Exam 1 Flashcards
(109 cards)
1
Q
What is the proper three step procedure for cleaning analytical glassware ?
A
The three step procedure for \_\_\_\_\_\_ is Wash with: detergent solution tap water x3 deionized water x3 If you're doing trace analysis, use ultra-pure water
2
Q
How can you use water to test if glassware is properly cleaned?
A
______ should be able to be coated with a uniform and unbroken film of water
3
Q
What are the three special treatments for glasswear?
A
The three ____ are:
Ultrasonic cleaning,
Using organic solvent
Using cleaning solution
4
Q
What are the five grades of chemicals?
A
Technical/Comercial grade USP Grade Reagent Grade Primary Standard Grade Special Purpose
5
Q
What are Technical/ Commercial Grade chemicals?
A
______ chemicals have the lowest purity, and is used only when purity is not a main criteria, like for cleaning
6
Q
What are U.S Pharmacopoeia (USP) grade chemicals?
A
______ chemicals have limits on impurities which are hazardous to health
7
Q
What are Reagent grade chemicals?
A
______ chemicals conform to standards set by ACS that list their analytical results on a label
8
Q
What are Primary Standard grade chemicals?
A
_______ chemicals have extraordinary purity, are carefully analyzed, and state analytical results on the label, Usually provided by NIST ( National Institute of Standards and Technology)
9
Q
What are Special Purpose Reagent chemicals?
A
_______ chemicals are Spectro-grade and HPLC grade
10
Q
What are the three concentrations used in trace analyses? Describe them in terms of 10e and g/Liters
A
ppm (million) 10e-6; mg/L
ppb (billion) 10e-9; ug/L
ppt (trillion) 10e-12 ng/L
11
Q
How would you prepare a 1:4 HCL solution?
A
You would prepare a 1:4 HCL solution with 1 part HCL and 4 parts water
12
Q
What is a stock solution?
What is the difference between a primary and secondary stock solution?
A
A ______ is a solution with a high concentration, used to prepare working solution. A primary ____ might have to high of a concentration to make working solutions from, so you could make a secondary ____ out of the primary. That solution would have a lower concentration, making it easier to use for working solutions with low concentrations.
13
Q
What is working solution?
A
A _____ is a solution with a lower concentration, made by diluting a stock solution, right when it is going to be used for a procedure so it is fresh.
14
Q
What kind of technique is Gas Chromatography?
A
____ is a separation technique
15
Q
Write the step by step process of what happens in a Gas Chromatograph
A
In _______
The sample is injected > Vaporized > it enters the head of the GC column > the analytes are carried by the flow of the carrier gas through the column> and finally the mixture is separated due to the different traveling speeds of the samples components.
16
Q
What is the definition of Chromatography?
A
______ is a separation science, which means separating a mixture into its different components.
17
Q
What are the parts of the gas chromatograph instrument?
A
Carrier gas>flow controller>injection port>column in oven>detector>recorder
18
Q
Why do the column and analyte need to have different polarities?
A
The column and the analyte need to have different polarities because if the polarity is the same, the analyte would stay in the column but if the polarities differ, the analyte will not want to be in the column, and it will pass through quickly.
19
Q
What temperature is the GC injector kept at? Why?
A
The GC injector is kept at about 50C, because that is greater than the boiling point of the component with the highest boiling point in the sample (the least volatile component).
20
Q
What are the two modes of injection for the capillary column?
A
The two ________ are:
Split, which is used for normal analysis and
Splitless, which is used for trace analysis.
21
Q
What is a Flame Ionization Detector? How does it work?
A
The principle of the ______ is that it contains a flame made of hydrogen gas and air. Organic compounds are combusted in the flame and produce ions and electrons. Those electrons are collected by a collector electrode and generate a tiny current, around 10e-12 Amps. The signal generated is amplified to create a chromatogram.
22
Q
What kind of compounds are analyzed in GC?
A
GC is used to analyze organic compounds. For Inorganic compounds, other methods can be used.
