Direct determination of molybdenum in polyvitaminic tablets by voltammetry in non-aqueous media.

Adsorptive stripping voltammetry carried out in a homogeneous ternary solvent composed of N,N-dimethylformamide, water and ethanol, with alpha-benzoinoxime (alpha BO) as the complexing agent for Mo(VI) and a 0.5 mol L-1 acetic acid - sodium acetate buffer as supporting electrolyte was successfully used for the determination of molybdenum in polyvitamin-polymineral tablets. Tablet samples were analyzed and the results were compared with those obtained both by graphite furnace atomic absorption and by recovery tests, with good correlations. indicating that this may be considered as an alternative procedure for routine determination of Mo(VI) in pharmaceutical samples.29115315

Vegetable oil stability at elevated temperatures in the presence of ferric stearate and ferrous octanoate

The thermoxidative stability of partially hydrogenated soybean oil (PHSBO) was examined after addition of ferric stearate and ferrous octanoate, and then heating the samples at 120, 160, 180, and 200 degrees C. In a second experiment, the effect of iron concentration (ferric stearate) on PHSBO stability was examined at 180 degrees C, and at concentrations of approximately 0.5 and 1.2 mg of added iron/kg PHSBO. Oil samples were heated continuously for 72 h and sampled every 12 h. The acid value, p-anisidine value, color, dielectric constant and the triacylglycerol polymer content of oil samples were compared to oil samples containing no added iron. Generally, the value of each oxidative index increased with (1) an increase in temperature, (2) an increase in heating time, and/or (3) an increase in iron. The results demonstrate that low concentrations of iron will substantially increase the rate of oxidation for vegetable oil samples heated to temperatures of 120 degrees C to 200 degrees C.5362088209

Iron accumulation in oil during the deep-fat frying of meat

Iron accumulation in oil is a potential problem when frying food containing substantial amounts of iron. Selected meat products (skinless chicken breast, beef liver, and lean beef) were ground and fried (ca. 2-cm spheres, ca. 10 g/sphere) in partially hydrogenated soybean oil (PHSBO). Samples (450 g) of ground meat were fried 3 times/h for 8 h/d for 3 d. Oil samples were collected for analysis for iron (every 8 h) and oil degradation (every 4 h) and replaced with fresh oil. The iron contents of oil samples after 3 d of frying were approximately 0.11, 0.48, and 4.01 mg of iron/kg of PHSBO for the oil used to fry chicken, beef, and liver, respectively. There was a notable darkening in color and an increased tendency to foam for the beef liver oil sample compared with the other samples. After frying, the acid values were 0.9, 1.1, and 1.4 for the oil samples for chicken, beef, and liver, respectively. After frying, the p-anisidine values were 11.5, 12.8, and 32.6 for the oil samples for chicken, beef, and liver, respectively; the food oil sensor values were 0.96, 0.96, and 0.83 for the oil samples for chicken, beef, and liver, respectively.82424925

Acceleration of the thermoxidation of oil by heme iron

Transition metals, including iron, occur naturally at significant concentrations in meat. Iron can be extracted from the food into the oil and potentially decrease the stability of the oil during frying by accelerating thermoxidation. The objective was to examine the thermoxidative stability of partially hydrogenated soybean oil after addition of heme iron. Heme iron (2.7 ppm) was added to the oil, and then oil samples were heated continuously at 160, 180, or 200 degrees C for 72 h. Oil samples were removed for analysis every 12 h. The acid values, color, food oil sensor readings, and TAG polymer content of the heated oil samples were compared with oil samples containing no added iron that were held at the same temperatures. Generally, each oxidative index increased with (i) an increase in temperature, (ii) an increase in heating time, and/or (iii) the addition of iron. Generally, the extent of oxidation was greater for samples heated at 200 degrees C than for oil samples heated at 160 or 180 degrees C. The oil samples heated at 200 degrees C reached the target polymer content of 20% after 27 h of heating. If heme iron accumulates in the oil, it will increase the rate of oxidation and thermal degradation and reduce the frying life of the oil.82857958

BERNHARD HARMS. Die Holländischen Arbeitskam= mern. Ihre Entstehung, Organisation und Wirksamkeit. Tubingen u. Leipzig 1903. J. C. B. Mohr (Poul Siebeck). (198 S., Rmk. 5.00).

