Controls
The following are various types of controls:

Method Blank/ Digestion Blank:

An aliquot of reagent water that is treated exactly as a sample including
exposure to all glassware, equipment, solvents, reagents, and internal
standards that are used with other samples. The method blank is used to
determine if method analytes or other interferences are present in the
laboratory environment, reagents, or apparatus.
      
Travel Blank:

An aliquot of reagent water that transported and handled in the exact same
way as the sample
      
Blank Spike, Laboratory Control Spike, or Laboratory Fortified Blank:

An aliquot of reagent water that is spiked with all the analytes that are to be
tested that is also treated exactly as a sample including exposure to all
glassware, equipment, solvents, reagents, and internal standards that are
used with other samples; also known as a blank spike.
      
Matrix Spike and Matrix Spike Duplicate:

Two aliquots of the same environmental sample to which known quantities
of the method analytes are added in the laboratory. The MS and MSD are
analyzed exactly like a sample, and their purpose is: to determine whether
the sample matrix contributes bias to the analytical results, and to indicate
precision associated with laboratory procedures. The background
concentrations of the analytes in the sample matrix must be determined in a
separate aliquot and the measured values in the MS and MSD corrected for
background concentrations.
      
Duplicate:
      
A duplicate of the sample to examine consistency and variability of the
method.
      
Second Source Check Solution or Quality Control Solution:

A solution of method analytes purchased from a reputable commercial
source, used to evaluate the performance and check the calibration of the
instrument.

All of the above are part of quality control and are used by our laboratory.
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