Analytical Chemistry is one of the 5 Branches of Chemistry. In years before, this is the purpose of many analytical chemist. Analytical chemistry fundamentally is about determining elements of a substance. As time developing, modern analytic chemistry involves more than just determining element that are an identification of an element, elucidation of structure, and quantitative analysis of the composition.
In other definition, analytical chemistry is study about comprising two branches which qualitative and quantitative. Qualitative analysis involves finding what constituent of an analytical example, and quantitative analysis deals with how much a given substance is in the sample.
Qualitative analysis divided into two fields which are in Branches of Inorganic Chemistry and Branches of Organic Chemistry. Analytical chemistry has a lot of method from branch of science to be involved with. For example, chromatography method which found by a chemist, or nuclear magnetic resonance (NMR) and mass spectroscopy which found by physicist. In fact, a result of study published that 60% of paper published about analytical chemistry is made by non analytical chemist.
You may also read:
1. Qualitative Analysis
One of sub branches of analytical chemistry is qualitative analysis. Qualitative analysis is a simple analysis since its field limited to determining whether a compound or element is present or absence in the analyte. In other word, qualitative do not measure quantity. Some of method used to determining the presence of a substance are chemical test and flame test.
Chemical test can be used in biochemical, organic, and inorganic test. This test will verify the requirement of a specification, regulation, or contract are met. It can also become a proof of a concept, demonstrate the utility of proposed patent and other various purposes. This means even a simple test can do many things in analytical chemistry. These test is an early stage of analytics process. These are simple but crucial test which will be very useful things to do before we get into some rigid quantitative test which absorb more energy because of its complexity.
Thus, there are many test in qualitative analysis in chemistry. They are:
- Filtration: The terms have different physical and chemical substances, and basic principle based on particle size.
- Crystallization: With the basic principle that the substance has the ability to evaporate.
- Sublimation: The change of chemicals from solid to gas, by passing the liquid phase advance. Such as distillation.
- Chromatography: The solubility.
- Centrifugation (Twist): The density difference.
2. Quantitative Analysis
Two major steps in analysis are identification and estimation of substances that contain in a compound. Identification step as we have discussed before known as qualitative analysis, while estimation steps can be identified as quantitative analysis. The first step consider more simple then the next step.
Quantitative analysis can be classified based on its method or its analysis scale. Two methods that will be discussed in this article are gravimetic and volumetric. The other method would involves advanced instrument on its experiment or as known as modern method analysis.
At early stage of its development, these modern methods can not produce a reproducible result. This means it can not produce a representative result and free from contamination. These elements of contamination will make the analysis result less accurate. But today, this is no longer problem for chemist as technology getting better and better.
The amount of sample and the amount of relative constituent. if sample are important characteristic in quantitative analysis method. These methods can be classified as macro, semi-micro and micro which depend on the amount of sample. A macro sample has bigger weigh than 0,100 gram; semi-micro range on 0,100-0,010 and micro sample is thus has amount less than 0,010 gram to be precise 0,01-0,001 gram called micro sample. While amount less than 0,001 gram called sub micro or ultra-micro. Substance of sample who has concentration range on 100-1% called first major constituent, while the substance who has concentration range on 1-0,01% called minor constituent. Substance who has concentration below 0,01% called coherent concentration. A determination of coherent concentration by spectrometer needs a macro sample but if we use spectrography method then we only need a micro sample.
There are steps in determining quantitative analysis which start with (1) obtaining sample (2) transform it into a measurable sample (3) determine the constituent observed (4) calculation and interpreting numeric data. Isolation stage is the hardest of all that is the prior stage before calculation, because of its complexicity many methods were developed to overcome this problem.
There are two ways or methods to determine the concentration of a substance. The two methods are gravimetric and volumetric which will be explained as followed.
- Gravimetric Analysis
The principle of this gravimetric analysis is that once an ion’s mass has been determined as a unique compound, that known measurement can then be used to determine the same analyte’s mass in a mixture. As long as the relative quantities of the other constituents are known. The reagent (R) gravimetrically will react with constituent(C) and produce a reaction (CaRb) in solid state and can be weighted. In gravimetric chemistry, reaction and disolvence must be quantitative and the releases must be less than 0,1mg or 0,0001 gram with recovery of its major component around 99,9%.
