Chapter 4 Analysis

Front 1

There is a relationship between the concentration of a substance in solution (such as bilirubin in serum) and the amount of radiant energy absorbed or transmitted through that solution under controlled conditions. This is the principle underlying spectrophotometry. The equation that mathematically describes this relationship is the Beer-Lambert law.
The equation is: A = abc = 2 - log %T
where A = absorbance, a = absorptivity of compound under standard conditions, b = light path of solution, c = concentration of compound, %T =percent transmittance.

Back 1

Beer-Lambert law: the concentration of a substance is directly proportional to the amount of light absorbed or inversely proportional to the logarithm of transmitted light.

Front 2

What is the chief use of atomic absorption spectrophotometry in today's laboratories?

Back 2

Measurement of metals such as lead, and others in the field of toxicology (heavy metals, industrial exposures, etc.).

Front 3

What is the chief advantage of fluorescence spectroscopy?

Back 3

Fluorescence spectroscopy, or luminescence, is characterized by high sensitivity

Front 4

In nephelometry the Rayleigh-Debye theory describes the scattering of light in relationship to the light wavelength and the size of the particles encountered by the light. If the wavelength and the size of the particles are approximately the same, then some light will scatter at an angle and some will scatter forward. What is the main application of nephelometry in the clinical laboratory?

Back 4

Ag-Ab reactions, particularly to measure proteins, such as apolipoproteins and immunoglobulins, and drugs.

Front 5

Bacterial growth in broth cultures, clot formation in coagulation.studies, and protein levels in urine and CSF are often measured by turbidimetry, which measuresa the reduction of light in the forward direction

Back 5

This is turbidimetry.

Front 6

Osmometry is the measurement of the osmolality of a solution. Although Henry does not dwell on this, let's take a moment to recall that osmolality is millimoles of solute per kilogram of solvent. This is the measurement we see for serum and urine concentrations. Serum osmolality is 275-295 mOsm/kg, urine is 300-900 mOsm/kg. The closely related term, osmolarity, is only occasionally used, and refers to milliosmoles of solute per liter of solution. Osomometry is based on measuring the changes in the colligative properties of a solution. These four properties are:

The most commonly used in the clinical laboratory is?

Back 6

The four colligative properties are osmotic pressure, freezing point, boiling point, and vapor pressure. freezing point osmometers are in common use

Front 7

In flow cytometry, cells are suspended in fluid and pass single file through a sensing point where the quantity and characteristics of the cell can be determined. Scattered light from an argon beam travels both forward, giving an indication of cell size, and in the 90 degree, or side scatter direction, showing cell complexity.

Back 7

foward scatter=cell size
side scatter=complexity

Front 8

What is the main use of the electrical impedance method, which measures the change in electrical resistance across an aperture when a particle in a conductive liquid passes through the aperture?

Back 8

hematology

Front 9

What is the glass electrode used to measure?

Back 9

The glass electrode is still used to measure the hydrogen ion concentration. This is the pH electrode.

Front 10

Potentiometry is the measurement of voltage between two electrodes in a solution. If you have an unknown concentration of an ion such as Na, and a metal of that .same sodium ion across a membrane, you can measure the electrical potential across the interface between the ion and the metal. The measured cell potential is related to the molar concentration of Na (or any ion) by what equation?

Back 10

the nernst equation

Front 11

Electrophoresis is the separation of compoungs, usually proteins, based on their electrical charge. The proteins with greater net charges move??

Back 11

Faster. The greater the negative charge, the faster the molecule will move toward the positively charged anode.

Front 12

What does denitometry add to simple electophoresis?

Back 12

quantifies the protein fractions

Front 13

Gas chromatography is used to measure volatile substances and those that can be converted to a volatile form. We can change the retention time of compounds, by changing what parameter?

Back 13

Column temperature can be increased to reduce the retention time and speed up the throughput of gas chromatography

Front 14

Liquid chromatography (LC) is more effective than gas chromatography for compounds that are unstable or have poor volatility. Older types of LC include paper, thin-layer, ion exchange, and exclusion. The newer method is called high­ performance liquid chromatography (HPLC). How does HPLC compare with the older methods in terms of analysis time?

Back 14

shorter analysis time is achieved by the high pressure used to push the liquids through

Front 15

True/False:A disadvantage to HPLC is the need to regnerate the columns with each new run. This adds to the cost of running each test.

Back 15

False. The columns can be used many times without regeneration.

Front 16

Characteristic fragmentation of moleecules when bombarded with electrons or fast atoms such as argon describes the trechnique called?

Back 16

This is mass spectrometry. This technique is used extensively in toxicology and therapeutic drug monitoring.

Front 17

What is the key application of the method of scintillation counting, the measurement of flashes of light that occur when gamma rays interact with matter?

Back 17

Radioimmunoassays for hormones is the key application .

Front 18

Briefly describe the composition and advantages of the most common type of glassware used for volume measurements in the clinical laboratory.

Back 18

This is borosilicate glass. It is characterized by a high degree of thermal resistance, low alkali content, and does not contain such elements or substances as magnesium, lime, zinc, heavy metals, arsenic or antimony.