100+ QC Chemist Interview Questions and Answers

The principles of HPLC, GC, UV, and IR are the fundamental concepts that govern the operation of these analytical techniques.

• HPLC (High-Performance Liquid Chromatography) separates components of a mixture based on their interactions with a stationary phase and a mobile phase.

• GC (Gas Chromatography) separates components of a mixture based on their boiling points and interactions with a stationary phase and a mobile phase.

• UV (Ultraviolet) spectroscopy measures the absorption of...read more

Ranges in NMR and UV can be identified by analyzing the chemical shifts and absorption peaks, respectively.

• In NMR, chemical shifts are measured in parts per million (ppm) and can range from 0 to 12 ppm for proton NMR.

• In UV spectroscopy, absorption peaks are observed at specific wavelengths, typically ranging from 200 to 400 nm.

• Interpreting the peaks and shifts in the spectra can help determine the functional groups present in the compound.

The Grignard reaction involves the addition of an organomagnesium halide to a carbonyl group.

• The reaction is named after French chemist Victor Grignard.

• It is used to form carbon-carbon bonds and is a key reaction in organic synthesis.

• An example is the synthesis of triphenylmethanol from benzophenone and phenylmagnesium bromide.

• The reaction proceeds through the formation of a Grignard reagent, which then attacks the carbonyl group.

• The resulting intermediate then undergoes hydr...read more

The HPLC should be calibrated before each use to ensure accurate and reliable results.

• HPLC should be calibrated before each use to maintain accuracy

• Calibration frequency may vary depending on the lab's SOPs and manufacturer recommendations

• Regular calibration helps in ensuring reliable results and instrument performance

• Calibration intervals can range from daily to monthly, depending on usage and requirements

Chemistry is the scientific study of matter and its properties, composition, and behavior. QC stands for Quality Control. HPLC and GC are analytical techniques used in chemistry.

• Chemistry is the study of matter and its properties

• QC stands for Quality Control and is used to ensure that products meet certain standards

• HPLC (High Performance Liquid Chromatography) is a technique used to separate, identify, and quantify components in a mixture

• GC (Gas Chromatography) is a technique...read more

To make 0.1 N NaOH, dissolve 4g of NaOH in 1L of distilled water.

• Calculate the molecular weight of NaOH (40g/mol)

• Weigh 4g of NaOH and dissolve it in distilled water

• Make up the volume to 1L with distilled water

• Stir the solution until the NaOH is completely dissolved

• Verify the concentration using a standard acid solution

Settle plate method is a technique used to measure the microbial contamination in the air of a cleanroom.

• In this method, a sterile agar plate is exposed to the air for a specific period of time.

• After the exposure time, the plate is incubated to allow any viable microorganisms to grow.

• The number of colonies on the plate is then counted and used to determine the level of contamination in the air.

• This method is commonly used in pharmaceutical and biotech industries to monitor th...read more

Organic compounds are composed of carbon atoms bonded together in various arrangements, with different functional groups determining their properties.

• Organic compounds contain carbon atoms bonded together in various structures

• Functional groups such as alcohols, aldehydes, ketones, and carboxylic acids determine the properties of organic compounds

• Mechanisms in organic chemistry involve the breaking and forming of chemical bonds to create new compounds

• Examples include the mecha...read more

Different types of titration include acid-base, redox, complexometric, and precipitation titrations.

• Acid-base titration involves the neutralization of an acid with a base or vice versa.

• Redox titration involves the transfer of electrons between reactants.

• Complexometric titration involves the formation of a complex between the analyte and titrant.

• Precipitation titration involves the formation of a precipitate as the endpoint of the titration.

• Other types include iodometric, coul...read more

Yes, I have operated HPLC before in previous roles.

• Operated HPLC to analyze samples and generate data

• Performed routine maintenance and troubleshooting on HPLC equipment

• Interpreted chromatograms and reported results accurately

A pH meter is an electronic device used to measure the acidity or alkalinity of a solution.

• pH meter measures the concentration of hydrogen ions in a solution

• The range of a pH meter is typically from 0 to 14

• A pH of 7 is considered neutral, below 7 is acidic, and above 7 is alkaline

• pH meters are commonly used in chemistry, biology, and environmental science

The question is incomplete and cannot be answered without additional information.

• The question needs to specify what c-9 refers to.

• Density is typically measured in units of mass per volume.

