Making standard solutions

Procedures to make ICP Standard Solutions

Since standard solutions determine the data accuracy in chemical analyses, it is very important to make good and accurate standard solutions.  In most cases, ICPO-ES analysis only needs 3 standard solutions: blank, high, and QC but we recommend you make more than that. 

1. Blank should be your matrix solution for your unknown samples and this solution should be used to make other two std solutions. In many cases, you may use 3% nitric acid (v/v) to make your standard solutions. Then, the 3% nitric solution is the blank solution for this purpose.

2. Hi Std and QC should contain all the elements you want to analyze if they are compatible. The concentrations of all elements in the hi-std should be higher than the highest expected concentration in your unknown samples but not too much higher. For this part, please check with us if you are not sure. The concentration of each element in QC should be about half of that in the hi-std but not less than 1 ppm. DO NOT just dilute your hi-std solution for making QC.  You should make hi and QC independently from your stock solutions.  KEEP your standard solutions in bottles, which you know it is ABSOLUTELY clean. PLEASE BE VERY CAREFUL WHEN YOU MAKE THEM! If ou like, you ma make 3 to 5 standards from low to high in concentrations.  The best way is doing a serial dilution. I usually recommend you do a 2x, 4x, and 8x of your high standard solution.  If more dilute solution is needed you just keep expand the list or skip some dilutions.  I also suggest that you use analytical balance with pipette to make the standard solutions for accuracy purpose.

3. Procedure:

   • Stock solution: You should purchase either multi-elements stock solution or single element stock solutions from Fisher, VWR, or other vendors. 

   • Using multi-elements stock solutions: all you need is carefully diluting your stock to the concentration you need with dilute (2 to 5%) HNO3 or HCl. HNO3 is preferred for ICP analysis.

   • Using single element stock solution:

     • Add pre-calculated amount of acid (HCl or Nitric Acid) to a CLEAN volumetric flask. The amount of acid should be based on the volume you are making but final acid concentration should be about 3 to 5% of concentrate acid.

     • Add each stock solution to the v-flask by weighing the solution on an analytic balance.  The weight of the solution that you transfer will be used to calculate the final concentration of each element in your final solution.  The calculation should be based on the density of the stock solution if the stock solution does not have a density of 1 g/ml.

     • Make the volume with DI-water to the mark of the v-flask.

     • Mix the solution very well and transfer to a plastic bottle, which you know it is absolutely clean even it is brand new.  If you are not sure, clean it with dilute HCl acid and rinse with DI water at least 3x.  Then, rinse with a small amount of your standard solution.

If you have any questions on making standard solutions please contact us.