Accreditation of 17025

You  asked

1. I would like to know if all the used samples should be a CRM samples in order to obtain the 17025 accreditation and if we could realise just one repetability reproductibility test on one sample and compare the results with a CRM sample.

Method Validation and measurement uncertainty involves investigating the effect of both systematic and random errors on the accuracy of results. This involves two components -trueness and precision. Both these are qualitative descriptions, where bias is measured to represent trueness; and a measure of spread of results, such as standard deviation to quantify precision. Precision studies include repeatability, intermediate precision and reproducibility. Typically you will use a matrix matched reference material (RM), reference method or reference value to determine any bias; while test samples or spiked sample blanks (matrix matched) are acceptable for the precision studies. Of course RMs could also be used. It is important, either way,  to represent the entire working range; menaing that low, medium and high range samples should be included.

You  also asked

2. we use a Spark Atomic Emission Spectrometry to realise the chemical analysis (zinc and aluminium), there is any criteria in the iso 17025 that obligate us to use an ASTM OR AN iso reference and if yes what should we do if our range of work is out the range mentioned if the standard."

The laboratory need not use a standard method, unless a client or the sector specify you must. As an ISO 17025 accredited laboratory you need to select suitable methods and prove through method validation and quality control; they are adequate for the purpose. The involves showing that the inhouse or non-standard method achieves the performance required- for example limit of detection, accuracy, along with suitable low-enough measurement uncertainty.  This is where Proficiency testing or interlaboratory studies can be used to evaluate how the nonstandard method performs compared to laboratories who may be using a standard method. 

For more information, see the ISO 17025 toolkit procedure Test and Calibration Method Procedure, at https://advisera.com/17025academy/documentation/test-and-calibration-method-procedure/; along with the two supporting documents Test Method Development, Verification and Validation Register and Test Method Development, Verification and Validation Record.