Transport properties of aqueous solutions of calcium lactate in the absence and presence of β-cyclodextrin

In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: Transport properties of aqueous solutions of calcium lactate in the absence and presence of β-cyclodextrin a b s t r a c t a r t i c l e i n f o Transport properties Diffusion Electrical conductivity Mutual diffusion coefficients and electrical conductivity of a well-known food additive and supplement, or excipient in pharmaceutical formulations, calcium lactate, have been measured in the absence and presence of β-cyclodextrin in aqueous solutions, at 298.15 K. The dependence of conductivity on concentration has been analysed using the Fuoss–Edelson method. The values of the Nernst diffusion coefficients, for binary solutions, derived from conductance and from diffusion experiments are in good agreement. The presence of β-cyclodextrin leads to a non-expected effect on the transport properties of the aqueous solutions of calcium lactate. These data have been justified with help of 1 H NMR spectroscopy. The effect on the water structure, reducing the hydration shell of lactate, is argued. This leads to an increase of the effective concentration of calcium lactate in solution contributing to an increase in the diffusion coefficients and a decrease in the dependence of the electrical conductance on the concentration. Calcium lactate (2-hydroxypropanoate), a salt used, e.g., as a baking powder [1] and found in foods [2,3] (such as, dairy products, red beans, rhubarb and broccoli), reveals a good solubility and bioavailability in comparison with other organic calcium salts, being one of the most important sources of calcium used in human diet, mainly due to its implication in orthopaedic health. Calcium lactate is used as a nutrient supplement in pharmaceutical formulations, applied to the management, treatment and prevention of calcium deficiency [4], that is, for individuals who do not receive sufficient calcium levels through their dietary intake. Being used in certain situations as a source of calcium ions (such as, in the preparation of calcium alginate microspheres for controlled-release delivery of active agents [5]), it is helpful in treating medical conditions, including tooth decay [6], weakened bones (known as rickets or osteomalacia) [7] and osteoporosis [8]. In addition, this organic calcium salt has also been introduced on the pharmaceutical market as tablet excipients (e.g. [9]). Cyclodextrins (CDs), cyclic oligosaccharides formed …