Chemistry Flashcards by Lydia Su

Examples of adsorption chromatography?

How does it work?

Thin layer, silica column

Solute is adsorbed onto the surface of the stationary phase

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What’s partition chromatography consist of?

How does it work?

A thin liquid (oily) stationary phase coated on the surface of a solid support (silica)
Solute dissolved in liquid stationary phase, equilibriate bw 2 phases

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What’s ion exchange chromatography consist of?

A resin: anionic or cationic groups covalently attached to a stationary solid phase. And a liquid mobile phase.

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In Ion exchange C, how does solute ions attach onto the solid stationary phase?r

By electrostatic Forces between solute ions and charged ions In resin

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What’s adsorption chromatography consist of?

A solid stationary phase

Liquid or gaseous mobile phase

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What is the British pharmacopoeia?

It is the legal standard of quality for pharmaceuticals and contains specifications for all substances used in the manufacture of medicines. CERY CHEAP techniques that can be used anywhere

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What does a pharmacopoeia like monograph tell you?

1) describes the substance
2) specifies a required level of purity
3) describes tests to identify the substance
4) decried test to monitor possible impurities
5) specifies an assay to determine the amount of the substance

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What’s the qualitative analysis?

IDENTIFY the substance (and/or monitor and identify possible impurities)

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What’s quantitative analysis?

To accurately determine the amount of a substance (could also be the amount of activity)

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What’s the quantitative analysis based on?

It is based on finding the linear relationship between the amount of a substance and the measurable chemical, physicals, biological property of that substance

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What is the British pharmacopoeia?

It is the legal standard of quality for pharmaceuticals and contains specifications for all substances used in the manufacture of medicines. CERY CHEAP techniques that can be used anywhere

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What does a pharmacopoeia like monograph tell you?

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What’s the qualitative analysis?

IDENTIFY the substance (and/or monitor and identify possible impurities)

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What’s quantitative analysis?

To accurately determine the amount of a substance (could also be the amount of activity)

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What’s the quantitative analysis based on?

It is based on finding the linear relationship between the amount of a substance and the measurable chemical, physicals, biological property of that substance

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Is volumetric analysis (titration) a Quantitated method or a qualitative method?
How often is it used in the BP
Example?

Quantitative method

Used for about 80% of the substances in the BP

Acid and base and redox titrations

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Is spectrophotometric method quantitative or qualitative?
Example of method?
How does it work?

IR Qualitative (provides fingerprint and is used in many monographs as an identification technique: identify substance/ impurities)

UV quantitative and qualitative (is widely used as a quantitative method: determine the amount of substance)

Infrared spectroscopy and UV spectroscopy, the amount of absorption by functional group is measured.
Utilise the interaction of substances with EM radiation.
Are mainly used for pure substances

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Describe the chromatographic methods?

Separate mixtures of substances by virtue (through the power of) of their differing affinities for a stationary phase and a mobile phase

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TLC can be used as qualitative or quantitative method?

What is its use?

Mainly qualitative - used by BP to monitor/identify impurities

Semi quantitative - use of diluted sample in limit tests for impurities (identify and control the impurities)

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Is HPLC qualitative or quantitative method

And whats the most suitable substance used?

Both

Most suitable for pure substances soluble in mixtures of water and polar organic solvents

Internal standard is used to avoid experimental errors

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Is GLC quantitative or qualitative?

What substance is most suitable for this one?

Both

Relative volatile and heat stable organic compounds

Use internal standards

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What are the validation of quantitative analyses? (From BP)

Study These Flashcards

SLA PLL
Selectivity
Linear of response
Accuracy

Precision
Limit of detection
Limit of determination

Accuracy of the quantitative method can be affected by?

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Impurities in preparation
Manipulation of sample during analysis
Complexity of overall analysis

IMC

What’s recovery in term of accuracy?

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A rough measure of accuracy is provided by calculating the recovery

%recovery =sample slope/ standard slope x100

What's limit of detection?

