Increment extraction error

This materialization is achieved by first defining the increment to be extracted - an operation termed increment delimitation. After this, the increment must be physically extracted. These two operations are sampling processes each associated with potential errors which are termed the increment delimitation error (IDE) and the increment extraction error (lEE) respectively. 

Increment Extraction Error error of this kind arises when the mechanics used to actually take a sample from the sampling target fail to precisely extract the intended sample properly designed sampling equipment recommended by Gy, e.g., scoops and spatulas that are flat (not spoon-shaped) and have parallel sides to avoid the preferential sampling of larger particles, and good protocols, are essential. 

The variogram function is not defined for lag = 0 - which would correspond to extracting the exact same increment twice. Even though this is not physically possible, it is highly valuable to obtain information of the likely variance corresponding to this zero-point variability (i.e. what if it would have been possible to repeat the exact same physical sampling). The TOS identifies this variance as MPE (minimum practical error), which is also known as V(0). 

Repeating an axiom stated earlier, mechanical samplers are designed to extract increments of sample from a bulk quantity of material B in a manner that increments S are representative within statistical bounds of the bulk B. Further, the sampler is designed and constructed in conformance to criteria stated previously under Mechanical Delimitations of Sampling to assure that negligible errors arise from mechanical influence. 

As shown in several studies, the pressure is usually a minor variable for the resulting efficiency in PHSE [18-20] provided the level used is high enough to maintain the solvent in the liquid state. In a study by Saim et al. [20], the total amount of PAHs extracted at different pressures (85 and 165 bar) with all other variables kept constant (120°C and 9 min static extraction) was similar (differences were within experimental error). In some cases, however, pressure can be a key to ensuring complete analyte removal. The use of high pressures facilitates extraction from samples where the analytes have been trapped in matrix pores. The pressure increment forces the solvent into areas of the matrices that would not normally be contacted by them under atmospheric conditions. For example, if analytes are trapped in pores, and water (or even an air bubble for small pores) has sealed pore entrances, then organic solvents may not be able to contact such analytes and extract them. The pressure increase (along with elevated temperatures and reduced solvent surface tensions) forces the solvent into the pore to contact the analytes. 

---