Using Capillary IC with Suppressed Conductivity and Charge Detection to Profile Organic Acids in Juices and BeveragesHua Yang, Terri Christison, Linda Lopez Thermo Fisher Scientific, Sunnyvale, CA, USA

2 Using Capillary IC with Suppressed Conductivity and Charge Detection to Profile Organic Acids in Juices and Beverages

Using Capillary IC with Suppressed Conductivity and Charge Detection to Profile Organic Acids in Juices and Beverages Hua Yang, Terri Christison, Linda Lopez Thermo Fisher Scientific, Sunnyvale, CA, USA

Conclusion The QD Charge Detector offered on the Dionex ICS-4000 HPIC system improves sample analysis and reporting reliability by:

Detecting peaks previously not detected by CD.

Identifying doubly and triply charged ions from the proportionally higher response than the singly charged ions.

Providing more linear response and proportionally higher responses for weakly ionized than strongly ionized compounds by CD

Detecting co-eluting peaks by the proportionally higher responses of multi-charged ions than singly charged ions.

References 1. Srinivasan, K., PhD. High Pressure Ion Chromatography Charge Detection,

webinar, October 2012. Thermo Fisher Scientific, Sunnyvale, CA, 2013.

2. Basumallick, L., PhD. Analysis of Carbohydrates & Organic Acids Using Capillary IC Methods, webinar, February 2013. Thermo Fisher Scientific, Sunnyvale, CA, 2013.

3. Verma, M. What is Charge Detection? White paper, WP70585_E 03/13S. Thermo Fisher Scientific, Sunnyvale, CA, 2013.

Overview Purpose: To demonstrate the advantages of using QD Charge detection for Ion Chromatography (IC).

Methods: Inorganic anions and organic acids were separated on a high-capacity 4 µm particle Thermo Scientific™ Dionex™ IonPac™ AS11-HC-4µm capillary column and detected with suppressed conductivity in series with charge detection. Analysis was facilitated by a high-pressure capillary IC system.

Results: Very high efficient separations at > 3500 psi system pressures were demonstrated on the Dionex IonPac AS11-HC-4µm on a dedicated capillary IC system. The QD charge detector shows comparably higher charge response for organic acids than for chloride and sulfate and can detect other peaks previously not detected by conductivity (CD). CD/QD ratios were used to assess peak purity, thereby improving reporting accuracy.

Introduction Determinations of organic acid profiles in fruit juices are important in the beverage industry to ascertain product quality and to meet labeling requirements for food products. Ion chromatography with suppressed conductivity is the ideal analytical method for ionic analytes. However organic acids which are weakly ionized can exhibit lower conductivity responses versus concentration than strongly ionized anions, such as chloride and sulfate. However, the new Thermo Scientific Dionex QD Charge Detector promotes complete dissociation of even weakly ionized compounds.

Methods Sample Preparation Commercial juice samples were diluted and filtered (0.2 µm) with a syringe filter.

Ion Chromatography Instrumentation (Figure 1) Thermo Scientific™ Dionex™ ICS-4000 HPIC™ dedicated capillary IC system with • Dionex IonPac ASTC-500 trap column • Thermo Scientific Dionex Conductivity Detection (CD) detector • Thermo Scientific Dionex QD Charge Detector Cell (QDC) • Thermo Scientific Dionex AS-AP Autosampler

All trademarks are the property of Thermo Fisher Scientific 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.

Column set: Dionex IonPac AS11-HC-4µm, guard and separation columns, 0.4 mm i.d.

Eluent Source: Thermo Scientific Dionex EGC-KOH capillary cartridge with Thermo Scientific Dionex CR-ATC capillary trap column

Gradient: Potassium hydroxide, listed in figures.

Flow Rate: 0.015 mL/min

Inj. Volume: 0.4 µL

Column Temp.: 30 C

Detection: A: Suppressed conductivity, Thermo Scientific™ Dionex™ ACES™ Anion Capillary Electrolytic Suppressor, recycle mode, Thermo Scientific Dionex CRD 180 Carbonate Removal Device. B: QD Charge Detection, Dionex QDC cell, 6 V, recycle mode.

Typical System Pressure:

3600 psi

TABLE 1. IC conditions for beverage analysis.

Results QD Charge Detection A charge detector (QD) is a constant voltage membrane device that maintains a specified potential at the anode and cathode (Figure 2).1 As the sample passes through the detector, the ions are drawn through the ion-exchange membranes, drawing a current to balance the charge. This results in a response proportional to the charge state and a significantly higher response for weakly ionized compounds than would be obtained with CD.

Data Analysis Thermo Scientific™ Dionex™ Chromeleon™ Chromatography Data System (CDS) software

FIGURE 2. Mechanisms of Dionex charge detection.

0 5 10 15 20 25Time/ min

120

140

160

180

Ca

pa

cit

an

ce

/ f

F

IO3-

BrO3-

NO3-NO2-

I-

Br-

0 5 10 15 20 25Time/ min

120

140

160

180

Cap

acita

nce

/ fF

IO3-

BrO3-

NO3-NO2-

I-

Br-

Signal total charges

AX CX (+) (-)

H2O

HY A+ Y-

AOH

Charge detection can be used to estimate concentration.1 In charge detection, all the salts and acids with the same equivalency have similar responses (Figure 3) as compared with conductance where the salts have lower response.

0 20 40 60Time, min

28

28.4

28.8

29.2

29.6

30

Curre

nt,

A

HClO4CH3SO3HHNO3

KClNaCl

NaNO3 Specific Conductance (S/cm/mM) HNO3 = 421 CH3SO3H = 380 HClO4 = 418 NaNO3 = 121

FIGURE 3. Conductance versus charge detection.

Figure 4 shows increased linear response for weakly ionized analytes with charge detection.1

Fluoride (Pka 3.17)

R² = 1 0

50

0 20 40 60 80 100 120

R² = 0.9999 0

20

0 20 40 60 80 100 120

Chloride

R² = 1 0

100

0 20 40 60 80 100 120

Formate (Pka 3.75)

R² = 0.9999

-20

0

20

0 50 100 150

R² = 0.9998

-10

0

10

0 20 40 60 80 100 120

Chloride

R² = 0.9997

-10

0

10

0 50 100 150

Fluoride (Pka 3.17)

Formate (Pka 3.75)

FIGURE 4A. FIGURE 4B.

FIGURE 4. Compares CD (A) and QD (B) responses with concentration.

3

7 2 5,6

4 13

1

15

12

11

Minutes 0 45 30 10 40 20 -5

µA*

30

µS

-10

100

A B

8

9 10

16

19

18

14 17

20

Peaks: 15. Sulfate 16. Oxalate 17. Phosphate 18. Citrate 19. Isocitrate 20. Unknown

FIGURE 9. Comparing CD to QD in a diluted orange juice sample to identify co-elution and detect additional peaks.

FIGURE 1. Dionex ICS-4000 Capillary HPIC system (FIGURE 1A), Dionex IC Cube with CD and QD Detectors (FIGURE 1C), Dionex QDC Charge Detector Cell (FIGURE 1C).

1A.

1B.

1C.

Figure 8 shows the QD chromatogram normalized at the chloride peak and overlaid on the CD chromatogram of a diluted guava juice sample.2 The chromatograms show a higher proportional charge with QD than CD for organic acids in diluted guava juice.

FIGURE 8. Comparison of QD to CD responses in diluted guava juice.

