ASTM_D_4192_-_15.pdf

Designation:D419215Standard Test Method forPotassium in Water by Atomic AbsorptionSpectrophotometry1This standard is issued under the fixed designation D4192;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 determination of lowamounts of potassium in waters2having low solids content.The applicable range of this test method is 0.20 to 4.0 mg/Lwhen using the 766.5-nm resonance line.The range may beextended upward by dilution of an appropriate aliquot ofsample or by using the less-sensitive 404.4-nm resonance line.Many workers have found that this test method is reliable forpotassium levels to 0.02 mg/L,but use of this test method atthis low level is dependent on the configuration of the aspiratorand nebulizer systems available in the atomic absorptionspectrophotometer as well as the skill of the analyst.Theprecision and bias data presented are insufficient to justify useof this test method in the 0.02-mg/L range.1.2 This test method has been used successfully with spikedreagent water.It is the analysts responsibility to ensure thevalidity of this test method to other low dissolved solidsmatrices.1.3 The values stated in SI units are to be regarded asstandard.The values given in parentheses are mathematicalconversions to inch-pound units that are provided for informa-tion only and are not considered standard.1.4 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 a specificprecautionary statement,see 8.6.2.Referenced Documents2.1 ASTM Standards:3D1066 Practice for Sampling SteamD1129 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 ConduitsD4841 Practice for Estimation of Holding Time for WaterSamples Containing Organic and Inorganic ConstituentsD5810 Guide for Spiking into Aqueous SamplesD5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water Analysis3.Terminology3.1 Definitions:3.1.1 For definitions of terms used in this test method,referto Terminology D1129.4.Summary of Test Method4.1 Potassium is determined by flame atomic absorptionspectrophotometry.The potassium content is determined byaspirating the low solids sample directly with no samplepretreatment.5.Significance and Use5.1 Potassium occurs in rocks in a form that is not easilysolubilized;therefore,the potassium content of natural watersis usually low.Most natural waters contain less than 20 mg/Lof potassium,but waters containing several hundred milli-grams per litre are occasionally found.Potassium is essential toanimal nutrition,but a concentration of 1000 to 2000 mg/L instock water is regarded as the extreme limit permissible.1This 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 Feb.1,2015.Published March 2015.Originallyapproved in 1982.Last previous edition approved in 2008 as D4192 08.DOI:10.1520/D4192-15.2Platte,J.A.,and Marcy,V.M.,“ANew Tool for the Water Chemist,”IndustrialWater Engineering,May 1965.3For 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 6.Interferences6.1 In the analysis of low-solids water,interferences areusually negligible.7.Apparatus7.1 Atomic Absorption Spectrophotometer for use at 766.5nm.NOTE1The manufacturers instructions should be followed for allinstrumental parameters.Wavelengths other than 766.5 nm may be usedonly if they have been determined to be equally suitable.7.2 Potassium Hollow-Cathode LampsMultielement hol-low cathode lamps are available and also have been foundsatisfactory.7.3 Pressure-Reducing ValvesThe supplies of fuel andoxidant shall be maintained at pressures somewhat higher thanthe operating pressure of the instrument by using suitablevalves.8.Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests.Unless otherwise indicated,it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Societywhere such