10+ Analytical Chemistry Associate/Scientist Interview Questions and Answers

During the development of an analytical method, I faced issues with instrument calibration and sample preparation.

• One issue I encountered was inconsistent instrument calibration, which resulted in inaccurate measurements. To solve this, I thoroughly checked the calibration procedure and recalibrated the instrument as needed.

• Another challenge was optimizing the sample preparation process to ensure reliable and reproducible results. I experimented with different extraction tech...read more

All peaks, including known and unknown impurities, should be separated in degradation products method.

• Separating all peaks is important for accurate identification and quantification of impurities.

• Compromising on certain peaks may lead to inaccurate results and potential safety concerns.

• Advanced analytical techniques such as high-resolution mass spectrometry can aid in identifying unknown impurities.

• Proper validation of the method should be performed to ensure accuracy and re...read more

I would investigate the cause of the dissolution failure and propose solutions.

• Conduct dissolution testing to confirm the issue

• Analyze the formulation and manufacturing process for potential issues

• Consider adjusting the formulation or manufacturing process

• Consult with colleagues and experts for additional insights

• Develop a plan for further testing and evaluation

The increasing impurity peak above the detection limit in excipient compatibility studies suggests a potential issue with the formulation.

• The impurity peak may indicate degradation or reaction of the excipient with the drug product (DP).

• Further investigation is needed to identify the impurity and its source.

• The formulation may need to be modified to prevent or reduce the impurity formation.

• Additional stability studies should be conducted to assess the long-term impact of the ...read more

Crystallography has significant impact on finished product and dissolution.

• Crystallography helps determine the structure and arrangement of molecules in a crystal lattice.

• This information is crucial for understanding the physical and chemical properties of the finished product.

• Crystallography can provide insights into the dissolution behavior of a substance.

• By studying crystal structures, scientists can predict how a substance will dissolve and its bioavailability.

• For example...read more

ODS and BDS columns are both used in chromatography but differ in their stationary phase.

• ODS (Octadecylsilane) columns have a hydrophobic stationary phase and are used for non-polar compounds.

• BDS (Butylsilane) columns have a more polar stationary phase and are used for polar compounds.

• ODS columns are more commonly used than BDS columns.

• Both columns have different selectivity and retention characteristics.

C8 and C18 columns differ in their hydrophobicity and selectivity.

• C8 columns have shorter carbon chains than C18 columns.

• C8 columns are less hydrophobic than C18 columns.

• C8 columns are more selective for less hydrophobic compounds.

• C18 columns are more selective for more hydrophobic compounds.

• C8 columns are often used for separating polar and nonpolar compounds.

• C18 columns are often used for separating nonpolar compounds.

• C8 columns have a lower retention time than C18 columns....read more

Retardation factor is the ratio of the distance traveled by a solute to the distance traveled by the solvent in a chromatography experiment.

• Retardation factor is a dimensionless quantity.

• It is used to identify and separate different components of a mixture in chromatography.

• It is calculated by dividing the distance traveled by the solute by the distance traveled by the solvent.

• Retardation factor values range from 0 to 1.

• A higher retardation factor indicates that the solute is...read more

Bunsen reaction involves the reaction of a metal with a non-metal to form an ionic compound.

• The reaction is named after Robert Bunsen, a German chemist.

• It is a type of redox reaction.

• The reaction formula is: Metal + Non-metal → Ionic Compound

• For example, the reaction between sodium and chlorine to form sodium chloride (Na + Cl2 → 2NaCl).

Lambert Beer Law states that the absorbance of a solution is directly proportional to the concentration of the absorbing species.

• The law is used to determine the concentration of a substance in a solution by measuring its absorbance.

• It assumes that the absorbing species is uniformly distributed throughout the solution.

• The law is expressed as A = εcl, where A is the absorbance, ε is the molar absorptivity, c is the concentration, and l is the path length.

• The law is widely used...read more