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Taking Duplicate Samples (2 replies)

Maya Rothman
9 months ago
Maya Rothman 9 months ago

Is that correct during taking the duplicate samples (field duplicate, coarse duplicate and pulp duplicate) for one reference samples, let's say the reference sample is A, then A become A' for field duplicate, A" for coarse duplicate, A'" for Pulp duplicate. Or the duplicate taking at different sample references for each stage (reduction samples). Am dealing with a Nickel Laterite.

9 months ago
Hauptsturm 9 months ago

It appears your concern is not clearly stated. Do you mean to inquire if the sample referencing by A', A" is correct or Restating it might increase your chances of obtaining the appropriate response.

Marshal Meru
9 months ago
Marshal Meru 9 months ago

In my experience the terminology used for duplicates in varied across the world and often confusing. My suggestion is that in agreement with your team clearly define (in writing) the meaning and method of collection of each quality control precision sample that you collect. In terms of Sampling Theory it is however; best to refer to all as 'duplicates' rather than 'replicates' and 'repeats'.

The term 'field-duplicate' is widely used and refers to a duplicate sample collected from the primarily lot in the field. In terms of drilling samples this is usually a second riffle split (having the same mass as the primary split) from the percussion drilling cuttings or perhaps the other half or a quarter core (which is not really correct duplicate as the mass is only half of the half-core).

The term 'coarse-duplicate' often refers to the (riffle or rotary) split duplicate collected following crushing drill core. This may not be available if the entire sample is pulverised.

The term 'pulp-duplicate' usually refers to a second sample collected from the pulverised field sample after the material has been reduced to a powder (usually below 100 or even 75 microns top-size). Many laboratories identify these as 'repeats' and this is where confusion may starts when results are reported as it is not always clear whether the 'repeat' is a second sample analysed separately for the pulp-lot or a repeat reading of a solution or XRF disk extracted from the lot. You should talk to your lab to be clear on what a 'repeat' actually means (pulp-duplicate, solution-duplicate, second reading of the same sample in which case note really a duplicate!).

Also note it is possible to have many duplicates from the same lot. Ideally the duplicate should be analysed in sequence after the primary (often named 'original') sample as we wish to precision of the primary process. However, it is also common practice to collect ‘lab-check-pulp-duplicates' at some future time to compare results with another laboratory.

I do like your idea of using derivative notation to of A then A' and then A'' to signify the position in sequence of each analysis of the same lot but suggest it is not widely used as far as I know. There are ISO standards that deal with precision which may be worth reading on duplicate nomenclature.