A GAS-CHROMATOGRAPHIC HEADS PACE METHOD FOR THE DETERMINATION OF ACETONE IN BOVINE MILK , BLOOD AND URINE
WINTERBACH, HANLIE E. K. & APPS , P . J. , 1991. A gas-chromatographic headspace method for the determination of acetone in bovine milk, blood and urine. Onderstepoort Journal of Veterinary Research, 58,75-79 (1991) An automated headspace gas-chromatographic method has been developed for the determination of acetone in the milk, blood and urine of dairy cows. Five me samples were saturated with 2 g of sodium chloride and equilibrated for 30 min at 90°C in a Hewlett-Packard HP 19395A automatic headspace sampler. The headspace volatiles were transferred without splitting to a 25 m x 0,3 mm x 0,4 11m Carbowax column in a Shirnadzu GC 9A gas chromatograph, operating isothermally at 50 °C. The coefficients of variation for the determination of acetone were 1,5-4,4 % for urine , 10,0-24 ,9 % for milk and 2,0-19,6 % for blood . The detection limits were 0,0055 mg/100 me for milk, 0,0072 mg/100 me for blood and 0,0080 mg/100 me for urine . The analysis time of 5 mm per sample provided an adequate rate of throughput for routine monitoring.
Micro method for determination of ketone bodies by head-space gas chromatography.
Abstract A method has been developed for the determination of ketone bodies. The principle is to transform acetoacetate and β-hydroxybutyrate to acetone, which is analyzed by means of head-space gas chromatography. Recoveries of acetoacetate and β-hydroxybutyrate were 101 and 86.1%, with standard deviations of 5–8 and 5–9%, respectively. With this method, concentrations from 1 μM could be measured accurately, which is particularly convenient for biological analyses. If samples of acetoacetate and β-hydroxybutyrate are to be stored, the transformation of the respective substances to acetone should be carried out on the day of sampling. The acetone samples should be alkalized to prevent decarboxylation of acetoacetate.
The role of white cells and frequency of milking in the control of staphylococcal mastitis.
Abstract It is suggested that the incidence of subclinical and clinical staphylococcal mastitis can be reduced by milking dairy cows three times a day at eight-hour intervals. This conclusion derives from experiments in which it was shown that the white cells suppressed the number of coagulase positive staphylococci in vitro in a milk culture in the early stages of incubation. In a herd milked twice a day at 9 and 15-hour intervals the bacterial count in udders was higher and clinical mastitis more common at the end of the long interval than at the end of the short interval.