# Geochemisrty quick tips: Cation Anion Balance or Charge Balance Error (C.B.E)!

Geochemistry quick tips: Cation Anion Balance or Charge Balance Error (C.B.E)!

Are you lost during a geochemical investigation? Well, sometimes I do get lost. Sometimes I feel like I need more water quality parameters to answer some of the geochemical questions. I never thought about doing just a simple “cation – anion” balance before until I really had to for one unique situation where I had to think about some metal that might be present in the water to produce low pH in the system.

A fundamental property of an aqueous solution is that they are electrically neutral! So, total number of equivalents for the positive constituents must equal to total number of equivalents of negative constituents.

A “cation – anion” balance will never give you 100% accuracy simply because it is virtually impossible to analyze every single ions in the water. In most cases it is also not required. The major cations and anions in ground or surface water almost always make up >95% of the ion balance.

A very good exercise on simple water quality analysis can be found HERE.

Well, we will anyway do our own math using a real water quality analysis!

C.B.E (Charge Balance Error or Cation – Anion Balance)=((Tot Cation meq/L – Total Anion meq/L) / (Total Cation meq/L + Total Anion meq/L))*100%

Below is an example of actual water quality analysis from a coal mine drainage. Note that they reported 4.34% CCE in the laboratory analysis. Now let’s do our analysis.

(Click on the Image for FULL VIEW)

To do our own calculation, we need to convert each anion to meq/L unit. I am attaching a spreadsheet that converts all anions and cations to meq/L.

Below is the screen shot of the actual spreadsheet I used to do the calculation. You should download the spreadsheet and check the calculation yourself. You can also use the spreadsheet to do your own Cation – Anion Balance calculations just by changing values for “measured concentrations”. Remember that you may need to add or subtract few cations or anions based on your particular water analysis.

(Click on the Image for FULL VIEW)

So, we get
Cation – Anion Balance = -2.9%

Now “negative” number for “cation – anion balance” means:

• Excess anions
• or, Lack of cations

While “positive” number for “cation – anion balance” means:

• Excess cations
• or, Lack of anions

A reasonable balance for routine water quality analysis is generally considered to be less than 5%. If you have a higher number, you should reconsider further constituents for analysis.

There are several reasons that may also create an electrical imbalance such as:

1. Laboratory error.
2. Sampling procedure.
3. Use of unfiltered water sample – this is another thing we often neglect to check. Unfiltered water samples contain particulate matter that dissolves into the sample when we add add small acid as preservative.
4. Sometimes some of the constituent may precipitate in the sample container.

Note: Also make sure that you use only “dissolved” constituents to do water “cation – anion” balance calculations.
The Cation Anion Balance or Charge Balance Error should always be included in any water quality analysis. Sometimes they can point out to some obvious errors.

So, never underestimate the importance of Charge – Balance Error (C.B.E) or Cation – Anion Balance.

Editor

Ankan Basu is a Certified Professional Geologist (CPG) with 10+ years of experience in the field of geology, hydrogeology and geochemistry.

### 23 Responses

1. Is says:

Thanks. this really help me.

2. Thanks says:

What a great example! Thanks 2 years later!

3. Ankan Basu says:

Glad that you could use it.

4. Siep says:

Thanks for this info. It is nice to have all the constants summarised. I only wish that water chemistry labs could standardise on the ion sequences, then one woul be able to just have one or two macros.

Another check on water accuarcy is to compare the measured EC with a calculated EC from the individual ion analyses. Is that a prcatical method and is there a spreadsheet somewhere?

5. Ankan Basu says:

Well there is another simple way to check if you have Geochemist’s workbench or PHREEQC for windows (which I like much better than PHREEQI). Just import the data to the PHREEQC and run it. Well let me write another tutorial using the same data I used to present the example above.

6. Suman Shakya says:

Well I have data set for bulk precipitation. And I want to check ion balance. What should i need to do? I want to check it with pH as EC was not working properly.

• Editor says:

Let me know what kind of data do you have and I will try to give you some tips.

7. Suman Shakya says:

Thank you editor.
Right now I am collecting bulk precipitation samples ( twice/month). I want to know how to come up with HCO3 ( is it TA_TC ?) and other finding the value of H+.
so
Cl+NO3+SO4+HCO3 = Na+K+Mg+Ca+NH4+H
Even thought it seems very easy chemistry, but for me its very much difficult.
Thank you

8. Editor says:

Well…
I still don’t know what exactly you are trying to do, but your equation is not right.

When we do charge balance error, we don’t include H+ in our formula (like we don’t include OH- either).

So, if you like to use pH to check for your ion balance, you need to do a CBE calculation based on the major ions and then predict the pH from the sample set.

if you have Geochemist Workbench, then you can do it really easily. They have a CSS module where you can calculate the solution pH based on the analytical result. If the predicted pH is close to your measured pH, then your analysis should be good.

Or may be, give me numbers for the major ions for one set of analysis, I will do the pH calculation for you.

• Suman Shakya says:

Thank you

Suman

9. Suman Shakya says:

Thank you

• Suman Shakya says:

Thank you

• Suman Shakya says:

Dear Editor,

Thank you

• Editor says:

I have your email. Will take a look soon.

• Suman Shakya says:

Dear Editor

Thank you

• Editor says:

10. Suman shakya says:

Can I have my results please?

Thank you

• Editor says:

11. Josh Rubinstein says:

How do you acount for pH in the worksheet?

12. Nyamongo Jared says:

This is really good. Am glad t
hat I am several step a head in Geochemistry.

13. new cheme says:

hi thank you so much for this article. you answered one of my questions, do you add up all of the cations on you parameters or just the major cations, “The major cations and anions in ground or surface water almost always make up >95% of the ion balance.” but can you elaborate on which valence to use if you do add up the minor cations. For example, antimony has a 3 or 5 valence and copper has a 1 or 2 valence?

and what are the parameters that make up major cations and anions in water analysis?

thank you very much.

• Editor says:

Most of the time you only have data for the major cations unless your project needs more elements. Scientifically, you should add ALL cations and ALL anions for the calculation. for Practical purposes, just the major cation and anions do just fine.