1. Determination of Adsorbable Organic Halogen in Wastewater
This is the default title slide for Thermo Fisher Scientific
Determination of Adsorbable Organic Halogen in Wastewater
Jingli Hu, Jeff Rohrer, and Kirk Chassaniol
Thermo Fisher Scientific, Sunnyvale, CA

2. Outline AOX (Adsorbable Organic Halogen) Combustion IC
Ion Chromatography
Methods
Results and Conclusions

3. AOX Introduction Organohalogens are toxic and persistent compounds
Given high priority in the monitoring and control of environmental pollution
AOX represents the equivalent amount of fluorine, chlorine, and bromine contained in organic compounds, expressed as chloride substances that can be adsorbed from water onto activated carbon
Organic halogen compounds cannot be directly analyzed by ion chromatography (IC)
Automated combustion ion chromatography (CIC) is often used to determine these organic halogen contaminants.

4. Diagram of a CIC System

5. CIC System Components
In CIC, the samples, including halogen-containing compounds, are first combusted and the resultant gases are released into an absorption solution, which is directly injected into an IC system
Ion Chromatography System
Gas Absorption Unit
Furnace
Solid/Liquid Autosampler

6. Reagent-free Ion Chromatography (RFIC) System

7. Hydroxide Eluent Generation
EluGen KOH Cartridge
[KOH] 
Current
Flow rate
[ + ]
Pt anode
(H2O H+ + ½O2 + 2e–)
Vent K+
Electrolyte
Reservoir K+
Cation-exchange connector
KOH
Generation
Chamber
Pump H2
H2O
KOH + H2
Degas
Unit
KOH
CR-ATC Anion Trap
[–]
Pt cathode
(2H2O + 2e– OH– + H2)

8. The Role of Chemical Suppression (KOH)
Eluent (KOH)
Sample F-, Cl-, SO42-
Analytical Column (Anion Exchanger )
Anion Suppressor (Cation Exchanger)
HF, HCl, H2SO4 in H2O
KaF, KCl, K2SO4 in KOH
Waste H+
Without Suppression
Counter Ions µS F-
SO42-
Cl-
Time
With Suppression K+

9. Thermo Scientific Dionex Electrochemically Regenerated Suppressors

10. Sample Preparation
Wastewater samples (50 mL) were absorbed onto granular activated carbon (GAC) columns
The column was then washed with 20 mL of sodium nitrate washing solution (0.01 M) at 2–3 mL/min to displace inorganic chloride ions
A rod was used to push the carbon from the column into a sample boat
Samples were analyzed with CIC
strong acids are subject to a strong electrostatic exclusion caused by the negative charge of the stationary phase, which prevents them from penetrating the pores in the packing material
weak acids, such as organic acids, the degree they can penetrate the pores is determined by the size of the charge (think of it as pKa), which results in differences in elution time (separation).
However, in actuality, a hydrophobic interaction also occurs with some of the packing substrate (styrene-divinylbenzene), which can delay the elution of hydrophobic organic acids in particular
electrostatic exclusion due to negatively-charged stationary phase,
hydrophobic interaction with the stationary phase matrix
penetration into stationary phase pores, determine elution times.

11. Combustion Conditions

12. IC Conditions
Thermo Scientific™ Dionex™ Integrion™ HPIC™ System

13. Separation of a Standard Anion Mixture
Standard halide solutions were directly injected into the IC to yield well resolved peaks within 10 min

14. Determination of AOX in (A) Wastewater and (B) Spiked Wastewater
Figure shows an overlay of chromatograms of unspiked and spiked wastewater. As the figure shows, the Dionex IonPac AS18-4μm column and suppressed conductivity detection achieve excellent resolution and sensitive detection for AOX.

15. Calibration Data, Retention Time, and Peak Area Precisions (n = 3)
To determine the calibration ranges, the peak responses to concentration were determined using triplicate injections of calibration standards (Table ). The excellent retention time stability and peak area precision are consistent with results typically obtained when using an electrolytically generated high-purity potassium hydroxide eluent.

16. Recovery of AOX Spiked in DI Water (n=3)
Working AOX standard trichlorophenol stock solution (1,000 mg/L Cl–), 4-fluorobenzoic acid solution (100 mg/L F–), and 4-bromoacetanilide stock solution (200 mg/L Br–) were used to spike AOX into DI water. Four spike levels were chosen and three replicate analyses were done on each level to determine the analysis accuracy and precision. Table 2 shows the recovery for AOF, AOCl, and AOBr spiked in DI water at all four levels. All three organic halides demonstrate acceptable recovery (85–115%). Good precision was achieved as evidenced by the relative standard deviation (RSD) values calculated from the three replicates (1.4–5.1).

17. Recoveries of AOX Spiked in Wastewaters (n = 3)
Three wastewater samples were obtained from local wastewater plants. Three replicates were performed for each sample. Table summarizes the recoveries for AOX spiked in wastewater samples. AOF, AOCl, and AOBr all demonstrated excellent recovery (95–105%).

18. Conclusions
AOX can be precisely and accurately determined in wastewater using combustion ion chromatography
Analysis was automated using the Mitsubishi AQF–2100H system in combination with the Dionex Integrion HPIC system with a Dionex IonPac AS18-4μm column
Suppressed conductivity detection selectivity detects only anionic species in aqueous solution from the absorbed combustion gas
Eluent generation frees the analyst from the need to prepare eluent, eliminates the handling of strong base, and removes a possible source of error

19. Thermo Scientific AppsLab Library of Analytical Applications
Thermo Scientific Application Note 72333: Determination of adsorbable organic halogen in wastewater using a combustion ion chromatography system

20. CIC Application Notes
AN72693: Determination of total fluorine, chlorine, and sulfur in aromatic hydrocarbons by oxidative pyrolytic combustion followed by ion chromatography
AU72588: Determination of Chlorine, Bromine, and Sulfur in Polyethylene Materials using Combustion IC with a Carbonate/Bicarbonate Eluent
AN72573: Determination of Halogens in Polymers and Electronics using a Combustion Ion Chromatography System
AN72349: Determination of Chlorine, Bromine, and Sulfur in Polyethylene Materials using Combustion Ion Chromatography
AN72333: Determination of Adsorbable Organic Halogen in Wastewater using a Combustion Ion Chromatography System
AN72268: Determination of Fluoride in Tea using a Combustion Ion Chromatography System
AN1145: Determination of Halogens in Coal Using Combustion Ion Chromatography
TN72211: Combustion Ion Chromatography with a Dionex Integrion HPIC System