µS 3

6

2

5 4 13

Minutes 0 45

-20 30 10 40 20

90

1

7

8

9

10

11

12

µA*

-2

8

A B

Detection: A: Suppressed conductivity, Dionex ACES 300 suppressor, recycle B: QD Charge Detection, *normalized to chloride peak

Sample Prep.: Diluted 5-fold, filtered, 0.2 µm Peaks: 1. Quinate 8. Malate- 2. Lactate Succinate 3. Acetate 9. Sulfate 4. Glycolate 10. Oxalate 5. Propionate 11. Phosphate 6.Formate 12. Citrate 7. Chloride 13. Isocitrate

Columns: Dionex IonPac AS11-HC-4µm column set, 0.4 mm Eluent Source: Dionex EGC-KOH capillary cartridge Gradient: 1 mM KOH (5 min), 1–15 mM KOH (5–15 min), 15–30 mM KOH (15–23 min), 30–60 mM KOH (23–31 min), 60 mM KOH (31–45 min)

Eluent Source: EGC-KOH capillary Gradient: 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)

Detection: A: Suppressed conductivity, Dionex ACES 300 suppressor, recycle mode B: QD Charge Detection, *normalized to chloride peak

Sample Prep.: Diluted 10-fold, filtered, 0.2 µm

Peaks: 1. Quinate 2. Glycolate 3. Lactate 4. Acetate 5. Formate 6. Pyruvate 7. Galacturonate

Concentration

Res

pons

e (µ

S*m

in)

A

B

C1

R2

R1

CD

Res

pons

e (µ

A*m

in)

C1

R3

QD

A or B

Res

pons

e (µ

A*m

in)

C1 C2

R2

R3

QD Confirms A or B

Concentration

Res

pons

e (µ

S*m

in)

A

B

C1 C2

R1

CD

FIGURE 5. Compares CD (A) and QD (B) responses with concentration. FIGURE 5A. Same response. FIGURE 5B. Different response.

Gradient + 1 mM KOH (0–8 min), 10% Methanol*: 1–15 mM (8–18 min), 15–30 mM (18–28 min), 30–60 mM (8–18 min)

0 10 20 30 40 45 -10

10

µS

Minutes

1

2 3 4 5 6,7

8 9

10

11

12

13 14

15

16,17 19

20

21 22

23 24

25

Apple

Standard

Cranberry

Concentration

Figures 5 and 6 show the advantages of using different detectors. In Figure 5, both analytes have the same response (R1) by CD but could have different responses/concentration (C1 or C2), making peak selection problematic. However, the QD response (R2, R3) confirms the concentration of each analyte (A = C1, B = C2).

In Figure 6, both analytes have the same response (R3) by QD but different responses by CD, confirming C1 concentration by both modes.

FIGURE 6. Compares CD (A) and QD (B) responses with concentration. FIGURE 6A. Different response. FIGURE 6B. Same response.

Concentration

Confirms C1

Peaks (Standard): mg/L 1. Quinate 1 2. Fluoride 0.6 3. Lactate 1 4. Acetate 1 5. Propionate 1 6. Formate 1 7. Butyrate 1 8. Pyruvate 2 9. Galacturonate 2

Detection: Suppressed Conductivity, Dionex ACES 300 suppressor, external water mode Sample: Juice, 50-fold sample dilution

FIGURE 7. Profiling organic acids to identify adulteration.

mg/L 18. Sulfate 2 19. Fumarate 2 20. Oxalate 2 21. Phosphate 3 22. Citrate 3 23. Isocitrate 3 24. cis-Aconitate -- 25. trans-Aconitate 3

Figure 7 demonstrates profiling of organic acids using CD to identify adulteration of a higher cost juice with a lower cost juice to increase profits. Cranberry juice with characteristic quinate peak (1) can easily be distinguished from the lower cost apple juice with malate peak (14).

mg/L 10.Chloride 1 11.Bromide 1 12.Nitrate 1 13. Glutarate 2 14. Succinate 2 15. Malate 2 16. Carbonate -- 17. Tartrate 2

Figure 9 shows misidentified nitrate peak by retention time alone. CD and QD responses (circle) indicate that the peak is likely a multi-charged organic acid. QD (boxes) response (boxes) show peaks previously unidentified by CD. increased linear response for weakly ionized analytes with charge detection.1

Peaks: 8. Chloride 9. Nitrate ? 10. Glutarate 11. Unknown 12. Malate 13. Maleate 14. Unknown

18

PO71296-EN 0914S

3Thermo Scientific Poster Note • PN-71296-AOAC-EN 0914S

Using Capillary IC with Suppressed Conductivity and Charge Detection to Profile Organic Acids in Juices and Beverages Hua Yang, Terri Christison, Linda Lopez Thermo Fisher Scientific, Sunnyvale, CA, USA

Conclusion The QD Charge Detector offered on the Dionex ICS-4000 HPIC system improves sample analysis and reporting reliability by:

Detecting peaks previously not detected by CD.

Identifying doubly and triply charged ions from the proportionally higher response than the singly charged ions.

Providing more linear response and proportionally higher responses for weakly ionized than strongly ionized compounds by CD

Detecting co-eluting peaks by the proportionally higher responses of multi-charged ions than singly charged ions.

References 1. Srinivasan, K., PhD. High Pressure Ion Chromatography Charge Detection,

webinar, October 2012. Thermo Fisher Scientific, Sunnyvale, CA, 2013.

2. Basumallick, L., PhD. Analysis of Carbohydrates & Organic Acids Using Capillary IC Methods, webinar, February 2013. Thermo Fisher Scientific, Sunnyvale, CA, 2013.

3. Verma, M. What is Charge Detection? White paper, WP70585_E 03/13S. Thermo Fisher Scientific, Sunnyvale, CA, 2013.

Overview Purpose: To demonstrate the advantages of using QD Charge detection for Ion Chromatography (IC).

Methods: Inorganic anions and organic acids were separated on a high-capacity 4 µm particle Thermo Scientific™ Dionex™ IonPac™ AS11-HC-4µm capillary column and detected with suppressed conductivity in series with charge detection. Analysis was facilitated by a high-pressure capillary IC system.

Results: Very high efficient separations at > 3500 psi system pressures were demonstrated on the Dionex IonPac AS11-HC-4µm on a dedicated capillary IC system. The QD charge detector shows comparably higher charge response for organic acids than for chloride and sulfate and can detect other peaks previously not detected by conductivity (CD). CD/QD ratios were used to assess peak purity, thereby improving reporting accuracy.

Introduction Determinations of organic acid profiles in fruit juices are important in the beverage industry to ascertain product quality and to meet labeling requirements for food products. Ion chromatography with suppressed conductivity is the ideal analytical method for ionic analytes. However organic acids which are weakly ionized can exhibit lower conductivity responses versus concentration than strongly ionized anions, such as chloride and sulfate. However, the new Thermo Scientific Dionex QD Charge Detector promotes complete dissociation of even weakly ionized compounds.

Methods Sample Preparation Commercial juice samples were diluted and filtered (0.2 µm) with a syringe filter.

Ion Chromatography Instrumentation (Figure 1) Thermo Scientific™ Dionex™ ICS-4000 HPIC™ dedicated capillary IC system with • Dionex IonPac ASTC-500 trap column • Thermo Scientific Dionex Conductivity Detection (CD) detector • Thermo Scientific Dionex QD Charge Detector Cell (QDC) • Thermo Scientific Dionex AS-AP Autosampler

All trademarks are the property of Thermo Fisher Scientific 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.