The measure of the absolute lower limit of analyte the method can detect

What's limit of determination?

The measure of the lowest limit of analyte CONCENTRATION that the method is able to QUANTIFY with a know degree of precision

Precision splits into 2 categories:

Repeatability- multiple analyses of the same sample by the same person using the same equipment over a short period of time Calculate mean, SD, relative SD Reproducibility- different

What are non-aqueous titrations?

Titration of substances dissolved in solvents instead of water as water is amphoteric (can both accept and donate protons in a reaction that competes with the analyte)

What's the NA titrants for weak acid and weak base?

NAT for weak acid: lithium methoxide (CH3OLi) in methanol NAT for weak base: perchloric acid (ClO3OH) in acetic acid

Describe the procedures in a titration

1) weight out a PRIMARY STANDARD. -to make up standard solution with known concentration 2) STANDARDISE the titrant -find titrant conc 3) weight out SAMPLE 4) titrate sample with titrant to END POINT 5) calculate the amount of sample from moles (Eq) and RMM of reactants

What are primary standards? | Examples?

Solids that have a very high purity

Define secondary standards

Are reagents that have been standardised again a primary standard

Describe what's a blank titration

Laboratory glasswear reacts with the titrant (NaOH) and consumes some of it. In method where glasswear is in contact with these titrant over a long period, a separate experiment (blank titration) has to be carried out to measure the amount consumed.

Describe a back titration

Or indirect titration. Is used when reaction is slow or requires an excess of reactant B or heat. Reactant A of unknown concentration is titrated against reactant B (in XS) of known concentration. The amount of B that's consumed is determined by measuring the amount that's left over by titration with a standardised acid/ base

Why do we need to standardise titrant?

We don't know EXACT concentration of the titrant we start with, even though the amount have been accurately weighed. This is because IMPURITY and REACTION WITH THE SURROUNDING (NaOH + air)

How to calculate the max no of fundamental vibrations of a molecule in IR

3n -6 | n=the no of atoms in mol

Why is KBr plates/ NaCl prism is used in IR?

Ionic binding- so invisible to IR

What does IR Spectrometry associate with in term of molecule

It involves the vibration of chemical bonds WITHIN the molecule

What's K stands for in IR

The force constant, measure of stiffness of bonds

Compare the size of K for stretch and bend

K stretch> K bend

K stench is higher or lower in triple bond

Higher

What information you can obtain from mass spectrum?

Molecular weight Accurate mass Isotope peaks Fragmentation

Does EIMS always give MI? | What's the solution

No around 20% of compounds give no MI- only fragments Or give small MI We use low EV ms

What's the precision of Morden MS m/z value

0.0001 (4dp)

What are the ionisation methods in LC-MS?

Thermospray- give pseudo and some frag | Electrospray ESI- mainly pseudo

An example of partition chrom?

Reverse phase HPLC

Ion exchange- Name one method where you can change the charge expressed by the solute and aid separation process?

Changing the PH of the mobile phase

Example of ion exchange?

Ion exchange purification of protein and biological molecules or sugar like molecules

Explain the method of molecular exclusion chrom?

Separate molecules by size, with larger mol passing straight through the column most quickly. Whereas the small molecules enter the pores on stationary phase. No interaction between stationary phase and solute

Describe the affinity chrom? Is it selective? What is it used for?

Most selective chrom Based on sopecific interaction bw one kind of solute molecule (a protein) and another molecule that is convalently bond to stationary phase (antibody). Used to isolate one protein from a mixture, protein purification. Dislodge by changing pH

What method can separate optical isomers? d- L- | What are the ad and disad

HPLC, Ad- separate optical isomers in small scale for analysis. Disad- not suitable for scale of commercial use Better to develop CHIRAL SPECIFIC SYNTHESIS as it is VERY expensive

What is a chromophore?

A part of molecule that's responsible for absorption of uv or invisible region of spectrum.

What is an auxochrome?

A functional group that has no absorption on its own but can modify the absorption of chromophore

Chemistry Flashcards

(53 cards)