Fast Ion Determinations and Effi cient Separations of...

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

Greg Malek, Peter Bodsky, Monika Verma, and Terri Christison; Thermo Fisher Scientifi c, Sunnyvale, CA

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

ResultsNew 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 (7–9 µm) resin particles (Figure 2). These smaller particles result in significantly improved column efficiencies indicated by higher peak responses, typically 1.5-fold increase of S/N, enabling more accurate quantifications and more reliable results.

Fast Ion Determinations and Efficient Separations of Complex Samples Using 4 µm Particle-Size Ion Exchange ColumnsGreg Malek, Peter Bodsky, Monika Verma, Terri Christison, Thermo Fisher Scientific, Sunnyvale, California, USA

Conclusion Separations of inorganic anions, organic acids, and alkanolamines in complex

samples were demonstrated on the 4 µm particle size columns on capillary and 2 mm i.d. format and detected by suppressed conductivity detection using a high-pressure capable ion chromatography instrument.

The Dionex high-pressure capillary IC systems, the Dionex ICS-4000 HPIC dedicated system and the Dionex ICS-5000+ HPIC modular system are “IC On Demand”, Always On, Always Ready for your sample analysis. The µL/min flow rates generate only 5 to 10 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 150 mm length columns and with very high resolution on the 250 mm length columns.

For more information, refer to recent applications, Application Brief AB 141 and Technical Notes TN 113, TN 117, and TN 122.1–4

References 1. Pang, F.; Christison, T.; Jack, R.; Lopez, L. AB 141: Fast Determination of

Inorganic Anions in Municipal Drinking Water Using Capillary Ion Chromatography, LPN 3059, Thermo Fisher Scientific Inc., Sunnyvale, CA, 2012.

2. Christison, T.; Lopez, L. Technical Note 113: Practical Guidance for using capillary IC, TN113_E 02/12SV LPN3043, Thermo Fisher Scientific, Sunnyvale, CA , 2012.

3. Christison, T.; Lopez, L. Technical Note 117: Fast Determinations of Inorganic Cations in Influent and Effluent Wastewater Samples using High-Pressure IC,TN70141_E 01/13S, Thermo Fisher Scientific, Sunnyvale, CA , 2013.

4. Christison, T.; Lopez, L. Technical Note 122: Separation of Heat Stable Amine Salts in Methyldiethanolamine (MDEA) using High-Pressure IC, TN70192_E 01/13S, Thermo Fisher Scientific, Sunnyvale, CA , 2013.

OverviewPurpose: 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 Rs = 1 to > 1.6 (EP) of critical peak pairs on the same column formulated with 4 µm resin particles compared the previous 9 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 (2 mm i.d.) flow rates.

IntroductionChromatographic 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 7–9 µm particles. The resultant ion-exchange columns have very high plate counts, 8k–12k plates/column, which increase peak resolution of critical pairs. This allows fast separations while maintaining peak resolution in 150 mm length fast columns and allows increased peak resolution of complex samples using the 250 mm high efficiency columns. The new generation of standard bore (4 and 5 mm i.d.),microbore (2 and 3 mm i.d.), and capillary size (0.4 and 0.5 mm i.d.) ion-exchange columns are the optimal combination of chromatographic speed and resolution. Doubling the flow rates when using 150 mm columns proportionally reduces separations to 3–5 min. However the column backpressures on the 150 and 250 mm length columns can increase to 3000–4500 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.

MethodsSample Preparation

Samples were diluted with deionized water and filtered (0.2 µm) as needed prior to injection.

Instruments

High-pressure chromatography instruments

• Thermo Scientific™ Dionex™ ICS-4000 Dedicated Capillary HPIC™ system or

• Thermo Scientific™ Dionex™ ICS-5000+ 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 7.1.2

All trademarks are the property of Thermo Fisher Scientific Inc. and its subsidiaries.

This information is not intended to encourage use of these products in any manners that might infringe the intellectual property rights of others.

FIGURE 2. SEM photo of Supermacroporous Particles. These particles are used in the Dionex IonPac AS18-4µm and Dionex IonPac AS11HC-4µm anion-exchange columns.

FIGURE 1. Flow diagram for a Capillary HPIC System.

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 500 cartridge for 2–5 mm i.d. columns.

Detection: Suppressed conductivity, recycle mode

• Thermo Scientific™ Dionex™ CES™ Capillary Electrolytic Suppressor for capillary flow rates or

• Thermo Scientific™ Dionex™ ERS™ 500 Electrolytically Regenerated Suppressor for microbore (2 mm) or standard bore (4 mm) flow rates

EGC

High Pressure capillary system

DegasModule Pump

Regen

CD

CRD200

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loop

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Fresh 18 M Ω-cm Deionized Water

Dionex AS-AP Autosampler

Syringe

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Or CRD Bypass

Columns


** flows through the back of the Dionex IC Cube

FIGURE 6. Fast separations of a nine-anion standard using a 2 mm i.d. Dionex IonPac AS18-4µm anion-exchange column.

