The effect of pH on the uptake and toxicity of the bivalent weak base chloroquine tested on Salix viminalis and Daphnia magna

Abstract

The uptake and accumulation of most electrolytes will change with pH because of the different speciation states of these compounds at various pH. Non-ionized compounds will partition into fatty and organic phases (such as cell membranes) more readily than the corresponding charged compounds, and therefore a higher toxicity can be expected. The current study examines the pH-dependent toxicity and bioaccumulation of the bivalent weak base chloroquine (pK(a): 10.47 and 6.33, log K(OW) 4.67) tested on Salix viminalis (basket willow) and Daphnia magna (water flea). The transpiration rates of hydroponically grown willow cuttings were used to determine the toxicity of chloroquine at pH levels of 6, 7, 8, and 9. Root concentration factors were calculated from solution measurements. Results showed more than 10-fold higher toxicity and four to seven times higher root concentration factor at pH 9 than at pH 6. The toxicity of chloroquine was tested on Daphnia magna using the standard Organisation for Economic Co-operation and Development acute toxicity test modified to accommodate testing at pH levels of 7, 8, and 9. Increasing toxicity was seen at higher pH. The results of the current study confirm that the toxicity of weak bases with intermediate pK(a) values is higher at high pH levels.

Estimation of the toxicity of sulfadiazine to Daphnia magna using negligible depletion hollow-fiber liquid-phase microextraction independent of ambient pH

“…In the present study, because of the limits set by the pH tolerance and buffer sensitivity of D. magna and the use of only three pH levels, the correlations between the log-transformed acute toxicity (ln EC50/LC50) and pH could not be statistically analyzed. The pH-dependent aquatic toxicities of ionizable compounds have been of concern345610, because these values affect risk assessment. In addition to the acute toxicity, the same total concentration of zwitterionic tetracycline in ambient solution can evoke very different expressions of the antibiotic resistance gene in the exposed bacteria due to differential antibiotic uptake at different pH values20.…”

“…The toxicities of weak acids and weak bases to D. magna increase with an increasing neutral fraction45 and can be described by a toxicokinetic ion-trapping model338. Thus, in theory, HF-LPME can be used to estimate the toxicities of ionizable compounds.…”

“…The categories of chemicals that have a greater tendency to be ionizable include pharmaceuticals and some classes of pesticides12. The dependence on pH of the toxicity and bioconcentration of ionizable organic compounds to organisms has been observed in many studies3456. This dependence greatly influences the estimation of the toxicity and bioconcentration of ionizable organic compounds because the pH of natural waters fluctuates from 6 to 97.…”

Development and Validation of an Hilic–MS/MS Method by One-Step Precipitation for Chloroquine in Miniature Pig Plasma

“…Preparation of biological samples by LLE usually results in large injection volumes and needs relatively complicated and time-consuming pretreatment, including acidification [10,11] and basification [7,10,11], whereas SPE procedures require expensive SPE columns and longer analysis times [6][7][8][9]. Because of the high sensitivity of MS detection, a simpler and more convenient protein precipitation procedure successfully met the requirements of the present PK study [14].…”

Environmental Compatibility of Lightweight Aggregates from Mine Tailings and Industrial Byproducts

“…The TU value of the lightweight aggregate leachate was also significantly higher than the raw material leachate except for the leachate from the red mud. Rendal et al [38] showed that toxicity measured by Daphnia magna significantly increases at pH values above 8. Also, as shown in Table 3, in the lightweight aggregate leachate, a very high concentration of Ca was observed.…”