MASS SPECTROSCOPY

Ionization potential:

The energy required to remove an electron from an atom or molecule is called ionization potential. Its unit is eV.  Most organic compounds have ionization potentials ranging between 8 to 15 eV. The energy require for removing one electron from the neutral patent molecule is usually 10 eV. However, a beam of electrons does not produce ions with high efficiency until the beam of electrons striking the steam of molecules has a potential of from 50 to 70 eV. 

Base peak:

The most intense peak in the mass spectrum is called base peak. Its intensity is highest and counted as 100%. The intensity of other peaks are determined by comparing with it. Base peak appears either due to resonance stabilization or for the formation of the ion through various common pathways. 

Instrumentation:

The instrument needed to produce the mass spectrum of a compound consists of the following parts: -----

Ion source

Mass analyzer

Ion detector.

IR SPECTROSCOPY

The molecules remain in its ground electronic state during this vibrational transition. The “true IR-region” extends from 2.5 to 15(. The region from 0.8 to 2.5( is called “near infrared”and that from 15( to 200( is called “far IR-region.”

Purpose of IR spectroscopy

The technique can be employed: ----------

To establish the identity of two compounds.

To determine the structure of a new compound.

In revealing the structure of a new compound, it is quite useful to predict the presence of certain fictional groups which absorb at definite frequencies. For example: the hydroxyl group in a compound absorbs at 3600 – 3200cm-1. Carbonyl group of ketone gives a strong band at 1710cm-1.

So IR spectroscopy is a very reliable technique for disclosing the identity of a compound.

PARENTERAL DRUGS ADMINISTRATION

This is the most suitable route of administration of drugs in treating patients who are non-cooperative, unconscious or are otherwise unable to take the medicine orally.   

DISADVANTAGES OF PARENTERAL PRODUCTS:

• It is expensive.
• People may have fear about the injectable syringes.
• These products must be maintained strictly t keep them sterile.
• Specialized equipment as well as trained persons is needed for their administration.
• These may be painful after administration.
• Application through wrong routs may prove fats.
• Daily or frequent administration of injections may pose difficulties to the patient.

CAPSULE & MICROENCAPSULATION

Types of Capsules:

Depending upon the form of the capsule shell the capsule may be classified into two types as: -----

Hard gelatin capsule

Soft gelatin capsule

Hard gelatin capsule:

Hard gelatin capsules are usually made up of a base containing plasticizers and water. The base may also contain preservatives, colors, flavors and sugars. Capsule shells are made up of two cylindrical halves, one slightly large in diameter bur shorter n length and the other slightly shorter in diameter and longer in length. The former in shown as cap and latter as body of the capsule. The drug is filled in the narrower and longer half over which the other half is fitted as a cap.

ENZYME

The non-protein substance is termed as cofactors. Commonly encountered cofactors include metal ions (Zn2+, Fe2+) and organic molecules (coenzyme)

The cofactor can be subdivided as follows: --------

Organic (coenzyme):

Tightly bound (prosthetic group)

Loosely bound (second substrate) 

Inorganic (metal ions):

Tightly bound (metallo enzymes)

Loosely bound (ion activators) 

Inorgenic Elements as Cofactors3

INSULIN

MECHANISM OF INSULIN SECRETION

Glucose is the principal stimulus to insulin secretion in human beings. The molecular mechanism of insulin secretion is follows: --------------------

Glucose enters the β cell by facilitated transport through GLUT 2, a specific subtype of glucose transporter.

The sugar is then phosphorylated by glucokinase, or hexokina敳桴湥

se, then undergoes metabolism and oxidation to CO2 and H2O. An offshoot of this process, probably a rising ATP/ADP ratio.

As a result, the ATP-sensitive K+ channel is blocked which cause membrane depolarization.

UV SPECTROSCOPY

When a molecule absorbs visible or ultraviolet energy, an electron or electrons will be raised to a higher energy level if the energy requirement for that transition is equal to the energy of the incoming photon. The electrons is the inner shells of atom and those that are shared by two adjacent atoms not affected to the same degree by incoming radiation as those that can’t be localized within the molecule. Electrons of the latter type give rise to spectra in the UV and visible regions of the electromagnetic spectrum.

Saturated double bond will not absorb ultraviolet energy. Presence of chromophore is essential in a saturated compound for absorption of radiations at UV and visible regions. Presence of auxochrome cause a bathochromic shift i.e. absorption maxima shifts to longer wave length.

TABLET

Advantages:

The major advantages of tablets over capsules, which has recently proved significant, is that the tablet is an essentially tamperproof dosage forms.

Disadvantages:

• Some patient particularly children and the seriously ill – persons may not be able to swallow tablets.
• Some drugs resist compression into dense compacts, owing to their amorphous nature or flocculent, low – density character.
• Drugs with poor wetting, slow dissolution properties, intermediate to large dosage, and optimum absorption in gastrointestinal tract or any combination of these features may be difficult or impossible to formulate or manufacture as a tablet that will still provide adequate or full drug bioavailability.
• Bitter tasting drugs, drugs with an objectionable odour or drugs that are sensitive to oxygen or atmospheric moisture may require encapsulation or entrapment prior to compression or the tablets may require coating. In such case, the capsule may offer the best and lowest cost approach.