Colloidal gold 1000 ppm: Definition, concentration, production and storage

Colloidal gold is the subject of numerous materials science, physical, and laboratory chemical investigations. Anyone studying the properties of highly concentrated precious metal dispersions will encounter parameters such as particle size , purity , ppm concentration , and manufacturing process . This article explains the chemical and physical principles of colloidal gold at 1000 ppm, as well as the quality criteria for its production and storage.

1. Definition: What is colloidal gold and what does “1000 ppm” mean?

Physical-chemical fundamentals

Colloidal gold (also referred to as gold sol in the literature) is a dispersed system in which microscopically small, elemental gold particles (nanoparticles) are distributed in highly purified, demineralized water.

• Dispersion instead of a true solution: Unlike ionic gold salts (such as gold chloride), the gold atoms in the colloid are not chemically dissolved. They are solid, metallic microparticles suspended in the dispersion medium of water.
• Particle size and zeta potential: In high-quality dispersions, the individual gold clusters have a diameter of just a few nanometers (usually between 1 and 20 nm). Due to their identical electrical surface charge (measurable via the so-called zeta potential ), the nanoparticles repel each other. In conjunction with Brownian motion, this prevents the particles from settling (sedimenting) despite the high density of gold.
• Optical properties (surface plasmon resonance): Depending on particle size and density, genuine colloidal gold does not appear metallic yellow, but rather exhibits a ruby-red to deep violet color . This phenomenon arises from surface plasmon resonance , in which the free electrons on the surface of the gold nanoparticles interact with the incident visible light. The scattered light cone of the suspended particles can be visualized using a laser beam ( Tyndall effect ).

What does the concentration value “1000 ppm” mean?

The unit of measurement ppm stands for “parts per million” and denotes the mass ratio between the dispersed precious metal and the carrier liquid:

• 1 ppm corresponds exactly to 1 milligram (mg) of gold per 1 kilogram (approx. 1 liter) of water .
• 1000 ppm therefore means that 1,000 milligrams (exactly 1 gram) of pure fine gold are dispersed in one liter of ultrapure water (0.1 mass percent).

Technical feature of 1000 ppm:

While conventional gold colloids often have concentrations between 1 and 50 ppm, 1000 ppm represents a high concentration . Because the average distance between the nanoparticles is extremely small at such a high particle density, the demands on the manufacturing process increase considerably: only a precisely controlled charge distribution and extremely small particle sizes will ensure that the dispersion remains stable, preventing the particles from agglomerating (clumping together) and settling at the bottom of the container.

2. Production: High-voltage electrolysis and purity criteria

The physical stability of colloidal gold depends significantly on the chosen production method and the purity of the starting materials.

The high-voltage plasma process (physical manufacturing)

Because gold, as a precious metal, is extremely unreactive, it can hardly be removed by simple low-voltage electrolysis in pure water. Therefore, modern laboratory and process engineering uses high-voltage electrolysis or arc electrolysis (according to Georg Bredig) :

1. Use of fine gold electrodes: Two electrodes made of certified fine gold are placed in a container with ultrapure water.
2. High-voltage discharge: Precisely controlled high-voltage pulses generate a microscopic plasma field underwater between the electrodes.
3. Thermoelectric atomization: Due to the high energy density in the arc, minute amounts of gold evaporate on the electrode surface and condense immediately in the cool ultrapure water to form electrically charged nanoparticles.
4. Free from chemical additives: Unlike the chemical reduction method (according to Turkevich), in which golden acid is reacted using citrates or other reducing agents, the physical high-voltage process requires no stabilizers, salts, or chemical additives whatsoever . The end product consists of 100% pure water and elemental gold particles.

The 3 key purity requirements

To prevent contamination or premature discharge of the colloid, strict laboratory standards are applied during production:

• Fine gold purity of at least 99.99% (24 karat): The gold electrodes used must meet at least the “Four Nines Fine” (999.9) standard to prevent foreign metal ions (e.g., copper or silver) from entering the liquid.
• Ultrapure water (Type 1 / Aqua bidestillata): The carrier liquid is repeatedly distilled and deionized laboratory water with a minimal residual conductivity of < 0.1 µS/cm . If minerals or electrolytes were present in the water, they would disrupt the electrical charge shell of the gold particles and lead to immediate flocculation.
• Inert container materials: Production takes place exclusively in non-reactive laboratory vessels (e.g., made of borosilicate glass) to prevent the leaching of foreign substances from the container.

3. Proper storage and shelf life

Since colloidal gold is a physically sensitive charge system, external factors influence the stability of the dispersion:

• Light protection (violet glass / amber glass): UV radiation and direct sunlight can disrupt the electrical charge balance of the nanoparticles. High-quality colloids are therefore stored in Miron violet glass or opaque amber glass.
• Constant room temperature: Storage should be in a cool, dry place at a constant room temperature (ideally between 15°C and 22°C ). Refrigeration or freezing should be avoided, as strong temperature fluctuations slow down Brownian motion and promote clumping of the particles.
• Distance from electromagnetic fields: The container should not be stored in the immediate vicinity of strong magnetic fields or sources of electronic radiation (e.g., Wi-Fi routers, microwaves, power supplies or loudspeakers) in order to preserve the zeta potential of the colloids.
• Avoiding contamination: When opening the bottle, the liquid must not come into contact with metals, organic substances or tap water, as even the smallest electrolyte contamination can impair the stability of 1000 ppm concentrates.

4. Legal Notice & Classification

Colloidal gold is a technical or laboratory chemical raw material and research product. According to current European Union regulations (in particular the Novel Food Regulation (EU) 2015/2283 ), colloidal gold is not approved as a food or food supplement . Its sale and supply are exclusively for technical, scientific, analytical, or further processing purposes as laboratory equipment.