23
Q
What is a chromatogram?
A
A ____ is the resulting spectra from the instrument
24
Q
What are the two important pieces of information you get from a chromatogram?
A
The two important pieces of information you get from a______ are retention time and peak area
25
What is retention time?
______ is the time required for an analyte to reach the detector after sample injection
26
Compare tM,tR,and tS. How are they related? What does each represent?
tM is the void/dead time. tM is a measure of the average rate of migration of mobile phase.
tS is the time retained by the stationary phase, also known as adjusted retention time.
tR is the retention time of the analyte, tM + tS= tR.
27
What is the significance of peak area in terms of analyte?
The _____ is proportional to how much analyte is inserted. It is critical for quantitative analysis. The more analyte, the higher the peak.
28
What are the three major parameters that affect separation in GC?
The four __________ are
The type of column
The temperature
and the flow rate
29
What are the two types of column that are used in GC?
The two ________ are polar (carbowax) and non polar (DB-1,PDMS)
30
What are the two types of temperature settings used for GC?
The two _______ are Isothermo, which is the oven temp is constant and
Temperature ramping/programing, which is increasing column temperature continuously or in steps during analysis
31
What steps should you follow when preparing a GC method?
First, consider if you need a polar or non polar column. Second, Figure out the best way to program the temperature. The temperature must be changed to achieve the best separation over the best amount of time, this is done by trial and error during method development. Finally, figure out the best flow rate, because flow rate affects retention time. These are all separation conditions that need to be reported.
32
How would you identify solvents from your unknown based on your chromatogram?
To _____ based on the chromatogram,
| compare the retention time and experimental separation conditions to known standards under the same conditions.
33
What should you do if two or more solvents happen to have the same retention time (co-elution)?
If ______ happens, we have to figure out how to separate them. First go back and look at the parameters that affected separation. The best method is usually to change the column. Try polar and non polar column, use the one with the most peaks.
34
Why is red solution red?
______ because When light passes through the solution, the solution has allowed the red component of white color to pass through and absorbed the complementary colors, yellow and blue.
35
What would make one solution a darker red than the other?
The solution would ____ the more concentrated it is. The more concentrated the solution, the more yellow and blue light is absorbed, and the more intense the color is detected to the eye.
36
What does Uv-Vis spectroscopy measure ? Why is this useful?
________ measures the transmittance or absorption of UV or visible light. This is useful because every molecular species is capable of absorbing its own characteristic frequencies of electromagnetic radiation.
37
How would you identify an unknown drug through its Uv-Vis spectrum?
To ______, you would find the characteristic absorption wavelength and compare it to lit values and chemical standards. You must also compare factors that may affect absorption, make sure they are consistent throughout.
38
How would you use Beer's law for quantitative analysis?
First, you would Select the wavelength with maximum sensitivity (absorption). Determine the relationship between absorbance and concentration, establish a calibration curve, and use it to find the unknown concentration.
39
What are the four goals for UV-parameters experiment?
The four _____ are:
investigate the parameters that affect absorption,
to understand instrument calibration,spectral resolution,
and instrument performance
40
What are the four types of cuvettes used in lab?
```
The four ______ are:
Far UV: Quartz
Near UV: Fused Silica
Plastic
Glass
```
41
Whats the difference of the UV-vis spectrum obtained by these four typed of cuvettes?
Each cuvette can absorb up until a certain limit, each has a different limit.
42
What is the best strategy for carrying out the conway experiment?
The _____experiment involves the color development caused by a chemical reaction in a conway cell, then the color is measured by a UV-Vis spectrometer. On Day 1, prepare the sample, on day two let it develop, on day three measure the samples by UV-Vis. Then find the unknown concentration by building a standard calibration curve.
43
Where is the Group Frequency Region and what is it used for?
The _______ region is about 3700-1200cm-1. It is used to determine functional groups
44
Where is the Fingerprint region and what is it used for?
