidifying the brine sample on-site with hydrochloric acid to pH below 2.
Glassware must be cleaned with phosphate free detergent and rinsed with 0.1 N hydrochloric acid to remove all residual phosphate or phosphonate.
The standard addition method in Section 12.6 is recommended for brine with high matrix interference.
Quality Control Requirements
Minimum quality control requirements are initial demonstration of proficiency, plus analysis of method blanks, quality control samples, and recovery spikes and, duplicate samples. For a general discussion of quality control and good laboratory practices, see Practices D 4210 and D 5789 and Guide D 3856.
Sample Handling
Collect the sample in accordance with Specification D 1192 or Practices D 3370, as applicable.
Preserve the samples immediately at the time of collection by adding 4 mL of 6 N hydrochloric acid per 100-mL brine.
Maximum Holding Time
Relative Cost
Unknown
Sample Preparation Methods