ASTM_D_7419_-_13.pdf

Designation:D741913Standard Test Method forDetermination of Total Aromatics and Total Saturates inLube Basestocks by High Performance LiquidChromatography(HPLC)with Refractive Index Detection1This standard is issued under the fixed designation D7419;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 totalaromatics and total saturates in additive-free lube basestocksusing high performance liquid chromatography(HPLC)withrefractive index(RI)detection.This test method is applicableto samples containing total aromatics in the concentrationrange of 0.2 to 46 mass%.1.1.1 Polar compounds,if present,are combined with thetotal aromatics.Precision was determined for basestocks withpolars content 1.0 mass%.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 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.2.Referenced Documents2.1 ASTM Standards:2D4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD6299 Practice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System Performance3.Terminology3.1 Definitions:3.1.1 aromatics,ninhighperformanceliquidchromatography,aromatic hydrocarbon components,minuspolar material,that has a longer retention time than saturates onthe specified polar columns,but can be removed as a singlepeak by backflushing the columns with heptane.3.1.1.1 DiscussionGenerally,aromatic hydrocarbons con-tain 1 to 4 rings.3.1.2 backflush,velution of the HPLC mobile phase in thebackward or reverse direction from the silica gel columntowards the cyano column.3.1.2.1 DiscussionIn this test method,it is used to elutethe total aromatics plus polars as one sharp component.3.1.3 foreflush,velution of HPLC mobile phase in theforward direction.3.1.3.1 DiscussionIn this test method,the sample entersthe cyano column first followed by elution through the silicagel column.3.1.4 polars,ninhighperformanceliquidchromatography,components that may contain organicallybonded nitrogen,oxygen and oxidized sulfur components andare more strongly retained than aromatic hydrocarbons.3.1.4.1 DiscussionIn this HPLC method,polars are back-flushed with the aromatics and the two cannot be distinguished.Generally present in very small amounts,such as 1.5 mL have been used successfully.6.9 Analytical Balanceaccurate to 60.0001 g.7.Reagents and Materials7.1 Heptane,HPLC grade.If necessary,dry solvent withmolecular sieves and then filter before use.7.2 Dichloromethane,HPLC or UV grade.If necessary,drysolvent with molecular sieves and then filter before use.7.3 Octadecylbenzene,97%pure.7.4 Hexadecane,98%pure.8.Sampling8.1 Follow Practice D4057 or D4177,or a similar standardto obtain a representative laboratory sample of the basestock.Mix well before sampling.9.Preparation of Apparatus9.1 Set up the liquid chromatograph,injection system,columns,backflush valve,optional column oven,optional UVdetector,refractive index detector and computing integrator inaccordance with the manufacturers instructions and as de-picted in Fig.1.Insert the backflush valve so that the detectoris always connected independently of the direction of flowthrough the column(see Fig.1).Maintain the sample injectionvalve at the same temperature as the sample solution;in mostcases this will be at room temperature.To minimize drifts insignal,ensure that the ambient temperature is relatively con-stant during analysis and calibration.9.2 New commercial columns may be packed in water/methanol or other polar solvents.Before these columns can beused flush them with dichloromethane followed with heptanebefore proceeding.Other suitable solvents that restore theTABLE 1 Examples of Operating Conditions Used in Cooperative StudiesLab ALab BLab CSilica ColumnVarian,50 cm length by 7.7 mm i.d.5 m Si60Varian,50 cm by 7.7 mm Si60(CP28526)Phenomenex,2 x Si60(10 by 250 mm,5 mCyano ColumnAlltech/YMC,100 by 10 mm 10 mWaters/YMC,100 by 12 mm 5 mYMC,10 by 100 mm 5 mRI DetectorAgilent 1200Hewlett Packard RI,model HP1047AShimadzu RID-10AHeptane Flow(mL/min)3.5 mL/min3.03.0Resolution55-610.3Injected Volume(microlitres)101010D7419 132 required resolution may be used.If the resolution requirementis not met,the column may be reactivated by flushing it withadditional dichloromethane.If the resolution still cannot beattained it may be necessary to replace the column o