Analytical Chemistry Methods

• Analytical chemistry involves quantitative analysis stages.

Classification of Analytical Methods

• Gravimetry uses direct methods by measuring the weight of the compound containing the species of interest.
• Gravimetry uses indirect methods by measuring weight loss due to volatilization of a species.
• Volumetric methods involve titration, which measures the volume of solution that is chemically equivalent to the species sought.
• Gas analysis measures the volume of gaseous species produced or consumed.
• Emission spectroscopy measures radiation emitted by a species.
• Absorption spectroscopy measures radiation absorbed by a species.
• Polarimetry measures when polarized light rotates due to a species.
• Refractometry measures the refractive index of a solution of a species.
• Turbidimetry measures light dispersion by a potential species.
• Potentiometry measures the potential of an electrode in equilibrium with a species.
• Conductimetry measures the conductivity of a solution of a species.
• Coulometry quantity of electricity equivalent to a species.
• Polarography measures current associated with a reaction at a polarizable electrode.
• High-frequency methods measure the capacitance of a solution of a species.
• Mass spectroscopy measures the mass-to-charge ratio of decomposition products of a species.
• Radiochemical methods measure radioactive disintegration of a species.
• Thermal conductivity measures the thermal conductivity of a species.
• Enthalpimetric titrations measure species reaction heat.

Steps of Quantitative Analysis

• The sample should reflect the composition of the total material from which it was taken to give significant results.
• Sample preparation involves converting the sample into a suitable form for analysis, such as trituration.
• The method is selected based on the physical and chemical properties of the sample.
• The method used has to justify the features and properties present in the sample.
• The interference removal process involves removing components with similar behavior to species of interest to prevent errors in the analysis.

Sampling Plan

• The most important operations in sampling and sample treatment involve creating sample plans, different types of samples, number of samples, sample dimensions , and more.
• A sampling plan includes procedures to select, extract, conserve, transport, and prepare sample portions to separate from a population.
• A sampling process should be planned, detailed, and written which includes where the sample will be taken, who will take the sample, and the procedure taken.

Sampling Plan Requirements

• Includes information on the nature and matrix of the sample
• Also includes information on the instrumentation to use during sampling.
• The homogeneity degree of the sample should be known
• The number of subsamples is indicated to ensure determined accuracy.
• Precautions should be presented to follow in sample preparation

Types of Sampling

• Representative: composition and qualities are similar in a sample and the whole.
• Selective: sample is obtained from certain zones.
• Systematic: sample is obtained according to a systematic procedure.
• Random: sample is obtained at random.
• Composite: sample is formed by two or more subsamples

Sampling Types

• Intuitive sampling relies on experience in a particular type of sample.
• Statistical sampling uses a statistically validated model.
• Systematic sampling follows a protocol specifying the type, size, frequency, period, sampling location, etc.
• Sample collection is fundamental for solids, liquids, and gases.
• Method selection is the first step in any quantitative analysis.
• When choosing the ideal process, the level of accuracy is important.
• If processing many samples, time will be spent assembling/calibrating instruments and preparing standard solutions.
• When analyzing few samples, select a method which avoids or minimizes preliminary steps.

International Sampling Regulations

• ASTM regulates standards, and clients can request product testing adheres to these guidelines, in order to give valid results.
• A sample should be representative in composition of its source material.
• Sampling means obtaining a small material quantity composing mass for the material undergoing sampling.
• For Example gases in blood concentration determined by different physiological and environmental factors.
• Standard lab procedures for sampling and transporting enable a representative blood sample.
• Sampling is the most difficult analysis step so the final result will never be more reliable than the sampling stage.
• Sample processing, the third analysis stage, may not be required for direct measurement.

Preparing a Lab Sample

• Pulverizing a solid lab is the first step to reduce particle size, ensure uniformity and stock it for some time before the test.
• Water absorption or desorption can occur during each process stage, depending on the ambient humidity.
• Drying samples before analyzing or determining the moisture content while analyzing is advisable due to altered chemical composition.
• Liquid samples can present distinct challenges, where the solvent can evaporate, altering the solution concentration.
• If there is a gas dissolved, the receptor has to persist in a sealed secondary recipient so it doesn't pollute everything.
• Measuring repeatedly improves result quality and provides a measure of reliability.
• Repeated quantitative tests are calculated, and many statistical methods determine accuracy.

Sample Solutions

• Samples are usually analyzed in the solutions which is prepared with the correct amount of dissolvent.
• The solvent should dissolve, including the measurement quickly and completely, since the materials will be un-dissolvable.
• Transforming an insoluble calculation is always the most difficult step in analytics.
• The sample should be placed with strong acids with high temperatures.
• The sample should be either calcined indoors or melted.
• If the solution has any properties, it should be able to measure properly.

Interferences

• Interference refers to species hindering final measurement.
• They can be removed through filtering, discarding, and other methods.
• Since some properties are exclusive, there's a high chance of reactions being used.
• Analytical result is determined by the final measured feature, which should change predictively and repeatably with concentration.
• Under Ideal cases, the measured property is directly proportional to concentration following the formula ca= kx.
• Calculations rely on measurement-stage experimental data, measurement instrument properties, and analytical reaction stoichiometry.
• The analyst must provide a measure of randomness associated with calculation results and is dependent on the analyzed data.
• An analytical result lacking reliability lacks value.

Steps in a Chemical Analysis

• Sampling: Selecting a representative sample of the material.
• Conversion: Convert the analyte into a suitable form for measurement
• Measurement.
• Calculation and measurement interpretation.

Exploration of quantitative analysis in analytical chemistry. Overview of gravimetry (direct and indirect methods), volumetric methods using titration and gas analysis. Examination of spectroscopy, polarimetry, refractometry, turbidimetry, potentiometry and conductimetry techniques.