表面活性剂中同系物检测方案(液相色谱仪)

Authors Victoria Elsner Institute for Pure and Applied MassSpectrometry， University of Wuppertal， Wuppertal， Germany Oliver J. Schmitz Applied Analytical Chemistry， University of Duisburg-Essen， Essen， Germany Volker WulfBASF Personal Care and NutritionGmbH Dusseldorf， Germany Edgar Naegele Agilent Technologies R&D andMarketing GmbH & Co.KG， Waldbronn， Germany Separation of Homologous Series ofTechnical Detergents with the Agilent1290 Infinity 2D-LC Solution Coupledto an Evaporative Light ScatteringDetector Application Note Food Testing & Agriculture - Consumer Products Abstract This Application Note shows the separation of a series of homologous non-ionicsurfactants in a technical product with the Agilent 1290 Infinity 2D-LC Solutionby combination of a HILIC column in the first dimension and a reversed phasecolumn in the second dimension. Surfactants typically do not show activity in UVdetection， hence， the Agilent 1260 Infinity ELSD was used. The visualization of thecompounds detected by the ELSD is demonstrated with dedicated 2D-LC software. Fatty alcohol ethoxylates belong to theclass of non-ionic surfactants and areused for a large variety of consumerproducts like cosmetics， cleaners， colors，plant protection， textiles and otherindustrial applications. The productionprocess starts with a homologous seriesof fatty alcohol compounds typically fromlauryl alcohol (C，) to stearyl alcohol(C). These compounds are reacted withethylene oxide， which gives a secondhomologous series of ethoxylates at theother side of the molecule (Figure 1). To monitor the quality and composition ofthe technical product， it is important tohave a separation method in hand whichis able to separate both homologousseries， the fatty alcohol componentand the successive series of ethoxylateunits. The only separation technologywhich can fulfill this requirement iscomprehensive 2-dimensional liquidchromatography by combination ofthe selectivity of a HILIC and an RPseparation. The other challenge is to findthe right detection method because UVdetection is not possible due to the lackof UV activities of these compounds.Typically an Evaporative Light ScatteringDetector (ELSD) is used for such aclass of non-UV active and nonvolatilecompounds. In addition， this is acost-effective detection method useful fortechnical quality control. C-C： Figure 1. Structure formula of fatty alcohol ethoxylat compounds. Experimental Method Two 40-pL loops are connected to the 2-Position/4-Port Duo valve and are located on the left side. Autosampler Water， 50 mM ammonium acetate Injection volume 5pL Sample temperature 8°C Needle wash 6 seconds in methanol ELSD 120 min -70 % B， 140 min -70 % B， 160 min-97 %B Evaporator temperature 80°C Post time 20 minutes 2d dimension pump Solvent A Water， 10 mM ammonium acetate Solvent B Methanol Flow rate 3 mL/min Initial gradient 0 min-50 % B， 0.1 min -70 % B， 0.65 min-95%B， 0.75 min-95 % B， 0.80 min-50 % B， 1.00 min-50% B Stop time 1.00 minute Equipment The Agilent 1290 Infinity 2D-LCSolutionconsists ot： Agilent 1290 Infinity Binary Pump(G4220A) Agilent 1260 Infinity QuaternaryPump (G-1311B) Agilent 1290 Infinity Autosampler(G4226A) with Thermostat(G1330A) Agilent 1290 Infinity ThermostattedColumn Compartment (TCC)(G1316C) with 2-Position/4-PortDuo valve (G4236A) for 2D-LC Agilent 1260 Infinity ELSD Software Open Lab CDS ChemStation Rev. C01.03with 2D-LC add-on software. LCxLCSoftware for 2D-LC data analysis from GCImage LLC.， Lincoln， NE， USA. Column 1st dimension SeQuant， Sweden， ZIC-HILIC，250×2.1 mm， 5 pm Column 2nd dimension Dr. Maisch GmbH， Germany， ReprospherC8-Aqua， 30x4.6 mm，5 pm Chemicals All solvents used were LC grade.Acetonitrile and methanol werepurchased from Merck， Germany. Freshultrapure water was obtained from aMilli-QIntegral system equipped with a0.22-pm membrane point-of-use cartridge(Millipak). All chemicals used as standardwere purchased from Sigma-Aldrich，Germany. Sample A synthetic， technical， fatty alcoholethoxlyate with an alkyl chain from C1，2to C was dissolved in acetonitrile/water 80/20 (v/v) and diluted to the finalconcentration of 3 mg/mL. Results and Discussion The comprehensive 2-dimensionalseparation of the technical mixture offatty alcohol ethoxylates was done on aHILIC phase in the first dimension undertypical HILIC conditions. The seconddimension separation was done on areversed phase column under typical RPconditions. The HILIC phase in the firstdimension separates the compounds bytheir increasing degree of ethoxylationfor compounds with 3 to 20 ethoxyunits. The reversed phase column in thesecond dimension separates the fractionof ethoxylate with a defined degree ofethoxylation by their fatty alcohol chainlength by increasing number of carbonatoms (Figure 2). The 2-dimensional separation spaceis nearly perfectly orthogonal. It startswith the lowest carbon chain length andlowest degree of ethoxylation at thelowest retention time in first and seconddimension time. The second dimensionretention time increases by chain lengthand the first dimension retention timeincreases by ethoxylation yielding thehighest 2-dimension retention time forlong chain compounds with highestdegree of ethoxylation (Figure 2). The analysis under given conditionsshows perfect separation for eachcompound in the mixture and allowsits characterization. The ELSD is ableto acquire data at a data rate sufficientto follow the fast chromatographicseparation in the second dimension.For a product mixture which was wellcharacterized in advance， the maincompounds can be confirmed easily for aproduction batch. Lower level compoundscan be seen on a lower signal intensitylevel. For a more reliable confirmation， amore sensitive detection such as massspectrometry is required (data not shownhere). Conclusion This Application Note demonstratesthe capability to run the Agilent 1290Infinity 2D-LC Solution with an ELSD asa detector for non-UV active compounds.This can be used for the separationand detection of complex oil and fattyalcohols or acids and their derivatives.These compounds are important technicalbasic chemicals typically occurring incomplex mixtures from the productionprocess and， hence， 2D-LC separationcould be used for quality control ofproduction batches.S. www.agilent.com/chem This information is subject to change without notice. C Agilent Technologies， Inc.， 2013-2014 Published in the USA， September 15， 2014 5991-2775EN Agilent Technologies 本应用显示了使用Agilent 1290 Infinity 2D-LC解决方案实现表面活性剂中一系列同源非离子的分离，第一维使用的是HILIC柱，第二维使用的是反相色谱柱。 表面活性剂通常在紫外线下不显示活性检测，因此使用了Agilent 1260 Infinity ELSD。 通过ELSD检测到的化合物可以通过专用的2D-LC软件得到可视化演示。