Column set: Dionex IonPac AS11-HC-4µm, guard and separation columns, 0.4 mm i.d.

Eluent Source: Thermo Scientific Dionex EGC-KOH capillary cartridge with Thermo Scientific Dionex CR-ATC capillary trap column

Gradient: Potassium hydroxide, listed in figures.

Flow Rate: 0.015 mL/min

Inj. Volume: 0.4 µL

Column Temp.: 30 C

Detection: A: Suppressed conductivity, Thermo Scientific™ Dionex™ ACES™ Anion Capillary Electrolytic Suppressor, recycle mode, Thermo Scientific Dionex CRD 180 Carbonate Removal Device. B: QD Charge Detection, Dionex QDC cell, 6 V, recycle mode.

Typical System Pressure:

3600 psi

TABLE 1. IC conditions for beverage analysis.

Results QD Charge Detection A charge detector (QD) is a constant voltage membrane device that maintains a specified potential at the anode and cathode (Figure 2).1 As the sample passes through the detector, the ions are drawn through the ion-exchange membranes, drawing a current to balance the charge. This results in a response proportional to the charge state and a significantly higher response for weakly ionized compounds than would be obtained with CD.

Data Analysis Thermo Scientific™ Dionex™ Chromeleon™ Chromatography Data System (CDS) software

FIGURE 2. Mechanisms of Dionex charge detection.

0 5 10 15 20 25Time/ min

120

140

160

180

Ca

pa

cit

an

ce

/ f

F

IO3-

BrO3-

NO3-NO2-

I-

Br-

0 5 10 15 20 25Time/ min

120

140

160

180

Cap

acita

nce

/ fF

IO3-

BrO3-

NO3-NO2-

I-

Br-

Signal total charges

AX CX (+) (-)

H2O

HY A+ Y-

AOH

Charge detection can be used to estimate concentration.1 In charge detection, all the salts and acids with the same equivalency have similar responses (Figure 3) as compared with conductance where the salts have lower response.

0 20 40 60Time, min

28

28.4

28.8

29.2

29.6

30

Curre

nt,

A

HClO4CH3SO3HHNO3

KClNaCl

NaNO3 Specific Conductance (S/cm/mM) HNO3 = 421 CH3SO3H = 380 HClO4 = 418 NaNO3 = 121

FIGURE 3. Conductance versus charge detection.

Figure 4 shows increased linear response for weakly ionized analytes with charge detection.1

Fluoride (Pka 3.17)

R² = 1 0

50

0 20 40 60 80 100 120

R² = 0.9999 0

20

0 20 40 60 80 100 120

Chloride

R² = 1 0

100

0 20 40 60 80 100 120

Formate (Pka 3.75)

R² = 0.9999

-20

0

20

0 50 100 150

R² = 0.9998

-10

0

10

0 20 40 60 80 100 120

Chloride

R² = 0.9997

-10

0

10

0 50 100 150

Fluoride (Pka 3.17)

Formate (Pka 3.75)

FIGURE 4A. FIGURE 4B.

FIGURE 4. Compares CD (A) and QD (B) responses with concentration.

3

7 2 5,6

4 13

1

15

12

11

Minutes 0 45 30 10 40 20 -5

µA*

30

µS

-10

100

A B

8

9 10

16

19

18

14 17

20

Peaks: 15. Sulfate 16. Oxalate 17. Phosphate 18. Citrate 19. Isocitrate 20. Unknown

FIGURE 9. Comparing CD to QD in a diluted orange juice sample to identify co-elution and detect additional peaks.

FIGURE 1. Dionex ICS-4000 Capillary HPIC system (FIGURE 1A), Dionex IC Cube with CD and QD Detectors (FIGURE 1C), Dionex QDC Charge Detector Cell (FIGURE 1C).

1A.

1B.

1C.

Figure 8 shows the QD chromatogram normalized at the chloride peak and overlaid on the CD chromatogram of a diluted guava juice sample.2 The chromatograms show a higher proportional charge with QD than CD for organic acids in diluted guava juice.

FIGURE 8. Comparison of QD to CD responses in diluted guava juice.

µS 3

6

2

5 4 13

Minutes 0 45

-20 30 10 40 20

90

1

7

8

9

10

11

12

µA*

-2

8

A B

Detection: A: Suppressed conductivity, Dionex ACES 300 suppressor, recycle B: QD Charge Detection, *normalized to chloride peak

Sample Prep.: Diluted 5-fold, filtered, 0.2 µm Peaks: 1. Quinate 8. Malate- 2. Lactate Succinate 3. Acetate 9. Sulfate 4. Glycolate 10. Oxalate 5. Propionate 11. Phosphate 6.Formate 12. Citrate 7. Chloride 13. Isocitrate

Columns: Dionex IonPac AS11-HC-4µm column set, 0.4 mm Eluent Source: Dionex EGC-KOH capillary cartridge Gradient: 1 mM KOH (5 min), 1–15 mM KOH (5–15 min), 15–30 mM KOH (15–23 min), 30–60 mM KOH (23–31 min), 60 mM KOH (31–45 min)

Eluent Source: EGC-KOH capillary Gradient: 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)

Detection: A: Suppressed conductivity, Dionex ACES 300 suppressor, recycle mode B: QD Charge Detection, *normalized to chloride peak

Sample Prep.: Diluted 10-fold, filtered, 0.2 µm

Peaks: 1. Quinate 2. Glycolate 3. Lactate 4. Acetate 5. Formate 6. Pyruvate 7. Galacturonate

Concentration

Res

pons

e (µ

S*m

in)

A

B

C1

R2

R1

CD

Res

pons

e (µ

A*m

in)

C1

R3

QD

A or B

Res

pons

e (µ

A*m

in)

C1 C2

R2

R3

QD Confirms A or B

Concentration

Res

pons

e (µ

S*m

in)

A

B

C1 C2

R1

CD

FIGURE 5. Compares CD (A) and QD (B) responses with concentration. FIGURE 5A. Same response. FIGURE 5B. Different response.

Gradient + 1 mM KOH (0–8 min), 10% Methanol*: 1–15 mM (8–18 min), 15–30 mM (18–28 min), 30–60 mM (8–18 min)

0 10 20 30 40 45 -10

10

µS

Minutes

1

2 3 4 5 6,7

8 9

10

11

12

13 14

15

16,17 19

20

21 22

23 24

25

Apple

Standard

Cranberry

Concentration

Figures 5 and 6 show the advantages of using different detectors. In Figure 5, both analytes have the same response (R1) by CD but could have different responses/concentration (C1 or C2), making peak selection problematic. However, the QD response (R2, R3) confirms the concentration of each analyte (A = C1, B = C2).

In Figure 6, both analytes have the same response (R3) by QD but different responses by CD, confirming C1 concentration by both modes.

FIGURE 6. Compares CD (A) and QD (B) responses with concentration. FIGURE 6A. Different response. FIGURE 6B. Same response.