• The density of a substance can vary depending on temperature and pressure.

• Additional information is needed to calculate the density of c-9.

FTIR is used to determine the functional groups present in the API.

• FTIR measures the absorption of infrared radiation by the sample

• Different functional groups absorb at different wavelengths

• The resulting spectrum can be used to identify the API and its purity

• Examples of functional groups include carbonyl, hydroxyl, and amine groups

The process of mixing spatches involves several steps to ensure uniform distribution of ingredients.

• The first step is to accurately measure the required amounts of each ingredient.

• Next, the ingredients are mixed together using a suitable mixing equipment such as a blender or mixer.

• The mixture is then homogenized to ensure uniform distribution of the ingredients.

• Finally, the mixed spatches are tested for quality and consistency before being used in production.

• Example: Mixing s...read more

Natural indicators are substances that change color in response to changes in pH levels.

• They are derived from natural sources such as plants, fruits, and vegetables.

• Examples include red cabbage, turmeric, and beetroot.

• They are used in various applications such as in food, cosmetics, and medicine.

• They are eco-friendly and non-toxic compared to synthetic indicators.

To make standard HCl solution, dilute concentrated HCl with distilled water to the desired concentration.

• Calculate the amount of concentrated HCl needed based on the desired concentration and volume of the final solution.

• Add the calculated amount of concentrated HCl to a volumetric flask.

• Fill the flask with distilled water up to the mark on the neck of the flask.

• Mix the solution thoroughly to ensure homogeneity.

• Verify the concentration of the solution using a suitable analyti...read more

pH is a measure of the acidity or basicity of a solution. A buffer solution is a solution that resists changes in pH.

• pH is measured on a scale of 0-14, with 7 being neutral

• Acidic solutions have a pH below 7, while basic solutions have a pH above 7

• Buffer solutions are made up of a weak acid and its conjugate base, or a weak base and its conjugate acid

• Buffer solutions resist changes in pH when small amounts of acid or base are added

HPLC, dissolution and UV are analytical techniques used in pharmaceutical industry to analyze drug substances and products.

• HPLC is used to separate, identify and quantify drug substances and impurities in a sample.

• Dissolution is used to determine the rate at which a drug substance dissolves in a solvent.

• UV is used to measure the absorbance of light by a sample at a specific wavelength.

• These techniques are important in drug development, quality control and regulatory complianc...read more

There are several types of titrations, including acid-base, redox, complexometric, precipitation, and non-aqueous titrations.

• Acid-base titrations involve the use of an acid or base to neutralize a sample.

• Redox titrations involve the transfer of electrons between reactants.

• Complexometric titrations involve the formation of a complex between a metal ion and a ligand.

• Precipitation titrations involve the formation of a precipitate.

• Non-aqueous titrations involve the use of solvent...read more

pH scale ranges from 0 to 14, with values above 14 not possible.

• pH is a measure of the acidity or alkalinity of a solution on a scale of 0 to 14

• Values below 7 indicate acidity, 7 is neutral, and above 7 is alkaline

• pH above 14 is not possible as it represents an extreme level of alkalinity

Oxidation is the loss of electrons by a molecule, atom, or ion, while reduction is the gain of electrons.

• Oxidation involves the addition of oxygen or loss of hydrogen, while reduction involves the loss of oxygen or gain of hydrogen.

• Oxidation increases the oxidation state of a molecule, while reduction decreases it.

• An example of oxidation is the rusting of iron, where iron reacts with oxygen to form iron oxide.

• An example of reduction is the conversion of carbon dioxide to gluc...read more

Instrumentation skills refer to the ability to operate and troubleshoot various laboratory instruments used for analysis.

• Knowledge of different types of analytical instruments such as HPLC, GC-MS, FTIR, UV-Vis spectrophotometer

• Ability to calibrate instruments and perform routine maintenance

• Troubleshooting skills to identify and resolve instrument issues

• Understanding of data analysis software used in conjunction with instruments

• Experience in validating and verifying instrument...read more

To prepare manufacturing of medicine, one must follow strict guidelines and procedures to ensure quality and safety.

• Develop a detailed manufacturing process including raw material selection, formulation, and packaging

• Ensure compliance with regulatory requirements such as Good Manufacturing Practices (GMP)

• Perform thorough testing and quality control checks at each stage of production

• Maintain accurate documentation of all processes and procedures

• Train staff on proper manufactur...read more

FTIR is a powerful analytical technique used for identifying and quantifying chemical compounds.

