Determination of the Level of Ethanol in Alcoholic Beverages Produced in Nigeria as an Indication for Safety Standard
This project is a survey of the level of alcohol in beverages produced in Nigeria and to ascertain the compliance of the producers by accepted values on WHO recommendation. Six brands of alcoholic beverages (Guilders, star Harp, Heineken, Stout and Legend) were bought in Awka in Anambra state. The samples were analyzed for level of alcohol (Ethanol) using acid dichromate reaction and visible spectroscopy methods. The result obtained for bottom-fermented beers; Guilders 5.1, star 5.3, Harp 5.2, Heineken 5.1, top-fermented beer Stout 7.2 and Legend6.5 were compared with the European Brewing convention standard of 5.1+0.2 and 7.3+0.2 for the bottom and top-fermented beer respectively. The result showed permissible levels for each of the six samples analyzed which are within acceptable limit except for legend stout with an alcohol content of 6.5 against 7.3+ 0.2 which is the European Brewing convention standard for top-fermented beer. The six samples are within the acceptable limit.
1.1 Background of the Study
An alcoholic beverage is a drink containing ethanol (commonly called alcohol), also called ethyl alcohol, pure alcohol, grain alcohol or drinking alcohol. It is a volatile flammable colourless liquid. It is a powerful psychoactive drug and one of the oldest recreational drugs. It is best known as the type of alcohol found in alcoholic beverages and thermometers. In common usage, it is often referred to simply as alcohol or spirit (Brain and Allan, 2005).
Alcoholic beverages are divided into three general classes, beer, wine and spirits. They are legally consumed in most countries and over 100 countries have laws regulating their production and consumption. In particular, such laws specify the minimum age at which a person may legally buy or drink the minimum age varies between 16 and 25 years, depending upon the country and the type of drink. Most nations set it at 18 years of age. Alcohol beverages are valued on account of their flavour and their stimulating effect and hardly at all as a source of energy; nevertheless, it is worth noting that the energy value of dry wine is about equal to that of milk. The three classes of alcoholic beverages are all made from carbohydrate materials by fermentation and their particular ingredient used and how it is processed chiefly determines the character of the drink. The starting material used depends upon the product required. For example, whisky is made from grain, Rum from molasses, wine from grapes, beer from malt and cider from apples (Morris Jacobs, 2009). The production and consumption of alcohol occur in most cultures of the world, from hunter-gatherer people to nation-states.
1.2 Statement of the Problem
Alcoholic beverages are often an important part of social events in these cultures. In many cultures, drinking plays a significant role in social interaction-mainly because of alcohol’s neurological effects. Alcohol is a psychoactive drug that has a depressant effect. A high blood alcohol content is usually considered to be legal drunkenness because it reduces attention and slows reaction speed. Alcohol can be addictive, and the state of addiction to alcohol is known as alcoholism (Bamforth, 2006).
Alcohol-specifically ethanol (ethyl alcohol, EtOH, CH3CH2OH) is the most socially accepted addictive drug, which can have life-threatening health hazards, its pleasures are very widely acknowledged and form a bond of community for the majority of adults in Western countries. References to those pleasures from a kind of “standing joke” physical and mental discoordination (disorientation are viewed with bemused affection).
1.3 Objectives of the Study
The main objective is to analyze and determine the level of ethanol beverages made in Nigeria.
The specific objective that will achieve the following
- To ascertain the quality of alcoholic beverages produced in Nigeria.
- To identify if there is proper monitoring and quality control
Alcoholic beverages are a standard lubricant (anxiety-reliever) at social gatherings and those who refuse to consume ethanol run the risk of being social outcasts.
1.4 Significance of the Study
Health benefits are frequently claimed for alcohol when consumed in moderation. Most of the claimed benefits are associated with reducing cardiovascular disease. However, alcohol health implication vulmently out weights its health benefit. This project is a survey of the level of alcohol in beverages produced in Nigeria and to ascertain the complaints of the producer by accepted values of EBC/WHO recommendation
1.5 Scope of the Study
The scope of the study includes the sampling and analysis of made Nigeria Alcoholic beverages to determine the level of ethanol using acid dichromate reaction and visible spectroscopy methods.
To compare the results with that of WHO acceptable standard.
1.6 Research Questions
- What are the methods employed in the determination of ethanol in alcoholic beverages?
- What is the effect of alcohol on human health?
- Does make in Nigeria alcoholic beverages meets the internationally acceptable standard.
