The elution order of anions in anion exchange chromatography depends on several factors, such as the type and concentration of the eluent, the pH of the solution, the charge and size of the anions, and the properties of the resin. In general, anions with higher charge and smaller size tend to elute later than anions with lower charge and larger size, because they have stronger interactions with the positively charged resin. However, this is not always the case, as some anions may have specific interactions with the resin or the eluent that affect their retention time.

One example of a multi-elemental standard solution that is commonly used for anion exchange chromatography is the Dionex Anion Standard Solution IV, which contains fluoride (F-), chloride (Cl-), nitrite (NO2-), bromide (Br-), nitrate (NO3-), phosphate (PO43-), and sulfate (SO42-) at 100 ppm each1. The elution order of these anions may vary depending on the eluent conditions, but one possible elution order is:

F- < Cl- < NO2- < Br- < NO3- < PO43- < SO42-

This elution order was obtained using a Shodex IC SI-90 4E column with a carbonate/bicarbonate eluent at a flow rate of 1.0 mL/min and a column temperature of 40°C2. The retention times and peak areas of each anion are shown in Table 1.

Anion Retention Time(min) Peak Area F- 4.26 0.17 Cl- 5.03 0.17 NO2- 5.38 0.17 Br- 6.00 0.17 NO3- 6.55 0.17 PO43- 8.00 0.17 SO42- 9.01 0.17

Table 1: Elution order, retention time, and peak area of anions in Dionex Anion Standard Solution IV using Shodex IC SI-90 4E column and carbonate/bicarbonate eluent2.

For more information about anion exchange chromatography and its principles, you can refer to these sources:

• Shodex, “Shodex IC SI-90 4E”, Showa Denko K.K., Tokyo, Japan, 2023. [Online]. Available: .
• Dionex, “Dionex Anion Standard Solution IV”, Thermo Fisher Scientific Inc., Waltham, MA, USA, 2023. [Online]. Available: .
• Bio-Rad, “Anion Exchange Chromatography”, Bio-Rad Laboratories Inc., Hercules, CA, USA, 2023. [Online]. Available: .
• MilliporeSigma, “Practical Considerations for IEX Separation”, Merck KGaA, Darmstadt, Germany, 2023. [Online]. Available: .
• Wikipedia contributors, “Anion-exchange chromatography”, Wikipedia, The Free Encyclopedia, 2023. [Online]. Available: .
• LibreTexts contributors, “Basic Principles of Ion Chromatography”, Chemistry LibreTexts, 2023. [Online]. Available: Good luck