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Instrumental Analysis > Experimental Spectroscopy Vocab > Flashcards

Experimental Spectroscopy Vocab Flashcards

1
Q

device that converts radiant power into an electrical signal or other physical property, e.g. heat or resistance, that can be measured

A

Detector

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2
Q

The slope of the curve (Q) that describes detector electrical response (S) with incident radiant power (F),

A

Detector sensitivity

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3
Q

The plot of Q(l) vs. l for a particular detector.

A

Spectral Response

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4
Q

The ability of a detector to convert incident radiation into an electrical signal; the ratio of the electrical output (V) to the incident radiant power (W)

A

Responsivity

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5
Q

A measure of detector sensitivity

A

Noise equivalent power (NEP)

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6
Q

A measure of detector sensitivity that normalizes the NEP by taking into account the area of the detector element

A

Specific detectivity (D*)

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7
Q

radiant energy generates current at the interface of a semiconductor and a metal

A

Photovoltaic cell

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8
Q

incident radiation causes emission of electrons from photosensitive cathode surface.

A

Phototube

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9
Q

The cathode and anode in a PMT are biased by 400 – 2500 mV and separated by a series of intermediate dynodes, each progressively more positively biased, which provides an electron multiplication cascade.

A

Photomultiplier tube (PMT)

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10
Q

Reverse-biased p-n junction forms depletion layer on a Si chip with no current; radiation striking the detector causes holes and electrons in depletion layer, producing a current that is proportional to the radiant power.

A

Si photodiode

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11
Q

Semiconductors, e.g. PbS, PbSe, InSb, HgCdTe, that act as a light-dependent resistor; resistance decreases when photons are absorbed.

A

Photoconductivity detector

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12
Q

Gas is heated in an enclosed cell (i.e. Golay cell), causing a reaction (change in capacitance) in a thin membrane.

A

Pneumatic Cell

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13
Q

Detects potential difference at junction between two dissimilar metals (e.g. Bi – Sb), which varies with DT between the two metals.

A

Thermocouple

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14
Q

Resistance thermometer made of semiconductors, e.g. Ge, Si. Detects change of resistance as a function of temperature

A

Bolometer

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15
Q

Detects temperature dependent polarization of pyroelectric crystal, e.g. triglycine sulfate (TGS)

A

Pyroelectric detector

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16
Q

Consists of a linear array of Si photodiodes placed in an integrated circuit; number of individual p-n junctions can range from 64 – 1024.

A

Photodiode array

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17
Q

Two-dimensional array of Si photodiodes containing about 105 individually resolvable pixels. Radiation strikes tube where charge is stored; target is scanned by electron gun that measures the charge needed to restore the individual Si photodiode pixel to its initial state.

A

Vidicon

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18
Q

Solid state sensor with integrated circuit technology. Photons strike MOS-on-p-type Si capacitor; electron charge stored in wells; serial readout destroys accumulated charge; high quantum efficiency (90%) possible.

A

Charge Coupled Device (CCD)

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19
Q

Solid state sensor with integrated circuit technology. Photons strike Si, which generates a + charge; charge is stored beneath negatively biased capacitor plates; random access readout does not destroy accumulated charge

A

Charge Injection Device (CID)

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20
Q

Spectral line broadening mechanism due to energy decay from excited state to ground state described by a damped oscillating dipole function

A

Natural line broadening

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21
Q

The lifetime of the exponential decay of the dampened oscillating dipole function

A

Classical damping constant

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22
Q

the lifetime of the atom or molecule in the excited state

A

Excited state lifetime

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23
Q

The line shape that results from the Fourier transform of the amplitude decay of the damped oscillating dipole function in Natural Line Broadening

A

Lorentzian frequency distribution

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24
Q

The width of a spectral band, measured as the full width of the band at one-half the maximum band intensity between the baseline and the peak; also related to the excited state lifetime

A

Full width at half maximum (FWHM)

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25
Q

The apparent shift in frequency or wavelength of an electromagnetic wave from a source that is moving either away from, or towards, a detector

A

Doppler effect

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26
Q

The line shape that results from Doppler line broadening of moving molecules in a sample

A

Gaussian distribution

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27
Q

Spectral band shape that is a mixture of both Lorentzian and Gaussian line shapes.