A drink or beverage is a liquid, which is specifically prepared for human consumption. In addition to filling a basic human need, beverages form part of the culture of human society. In medieval times the term beverage was used to indicate alcoholic drinks. In this century, a variety of drinks have been developed, which are non-alcoholic and the wood beverage is now used to indicate all foods, which are consumed in liquid form (Morris Jacob, 1999). Beverages are liquid foods, which are served as drinks with or without other foods. Even water is included in this group as it is a universal beverage. Beverages help not only to quench thirst but aid the movement of food in the body (John cousins, et al., 2002).
There are a variety of beverages, which are consumed daily. Beverages are served either not or cold. Hot beverages include tea, milk, cocoa, and chocolate and other malt flavoured milk cold beverage include fruit juice, soft drinks, milk etc. Some of these beverages are taken for their stimulating and refreshing effects, while others are taken as stimulating drinks, whole milk, milkshakes etc are nourishing drinks (Morris Jacobs, 1999). Beverages are excellent stimulants or appetizers which play an important role in our daily diet those beverages which are prepared from fruits or vegetables contain vitamins and minerals. And those prepared from meat, milk, egg or legume or cereal or millet provides some protein in addition to vitamins and minerals (Brain and Allan, 2005).
Types of Beverages
There are various classes of beverages the classification is based on whether the beverage contains no alcohol, minimum alcohol, high alcohol content served or consumed hot or cold or soft drinks fruit juice, alcoholic, non-alcoholic and miscellaneous beverages (Bamforth, 2006).
2.1 Alcohol content of Beverages
The concentration of alcohol in a beverage is usually stated as the percentage of alcohol by volume (ABV) or in the United States as proof. In the U.S, the proof is twice the percentage of alcohol by volume at 60 Fahrenheit (15oC) (e.g, 80 Proof = 40% ABV).
Degrees proof were formerly used in the United Kingdom, where 100 degrees proof was equivalent to 57.1% ABV. Ordinary distillation cannot produce alcohol of more than 95.6% ABV (191.2 proof) because at that point alcohol is azeotrope with water. A spirit that contains a very high level of alcohol and does not contain any added flavouring is commonly called a neutral spirit.
Generally, any distilled alcoholic beverage of 170 proof or higher is considered to be a neutral spirit (Bamforth, 2006). Most yeast cannot reproduce when the concentration of alcohol is higher than about 18%, so that is the practical limit for the strength of fermented beverages such as wine, beer and sake. (Arnold, 2005).
Fermentation is the traditional way of making ethanol. Ethanol is made by the action of Enzymes on sugars, particular glucose and fructose, both of which have the formula C6H12O6. One enzyme, which is extremely effective in causing fermentation, is found in yeast. As the grape ripens, the amount of sugar inside them increases and yeast grows on the outer skin. By crushing the grapes the sugary juices and yeast are brought into contact and fermentation starts. The sugar sucrose, C12H22O11, which is itself resistant to attack by zymase, can be broken down into glucose and fructose by another enzyme invertase.
C12H11O12 + H2O C6H12O6 +C6H12O6
Sucrose Glucose Fructose
C6H1206 +H20 Zymase 2C2H5OH + 2CO2
(Philip Mattew, 2003)
The main types of alcoholic drinks and their energy values are shown in table 1 below.
Table 1: The conversion of sugars into ethanol.
|Types of Alcoholic
|Example||Alcoholic content (g/100ml)||Energy value kg/100ml|
Generally, the world alcohol when used alone usually refers to ethanol, also known as grain alcohol or spirit. Ethanol or ethyl alcohol (CH3CH2OH) is the most common member of the organic compound in which a hydroxyl group. Alcohol can be regarded as derivatives of water with an alkyl group replacing one of the hydrogen atoms (Morrison and Boyd, 2005). There are three major groups of alcohol-based upon the number of carbon atoms the C-OH Carbon is bonded to they are as follows:
Primary Alcohol: They has only one alkyl group attached to the carbon atom that carried the hydroxyl groups. The general structure is RCH2OH. The simplest primary alcohol is mentioned and sometimes known as wood spirit because it was initially produced by the destructive distillation of wood.
Secondary Alcohol: This has the alkyl groups attached to the carbon atom that carries the hydroxyl structure R2CHOH. The simplest secondary alcohol is Isopropanol (2-methyl propanol).
