Search

AUTOMATIC TITROMETRIC METHOD IN FLOW-BATCH CONTROLLED BY AN ARDUINO OPEN SOURCE HARDWARE. This work describes the development of an automatic titrometric method in flow-batch with potentiometric detection using alternative and easily accessible materials. Arduino board and its modules, solenoid valves to control the flow rate, peristaltic pump to propel and suction fluids and tubes of inert material to connect the different parts of the Flow-Batch Analyser (FBA) were used. The use of solenoid valves controlled by microcontrollers proved to be efficient for controlling the flow in FBA systems, the correlations of their flow rates as a function of time showed good linearity with correlation coefficients (r) 0.9994 and 0.9997 for the valve 1 and valve 2, respectively, allowing correct addition of pre-established volumes. Accuracy was verified by comparing the results of the proposed method with the classic potentiometric titration with statistically evaluated by Student’s t-test in NaOH with HCl and vinegar with NaOH titrations. Results confirmed the efficiency to use Arduino board and its modules and automatic titrometric method in flow-batch developed in this work allow the implementation of practical disciplines, such as potentiometric titration and flow analysis system in undergraduate courses, making these instruments more accessible, especially for the chemistry students.

A screening method for zinc levels in different milk samples (raw cow, raw sheep, UHT cow, UHT goat and soybean milk base) was performed to establish the Zn levels' differences in protein samples. The samples were digested in a cavity microwave oven and the total Zn levels in the extracts were determined by flame absorption atomic spectrometry (FAAS). The protein separation was performed by urea polyacrylamide gel electrophoresis (UREA-PAGE). Protein bands were digested in the cavity microwave oven and Zn-protein analysis was further conducted by electrothermal atomic absorption spectrometry (ETAAS). The results showed that Zn is mainly bound to 32 kDa (b-casein) protein (17.0 ± 2.0%) in UHT cow and 24 kDa (a-casein) protein (9.0 ± 0.6%) in raw sheep milk. This method provided quantitative information regarding Zn species present in the protein fractions of the milk samples. The accuracy was evaluated using certified reference material (whole milk powder, NIST 8435) with statistically equivalent concentrations (Student's t-test) for total Zn and by addition and recovery experiments applied to measure Zn-protein. The recovered values were in the 92-110% range. Made available in DSpace on 2021-07-01T19:00:51Z (GMT). No. of bitstreams: 1 ZincFractionationCow.pdf: 300396 bytes, checksum: 9c0d5f6e765b2c9996705ff2bb985a87 (MD5) Previous issue date: 2021

A flow injection system was proposed to evaluate the transient product of a colorimetric reaction between hydrolysable tannin and potassium iodate (KIO 3 ) solution. The system optimization was accomplished by using statistical methods based on experimental design. Flow rate of KIO 3 solution, sample volume, carrier flow rate, and reaction coil were the selected factors for evaluation. On screening step, complete factorial 2 4 was used and two levels for each selected factor were studied. For the optimization phase, a centered face composite design 2 2 + star was employed to evaluate sample volume and flow rate of KIO 3 solution, which were the factors identified in the screening phase as having more influence on the absorbance signal. After optimization, the proposed system was compared with batch determination. Some characteristics, such as analytical frequency, reagent consumption and chemical residues generation presented better results by the use of the proposed system if compared with batch method. The system presented good repeatability with standard deviation lower than 3%, for n = 10, linearity ( R 2 = 0.9974) for tannic acid standard, analytical frequency of 15 injections h − 1 and limit of quantification of 24 mg L − 1 of tannic acid. Good results were obtained when the proposed system was applied to hydrolysable tannin determination in Stryphnodendron barbatimao , Eucalyptus citriodora and Phyllanthus niruri , samples of plants commonly used in popular medicine.

The main challenge of Embrapa is to develop a model of genuine Brazilian tropical agriculture and livestock. To get this task, the quality of laboratories results is mandatory, increasing the demand for reference materials. Projects were proposed to produce reference materials to support the national agriculture laboratories and consolidate a network able to perform reliable and reproducible analytical testing laboratory within the internationally standards required. Reference materials were produced and available to interested laboratories and collaborative tests were conducted to obtain consensus values. The results and statistical evaluations were performed with the use of software developed by Embrapa Pecuaria Sudeste.