The ______ is 1200-600cm-1. It is used to make detailed comparisons of the small differences in structure and constitution. Small differences in the structure make significant changes in absorption spectrum in this region.
45
What is the KBr pellet procedure?
In the _____ procedure, you mix analyte with dry Kbr powder in a mortar and pestle, then apply high pressure 10k-15k psi.
46
Why must the KBr be dry in the KBr pellet?
The pellet must be dry because moisture exhibits bands at 3450 and 1640 cm^-1
47
What is the procedure for the Thin film salt plate technique?
In the _____ procedure, you dissolve sample in a small amount of methylene chloride and put one or two drops onto a NaCl salt plate, squeeze the solution between two plates to give a thin film.
48
What is the procedure for the Mulls technique?
In the _____ procedure, you grind a small amount of sample with NUJOL or Fluorolube and put a small amount on the salt plate to obtain the spectrum.
49
What is the procedure for the liquid cell technique?
In the _____ procedure, a sample is dissolved in an organic solvent such as CCl4 and CS2 and the spectrum is obtained
50
What range is quartz and fused silica cuvettes useful for in UV-VIS spec?
___ and ___ cuvettes are useful in the the uv. Quarts for far, fused for near
51
what range is a plastic and glass cuvette useful for in UV-VIS?
____ and ____ cuvettes are useful for the visible range of light
52
Under what circumstance would you use a procedure like the Conway experiment?
The _____ is used when the analyte can not be analyzed directly. In this case, chemical reactions can be introduced to convert the analyte into a species that can be analyzed.
53
What are the two Classical Analytical methods?
The two ___ methods are
Gravimetric analysis and
Volumetric analysis
54
What medium is used in gravimetric analysis? What are some things they are used for?
_____ analysis is done by mass. Some things ____ analysis is used for is precipitate in formation, drying, weighing, and calculation of percent species
55
What medium is used in Volumetric analysis? What are some things they are used for?
_____ analysis is done by titration. The end point is found and used for calculation of % species.
56
What are the three modern instrumental methods? What are two others?
```
The three ______ are:
Spectroscopy
Seperation
and Electroanalysis
Some others are radiochemical and thermal analysis.
```
57
What are two types of spectroscopy?
Two types of ____ are:
Atomic _____
and Molecular _____
58
What is instrumental separation called? What kinds of species can be separated?
______ is known as chromatography.
The species that can be separated are:
Gas, Liquid, Ions, and more.
Theres also capillary electrophoresis
59
What types of analysis is performed with electroanalysis?
_______ measures current, voltage, pH electrode, ISE, Voltammetry
60
What are the two kinds of information instruments give us? What are the 4 steps to obtaining that information?
The instrument can give qualitative or quantitative information. To obtain that information:
First provide a stimulus to the analytes,
then the analyte responds to a stimulus in a unique way
then that response is collected and measured
and finally, that measurement is used to find out useful information.
61
What is the definition of calibration? How us calibration usually done?
The definition of ____ is to determine the relationship between the analytical response and the analytical concentration, such as by generating a calibration curve. This is ususally done using chemical standards.
62
What are the three Calibration methods?
The three _____ methods are:
External ____
Internal ____
and Standard addition method
63
What are the two things the External Standard Calibration is used for?
_______ calibration can be used to Calibrate instruments
| or determine the unknown concentration in a sample.
64
What is an example of calibrating an instrument by External Standard Calibration?
An example of ______ is a calibrating pH meter by using a standard buffer with a known pH
65
What are the three steps to determine an unknown concentration in a sample by External Standard Calibration?
The three steps to _____ are:
1: Prepare a series of external standards containing the analyte in known concentrations
Then, obtain the response signal as a function of the known alalyte concentration to establish a calibration curve. The response signal may be absorbance, peak height, peak area, ect.
Finally, determine the unknown concentration based on the obtained calibration curve.
66
How does a calibration curve work in terms of math?
In a _____ a linear relationship is found and expressed mathematically. Then, based on the signal you obtained from the experiment, you can determine the unknown concentration.
