Question { Oxygen Healthcare, 19160 }

viod volume and dead time

Answer

void volume means volume taken to elute Unretained solute
(Do not interact with packig material)from column after
injection....





Paresh Jobanputtra...Cadila

Question { Reddy Labs, 20766 }

what is the value of pH

Answer

pH is the minus logarithum of the concentration of H+ ion to
the base 10..scale 0 to 14 (discovered by SORENSON)
Less than 7-Acidic in nature
Greater than 7-Basic in nature
and equal to 7-neutral in nature
1st crireria is the soln must be an aqueous soln..
2nd thing its must be an electrolyte..
we can see pH value only that soln whose concentration is
below or equal to 1M...

Question { Dr Reddys, 32328 }

Why we are using only KBr in IR spectrometer why not KCl

Answer

Actuly alkli halide are used for this perpose..because they
are inert and could not have any absorbance in IR range..so
we can use kcl instead of kBr...

Question { Cadila, 28151 }

How to prepare 50 ppm ammonia solution form 25% ammonia
solution?

Answer

Take 20mg Ammonia soln and make up it 100 ml...
then it is Prepered 50 ppm of ammonia soln....





Paresh Jobanputtra....Cadila

Question { 16579 }

Why noise test is performed at 254 nm in calibration of HPLC
system?

Answer

Earlier fixed wavelength detector is mostly used i.e 254 nm
because almost all Benzene ring containing compounds absorbs uv light
at 254 nm. i think due to this reasons only.

Regards,
Paresh Jobanputtra

Question { 66501 }

How to prepare ppm solution of Nacl form its salt?

Answer

Hi Dear
If i want to make 70 ppm of Chloride solution from its Nacl salt
then i have to take 11.2 mg of Nacl salt in 100 ml of Solvent.
e.g Mol wt of Nacl # 58.5 gm per mole.
Na+cl#23+35.5.
it means 58.5 mg of Nacl salt in 1000ml of Solvent contains 35.5 ppm of Chloride.
but i want to make 70 ppm Chloride solution
so, 35.5 ppm----->58.5 mg Nacl salt
70 ppm-----> ?

=70*58.5/35.5(in 1000 ml of solvent)
=115.39 mg
so, 11.539 mg in 100 ml of solvent.

Regards,
Paresh Jobanputtra.

Question { Matrix, 48855 }

water is more polar than acetonitrile.but in reverse phase chromatography peaks elute earlier when we increse Acetonitrile.what is the reason.

Answer

Actually What happen,When we mix Acetonitrile with buffer then VISCOSITY is decresed of mobile phase.
"As viscosity decreased, Mass transfer of solute particle with stationary phase is decreased"
So but obvious component elute earlier.

Regards,
Paresh Jobanputtra

Question { Orchid, 8276 }

what type of compounds do we see lod @ wat type compounds do
we see m.c

Answer

In Moisture content analysis by Karlficher instrument (free water content), by TGA(trapped water content) we can find only water content.
but by LOD we con find Water content as well as Lower boiling point organic solvents too.
So what u want to find this depends on this factors.

Regards,
Paresh Jobanputtra

Question { MSN Pharma, 31714 }

In case of HPLC coloums what is the difference Between C8 &
C18 coloums & how can we select difference type of coloums
like Inertial ODS , Hypersil BDS , ODS etc.?

Answer

in case of C8 column,C8 carbon chain is attached to the packing material
and in case of C18(ODS) column, C18 carbon chain is attached to the packeting material.
eg. OH
¡
OH-SI-O-C8 orC18
!
OH
Some names of specially treated stationary phases:suitable for separation of BASIC compds.
like Inertsil:"Inert towards bases"
BDS :"Base deactivated silica"
different make columns have different characteristics
like different Carbon load,Specific pore volume(empty spaces betn particles),Specific surface area,Ligand density etc.
If the carbon load is high it means specific pore volume is lesss so retained capability of packing material is high so capacity factor is high. so retemtion is better of this column.
and selection of column is depends on nature of product, and no of trials in developement.

Regards,
Paresh Jobanputtra.