Concentration

Confirms C1

Peaks (Standard): mg/L 1. Quinate 1 2. Fluoride 0.6 3. Lactate 1 4. Acetate 1 5. Propionate 1 6. Formate 1 7. Butyrate 1 8. Pyruvate 2 9. Galacturonate 2

Detection: Suppressed Conductivity, Dionex ACES 300 suppressor, external water mode Sample: Juice, 50-fold sample dilution

FIGURE 7. Profiling organic acids to identify adulteration.

mg/L 18. Sulfate 2 19. Fumarate 2 20. Oxalate 2 21. Phosphate 3 22. Citrate 3 23. Isocitrate 3 24. cis-Aconitate -- 25. trans-Aconitate 3

Figure 7 demonstrates profiling of organic acids using CD to identify adulteration of a higher cost juice with a lower cost juice to increase profits. Cranberry juice with characteristic quinate peak (1) can easily be distinguished from the lower cost apple juice with malate peak (14).

mg/L 10.Chloride 1 11.Bromide 1 12.Nitrate 1 13. Glutarate 2 14. Succinate 2 15. Malate 2 16. Carbonate -- 17. Tartrate 2

Figure 9 shows misidentified nitrate peak by retention time alone. CD and QD responses (circle) indicate that the peak is likely a multi-charged organic acid. QD (boxes) response (boxes) show peaks previously unidentified by CD. increased linear response for weakly ionized analytes with charge detection.1

Peaks: 8. Chloride 9. Nitrate ? 10. Glutarate 11. Unknown 12. Malate 13. Maleate 14. Unknown

18

PO71296-EN 0914S

4 Using Capillary IC with Suppressed Conductivity and Charge Detection to Profile Organic Acids in Juices and Beverages

Using Capillary IC with Suppressed Conductivity and Charge Detection to Profile Organic Acids in Juices and Beverages Hua Yang, Terri Christison, Linda Lopez Thermo Fisher Scientific, Sunnyvale, CA, USA

Conclusion The QD Charge Detector offered on the Dionex ICS-4000 HPIC system improves sample analysis and reporting reliability by:

Detecting peaks previously not detected by CD.

Identifying doubly and triply charged ions from the proportionally higher response than the singly charged ions.

Providing more linear response and proportionally higher responses for weakly ionized than strongly ionized compounds by CD

Detecting co-eluting peaks by the proportionally higher responses of multi-charged ions than singly charged ions.

References 1. Srinivasan, K., PhD. High Pressure Ion Chromatography Charge Detection,

webinar, October 2012. Thermo Fisher Scientific, Sunnyvale, CA, 2013.

2. Basumallick, L., PhD. Analysis of Carbohydrates & Organic Acids Using Capillary IC Methods, webinar, February 2013. Thermo Fisher Scientific, Sunnyvale, CA, 2013.

3. Verma, M. What is Charge Detection? White paper, WP70585_E 03/13S. Thermo Fisher Scientific, Sunnyvale, CA, 2013.

Overview Purpose: To demonstrate the advantages of using QD Charge detection for Ion Chromatography (IC).

Methods: Inorganic anions and organic acids were separated on a high-capacity 4 µm particle Thermo Scientific™ Dionex™ IonPac™ AS11-HC-4µm capillary column and detected with suppressed conductivity in series with charge detection. Analysis was facilitated by a high-pressure capillary IC system.

Results: Very high efficient separations at > 3500 psi system pressures were demonstrated on the Dionex IonPac AS11-HC-4µm on a dedicated capillary IC system. The QD charge detector shows comparably higher charge response for organic acids than for chloride and sulfate and can detect other peaks previously not detected by conductivity (CD). CD/QD ratios were used to assess peak purity, thereby improving reporting accuracy.

Introduction Determinations of organic acid profiles in fruit juices are important in the beverage industry to ascertain product quality and to meet labeling requirements for food products. Ion chromatography with suppressed conductivity is the ideal analytical method for ionic analytes. However organic acids which are weakly ionized can exhibit lower conductivity responses versus concentration than strongly ionized anions, such as chloride and sulfate. However, the new Thermo Scientific Dionex QD Charge Detector promotes complete dissociation of even weakly ionized compounds.

Methods Sample Preparation Commercial juice samples were diluted and filtered (0.2 µm) with a syringe filter.

Ion Chromatography Instrumentation (Figure 1) Thermo Scientific™ Dionex™ ICS-4000 HPIC™ dedicated capillary IC system with • Dionex IonPac ASTC-500 trap column • Thermo Scientific Dionex Conductivity Detection (CD) detector • Thermo Scientific Dionex QD Charge Detector Cell (QDC) • Thermo Scientific Dionex AS-AP Autosampler

All trademarks are the property of Thermo Fisher Scientific 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.

Column set: Dionex IonPac AS11-HC-4µm, guard and separation columns, 0.4 mm i.d.

Eluent Source: Thermo Scientific Dionex EGC-KOH capillary cartridge with Thermo Scientific Dionex CR-ATC capillary trap column

Gradient: Potassium hydroxide, listed in figures.

Flow Rate: 0.015 mL/min

Inj. Volume: 0.4 µL

Column Temp.: 30 C

Detection: A: Suppressed conductivity, Thermo Scientific™ Dionex™ ACES™ Anion Capillary Electrolytic Suppressor, recycle mode, Thermo Scientific Dionex CRD 180 Carbonate Removal Device. B: QD Charge Detection, Dionex QDC cell, 6 V, recycle mode.

Typical System Pressure:

3600 psi

TABLE 1. IC conditions for beverage analysis.

Results QD Charge Detection A charge detector (QD) is a constant voltage membrane device that maintains a specified potential at the anode and cathode (Figure 2).1 As the sample passes through the detector, the ions are drawn through the ion-exchange membranes, drawing a current to balance the charge. This results in a response proportional to the charge state and a significantly higher response for weakly ionized compounds than would be obtained with CD.

Data Analysis Thermo Scientific™ Dionex™ Chromeleon™ Chromatography Data System (CDS) software

FIGURE 2. Mechanisms of Dionex charge detection.

0 5 10 15 20 25Time/ min

120

140

160

180

Ca

pa

cit

an

ce

/ f

F

IO3-

BrO3-

NO3-NO2-

I-

Br-

0 5 10 15 20 25Time/ min

120

140

160

180

Cap

acita

nce

/ fF

IO3-

BrO3-

NO3-NO2-

I-

Br-

Signal total charges

AX CX (+) (-)

H2O

HY A+ Y-

AOH

Charge detection can be used to estimate concentration.1 In charge detection, all the salts and acids with the same equivalency have similar responses (Figure 3) as compared with conductance where the salts have lower response.

0 20 40 60Time, min

28

28.4

28.8

29.2

29.6

30

Curre

nt,

A

HClO4CH3SO3HHNO3

KClNaCl

NaNO3 Specific Conductance (S/cm/mM) HNO3 = 421 CH3SO3H = 380 HClO4 = 418 NaNO3 = 121

FIGURE 3. Conductance versus charge detection.

Figure 4 shows increased linear response for weakly ionized analytes with charge detection.1

Fluoride (Pka 3.17)

R² = 1 0

50

0 20 40 60 80 100 120

R² = 0.9999 0

20

0 20 40 60 80 100 120

Chloride

R² = 1 0

100

0 20 40 60 80 100 120

Formate (Pka 3.75)

R² = 0.9999

-20

0

20

0 50 100 150

R² = 0.9998

-10

0

10

0 20 40 60 80 100 120

Chloride

R² = 0.9997

-10

0

10

0 50 100 150

Fluoride (Pka 3.17)

Formate (Pka 3.75)

FIGURE 4A. FIGURE 4B.

FIGURE 4. Compares CD (A) and QD (B) responses with concentration.

3

7 2 5,6

4 13

1

15

12

11

Minutes 0 45 30 10 40 20 -5

µA*

30

µS

-10

100

A B

8

9 10

16

19

18

14 17

20

Peaks: 15. Sulfate 16. Oxalate 17. Phosphate 18. Citrate 19. Isocitrate 20. Unknown

FIGURE 9. Comparing CD to QD in a diluted orange juice sample to identify co-elution and detect additional peaks.

