Term
What are the 10 steps of the analytical method? 

Definition
1) Define the problem (quant. vs.qual) 2) Choose the method of analysis 3) Obtain appropriate sample 4) Determine amount of sample 5) Get sample into correct form 6) Eliminate interfering species 7) Run assay 8) Data reduction 9) Statistical analysis 10) Interpret the meaning of results 


Term
What's the general framework for instrumentation? 

Definition
Stimulus > Sample> Response 


Term
Difference between accuracy and precision. 

Definition
Accuracy= how close measurements are to the true value.
Precision = how close measurements are to each other 


Term
Explain the two types of errors 

Definition
1) random: indeterminate> equal high and low precision. 2) systematic: determinate> generates from a fixed cause, and is either high or low. affects our accuracy but its generally correctable. 


Term
What's relative standard deviation 

Definition
Comparing two numbers with standard deviations. Relative : s/ avg. x % rel std same thing times one hundred percent 


Term
What's the difference between x, s and Mu, delta in the context of confidence intervals? 

Definition
x, s = experimental sample mean and standard deviation; limited number of results; N < 20 Mu, delta = population/true; infinite number of measurements; N >20 


Term
What are two systematic errors that affect accuracy (bias)? 

Definition
1) constant: size of sample doesn't effect this; its the same magnitude (ex: calibration throws off subsequent measurements) 2) proportional: magnitude of error is proportional to sample; interferent in sample. 


Term
Corrections for systematic error 

Definition
1) constant > run a blank. 2) proportional > run a standard (standard= sample with a known concentration of analyte). 


Term
When would choose a type 1 ttest? 

Definition
When we want to see if experimental data agrees with a known value. tcalc = (Mu  x)(sq. root of N / s) If tcalc < ttable we get statistically valid results. 


Term
When would we use a type 2 t test? 

Definition
Compare 2 sets of experimental data which are replicates of a single sample: same method w/ 2 diff. analysts or 2 methods with the same analyst. You get 2 sets of data, each w/ Xa Xb and Mu a and Mu b. 


Term
When would you used a case 3 ttest? 

Definition
Compare 2 sets of data where individual measurements are made of multiple samples. tcalc = d/ sd *(sq. root of N)
where d = difference between set 1 and 2. 


Term
Why would we do an ftest? 

Definition
Allows us to compare error distributions of 2 sets of experimental data. fcalc = sa^2/ sb^2 (bigger one on top) If fcalc > ftest, they have different error distributions. 


Term
Why would you use the Qtest? 

Definition
Only if there is a particular data point that isn't part of the parent popluation. Qcalc = d (differnece between questionable point and its nearest neighbor) / w (difference between qst. pt. and the farthest point)
IF q calc < q table, you must keep the point 


Term
What are the 5 general principles in sample pretreatment? 

Definition
1) Should be done w/o losing analyte 2) Should include bringing analyte into the best chemical form. 3) should remove interferents from the matrix. 4) should be done w/o introducing additional interferents 5) should bring the analyte into the proper concentration range 


Term
What are some sources of loss in your sample? 

Definition
1) Adsorption: sticks to the surface (metal on glass) 2) Decomposition 3) nonquantitative transfer 


Term
How can you maximize your recovery? 

Definition
Optimize the chemical form, Minimize interferences, and optimize concentration 


Term
Standards: 2 Types of Instruments 

Definition
1) Direct measure: mass, volume 2) Indirect measure: instrument measures signal 


Term
Describe an external standard 

Definition
The sample is different from the standard (in physically different locations). when matrix is either simple or well defined.  one set of calibration solutions. 


Term
For external standards, what does the calibration curve depend on? 

Definition
The instrument, condition of the instrument at the time of analysis, and other materials in the matrix 


Term
When would you use/apply standard addition? 

Definition
When matrix is very complex, or when it contains proportional interferences. spike varying amts. of standard 1) known conc. of standard 2) const. amt of sample, 3) varying amt of standard 4) const total volume 


Term
For standard addition, on a graph of IR versus volume of standard, what does "Vs0" refer to? 

