【国外标准】 Standard Practice for Preparation of Solution of Solid, Pasty and Powdered Vegetable Tannin Extracts

4.1 The concentration of tannins in solid, pasty, and powdered extracts needs to be reduced to analytical strength for tannin analyses.4.2 Vegetable tannin extracts are heterogeneous mixtures of components with varying solubility.4.3 The solubility of such extracts is influenced by temperature and concentration, which affect the degree of dispersion and size of the component particles.4.4 Since extracts have greater solubility in hot water than cold, it is desirable to dissolve and disperse an extract in hot water and then let the solution cool slowly to standard room temperature.4.5 It is often difficult to reduce samples of solid and particularly pasty extracts to specimen size and at the same time ensure representative sampling. Therefore, caution is advised in drawing conclusions on the precision and bias of the results obtained on such extracts; where difficulties in sample preparation are experienced, little confidence can be placed in the results.1.1 This practice covers a standard procedure for use in preparing the analytical solution required for the analysis of solid, pasty, or powdered vegetable tannin extracts.1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.