Mass Reduction as a Specific Sampling Procedure

The focus of process sampling very often is on selecting the final, conveniently small, analytical sample mass as early as possible in the sampling process, preferentially directly as part of the primary sampling. 

Any mass reduction method must be in compliance with the fundamental sampling principle, that all parts of the lot (or subsample) have equal probability of ending up in the final sample (or subsample) for analysis. 

An extensive benchmark stndy has been carried ont in order to identify the optimal mass redaction principle(s) [6], This was achieved by assessing and validating the almost nniversally nsed mass redaction approach, grab sampling, as opposed to a comprehensive series of more advanced techniqnes and methods, 17 in total. All techniqnes and methods were tested with regard to a fall snite of qnality parameters, some scientihcally important, others related to cost and minimizing practical operating conditions and expenses. The most important merit of any mass redaction method is the ability to deliver an unbiased split of material with the smallest possible variation in repeated rnns snbject to the best possible accnracy. These two featnres are summed up in the TOS qnantitative measnre of representativeness. 

The principal types of mass-redaction techniqnes and methods investigated covered  

It is crncial that all mass-rednction equipment is operated correctly. There are a number of very practical rules to be followed when nsing any of the acceptable devices. Neglecting one or more of these will canse the entire mass redaction to be biased, and result in unnecessarily large variation. Although Petersen and colleagues [6] on the snrface primarily deal with stand-alone, laboratory bench type equipment, the principles derived must apply equally well for any type of on-/at- or in-line mass reduction that can be contemplated in the PAT context. 

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