Chapter 1 - What is mass spec?

Question 1

First mass spec was created

Answer 1

by JJ Thomson in 1906.

Question 2

The basic principle of MS is to

Answer 2

generate ions from inorganic or organic compounds, separate these ions by their m/z ratio, and detect them qualitatively and quantitatively by their m/z ratio and abundance.

Question 3

An MS consists of

Answer 3

an ion source, a mass analyzer, and a detector.

Question 4

MS can be regarded as practically nondestructive because

Answer 4

the amount of analyte needed is so small.

Question 5

Y-axis

Answer 5

ordinate

Question 6

X-axis

Answer 6

abscissa

Question 7

Base peak

Answer 7

The most intense peak of a mass spectrum.

Question 8

In most representations, the intensity of the base peak is normalized to

Answer 8

100% relative intensity.

Question 9

Minimum amount of sample

Answer 9

1 attomol (10^-18 moles) = 6.022 X 10^5 molecules

Question 10

Unified atomic mass (u)

Answer 10

1/12 mass of a single carbon-12 atom (same thing as Da)

Question 11

Profile mode

Answer 11

Gaussian peaks

Question 12

Centroid mode

Answer 12

Straight line vertical peaks

Question 13

Total ion chromatogram (TIC)

Answer 13

Summation of peak intensities of each mass spectrum as successively acquired during analysis.

Question 14

Extracted Ion Chromatogram (EIC)

Answer 14

A chromatogram created by plotting the intensity of the signal observed at a chosen m/z value or set of values in a series of mass spectra recorded as a function of retention time.

Question 15

Sensitivity is defined as

Answer 15

the slope of a plot of analyte amount vs. signal strength.

Question 16

Sensitivity units

Answer 16

C/ug for solids

A/Pa for gases

Question 17

Limit of detection (LOD)

Answer 17

The smallest flow or the lowest amount of analyte necessary to obtain a signal that can be discerned from the background noise.

Question 18

Signal to noise ratio (S/N)

Answer 18

describes the uncertainty of an intensity measurement.

Question 19

Noise results from the

Answer 19

electronics of an instrument.

Question 20

Noise is present

Answer 20

between the signals and also on the signals.

Question 21

The reduction of noise is proportional to the

Answer 21

square root of acquisition time or number of single spectra that are averaged (reduced by a factor of 10 by averaging 100 spectra)

Question 22

Signals are regarded to be clearly visible at S/N > or = to

Answer 22

10

Question 23

S/N greater than 1000 means

Answer 23

that noise is essentially invisible in the spectral plot.

Question 24

The abscissa of a mass spectrum is to be labelled only as

Answer 24

m/z