Fast Ion Determinations and Efficient Separations of Complex Samples Using 4 µm Particle-Size Ion Exchange Columns

Transcription

1 Fast Ion Determinations and Efficient Separations of Complex Samples Using 4 µm Particle-Size Ion Exchange Columns Greg Malek, Peter Bodsky, Monika Verma, and Terri Christison; Thermo Fisher Scientific, Sunnyvale, CA

2 Overview Purpose: Demonstrate fast and efficient separations of ions in complex samples using 4 µm particle, high-resolution ion-exchange capillary columns. Methods: Analytes in complex samples are separated by ion-exchange chromatography on 4 µm and 5 µm resin size columns and detected by suppressed conductivity on high-pressure capable ion chromatography systems. Results: The data presented here shows the increased resolution from R s = to >.6 (EP) of critical peak pairs on the same column formulated with 4 µm resin particles compared the previous µm particle size. Ions were determined on these 4 µm columns in complex samples, such as a salt lake surface water, fruit juice, and amine scrubber solutions. The analyses were demonstrated on two high-pressure capable capillary IC systems and one high-pressure IC system at microbore ( mm i.d.) flow rates. Introduction Chromatographic peak resolution is critical for peak integration which improves accurate quantification, identification, and reporting accuracy. However, the need for fast analysis times and high sample throughput often necessitates sacrificing peak resolution, risking the reliability of the results reported. In the latest generation of ion chromatography columns, the resin particles were optimized to an average distribution of 4 µm from the earlier 7 µm particles. The resultant ion-exchange columns have very high plate counts, 8k k plates/column, which increase peak resolution of critical pairs. This allows fast separations while maintaining peak resolution in 5 mm length fast columns and allows increased peak resolution of complex samples using the mm high efficiency columns. The new generation of standard bore (4 and 5 mm i.d.), microbore ( and mm i.d.), and capillary size (.4 and.5 mm i.d.) ion-exchange columns are the optimal combination of chromatographic speed and resolution. Doubling the flow rates when using 5 mm columns proportionally reduces separations to 5 min. However the column backpressures on the 5 and mm length columns can increase to 45 psi which requires a high-pressure capable Reagent-Free ion chromatography (RFIC ) system and electrolytic eluent generation. The high-pressure compatible Eluent Generator Cartridges (EGC) precisely and accurately generates eluent inline through the hydrolysis of water. Methods Sample Preparation Samples were diluted with deionized water and filtered (. µm) as needed prior to injection. Instruments High-pressure chromatography instruments Thermo Scientific Dionex ICS-4 Dedicated Capillary HPIC system or Thermo Scientific Dionex ICS-5 + HPIC IC system configured for either capillary or microbore flow rates. Thermo Scientific Dionex AS-AP Autosampler Thermo Scientific Dionex Chromeleon Chromatography Data System with version Chromeleon 7.. Ion Chromatography Methods Columns: Thermo Scientific Dionex IonPac columns, specified in the figures Eluent Source: Thermo Scientific Dionex EGC Electrolytic Generating Cartridge for capillary flow rates or The high-pressure Thermo Scientific Dionex EGC 5 cartridge for 5 mm i.d. columns. Detection: Suppressed conductivity, recycle mode Thermo Scientific Dionex CES Capillary Electrolytic Suppressor for capillary flow rate or Thermo Scientific Dionex ERS 5 Electrolytically Regenerated Suppressor for microbore ( mm) or standard bore (4 mm) flow rates Fast Ion Determinations and Effi cient Separations of Complex Samples Using 4 μm Particle-Size Ion Exchange Columns