Definition
The negative of this value gives you the amount of standard you would've had to add to give you the same signal as the standard.
Cx = (Vs)0 Cs/ Vx 


Term
Describe the Internal Standard method 

Definition
spike a compound that's similar but different from our analyte add a known amt of internal standard (diff from analyte) 


Term
What are the criteria for a good internal standard 

Definition
1) similar molecular properties to analyte 2) distinguishable analytical signal 


Term

Definition
How close 2 samples can be in concentration and still produce a measureably different instrumental response 


Term
Describe calibration sensitivity 

Definition
Sensitivity can be determined by slope of the calibration curve. We want 2 samples close together, but produce a large difference in IR to be able to distinguish and measure them. 


Term
Describe analytical sensitivity 

Definition
Gamma = m/ s, where s= std. dev. of sample IR.
If you have another sample that falls within the same std. deviation of one sample, you won't be able to distinguish them. 


Term

Definition
The smallest concentration which produces a signal which can be statistically differentiated form the blank. Smin = Sblank + 3sblank
cmin = Smin b/ m 


Term

Definition
Range of concentration over which the instrumental response/ signal is linearly related to the concentration 


Term

Definition
ability of your method to distinguish signal from analyte versus signal from interferents.
S = maCa + mbCb + Sbl selectivity coeffic. Kb,a = mb/ma If K is small, method is selective 


Term
We're talking about light now. A high energy corresponds to what type of wavelength, and frequency? 

Definition
A short wavelength, and a high frequency 


Term
From high energy to low energy, list the types of radiation that you can have. 

Definition
Gamma, xrays, UV, Visible, Infrared, Microwaves, and Radiowaves 


Term
For the index of refraction, if there are two mediums that light can pass through (air and water for example), in what medium will the angle between the normal be smallest? 

Definition
In water; the greater the difference in the index of refraction, the more it bends. 


Term
Name two important facets of the Photoelectric Effect 

Definition
1) Light must have a critical/threshold frequency (doesn't matter what intensity the light is, the wavelength has to be shorter than the medium) 2) Light having greater than critical frequency causes ejected electrons to be ejected w/ increased KE 


Term
Atoms have ____ _____ energy levels, and can only absorb or emit certain frequencies of light. 

Definition


Term
Energy of light must equal _______ between any ___ ___ levels in the atom or molecule. 

Definition
the difference; 2 energy levels 


Term
Describe the three types of emission that can occur 

Definition
1) Line spectra: arise from atomic transitions (vphoton = E1E0/ h) 2) Band spectra: arise from molecules (they are broader) 3) Contiuum Spectra aka blackbody radiation (wavelength max = TK) 


Term
Name two types of absorbtion 

Definition
1) Atomic: no vibrational levels, only electronic 2) Molecular: electronic, vibrational, and rotational 


Term
When we measure absorbance, what are we actually measuring? 

Definition
The power in and power out. T = P/Po A= log T 


Term
What are the practical quantitative aspects of UVVis? 

Definition
1) Selection of lambda max 2) Prepare solns which have constant temp, electrolyte concentration, interfering species, pH 3) Cells or cuvettes (ideally usd matched ones) 


Term
What do we run a user baseline? 

Definition
To account or correct for differences in the cuvette 


Term
Important characteristics of UVVis 

Definition
1) wide applicability to both inorganic and organic 2) detection limit (E4, E5) 3) moderate selectivity 4) good accuracy 5) easy data acquisition 


Term
How about qualitative aspects of UVVis? 

Definition
Not done frequently because you get broad, few peaks  can get some functional groups must choose solvent carefully (must be transparent at wavelengths of interest)  polar solvents blur the spectrum 


Term
What's the difference between single vs. double beam UVVis? 

Definition
single beam= measure the reference than sample. double beam = measure reference and sample at the same time 


Term
Photometer versus Spectrophotometer 

Definition
Spectro: measure spectrum, photo: can't; measures absorbance at one wavelength. 