67
What is the Least-Squares method
The _______ method is the mathematically way to get the best-fit equation.By using this method, we are also performing regression analysis.
68
What are the two benefits to regression analysis.
The two benefits of ______ are that it provides the means for :
objectively* obtaining a best fit line and
Specifying the uncertainties associated with its use
69
What are the three assumptions made when using the least square method?
The three assumptions made when using the _____ method are:
1. That a linear relationship exists between the measured response, y, and the standard analyte concentration, x. Expressed as the regression model, y=mx+b. m=slope b=y-intercept.
2. That there is no error in the x value (the concentration). Any deviation of the point from the straight line is from error in the measurement.
3. The same response will be obtained for the same analyte concentration that is present in the sample and in the standard.
70
What is the definition of a residual in terms of finding the least square line?
The ______ is the vertical deviation of each point from the straight line. The least square method aims to minimize the sum of the square of the residuals using y=mx+b.
71
What is R^2?
_____ is the coeficient of determination. it is usually a number smaller than, but close to 1. The closer it is to 1, the better the linear regression fit is. For routine analysis, it is often required to be better than 0.99.
72
What is R?
____ is the coefficient of correlation
73
What is a random error in terms of calibration curve uncertainty? How do we make up for this?
_____ can influence the accuracy of results obtained from the calibration curve. We make up for this by calculating the standard deviation.
74
What is the Ideal blank?
| What is the difference between a solvent blank and a reagent blank?
The ideal ____ is identical to the sample, but without the analyte.
A Solvent ____ contains the same solvent in which the sample is dissolved
A reagent _____ contains the solvent plus all reagents used in sample preparation
75
What is the matrix effect?
The ______ can affect the analysis, making it difficult to get an accurate result using the calibration curve.
76
What are three causes of the matrix effect?
Three causes of the ______ are that the sample may contain:
1) chemical properties similar to the analyte,
2) Reagent or solvent used in the sample prep
3) decomposition of certain species
77
What kind of sample matrix are usually complicated?
Biological ____ are usually complicated such as blood, hair, urine, and tissues.
78
What are three ways to reduce the matrix effect?
Three ways to reduce _____ are:
| A matrix modifier, dilution, and matrix matching.
79
What is a matrix modifier?
A _____ is added to samples, standards, and blanks in sufficient amounts to make the analytical response independent of the concentration of any interfering species. For example, a buffer may be added to maintain pH.
80
How is dilution used to reduce the matrix affect?
If the interfering species produces no significant effect below a certain concentration level, the solution may be ______ to reduce the matrix affect.
81
What is Matrix matching?
______ is an attempt to duplicate the sample matrix by adding the major matrix constituents to the standard and blank solution. For example, adding synthetic urine, seawater, ect.
82
Explain the Internal Standard Method
In the ______ method, a known , and fixed, amount of reference species, named the internal standard, is added to all samples, standards, and blanks. It should be a species chemically and physically similar to the analytes. The response signal is not the analyte signal itself, it is the ratio of the analyte signal to the reference species signal.
The calibration curve is prepared in which the y-axis is the ratio of responses and the x-axis is the analyte concentration in the standards.
83
Why would you want to use the internal standard method?
Ideally, the internal standard would give a constant response in all analysis, but there might be uncontrollable reasons that result in a change of the response. We can compensate for the uncertainty caused by this by using the ratio of analyte signal to IS signal, (if these influence both the analyte and the internal standard to the same proportional extent). BASICALLY: if something internal is messing up, the internal standard will make you aware of it.
84
What is the Standard addition method. When should it be used?
_____ method is a powerful method used to handle difficult sample matrixes. The ______ method should be used when the sample matrix is complicated or when its difficult or impossible to duplicate the sample matrix.
85
What are the six steps to using the standard addition method?
