Performance verification Karl Fisher

The Karl Fisher instrumentation and its performance verification are discussed in this chapter. The instrumentation, calibration practices, and common difficulties that are encountered are presented. Neither method validation nor method specific problems are discussed. 

The performance verification of Karl Fisher apparatus should include checks for the accuracy and precision of the instrument. The linearity of the instrument should be determined at installation. The first step is to standardize the instrument (see Section 14.3.2) pure water is sufficient for this purpose. Sodium tartrate dihydrate standard (water content 15.66 0.05%) can be used to assess the accuracy, precision, and linearity of the instrument. Typically, one would measure the water content of at least five samples, over the intended instrument user range. For example, the water content of sodium tartrate dihydrate samples that were 65 mg (ca. 10 mg H20), 195 mg (ca. 30 mg H20), 325 mg (ca. 50 mg H20), 455 mg (ca. 70 mg H20), and 650 mg (100 mg H20) could be determined. Calculate the percent water to assess the instrument s accuracy. The results should be within 98 to 102% of 15.66% water. Determine the % RSD of the percent water found to assess the precision of the instrument. The % RSD should be less than or equal to 1%. Finally, plot the expected water content versus the percent water content to assess the linearity of the instrument s response. A correlation coefficient (r) value of 0.999 or greater is acceptable. 

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