FIGURE 1. Dionex ICS-4000 Capillary HPIC system (FIGURE 1A), Dionex IC Cube with CD and QD Detectors (FIGURE 1C), Dionex QDC Charge Detector Cell (FIGURE 1C).

1A.

1B.

1C.

Figure 8 shows the QD chromatogram normalized at the chloride peak and overlaid on the CD chromatogram of a diluted guava juice sample.2 The chromatograms show a higher proportional charge with QD than CD for organic acids in diluted guava juice.

FIGURE 8. Comparison of QD to CD responses in diluted guava juice.

µS 3

6

2

5 4 13

Minutes 0 45

-20 30 10 40 20

90

1

7

8

9

10

11

12

µA*

-2

8

A B

Detection: A: Suppressed conductivity, Dionex ACES 300 suppressor, recycle B: QD Charge Detection, *normalized to chloride peak

Sample Prep.: Diluted 5-fold, filtered, 0.2 µm Peaks: 1. Quinate 8. Malate- 2. Lactate Succinate 3. Acetate 9. Sulfate 4. Glycolate 10. Oxalate 5. Propionate 11. Phosphate 6.Formate 12. Citrate 7. Chloride 13. Isocitrate

Columns: Dionex IonPac AS11-HC-4µm column set, 0.4 mm Eluent Source: Dionex EGC-KOH capillary cartridge Gradient: 1 mM KOH (5 min), 1–15 mM KOH (5–15 min), 15–30 mM KOH (15–23 min), 30–60 mM KOH (23–31 min), 60 mM KOH (31–45 min)

Eluent Source: EGC-KOH capillary Gradient: 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)

Detection: A: Suppressed conductivity, Dionex ACES 300 suppressor, recycle mode B: QD Charge Detection, *normalized to chloride peak

Sample Prep.: Diluted 10-fold, filtered, 0.2 µm

Peaks: 1. Quinate 2. Glycolate 3. Lactate 4. Acetate 5. Formate 6. Pyruvate 7. Galacturonate

Concentration

Res

pons

e (µ

S*m

in)

A

B

C1

R2

R1

CD

Res

pons

e (µ

A*m

in)

C1

R3

QD

A or B

Res

pons

e (µ

A*m

in)

C1 C2

R2

R3

QD Confirms A or B

Concentration

Res

pons

e (µ

S*m

in)

A

B

C1 C2

R1

CD

FIGURE 5. Compares CD (A) and QD (B) responses with concentration. FIGURE 5A. Same response. FIGURE 5B. Different response.

Gradient + 1 mM KOH (0–8 min), 10% Methanol*: 1–15 mM (8–18 min), 15–30 mM (18–28 min), 30–60 mM (8–18 min)

0 10 20 30 40 45 -10

10

µS

Minutes

1

2 3 4 5 6,7

8 9

10

11

12

13 14

15

16,17 19

20

21 22

23 24

25

Apple

Standard

Cranberry

Concentration

Figures 5 and 6 show the advantages of using different detectors. In Figure 5, both analytes have the same response (R1) by CD but could have different responses/concentration (C1 or C2), making peak selection problematic. However, the QD response (R2, R3) confirms the concentration of each analyte (A = C1, B = C2).

In Figure 6, both analytes have the same response (R3) by QD but different responses by CD, confirming C1 concentration by both modes.

FIGURE 6. Compares CD (A) and QD (B) responses with concentration. FIGURE 6A. Different response. FIGURE 6B. Same response.

Concentration

Confirms C1

Peaks (Standard): mg/L 1. Quinate 1 2. Fluoride 0.6 3. Lactate 1 4. Acetate 1 5. Propionate 1 6. Formate 1 7. Butyrate 1 8. Pyruvate 2 9. Galacturonate 2

Detection: Suppressed Conductivity, Dionex ACES 300 suppressor, external water mode Sample: Juice, 50-fold sample dilution

FIGURE 7. Profiling organic acids to identify adulteration.

mg/L 18. Sulfate 2 19. Fumarate 2 20. Oxalate 2 21. Phosphate 3 22. Citrate 3 23. Isocitrate 3 24. cis-Aconitate -- 25. trans-Aconitate 3

Figure 7 demonstrates profiling of organic acids using CD to identify adulteration of a higher cost juice with a lower cost juice to increase profits. Cranberry juice with characteristic quinate peak (1) can easily be distinguished from the lower cost apple juice with malate peak (14).

mg/L 10.Chloride 1 11.Bromide 1 12.Nitrate 1 13. Glutarate 2 14. Succinate 2 15. Malate 2 16. Carbonate -- 17. Tartrate 2

Figure 9 shows misidentified nitrate peak by retention time alone. CD and QD responses (circle) indicate that the peak is likely a multi-charged organic acid. QD (boxes) response (boxes) show peaks previously unidentified by CD. increased linear response for weakly ionized analytes with charge detection.1

Peaks: 8. Chloride 9. Nitrate ? 10. Glutarate 11. Unknown 12. Malate 13. Maleate 14. Unknown

18

PO71296-EN 0914S

5Thermo Scientific Poster Note • PN-71296-AOAC-EN 0914S

Using Capillary IC with Suppressed Conductivity and Charge Detection to Profile Organic Acids in Juices and Beverages Hua Yang, Terri Christison, Linda Lopez Thermo Fisher Scientific, Sunnyvale, CA, USA

Conclusion The QD Charge Detector offered on the Dionex ICS-4000 HPIC system improves sample analysis and reporting reliability by:

Detecting peaks previously not detected by CD.

Identifying doubly and triply charged ions from the proportionally higher response than the singly charged ions.

Providing more linear response and proportionally higher responses for weakly ionized than strongly ionized compounds by CD

Detecting co-eluting peaks by the proportionally higher responses of multi-charged ions than singly charged ions.

References 1. Srinivasan, K., PhD. High Pressure Ion Chromatography Charge Detection,

webinar, October 2012. Thermo Fisher Scientific, Sunnyvale, CA, 2013.

2. Basumallick, L., PhD. Analysis of Carbohydrates & Organic Acids Using Capillary IC Methods, webinar, February 2013. Thermo Fisher Scientific, Sunnyvale, CA, 2013.

3. Verma, M. What is Charge Detection? White paper, WP70585_E 03/13S. Thermo Fisher Scientific, Sunnyvale, CA, 2013.

Overview Purpose: To demonstrate the advantages of using QD Charge detection for Ion Chromatography (IC).

Methods: Inorganic anions and organic acids were separated on a high-capacity 4 µm particle Thermo Scientific™ Dionex™ IonPac™ AS11-HC-4µm capillary column and detected with suppressed conductivity in series with charge detection. Analysis was facilitated by a high-pressure capillary IC system.

Results: Very high efficient separations at > 3500 psi system pressures were demonstrated on the Dionex IonPac AS11-HC-4µm on a dedicated capillary IC system. The QD charge detector shows comparably higher charge response for organic acids than for chloride and sulfate and can detect other peaks previously not detected by conductivity (CD). CD/QD ratios were used to assess peak purity, thereby improving reporting accuracy.

