Mdcm 603 Pharmaceutical Analysis

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gross errors

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easy to recognize because they involve a major breakdown in the analytical process such as samples being split, wrong dilutions being prepared, or instruments breaking down or being used in the wrong way

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systematic errors

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characterized by precise and inaccurate measurement results

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random errors

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characterized by widely scattered ie. imprecise, measurement results

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standard deviation

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the calculated value provides a fomal expression of the scatter in the results from an analysis rather than the visual judgement shown previously

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analytical procedure

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provides an exact description of how the analysis is carried out

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precision

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expresses the closeness of agreement (degree of scatter) between a series of measurements obtained from multiple sampling of the same homogenous sample

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repeatability

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the precision obtained under the same operating conditions over a short period of time (an assay is repeated by the same person using the same equipment)

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intermediate precision

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expresses the within-lab variation of precision when the analysis is carried out by different analysts, on different days, and with different equipment

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reproducibility

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expresses the precision between labs such as when a method is transferred from one part of a company to another

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accuracy

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the simplest method is to compare a substance being analyzed with a reference standard analyzed by the same procedure (the reference standard is a highly characterized form of the durg that has been subjected to extensive analysis

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system suitability

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relates to the performance of the analytical equipment (the four Q's rule)...design qualification, installation qualification, operational qualification, and performance qualification

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analytical blank

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consists of all of the reagents or solvents used in an analysis without any of the analyte being present

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calibration

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comparison of the value or values of a particular parameter measured by the system under strictly defined conditions with pre-set standard values

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limit of detection

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the smallest amount of an analyte which can be detected by a particular method

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limit of quantification

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the smallest amount of an analyte which can be quantified reliably

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linearity

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most analytical methods are based on processes where the method produces a response that is linear and which increases or decreases linearly with analyte concentration

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range

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refers to the interval between the upper and lower concentration of an analyte for which an acceptable level of precision and accuracy has been established

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robustness

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evaluated to determine how resistant the precision and accuracy of an assay are to small variations in the method (eg. the stability of analytical solutions, or the length of sample extraction time)

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selectivity

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the measure of how capable a method is of measuring the analyte alone in the presence of other compounds contained in the sample

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sensitivity

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indicates how responsive the method is to a small change int he concentration of an analyte (may be viewed as the slope of a linear response curve)

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weighing by difference

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where the sample is weighed in a suitable vessel, ie. a glass weighing boat with a spout, and then transferred immediately to the vessel in which it is going to be analyzed or dissolved and the weighing vessel is reweighed and the difference between the wrights before and after transfer gives the weight of the sample

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percentage volume/volume (%v/v)

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often encountered in relation to the composition of mobile phases used in high pressure liquid chromatography

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percentage weight/volume (%w/v)

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usually used to express the content of an active ingredient in liquid formulations such as injections, infusions, and eyedrops

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percent weight/weight (%w/w)

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a common measure used to express the concentration of active ingredient in a formulation such as a cream

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parts per million (ppm)

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a common measure used for impurities in drug substances, particularly heavy metals and solvents

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physical properties of drug molecules, such as _____, along with simple chemical ________ and degradation reactions, play an important part in the design of analytical methods

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pka and partition coefficient

derivatisation

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when pka is used to measure acidic or basic strength,

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for an acid, the smaller the pka value - the stronger the acid, and for a base, the larger the pka value - the stronger the base

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the most effective range for a buffer....

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is 1 ph unit either side of the pka value of the weak acid or base used in the buffer

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the partition coefficient for a compound (P) can be simply defined as _______.

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P = Co/Cw
Co is conc. of substance in an organic phase, and Cw is conc. of substance in water

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the ______ the more a substance has an affinity for the organic media

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greater P

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many drugs contain ionisable groups and their partition coefficient at a given pH may be difficult to predict if more than one ionisable group is involved; however, _____.

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often one group in a molecule may be very much more ionized than another at a particular pH, thus governing its partitioning

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In zero order kinetics, the rate of degradation is _______.

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independent of the concentration of the reactants

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First Order Degradation. This type of degradation would be typical of ______.

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hydrolysis of a drug in solution

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the ________ about the double bond ensures that the stereochemistry of this drug and its isomer are different

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lack of free rotation

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when a compound ___________ about a particular carbon atom, the carbon atom is said to be a chiral center

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has no symmetry

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a chiral center arises when a carbon atom _______.