Tertiary Alcohol: This has three alkyl groups attached to the carbon atom that carries the hydroxyl group with general structure R3COH that is they contain three alkyl groups but no hydrogen attached to the hydroxyl-bonded carbon atom Example is 2,2-methyl propane-2- ol (John Cousins, et al., 2002).
Alcohol is prepared in the laboratory by hydration of alkenes which engage in an acid catalysed hydration reaction using concentrated sulphuric acid as a catalyst; which usually gives secondary or tertiary alcohol. Also from Gringand’s regent reacts carbonyl groups to give primary, secondary and tertiary alcohols. Hydrolyzing alkyl halides by aqueous alkali gives primary alcohol (Arnold, 2005).
Alcohol is also prepared industrially by fermentation using glucose produced from sugars from the hydrolysis of starch in the presence of yeast.
Denatured Alcohol: This is one of the types of ethanol consisting of ethanol blended with various additives to render it unfit for human consumption. These additives called denaturants are generally either toxic or have unpleasant tasks or odours such as denatonium benzoate, (Morris Jacobs, 1999).
Absolute Ethanol: This is another type of ethanol and it is generally referred to as purified ethanol containing not more than one per cent by simple fractional distillation because a mixture containing about 65.6% alcohol and 4.4% water becomes a constraint in the boiling mixture. In one common industrial method used to obtain absolute alcohol, a small quantity of benzene is added to the rectified spirit and the mixture is then distilled. Absolute alcohol is obtained in the third fraction that distils over at 78.5o. Pure ethanol is a colourless, liquid with a slight but characteristic odour, a boiling point of 75.5oC and a density of 0.78glml. The OH-functional group makes ethanol-soluble in water. (Morrison, & Boyd, 2005).
2.1.1 Alcohol Strength
The scale of measurement of alcohol strength may be summarized as follows:
OIML scale (European): Range 0% to 100% alcohol by volume.
Sikes scale (United Kingdom old scale): Range 0o to 170 proof was the point 100; 70 is equal to 40% alcohol by volume.
American scale (USA): Range 0o to 200o similar to sikes but has a scale of 200o rather than 175o.
2.1.2 The OIML Scale
Previously called the Gay Lussac scale now the organization Metrologic Legale (OIML) scale is directly equal to the percentage of alcohol by volume in the drink at 20oC. It is the universally accepted scale for the measurement of alcohol. The by volume measurement indicates the amount of pure alcohol in a liquid. Thus a liquid measured as 40% alcohol by volume will have 40% of the content as pure alcohol. The alcohol contents of drink by volume is now almost always shown on the label.
Table 2 shows the approximate alcohol strength of drinks (OML) scale (Arnold, 2005).
|% Alcohol by volume|
|Not more than 0.05%||Alcohol-free|
|Not more than 0.05%||De-alcoholised|
|Up to 1.2%||Low alcohol|
|8-15%|| Wines usually around
|14-22%||Fortified wines, Sherry, port|
|37.5-45%||Spirits usually at 40%|
|17-55%||Liqueurs very wide range.|
(Gold Hammer, 2008).
2.1.3 Standard Drinks
A standard drink is a national drink that contains a specified amount of pure alcohol. The standard drink is used in many countries to quantify alcohol intake. It is usually expressed as a measure of beer, wine or spirits. One standard drink always contains the same amount of alcohol regardless of serving or the type of alcoholic beverage. The standard drink varies significantly from country to country. for example, it is 7.62ml (6 grams) of alcohol in Austria, but in Japan, it is 25ml (19.75grams) (Stamper, et al, 2005). In the United Kingdom, there is a system of units of alcohol that serves as a guideline for alcohol consumption. A single unit of alcohol is defined as 10ml. The number of units presented in a typical drink is printed on bottles. The system is intended as an aid to people who are regulating the amount of alcohol they drink (Bamforth, 2006).
2.1.4 Effects of Alcohol on the Body
Alcohol, also called C2H5OH is the most widely consumed drug in the world. Alcohol must be regarded as a foodstuff because in the body it can be broken down to provide energy. When alcohol is ingested, the stomach absorbs only a small intestine, where it is rapidly absorbed by diffusion into the bloodstream which distributes it throughout the body. Alcohol also affects the central nervous system and it is also a drug. These two effects must be considered together when assessing the desirability of alcohol as a source of energy. The nature of the effects of alcohol on the body varies from mild stimulation when a small amount is consumed to loss of coordination and even death when a large quantity is taken (Bamforth, 2006). Consumption of a pint of beer produces a maximum level of about 0.05% alcohol in the blood.
