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Assaying caffeine in over-the-counter tablets

Metrohm (UK)contact supplier

844 UV/vis

Caffeine is the most widely used drug in the world, it is a physically addictive stimulant that is naturally produced in the leaves, seeds and fruits of many plants

Commonly found in coffee, tea, soft drinks, chocolate and a wide variety of over the counter medications, caffeine is legal and easily accessible.

Caffeine is the most widely used psychoactive medication in the world.

Chromatography can be used to assay caffeine in a variety of products but especially over the counter pharmaceutical tablets where their control and tolerance is strictly monitored by the regulatory authorities to ensure no risk is posed to humans.

People have enjoyed caffeine beverages for thousands of years.

The earliest record of caffeine consumption dates back to around 2700BC when the Chinese emperor drank hot brewed tea.

Coffee originated in Africa around 575AD and it is thought that in the 11th century Arabs drank coffee regularly.

The Spanish conquistadors exploring Mexico were served coffee in the 16th century.

Americans made a nationwide switch from tea to coffee in the 18th century, as the caffeinated drink of choice as a protest from the heavy taxes laid on the tea imported.

Eventually the Boston Tea Party was held, in which revolutionaries dumped a large quantity of tea cargo from a boat into the Boston Harbor in protest at the high tax placed on tea.

In 1958, caffeine was acknowledged by the American Food and Drug Administration (FDA) as being generally recognised as safe.

Although tea leaves generally contain more caffeine by weight than coffee beans, there is usually more caffeine in a cup of coffee than in a cup of tea because more coffee beans than tea leaves are used to make each regular cup.

Also tea is infused not boiled like coffee.

Worldwide per capita caffeine consumption is estimated to be 70mg per day, or approximately equivalent to one cup of coffee.

The average intake for Americans is believed to be about 200mg per day.

Caffeine moves through the body within a few hours after it is consumed.

It is not stored in the body, but one may feel its effects for up to six hours.

Caffeine can pose risks for certain groups.

Caffeine has pharmacological actions on brain activity, caffeine is consumed regularly by millions in order to induce wakefulness when arising from sleep or to prevent falling asleep, relieve the boredom of daily routines, and decrease the fatigue associated with tedious, long periods of work (eg studying for exams or long distance driving).

It should be remembered that caffeine only masks the sense of fatigue; it does not replenish energy that has been exhausted through physical and mental work.

Caffeine can be used to treat headaches.

Caffeine alone (100-200mg) and in combination with over the counter analgesics, such as aspirin and ibuprofen, has been found to be effective in relieving mild to moderate tension and vascular headaches.

Some over the counter analgesics and cold medicines include caffeine as an ingredient.

Recent studies have suggested that the presence of caffeine might give some therapeutic advantage to these products because moderate doses also appear to have an analgesic effect for certain types of pain.

Caffeine (100-250mg) is contained in all over the counter medicines promoted as stimulants or 'stay awake' products.

There has been a great deal of media interest in the range of energy drinks recently introduced into the market which contain caffeine.

In general, the concentration of caffeine per ml in soft drinks or energy drinks is considerably lower than in coffee.

Most researchers now seem to agree that there is little risk of harm when a person consumes less than 600mg of caffeine a day.

However at times of anxiety or stress, or during pregnancy, many doctors now recommend consumption of less than 200 mg a day.

The short-term effects of using caffeine may include increased body temperature, increased urination, increased alertness and irritability and restlessness.

It should be noted also that the use of coffee to sober a person up after drinking alcohol is not effective.

The caffeine does not improve impaired motor coordination but may make the person more alert.

It simply makes the person under the influence of alcohol more awake.

The long-term effects of caffeine with substantial daily doses - and in some people even as little as 250mg per day - can lead to unpleasant effects such as restlessness, nervousness, insomnia, stomach upsets and muscle twitching.

Fortunately fatal overdose with caffeine are extremely rare though possible and the lethal dose in humans appears to be of the order 5 to 10 grams, although toxic symptoms may appear with lower doses.

Some symptoms of caffeine poisoning include tremors (involuntary shaking), nausea, vomiting, irregular or rapid heart rate and confusion.

The affects of caffeine on pregnancy are not fully explained and appear to be inconclusive with some reports suggesting caffeine increases the risk of birth defects, can interfere with fertility or take longer to conceive.

It is known however that caffeine consumed by the mother does cross through the placenta into the fetus.

Consumption of caffeine has also been linked to an increased frequency and severity of premenstrual syndrome (PMS).

This interaction is dose dependent with the PMS incidence increasing by as much as 5 times for those women consuming 8 to 10 cups of coffee daily.

The source of the caffeine consumed does not appear to make a difference.

Metrohm has launched a new version of the 844 UV/vis compact ion chromatography (IC) in stainless steel complete with a column oven (2.844.0130) especially suited as an alternative low cost and simplified way of assaying many pharmaceutical or food/beverage based products using photometric detection.

One such application is the analysis of caffeine in over the counter tablets that can be performed isocratically simply using a phosphate/methanol mobile phase.

The 844 UV/vis compact IC with column heater is a complete liquid chromatography system with a very small footprint.

Together with a suitable separation column the instrument analyses substances (polar, anions or cations) absorbing ultraviolet and visible light.

The stainless-steel version of the 844 UV/vis compact IC with column heater guarantees excellent flow accuracy as well as precise and reliable results.

All the hardware is located inside a single housing and all components are easily accessible.

Included with the system are a high-pressure pump with stainless steel pump head, a six-port injection valve equipped with 20ul sample loop, a column oven and a diode array detector (DAD) with a combined bulb system for the UV and Vis lamp.

All components of the chromatography system are made of stainless steel.

Additionally the 844 UV/vis compact IC with column heater is equipped with a gas sensor and a leak detector for liquids.

The gas sensor detects very low amounts of evaporated organic solvents (used often in the mobile phase) within the instrument and stops the system immediately.

This means increased safety during operation.

The DAD can measure three different wavelengths and a reference channel in parallel.

Additionally the ratio of absorption signal 1 and absorption signal 2 is recorded.

Absorption spectra can be determined for optimization of an application during development of a method.

Analysis of tablets was relatively simple; one tablet was solved in a know quantity of ultra pure water and run against a previously run caffeine calibration curve with caffeine detected on the ProntoSil C18 column in less than six minutes at a wavelength of 280nm using the IC Net controlling software.

As an option then MagIC Net can also be used for manipulation of the results (IC Net is used only to start-up the hardware); operation of the instrument is performed from MagIC Net in terms of running samples, calibration of standards and all the chromatographic raw data goes into the MagIC Net database where the determinations can be reported or exported either manually or automatically into an external package.

Shutdown of the IC hardware can also be performed from directly from MagIC Net.

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Analysis & Quality Control