A

Voigt Profile

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28
Q

Random fluctuations that are observed in spectra or other measured signals when replicate measurements are made on instrumental outputs that are continuously monitored.

A

Noise

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29
Q

Random signal fluctuations that result from a variety of uncontrollable variables, e.g. temperature, pressure, humidity, vibrations, etc.

A

Chemical noise

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30
Q

Random signal fluctuations that are generated by particular components of an analytical instrument, i.e. source, detector, electronics, etc.

A

Instrumental noise

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31
Q

Measurement of the strength of the signal level relative to the background noise level

A

Signal-to-noise ratio

32
Q

Measurement of the noise strength as the difference between the maximum and minimum noise signal heights

A

Peak-to-peak noise

33
Q

Measurement of the noise strength as the standard deviation of the signal derived from n independent measurements

A

Root-mean-square noise

34
Q

Plot of the mean-square noise per unit frequency interval vs. frequency; describes the type of frequency-dependent noise found in many types of experimental spectroscopy.

A

Noise power spectrum

35
Q

Random, non-fundamental, frequency-dependent noise that usually manifests itself as a slow drift in the signal; exhibits large amplitude at low frequency; also known as “flicker” noise.

A

1 / f Noise

36
Q

A random and fundamental noise whose magnitude is independent of the signal frequency; also known as “background” noise.

A

White noise

37
Q

A frequency-dependent, non-random, and non-fundamental noise source; frequently appears at discrete frequencies due to pick-up or coupling with other signal sources, e.g. 60 Hz electrical noise; can be correlated to external event, e.g. the “5 o-clock effect”.

A

Interference/environmental noise

38
Q

Random signal fluctuations in an electrical signal; characteristic of all electronic circuits.

A

Electronic noise

39
Q

Type of random, fundamental, white noise produced by thermal agitation of electrons in electrical circuits

A

Thermal / Johnson noise

40
Q

Type of random, fundamental, white noise produced whenever electrons move across a junction or barrier, or current is generated at an interface

A

Shot noise

41
Q

Shielding of electrical cables to reduce environmental noise.

A

Grounding

42
Q

Amplifier circuit with 2 input terminals: reference vs. sample; voltage difference between reference and sample signals is amplified.

A

Difference amplifier

43
Q

Low-pass frequency filter with a long time constant that removes high frequency components, e.g. thermal and shot noise, in DC signals; used to reduce the effect of drift and other low frequency components.

A

Analog filter

44
Q

The alteration of some property of a carrier wave by a signal so that the carrier wave encodes the signal information; moves the signal to a region of the frequency spectrum where it is easily distinguished from noise.

A

Modulation

45
Q

Also called synchronous detector, heterodyne detector or phase-sensitive detector; electronic amplifier that detects specific AC frequency signal, requires a reference signal at the specific detection frequency; only those modulated signals that are “locked-in” to the reference signal are detected and amplified, all other signals are rejected.

A

Lock in amplifier

46
Q

Mathematical co-addition of digital spectra where the final S/N is proportional to the square root of the number of individual spectra collected

A

Ensemble averaging

47
Q

Linear filter in which spectral data points are divided into series of discrete, equally spaced windows; the data points in each are then replaced by the centroid average value of all the data in the window.

A

Boxcar filter

48
Q

Linear filter in which the smoothed data are simple linear functions of the raw input data; input data are multiplied by weighting factors that are the linear average of the data in the filter window; filter window is successively moved along the spectrum, with each data point replaced successively by the corresponding filtered data point.