Unlike most foods, alcohol can be absorbed by the body without prior digestion and this takes place mainly in the small intestine, but also through the walls of the stomach. Absorption may take anything from one-half to two half depending on the concentration of alcohol in the beverage consumed the amount taken, and the nature and amount of food eaten with it or immediately beforehand. The average time of absorption is about one hour (Bamforth, 2006) the effect of alcohol in the body is summarized in appendix 2.
After absorption, the alcohol is distributed through the body in the bloodstream and thereafter, it is broken down in a series of oxidative steps with the liberation of energy. The breakdown process is controlled by a series of enzymes, each step being controlled by its enzymes. Initial oxidation of alcohol to acetaldehyde is mainly controlled by alcohol dehydrogenase and as its name indicates, this step involves the removal of hydrogen. It is followed further by oxidation to acetic acid, the most involved in this step being aldehyde dehydrogenase. Those initial breakdown steps occur in the liver, and the acetic acid produced then becomes part of the general body and is further oxidized in a complex process, to carbon dioxide and water. Alcohol is oxidized in the body rather slowly and only about 7g can be oxidized in an hour. This means that alcohol is removed from the body at a slow rate and that it can only make a small overall contribution to energy needs (Curtis Klassen, 1996).
The most common legal terms regarding the effect of alcohol in the body are impairment and intoxication. Those terms are based on blood alcohol content (BAC) which is defined as either gram of alcohol per 2101 of breadth. Even at 100 concentrations, alcohol acts as a central nervous system depression.
Table 3: The effects of various levels of alcohol
|0.01-0.03||Subclinical||Behaviour is normal|
|0.03-0.09||Euphoria||Socially, talkativeness decreased inhibition|
|0.09-0.20||Excitement||Emotional stability, impairment of perception, memory and comprehension, increased reaction time, downiness|
|0.20-0.30||Confusion||Disorientation, dizziness, exaggerated, slurred speech, apathy|
|0.030-0.40||Stupor||Markedly decreased response to stimuli, muscular in-coordination vomiting, sleep|
|0.35-0.45||Coma||Complete unconsciousness impairment of circulation and respiration, subnormal body temperature possible death.|
|0.45+||Death||Death from respiratory arrest|
(Leonidas and Peter, 2006).
2.1.5 Alcohol Intakes and Health
Ethanol and liver
Most ethanol (CH3CH2CH2OH) is metabolized in the crystal of the liver (and to a lesser extent in the kidney, lungs, and other tissues) by the enzyme alcohol dehydrogenase to produce acetaldehyde (CH3CHO), with Nicotinamide Adenine Dinucleotide (NAD) as the hydrogen acceptor. As the third route of ethanol metabolism, catalase in the peroxide (H2O2) is available without requiring NAD as a cofactor. All these methods of metabolizing ethanol result in acetaldehyde (John Potter, 2002).
Acetaldehyde is then further metabolized in mitochondria by the enzyme acetaldehyde dehydrogenase to acetic acid (CH3COOH) which can be metabolized into carbon dioxide and water with a release of energy. Daily drinking can increase the liver metabolism of ethanol by as much as a third but is not rapidly metabolized. High doses of acetaldehyde are so unpleasant that alcoholics have been given acetaldehyde dehydrogenases blocking agent (disulfiram). The alcoholics find the flushing, headache, nausea, vomiting and other side effects to be a strong disincentive for further ethanol ingestion. Large quantities of NADH resulting from heavy drinking can lead to triglyceride accumulation fatty liver, high alcohol and fat consumption along with low protein and carbohydrate consumption helps turn fatty liver into the alcoholic liver cirrhosis-a cause of death for some alcoholics. Protein deficiency increase liver damage due to ethanol fat accumulation in the liver is worsened by reduced lipoprotein biosynthesis and secretion and impaired fatty acid oxidation (John Potter, 2002).
Ethanol potentiates the capacity of Vitamin A to cause liver damage. Ethanol also increases the release of arachidonic acid from cell membranes, increasing oxidative stress. Liver cells degenerate and die, replaced by connective tissue, lymphocytes and leucocytes as inflammation proceeds, only 10-155 of alcoholics develop liver Cirrhosis, however. A higher level of NADH in mitochondria can cause an increase in the number of superoxides (O2) free radicals leaked from oxidative phosphorylation-leading to the formation of hydroxyl radicals (OH-), lipid peroxidation and damage to mitochondria. DNA (Goodman and Gilmans 2008). Acetaldehyde which escapes immediate conversion to acetic acid can blind to the system, a constituent of the anti-oxidant peptide glutathione (GHS), further compromising liver mitochondria function with oxidative damage. Acetaldehyde released into the bloodstream can drift to other organs, notably the brain, where it can damage protein and DNA as well as cause lipid peroxidation in membranes (Cur6tis Klaasser, 1996).