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has 4 structurally different groups attached to it

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the ______ attached to the chiral carbon atom, often hydrogen, is placed behind the plane of the paper with all of the other groups pointing forward

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group with lowest priority

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the priorities are assigned to the atoms immediately attached to the chiral center in order of ___.

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decreasing atomic mass

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when _______ is present in a molecule, there is the possibility of diastereoisomers

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more than one chiral center

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Analytical derivatization is employed for two reasons:
to improve the analysis by improving the _______.
to improve the analysis by improving chromatographic behavior or detectibility, ie., ______.

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selectivity

sensitivity

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analytical derivatization reactions are a form of synthetic organic chemistry in which the goal is ______.

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100% yield of a single pure product

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radiation in the wavelength range _______ is passed through a solution of drug

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200-700nm

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most drug molecules absorb radiation in the UV region of the spectrum, ie. ________.

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100-350nm

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short wavelength UV radiation _______ can cause the strongest bonds in organic molecules to break

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less than 150nm

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weaker bonds in molecules are of more interest to the analyst because they can be excited by longer wavelength UV radiation ________ which is at a longer wavelength than the region in which air and common solvents absorb

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200nm

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chemical substructures that are responsible for the absorption of electromagnetic radiation are called ______.

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chromophores

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a most common ______ in drug molecules is the _______.

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chromophore

aromatic ring, such as the benzene ring

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the _______ by a solution of molecules is governed by the Beer-Lambert Law

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measurement of light absorption

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the beer lambert equation

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A=A(1%,1cm)bc

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since measurements are usually made in a 1cm cell, the equation can be written as ______ which gives the concentration of the analyte in g/100mL

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c= A/A(1%,1cm)

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the ______ a deuterium lamp for the UV region from 190 to 350nm and a quartz halogen or tungsten lamp for the visible region from 350 to 900 nm

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light source

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the ______, used to disperse the light into its constituent wavelengths

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monochromator

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the ______ may be designed to split the light beam so that the beam passes through two sample compartments, and, in such a double beam instrument, a blank solution can then be used in one compartment to correct the reading or spectrum of the sample

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optics

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______ are generated in a high vacuum region, or immediately prior to a sample entering region, or immediately prior to a sample entering a high vacuum region, using a variety of methods for ion production

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charged molecules or molecular fragments

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GC/MS and LC/MS provide highly sensitive and specific methods for determining drugs and their ___________.

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metabolites in biological fluids and tissues

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quadrupole instrument
_______ mass spectrometer than a magnetic sector instrument.

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cheaper and more sensitive

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electrospray ionization
the most common ________

spectra may contain the _____ only

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LC/MC detection interface

molecular ion

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_______ is the most frequently used analysis technique in pharmaceutical analysis

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chromotograph

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if a compound __________, it will travel through the column at the same rate as the solvent

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doesn't partition appreciably into the stationary phase

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the length of time it takes a retained compound to pass throgh the column depends on the compounds _______ which is a measure of the degree to which the compound partitions (adsorbs) into the stationary phase from the mobile phase

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capacity factor (K1)

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calculation of column efficiency
the _____ a chromatographic peak is relative to its retention time, the less efficient the column it is eluting from

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broader

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where n is the number of ______, where tr is the time taken for the compound to pass through the column, where w1/2 is the width of the peak at half its height

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theoretical plates

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_______ is usually expressed in theoretical plates per meter, or n x (100 cm/m)/L

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column efficiency

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silica gel, a _____ column packing, where the mechanism of retaining a compound is by ____ onto the polar groups of the stationary phase

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normal phase

adsorption of the polar groups of a molecule

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octadecylsilane-coated (ODS coated) silica gel, a ______ column packing, where the mechanism of retaining a compound is due to _____ into the stationary phase

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reverse phase

partitioning of the lipophilic portion of a molecule

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HPLC
for neutral compounds it is the balance between its ____ which will determine the time it takes to elute from an HPLC column

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polarity and lipophilicity

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in the case of a reverse-phase column (ODS-coated silica gel), the ____ a compound is the more it will be retained

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more lipophilic

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in the case of a normal phase column (silica gel), the ____ a compound is the more it will be retained

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more polar

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the control of the rate of elution via control of the pH of the mobile phase is only applicable to compounds in which the _____ (the majority of common drugs)

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degree of ionization is dependent on pH

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for the majority of analyses of drugs in formulations, variable wavelength ____ are used which are based on the absorption of UV light by an analyte

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UV detectors

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______ (ELSD) which is based on the scattering of a beam of light by particles of compound remaining after evaporation of the mobile phase

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Evaporative Light Scattering Detector