Hello Edward,

First you have to accurately weigh your sample to 4 decimal places. Then you digest it in nitric acid and make it up so that it is 3% with respect to nitric acid in the final solution. Always use volumetric flasks. If the sample contains silicates, then you have to fully digest it using HF / aqua regia. The HF / aqua regia must be fumed to dryness and then appropriate volume of concentrated nitric acid added, so that the final solution is 3% with respect to nitric acid after being made up to the desired volume. Remember HF is deadly, and appropriate safety gear such as lab coats, goggles, safety shoes and special fume cupboards must be utilised for the purpose. Always peform the experiment in replicates and include blanks which undergo the same procedure as the samples. Also, always use high purity water and "Tracepur" nitric acid. Nitric acid is preferred to hydrochloric acid due to it having less interference and is considered "a clean acid".

Analyse your samples and blanks for desired elements after preparing operational standards (for those elements) and quality assurance international standards and the addition of internal standards in all solutions. Calculate the amount of each element in the sample.

I hope this helps you.

What is your element of interest for AA analysis? La3+ is helpful when you have an idea of interferences/ ionization in the sample. Do you have a lot of phosphate in your sample? As Alexander stated, 1000 mg/L La can prevent interferences from phosphate in Ca analysis.

One of the best books on atomic absorption is from Perkin Elmer. It has the data and the right methods for preparing standards for all the elements (along with procedures for dealing with interferences).

http://www.lasalle.edu/~prushan/Intrumental%20Analysis_files/AA-Perkin%20Elmer%20guide%20to%20all!.pdf

Lanthanum chloride solution, 10 percent lanthanum: Weigh 58.7 g lanthanum oxide into a 1 L beaker and wet with water. Cautiously, add 100 mL concentrated hydrochloric acid in small portions. When the oxide is completely dissolved, slowly dilute to 500 mL with water while stirring to avoid overheating.

Thanks everyone, especially M. Farooq for the book. Am grateful. I'll follow up if there are problem.