SOLVENTES EUTÉTICOS NATURAIS PROFUNDOS (NADES) NO PREPARO DE AMOSTRAS DE ROCHA FOSFÁTICA E SUPLEMENTO MINERAL PARA DETERMINAÇÃO ELEMENTAR POR TÉCNICAS DE PLASMA

NATURAL DEEP EUTECTIC SOLVENTS (NADES) IN SAMPLE PREPARATION OF PHOSPHATE ROCK AND MINERAL SUPPLEMENT FOR ELEMENTARY DETERMINATION BY PLASMA-BASED TECHNIQUES. Natural deep eutectic solvents (NADES) based on xylitol, citric acid, and malic acid were synthesized and used in ultrasound-assisted extraction (UAE) and heating-bath extraction of phosphate rock and mineral supplement samples. Arsenic, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, P and Zn were determined by inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry (ICP OES). The results showed the NADES as promising solvents for extraction of inorganic matrices compared to reference values and concentrations obtained using microwave-assisted acid digestion (MW-AD). Significant differences were observed for some elements, suggesting different chemical interactions between the synthesized NADES and each monitored element. For analytes extraction of phosphate rock, UAE presented the best results for As, Cr and P. Zinc was extracted with UAE and heating bath. Concerning mineral supplement, no significant differences were observed for Ca (UAE), Cd (UAE and heating bath), K (UAE and heating bath), Mn (UAE and heating bath), Na (UAE and heating bath), and P (UAE and heating bath). The NADES is a greener and a potentially alternative for the sample preparation compared to the official methods of analysis, can being used as selective extractor solvent in conventional sample preparation methods.

UPGRADE OF THE LANGENDORFF APPARATUS USING THE INFRARED THERMO-CONTROL SYSTEM AND AN INTELLIGENT HEATER

Biological experiments involving isolated organs and tissues demand precise temperature monitoring and regulation. An automatic temperature control system was proposed and optimised on real isolated swine hearts and the prototype is described in this work. The traditional Langendorff apparatus consists of a heart holder, a reservoir of perfusion solution flowing to aortic cannula and a heating bath allowing passive heat transfer to the reservoir of perfusion solution. The commercial infrared camera FLIR T62101 was added to this basic set-up and used for very precise monitoring of the temperature kinetic of the organ and connected with an electronic feedback loop, which allowed real-time and precise regulation of heat transfer from the heating bath to the perfusion solution and in turn indirectly to the heart tissue. This provides real time control and active regulation of the myocardial tissue temperature. The infrared camera was tested in several modes and several variants of detection were optimised for ideal measurement of the region of interest of the ex vivo organ. The kinetics of the temperature changes and temperature stability of the tissue were recorded and calibrated by external electronic thermometers (type Pt100, inserted in tissue). The time lapse from the hang-up of the hypo termed organ (30 °C) until optimal warming (37 °C) was less than eight minutes in the final instrument prototype. The final stability of the 37 °C tissue temperature was approved; the temperature fluctuation of left ventricle tissue was characterised as 36.8 ± 0.5 °C. This upgraded traditional instrument could be used in specific preclinical and clinical transplantation and analytical projects in future.

A Technique to Measure Firmness in Potato Tissue during Frying

The suitability of a cylinder fabricated from stainless steel was investigated for measuring the textural changes in potato during frying. The cylinder was attached to a TA.XT2 texture analyzer. A circulating heating bath was suitably connected to the cylinder. Initially, sunflower oil in the heating bath was brought to 180 'C without allowing it to circulate into the cylinder. A cube of potato tissue was positioned at the center of the cylinder with the help of a metal plate. The metal plate also allowed a thermocouple to be inserted into a potato cube to measure sample temperatures. The texture analyzer was then set to cause a continuous 20% strain. Heated sunflower oil from the bath was then circulated into the cylinder, thereby achieving complete immersion of potato tissue during force measurements. The circulating heated oil rapidly raised the tissue temperature from 20 'C to about 85 0C in 30 s, and, thereafter, a slow increase was observed. Firmness, expressed as the force required to cause 20% strain in the cube of potato tissue, slightly decreased during initial frying followed by a rapid decline. In separate hot-stage microscopy experiments, temperatures corresponding to swelling of starch granules and cell disruption were examined and compared with the firmness data. The stainless steel cylinder certainly allowed continuous circulation of heated oil and also kept the food sample in direct contact with oil during force measurements. This technique has limitations if absolute values of firmness are required. However, for zomparing texture profiles of different food samples during frying, the technique allows continuous measurements to be made.