2.1.6 Ethanol and the Brain
It is a common assumption that light drinking can stimulate thinking and that heavier drinking has only temporary harmful effects on brain function. Brain damage to alcoholics is attributed to malnutrition rather than the neutrality of ethanol. Light drinking increase social conversation and reduces inhabitation among virtually all people who consume alcoholic beverages on social occasions. Ethanol exerts its primary effect through modulation of action of several brain neurotransmitters notably subtypes of receptors of glutamate. Ethanol also alters the activity of the brain signalling chemicals serotonin acetylcholine, dopamine, noradrenaline. Ethanol also reduces sodium transport in neurotransmission (Goodmanand Gilman’s, 2008).
As with caffeine, many of the effects of ethanol are through adenosine receptors. Ethanol may inhibit adenosine transports interact directly with adenosine receptors and increase adenosine formation. The latter is a byproduct of ethanol metabolism, caffeine can offset the effects of alcohol when the level of caffeine is high and the level of alcohol is low. The reversal is the best for the sleeping induced effects of alcohol, but co-ordination and performance may not improve as much leaving a wide-awake drunk (Goodman and Gritman’s, 2008).
The second brain neurotransmitter receptor most strongly affected by ethanol is the NMDA (N-methyl-D Aspartate) receptor for glutamine acid (Glutamate), Ethanol, especially in high doses associated with heavy drinking, is a protein inhibitor of the NMDA receptor.
NMDA function in the hippocampus is associated with memory formation through a process known as LTP (Long term potentiating). Ethanol produces a dose-dependent suppression of the magnitude of LTP. In high doses, ethanol can block LTP entirely. LTP blockage is the likely explanation for the fact that after an evening of heavy drinking, 30-40% of males in their late teens or early twenties experience a blackout which eliminates all or part of their memory of what occurred while drinking (John Potter, 2002).
Ethanol is known to produce both tolerance and dependence. Tolerance refers to the fact that an increasingly higher dose of the drug is required to produce the same effect. Dependence refers to the fact that withdrawal of the drug produces unpleasant physiological effects. The unborn foetus is also highly sensitive to brain damage by ethanol in the extreme cases leading to Fetal Alcohol Syndrome (FAS), a condition characterized by facial disfigurement, growth retardation and Brain damage (John Potter, 2002).
2.1.7 Ethanol and cancer
The cancer rate in alcoholics is ten times higher than that in the general population. Epidemiological studies find a much lower incidence of cancer among abstaining religious groups. Every 10gram (10 millilitres-just under one drink) per day of ethanol consumption is associated with a 9% increase in breast cancers (Curtise Klaassens, 1996).
Sixty grams of ethanol per day is associated with a 21% increased risk of prostate cancer. Heavy drinking accounts for nearly 20% of all prostate cancer. (Goodman & Gilman’s, 2008) Both acute and chronic ethanol consumption increases serum estrogen and decreases serum androgen in both men and women.
Many alcoholic men have irreversible atrophy of their testicles. Because excess estrogen and androgen are associated with increased cancer risk, the effect of ethanol on sex hormones explains the increase in breath cancer but the increase in prostate cancer with ethanol must be due to another mechanism (Yulan Lie and Walter Hunt, 2002).
2.1.8 Ethanol and the heart
Modest doses of ethanol beneficially increase plasma HDL cholesterol and reduce blood pressure while harmful raising plasma triglycerides, decides, decreasing heart muscle contractility and increasing heart rate. Heavier drinking increases blood pressure, reduced clothing is another benefit of light ethanol consumption an effect ethanol shares with aspirin. Many studies of cardiovascular disease, have given mixed results. The use of ethanol has been associated with a higher risk of mortality from hypertension hemorrhagic stroke and cardiomyopathy, but with a lower risk from Coronary Artery Disease (CAD), occlusive stroke and no specific cardiovascular diseases. Cardiomyopathy is damaged heart muscles cell unrelated to coronary artery disease. Ethanol with fatty acids to produce fatty acid ethyl ester, (general molecular formula CH3(CH2)n COO CH2CH3) which are toxic to mitochondria-leaving to heart muscles cell damage. (Yuam Liu & Walter Hunt, 2002).