Real samples were used for PLS model calibration and validation steps, showing that this approach can be of value in preventing deviations in the results caused by the matrix effects for the simultaneous spectrophotometric determination of aluminum and iron in plant extracts. One hundred UV-vis spectra. obtained from sample, of the 1997 to 2000 International Plant-Analytical Exchange (IPE) program (The Netherlands), were used for model development, with ICP-AES aluminum and iron determinations as reference values for model calculation. The plant extracts were analyzed both by ICP-AES and by the PLS models developed in this work, using calibrations with both aqueous standard solutions and with real sample extracts. In addition, since the use of smaller calibration sets could be of value in reducing both the cost and the time of analysis, sets with fewer calibration samples were also investigated, with the help of the Kennard and Stone algorithm for sample selection. Comparison of the predictability of the best model obtained with each calibration set was made using the ratio of their relative root mean square error (%RMSEV) for samples in the validation set, for aluminum or iron determinations, and were compared against F-test tabulated values. For all the models developed with real samples, the differences in the %RMSEV values for the aluminum or iron determinations were found not to be statistically significant, at a confidence level of 95%. Although it was observed that the aluminum, but not the iron. determinations with the PLS 2 model prepared with aqueous standards tend to be slightly lower than the ICP-AES determinations. this model has a good global prediction ability, as observed through the correlation curves presented, and can be used for screening determinations or for other agricultural purposes

Time-based injection approach for monosegmented continuous flow systems and related techniques

A time-based injection module for monosegmented continuous flow systems and related techniques, which uses three independently controlled solenoid valves, is described. A timer circuit employing three I.C. 555s and three TIP-121 transistors was constructed to control the injection module valves. The injection device was tested with non-reacting chemical systems (for example with a spectrophotometric standard and calcium flame emission) and with reacting conditions (for example the determination of Cr(VI), using diphenylcarbazide as colour reagent, and acid-base titration). The performance of this injection module demonstrates its suitability for everyday use.18619920

Modeling a new fixed-time batch approach for Mo(VI) determination

A fixed-time batch approach for molybdenum determination using iodide oxidation by hydrogen peroxide is presented. The iodine formed was extracted in situ with chloroform, and the absorbance readings were performed at 510 nm. This extraction procedure allowed us to 'freeze' the reaction at any preset time up to two hours, permitting a detailed investigation of the principal and interaction effects among the variables Mo(VI), H2SO4, H2O2, and KI, for the noncatalyzed and the Mo-catalyzed reactions. Response surface methodology was employed to model this chemical system and to find its optimized conditions, resulting in a 12-fold increase in method sensitivity. A reference material (Mussel) from the National Institute for Environmental Studies (NIES, Japan), run under the proposed conditions, gave results in good agreement with the reference value reported for molybdenum.40594795

The pan-beating stability of an expeller expressed soybean oil

The relative stability of an expeller expressed, physically refined soybean oil (EE-SBO, iodine value = 126.6) was compared to a low-linolenic acid soybean oil (LL-SBO, iodine value = 120.9) using pan frying. Physicochemical analyses, including free fatty acid analysis, the dielectric constant (Food Oil Sensor), and the Lovibond color were completed. High performance size exclusion chromatography was used to quantify the amount of polymeric triacylglycerol formed in the oil samples during heating. Oil samples were heated as thin films on a teflon-coated frying pan at similar to180C to a target endpoint of greater than or equal to 20% polymer. ne endpoint, as determined by high performance size exclusion chromatography, was reached after 10 min of heating for the EE-SBO (23.8% polymer) and 12 min for the LL-SBO (24.9% polymer) sample. Although the iodine value suggests that LL-SBO should have an oxidative stability comparable to EE-SBO, the results from the physicochemical analyses indicated that the EE-SBO was approximately 20% more stable than the LL-SBO.111576

Elimination of iron interference in the molecular spectrophotometric determination of aluminum in soil extracts using artificial neural networks

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)An artificial neural network (ANN) calibration model was developed to determine aluminum in the presence of iron in soil extracts, using xylenol orange as chromogenic reagent. The spectral data of synthetic mixtures of Al3+ and Fe3+ as well as of the soil extracts, were recorded in the range between 410 and 580 nm. Method validation was carried out using 18 soil extracts. The results gave good linear correlations between the ANN model and the ICP OES measurements for both species.24911471150Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq