Preservation Guide for Reagents Used in Laboratory Heavy Metal Nickel Analyzers

The accuracy and reliability of measurements from heavy metal nickel analyzers heavily depend on the proper preservation of reagents. Incorrect storage can lead to reagent degradation, contamination, or changes in concentration, ultimately compromising test results. This guide outlines key principles for preserving common reagents used in nickel determination, typically via colorimetric or atomic absorption methods.

1. General Principles

Labeling: Clearly label all containers with the reagent name, concentration, preparation date, expiration date, and any specific hazards.

Contamination: Use clean, dedicated utensils and containers. Avoid metal contact. Seal containers immediately after use.

Temperature: Follow manufacturer instructions strictly. Most require storage in a cool, dark place. Refrigeration (4°C) is common for unstable reagents, but avoid freezing unless specified.

Light-Sensitive Reagents: Many organic complexing agents (e.g., dimethylglyoxime) are light-sensitive. Store in amber glass bottles or wrapped in aluminum foil.

2. Common Reagents & Specific Methods

Complexing/Spectrophotometric Reagents (e.g., Dimethylglyoxime Solution): This key reagent for colorimetric nickel analysis is prone to photodegradation and evaporation. Preservation: Store in a tightly sealed amber bottle at 4°C. Prepare in small volumes and monitor for discoloration or precipitation.

Strong Acids (Nitric, Hydrochloric Acid): Used for digestion and sample preservation. Preservation: Store in their original containers, made of acid-resistant material (e.g., polyethylene), in a dedicated acid cabinet away from organic solvents and bases. Ensure vents are functional.

Nickel Standard Solutions:

Stock Standard Solution (e.g., 1000 mg/L): Stable for up to one year when stored in a tightly sealed polyethylene or FEP bottle at 4°C. Acidification to 1-2% with high-purity nitric acid helps maintain stability.

Working Standard Solutions: Prepare by diluting the stock solution as needed. These are less stable and should be prepared weekly or even daily for the highest precision. Store at 4°C.

Reducing Agents (e.g., for Hydride Generation): Solutions like sodium borohydride are highly unstable in air and moisture. Preservation: Prepare fresh solutions daily if possible. Alternatively, store prepared alkaline solutions in sealed, dark bottles at 4°C for no more than a week. Keep solid reagent in a desiccator.

3. Summary

Establishing a systematic preservation protocol is essential for laboratory quality control. Always consult the specific analyzer's manual and reagent Safety Data Sheets (SDS) for the most authoritative instructions. Regular inspection of stored reagents for changes in color, clarity, or volume is a critical best practice. By ensuring reagent integrity, laboratories guarantee the precision and validity of their nickel analysis data.