Figure 6 demonstrates the fast separations from 0.25 to 0.38 mL/min of a nine-anion standard on a 2 × 150 mm, Dionex IonPac AS18-4µm column with the high-pressure capable Dionex ICS-5000+ HPIC system. Sample run times were reduced from 9 to 5 min. All peaks except nitrate and sulfate, Peaks 7 and 8, show peak-to-peak separation at the highest flow rate (Rs (EP) > 2), whereas nitrate and sulfate are almost baseline resolved (Rs (EP) > 1.6).

High-pressure capillary IC

High-pressure capillary ion chromatography is now available on two instruments, the Dionex ICS-5000+ HPIC modular IC system and the Dionex ICS-4000 HPIC dedicated IC system. Capillary IC scales down column size, injection volumes, and flow rates by a factor of 10 to 100 to provide these benefits.

• Low µL/min operating flow rates allow the capillary IC system to stay on 24/7, resulting in very low baseline noise and high pump stability and less timeequilibrating and calibrating the system.

• Low consumption of deionized water at 15–30 mL per day, and therefore low generation of waste, equating to 5–10 L per year.

• Longer cartridge life and delivery of higher eluent concentrations than optimumflow rates result in increased ease of use.

• Allows analysis at faster flow rates on 150 mm 4 µm columns which result in quick run times and faster results for short turn-around analysis.

• Allows better separations on the 250 mm 4 µm columns which provide higher peak resolution, integration, and improved reporting accuracy.

Figure 3 compares the separations of a 29-analyte standard under the same conditions on the 9 µm and 4 µm resin particle formulations of the Dionex IonPac AS11-HCcolumn. The critical pairs of peaks, highlighted in blue, show increased separation on the 4 µm particle column. For example, Peaks 3 and 4 originally have Rs ~1 (EP), but on the 4 µm column, the resolution (Rs) increased to 1.6 (EP). The other critical pairs show Rs = 1.6 to 2 (EP) on the 4 µm particle column. All analyte peaks are noticeably narrower, as evident by the 20–40% increase in peak response.

FIGURE 3. Effect of particle size on the efficiency of separations using the Dionex IonPac AS11-HC chemistry columns.

Separations using 2 mm i.d. 4 µm particle columns

Columns: Dionex IonPac AS11-HC-4µm column set, 0.4 × 250 mm

Instrument: Dionex ICS-4000 HPIC Dedicatedcapillary IC system

Eluent Source: Dionex EGC-KOH (Capillary) cartridgeGradient: 1 mM KOH (5 min),

1–15 mM KOH (5–15 min), 15–30 mM KOH (14–23 min), 30–60 mM KOH (23–31 min), 60 mM KOH (31–45 min)

Flow Rate: 0.015 mL/min Inj. Volume: 0.4 µLColumn Temp.: 30 °CIC Cube Temp.: 15 °CDetection: Suppressed conductivity, Dionex ACES 300Sample Prep.: Diluted 10-fold, filtered, 0.2 µmPeaks:

1. Quinate 11. Unknown2. Glycolate 12. Malate3. Lactate 13. Maleate4. Acetate 14. Unknown5. Formate 15. Sulfate6. Pyruvate 16. Oxalate7. Galacturonate 17. Phosphate8. Chloride 18. Citrate9. Nitrate 19. Isocitrate

10. Glutarate 20. Unknown

FIGURE 4. Determination of inorganic anions and organic acids in an orange juice sample on a 0.4 mm i.d. Dionex IonPac AS11-HC-4µm column

Figure 4 shows the separation of 20 analytes in a diluted, filtered orange juice sample on the capillary Dionex IonPac AS11-HC-4µm column using the Dionex ICS-4000 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.

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Columns: Dionex IonPac AS11-HC-4µm column set, 2 × 250 mm

Instrument: Dionex ICS-5000+ HPIC high-pressure systemEluent Source: Dionex EGC 500 KOH cartridgeGradient : 1 mM (-10 to 8 min), 1–30 mM (8–28 min),

3–72 mM (28– 38 min), 72–100 mM (38–70 min )

Flow Rate: 0.38 mL/minInj. Volume: 5 µLColumn Temp.: 30 °CDetection: Suppressed conductivity, Dionex AERS 500,

2 mm, recycle mode

Peaks: mg/L mg/L1. Fluoride 2 9. Carbonate 502. Acetate 10 10. Sulfite 1003. Propionate 10 11. Sulfate 1004. Formate 10 12. Oxalate 205. Chloride 100 13. Phosphate 206. Nitrite 10 14. Thiosulfate 107. Bromide 10 15. Thiocyanate 108. Nitrate 100

FIGURE 8. Determination of heat stable amine salts added to an amine scrubber sample of 30% methyldiethanolamine on a 2 mm i.d. Dionex IonPac AS11-HC-4µm column

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Columns: Dionex IonPac AS18-4µm column set, 2 × 150 mm

