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A: Melamine is an organic compound that is rich in nitrogen. When combined with formaldehyde it produces melamine-resin. Melamine-resin is widely used in several textiles, plastics, adhesives, flame-resistant products, and some cleaning agents.

 

A: Melamine is illegally added to food to artificially elevate the protein content values of products. The Kjeldahl method, which is used to determine protein content, works by testing for nitrogen content. When protein is digested, nitrogen is released and converted to ammonia. The amount of ammonia is determined by titration and is correlated to the amount of protein present. This method yields falsely high numbers when nonprotein nitrogen is in the sample.

A: The first melamine scare dates back to 1987 when contamination occurred in several beverages such as coffee, orange juice, lemon juice and fermented milk. This contamination was caused by leaching of melamine from melamine-resin cups. In 2004 and again in 2007 melamine contamination in rice and wheat gluten made thousands of animals sick, sometimes resulting in death. The most recent melamine scare was in 2008 when contaminated milk powder resulted in recalls of infant formula, biscuits, candies and several other products containing milk powder.

 

A: The Food and Drug Administration (FDA) has set tolerable daily intakes (TDI) for melamine for infant and noninfant food stuffs. The TDI for noninfant food is 0.63mg of melamine per kg of body weight per day (0.63mg/kg bw/d). This equates to about 2.5 part per million (ppm) or ?g/g in a given food commodity. For infant formula the FDA has set the TDI at 0.063mg/kg bw/d. This is a 10-fold safety factor to account for the fact that the majority of infants total caloric intake is from infant formula. This TDI equates to about 1ppm or 1?g/g in a given food commodity. The World Health Organization (WHO) has set their TDI for all food at 0.2mg/kg bw/d. Although none of these TDIs are reported as “safe” these are the amounts that have been determined, based on rat studies, that should yield no increased human health risk. | www.who.int/en/

 

A: The solubility of melamine alone is 3.1g/L in water. However, when the combination of melamine and cyanuric acid form the crystal structure melamine cyanurate, the solubility significantly decreases to 0.01g/L in water, due to the strong hydrogen bonding that takes place in the melamine cyanurate crystals.

 

A: Backflash occurs when the vapor expansion volume of a solvent is larger than the internal volume of the injection port liner. This can cause sample carryover, gas line contamination, or decreased analyte response. Use Restek’s backflash calculator to determine if you will have any issues. If you determine that you do have backflash, there are several ways to try and alleviate this problem. Decreasing injection volume, decreasing injection port temperature, and slowing down the total flow are all ways to help avoid backflash.

A: Derivatization is a chemical process where a chemical compound is transformed into a product with a similar structure but often different functionalities. Melamine and related analogs are not volatile compounds. By derivatizing these compounds they are converted to a volatile derivative of melamine therefore allowing these compounds to be analyzed by gas chromatography.

 

A: The derivatisation reagent BSTFA is a trimethylsilyl donor that reacts with a wide range of polar compounds to replace noncarbon bonded hydrogens with a –Si(CH3)3 group. Therefore, if any water is present, it will compete for the derivatisation reagent and may result in the incomplete derivatisation of the analytes of interest.

 

A: When making a reference standard there are two different types of standards that can be utilized. Solvent-only standards are standards that are made in the extracting solvent alone. This type of standard is the most commonly used. Matrix-matched standards are standards that are spiked into the blank matrix extract. Matrix-matched standards are useful when any type of matrix effect is taking place. A matrix effect can alter the intensity of a given analyte, yielding false positives and sometimes false negatives.

 

A: Matrix protection effects are matrix-based effects that enhance (or protect) the signal of an analyte, compared to what would be observed without the matrix being present. When a sample is injected into a GC, some matrix components may interact with active sites in the injection port, thereby reducing the potential for interactions between those active sites and the target analytes. These matrix components are termed analyte protectants and their interactions with active sites prevent target analyte absorption and minimize degradation, ultimately increasing the overall signal of an analyte in a commodity, in comparison to the response that would be seen for the analyte in solvent alone.1,2,3