Introduction Determinations of organic acid profiles in fruit juices are important in the beverage industry to ascertain product quality and to meet labeling requirements for food products. Ion chromatography with suppressed conductivity is the ideal analytical method for ionic analytes. However organic acids which are weakly ionized can exhibit lower conductivity responses versus concentration than strongly ionized anions, such as chloride and sulfate. However, the new Thermo Scientific Dionex QD Charge Detector promotes complete dissociation of even weakly ionized compounds.

Methods Sample Preparation Commercial juice samples were diluted and filtered (0.2 µm) with a syringe filter.

Ion Chromatography Instrumentation (Figure 1) Thermo Scientific™ Dionex™ ICS-4000 HPIC™ dedicated capillary IC system with • Dionex IonPac ASTC-500 trap column • Thermo Scientific Dionex Conductivity Detection (CD) detector • Thermo Scientific Dionex QD Charge Detector Cell (QDC) • Thermo Scientific Dionex AS-AP Autosampler

All trademarks are the property of Thermo Fisher Scientific 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.

Column set: Dionex IonPac AS11-HC-4µm, guard and separation columns, 0.4 mm i.d.

Eluent Source: Thermo Scientific Dionex EGC-KOH capillary cartridge with Thermo Scientific Dionex CR-ATC capillary trap column

Gradient: Potassium hydroxide, listed in figures.

Flow Rate: 0.015 mL/min

Inj. Volume: 0.4 µL

Column Temp.: 30 C

Detection: A: Suppressed conductivity, Thermo Scientific™ Dionex™ ACES™ Anion Capillary Electrolytic Suppressor, recycle mode, Thermo Scientific Dionex CRD 180 Carbonate Removal Device. B: QD Charge Detection, Dionex QDC cell, 6 V, recycle mode.

Typical System Pressure:

3600 psi

TABLE 1. IC conditions for beverage analysis.

Results QD Charge Detection A charge detector (QD) is a constant voltage membrane device that maintains a specified potential at the anode and cathode (Figure 2).1 As the sample passes through the detector, the ions are drawn through the ion-exchange membranes, drawing a current to balance the charge. This results in a response proportional to the charge state and a significantly higher response for weakly ionized compounds than would be obtained with CD.

Data Analysis Thermo Scientific™ Dionex™ Chromeleon™ Chromatography Data System (CDS) software

FIGURE 2. Mechanisms of Dionex charge detection.

0 5 10 15 20 25Time/ min

120

140

160

180

Ca

pa

cit

an

ce

/ f

F

IO3-

BrO3-

NO3-NO2-

I-

Br-

0 5 10 15 20 25Time/ min

120

140

160

180

Cap

acita

nce

/ fF

IO3-

BrO3-

NO3-NO2-

I-

Br-

Signal total charges

AX CX (+) (-)

H2O

HY A+ Y-

AOH

Charge detection can be used to estimate concentration.1 In charge detection, all the salts and acids with the same equivalency have similar responses (Figure 3) as compared with conductance where the salts have lower response.

0 20 40 60Time, min

28

28.4

28.8

29.2

29.6

30

Curre

nt,

A

HClO4CH3SO3HHNO3

KClNaCl

NaNO3 Specific Conductance (S/cm/mM) HNO3 = 421 CH3SO3H = 380 HClO4 = 418 NaNO3 = 121

FIGURE 3. Conductance versus charge detection.

Figure 4 shows increased linear response for weakly ionized analytes with charge detection.1

Fluoride (Pka 3.17)

R² = 1 0

50

0 20 40 60 80 100 120

R² = 0.9999 0

20

0 20 40 60 80 100 120

Chloride

R² = 1 0

100

0 20 40 60 80 100 120

Formate (Pka 3.75)

R² = 0.9999

-20

0

20

0 50 100 150

R² = 0.9998

-10

0

10

0 20 40 60 80 100 120

Chloride

R² = 0.9997

-10

0

10

0 50 100 150

Fluoride (Pka 3.17)

Formate (Pka 3.75)

FIGURE 4A. FIGURE 4B.

FIGURE 4. Compares CD (A) and QD (B) responses with concentration.

3

7 2 5,6

4 13

1

15

12

11

Minutes 0 45 30 10 40 20 -5

µA*

30

µS

-10

100

A B

8

9 10

16

19

18

14 17

20

Peaks: 15. Sulfate 16. Oxalate 17. Phosphate 18. Citrate 19. Isocitrate 20. Unknown

FIGURE 9. Comparing CD to QD in a diluted orange juice sample to identify co-elution and detect additional peaks.

FIGURE 1. Dionex ICS-4000 Capillary HPIC system (FIGURE 1A), Dionex IC Cube with CD and QD Detectors (FIGURE 1C), Dionex QDC Charge Detector Cell (FIGURE 1C).

1A.

1B.

1C.

Figure 8 shows the QD chromatogram normalized at the chloride peak and overlaid on the CD chromatogram of a diluted guava juice sample.2 The chromatograms show a higher proportional charge with QD than CD for organic acids in diluted guava juice.

FIGURE 8. Comparison of QD to CD responses in diluted guava juice.

µS 3

6

2

5 4 13

Minutes 0 45

-20 30 10 40 20

90

1

7

8

9

10

11

12

µA*

-2

8

A B

Detection: A: Suppressed conductivity, Dionex ACES 300 suppressor, recycle B: QD Charge Detection, *normalized to chloride peak

Sample Prep.: Diluted 5-fold, filtered, 0.2 µm Peaks: 1. Quinate 8. Malate- 2. Lactate Succinate 3. Acetate 9. Sulfate 4. Glycolate 10. Oxalate 5. Propionate 11. Phosphate 6.Formate 12. Citrate 7. Chloride 13. Isocitrate

Columns: Dionex IonPac AS11-HC-4µm column set, 0.4 mm Eluent Source: Dionex EGC-KOH capillary cartridge Gradient: 1 mM KOH (5 min), 1–15 mM KOH (5–15 min), 15–30 mM KOH (15–23 min), 30–60 mM KOH (23–31 min), 60 mM KOH (31–45 min)

Eluent Source: EGC-KOH capillary Gradient: 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)

Detection: A: Suppressed conductivity, Dionex ACES 300 suppressor, recycle mode B: QD Charge Detection, *normalized to chloride peak

Sample Prep.: Diluted 10-fold, filtered, 0.2 µm

Peaks: 1. Quinate 2. Glycolate 3. Lactate 4. Acetate 5. Formate 6. Pyruvate 7. Galacturonate

Concentration

Res

pons

e (µ

S*m

in)

A

B

C1

R2

R1

CD

Res

pons

e (µ

A*m

in)

C1

R3

QD

A or B

Res

pons

e (µ

A*m

in)

C1 C2

R2

R3

QD Confirms A or B

Concentration

Res

pons

e (µ

S*m

in)

A

B

C1 C2

R1

CD

FIGURE 5. Compares CD (A) and QD (B) responses with concentration. FIGURE 5A. Same response. FIGURE 5B. Different response.

Gradient + 1 mM KOH (0–8 min), 10% Methanol*: 1–15 mM (8–18 min), 15–30 mM (18–28 min), 30–60 mM (8–18 min)

0 10 20 30 40 45 -10

10

µS

Minutes

1

2 3 4 5 6,7

8 9

10

11

12

13 14

15

16,17 19

20

21 22

23 24

25

Apple

Standard

Cranberry

Concentration

Figures 5 and 6 show the advantages of using different detectors. In Figure 5, both analytes have the same response (R1) by CD but could have different responses/concentration (C1 or C2), making peak selection problematic. However, the QD response (R2, R3) confirms the concentration of each analyte (A = C1, B = C2).

