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150% of the expected concentration of the sample. All four aliquots are <br /> maintained at the same final volume by adding reagent water or a blank <br /> solution, and may need dilution adjustment to maintain the signals in the <br /> linear range of the instrument technique. All four aliquots are analyzed. <br /> 8.4.3 Prepare a plot, or subject data to linear regression, of <br /> instrument signals or external -calibration-derived concentrations as the <br /> dependant variable (y-axis) versus concentrations of the additions of <br /> standard as the independent variable (x-axis) . Solve for the intercept of <br /> the abscissa (the independent variable, x-axis) which is the concentration <br /> in the unknown. <br /> 8.4.4 Alternately, subtract the instrumental signal or external - <br /> calibration-derived concentration of the unknown (unspiked) sample from <br /> the instrumental signals or external -calibration-derived concentrations of <br /> the standard additions. Plot or subject to linear regression of the <br /> corrected instrument signals or external -calibration-derived concentra- <br /> tions as the dependant variable versus the independent variable. Derive <br /> concentrations for unknowns using the internal calibration curve as if it <br /> were an external calibration curve. <br /> 8.5 Samples must undergo TCLP extraction within the following time <br /> periods: <br /> SAMPLE MAXIMUM HOLDING TIMES EDAYS] <br /> From: From: From: <br /> Field TCLP Preparative <br /> collection extraction extraction <br /> To: To: To: Total <br /> TCLP Preparative Determinative elapsed <br /> extraction extraction analysis time <br /> Volatiles 14 NA 14 28 <br /> Semi -volatiles 14 7 40 61 <br /> Mercury 28 NA 28 56 <br /> Metals , except 180 NA 180 360 <br /> mercury <br /> NA = Not applicable <br /> If sample holding times are exceeded, the values obtained will be considered <br /> minimal concentrations. Exceeding the holding time is not acceptable in <br /> establishing that a waste does not exceed the regulatory level . Exceeding the <br /> holding time will not invalidate characterization if the waste exceeds the <br /> regulatory level . <br /> CD-ROM 1311- 21 Revision 0 <br /> July 1992 <br />