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Analytical Chemistry Interview Questions and Answers


This page contains the collection of Analytical Chemistry Interview Questions and Answers / Frequently Asked Questions (FAQs) under category Science. These questions are collected from various resources like informative websites, forums, blogs, discussion boards including MSDN and Wikipedia. These listed questions can surely help in preparing for Analytical Chemistry interview or job.

What is deference between the working standard and reference standard?
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

How do we fix the sample concentaryion in hplc method development. what is the basis?
IF ALL IMPURTITIES AT SPEC LEVEL ARE MEETING S/N RATIO MORE
THAN 60 AT THAT PARTICULAR CONCENTRATION AS WEL AS NO
COLUMN OVERLOAD.

Suppose we prepared pH buffer solution in lab.and calibrate against NIST solution, and same shall going to used upto 30 days. is it possible to stable pH and apperance? suggest?
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.

What is rs test why we are perfoming rs test?
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

What is difference between silica used in TLC and HPLC column?
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.

What is use of acetonitrile compare to methanol in RP-HPLC Method development?
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.

How to know HPLC column performance?
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.

What is heavy water?
Isotopes of H2O, D2O

What is quality controle?
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

When we get Moisture content by KF higher than by LOD, what does this indicate?
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.

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

How to calculate signal to noise ratio by this formula 2H/h where h from where and how to measure?
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)

WHAT IS USE OF ION PAIR REAGENTS?
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.

Explain What is a base line?
#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..
1)Cyclic base line
2)Synchorinise noise
3)Asynchorinise noise
4)Base line drift
5)Spikes
6)Negative peaks
7)No peaks

#Base line noise is attributed due to mobile phase,sample,
system problems.leaks in the system,temperature variations
in lab etc..

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?
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

WILL YOU DRY DST BEFORE FACTOR DETERMINATION BY USING KARL FISHER TITRATOR?
NO

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