A

Moving average filter

49
Q

Non-linear filter in which the raw spectral data are smoothed using a polynomial function to fit a series of adjacent data points in the spectra

A

Polynomial / Savitzy-Golay filter

50
Q

Digital filtering of spectral domain signal in frequency domain; Fourier transform of spectrum used; frequency domain spectrum is multiplied by digital filter which removes unwanted frequency regions

A

Fourier filter

51
Q

the fraction of the incident radiant power transmitted through a medium

A

Transmittance

52
Q

logarithm of the fraction of the incident radiant power transmitted through a medium

A

Absorbance

53
Q

The linear relationship between optical absorbance and the concentration of an absorbing species in solution, also sometimes written to emphasize the wavelength dependence of the absorbance

A

Beer Lambert law

54
Q

Determination of the relationship between the analyte concentration and the analytical response.

A

Calibration

55
Q

Use of chemical reference materials that provide a known comparison between concentration and response for calibration purposes.

A

Standardization

56
Q

Calibration procedure where a series of external standard samples are prepared separately from the analytical sample; used when there are no interference effects from matrix components in the analytical sample; calibration is accomplished by measuring an analytical property, e.g. absorbance, as a function of analyte concentration in a series of external standards; calibration curve is then used to predict concentration of unknown

A

External calibration

57
Q

Relationship of a response or dependent variable (y), to a single independent feature or measurement variable (x) by a linear model

A

Linear regression

58
Q

Finds the slope (m) and intercept (b) of the regression line in a linear regression by minimizing the sum of the squares of the residuals between the predicted and actual y values,

A

Method of least squares

59
Q

Variance about a least squares fit regression line

A

Residual variance

60
Q

measure of the “goodness of fit” of the regression model; it describes how well the regression line approximates the real data points

A

Coefficient of determination

61
Q

the square root of the coefficient of determination

A

Correlation coefficient

62
Q

Procedure used to determine concentration of an analyte in an unknown sample by comparison to a set of samples of known concentration; used instead of a calibration curve to solve the matrix effect problem.

A

Method of standard addition

63
Q

Type of Method of Standard Addition: addition of increasing increments of a standard solution to sample aliquots; solution is then diluted to fixed volume before measurement.

A

Continuous Variation of the Standard Solutions

64
Q

Type of Method of Standard Addition: uses replicate measurements on a single spiked sample at high concentration.

A

Single addition method

65
Q

Addition of an inert compound in a known, constant amount to all samples, blanks, and calibration standards in an analysis; calibration involves plotting the ratio of the analyte signal to that of the internal standard in a series of standard solutions.

A

Internal standard method

66
Q

The measure of how close the result of an analytical measurement comes to the true value.

A

Accuracy

67
Q

The reproducibility of the results, i.e. the numerical agreement between replicate measurements.

A

Precision

68
Q

Figures of merit used to determine precision include

A

standard deviation, the standard error of the mean, and the coefficient of variation.

69
Q

Describes the measurement of the systematic or determinate error of the analytical method

A

Bias

70
Q

The ability of an analytical method to discriminate between small differences in analyte concentration

A

Sensitivity

71
Q

The slope of the calibration curve at the concentration of interest

A

Calibration sensitivity

72
Q

The lowest analyte concentration likely to be reliably distinguished from the blank and at which detection is feasible; alternatively, the minimum concentration of analyte that can be detected at a known confidence level. Practical definition is the analyte concentration that gives a signal equal to the blank plus 3 standard deviations of the blank

A

Limit of detection (LOD)

73
Q

The useful range of an analytical method, that extends from the limit of quantitation (LOQ) to the limit of linearity (LOL).

A

Dynamic range

74
Q

The lowest concentration of a substance that produces a quantitative result within specified limits of precision and bias.

A

Limit of Quantitation (LOQ)

75
Q

The concentration of an analyte at which the calibration curve departs from linearity by a specified amount, usually 5%.

A

Limit of linearity (LOL)

Instrumental Analysis (45 decks)

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