Tokyo : Tanaka Holdings Co., Ltd. (a company of Tanaka Precious Metals) today announced that the TKG Laboratory Center of Tanaka Kikinzoku Kogyo K.K., which operates the Tanaka Precious Metals’ manufacturing business became the first company in Japan to acquire ISO/IEC17025:2005(*1) accreditation for silver analysis technology.

First to obtain accreditation in Japan after succeed in improving analysis accuracy

The ISO/IEC17025:2005 accreditation recognizes that Tanaka Kikinzoku Kogyo’s analysis technology is compliant with international standards on repeatability of analytical results concerning the quantitative analysis of 37 elements(*2) including 23 significant elements that should be analyzed as trace elements in silver and this is the first time this kind of accreditation has been awarded in Japan. Upon certification, from January 2011, Tanaka Kikinzoku Kogyo has continued working on the optimization of silver analysis techniques. Through these efforts, the Company sought to correct solubility conditions of silver analysis samples while confirming the validity of the analysis method, and the improvement in accuracy of analysis made it possible to obtain ISO/IEC17025:2005 accreditation.

ISO/IEC 17025 is an international standard that defines the general requirements concerning the ability to perform testing and calibration, and it requires not only the operation of management systems such as those specified in ISO9001, but also strict analytical ability. This accreditation enables the users of manufacturing various industrial silver products to establish an ever more reliable analysis infrastructure for silver.

The rise in precious metal prices in recent years has led to silver being extracted not only from mines but also recycled items, making the development and establishment of more accurate and rapid analysis methods a pressing issue. Currently, silver is used in a wide range of products in industrial fields, such as bonding material, contact material, solar cell electrodes and sputtering targets. In particular, bonding material made of high-purity silver is used in advanced industrial products such as power devices, power LEDs (light emitting diodes) and MEMS (microelectromechanical systems), for which markets are beginning to expand on a large scale. It has been confirmed that the function of such products is affected if they contain even trace amounts of certain elements, and both customer demand and market requirements for silver analysis are increasing.

Obstacles to silver analysis

To dissolve silver for analysis, nitric acid is used instead of aqua regia(*3), which is generally used for dissolving other precious metals. This is because dissolving silver in aqua regia produces silver chloride which may hinder the operation for determining the grade of silver. However, if silver which contains gold as a trace element, for instance, is dissolved in nitric acid, gold remains undissolved, thus making the analysis of silver more difficult than other precious metals.

That is why in recent years Tanaka Kikinzoku Kogyo has been using a method that establishes the purity of silver through the subtraction method by assessing, via an ICP Optical Emission Spectrometer(*4), a solution in which silver is dissolved with nitric acid and another solution in which indissoluble elements with nitric acid are dissolved using a mixture of hydrochloric acid and nitric acid. However, the problem with this method was that errors may increase when the concentration of impurities is low. Further improvement in analysis technology to define the content of every element was necessary.

Tanaka Kikinzoku Kogyo has worked on the optimization of silver analysis technology to resolve such issues. Through these approaches, the Company was able to improve the accuracy of silver analysis when there are low concentrations of impurities by investigating the pretreatment conditions and ICP Optical Emission Spectrometer measurement conditions, leading to ISO/IEC17025:2005 accreditation for the entire analysis process including the method of dissolving silver. In this connection, by exchanging opinions with an incorporated administrative agency Japan Mint Bureau the Company was able to extend its knowledge of silver analysis methods.

By obtaining the accreditation, Tanaka Kikinzoku Kogyo has achieved an important goal in the analysis of precious metals, acquiring ISO/IEC17025:2005 accreditation for analysis technology for gold which has particularly high turnover among precious metals, platinum, palladium and silver. The Company will continue to strive for quality improvement to realize the world standard for analysis technology and quality assurance of these precious metals in the future.