Determination of moisture and fat in meats by microwave and nuclear magnetic resonance analysis: collaborative study

Ten laboratories participated in a collaborative study to determine the total moisture and fat in raw and processed meat products by microwave drying and nuclear magnetic resonance (NMR) spectroscopy. Meat products were prepared following the AOAC Method and analyzed using CEM Corp.'s SMART Trac Moisture and Fat Analysis system. SMART Trac provides moisture results by measuring the weight loss on drying by microwave energy. The dried sample is then analyzed by NMR spectrometry for fat content. Moisture and fat results are displayed and reported by the SMART Trac as a percentage (g/100 g). Microwave drying is an AOAC-approved reference method (Method 985.14), Moisture in Meat and Poultry Products. NMR spectrometry is a secondary technique used to determine the concentration of various constituents in biological, organic, or chemical samples. The study design was based on Youden's matched pair principle for collaborative tests. For the purposes of this study, 10 laboratories each tested 10 Youden matched pairs, for a total of 20 samples. The study samples represented a range of products processed daily in plant operations. Included were raw meat samples (beef, pork, chicken, and turkey) as well as processed meats (beef hot dog, pork sausage, and ham). The total moisture content of the undiluted samples, as received for the purposes of this study, was determined by AOAC Method 950.46 and ranged from 54.03 to 74.99%. The total fat content of the undiluted samples was determined by AOAC Method 960.39 and ranged from 1.00 to 29.79%. Statistical analysis of study results for total moisture yielded a relative standard deviation for repeatability (RSDr) range of 0.14 to 0.95% and a relative standard deviation for reproducibility (RSDR) range of 0.26 to 0.95%. Statistical analysis for total fat yielded similar RSDr and RSDR range of 0.74 to 4.08%. Results for turkey had higher RSDr and RSDR values, both at 12.6%, due to low fat content and possibly to the separation of the samples observed by some of the collaborators. Results demonstrate that microwave drying with NMR is a rapid, practical method providing results equivalent to AOAC Methods 950.46 (Forced Air Oven Drying) and 960.39 (Soxhlet Ether Extraction) in raw and processed meat products.     

Hydrogen electrocatalysis on overlayers of rhodium over gold and palladium substrates--more active than platinum?

We have investigated the stability and catalytic activity of epitaxial overlayers of rhodium on Au(111) and Pd(111). Both surfaces show a strong affinity for hydrogen. We have calculated the energy of adsorption both for a strongly and a more weakly adsorbed species; the latter is the intermediate in the hydrogen evolution reaction. Both the energy of activation for hydrogen adsorption (Volmer reaction) and hydrogen recombination (Tafel reaction) are very low, suggesting that these overlayers are excellent catalysts.     

Nanoscale patterning of alkyl monolayers on silicon using the atomic force microscope

Self-assembled monolayers (SAMs) of 1-alkenes on hydrogen-passivated silicon substrates were successfully patterned on the nanometer scale using an atomic force microscope (AFM) probe tip. Nanoshaving experiments on alkyl monolayers formed on H-Si(111) not only demonstrate the flexibility of this technique but also show that patterning with an AFM probe is a viable method for creating well-defined, nanoscale features in a monolayer matrix in a reproducible and controlled manner. Features of varying depths (2-15 nm) were created in the alkyl monolayers by controlling the applied load and the number of etching scans made at high applied loads. The patterning on these SAM films is compared with the patterning of alkyl siloxane monolayers on silicon and mica.     

Spectrophotometric determination of manganese with 2-oximinocyclohexanone thiosemicarbazone

The 2-oximinocyclohexanone thiosemicarbazone forms, in basic medium, a violet complex with Mn(III) whose stoichiometry is 3:1 (reagent:Mn(III)). The molar absorptivity has a value of 3000 liters · mol⁻¹ · cm⁻¹. By means of the formation of this complex manganese can be determined between 9 and 400 μg with a relative error (95% confidence level) of 0.20%. The effect of foreign ions has been examined and the method has been applied to Mn(II) determination in Lincolnshire iron ore.