Method Blank

 A method blank is carried through all the steps of sampleprepar a tion and a nalysis as if it were an actual sample. This is most important from  the  sample preparation prospective. The same solvents/reagentsthat are used with the actual samples are used here. For example, in theanalysis of metals in soil, a clean soil sample may serve as a method blank.It is put through the extraction, concentration, and analysis steps encountered by the real samples. The method blank accounts for contaminationthat may occur during sample preparation and analysis. 

These could arisefrom the reagents, the glassware, or the laboratory environment.Other types of blanks may be employed as the situation demands. Itshould be noted that blanks are e¤ec tive only in identifying contaminatio n. They do not account for various errors that might exist. Blanks aresel dom used to correct for contamination. More often, a blank above a predetermined value is used to reject  analytical data, making reanalysis andeven resampling necessary. The laboratory SOPs should identify the blanksnecessary for contamination control.