Dale and Rebek (2006) invented a fluorescent sensor that responds to organophosp

Question

Dale and Rebek (2006) invented a fluorescent sensor that responds to organophosphorus-containing nerve agents. An analysis for sarin was carried out like this: 20.5 g of soil from Syria was extracted by sequentially mixing two 100.00-mL aliquots of an aqueous buffer with an amine-based stabilizer followed by filtering. Both aliquots were combined and then evaporated to dryness at subambient pressure. The solid residue was dissolved in 25.00 mL of alcohol and stored at 4°C until analysis. The fluorescence process involved a calibration curve using the new sensor plotting ppb sarin (in alcohol solutions dropped on the sensor face) versus arbitrary fluorescence units with a LLS fit equation: y = 10.9x + 0.003. A soil blank—containing no sarin—handled the same way generated a signal of 245.6 fluorescence units. If the limit of detection by this method is 10 ppb in soil, and the stored 25.00 mL alcohol from Syrian soil sample produced a signal of 344 fluorescence units, was sarin present in the Syrian soil sample?

Explanation / Answer

A soil blank—containing no sarin—handled the same way generated a signal of 245.6 fluorescence unit and the stored 25.00 mL alcohol from Syrian soil sample produced a signal of 344 fluorescence units, Since 344 is much higher than 245.6 ( about 40% higher), sarin was present in the Syrian soil sample.

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