587 08 wk01 1_5 std 2pg

587 08 wk01 1_5 std 2pg - Instrumentation Basics We must...

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1 Instrumentation Basics – We must understand the instrument • How does it function? • What are the pros and cons of using a specific instrument for a measurement? • Can we obtain an accurate measurement? We can choose the “best” technology if we are educated on how it functions Instrumentation Important Factors Speed Ease of use Operator skill level Does the user need special training? Access e.g. is the instrument in a facility? Cost / sample run
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2 Instrumentation: Figures of Merit Precision – good precision = small std. dev. Bias – difference between the true value and the measured value Sensitivity – can the instrument differentiate small concentration changes? Detection Limit – 3 X the std dev of the blank plus the blank Dynamic Range – the range of accurate concentration detection Selectivity – quantitative measure of interference effects Response in the form of Data Domains Analog Voltage, Current, Charge or power Time e.g. frequency, periodicity Digital 2-level structure ENERGY source sample RESPONSE
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3 Calibration Methods In order to report a measured concentration value of a sample analyte, calibration is needed – Concentration calibration methods Completed using the analyte of interest » Usually using chemical standards » • Standard addition method – Especially good for complex samples • Internal standard – Known chemical substance added to the solution of interest » • Instrument calibration – Completed using a standard sample Ch. 5 Signal and Noise
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4 Signal and Noise ± Signal ± Noise ¾ Effect of noise increases with decreasing quantity being measured
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587 08 wk01 1_5 std 2pg - Instrumentation Basics We must...

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