There are couple of methods in gravimetric analysis such as precipitation method which is used in determination of the amount of calcium in water. In this method, we use the excess of oxalid accid and add it to a known and measurable volume of water. By adding the ammonia as a reagent calcium will precipitate and will transform into calcium oxalate. Because of the positive and negative ion, when a proper reagent is added to an aqueous solution, a reaction will produce highly insoluble precipitates that would be soluble with their counterparts. Direct determination in voltalization method used many inorganic substances to eliminate water in a quantitative amount by utilize the ignition reaction. To determined the mass of the solid desiccant we calculate the gain in mass of the desiccant.
There are other direct voltalization method which is involved the reaction of decomposing carbonates, this reaction will release carbon dioxide when the acids are used.
Carbon dioxide have certain character that is when heat it is easily evolved. By measuring the increase of its mass of the absorbent solid used its mass will directly established. Besides the methods mention above the other method used in gravimetric are electro-analytical and miscellaneous physical method.
A very precise result will be gained if the gravimetric analysis is performed righteously with following certain steps of the methods. Moreover, in determining the atomic masses scientist use gravimetric analysis to six figure accuracy. Besides those precision gravimetric analysis able to result one of its disadvantages is gravimetric can only analyse one element or a limited group of element at a time. So, we have to re-analysis if we want to have a wider range of element as result. This is the lack of gravimetric compare with modern analysis such as chromatography.
- Volumetric Analysis
Volumetric analysis is one of the most useful analytical. It is fairly rapid and has very good accuracy. In a titration the test substance react with a reagent added as a solution of known concentration. This is referred as a standard solution, and it is generally added form a buret. The addition solution is called the titrant. The volume of titrant required to just completely react with the analyte is measured since the concentration is known and since the reaction between the analyte and reagent is known.
The amount of analyte can be calculated. The requirement of a titration are : the reaction should be stoichiometric, the reaction should be rapid, there should be no side reaction, there should be a marked change in some property of the solution, the stoichiometric amount of titration is called equivalence point, the reaction should be quantitative.
There are four general classes of volumetric or titrimetric method they are : Acid-base, many compounds both inorganic and organic are either acid or bases can be titrated with a standard solution of a strong base or strong acid, the end point of this experiment is easy to determine by following the change in pH with a pH meter.
Preciptation, in this case the titrant forms an insoluble product with the analyte, for instance is the titration of chloride ion with silver nitrate solution. The result can be determined by indicators or the potential of the solution can be monitored electrically. Complexometric, in this method the titrant is complexing agent and forms a water-soluble complex with the analyte, the titrant is often a cheating agent. The reverse titration may be carried out also.
Reduction-oxidation, this redox titrations involves titration of an oxidizing agent with a reducing agent, or vice versa. There must be sufficiently large difference between their reduction potential for the reaction completion and give a sharp end point.
Application of Analytical Chemistry
There are two reasons why do analytical chemistry has a really wide application. First, it’s because analytical chemistry offers many usefulness in many discipline like in inorganic chemistry, organic chemistry, physic chemistry, and biochemistry. The second reason is many discipline other than chemistry also use analytical chemistry in their study such as agriculture, medical, solid state, oceanography and others.
One of the application is in clinical chemistry, clinical chemistry is the area of analyzing body fluid to determine clinical pathology in human body. The analytical chemistry help to determine element desired to observed in human blood by using its techniques.
The other application of analytical chemistry is in radioimmunoassay (RIA), radioimmunoassay is new techniques which is finding increased use in the clinical and biomedical fields for specific determination of hormones, drugs, and vitamins at nano gram and smaller levels. The principles of the techniques were developed by Berson and Yalow about two decade ago for the assay of insulin but it was not until late 1960 and early 1970 RIA became widely available for routine analysis.
