analytical chemistry - intro , terminology

What is accuracy ?

is a measure of how close a single measurement from a set is to the true value.

What is precision?

measure the closeness in which repeated analyses of samples agree with each other - How close the results are to each other - if it is Reproducible

What is standard deviation?

a quantitive measure of spread of a set of measurements/results

what is screening used for ?

used to identify individual from a population who are at high risk to allow diagnostic procedures - that may be too expensive/risky to offer to everybody

why use screening tests?

to find out who is at greater risk- they are then offered to people at greater risk

What happens after screening?

Once completed, and a subgroup of the population who is at a greater risk of a disease has been identified, diagnosis is facilitated using a more accurate test or group of tests or procedures.

These diagnostic tests will confirm whether an individual has that disease or not.

Qualitive test

a test which is concerned with only the nature of the substance under investigation and not its amount or concentration. eg. preganancy test,coid test

Quantitive test

est which is concerned with the amount or concentration of the substance(s) under investigation.

what is an analyte?

the substance or component you want to analyse

For example, if an analytical method can distinguish one molecule in a mixture of similar molecules, it is selective for that molecule.

what is selectivity?

a basic analytical property how well a test can ignore everything else in a sample and focus only on the target substance(analyte).

what is specificity

an analytical method that is perfectly selective for an analyte or group of analytes - How well it targets a specific thing . NOTE:very few methods are truly specific

what is Sensitivity?

Analytical sensitivity is a test's ability to detect or measure very small amounts of a substance in a sample. - How well it is able to measure a small difference of a specific thing

Example- the more similar the conc of an analyte or the lower the amount that can be detected ,the higher the sensitivity if the technique

Why is Quality important?

it is an important concept in the standardisation of methods, i.e. ensuring methods work according to a particular defined standard or method.

What is Quality?

quality- the body of characteristics, properties, attributes or abilities that make it better or worse than, or equal to, other entities of the same type.

NOTE- ISO - defines quality as the totality of characteristics of an entity that are able to satisfy the needs imposed by a client

What is Quality Assurance? (QA)

describes the overall measures that an analytical laboratory uses to ensure the quality of its service. - What are they doing to ensure Quality

What is Quality Control? (QC)

It is a component of QA which involves examining the laboratory and its analytical results.- ensure that analytical processes work correctly.

What are the Two Types of QC?

INTERNAL QC-which provides confidence to the laboratory staff carrying out the measurements

EXTERNAL QC- also known as external quality assessment, which provides confidence to the client by comparing the performance of the laboratory with others making similar measurements.

What is GLP?

Good laboratory practice- GLP is a legal requirement for all laboratories doing regulatory work, ensuring the production of quality test data.

What is GMP?

Good Manufacturing Practice - part of QA which ensures products are manufactured to an appropriate quality for their use

What are the Types of errors?

Systematic error

random error

What is a Systematic error? How can they be Reduced?

an error relating to the equipment used or how you used it

NOTE- systematic errors affect the accuracy of the mesurement

Examples:

a burette will be accurate to a certain error (here 0.1 ± 0.1 cm3)

misreading of the value by not using the bottom of the meniscus

Systematic errors can be reduced by

1. using better equipment (not always practical)

2.ensuring equipment is calibrated

3.ensuring equipment is used correctly

What is a random error ? How can it be reduced?

an error caused be unknown or unpredictable environmental changes

Examples:

temperature changes

electrical interference

Random errors can be reduced by:

1.using better equipment (not always practical)

2.controlling the environment around the equipment e.g. temperature controlled housing

3. §repeating the experiment

Describe the Analytical process?

1. define the problem, or hypothesis.

( consider possible experimental procedures)

2. Devise a sampling strategy and collect samples (by asking a set of reserch questions )- to see what is already known etc

3. Once the hypothesis has been tested repeatedly , and experiments show predicted behaviuor then it can be developed into a theory.

4. If theory disproved through furthr analysis then a new theory needs to be developed to replace/ refine the old one

Analytical process - Applied to real life Example - YOUR HUNGRY

1. determine possible options- decide on one

TAKEAWAY,HOME COOKED, RESTURANT ETC..

2. Analyse the option ,

WHERE - make a list , WHAT DO YOU WANT TO EAT

3. You create a sample- LIST OF MENUS , IS IT OPEN , WHAT DO YOU WANT - ...

4. Make a conclusion -did the cheesburger fil you up or are you still hungry

NOTE- if it did the problem is solved if not return back to hypothesis and reoeat process again

What is Sampling ?

sampling is the act of testing a small, representative part (portion)

of something to understand the whole

What Further considerations do you have to make when sampling?

further Considerations:

Bulk samples;

Aliquots (sub-samples);

Handling;

Labelling;

Storage;

Stability;

Sample management

Sample ethics

Study control:

-Blindness

-Population

What do you consider when determining which technique is appropriate for a analytical problem to get optimum results?

Considerations:

-How accurate does the analysis need to be?

-Qualitative or quantitative?

-How much sample is available versus how much sample is needed?

-Does the sample need to be manipulated (extracted, stabilised, etc.) before analysis?

-What is the likely concentration range(s) of the analyte(s)?

-How sensitive is the technique? What is the limit of detection (LOD) and the limit of quantification (LOQ)?

-Destructive vs non-destructive?

Further analytical considerations include:

-Speed

-Skills required of analyst

-Cost of equipment and infrastructure

-Availability of equipment

-Portable or lab-based

-Per-sample cost

-Health and safety

-Format of data

-Statistics (relevance)

-An incorrect interpretation can have a financial, legal, environmental, health or even a political impact.

Summarise the Scientific Method

it is a constant cycle of theory testing , refining allowing analysts to get closer to better explanations ,descriptions of their own area of investigation

How does the Scientific Method work?

1.setting up a hypothesis,

2. testing it, refining or reformulating it,

3. retesting it, and so on, is often called the scientific method.

NOTE-Here we have turned it specifically to analysis.- but underpins all scientific investigations

What is Analytical Chemistry?

it tells us what chemicals are in a sample and/or how much of a chemical is in a sample

MAIN COMPONENTS:

- IDENTITY

- AUTHENTICITY

- PURITY

- CONSISTENCY

How can you IDENTIFY a completely unknown or new compound that you have made?

look at the following :

-Melting point

-Reactivity

-Odour

-Crystal Structure

-Spectroscopy (UV-Vis, IR)

-Taste (not in the lab!)

Why is Determining AUTHENTICITY important?

Determining authenticity is important for:

-Consumer protection

-Protection of intellectual property

-Understanding risk

-Handling safety

How do you confirm authenticity ?

it requires an authentic sample, known as a STANDARD REFERANCE MATERIAL of known provenance for comparison

Why is PURITY important ?

it is important for safety and reproducible science -a small amount of impurities can have significant. health effects

What is CONSISTENCY?

Does one batch of material/product meet the required specification?

Does it meet performance specification?

Does it meet legal/regulatory requirements?

EXAMPLE: PAINT

Performance

-Is it the right viscosity?

-Will it be stable on the shelf in B&Q?

-Will it still dry in the appropriate time?

LEGAL

-Is the concentration of volatile organic compounds (e.g. solvents) low enough to be sold to consumers?

What is the BRITISH PHARMACOPEIA ?

it collection of standards for UK medicinal substances and products.

Ensures the quality, safety, and efficacy of medicines.

Contribution to public health.

What does the british Pharmacopeia include?

It includes:

-active pharmaceutical ingredients,

-excipients,

-formulated preparations (licensed and unlicensed), herbal drugs,

-blood products,

-immunological products,

-radiopharmaceutical preparations,

-homeopathic preparations.