EXAM A

Question 1

If the linearity of an instrument is 20%T to 80%T. The sample resulted in a 10%T. What should be done?

Answer 1

need to dilute because 10%T means that the sample is too concentrated (less light can get through)

Question 2

What is the purpose of the monochromator?

Answer 2

allows you to pick a specific wavelength

Question 3

Identify the purpose of the second beam of a dual beam spectrophotometer. If the blank is placed in the second beam, what is the additional purpose of this channel?

Answer 3

The second beam passes through the reference cell (blank) and then on to the second rotating disc, where it will pass through the transparent section straight through to the detector, to determine the intensity of light that will be used as I0, which is compared to intensity of light of the sample being measured to determine the absorbance of the sample. This allows for making simultaneous corrections for changes in light intensity, grating efficiency, slit width variation, etc. This method is useful for obtaining spectral curves.

Question 4

Calculate the concentration of an unknown solution given the concentration and absorbance of a standard and the absorbance of the unknown solution.

Answer 4

-

Question 5

What kind of flame is used for Flame Emission Photometry?

Answer 5

Nitrous oxide acetylene flame

Question 6

device used to isolate a certain wavelength or range of wavelengths; usually refers to prisms or grating

Answer 6

Monochromator

Question 7

Flame Emission Photometry:

Alkali metals are relatively easy to excite in a flame, such as ____ (yellow), ____ (red-violet ), Li (red)

Answer 7

Na, K

Question 8

What is a main difference between Flame Emission Photometry and Atomic Absorption Spectrophotometry?

Answer 8

FEP- emission of light

AAS- absorption of light

Question 9

Atomic Absorption Spectrophotometry:

The source emitting radiant energy is called a ____________ lamp.

Answer 9

hollow-cathode

Question 10

____ and _____ are important elements in atomic absorption spectrophotometry.

Answer 10

Ca, Mg

Question 11

measurement of the reduction in light transmission caused by particle formation, and it quantifies the residual light transmitted; sensitivity is limited by the photometric accuracy and sensitivity of the instrument used; instruments used for this assay can be used for other assays (ex. enzyme assay or color development)

Answer 11

Turbidimetry

Question 12

measurement of a portion of the light that is scattered at a variety of angles; sensitivity depends on the absence of black or background scatter; signal magnified by photomultiplier; it is strictly needed and has limited use in other assays

Answer 12

Nephelometry

Question 13

Turbidimetry and Nephelometry both are dependent on measurement of…

Answer 13

of light scatter. Quantitative relationship is between the size and number of the particles

Question 14

What is the purpose of the second filter of a fluorometer?

Answer 14

the second filter only allows the emitted light to hit the detector

Question 15

Fluorometer:

What is used when the wavelength is below 320 nm?

Answer 15

Quartz cuvette

glass or polyacrylate cuvettes do not have optimum optical properties - transmission% is low

Question 16

What is the principle of fluorescence polarization and how is it applied to fluorescence immunoassay competitive binding? (FPIA)

Answer 16

Patient analyte competes with labeled analyte for Ab binding site in this homogenous assay. Polarization optics are used to detect polarization. If labeled analyte binds to Ab then polarization is retained due to slower rotation of the large complex. If labeled analyte does not bind Ab then there is a decrease in polarized light due to the fast rotation of the small analyte. The relation of signal to unknown is indirectly proportional.

Question 17

How do you calculate the osmolality of a solution given the freezing point?

Answer 17

Osmolality (mOsm/kg) = (FP depression/1.86) * 1000

Question 18

What two molecules are measured using solid glass membrane?

Answer 18

H and Na (check this one)

or is it ammonia and Mg?

Question 19

Ion selective electrodes:

__________: Has a liquid-membrane design, uses exchanger valinomycin (ionophore) which allows K+ to pass through the hydrophobic membrane

Answer 19

Potassium

Question 20

The electrical charge of a solute is dependent what two things?

Answer 20

-pH
-isoelectric point of the solute