Analytical chemistry is primarily concerned with determining the chemical composition of a material. It used to be the ultimate goal of an analytical chemist. But in the field of modern analytical chemistry, its aspects also include the identification of a substance, structural explanation and quantitative analysis of its composition. The difficult task for an analytical chemist is to explain what exactly analytical chemistry is? This is a branch of science where many workers in the field of research have contributed to its development.
For example, chromatographic methods have been invented by biochemists, or biological scientists, while methods such as nuclear magnetic resonance or nuclear magnetic resonance (NMR) and mass spectroscopy, physicists are the first to develop them. Observations of a number of research publications in scientific magazines show that 60% of manuscripts related to analytical chemistry are produced by those who are not actually field scientists. Apparently many scientists who use analytical techniques in the fields of inorganic chemistry, organic chemistry, or biochemistry have objected to calling themselves chemists in the field of analytical chemistry for various reasons.
One of the main reasons for this rejection is the old picture of a chemist who seems to always follow his prescriptions rigidly in his analysis of analytical methods; as is still practiced in the analysis of pharmaceutical ingredients using ISI or BP specifications. The next problem is the widespread application of wet analysis which mainly concerns gravimetric and volumetric methods. The method of analysis performed decades ago was dominated by the classical analysis method. Fortunately with the invention of modern analytical methods that mainly include instruments, the classical methods are beginning to be abandoned.
However, this does not mean that this classical method is eradicated by the development of newer methods of analysis, since the new method has limited scope, ie the new method can not be used if the analyzed substances are present in very large concentrations and other concentrations. Classical analysis methods are still needed to standardize new methods. The false trend is the assumption that the instrumental analysis method only gives meaning to the equipment problem, since the classical analysis method also uses instrumentation such as burette, pipette or balance sheet. What is meant by modern analytical methods is a method that can categorize fast, simple and high sensitivity analysis.
Application of Analytical Chemistry
There are two reasons why analytical chemistry is the only branch of science that has such a wide application. The first analytical chemistry offers a wide range of uses in a variety of chemical disciplines such as inorganic chemistry, organic chemistry, physical chemistry and biochemistry and both are widely used in analytical chemistry in other branches of science such as environmental sciences, agricultural sciences, medical sciences, pharmaceutical chemistry, solid and electronics, oceanography, forensic science and space research.
This will be more clear with regard to one or two examples in each area of research, for example in environmental monitoring air and water pollution is a vital issue. Continuous monitoring of SO2, CO, CO2 can be done by infrared spectroscopy or fluorescence spectroscopy, whereas potentiometry or colorimetry can be used to check the oxygen and chlorine content dissolved in water.
Analysis of pesticides or insecticides on crops with high performance liquid gas chromatography or chromatography, as well as determination of potassium, sodium ratio in fertilizers with atomic absorption spectroscopy or flame emission spectroscopy are some of the use of analytical chemistry in the field. agricultural science. Micronutrient analysis such as iron (Fe), copper (Cu), zinc (Zn), molybden (Mo), boron (B), and manganese (Mn) with spectrophotometer are other examples.
In the field of medical and pharmaceutical research, such as barbiturate analysis, food poisoning, vanadium detection, arsenic in hair and nails by spectroscopy method, cobalt analysis on vitamin B12, iron in blood hemoglobin and isolation using electrophoresis or gel permeation), and others . In the field of electronics, trace element analysis such as germanium in semiconductors and transistors, selenium determination, calcium in photo cells by emission spectroscopy or neutron activation analysis.
In the fields of oceanography, geology and astronomy, analytical chemistry is widely used. Chemical analysis of seawater; Analysis of rocks to determine the quantity of manganese and aluminum or the rapid analysis of moon rock elements by spectroscopy is not impossible. There are many more examples that can not be cited here that show the use of analytical chemistry in various disciplines. All of these examples simply show that the science of analysis is really an interdisciplinary field of research.
Quantitative Analysis Method
The first two steps in the analysis are the identification and estimation of the compound component. The identification step is known as a qualitative analysis whereas the estimation step is a quantitative analysis.
The first step, can be said only temporarily quantitative analysis is somewhat more complicated. Quantitative analysis can be classified based on different analytical methods or classified by scale of analysis. Classification with different analytical scales. The former can divide methods that include classical analysis methods such as gravimetry or volumetry and which include advanced instrumentation, which came to be known as modern methods of analysis.
Initially these newer methods can not guarantee repeatable results. To obtain reproducible results there must be a truly representative sample for analysis and both examples should be free of confounding elements. Eliminating elements can distort quantitative analysis measurement results. Now these two things are not a problem for analytical chemists.
The problem of an analyst dealing with sampling problems and disturbing elements is covered by good sampling knowledge, a fairly complete separation method such as solvent extraction, ion exchange and various chromatographic methods. However, it can be said that such isolation and purification methods are not sufficient. When the number of samples ranges from milligram concentrations, the next step is a method involving volumetry or gravimetry. When components are analyzed at very low concentrations, optical or spectroscopic methods such as UV-visible spectroscopy, IR, with scattering scattering, luminiscence molecules or emission spectroscopy and absorption are used. The methods mainly used for structural explanations include NMR, mass spectroscopy.
