Elemental Microanalysis for C,H,N,S,O
Both solid and liquid samples of organic and metallo-organic compoundscan be analysed for %C, %H, %N, %S, %O.
A minimum 5mg sample is required as samples are run in duplicate and a further 2mg if O is required. Use screw cap tubes to preserve your sample. If samples are difficult to remove due to electrostatic charge etc., then at least twice that amount will be required. Samples must be clean (no foreign particles) and dry. If samples are sent by mail they should be in plastic containers with the lids sealed.
Many materials are very often unhomogeneous, and an appropriate homogenisation procedure is therefore required. Important: the reproducibility of results is independent of the sample size but strongly dependent of the sample homogenity.
Dry and soft materials
Samples like cereals, dry bread, plant tissues, etc.: grind the sample in a rotor mill equipped with a 1 mm. Sieve, possibly with trapezoidal holes. According to AOAC 992.03 method, the suitable fineness of grind is that which gives relative standard deviation (RDS) < 2 % for 10 successive determination of nitrogen.
Dry mixtures of hard, soft and tough materials
Samples like rock-containing soil, shale, mining slags, etc.: a crushing mill is first of all to crush the hard required the hard particles and to mix them with the rest of the sample; a second grinding process in a ball mill is also required in some cases
Dry or wet soft materials
Materials like meat, sausages, fish meat, etc.: grind in a knife mill with liquid nitrogen. Place the sample in the mill, add liquid nitrogen, wait about 1 minute, add liquid nitrogen again and start the mill.Thanks to the action of liquid nitrogen, the sample is immediately frozen at –195°C and becomes extremely brittle and fragile. A mild grinding action is then enough for the complete destruction of the texture of the sample, and the heat generated by the mill action will not affect the water content because it will be adsorbed by the nitrogen evaporation.
Rape-seeds and other oil-containing seeds, which become smeary when ground at room temperature, form a homogeneous dry powder. Meat, fresh plant tissues and similar wet products form a homogeneous paste.
When liquid nitrogen is not available, it is possible to freeze the sample (at least –25°C, minimum 1 hour) and to grind it when deeply frozen.
Materials containing volatile compounds
Sometimes it is important that the material to be ground does not lose volatile constituents or take up moisture. Liquid nitrogen, which is added to the container, is quite dry, and all moisture in the sample is immediately frozen and cannot escape. When liquid nitrogen is volatilized from the container, the sample is still so cold that no volatile constituents are volatilised. After shaking, the container is allowed to warm up to room temperature unopened so that no atmospheric moisture can condense on the cold sample. The homogenized sample has the same moisture content and the same content of volatile constituents as the original material.
|Mortar (agate or porcelain)||Coals, soils|
|Coffee mill||Cereals, barley, meal|
|Hammer mill||Textiles, paper|
|Ball mill (*)||Solids (coals, cokes)|
|Ball mill + liquid nitrogen||Hard materials (bones, textiles, hair), wet products (meat, fresh vegetables)|
|Rotor speed mill (**)||Cereals, plants, plastics, synthetic resins, soils, animal feeds, drugs, grain, coal, fertilizers|
|Scissors, blades||Leaves, fibers, plastic products, rubbers|
(*) The microdismembrator is a very strong, longitudinally shaking ball mill. The materials to be ground is placed into an egg-shaped teflon container together with 2-4 steel balls, which should have different diameters, usually 10 mm and 7 mm diameter.
(**) The samples are ground by the impact and shearing stresses from the high-speed rotor and are forced through the sieve by the ultra-centrifugal force. The ground material is collected in a collecting vessel. It is possible to grind up to 0.5-1 mm particle size.
Analysis of data
SCMB users - $24 for CHNS; $24 for Oxygen; $48 – CHMS&O, total of 5 samples required
Non-SCMB users - $60 -CHNS, $60 – Oxygen; $120 – CHNS&O
Next day Express service: $120 –CHNS or $120 – Oxygen; only one type of analysis is possible per day
Michael Nefedov: email@example.com; 0427428089, 07-33651833;