• Advantages: non-destructive, rapid, requires minimal sample preparation, can analyze a wide range of compounds, can be used for qualitative and quantitative analysis

• Disadvantages: expensive equipment, requires trained personnel, may require calibration, may not be suitable for analyzing certain compounds

• Example: FTIR can be used to identify the presence of impurities in pharmaceuti...read more

Sampling of raw materials or finished products is done following specific procedures to ensure accuracy and representativeness.

• Follow SOPs for sampling raw materials or finished products

• Use appropriate sampling tools such as scoops, pipettes, or sampling thieves

• Ensure proper labeling and documentation of samples

• Store samples in suitable containers to prevent contamination

• Transport samples to the laboratory for analysis in a timely manner

Main parts of HPLC include pump, injector, column, detector, and data system.

• Pump - used to deliver the mobile phase at a constant flow rate

• Injector - introduces the sample into the column

• Column - where the separation of compounds occurs

• Detector - detects the separated compounds as they elute from the column

• Data system - records and analyzes the detector output

HPLC, dissolution, and UV are analytical techniques used in pharmaceutical analysis.

• HPLC is used to separate, identify, and quantify components in a mixture.

• Dissolution is used to determine the rate at which a drug dissolves in a solvent.

• UV is used to measure the absorbance of light by a sample at a specific wavelength.

• These techniques are commonly used in drug development and quality control.

• They require specialized equipment and training to perform accurately.

Types of titration include acid-base, redox, complexometric, and precipitation titrations.

• Acid-base titration involves the neutralization of an acid with a base or vice versa.

• Redox titration involves a redox reaction between the analyte and titrant.

• Complexometric titration involves the formation of a complex between the analyte and titrant.

• Precipitation titration involves the formation of a precipitate when the analyte reacts with the titrant.

Mole fraction is calculated by dividing the moles of a specific component by the total moles of all components in a mixture.

• Mole fraction = Moles of component / Total moles of all components

• Mole fraction is a dimensionless quantity.

• The sum of mole fractions of all components in a mixture is always equal to 1.

• For example, in a mixture of 2 moles of oxygen and 3 moles of nitrogen, the mole fraction of oxygen would be 2/(2+3) = 0.4.

API stands for Active Pharmaceutical Ingredient, RAW material refers to the basic materials used in manufacturing, and KSM stands for Key Starting Material.

• API is the main ingredient in a drug that produces the intended effect

• RAW materials are the basic materials used in the manufacturing process of a drug

• KSM is the starting material used in the synthesis of an API

• Examples of RAW materials include solvents, excipients, and reagents

• Examples of KSM include intermediates and bui...read more

Titration is a technique used to determine the concentration of a substance in a solution by reacting it with a solution of known concentration.

• Titration involves slowly adding a solution of known concentration (titrant) to a solution of unknown concentration (analyte) until the reaction is complete.

• The point at which the reaction is complete is indicated by a color change or other observable change, known as the endpoint.

• Common types of titrations include acid-base titration...read more

NC stands for normal consistency and setting time refers to the time taken for a material to harden.

• NC is the water content at which a cement paste has standard consistency for testing.

• Setting time is the time taken for a material to change from a liquid to a solid state.

• Setting time can be influenced by factors like temperature, humidity, and the composition of the material.

• For example, in cement testing, NC is determined by measuring the penetration of a standard needle int...read more

Reverse phase HPLC is a chromatographic technique used to separate non-polar compounds based on their hydrophobicity.

• Reverse phase HPLC uses a non-polar stationary phase and a polar mobile phase.

• Non-polar compounds elute first, while polar compounds are retained longer.

• It is commonly used in pharmaceutical analysis to determine drug purity and impurities.

• Example: Separation of a mixture of non-polar drugs like benzodiazepines.

A use properly manual is a guide that provides instructions on how to correctly use a product or equipment.

• Provides step-by-step instructions on how to operate the product or equipment

• Includes safety precautions and warnings

• May contain troubleshooting tips and maintenance guidelines

• Often includes diagrams or illustrations for clarity

Melting point is the temperature at which a solid substance turns into a liquid. Boiling point is the temperature at which a liquid substance turns into a gas.

• Melting point is a physical property of a substance

• It is the temperature at which the solid and liquid phases of a substance are in equilibrium

• Boiling point is also a physical property of a substance

• It is the temperature at which the vapor pressure of a liquid equals the atmospheric pressure

• Both melting and boiling poin...read more

Instrumental calibration procedures ensure accurate and precise measurements. Different procedures include external calibration, internal calibration, and standard addition.

• External calibration involves using a standard solution with a known concentration to calibrate the instrument.

• Internal calibration involves using a reference material that is added to the sample to ensure accurate measurements.

• Standard addition involves adding a known amount of a standard solution to the ...read more

Slump is a measure of consistency of concrete. IS codes are Indian Standards codes used for construction materials.

• Slump is the vertical displacement of concrete when a cone is removed.

• IS codes provide guidelines for quality and safety of construction materials.

• IS 456 is the code for plain and reinforced concrete design.

• IS 10262 is the code for concrete mix design.

• IS 1199 is the code for methods of sampling and analysis of concrete.

To make 500 mL 1:1 HCl, mix 250 mL of concentrated HCl with 250 mL of water.

• Measure 250 mL of concentrated HCl.

• Measure 250 mL of water.

• Mix the concentrated HCl and water together.

• Ensure proper safety precautions are taken when handling concentrated HCl.

Spectroscopy is the study of the interaction between matter and electromagnetic radiation.

• Spectroscopy involves analyzing the absorption, emission, or scattering of light by a sample.

• Different types of spectroscopy include UV-Vis, IR, NMR, and mass spectrometry.

• It is commonly used in chemistry to identify compounds and study molecular structures.

• Spectroscopy can also be used in quality control to ensure the purity of products.

Chromatography is a technique used to separate and analyze mixtures based on their different interactions with a stationary phase and a mobile phase.

• Chromatography is a laboratory technique for the separation of a mixture.

• It involves a stationary phase (solid or liquid) and a mobile phase (gas or liquid).

• The components of the mixture interact differently with the stationary and mobile phases, leading to separation.

• Common types of chromatography include gas chromatography, liq...read more

The sample is soluble in water at a concentration of 5g/100ml.

• The sample is water-soluble.

• The concentration of the sample in water is 5g/100ml.

• This information is relevant for determining the sample's properties and potential uses.

Moisture can be calculated by measuring the weight loss of a sample after drying it at a specific temperature.

• Weigh the sample before drying

• Dry the sample at a specific temperature for a specific time

• Weigh the sample again after drying

• Calculate the weight loss as a percentage of the original weight

• Moisture content = (initial weight - final weight) / initial weight * 100%

• Use appropriate equipment and follow standard methods for accurate results

The pH formula is used to calculate the acidity or alkalinity of a solution. Molarity is a measure of the concentration of a solute in a solution. The pH scale is a logarithmic scale that ranges from 0 to 14, with 7 being neutral.

• pH formula calculates the negative logarithm of the hydrogen ion concentration in a solution

• Molarity is the number of moles of solute per liter of solution

• The pH scale ranges from 0 to 14, with values below 7 being acidic, 7 being neutral, and values...read more

pH value is a measure of acidity or alkalinity of a solution. Organic chemistry is the study of carbon-based compounds.

• pH value ranges from 0 to 14, with 7 being neutral, below 7 acidic and above 7 alkaline

• Organic chemistry deals with the structure, properties, and reactions of compounds containing carbon atoms

• Examples of organic compounds include carbohydrates, proteins, lipids, and nucleic acids

To prepare a 1M, 1N solution, you need to calculate the amount of solute needed based on the molarity and normality of the solution.

• Calculate the molecular weight of the solute

• Determine the volume of solvent needed

• Measure out the calculated amount of solute and dissolve it in the solvent to make the final volume of the solution

• Verify the concentration using appropriate analytical techniques

Hydroquinone is a chemical compound with the formula C6H4(OH)2, commonly used in skincare products for its skin-lightening properties.

• Chemical formula: C6H4(OH)2

• Consists of two hydroxyl groups attached to a benzene ring

• Used in skincare products to lighten dark spots and hyperpigmentation

Distillation is a process of separating components of a mixture based on their boiling points.

• It involves heating the mixture to vaporize the component with the lowest boiling point.

• The vapor is then condensed and collected as a separate liquid.

• This process can be used to purify liquids, separate different components of a mixture, and extract essential oils from plants.

• Examples include the distillation of alcohol to make spirits, the purification of water, and the extraction ...read more