2 - Isoproterenol Flashcards
What is isoproterenol?
Bronchodilator that relaxes lung smooth muscle and improves breathing in asthma, bronchitis, and emphysema
How is isoproterenol available?
Injection
What is the point of calibration?
- Compare to a defined standard or reference
- Essential for understanding and interpreting data to establish a relationship between quantities
Difference between relative and absolute calibration?
- Relative = evaluated by comparison to standards; used in pharmaceutical analysis for quantitative measurements
- Absolute = relies of physical/chemical constants; used in instrumentation calibration
Difference between one-point calibration and multiple-point calibration? Which was used for this experiment?
- One-point = uses one standard as a comparison that is reliable and reproducible; zero measurement produces zero response; linear and can’t extrapolate
- Multiple-point = uses > 3 different standards (other than zero); more accurate/reliable and extrapolation can be done; linear (y = mx + b where y = absorbance and x = concentration); *used for this lab
Which wavelengths are UV and which are visible?
- UV = 200-380 nm
- Visible = 380-800 nm
Advantage of UV/Vis spectrophotometry?
- Easy, inexpensive, and robust approach for quantitative measurement of drugs
- Routine method for physical and chemical characterization
UV/Vis spectrophotometry is routine for ____
Characterization of drugs
What is the basis of spectrophotometry?
The relationship between concentration of an analyte and the intensity of its light absorption
Disadvantages to UV/Vis spectrophotometry?
- Assay selectivity is low b/c depends on the chromophore (extended systems of double bonds)
- Analysis of mixtures is difficult because 2 compounds may have maximum absorbance at the same wavelength
What 2 factors govern absorption of radiation by a molecule?
- Structure of the chemical molecule
- Wavelength of radiation
Why does spectrophotometry use longer wavelengths (> 200 nm)?
- Short wavelength UV radiation (< 150 nm) can cause the strongest bonds in organic molecules to break and thus is very damaging to living organisms
- Longer wavelengths allow weaker bonds to be excited
When will absorption take place for molecules w/ more double bonds?
Longer wavelengths and w/ greater intensity
Formula for Beer-Lambert law and what each parameter means
A = A(1%, 1 cm) bc
- A = absorbance
- A(1%, 1 cm) = absorbance of a 1% (1 g/100 mL) solution in a 1 cm cell
- b = pathlength of the cell in cm
- c = concentration of the analyte (mol/liter)
3 basic components of a UV/Vis spectrophotometer
1) Light sources - deuterium lamp for UV (190-350 nm) and quartz halogen or tungsten lamp for visible (350-900 nm)
2) Monochromator - disperses light into wavelengths; can also rotate wavelengths so they can pass through the sample
3) Optics - splits the light beam to pass through 2 sample compartments; use a blank to correct the reading (blank is usually the solvent in which the sample is dissolved)
What are some examples of UV/Vis spectrophotometry use in pharmaceutical analysis?
- Partition coefficient (amount of drug in aqueous or organic layer)
- Solubility (concentration of drug that has gone into solution)
- Drug release (concentration of each sample during dissolution where excipients don’t interfere; may need to do chromatographic separation first)
What are 2 other types of spectrophotometry?
Infrared and atomic
Why was isoproterenol checked for colour, clarity, and foreign substances?
Shouldn’t be used if colour is pinkish or darker than slightly yellow or it contains a precipitate
Which substances were added to the isoproterenol in calibration preparation and why?
- Ferrous sulphate citrate
- Aminoacetate buffer (causes a reaction and increases volume)
What was used as a blank?
Distilled water
What calculations were used for this experiment?
- Dilution factor for stock standard solution = 10 mL/200 mL and then 14 mL/25 mL = 0.028
- Dilution factor for final test solution = 1 mL/25 mL and then 20 mL/25 mL = 1/125
- Original concentration = diluted concentration/ dilution factor
- % drug content = original concentration / 5 mg/mL (theoretical concentration)