Term
Single versus Multichannel 

Definition
Single channel: looks at one wavelenght at a time Multichannel: all wavelengths at once 


Term
Null versus Direct read out 

Definition
Direct: directly measures P and Po Null: put optical wedge in until you get same intensity of P and Po. 


Term
What are some general characterisitics of the light source you need for UVVis? 

Definition
1) stable intensity> fairly intense 2) cover all wavelengths of interest (can't do) 3) easily replaced and realigned (can do) 


Term
Deuterium versus Tungsten light source 

Definition
Deuterium: UVlight source Tungsten: pass current through filament, resistive heating > blackbody radiation (3502500 nm) 


Term
Describe two slit experiment 

Definition
Interference pattern spacing: smaller spacing of slits yields larger spaces of diffraction pattern.  the place where diffraction spots fall is lambda dependent 


Term
What does n*(lambda) = d(sin i + sin r) tell you? 

Definition
It tells you where in space you get positive interference for a particular wavelength 


Term
Performance characteristics for monochromator 

Definition
1) Inverse linear dispersion 2) Resolution 3) Effective bandwidth 4) Scattered light 


Term
Inverse linear dispersion. Describe it. 

Definition
A small inverse linear dispersion is good (bad is large teheh) IF you want a low D1, you need a large space or large spectrum 


Term

Definition
How close 2 spectral peaks can be together and still be distinguished R = lambda/ delta lambda for 1 peak (detla lambda = Full Width Half Max
For 2 peaks, R = lambda ave/ delta lambda 


Term
What are factors that effect the resolution? 

Definition
Distance between the blazes, diffraction order (n), size of the grating R= nN 


Term
Describe effective bandwidth 

Definition
Range of wavelengths exiting the monochromator. delta lambda eff = D1 * w, where D1 = inverse linear dispersion, and w = width of the slit 


Term
What size bandwidth will give you a greater sensitivity? 

Definition
A larger bandwidth; more light, more sensitive. BUT, if you have an analyte and interferent, you need a small bandwidth in order to distinguish the two (sensitivity vs. selectivity) 


Term
What's the effect of scattered light on beer's law? 

Definition
You get nonlinearity, and an erroneous low absorbance. 


Term
Colored glass filter vs. Interference filter 

Definition
1) colored glass: every thing else is absorbed except for colored wavelength 2) interference: destructive interference for all other wavelenghts except for wavelength of interest. 


Term
Sample and Reference cells Measure P and Po simultaneously vs. in series 

Definition
1) Simultaneously: minimize time between P and Po, difference in detector response between cause errors 2) series: chopper! mirror = sample, holes = reference 


Term

Definition
Transduce our signal from a nonelectronic domain to an electronic domain. 


Term

Definition
Taking a small optical signal, and transducing it (a multiplying it) to a large electronic signal.  each dinode multiplies the number of electrons, 1 photon = 10^7 electrons 


Term
Performance characteristics in PMT 

Definition
1) Good sensitivity (small number of photons gives a reasonable current) 2) Consistent response regardless of lambda 3) High gain (1 photon > lots of electrons) 


Term
Multichannel Detectors PMT vs. Array 

Definition
PMT: exit slit determines bandwidth; scan Array: all multichannel is single beam,gives us spectrum chunk at one time 


Term
For array of detectors, what must you change about the monochromator? 

Definition
You must remove the exit slit, so the light is open to all detectors (the width of each detector is the band width or the pixel) 


Term

Definition
 solid w/ dissociated electrons. Electrons can move w/o being attached to a particular atom or molecule. Holes or electrons moves about = both can be an electrical conductor.  electricity conducted by electrons (ntype) or holes (ptype) 


Term
An ntype semiconductor is doped w/ group __. An ptype semiconductor is doped w/ group __. 

Definition
ntype: group 5. ptype: group 3. 


Term
What are the 4 limitations of Beer's law? 

Definition
1. Only works for dilute solutions. 2. Equilibrium pushes system to chemical deviations 3. Polychromatic deviations (this is why we measure absorbance at flat region). 4. Stray radiation (light which reaches the detector but hasn't originated from the light source and through the sample). 

