滴眼液中表面张力检测方案(接触角测量仪)

KRUSS Application Report Surface tension as a basic parameter for controlling drop dispensing ofophthalmic solutions Abstract Ophthalmic solutions and liquids (eye drops) are used to apply active pharmaceutical ingredients (API) directly to the eye.Surface tension measurement plays a key role for these solutions， as the surface tension is the only parametermanufacturers can control over a wide range that determines the droplet size. According to Tate， drop volume decreaseswith decreasing surface tension. The accessibility and significance of the surface tension makes it an important parameterfor quality control (QC) measurements. Figure 1： Dispensing drops of ophthalmic liquids Background Pharmaceutical drugs are most commonly applied to theeye in form of ophthalmic solutions (eye drops). Thevolume of the droplet determines the amount of activepharmaceutical ingredient (API) that reaches the eye. Inthis sense， controlling the volume becomes an importantaspect of the application of eye drops. Drop volumes of5 -15 pL have been proven to be most efficient for drugdelivery [1].There are two parameters that define the volume ofdrops being dosed： the condition of the nozzle withrespect to its material and design， and the surfacetension of the liquid. From the engineering point of view，the design of the nozzle and its surface properties arefrequently discussed. However， these are parameters themanufacturer of ophthalmiic solutions cannot control.The dosing containers are bulk commodity mainly madeof polypropylene. The inner and outer diameters of theorifice， as well as the surface properties of the containerwith regard to wettability， are predefined. In terms； ofphysico-chemicalproperties of)ftheophthalmic solution， the volume of the droplet mainlydepends on the surface tension. According to Tate， inthermodynamic equilibrium between the bulk and thesurface， the drop volume is directly proportional to theliquid's surfacetension[2]. This is a parametermanufacturers can influence by adding surface activeingredients and controlling the resulting effect withsurface tension measurements. Therefore， the liquid'ssurface tension is the parameter easiest accessible tooptimize the dispensing volume. Additionally， surface tension influences the break-uptime of tear films on the eyeball. This is importantbecause an elongated break-up time means a longer，more homogeneous exposition of the drug to theeyeball. It also enhances the comfort of the user whenapplying eye drops [3]. Therefore， the surface tension ofophthalmic liquids is an important parameter for qualitycontrol (QC) processes. Results In scientific literature， several studies investigating theinfluence of the surface tension of ophthalmic solutionson the volume of dispensed drops can be found [1， 4].We plotted results as adapted from published data byVan Santvliet and Ludwig and obtained alinearcorrelation between surface tension and drop weight fordispensed eye drops (figure 2). This is in good agreementwith Tate's description [2]. Figure 2： Drop weight of ophthalmic solutions as a functionof surface tension as adapted from data published by VanSantvliet and Ludwig [1， 4]. The coefficient of determinationRfor the linear reqression is 0.989. Summary Eye drops or ophthalmic solutions are widely used toapply drugs to the eye. The amount of drug is regulatedby the drop volume dosed. The main factor influencingthe dispensed drop volume of ophthalmic solutions istheir surface tension. We review results that show aproportional correlation between surface tension anddrop weight for ophthalmic solutions. This makes surfacetension measurements (by force tensiometer， dropvolume tensiometer or pendant drop measurements forsmall sample volumes) an attractive tool for qualitycontrol of eye drops and ophthalmic solutions. Literature ( [1] L . Van Santvliet， A. Ludwig， D ispensing eye drops TromT flexible plasti c dropper bottles part I ： Influence of the physico-chemical p r operties o f t h eformulation and the manipulation technique by the patient， Pharm. Ind. 1999，61， 194. ) [2] T. Tate， On the magnitude of a drop of liquidformed under different circumstances， Phil. Mag.S. 4 1864，27，176. [3] H. P. Dabrowski， A. Salpekar， O. W. Lever Jr. (Bausch& Lomb Inc.)， Ophthalmic solutions for artificialtears， U.S. Patent 5，895，645，1999. [4] L. Van Santvliet， A. Ludwig， Influence of the physic-chemical properties of ophthalmic viscolysers on theweight of drops dispensed from a flexible dropperbottle， Eur. J. Pharm. Sci.1999， 7，339. KRUSS GmbH|Borsteler Chaussee Hamburg| Germany|www.kruss.de|