In Figure 6, both analytes have the same response (R3) by QD but different responses by CD, confirming C1 concentration by both modes.

FIGURE 6. Compares CD (A) and QD (B) responses with concentration. FIGURE 6A. Different response. FIGURE 6B. Same response.

Concentration

Confirms C1

Peaks (Standard): mg/L 1. Quinate 1 2. Fluoride 0.6 3. Lactate 1 4. Acetate 1 5. Propionate 1 6. Formate 1 7. Butyrate 1 8. Pyruvate 2 9. Galacturonate 2

Detection: Suppressed Conductivity, Dionex ACES 300 suppressor, external water mode Sample: Juice, 50-fold sample dilution

FIGURE 7. Profiling organic acids to identify adulteration.

mg/L 18. Sulfate 2 19. Fumarate 2 20. Oxalate 2 21. Phosphate 3 22. Citrate 3 23. Isocitrate 3 24. cis-Aconitate -- 25. trans-Aconitate 3

Figure 7 demonstrates profiling of organic acids using CD to identify adulteration of a higher cost juice with a lower cost juice to increase profits. Cranberry juice with characteristic quinate peak (1) can easily be distinguished from the lower cost apple juice with malate peak (14).

mg/L 10.Chloride 1 11.Bromide 1 12.Nitrate 1 13. Glutarate 2 14. Succinate 2 15. Malate 2 16. Carbonate -- 17. Tartrate 2

Figure 9 shows misidentified nitrate peak by retention time alone. CD and QD responses (circle) indicate that the peak is likely a multi-charged organic acid. QD (boxes) response (boxes) show peaks previously unidentified by CD. increased linear response for weakly ionized analytes with charge detection.1

Peaks: 8. Chloride 9. Nitrate ? 10. Glutarate 11. Unknown 12. Malate 13. Maleate 14. Unknown

18

PO71296-EN 0914S

6 Using Capillary IC with Suppressed Conductivity and Charge Detection to Profile Organic Acids in Juices and Beverages

Using Capillary IC with Suppressed Conductivity and Charge Detection to Profile Organic Acids in Juices and Beverages Hua Yang, Terri Christison, Linda Lopez Thermo Fisher Scientific, Sunnyvale, CA, USA

Conclusion The QD Charge Detector offered on the Dionex ICS-4000 HPIC system improves sample analysis and reporting reliability by:

Detecting peaks previously not detected by CD.

Identifying doubly and triply charged ions from the proportionally higher response than the singly charged ions.

Providing more linear response and proportionally higher responses for weakly ionized than strongly ionized compounds by CD

Detecting co-eluting peaks by the proportionally higher responses of multi-charged ions than singly charged ions.

References 1. Srinivasan, K., PhD. High Pressure Ion Chromatography Charge Detection,

webinar, October 2012. Thermo Fisher Scientific, Sunnyvale, CA, 2013.

2. Basumallick, L., PhD. Analysis of Carbohydrates & Organic Acids Using Capillary IC Methods, webinar, February 2013. Thermo Fisher Scientific, Sunnyvale, CA, 2013.

3. Verma, M. What is Charge Detection? White paper, WP70585_E 03/13S. Thermo Fisher Scientific, Sunnyvale, CA, 2013.

Overview Purpose: To demonstrate the advantages of using QD Charge detection for Ion Chromatography (IC).

Methods: Inorganic anions and organic acids were separated on a high-capacity 4 µm particle Thermo Scientific™ Dionex™ IonPac™ AS11-HC-4µm capillary column and detected with suppressed conductivity in series with charge detection. Analysis was facilitated by a high-pressure capillary IC system.

Results: Very high efficient separations at > 3500 psi system pressures were demonstrated on the Dionex IonPac AS11-HC-4µm on a dedicated capillary IC system. The QD charge detector shows comparably higher charge response for organic acids than for chloride and sulfate and can detect other peaks previously not detected by conductivity (CD). CD/QD ratios were used to assess peak purity, thereby improving reporting accuracy.

Introduction Determinations of organic acid profiles in fruit juices are important in the beverage industry to ascertain product quality and to meet labeling requirements for food products. Ion chromatography with suppressed conductivity is the ideal analytical method for ionic analytes. However organic acids which are weakly ionized can exhibit lower conductivity responses versus concentration than strongly ionized anions, such as chloride and sulfate. However, the new Thermo Scientific Dionex QD Charge Detector promotes complete dissociation of even weakly ionized compounds.

Methods Sample Preparation Commercial juice samples were diluted and filtered (0.2 µm) with a syringe filter.

Ion Chromatography Instrumentation (Figure 1) Thermo Scientific™ Dionex™ ICS-4000 HPIC™ dedicated capillary IC system with • Dionex IonPac ASTC-500 trap column • Thermo Scientific Dionex Conductivity Detection (CD) detector • Thermo Scientific Dionex QD Charge Detector Cell (QDC) • Thermo Scientific Dionex AS-AP Autosampler

All trademarks are the property of Thermo Fisher Scientific 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.

Column set: Dionex IonPac AS11-HC-4µm, guard and separation columns, 0.4 mm i.d.

Eluent Source: Thermo Scientific Dionex EGC-KOH capillary cartridge with Thermo Scientific Dionex CR-ATC capillary trap column

Gradient: Potassium hydroxide, listed in figures.

Flow Rate: 0.015 mL/min

Inj. Volume: 0.4 µL

Column Temp.: 30 C

Detection: A: Suppressed conductivity, Thermo Scientific™ Dionex™ ACES™ Anion Capillary Electrolytic Suppressor, recycle mode, Thermo Scientific Dionex CRD 180 Carbonate Removal Device. B: QD Charge Detection, Dionex QDC cell, 6 V, recycle mode.

Typical System Pressure:

3600 psi

TABLE 1. IC conditions for beverage analysis.

Results QD Charge Detection A charge detector (QD) is a constant voltage membrane device that maintains a specified potential at the anode and cathode (Figure 2).1 As the sample passes through the detector, the ions are drawn through the ion-exchange membranes, drawing a current to balance the charge. This results in a response proportional to the charge state and a significantly higher response for weakly ionized compounds than would be obtained with CD.

Data Analysis Thermo Scientific™ Dionex™ Chromeleon™ Chromatography Data System (CDS) software

FIGURE 2. Mechanisms of Dionex charge detection.

0 5 10 15 20 25Time/ min

120

140

160

180

Ca

pa

cit

an

ce

/ f

F

IO3-

BrO3-

NO3-NO2-

I-

Br-

0 5 10 15 20 25Time/ min

120

140

160

180

Cap

acita

nce

/ fF

IO3-

BrO3-

NO3-NO2-

I-

Br-

Signal total charges

AX CX (+) (-)

H2O

HY A+ Y-

AOH

Charge detection can be used to estimate concentration.1 In charge detection, all the salts and acids with the same equivalency have similar responses (Figure 3) as compared with conductance where the salts have lower response.

0 20 40 60Time, min

28

28.4

28.8

29.2

29.6

30

Curre

nt,

A

HClO4CH3SO3HHNO3

KClNaCl

NaNO3 Specific Conductance (S/cm/mM) HNO3 = 421 CH3SO3H = 380 HClO4 = 418 NaNO3 = 121

FIGURE 3. Conductance versus charge detection.

