Question 9: Suppose that you have collected fifty 1.0 litre samples to analyse the water in a wetland for pesticides. Th

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Question 9 Suppose That You Have Collected Fifty 1 0 Litre Samples To Analyse The Water In A Wetland For Pesticides Th 1 (89.78 KiB) Viewed 11 times

Question 9: Suppose that you have collected fifty 1.0 litre samples to analyse the water in a wetland for pesticides. The pesticides are only weakly polar and are extracted from water by SPE. During the analysis 25.0 mL of water is passed through an SPE cartridge followed by elution of the pesticides with 5.0 mL of methanol. The methanol solution is analysed by direct injection of a 1 μL volume into a GC-MS with a capillary column. Peaks for pesticides are observed but these have low signal-to-noise ratios. Which of the following changes to the analysis is not a practical way to increase the signal-to-noise ratios of the pesticide peaks? Increase the volume of water passed through the SPE cartridge. Decrease the volume of methanol used to extract the pesticides off the SPE cartridge. O Inject twice the volume of methanol solution into the GC-MS. Concentrate the pesticides in the methanol solution by evaporation before injecting it into the GC-MS. O All these changes are practical ways to increase the signal-to-noise ratios of the pesticide peaks.