Analytical Chemistry Interview Questions & Answers

Question 1. What Is Standard Deviation?

Answer :

Standard deviation tells about the widely spread out of the measured analytical data points. Highly precised measurements are less standard deviation.

Question 2. How To Calculate Signal To Noise Ratio By This Formula 2h/h Where H From Where And How To Measure?

Answer :

The H is the height of the main peak and the h is the lowest height of a peak in the range of X5 the main peak (around the amin peak).

Question 3. What Is Use Of Ion Pair Reagents?

Answer :

The chemical substances that pair each other, to form complexes. These can use for stabilization of one of the molecule that is more active or to colorifying etc.

Question 4. Explain What Is A Base Line?

Answer :

• Base line is nothing but the detectors response to the mobile phase.(gc,hplc) 
• Base line should be stable to start a run. 
• Un stabilized base line is called as base line noise. 
• Base line noise is of many types.. 
• Cyclic base line 
• Synchorinise noise 
• Asynchorinise noise 
• Base line drift 
• Spikes 
• Negative peaks 
• No peaks
• Base line noise is attributed due to mobile phase,sample, system problems.leaks in the system,temperature variations in lab etc..

Question 5. What Is Deference Between The Working Standard And Reference Standard?

Answer :

Reference std is like USP,EP std , in this std we get COA including results of Potency by HPLC , NMR & XRPD data. whenever there is requirement of w.std preparation first we have get API rawmaterial from warehouse & we check assay , water content or LOD & Related substances aganist reference std . Some times we are doing analysis in duplicate & get mean value.then we decide final assay or potency value & it's validity one year

Question 6. How Do We Fix The Sample Concentaryion In Hplc Method Development. What Is The Basis?

Answer :

If all impurtities at spec level are meeting s/n ratio more than 60 at that particular concentration as wel as no column overload.

Question 7. Suppose We Prepared Ph Buffer Solution In Lab.and Calibrate Against Nist Solution, And Same Shall Going To Used Up To 30 Days. Is It Possible To Stable Ph And Appearance? Suggest?

Answer :

PH of the buffer solution will be change, as due to presence of nitrogen containing substances and also due to microbial growth. but if stored at 4 degree centi. it may used to some extent.

Question 8. What Is Rs Test Why We Are Perfoming Rs Test?

Answer :

RS stands for related substance, means by-products upon completion of reaction, or the unreacted portion present in the product. RS testing help us to identify the adequate quantitiy of these by-products or unreacted part. More over RS help us during the stability study to know any significant change in the nature of product during long storage in various climatic conditions

Question 9. What Is Difference Between Silica Used In Tlc And Hplc Column?

Answer :

Tlc is called thin layer chromatography. The simple technique works on the principle of adsorption, where as HPLC is a sophisticated technique works on partition principle.

Question 10. What Is Heavy Water?

Answer :

Isotopes of H2O, D2O.

Question 11. How To Know Hplc Column Performance?

Answer :

Check for the number of plates that it maintains stady all over the run , check the SST at avery run that cpmplies the acceptance criterias of the method.

Question 12. What Is Use Of Acetonitrile Compare To Methanol In Rp-hplc Method Development?

Answer :

ACN is highly polar as compare to Methanol So provide Better resolution for many compound and it has property to form hydrogen bond so provide better selectivity.

Question 13. What Is Quality Control?

Answer :

quality control means to maintain the quality of product by calculating their content ,different physical parameters,as per their specification IP/BP/USP/EP/JP.

Question 14. When We Get Moisture Content By Kf Higher Than By Lod, What Does This Indicate?

Answer :

KF titration is the most accurate method in analysing moisture content. But it is coastlier and maintaince is too high. So in analysis of moisture content an alternative experiment is Loss on Drying(LOD), which gives approximate moisture value present in the given substance.

Question 15. Will You Dry Dst Before Factor Determination By Using Karl Fisher Titrator?

Answer :

No, We will not dry dst before factor determination by using karl fisher titrator.

Question 16. In Rs Method Development When We Are Going Area Normalization Method To Dilute Standard Method?

Answer :

When analyte gives linear response then only we can use area normalization. When analyte response is to high and saturated in chromatograph, for this condition we can use diluted standard.

Question 17. In The Gas Chromatography What Is Used Carrier Gas And Make Up Gas?

Answer :

In the gas chromatography, nitrogen gas  is used carrier gas and make up gas.

Question 18. What Is The Difference Between Chromatographic Purity And Related Substances?

Answer :

• Purity is only area normalization.
• Rs is calculated by using std and rrf.

Question 19. What Is The Difference Between C8 And C18 Hplc Column?

Answer :

C8 column have more polar than C18. and it has 8 carbon atoms.

Question 20. Why Karl Fisher Factor Is 5 ?

Answer :

5 mg of water consuming 1 ml of KF reagent.

Question 21. In Ph Calibration,calibration Is Done For Ph Meter Or Electrode?how Will You Judge That The Meter To Be Calibrated With 4,7,9.2 Buffers?explain Temperature Effects On Ph?

Answer :

calibration is also one of the system suitability test,whether the system working satisfactory or not physically so when you do the calibration for pH meter with standard pH buffer solution (which is from NIST-it may accurate solution for actual pH)and once if your instrument has calibrated,you can cross verify your insrument against those pH buffer solution (NIST) and the acceptable range is +/- 0.02 then you can conclude for. once if temperature raises the pH will decrease and its not all cases.

Question 22. What Is Similarity Factor And Its Use In Api Strength?

Answer :

it is having both regulatory and domestic markets.

Question 23. What Is Delay Volume?

Answer :

The volume from gpv to detector.

Question 24. Why Six Unit Used For Precision?

Answer :

Since it is performed as per ICH guidelines for validation.

Question 25. Loss Of Linearity In Tkn Analysis, Possible Reasons?

Answer :

Contamination in calibration standards during the TKN digestion.

Question 26. What Is The Use Of Tlc And Hplc? And When And Where Use?

Answer :

TLC is used to check wheather the reaction is completed or not. HPLC is used to identify, quantify,and for separation of mixture.