X hits on this document

PDF document

DL-LACTONE CAS N°:79-50-5 - page 46 / 113





46 / 113



ID: 79-50-5 DATE: 18.01.2006

the test bottle was removed for titration; each of the remaining two absorbers was moved one position in the direction of the test bottle and a new CO2-absorber was placed at the far end of the series. Phenolphthalein (1% solution in ethanol, Merck KGaA, Germany) was used as pH-indicator. On the 28th day, the pH of the test suspensions was measured and 1 ml of concentrated HCl (37%, Merck KGaA, Germany) was added to each bottle. The bottles were aerated overnight to drive off CO2 present in the test suspension. The final titration was made on day 29. Theoretical CO2 production: The theoretical CO2 production was calculated from the molecular formula. Sampling and DOC analyses Test bottles: Samples were taken from the bottles containing the abiotic control, adsorption control (both containing sterilizing agent) and additional adsorption control (no sterilizing agent). Sampling procedure: A 30 ml sample of the test solutions was passed through a rough paper filter, and thereafter through a 0.45 µm filter. At least, the first 5 ml was discarded. Frequency of sampling: At the start of the test (0 h) and 3 h after addition of the test substance and on days 1, 7, 14, 16, 21, 28 and 29; in order to estimate any adsorption of dl-Lactone by the activated sludge and/or degradation of dl-Lactone. Furthermore TOC analyses were performed on the stock solution of dl-Lactone. DOC analyses: Analyses of the samples were performed using a Shimadzu TOC-VCPH total organic carbon analyzer combined with a Shimadzu ASI-V autosampler (Shimadzu.Benelux, The Netherlands). Measurements and recording pH: At the start of the test and on the 28th day. Temperature of medium: Continuously in a vessel with Milli-RO water in the same room.

Interpretation Degradation: Relative degradation values were calculated from the cumulative CO2 production relative to the total expected CO2 production based on the total carbon content of the amount of test material present in the test bottles. They were plotted versus time together with the relative degradation of the positive control. A figure of more than 10% degradation was considered as significant. Toxicity control: if less than 25% degradation (based on ThCO2) occurred within 14 days, the test substance was assumed to be inhibitory. The total CO2 evolution in the inoculum blank was determined by the cumulative difference (in ml of titrant) between the blank Ba(OH)2 traps and fresh Ba(OH)2.

Acceptability of the test 1. The positive control substance was degraded by at least 60% (67%) within 14 days. 2. The difference of duplicate values for %-degradation of dl-Lactone was always less than 20. 3. The total CO2 release in the blank at the end of the test exceeded 40 mg/l, but did not exceeded 70 mg/l (84 mg CO2 per 2 litres of medium, corresponding to 42 mg/l). Since all criteria for acceptability of the test were met the study was considered acceptable.



Document info
Document views372
Page views388
Page last viewedMon Jan 16 20:58:59 UTC 2017