Multiresidue Method of Analysis of Pesticides in Medical Cannabis.

Three related analytical methods were developed and validated for the determination of pesticides in cannabis leaves, dried cannabis flowers, and cannabis oil. The methods follow the generic sequence of an acetonitrile extraction, followed by solid-phase extraction cleanup and analysis by HPLC-tandem mass spectrometry (HPLC-MS/MS), GC-MS/MS, and GC-MS. These methods were developed to accommodate sample quantity and lipid content of the different matrices. Validation at a spiking level of 0.01 µg/g was successful for 39 pesticides in cannabis leaves and 40 pesticides in cannabis oil, and at 0.02 µg/g for 32 pesticides in cannabis flowers, with the majority of analytes showing recoveries within the acceptable range of 70-130%. With these methods established, unannounced inspections of Canadian licensed producers of cannabis revealed that out of 144 samples collected, 26 showed the presence of unauthorized pest control products.

Coupled mutual diffusion in solutions of micelles and solubilizates.

The coupled diffusion of micelles and solubilizates has been studied by measuring ternary mutual diffusion coefficients (D(ik)) for aqueous solutions of dodecylsulfobetaine (SB12) with added butanol, pentanol, or hexanol. SB12 micelles solubilize alcohols, so diffusing SB12(1) might be expected to co-transport alcohol(2). Negative values of cross-coefficient D(21) indicate, however, that the diffusion of SB12 drives substantial counterflows of alcohol. To help interpret the results, measured decreases in critical micelle concentrations with added alcohol (ROH) are used to evaluate equilibrium constants for the formation of (SB12)(m)(ROH)(n) mixed micelles. Increasing the concentration of SB12 along a diffusion path raises the concentrations of micelles and solubilized alcohol while lowering the concentration of free alcohol. The resulting flux of relatively mobile free alcohol molecules up SB12 concentration gradients is larger than the flux of solubilized alcohol down SB12 gradients, producing net countercurrent coupled fluxes of alcohol. The measured D(ik) coefficients are in close agreement (+/- 0.05 x 10(-5) cm(2) s(-1)) with predictions using self-diffusion coefficients (D(i)*) for SB12 and alcohol in solutions at thermodynamic equilibrium and the relations D(ik) = partial differential(C(i)D(i)*)/ partial differentialC(k) proposed recently for mutual diffusion in non-equilibrium solutions of associating solutes. Mutual diffusion coefficients for coupled surfactant-solubilizate diffusion are used to evaluate equilibrium constants for the formation of surfactant-solubilizate mixed micelles.