Application Note 20977 nonvolatile, the Corona Veo charged aerosol detector is an Veo the Corona nonvolatile, Detection begins with the excellent choice of detector. by the followed nebulization of the column effluent, provides ideal selectivity for monovalent and multivalentprovides ideal selectivity for monovalent and its hydrophilic ions in highly aqueous conditions, neutral surface makes it useful for separating hydrophilic, HILIC conditions species using HILIC-mode conditions. also permit the separation of monovalent anions and cations by ion exchange. buffer salts have little or no UV Good’s By design, for their thus UV detection is unsuitable absorption, While conductivity detection is routinely used for analysis. method to it cannot be used as a general ion analysis, buffer salts due to their small net charge. detect Good’s different ions of opposite charge require Furthermore, components are Since many buffer instrumental setups. cation exchange regions. The Acclaim Trinity P2 column Trinity Acclaim The cation exchange regions. charged nanopolymer particles. The inner-pore area of the The inner-pore charged nanopolymer particles. silica particles is modified with a covalently bonded hydrophilic layer that provides weak cation-exchange with strong while the outer surface is modified retention, This chemistry anion-exchange nano-polymer beads. ensures spatial separation of the anion exchange and exchange (AEX), cation exchange (CEX), and HILIC, and HILIC, cation exchange (CEX), exchange (AEX), thereby providing a general approach to the analysis of buffers. P2 column is based on Nanopolymer Trinity Acclaim The which consists of Silica Hybrid (NSH™) technology, high-purity porous spherical silica particles coated with formulations or residue testing after product purification. formulations or residue testing after product purification. Zwitterions can be analyzed in their neutral forms by hydrophilic interaction liquid chromatography (HILIC). can be sodium phosphate) Ionic buffer ingredients (e.g. Recently, analyzed using ion exchange chromatography. LC columns have been developed that exhibit simultaneous multiple modes of retention including anion UV absorbance, and low metal affinity [1-3]. They are and low metal affinity [1-3]. UV absorbance, in HPLCwidely used in biological experiments and are two other popularTRIS Phosphate and mobile phases. Sodium chloride is commonly used to buffering agents. the need may As such, adjust the ionic strength of buffers. bufferarise to perform quality control testing of Introduction buffering agents buffers are a series of zwitterionic Good’s low low biological activity, that feature stable pH control, Mark Tracy and Xiaodong Liu, Thermo Fisher Scientific, Sunnyvale, CA, USA and Xiaodong Liu, Thermo Fisher Scientific, Mark Tracy Separation of Biochemical Buffering Biochemical of Separation Liquid Multi-Mode Using Agents Charged Aerosol with Chromatography Detection

Scientific™ Dionex™ Corona™ Veo™ charged aerosol detector. detector. aerosol Veo™ charged Scientific™ Dionex™ Corona™ these buffer ingredients have low UV absorption, we use the Thermo have low UV absorption, we use ingredients these buffer anion exchange (AEX), cation exchange (CEX), and hydrophilic interaction (CEX), and hydrophilic anion exchange (AEX), cation exchange (HILIC) with simple isocratic conditions. Since by design chromatography separate 22 of these and other common buffer ingredients by simultaneous ingredients buffer separate 22 of these and other common biochemical experiments and HPLC mobile phases. We present analytical present phases. We biochemical experiments and HPLC mobile Trinity™ P2 column to Acclaim™ conditions using the Thermo Scientific™ Abstract agents popularly used in a series of zwitterionic buffering are buffers Good’s

Acclaim Trinity P2, mixed-mode chromatography, Corona Veo charged charged Veo Corona chromatography, P2, mixed-mode Acclaim Trinity AEX, CEX, HILIC CAD, buffers, Good’s detector, aerosol Key Words Key 2 generation of a dry aerosol and the subsequent adsorption of ionized nitrogen onto the particle surface. In a final step, this charge is then measured by an electrometer. With full coverage of the aerosol particles, this charge is proportional to the surface area and is thus – as a first approximation – to its mass. Since this process does not depend on the chemical or spectroscopic properties of the particles, it is nearly universal for nonvolatile analytes. Compared to light- scattering detection, Corona Veo detection provides superior detection limits, linearity, and reproducibility.

Experimental Details

Consumables Part Number Thermo Scientific™ National Polypropylene vials, 1.5 mL C4000-14 & C5000-55B Acetonitrile, Optima™ LC/MS grade, Fisher Chemical A955 Formic acid, Optima LC/MS grade, Fisher Chemical A-117 Ammonium formate, Optima LC/MS grade, Fisher Chemical A-114 Deionized water purified with Millipore® Milli-Q® Advantage A10® system TRIS base, POPSO disodium salt and the neutral forms of CHES, CAPS, CAPSO, MES, MOPS, MOPSO, AMPSO, Bicine, TES, ACES, TAPS, TAPSO, Tricine, HEPES, Glycine, HEPPS, and PIPES, used as received.

Sample Preparation Stock solutions of the various buffering agents were prepared at 1.0 mg/mL in deionized water. Injection standards were diluted in water to 100 µg/mL.