Methods of thermal and radiochemical analysis are very useful for quantitative work. Another important method is the electrochemical technique. These methods include potentiometry, volumetry including polarography, conduction and method of cartometometric analysis. Some of the parameters to be discussed below are the appointment of appropriate analytical methods.
Selection of Analysis Methods
From the description of the following methods, the analyst or scientist will deal with the problem of selecting appropriate methods from the various methods available in the quantitative analysis. The choice will be determined by factors such as speed, accuracy, accuracy, sensitivity, selectivity, equipment availability, sample size, level of analysis, this latter factor is a factor that can not be ignored.
In addition to considering the concentration of components to be analyzed, the sample background should also be considered. For example, analysis of iron (III) mineral hematite and contaminated water samples, certainly the analysis can not be done by the same method because we must consider the various disturbing ions. In hematite there is manganese while calcium is in water, so we use choline color with thiocyanate method for hematite ore, while o-fenantrolin is used for water sample by using spectrophotometer.
There is really no good and fast rule for choosing the method. The choice of method is a matter of wisdom. Such wisdom tests are difficult to test and experience usually decisive. It is not appropriate to follow certain methods for elements. Knowledge of basic concepts of chemical analysis is certainly able to equip and develop wisdom and at the same time provide experience and background to be achieved.
In the right selection for analytical methods. This means that an analyst must have extensive knowledge and understanding of the basic concepts of modern analytical methods. He can also use his knowledge to modify existing analytical methods. Next we will review the various steps of the analytical process and analytic determination.
Chemical Analysis and Chemical Analysis
Chemical analysis determines the composition of qualitative and quantitative materials. The constituents to be detected or determined in number are elements, radicals, functional groups, compounds or phases. Analytical chemistry involves a broader and more fundamental aspect, whereas chemical analysis involves more narrower and more specific aspects of analysis.
Careful determination of components in the matrix of several other similar components requires careful regulation of conditions such as pH, complexity, changes in oxidation rates. The advances achieved in analytical chemistry are obtained thanks to the advancement of the method of separation. The analysis generally consists of quantitative analysis and qualitative analysis. Typically qualitative analysis is performed before quantitative analysis. In general, the constituent constituents can be determined precisely by the spectrograph method or spot test / spotting-test with selective, specific and sensitive organic reagents.
Quantitative Analysis and Operation Scale
A large number of samples and number of sample constituents are relatively important for quantitative analysis methods. This method can be classified as macro, semimicro and micro depending on the least number of samples. The macro sample is a sample weighing greater than 0.100 gram, semimicro between 0.12-0.010 grams, whereas less than 0.010 gram is a micro sample.
In general, or rather, samples between 0.01-0.00 grams are called micro samples, whereas less than 0.001 grams is called submicro samples or ultramycro samples. The sample component whose concentration is between 100-1% is known as the main constituent. While the constituent below 0.01% is referred to as the trace concentration. Determination of spectral spectrophotometer concentration requires a macro sample but if done by spectrography, simply by micro samples.
The stages of determining quantitative analysis are for, the effort of obtaining the sample, turning it into a measurable state, the measurement of the desired constituent, the calculation and interpretation of the numerical data.
Content Determination Method
Chemical determination method consists of methods of volumetric and gravimetric analysis. This method is related to chemical reactions. The method based on the measurement of physical properties is known by the method of chemical physics. This method of physical analysis is a method that does not actually include chemical reactions. Most of these physical measurement methods are instrumental methods.
a). Chemical methods: This method includes gravimetric and volumetric analysis methods that are generally based on stoichiometric equations of type:
Untitled Reagent (R) reacts gravimetrically with constituents (C) to produce a dense, weight-balanced reaction product (CaRB). In chemical reaction gravimetry and separation must be quantitative and the losses should be less than 0.1 mg or 0.0001 gram with the acquisition of 99.9% main components. While on volumetry, (R) is added to (C) until CaRb is formed. The end point of the reaction is indicated by the indicator. Often the endpoint is obtained before or after the equivalent point. Various reactions such as neutralization, oxidation reduction, precipitation and formation of complex compounds can be used in volumetric titration. Speed of analysis is very important. Gravimetric and volumetric methods are useful for determining key components. For analysis with large sample quantities, titrimetry is more useful. Overall these two methods, gravimetry and volumetry are still regarded as the right, meticulous, and most practical method.
b). Physical Method: The popularity of physical methods or methods of physics arises from the selectivity and acceleration and simplicity of the analysis phase. This method is useful for the determination of minor components or the concentration of trace elements or constituents that are thought to be the main elements of the sample. Many argue that the accuracy and precision is relatively not as great as chemical methods. This is not always true. When reviewed the speed of its analysis, physical and chemical methods can not be compared. The physics method is very fast and with the same precision. Most of these methods require standards that contain a number of known substances and act as benchmarks in measurement.
Role of Instrumentation
It must be clearly distinguished between instrumentation (as a way of applying analytical techniques) and the intricacies of running the instrument. Instrumentation is very important for analytical chemists. Chemists generally have to understand the fundamental relationship between the chemical type and its chemical and physical characteristics. The analysis should not only know the range and use of the analysis, but the most important thing is to know the limits of measurement in the analysis. During analysis by instrument method, electronic skill is not required by an expert analyst.
Reference : Reference 1, Reference 2, Reference 3, Reference 4
