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Analytical Chemistry calculators

Measurement and its reliability. The Beer-Lambert law and spectrophotometer dilutions turn absorbance into concentration; calibration curves, including the four-parameter logistic used for ELISA, turn a signal into a result with its uncertainty; colony counts do the same for plate counts.

The rest describes how far the result can be trusted: limits of detection and quantitation by the ICH and CLSI methods, percent recovery, replicate statistics (SD, %RSD, standard error, confidence interval), Z-scores and outlier screens. Calibration pages show the slope, intercept, R², equation and residuals, and say plainly that a high R² does not make a model valid.

Calibration Curve Calculator (Standard Curve)Linear fit, residuals and an unknown with its uncertaintyOpen calculatorBeer-Lambert Law CalculatorAbsorbance, concentration or ε, and absorbance ⇄ % transmittanceOpen calculatorSpectrophotometer Dilution CalculatorDilute a too-dark sample into the instrument's linear rangeOpen calculatorColony Count Calculator (CFU/mL)CFU/mL from plate counts at several dilutions, weighted over twoOpen calculatorELISA Standard Curve Calculator (4PL)Four-parameter logistic fit and sample concentrationsOpen calculatorLimit of Detection and Quantitation CalculatorLoD and LoQ from a calibration curve (ICH) or blanks (CLSI)Open calculatorPercent Recovery CalculatorRecovery of a spike or a standard, with biasOpen calculatorReplicate Measurement Statistics (SD, %RSD, SE, CI)Mean, SD, %RSD, standard error and 95% CI of replicatesOpen calculatorZ-Score CalculatorZ-score, percentile and probability, or the value for a ZOpen calculatorOutlier Screening Tool (Grubbs, Tukey, Modified Z)Flag suspect values with three standard screensOpen calculator

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Service documentation, failure modes and parts for the instruments these calculations are used with.

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