Instrument: Dionex ICS-5000+ HPIC high-pressure systemEluent Source: Dionex EGC 500 KOH cartridgeEluent: 23 mM KOH Flow Rate: 0.38 mL/minInj. Volume: 5 µLColumn Temp.: 30 °CDetection: Suppressed conductivity, Dionex AERS 500,

recycle mode, 22 mASample Prep.: 1000-fold diluted, filtered, 0.2 µm

TotalPeaks: 1. Chloride 31.1 g/L

2. Carbonate --3. Sulfate 18.3

FIGURE 7. Fast Separations of a Salton Sea surface water sample

Figure 7 demonstrates the fast separations of a diluted Salton Sea surface water sample with 20 to 30 mg/L of chloride and sulfate as injected, eluting within 5 min with resolution Rs > 2 (EP).

After the amine scrubbing process, the hydrogen sulfide and carbon dioxide gases are stripped from the amine solution as elemental sulfur and carbon dioxide. The remaining contaminants in the 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 meet discharge permit requirements. Fifteen of these anions are show below in Figure 8 with a gradient separation on a 2 mm i.d. IonPac AS11-HC-4µm column.

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 0.5 mm i.d. Dionex IonPac CS16-5µm cation-exchange column.

Column: Dionex IonPac CS16 column set, 0.5 × 250 mm

Instrument: Dionex ICS-5000+ HPIC high-pressure system Eluent Source: Dionex EGC-MSA (capillary ) cartridgeGradient : 6–8 mM MSA 0–13 min,

8–55 mM MSA 13–55 min Flow Rate: 0.014 mL/minInj. Volume: 0.4 µLColumn Temp.: 40 °CDetection: Suppressed conductivity,

Dionex CCES 300, recycle mode, 13 mASample: Amine scrubber solution spiked with

sodium, diethanolamine, and triethanolamine

Dilution: 1000-foldPeaks: 1. Sodium

2. Ethanolamine3. Diethanolamine4. Triethanolamine

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Figure 1 shows the flow diagram of a capillary HPIC system using the Dionex ICS-4000 or the ICS-5000+ HPIC system configured for capillary flow rates. The flow path is not shown for the high-pressure Dionex ICS-5000+ HPIC system configured for microboreflow rates.

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Columns: A: Dionex IonPac AS11-HC column set, 0.4 × 250 mmB: Dionex IonPac AS11-HC-4µm column set, 0.4 × 250 mm

Instrument:: Dionex ICS-5000+ HPIC capillary systemEluent Source: Dionex EGC-KOH (capillary) cartridgeGradient: 1 mM KOH (0–5 min), 1–15 mM (5–14 min),

15–30 mM (14–23 min), 30–60 mM (23–31 min)

Flow Rate: 0.015 mL/min Inj. Volume: 0.4 µLColumn Temp.: 30 °CIC Cube Temp.: 15 °CDetection: Suppressed conductivity, Dionex ACES 300Peaks:

1. Quinate 11. Monochloro- 20. Maleate2. Fluoride acetate 21. Sulfate 3. Lactate 12. Bromate 22. Oxalate 4. Acetate 13. Chloride 23. Tungstate 5. Propionate 14. Nitrite 24. Phosphate 6. Formate 15. Trifluoroacetate 25. Phthalate 7. Butyrate 16. Bromide 26. Citrate 8. Methylsulfonate 17. Nitrate 27. Chromate 9. Pyruvate 18. Carbonate 28. cis-Aconitate

10. Valerate 19. Malonate 29. trans-Aconitate

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Columns: Dionex IonPac AS18-4µm column set2 × 150 mm

Instrument: Dionex ICS-5000+ HPIC high-pressure system Eluent Source: Dionex EGC 500 KOH cartridgeEluent: 23 mM KOHFlow Rate: A: 0.25, B: 0.30, C: 0.38 mL/minInj. Volume: 5 µLColumn Temp.: 30 °CDetection: Suppressed conductivity, Dionex

AERS 500, recycle mode, A: 15, B: 26, C: 32 mA

Peaks: 1. Fluoride 0.5 mg/L2. Chlorite 0.13. Chloride 3.04. Nitrite 5.05. Carbonate ---6. Bromide 20.07. Sulfate 10.08. Nitrate 10.09. Chlorate 10.0

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EGC


DegasModule Pump

Regen

CD

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CESSuppressor


loop

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Syringe

Needle

Tray carousel

Or CRD Bypass

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Instruments












Eluent Source:






EGC


DegasModule Pump

Regen

CD

CRD200

Regen

Regen**

CESSuppressor


loop

Regen**



Syringe

Needle

Tray carousel

Or CRD Bypass

Columns
























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DegasModule Pump

Regen

CD

CRD200

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CESSuppressor


loop

Regen**



Syringe

Needle

Tray carousel

Or CRD Bypass

Columns
























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EAS2013_PN70894_E 08/16S

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Fast Ion Determinations and Effi cient Separations of...

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