Answer / bhagavanji nelakanti

Masking of secondary silanol groups of bonding phase by tri
methyl silane (TMS)molecules is called as end capping. In
the bonded phase the secondary silanol molecules which shows
high polar bonding property with compound retains in the
column and those compounds elute slowly. Because of the end
capping the binding property of the secondary silanol
molecules will reduce and resulting less retention of those
compounds.

Answer / premraj behera

All the packing material(active silanol group) has been end-capped(fixed) with trimethylsilyl/double end-capped with dimethylsilyl and trimethylsilyl group. End-capped stationary phase increase column stability and reducing the solubility rate o f the silica support, and also useful for rugged method development. Double end-capped column appears to further increase column stability.

Answer / vinod kumar uppalli

The Si-OH functional groups of silica bed tend to ionize at higher pH and convert into negatively charged Si-O functional group and this interacts with acidic moieties and leads to tailing of peak due to secondary interactions. To overcome this most of the columns are end capped (Si-OH GROUP IS SHIELDED) to avoid secondary interactions.

Answer / ravi kumar thota

Silica is an amorphous polymer of silicon and oxygen. This polymer terminates at the surface of the particle as –Si-OH groups, commonly called “silanols.” These silanol groups serve as attachment sites for the bonded phase. A silane reagent, such as Cl(CH3)2SiC18H37 is reacted with the silanol to form a silyl ether (–Si-O-Si-). The bulk of the C18 group prevents bonding to all of the exposed silanols. This results in a surface that looks much like that on the left side of Figure 1, where there is a fairly high population of unbounded silanols, often termed “residual silanols.” The residual silanols are somewhat acidic and can be overly reactive with sample components, especially basic analytes, so it is preferable to reduce the population of residual silanols.

Answer / vinod kumar uppalli

The SI-OH functional groups tend to ionize at at higher pH into negatively charged group. This will lead to secondary interaction between Si-O negative and basic analytes. This leads to tailing of peak, to overcome from this issue columns are end capped.

why we use only six bowls for dissolution of a drug

1 Answers   Cipla, Natco, TelePerformance,

differance between L1 and L7 columns

5 Answers   Everest,

What is Band broading effect explain

0 Answers   Dr Reddys,

we run the same sample in same method in different flow rates in HPLC,any changes in sample analysis?

2 Answers  

why we are using in ph calibrations ph4,7,9.2 buffers only?

5 Answers   Reddy Labs,

what is MCG dilution in HPLC & GC analysis

1 Answers   Amoli Organics, Cipla,

what is difference between zero air gas and o2 gas

1 Answers   IPCA, Vasudha Pharma,

why we use deturium lamp in uv spctrophotometer other than lamps

1 Answers  

what is principle of XRD?

3 Answers   Cipla,

Why potassium hydrogen pthalate is used for perchloric acid And naoh. Why it is used for both acid and base

6 Answers   Vijayasri Chemicals,

What is FDA form 482c?

1 Answers   Lupin,

how to qualify the impurity?

0 Answers