Ethanol impairment of protein synthesis affects both skeletal and heart muscles. In isolated heart cells, ethanol reduces the number and uniformity of fibrils (minute fibres). The heart muscle in alcoholics shows loss of contractile elements and/or fragmentation and disarrangement of those elements (John Potter, 2002).
2.2 Other Effects of Ethanol
Both acute and chronic alcohol consumption can suppress the immune system, leading to increased susceptibility to infections. Decreased antigen Presenting cell function appears to be the most important factor in reduced cell-mediated immunity.
Acute ethanol increases apoptosis (Cell suicide) of both thymocytes and Blood mononucleotides. Although the acute effect of ethanol is transient, it can create a window of opportunity for serious infection by AIDS hepatitis or other pathogens. Alcoholics show increased blood levels of inflammatory cytokines, elevated immunoglobulin and decreased activity of natural killer (NK) cells. (Yeam Liu and Walter Hunt, 2002).
Ethanol stimulates excess levels of plasma cortisol, which can have harmful immunosuppressant and anabolic consequences. Even though alcohol does not reduce average food intake (evidently being a stimulant to the appetite), alcohol does not always lead to weight gain, part of the reason is that alcohol drinkers reduce their consumption of foods as a result of the calories they get from alcohol. But there is also a suppression of oxidation of fatty alcohol that damages the energy-generating system of mitochondria, while at the same time increasing metabolism. A small amount of alcohol can increase (disinhibit) the sex drive of men, while at the same time reducing their capacity to get an erection. The risk of spinal osteoporosis with vertebral fractures is significantly greater among men who drink alcoholic beverages than those who don’t. The risk increase by a factor of 1.007 for each ounce per day for a year of cumulative ethanol exposure. A person under the influence of only one or two drinks may be less capable of dealing effectively with an unexpected life-threatening emergency (Goodman and Gilman’s, 2008).
2.2.1 Oxidation of Ethanol
Under appropriate phase-transfer catalysis conditions, reagents such as dichromate salt in sulfuric acid (acid dichromate) pyridinium chlorochromate in dichloromethane and potassium permanganate can oxidize primary and secondary alcohol in solution. For example, when potassium dichromate is used to oxidize primary alcohol, such as ethanol, the reaction yields the corresponding carboxylic acid. The fate of the dichromate ion in this reaction makes possible the colourimetric determination. The dichromate ion (Cr2O72-) contain Cr(vi), which is yellow-orange, upon reaction with primary alcohol, the Cr(vi) is reduced to Cr(iii), which is blue-green. Cr(iii) concentration can be determined using a visible spectrophotometer. Equation 1 describes the quantitative oxidation of ethanol by dichromate ion.
3CH3CH2OH + 2Cr2O72- + 16H+
3CH3CHOOH + 4Cr3+ + 11H2O
As long as ethanol is the limiting reagent, Cr(vi) will be reduced to Cr(iii) until all the ethanol has been oxidized. As this reaction proceeds, the yellow-orange colour disappears and the solution changes to blue-green (Leonidas and Peter, 2006).
This laterally means measurement of colour the variation of colour of a system with changes in concentration of some components forms the basic form of what the chemist commonly term colourimetric analysis. It is concerned with changes in the colour of a solute colorimetric is the quantitative determination of coloured chemicals or species in solution with the aid of a photoelectric instrument such as Absorption or spectrophotometer operating in the visible region of the electromagnetic spectrum.
The colourimeter is a computer interfaced probe designed to determine the concentration of a solution from its colour intensity. The colour of a solution may be inherent or derived by adding another reagent to it.
Lambert’s law- say that the fraction of incident light absorbed is independent of the intensity of the source and is proportional to the thickness of the absorbing layer.
Beer’s law: This states that the fraction of light is absorbed is directly proportional to the concentration of the absorbing particles.
From these two laws, the Beer-Lamberts law is obtained.
These two laws have been combined mathematically as where;
10 = Intensity of an incident beam of monochromatic
I = Intensity of the emergent beam which has passed through an absorbing medium of thickness 1 cm.
L = Path Length (usually 1 cm)
C = Concentration is mold litre
E = Molar extinction co-efficient or molar absorptive expressed in 1000cm3/mole
A = Absorbance or optical density
The equation id Beer-Lambert’s law and it obeyed by moist solution provided they are dilute
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