3/20/2014 1 Use of Chromatography in Laboratory Analysis • Many analytical procedures use spectrophotometry and chromatography to determine nutrients • Examples: – Amino acids -- amino acid analyzer – Minerals • atomic absorption spectrophotometer • Inductively coupled plasma spectrophotometer – Fatty acids --- gas chromatography – Vitamins, Carbohydrates -- HPLC – Multiple feed components • near infrared reflectance (NIR) Spectrophotometry: used for hundreds of compounds glucose, cholesterol, urea, minerals Chromatographic Analysis • Thin layer • Liquid chromatography – Amino acid analysis • Gas Chromatography – Fatty acid analysis • HPLC (high pressure liquid chromatography) – High performance – Used for amino acids, steroid hormones, vitamins – Drug residue analysis, etc.3/20/2014 2 Gas Chromatography: -used to determine fatty acid profile -saturated, unsaturated, chain length -typically run at 200-240 C An inductively coupled plasma (ICP) is a very high temperature (7000-8000K) excitation source that efficiently desolvates, vaporizes, excites, and ionizes atoms. Molecular interferences are greatly reduced with this excitation source but are not eliminated completely. Allows determination of multiple minerals in each run. Atomic-absorption (AA) spectroscopy uses the absorption of light to measure the concentration of gas-phase atoms. Since samples are usually liquids or solids, the analyte atoms or ions must be vaporized in a flame or graphite furnace. The analyte concentration is determined from the amount of absorption. Atomic Absorption and ICP - mineral profile3/20/2014 3 NIR Can be used for a variety of determinations. It is an approved AOCS procedure for determination of Crude Protein, ADF and moisture. It is also used for amino acids, starch, fatty acids, and phosphorus. Extensive validation is needed for each sample type and analyte. Analytical Procedures • Considerations – In feed mill vs commercial lab – Cost: • Amino acid and Fatty acid analysis $50-100 per sample – Speed: • Amino acid – several days • NIR or Nitrogen analyzer –dozens per hour –
View Full Document
Unlocking...