The six steps to using _____ are:
1. Take at least two portions of the same volume of sample
2. Spike a series of known amount standards into these two samples
3. Measure the samples,
4. Assume a linear response
5. Establish the linear regression
6. calculate the concentration, don't forget to consider dilution factors
86
What are the three figures of merit for analytical methods?
The three ______ for analytical methods are:
the Detection limit,
the Dynamic linear range,
and the reproducibility
87
What is the Detection Limit?
The _____ is the minimum concentration or mass of analyte that can be detected at a known confidence level. Signal/Noise must be greater than 3 standard deviations of blank.
88
What is the Dynamic Linear Range?
The _______ is the concentration range that can be determined with a linear calibration curve.
89
What is the lower limit of Dynamic Linear Range?
The ____ of the dynamic linear range is the limit of quantitation, 10 standard deviations of the blank.
90
What is the upper limit of Dynamic Linear Range?
The ____ of dynamic linear range is usually about 5% from linearity. It is the concentration at which the analytical signal or slope of the calibration curve deviates by a specified amount from the linear relationship.
91
What causes deviations from linearity in the dynamic linear range?
______ from linearity in dynamic linear range are caused by a non-ideal detector response, or a chemical effect.
92
What is reproducibility in terms of analytical methods?
_____ describes precision through standard deviation, and relative standard deviation( also known as coefficient of variation (CV)
93
What is the formula for CV or RSD? What are the acceptable results in instrumental analysis?
_____ = standard deviation/mean x100.
<=10% is okay
<=5% is good
<=2% is Excellent
94
What are the five factors you should consider when you choose or develop an analytical method?
The five factors that should be considered when ______ are:
- Cost and availability of the instrument
- Ease and convenience
- Speed
- Skill required of operator
- Per-sample cost
95
What are the 6 performance characteristics of instrumental methods?
```
The six _____ are:
Pricision
Bias
Sensitivity
Detection limit
Dynamic range
and Selectivity
```
96
What are the figures of merit for the precision criteria?
The figures of merit for ____ are:
absolute standard deviation
Coefficient of variation
varience
97
What are the figures of merit for the bias criterion
The figures of merit for ____ are:
| Absolute systematic error and relative systematic error
98
What are the figures of merit for sensitivity?
The figures for merit for ____ are:
calibration sensitivity
and analytical sensitivity
99
What are the figures of merit for Detection limit?
The figures of merit for ___ are:
| The blank plus 3 times standard deviation of the blank
100
What are the figures of merit for dynamic range?
The figures of merit for ___ are:
| The concentration limit of quantitation (LOQ) or Concentration Limit of Linearity (LOL)
101
What are the figures of merit for selectivity?
The figures of merit for ____ are:
| Coefficient of selectivity
102
Why it the signal to noise ratio important ? (S/N)
The ______ is important for comparing analytical methods or instruments. If the signal is sufficiently higher than the noise, it is not difficult to make a reliable measurement.
103
What are the two types of noise encountered in instrumental analysis?
The two types of ____ encountered in instrumental analysis are Chemical and instrumental noise
104
What causes Chemical noise?
_____ is caused by uncontrollable variables that affect the chemistry of the system. For example: temperature and pressure affect chemical equilibrium, or fluctuations in relative humidity.
105
What are the three types Instrumental noise?
The three types of _____ are:
White noise
Flicker noise
and environmental noise.
106
What is White noise? what are the two types and their causes?
____ noise is unavoidable instrumental noise.
The two types of ___ noise are:
Thermal noise, which is caused by random motions of charger carriers (like electrons) leading to voltage fluctuation.
and
Shot noise which is when charge carriers cross a junction in an electrical circuit.
107
What is flicker noise?
____ noise is 1/f but we don't know why. It is inversely proportional to the frequency of the signal. This is significant for low frequency signals.
108
What is environmental noise
_____ noise is caused by the surroundings
109
What are the signal-to-noise-enhancement stategies?
```
______ can be enhanced with:
Software OR
Hardware through:
grounding and shielding,
difference and instrumentation amplifiers
analog filtering,
and modulation.
```