Figure 4 shows increased linear response for weakly ionized analytes with charge detection.1

Fluoride (Pka 3.17)

R² = 1 0

50

0 20 40 60 80 100 120

R² = 0.9999 0

20

0 20 40 60 80 100 120

Chloride

R² = 1 0

100

0 20 40 60 80 100 120

Formate (Pka 3.75)

R² = 0.9999

-20

0

20

0 50 100 150

R² = 0.9998

-10

0

10

0 20 40 60 80 100 120

Chloride

R² = 0.9997

-10

0

10

0 50 100 150

Fluoride (Pka 3.17)

Formate (Pka 3.75)

FIGURE 4A. FIGURE 4B.

FIGURE 4. Compares CD (A) and QD (B) responses with concentration.

3

7 2 5,6

4 13

1

15

12

11

Minutes 0 45 30 10 40 20 -5

µA*

30

µS

-10

100

A B

8

9 10

16

19

18

14 17

20

Peaks: 15. Sulfate 16. Oxalate 17. Phosphate 18. Citrate 19. Isocitrate 20. Unknown

FIGURE 9. Comparing CD to QD in a diluted orange juice sample to identify co-elution and detect additional peaks.

FIGURE 1. Dionex ICS-4000 Capillary HPIC system (FIGURE 1A), Dionex IC Cube with CD and QD Detectors (FIGURE 1C), Dionex QDC Charge Detector Cell (FIGURE 1C).

1A.

1B.

1C.

Figure 8 shows the QD chromatogram normalized at the chloride peak and overlaid on the CD chromatogram of a diluted guava juice sample.2 The chromatograms show a higher proportional charge with QD than CD for organic acids in diluted guava juice.

FIGURE 8. Comparison of QD to CD responses in diluted guava juice.

µS 3

6

2

5 4 13

Minutes 0 45

-20 30 10 40 20

90

1

7

8

9

10

11

12

µA*

-2

8

A B

Detection: A: Suppressed conductivity, Dionex ACES 300 suppressor, recycle B: QD Charge Detection, *normalized to chloride peak

Sample Prep.: Diluted 5-fold, filtered, 0.2 µm Peaks: 1. Quinate 8. Malate- 2. Lactate Succinate 3. Acetate 9. Sulfate 4. Glycolate 10. Oxalate 5. Propionate 11. Phosphate 6.Formate 12. Citrate 7. Chloride 13. Isocitrate

Columns: Dionex IonPac AS11-HC-4µm column set, 0.4 mm Eluent Source: Dionex EGC-KOH capillary cartridge Gradient: 1 mM KOH (5 min), 1–15 mM KOH (5–15 min), 15–30 mM KOH (15–23 min), 30–60 mM KOH (23–31 min), 60 mM KOH (31–45 min)

Eluent Source: EGC-KOH capillary Gradient: 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)

Detection: A: Suppressed conductivity, Dionex ACES 300 suppressor, recycle mode B: QD Charge Detection, *normalized to chloride peak

Sample Prep.: Diluted 10-fold, filtered, 0.2 µm

Peaks: 1. Quinate 2. Glycolate 3. Lactate 4. Acetate 5. Formate 6. Pyruvate 7. Galacturonate

Concentration

Res

pons

e (µ

S*m

in)

A

B

C1

R2

R1

CD

Res

pons

e (µ

A*m

in)

C1

R3

QD

A or B

Res

pons

e (µ

A*m

in)

C1 C2

R2

R3

QD Confirms A or B

Concentration

Res

pons

e (µ

S*m

in)

A

B

C1 C2

R1

CD

FIGURE 5. Compares CD (A) and QD (B) responses with concentration. FIGURE 5A. Same response. FIGURE 5B. Different response.

Gradient + 1 mM KOH (0–8 min), 10% Methanol*: 1–15 mM (8–18 min), 15–30 mM (18–28 min), 30–60 mM (8–18 min)

0 10 20 30 40 45 -10

10

µS

Minutes

1

2 3 4 5 6,7

8 9

10

11

12

13 14

15

16,17 19

20

21 22

23 24

25

Apple

Standard

Cranberry

Concentration

Figures 5 and 6 show the advantages of using different detectors. In Figure 5, both analytes have the same response (R1) by CD but could have different responses/concentration (C1 or C2), making peak selection problematic. However, the QD response (R2, R3) confirms the concentration of each analyte (A = C1, B = C2).

In Figure 6, both analytes have the same response (R3) by QD but different responses by CD, confirming C1 concentration by both modes.

FIGURE 6. Compares CD (A) and QD (B) responses with concentration. FIGURE 6A. Different response. FIGURE 6B. Same response.

Concentration

Confirms C1

Peaks (Standard): mg/L 1. Quinate 1 2. Fluoride 0.6 3. Lactate 1 4. Acetate 1 5. Propionate 1 6. Formate 1 7. Butyrate 1 8. Pyruvate 2 9. Galacturonate 2

Detection: Suppressed Conductivity, Dionex ACES 300 suppressor, external water mode Sample: Juice, 50-fold sample dilution

FIGURE 7. Profiling organic acids to identify adulteration.

mg/L 18. Sulfate 2 19. Fumarate 2 20. Oxalate 2 21. Phosphate 3 22. Citrate 3 23. Isocitrate 3 24. cis-Aconitate -- 25. trans-Aconitate 3

Figure 7 demonstrates profiling of organic acids using CD to identify adulteration of a higher cost juice with a lower cost juice to increase profits. Cranberry juice with characteristic quinate peak (1) can easily be distinguished from the lower cost apple juice with malate peak (14).

mg/L 10.Chloride 1 11.Bromide 1 12.Nitrate 1 13. Glutarate 2 14. Succinate 2 15. Malate 2 16. Carbonate -- 17. Tartrate 2

Figure 9 shows misidentified nitrate peak by retention time alone. CD and QD responses (circle) indicate that the peak is likely a multi-charged organic acid. QD (boxes) response (boxes) show peaks previously unidentified by CD. increased linear response for weakly ionized analytes with charge detection.1

Peaks: 8. Chloride 9. Nitrate ? 10. Glutarate 11. Unknown 12. Malate 13. Maleate 14. Unknown

18

PO71296-EN 0914S

www.thermofisher.com©2016 Thermo Fisher Scientific Inc. All rights reserved. All trademarks are the property of Thermo Fisher Scientific and its subsidiaries. This information is presented as an example of the capabilities of Thermo Fisher Scientific products. It is not intended to encourage use of these products in any manners that might infringe the intellectual property rights of others. Specifications, terms and pricing are subject to change. Not all products are available in all countries. Please consult your local sales representative for details.

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Africa +43 1 333 50 34 0Australia +61 3 9757 4300Austria +43 810 282 206Belgium +32 53 73 42 41Brazil +55 11 3731 5140Canada +1 800 530 8447China 800 810 5118 (free call domestic)

400 650 5118

Denmark +45 70 23 62 60Europe-Other +43 1 333 50 34 0Finland +358 9 3291 0200France +33 1 60 92 48 00Germany +49 6103 408 1014India +91 22 6742 9494Italy +39 02 950 591

Japan +81 6 6885 1213Korea +82 2 3420 8600Latin America +1 561 688 8700Middle East +43 1 333 50 34 0Netherlands +31 76 579 55 55 New Zealand +64 9 980 6700 Norway +46 8 556 468 00

Russia/CIS +43 1 333 50 34 0Singapore +65 6289 1190Sweden +46 8 556 468 00 Switzerland +41 61 716 77 00Taiwan +886 2 8751 6655UK/Ireland +44 1442 233555USA +1 800 532 4752