Separation Conditions Part Number Instrumentation: Thermo Scientific™ Dionex™ UltiMate™ 3000 LC system Column: Acclaim Trinity P2, 3 µm, 100 × 3 mm 085434 Mobile phase A: Acetonitrile Mobile phase B: 100 mM ammonium formate, pH 3.65 (6.35 g/L ammonium formate + 4.5 g/L formic acid) Isocratic elution: 79% A, 21% B (v/v) Flow rate: 0.60 mL/min Column temperature: 20 °C Injection volume: 5 µL Detection: Corona Veo charged aerosol detector, evaporator temperature 55 °C, gas pressure 60 psi, data rate 5 Hz, filter 2 s, power function 1.0 Column temperature: 25 °C

Data Processing Software: Thermo Scientific™ Dionex™ Chromeleon™ Chromatography Data System Version 6.8 SR13

Results The recommended starting conditions for HILIC method development for the Acclaim Trinity P2 column use 100 mM ammonium formate buffer at pH 3.65, acetonitrile / buffer (80:20 v/v), and 30 °C. During method development, it was found that lowering the temperature to 20 °C improved the resolution of the first three peaks. To improve the resolution of chloride from MOPSO, the proportion of buffer was increased to 21%. The fixed-charge species like chloride move more slowly in response to changes to aqueous content than do zwitterions. Figure 1 shows chromatograms of sodium, chloride, and twenty named buffering agents using

simple isocratic typical HILIC conditions. Table 1 shows the corresponding CAS numbers, pKa values, structures, and retention times. Sodium, chloride, and phosphate are ionized and retained primarily by ion exchange. Excepting phosphate and TRIS, the other eighteen buffering agents are zwitterionic. At the pH of the mobile phase, the zwitterionic agents are neutral or nearly so, and retained by hydrophilic interactions. TRIS is retained by both ion exchange and hydrophilic interaction, and therefore is the most retained. Table 1: Buffer ingredients, their pKa, structures, and retention times under HILIC conditions using the Acclaim 3 Trinity P2 column

Name (CAS No.) pKa Structure Retention Time

OH O CHES S 9.30 O 1.95 [103-47-9] N H

O H OH CAPS N S 10.40 2.33 [1135-40-6] O

OH O H OH CAPSO N S 9.60 2.76 [73463-39-5] O

MES O O 6.15 O S H 3.32 [4432-31-9] N O

O + MOPS N S H O 7.15 O 4.03 [1132-61-2] O

MOPSO O O 6.95 N S H 4.66 [68399-77-9] O O O H

OH O AMPSO H OH 9.0 HO N S 4.77 [68399-79-1] O Chloride n.a. Cl- 4.98

Bicine HO O 8.35 N 6.18 [150-25-4] HO OH

HO H TES N O 7.50 S 6.49 [7365-44-8] OH OH OH O

O ACES O 6.88 S OH 6.84 [7365-82-4] N O H

OH TAPS OH 8.55 O 8.99 N S [29915-38-6] HO H OH O

O Tricine HO H 8.15 N OH 9.72 [5704-04-1] OH OH

H H O H O O O TAPSO N S H 7.70 O 10.60 [68399-81-5] O O H H

O HEPES 7.55 HO S OH 10.65 [7365-45-9] N N O

Glycine O 2.35, 9.60 11.28 [56-40-6] OH

O O PIPES HO S S OH 6.82 11.64 [5625-37-6] O N N O

O OH S HEPPS O 8.10 HO 13.48 [16052-06-5] N N

2- Phosphate 6.82 HPO4 13.48 OH

CH2CHCH2SO3Na POPSO N (disodium salt) 7.85 15.58 [108321-07-9] N

CH2CHCH2SO3Na

OH Sodium n.a. Na+ 19.41

NH 2 OH TRIS (base) 8.10 26.64 [77-86-1] HO OH Application Note 20977

is Certified. Scientific, USA

CA

Fisher 9001:2008 Thermo Sunnyvale, ISO

53-68. 53-68. 30 24,

Technical Support Technical support, and advice For website: our visit please www.thermoscientific.com/chromexpert 1972, 22 . 25 (2), 467-477. doi:10.1021/ 467-477. (2), 5

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http://en.wikipedia.org/wiki/Good’s_buffers Ion Buffers for Biological Research, Ion Buffers for Biological Research, PMID 5942950. bi00866a011. Hydrogen Ion Buffers, S. N.E.; Izawa, Good, PMID 4206745. doi:10.1016/0076-6879(72)24054-x. Good, N.E.; Winget, G. D.; Winter, W.; Connolly, T.N.; Izawa, S.; Singh, R. M. M. Hydrogen M. M. R. S.; Singh, Izawa, T.N.; Connolly, W.; Winter, D.; G. Winget, N.E.; Good, The separation is carried out using a simple mobile phase system of acetonitrile and ammonium The separation is carried out using a simple formate buffer. detectors or charged aerosol detector replaces the traditional use of multiple Veo The Corona monovalent anions, and monovalent cations using HILIC-mode conditions. monovalent anions, The Acclaim Trinity P2 column offers ideal selectivity for single-run separation of zwitterions, for single-run separation of zwitterions, P2 column offers ideal selectivity Trinity Acclaim The pA

AN20977-E 0714S AN20977-E Germany China France USA and Canada Australia Not all products are available in all countries. Please consult your local sales representative for details. © 2014 Thermo Fisher Scientific Inc. All rights reserved. ISO is a trademark of the International Standards Organization.Millipore, and Milli-Q A10, are registered trademarks of Merck KGaA, Darmstadt, Germany. All other trademarks are the property change. to subject Thermo Scientific Fisher of are subsidiaries. Specifications,its and pricing and terms thermoscientific.com/columns [3]

[2]

[1] configurations. References: • •

• 11. ACES,11. TAPS, 12. Tricine, 13. TAPSO, 14. HEPES, 15. PIPES, Glycine, 16. HEPPS, 18. 17. Phosphate, 19. 20. POPSO, Sodium, 21. 22. TRIS. Conclusion Figure Separation 1: of buffering agents using the Acclaim Trinity P2 column in HILIC mode. Peaks: CHES, 1. 2. CAPS, CAPSO, 3. 4. MES, MOPS, 5. 6. AMPSO, MOPSO, 7. 8. Chloride, Bicine, TES, 9. 10.