Determination of ascorbic acid in pharmaceutical dosage forms and urine by means of an oscillatory reaction system using the pulse perturbation technique
A simple and reliable method for the determination of ascorbic acid (AA) is proposed and validated. It is based on potentiometric monitoring of the concentration perturbations of an oscillatory reaction system in a stable nonequilibrium stationary state close to the bifurcation point. The response of the Bray–Liebhafsky (BL) oscillatory reaction as a matrix, to the perturbation by different concentrations of AA, is followed by a Pt electrode. The linear relationship between maximal potential shift and the logarithm of the amount of AA is obtained between 0.01 and 1.0 μmol. The sensitivity of the proposed method (as the limit of detection) is 0.009 μmol and the method has excellent sample throughput (30 samples per hour). The procedure was used for AA determination in pharmaceutical formulations and urine. The results are in agreement with those obtained using the official method. Some aspects of the possible mechanism of AA action on the BL oscillating chemical system are discussed.
Analitičke primene oscilatornih hemijskih reakcija: određivanje nekih
Izvod U poslednjih dvadesetak godina razvijene su brojne analitičke primene oscilatornih hemijskih reakcija realizovanih u otvorenom reaktoru. Predložene kinetičke metode se zasnivaju na sposobnosti analiziranih supstancija da menjaju kinetičke parametre hemijskih reakcija, pri čemu eksperimentalno dobijeni signal odražava reakcionu brzinu koja zavisi od koncentracije ispitivanog analita. Razvoju ovih metoda poklanja se sve veća pažnja zbog jednostavne eksperimentalne procedure, velikog linearnog opsega regresione jednačine (10−10 mol L) i niskog limita detekcije (10−10 mol L, u nekim slučajevima, ≤ 10 mol L), a njihovo korišćenje je vrlo pogodno za rutinske analize različitih neorganskih i organskih jedinjenja, kao i gasova. Ovaj rad ima za cilj da dâ kratki pregled primene takozvane pulsne perturbacione tehnike za kvantitativna određivanja nekih farmaceutski i biološki važnih jedinjenja u periodu od druge polovine 2005. godine do prve polovine 2011. godine.
Genotypic diversity in field isolates of Babesia bovis from cattle with babesiosis after vaccination.
OBJECTIVE
To determine whether particular genotypes of Babesia bovis were common to field isolates obtained from cattle properties in Queensland where the B bovis vaccine had apparently failed.


DESIGN
A comparative study of polymerase chain reaction genotypes in different populations of B bovis.


PROCEDURE
Two polymerase chain reaction assays were applied to analyse DNA extracts of B bovis vaccine (K, T and Dixie strains) and 27 field isolates from 24 properties where disease outbreaks had occurred despite the use of the vaccine. To evaluate the stability of the genotypes identified, 11 of the field isolates were inoculated into experimental cattle that had either been previously vaccinated with T strain or not vaccinated.


RESULTS
No particular genotype of B bovis was responsible for the problems observed in previously vaccinated herds. None of the isolates had genotypes identical to the vaccine strains used. No geographic trends among the genotypes were observed. Isolates that originated from the same property also had different genotypes. Blood passage of the 11 field isolates in either previously vaccinated or nonvaccinated cattle did not alter the original genotype.


CONCLUSION
No particular genotypes identified by the Bv80 and BvVA1 polymerase chain reaction assays could be associated with vaccine failures.