3 Figure shows the flow diagram of a capillary HPIC system using the Dionex ICS-4 or the ICS-5 + HPIC system configured for capillary flow rates. The flow path is not shown for the high-pressure Dionex ICS-5 + HPIC system configured for microbore flow rates. FIGURE. Flow diagram for a Capillary HPIC System. Dionex AS-AP Autosampler High Pressure capillary system Fresh 8 M Ω-cm Deionized Water Regen** Regen CRD Or CRD Bypass Syringe CES Suppressor CD Needle Columns Regen** Tray carousel Regen Fresh 8 M Ω-cm Deionized Water Results Internal sample loop Degas Module CR-TC New 4 µm Dionex Separation Columns These columns are prepared with smaller, 4 µm supermacroporous resin particles functionalized with the same chemistries as those with the larger (7 µm) resin particles (Figure ). These smaller particles result in significantly improved column efficiencies indicated by higher peak responses, typically.5-fold increase of S/N, enabling more accurate quantifications and more reliable results. FIGURE. SEM photo of Supermacroporous Particles. These particles are used in the Dionex IonPac AS8-4µm and Dionex IonPac ASHC-4µm anion-exchange columns. EGC ** flows through the back of the Dionex IC Cube Pump High-pressure capillary IC High-pressure capillary ion chromatography is now available on two instruments, the Dionex ICS-5 + HPIC modular IC system and the Dionex ICS-4 HPIC dedicated IC system. Capillary IC scales down column size, injection volumes, and flow rates by a factor of to to provide these benefits. Low µl/min operating flow rates allow the capillary IC system to stay on 4/7, resulting in very low baseline noise and high pump stability and less time equilibrating and calibrating the system. Low consumption of deionized water at 5 ml per day, and therefore low generation of waste, equating to 5 L per year. Longer cartridge life and delivery of higher eluent concentrations than optimum flow rates result in increased ease of use. Allows analysis at faster flow rates on 5 mm 4 µm columns which result in quick run times and faster results for short turn-around analysis. Allows better separations on the mm 4 µm columns which provide higher peak resolution, integration, and improved reporting accuracy. Thermo Scientifi c Poster Note PN784_E /S

4 Figure compares the separations of a -analyte standard under the same conditions on the µm and 4 µm resin particle formulations of the Dionex IonPac AS-HC column. The critical pairs of peaks, highlighted in blue, show increased separation on the 4 µm particle column. For example, Peaks and 4 originally have R s ~ (EP), but on the 4 µm column, the resolution (R s ) increased to.6 (EP). The other critical pairs show R s =.6 to (EP) on the 4 µm particle column. All analyte peaks are noticeably narrower, as evident by the 4% increase in peak response. FIGURE. Effect of particle size on the efficiency of separations using the Dionex IonPac AS-HC chemistry columns. 4 µm, 6 psi B µm, psi A Columns: A: Dionex IonPac AS-HC column set,.4 mm B: Dionex IonPac AS-HC-4µm column set,.4 mm Instrument:: Dionex ICS-5 + HPIC capillary system Eluent Source: Dionex EGC-KOH (capillary) cartridge Gradient: mm KOH ( 5 min), 5 mm (5 4 min), 5 mm (4 min), 6 mm ( min) Flow Rate:.5 ml/min Inj. Volume:.4 µl Column Temp.: C IC Cube Temp.: 5 C Detection: Suppressed conductivity, Dionex ACES Peaks:. Quinate. Monochloro-. Maleate. Fluoride acetate. Sulfate. Lactate. Bromate. Oxalate 4. Acetate. Chloride. Tungstate 5. Propionate 4. Nitrite 4. Phosphate 6. Formate 5. Trifluoroacetate. Phthalate 7. Butyrate 6. Bromide 6. Citrate 8. Methylsulfonate 7. Nitrate 7. Chromate. Pyruvate 8. Carbonate 8. cis-aconitate. Valerate. Malonate. trans -Aconitate Figure 4 shows the separation of analytes in a diluted, filtered orange juice sample on the capillary Dionex IonPac AS-HC-4µm column using the Dionex ICS-4 dedicated capillary IC system. The orange juice sample shows the characteristic profile dominated by citrate and malate with small amounts of the early eluting organic acids. FIGURE 4. Determination of inorganic anions and organic acids in an orange juice sample on a.4 mm i.d. Dionex IonPac AS-HC-4µm column - 4 5, Columns: Dionex IonPac AS-HC-4µm column set,.4 mm Instrument: Dionex ICS-4 HPIC Dedicated capillary IC system Eluent Source: Dionex EGC-KOH (Capillary) cartridge Gradient: mm KOH (5 min), 5 mm KOH (5 5 min), 5 mm KOH (4 min), 6 mm KOH ( min), 6 mm KOH ( 45 min) Flow Rate:.5 ml/min Inj. Volume:.4 µl Column Temp.: C IC Cube Temp.: 5 C Detection: Suppressed conductivity, Dionex ACES Sample Prep.: Diluted -fold, filtered,. µm Peaks:. Quinate. Unknown. Glycolate. Malate. Lactate. Maleate 4. Acetate 4. Unknown 5. Formate 5. Sulfate 6. Pyruvate 6. Oxalate 7. Galacturonate 7. Phosphate 8. Chloride 8. Citrate. Nitrate. Isocitrate. Glutarate. Unknown 4 Fast Ion Determinations and Effi cient Separations of Complex Samples Using 4 μm Particle-Size Ion Exchange Columns

