Wet Test (Wet Chemistry)
Wet test is a form of analytical chemistry that uses classical laboratory analytical methods such as titrations, extractions, thin layer chromatography (TLC), observing colorimetric reactions and changes of physical state. It is referred to as wet test because most analyzing is done in liquid phase. Wet test can also be referred to as bench chemistry or wet chemistry.
Wet test uses reagents to indicate presence of a specific chemical in an unknown solution. The reagents cause a unique reaction based on the chemical it reacts, allowing an analyzer to understand the chemical present in solution. Examples of wet test include Heller’s test, Ascorbic acid test, protein test, PH test, cloud point, concentration and so on.
Wet test employs the use of laboratory glassware such as beaker, conical flasks and other transparent materials to keep tract of reaction. Also Bunsen burners, gasoline and crucibles may be used to evaporate and isolate substances in their dry forms.
Unlike dry tests (dry chemistry) where qualitative methods are used to determine the presence or absence of a particular chemical compound in a sample, in wet test (wet chemistry), quantitative methods are used to determine the quantity of analyte present by measuring absorbance/transmittance of a solution at a particular wavelength, the weight of a precipitate formed, weight-loss through volatilization, or quantity of titrant required to reach a particular PH value or intensity of color/turbidity.
Wet tests methods use information that can be quantified or measured to indicate a change such as change in concentration, volume, weight and so on. Techniques used in wet chemistry include:
- Limit test- determination that if present an analyte does not exceed a specific level. It is done by comparing the intensity of the color/turbidity of a known solution or the size or color of a standard spot on a TLC plate, to that of the sample.
- Titrimetry- determination of analyte present in a sample by employing a chemical reaction between a titrant of known attributes and the sample.
- Gravimetry-determination of the quantity of an analyte present in a sample by employing a reaction which results in the physical precipitation or volatilization of the analyte.
- Colorimetry- determination of the quantity of an analyte present in a solution by measuring the absorbance or transmittance of UV/Visible light at a specific wavelength versus that of a solution of the analyte of known concentration.
- Polarimetry- determination of purity of a compound by measuring the extent to which a solution bends visible light.
- Physicochemical testing- the determination of physical and chemical properties of a substance.
Applications of Wet Chemistry
- Elemental analysis of samples such as water sources for elements and compounds such as ammonia nitrogen, cyanide, sulfide, phosphorus, phenols, silica, chromium etc.
- Use in agriculture during Soil testing.
- Clinical chemistry uses chemical processes (wet tests) to measure levels of chemical components in body fluids and tissues.
Dry Test (Dry Chemistry)
Dry test in chemistry refers to an investigation that deals with the identification of elements or group of elements present in a sample. It typically analyses changes in color, melting points, odor, reactivity and boiling point. Dry tests are usually specific depending on the sample under investigation for example flame tests or spot test can be used.
Dry test is performed to detect the presence of element in compound by introducing the sample to the flame for the purpose of noting color produced because majority of elements can be detected by means of their characteristic color when heated on flames without using water.
Dry test utilizes simple analytical instruments such as lab scales, PH meters, automatic titrators, microscopes and UV/ visible spectrophometers are used to investigate a substance before and after color changes.