[Validation Study on the Developed Method for Cyanide in Various Mineral Waters].

Area of Science:

• Environmental Chemistry
• Analytical Chemistry

Background:

• Mineral waters (MWs) present unique challenges for cyanide analysis due to variations in hardness and carbonation.
• Existing official methods for tap water cyanide analysis may not be suitable for MWs, failing validation criteria in Japan.
• Pretreatment pH adjustment to approximately 2.4, crucial for accurate cyanide determination, is often unachievable in certain MWs.

Purpose of the Study:

• To develop and validate a reliable method for determining cyanide ion and cyanogen chloride in diverse mineral waters.
• To address the limitations of existing methods in accurately analyzing cyanide in mineral water matrices.

Main Methods:

• A method was developed and validated for the simultaneous determination of cyanide ion and cyanogen chloride.
• A five-fold dilution step using a phosphate buffer was introduced during sample pretreatment to achieve the target pH of 2.4.
• Validation was performed according to established guidelines, assessing trueness and precision (RSD).

Main Results:

• The developed method demonstrated improved trueness, ranging from 93.0% to 103.8%, after incorporating the dilution step.
• Repeatability and within-laboratory reproducibility (RSD) were below 3.83% and 4.68%, respectively, meeting validation criteria for both analytes.
• The method successfully achieved the target pH of 2.4 in previously problematic MW samples.

Conclusions:

• The developed method, including a phosphate buffer dilution step, enables accurate determination of cyanide ion and cyanogen chloride in various mineral waters.
• This approach overcomes pretreatment pH adjustment challenges, ensuring reliable analytical results for mineral water quality assessment.
• The validated method shows applicability for routine analysis of these cyanide species in commercial mineral water products.