Probably not advisable to continue until you know why you don't get good recovery from the CRM

If you continue as you are, you may be making a serious error in the extraction process, or sampling errors might be affecting the calculations, or the measurement technique might be faulty. You won't know what the "true" results are until you have improved the entire process to within the acceptable tolerance limits.

Your question does leave a few gaps for a complete answer though. A few ideas to help:

• Is the CRM appropriate (rice preferably, or at least a high carbohydrate like wheat flour)? Leafy CRMs are not always appropriate for starchy materials and vice versa.
• Have you dried the CRM sufficiently? Even an hour in humid conditions will absorb moisture (especially with rice) and alter your dry matter weights. Keep it at 80C right up until you need to weigh it.
• Are you getting consistent high or low recoveries? Which elements? What are the tolerances for these elements compare to your efforts?
• What instrument(s) are you using? Are you trying to achieve the unlikely (eg ± 1ppb for Pb using AAS?).
• Is your blank solution clean enough? can it achieve your required limit of detection? Acid extracts elements from the glass bottles it is supplied in, so if you're trying to measure ultratrace elements with contaminated acid, you will be facing an uphill battle. Maybe switch to a different supplier?
• Is the extraction procedure appropriate? Are you using enough acid? Is it hot enough, and for long enough? are you losing sample during the digest? Are the tubes re-used or disposed of after digestion? Are they clean?

If you can go through your method and find a few key points to describe where your method is going awry, then we might be able to provide some more helpful suggestions than these generalised responses.

You can proceed AS LONG AS your documented investigation has determined the source of the problem and the new signed protocol has resolved the issue!

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