5 Amine solutions are used to neutralize sour natural gas which contain hydrogen sulfide and hydrogen cyanide gases, to meet the air pollution control requirements and to provide a product without corrosive and toxic gases. The amines (Figure 5) and contaminants (Figure 8) are monitored to ensure the efficiency of the amine scrubbing process. After the amine solution capacity is exhausted, the waste must be characterized according to the waste discharge permits. FIGURE 5. Separation of inorganic cations and amines in an amine scrubber sample on a.5 mm i.d. Dionex IonPac CS6-5µm cation-exchange column..8 Separations using mm i.d. 4 µm particle columns Figure 6 demonstrates the fast separations from. to.8 ml/min of a nine-anion standard on a 5 mm, Dionex IonPac AS8-4µm column with the high-pressure capable Dionex ICS-5 + HPIC system. Sample run times were reduced from to 5 min. All peaks except nitrate and sulfate, Peaks 7 and 8, show peak-to-peak separation at the highest flow rate (R s (EP) > ), whereas nitrate and sulfate are almost baseline resolved (R s (EP) >.6). FIGURE 6. Fast separations of a nine-anion standard using a mm i.d. Dionex IonPac AS8-4µm anion-exchange column. Columns: Dionex IonPac AS8-4µm column set 6 5 mm Instrument: Dionex ICS-5 + HPIC high-pressure system 7 8 Eluent Source: Dionex EGC 5 KOH cartridge 4 Eluent: mm KOH Flow Rate: A:., B:., C:.8 ml/min Inj. Volume: 5 µl 5 Column Temp.: C C Detection: Suppressed conductivity, Dionex 6 psi AERS 5, recycle mode, A: 5, B: 6, C: ma Figure 7 demonstrates the fast separations of a diluted Salton Sea surface water sample with to mg/l of chloride and sulfate as injected, eluting within 5 min with resolution R s > (EP). FIGURE 7. Fast Separations of a Salton Sea surface water sample 7 Columns: Dionex IonPac AS8-4µm column set, 5 mm Instrument: Dionex ICS-5 + HPIC high-pressure system Eluent Source: Dionex EGC 5 KOH cartridge Eluent: mm KOH Flow Rate:.8 ml/min Inj. Volume: 5 µl Column Temp.: C Detection: Suppressed conductivity, Dionex AERS 5, recycle mode, ma Sample Prep.: -fold diluted, filtered,. µm Total Peaks:. Chloride. g/l. Carbonate --. Sulfate 8. - B A psi 8 4 psi 5 6 Column: Dionex IonPac CS6 column set,.5 mm Instrument: Dionex ICS-5 + HPIC high-pressure system Eluent Source: Dionex EGC-MSA (capillary ) cartridge Gradient : 6 8 mm MSA min, 8 55 mm MSA 55 min Flow Rate:.4 ml/min Inj. Volume:.4 µl Column Temp.: 4 C Detection: Suppressed conductivity, Dionex CCES, recycle mode, ma Sample: Amine scrubber solution spiked with sodium, diethanolamine, and triethanolamine Dilution: -fold Peaks:. Sodium. Ethanolamine. Diethanolamine 4. Triethanolamine Peaks:. Fluoride.5 mg/l. Chlorite.. Chloride. 4. Nitrite Carbonate Bromide. 7. Sulfate. 8. Nitrate.. Chlorate. Thermo Scientifi c Poster Note PN784_E /S 5