The other important application of analytical chemistry is in drug analysis for narcotics and dangerous drugs. Drugs can be classified as Barbiturates or as known “downer” for their effect which we could find in sleeping pills; amphetamines is the contrast of barbiturates which have the “uppers” effect; Alkaloids are more commonly found in opium alkaloids which most widely used narcotics and has major addictive effect; Hallucinogens are like amphetamines which has effect as stimulants but they often effect with unpredictable and unusual effect, we can found this kind of element in marijuana.
The Analytical Chemistry Process
Most of analytical process follows logical sequences which start with: defining the problem, obtaining and dissolving sample, performing the required separation, making the appropriate measurement, and the last data presentation. To be more details about these steps, a brief explanation of it will be shown below.
1. Defining The Problem
In this first part, the analyst will ask himself such questions that lead him to acquire problems. The questions could be formed like what is the information required? How sensitive must the method should be? How accurate and precise the analytic will be? What interference are likely and what separations are required? How soon the result must be available? How many sample needed? What equipment needed and required? What is the cost of this performance?
For some analysis, luckily there are already a certain procedure that will help analyst in determining the answers of questions above. For examples, blood chloride is routinely determined by titration with silver ion produced by electro-oxidation of silver metal at controlled current. Once the problem has been defined we could move to next step.
2. Obtaining and Dissolving Sample
Since the sample analyzed should be represent the whole, the method of obtaining it become crucial. Liquid samples tend to be homogeneous which are not often become a serious problem but obtaining sample in solid form or obtaining material element can be a tricky one. The condition when sample collected should be a concern, for example, it is important to know if a patient has already eaten or not when it comes to obtaining blood sample which has biological fluid form, because preservatives such as sodium fluoride could be added to blood sample when they collected under certain condition.
The other concern is the treatment of sample collected, back to our example. If the whole blood is collected an allowed to stand several minutes the soluble protein fibrinogen will be converted by a complex series of chemical reactions into the insoluble protein fibrin.
Moreover, certain precautions should be taken in handling and storing sample to prevent and minimize contamination. In general, one must prevent contamination or alteration of the sample by container, the atmosphere, or the light. These precautions are very important because the contamination could effect a certain reaction which will effect the result of analysis and decrease one analytic accuracy and precise work.
3. Performing Required Separation
If the sample is a solid, it’s usually must be out into solution before the analysis is performed. Biological fluids may be analyzed directly even though in some cases protein that interfered in the biological fluid should be removed.
Various techniques can be used to handle this step. For example, destruction techniques such as acid digestion and dry ashing which will accomplish such removal. Other example is by giving protein-free filtrate (PFF) when a separation procedure is needed.
4. Appropriate Measurement
Method involved for actual quantitative measurement of the analysis is depending on several factors. Not the least important, are the amount of analyze present and the accuracy required. There are many techniques available to use, each of them has it own degree of selectivity, accuracy, precision, and rapidity.
Gravimetric analysis involves the selective separation of the analyse by precipitation, followed by the very non-selective measurement of mass. Volumetric and titrimetric analysis make the analyte reacts with measured volume of reagent of known concentration in process called titration. In electrical property or the absorption of electromagnetic radiation make measurement of physical property as it based.
In modern instrumental method, generally it involved instrument that more sensitive than gravimetric and volumetric method. For example, in gas chromatography which involves a separation based on the interaction of gasses with liquid or solid followed by measurement of separated gasses by non-selective detector. These measurements can be expressed in many ways yet most of them describing the concentration of analyte in the sample represents the bulk material from which it was taken.
5. Data Presentation
The work of analyst ends with his report of data they have been found. The data actually reporting about information required, the method employed, or the method of expressing analytical results. Good laboratory records are important in analytical chemistry. The correct data are used for calculating the mean of result and presenting the precision of the data, is an important way of the validity of analysis to others.
You may also search:
- Branches of Biochemistry
- Branches of Physical Chemistry
- Branches of Inorganic Chemistry
- Branches of Chemistry
As a result, the branches of organic chemistry are important to learn. These fields have many applications to compound whether in industries or medical to fulfill our needs. As a result, may this knowledge useful to know and learn by the time.