ASTM_D_6501_-_15.pdf

Designation:D650115Standard Test Method forPhosphonate in Brines1This standard is issued under the fixed designation D6501;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope*1.1 This test method covers the colorimetric determinationof phosphonate(PNA)in brines from gas and oil productionoperations in the range from 0.1 to 5 mg/L.1.2 This phosphonate method is intended for use to analyzelow concentration of phosphonate in brine containing interfer-ing elements.This test method is most useful for analyzingphosphonate at 0.1 to 1 mg/L range in brines with interferingelements;however,it requires personnel with good analyticalskill.1.3 This test method has been used successfully withreagent water and both field and synthetic brine.It is the usersresponsibility to ensure the validity of this test method forwaters of untested matrices.1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.For specific hazardstatements,see 9.1.3.2.Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD3856 Guide for Management Systems in LaboratoriesEngaged in Analysis of WaterD4375 Practice for Basic Statistics in Committee D19 onWaterD5810 Guide for Spiking into Aqueous SamplesD5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water AnalysisE275 Practice for Describing and Measuring Performance ofUltraviolet and Visible Spectrophotometers3.Terminology3.1 DefinitionsFor definitions of terms used in this testmethod,refer to Terminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 phosphonate,na group of organophosphorus com-pounds typically used for mineral scale and corrosion control,as cleaning agents,dispersants,and chelants.3.2.1.1 DiscussionTypicalphosphonatecompoundsinclude,but are not limited to,the following phosphonic acidand their neutralized salts:Aminotri(methylenephosphonicacid),1-hydroxyethylidene-1,1-diphosphonic acid,ethylenedi-aminetetra(methylenephosphonic acid),hexamethylenedi-aminetetra(methylenephosphonic acid),and diethylenetri-aminepenta(methylenephosphonic acid).4.Summary of Test Method4.1 Phosphonate materials are converted to orthophosphateby potassium persulfate digestion.The orthophosphate is thenreacted with ammonium molybdate to form a phosphomolyb-date complex.The complex is extracted with a methyl isobutylketone/cyclohexane mixture and measured colorimetrically.5.Significance and Use5.1 This test method is useful for the determination of tracelevel phosphonate residues in brines.Chemical treatmentwhich contain phosphonates are used as mineral scale andcorrosion inhibitors in gas and oil drilling and productionoperations;and other industrial applications.Often,the deci-sion for treatment is based on the ability to measure lowphosphonate concentration and not upon performance criteria.Phosphonate concentrations as low as 0.16 mg/L have beenshown effective in carbonate scale treatment.This test methodenables the measurement of sub-mg/L phosphonate concentra-tion in brines containing interfering elements.5.2 The procedure includes measuring total(see 12.3.8)andfree orthophosphate(see 12.4.3)ions and the difference in1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.05 on Inorganic Constituentsin Water.Current edition approved March 15,2015.Published April 2015.Originallyapproved in 1999.Last previous edition approved in 2009 as D6501 09.DOI:10.1520/D6501-15.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 concentration is the phosphonate concentration.The samplecould contain orthophosphate naturally,or from decompositionof the phosphonate during processing or well treatment or fromtreating compounds containing molecular dehydrated phos-phates.6.Interferences6.1 Sulfide interferes in this test method,but techniquesdescri