This document discusses the principles and applications of CHNS elemental analyzers. CHNS analyzers determine the levels of carbon, hydrogen, nitrogen, and sulfur in organic materials through combustion. Samples are burned at high temperatures, converting the elements to gases that are then detected using techniques like gas chromatography or thermal conductivity. The instruments are used widely in fields like pharmaceuticals, polymers, chemicals, foods, and oil refining to analyze sample composition and monitor processes.

1. SUBMITTED BY: ANUPAMA.C.P
1 SEM M-PHARM

2. INTRODUCTION
 CHNS elemental analysers provide a mean for the rapid
determination of carbon, hydrogen, nitrogen, and sulphur
in organic matrices and other type of materials.
 They are capable of handling a wide variety of sample
types including solids, liquids, volatile and viscous
samples in the fields of pharmaceuticals, polymers etc.

3. PRINCIPLE
In combustion process ( furnace at 1000°c)
 Carbon is converted into carbon dioxide
 Hydrogen to water
 Nitrogen to nitrogen gas / oxides of nitrogen
 Sulphur to sulphur dioxide
• If other element such as chlorine is present , they converted
into combusion products, such as hydrogen chloride.
• Combusion prdts are swept out from the chamber using inert
gas (helium) and passed over heated high purity copper.

4.  The gases then passed through adsorbent trapes to leave
only Co2, H2O, N2,SO2.
 Determination can be carried out in a variety of ways
 GC separation followed by qualification using thermal
conductivity detection.
 A partial separation by GC followed by thermal
conductivity.
 A series of infra red and thermal conductivity.

5. INSRUMENTATION

6.  Combustion elemental analysis are manufactured in a
variety of configurations to suit specific application,
element of interest, sample type and size etc.
 All instruments require two gas supplies:
1. An inert carrier gas (helium recommended)
2. High purity oxygen ( minimum 99.9995%)
 Strict specification for oxygen is associated with the
need to reduce the nitrogen “blank” contribution.
 Additionally, GC type gas filters are also usually fitted
to prevent trace organic species and water entering the
combusion.

7.  The choice of sample introduction system will depend on
the application and sample type
For solids or viscous liquids, samples are weighed out
into tin capsules.
For liquids, samples can be sealed in individual vials or
introduced via a liquid auto sampler.
 Both capsules and vials are pre-cleaned and dried to avoid
trace contamination from water and oils.

8.  Instruments are classified as ‘static’ or ‘dynamic’ in terms
of their combustion characteristics.
 In the static type a pre-set volume of oxygen is added
to the combusion tube before the sample is introduced.
In the dynamic type ,the oxygen is added to the tube at
the same time as the sample introduction and continuous
to flow for a set time.

9. APPLICATIONS
In analytical laboratories for over thirty years.
Used in pharmaceuticals, chemicals, oil-related products,
catalysts and foods.
In oil industry, regular monitoring of coke build up on
refinery catalyst to ensure that regeneration procedures.
In food analysis, the determination of nitrogen is
important for pricing grain and evaluating meat products.

10. REFERENCES
 www. Slideshare . net
 Elemental impurities- chns analysis