{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

HW 8-calibration curves key

# HW 8-calibration curves key - HW 8 Key 1 Use the following...

This preview shows pages 1–2. Sign up to view the full content.

HW 8 Key 1. Use the following mass spectrometry data and blank to construct a calibration curve with trend line: CH 4 (vol%): 0 0.062 0.122 0.245 0.486 0.971 1.921 Signal (mV): 9.1 47.5 95.6 193.8 387.5 812.5 1671.9 Blank correcting the signal means subtracting the blank signal (9.1 mV) from all other signals. The blank-corrected table is: CH 4 (vol%): 0 0.062 0.122 0.245 0.486 0.971 1.921 Signal (mV): 0 38.4 86.5 184.7 378.4 803.4 1662.8 Plotting vol% vs corrected signal gives the following plot: (Make sure axes are labeled with a name and appropriate units). Replicate measurements of an unknown gave 152.1, 154.9, 153.9, and 155.1 mV, and a blank gave 8.2, 9.4, 10.6, and 7.8 mV. (a) Find the concentration of the unknown. Average unknown: 152.1+154.9+153.9+155.14 = 154.0 Average blank: 8.2+9.4+10.6+7.84 = 9.0 Blank-corrected unknown value: 154.0-9.0 = 145.0 % by vol of unknown methane concentration: 145.0 = 869.13 x – 22.085 x = 0.192% methane by vol. y = 869.13x ‐ 22.085 R² = 0.99925 ‐200 0 200 400 600 800 1000 1200 1400 1600 1800 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Signal(mV) Amount of methane (% by vol) Signal versus % Methane

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
(b) Why might the replicate series of blanks be taken right before the unknown rather than for the calibration curve? What might be good or bad about doing that?
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}