6 After the amine scrubbing process, the hydrogen sulfide and carbon dioxide gases are strippe from the amine solution as elemental sulfur and carbon dioxide. The remaining contaminants scrubbing solution are collectively called heat stable salts. The concentrations of these contaminants are monitored to ascertain the capacity of the amine scrubbing solution and to discharge permit requirements. Fifteen of these anions are show below in Figure 8 with a gra separation on a mm i.d. IonPac AS-HC-4µm column. FIGURE 8. Determination of heat stable amine salts added to an amine scrubber sample of % methyldiethanolamine on a mm i.d. Dionex IonPac AS-HC-4µm column 6 psi 5 4 Columns: Dionex IonPac AS-HC-4µm column set, mm Instrument: Dionex ICS-5 + HPIC high-pressure sys Eluent Source: Dionex EGC 5 KOH cartridge Gradient : mm (- to 8 min), mm (8 8 min), 7 mm (8 8 min), 7 mm (8 7 min ) Flow Rate:.8 ml/min Inj. Volume: 5 µl Column Temp.: C Detection: Suppressed conductivity, Dionex AERS 5 mm, recycle mode Peaks: mg/l mg/l. Fluoride. Carbonate 5. Acetate. Sulfite. Propionate. Sulfate 4. Formate. Oxalate 5. Chloride. Phosphate 6. Nitrite 4. Thiosulfate 7. Bromide 5. Thiocyanate 8. Nitrate Conclusion Separations of inorganic anions, organic acids, and alkanolamines in complex samples were demonstrated on the 4 µm particle size columns on capillary and mm i.d. format and detected by suppressed conductivity detection using a highpressure capable ion chromatography instrument. The Dionex high-pressure capillary IC systems, the Dionex ICS-4 HPIC dedicated system and the Dionex ICS-5 + HPIC modular system are IC On Demand, Always On, Always Ready for your sample analysis. The µl/min flow rates generate only 5 to L of waste per year, saving money on consumables and waste handling. These systems can utilize the new 4 µm particle columns, producing fast separations on the 5 mm length columns and with very high resolution on the mm length columns. For more information, refer to recent applications, Application Brief AB 4 and Technical Notes TN, TN 7, and TN. 4 References. Pang, F.; Christison, T.; Jack, R.; Lopez, L. AB 4: Fast Determination of Inorganic Anions in Municipal Drinking Water Using Capillary Ion Chromatography, LPN 5, Thermo Fisher Scientific Inc., Sunnyvale, CA,.. Christison, T.; Lopez, L. Technical Note : Practical Guidance for using capillary IC, TN_E /SV LPN4, Thermo Fisher Scientific, Sunnyvale, CA,.. Christison, T.; Lopez, L. Technical Note 7: Fast Determinations of Inorganic Cations in Influent and Effluent Wastewater Samples using High-Pressure IC, TN74_E /S, Thermo Fisher Scientific, Sunnyvale, CA,. 4. Christison, T.; Lopez, L. Technical Note : Separation of Heat Stable Amine Salts in Methyldiethanolamine (MDEA) using High-Pressure IC, TN7_E /S, Thermo Fisher Scientific, Sunnyvale, CA,. 6 Fast Ion Determinations and Effi cient Separations of Complex Samples Using 4 μm Particle-Size Ion Exchange Columns

7 6 Thermo Fisher Scientific Inc. All rights reserved. All trademarks are the property of Thermo Fisher Scientific, Inc. and its subsidiaries. Specifications, terms and pricing are subject to change. Not all products are available in all countries. Please consult your local sales representative for details. Australia Austria Belgium Brazil Canada China (free call domestic) Denmark Finland +58 France Germany India Italy Japan Korea Latin America Netherlands New Zealand Norway Singapore Sweden Switzerland Taiwan UK/Ireland USA EAS_PN784_E 8/6S