Profile
Settings
Refer your friends
Sign out
Introduction
The measurement of how much a specific component is present in a sample is known as quantitative analysis. The quantity can be expressed in terms of mass, concentration, or relative abundance of any or all of the sample’s components. Quantitative research evaluates nutrient levels and offers an exact accounting of dosage in the manufacture and testing of food and pharmaceuticals.
It is also important for determining the amount of pollutants or impurities in a sample. While qualitative analysis can detect the presence of lead in the paint on a toy, quantitative analysis can detect the amount of concentration present.
Medical tests rely on quantitative analysis for information about a patient’s health. Quantitative analytic techniques can be used to evaluate blood cholesterol levels, lipoprotein ratios in plasma, and the amount of protein discharged in urine.
Quantitative Analysis of :
Phosphorus (P)
Principle: When an organic compound with a known mass is heated with fuming nitric acid, the phosphorus in the chemical is oxidised to phosphoric acid. Combining ammonia and ammonium molybdate forms ammonium phosphomolybdate, (NH4) 3PO4.12MoO3. Phosphoric acid can also be precipitated as MgNH4PO4 by combining a magnesia mixture, producing Mg2P2O7 when ignited.
The ammonium phosphomolybdate precipitates are filtered, washed, dried, and weighed. Alternatively, by adding magnesia mixture, magnesium chloride, ammonium chloride, and ammonia, phosphoric acid can be precipitated as magnesium ammonium phosphate. The magnesium ammonium phosphate precipitates are filtered, washed, dried, and burned. The resulting magnesium pyrophosphates are weighed. The percentage of phosphorus can be estimated using the quantity of the organic component taken and the mass of ammonium phosphomolybdate or magnesium pyrophosphate produced.
Sulphur (S)
Principle: Carius Method- In a Carius tube, a known mass of an organic chemical is heated with sodium peroxide or fuming nitric acid. The compound’s sulphur is oxidised to sulphuric acid. When an excess of barium chloride solution is added to water, it precipitates as barium sulphate, which is filtered, rinsed, dried, and weighed. The mass of barium sulphate can be used to compute the sulphur percentage.
Closed-flask burning (or oxygen-filled flask combustion) with platinum as the catalyst is a simple method for degrading organic compounds in a flask filled with pure oxygen. This approach is appropriate for determining sulphur levels.
Oxygen (O)
The percentage of oxygen in an organic compound is normally calculated by subtracting the overall percentage composition from the sum of all other components’ percentages. However, oxygen can be calculated directly as follows:
A certain mass of the chemical is degraded by heating an organic compound in a stream of nitrogen gas. When all oxygen in a mixture of gaseous products containing oxygen is converted to carbon monoxide, it is passed across red-hot coke. When carbon monoxide is oxidised to carbon dioxide, this mixture is cycled through warm iodine pentoxide (I2O5), producing iodine.
By passing the compound over red hot coke, the oxygen in the molecule is entirely transformed to CO, which is then quantitatively changed to CO2 by passing through an I2O5 solution. The CO2 is then converted to STP, and the volume is calculated. Keeping in mind that one mole of CO2 equals one mole of an oxygen atom from the organic component, each 22.7 litres CO2 equals 16g oxygen (and not 32 g, which would be the usual case).
Carbon (C) and Hydrogen (H)
In one experiment, both carbon and hydrogen can be calculated. In the presence of abundant oxygen and copper(II) oxide, a known mass of an organic compound is burned. The compound’s carbon and hydrogen oxidise to carbon dioxide and water, respectively. The volume of water produced can be calculated by passing the combination through a weighted U-tube carrying anhydrous calcium chloride. Another U-tube with a strong potassium hydroxide solution absorbs carbon dioxide. These tubes are linked together in a sequence. The amount of water and carbon dioxide produced by the increase in calcium chloride and potassium hydroxide is used to compute the percentages of carbon and hydrogen. Water and carbon dioxide (formed from material oxidation) are consumed in anhydrous calcium chloride and potassium hydroxide solutions, respectively, in U tubes.
Conclusion
The field of chemistry concerned with the identification or grouping of components present in a sample is known as qualitative chemical analysis. Depending on the nature of the sample, the procedures used in qualitative analysis vary in complexity. In certain circumstances, the presence of specified elements or groups is required, and specific tests applicable specifically for the sample (e.g., flame tests, spot tests) may be provided. The sample is often a complicated combination, requiring a rigorous investigation to identify all of the ingredients. Each of the constituent elements has its own set of tests.