Automated Method for Determining Direct Available P2O5 in Fertilizers

In the automated method for the analysis of direct available and total P205 in fertilizers, a heating bath is used to destroy ammonium citrate and colored material and for hydrolysis of non-orthophosphates. The heating bath was maintained at 98°C and contained a 40' time delay coil, providing 15 min digestion. Improvements on the method for the automated digestion of citrate extracts of fertilizer included decreasing the reagent and sample flow rates by factors of 2 to 5. All of the citrate in those samples containing the highest levels of citrate was not destroyed; however, the slight effect of the remaining citrate could be eliminated by changing the concentration of the molybdovanadate reagent. No difficulty was encountered with the hydrolysis of non-orthophosphates. With this analytical system, steady state conditions were reached at a sampling rate of 40 samples/hr and with a 4 : 1 sample-to-wash ratio. Repeated analyses were made on 9 samples, and the accuracy and precision of results obtained by the automated method compared very well with data by the official AOAC gravimetric method.

Manual Procedure for Direct Microassay of Serum Glucose by Use of o-Toluidine, and Its Adaptation to the SMA 12/60 AutoAnalyzer

A direct o-toluidine method for serum glucose is described as an alternative to the usual Cu—neocuproine method used with the Technicon SMA 12/60 AutoAnalyzer. Routine operation of the machine is simplified: the number of reagents and manifold lines is decreased and the dialyzer and pre-heating bath are eliminated. Deterioration of manifold tubing is minimized, while maintaining optimal machine sensitivity by adding borate and water to the reagent. Serum glucose was measured by the automated o-toluidine and Cu—neocuproine methods with similar, highly correlated results. Thus, the "normal limits" are unchanged and the same recorder graph paper may be used. A direct manual micro-method is also described, in which an anhydrous o-toluidine reagent is used. Results of manual and automated methods agree satisfactorily.

A Study of 2,4,6-Trinitrobenzenesulfonic Acid for Automated Amino Acid Chromatography

The reaction of 2,4,6-trinitrobenzenesulfonic acid (TNBS) with amino acids was investigated by a static system to develop optimum conditions for application to automated amino acid chromatography. TNBS was found to be a very simple and sensitive reagent, easier to use than ninhydrin. The reaction occurs quite rapidly at room temperature, eliminating the requirement of a heating bath. The major disadvantage is a much lower sensitivity to the imino acid proline than to the amino acids.

A Simplified Method for Automated Phosphorus Analysis of Serum and Urine

A simplified procedure utilizing ferrous ammonium sulfate-thiourea as the reductant for the determination of inorganic phosphate in serum and urine by the AutoAnalyzer is described. Elimination of the heating bath usually required for many phosphorus methods for color development yields an improved S.D. of ± 0.25 and facilitates troubleshooting during any apparatus malfunction. Comparison of results between the proposed method and that of Fiske and SubbaRow (1) is presented. Recoveries of added phosphorous in serum or urine are quantitative.

An Improved Automated Determination of Serum Total Cholesterol with a Single Color Reagent

An anhydrous color reagent containing ferric chloride is pumped through Tygon tubing to a glass coil in a 95° heating bath. Manually prepared serum extracts (1:20 isopropanol dilution) are presented to the stream of preheated color reagent, and the two are passed through three mixing coils, connected in series. The absorbance of the resultant color is determined at 550 mµ in a 15 mm. tubular flow-cell. The improved N-automated procedure gave values of greater precision (5.6%) for total cholesterol determined in replicate samples from sera pools than the N-automated procedure which lacked precision (27.7%). The values found in 60 individual serums are within 6.0% of total cholesterol values determined by the Abell et al. method.