Calcium Gluconate Monohydrate: Properties, Uses & Lab Guide

Calcium Gluconate Monohydrate is a water-soluble calcium salt of gluconic acid widely used in biochemical research, cell biology, and physiological studies as a biocompatible, readily ionizable source of divalent calcium ions.

Chemical Name

Calcium gluconate monohydrate

Molecular Formula

C₁₂H₂₂CaO₁₄·H₂O

Molecular Weight

448.39 g/mol

CAS Number

66905-23-5

Appearance

White crystalline powder

Solubility

Soluble in water; slightly soluble in ethanol

Storage Condition

Room temperature, dry, away from light

Chemical Identity and Physical Properties

Calcium Gluconate Monohydrate (CAS 66905-23-5) is the monohydrated calcium salt of gluconic acid, a naturally occurring sugar acid derived from glucose. Its molecular formula is C₁₂H₂₂CaO₁₄·H₂O with a molecular weight of approximately 448.39 g/mol. The compound appears as a white, odourless, crystalline powder that is stable under standard laboratory conditions.

The compound is freely soluble in hot water and moderately soluble in cold water, making it straightforward to prepare aqueous stock solutions for biological experiments. It is only sparingly soluble in anhydrous ethanol and essentially insoluble in most organic solvents. Aqueous solutions are mildly acidic to near-neutral in pH, which is compatible with many physiological buffer systems. The monohydrate form is the most commonly supplied pharmaceutical and research grade, offering consistent stoichiometry relative to the anhydrous form.

Biochemical Role of Calcium and Gluconate

Calcium ions (Ca²⁺) are essential second messengers and structural cofactors in virtually all eukaryotic cells. They regulate a diverse range of processes including muscle contraction, neuronal excitability, exocytosis, enzyme activation, and gene transcription. Calcium Gluconate Monohydrate serves as a biocompatible, non-toxic vehicle to deliver Ca²⁺ in experimental settings where precise ionic concentrations must be controlled.

The gluconate anion is metabolically inert under most experimental conditions and does not participate significantly in the major metabolic pathways being studied, making it an ideal counterion for calcium delivery compared to chloride or phosphate salts in contexts where those anions may confound results. Gluconate is also well-tolerated in cell culture media and does not precipitate with common buffer components such as phosphate at physiological concentrations, provided concentrations are kept within reasonable ranges.

Laboratory Applications

Calcium Gluconate Monohydrate finds broad application across multiple research disciplines:

• Cell culture and physiology: Used to supplement calcium in defined or low-calcium culture media, enabling the study of calcium-dependent cell adhesion, signalling cascades, and differentiation. It is also used in reconstituted extracellular fluid formulations.
• Enzyme activity assays: Many enzymes—including proteases, lipases, and kinases—require Ca²⁺ as a cofactor. Calcium Gluconate Monohydrate provides a clean calcium source for enzyme kinetics studies without interfering anions.
• Electrophysiology buffers: Incorporated into artificial cerebrospinal fluid (aCSF) and bath solutions for patch-clamp and field-potential recordings where the gluconate anion can replace chloride to reduce chloride-mediated artefacts.
• Biomaterial and hydrogel research: Used to cross-link alginate and other polyanion hydrogels by providing a controlled source of divalent cations for materials science and tissue-engineering experiments.
• Nutritional and pharmaceutical research: Serves as a reference standard or active ingredient in bioavailability and absorption studies involving calcium supplementation formulations.

Preparation and Handling Guidelines

Solution preparation: To prepare a 1 M stock solution, dissolve 448.39 g of Calcium Gluconate Monohydrate in approximately 800 mL of warm deionized water with gentle stirring, then adjust the final volume to 1 L. For most cell-biology applications, working concentrations range from 1–10 mM. Filter sterilize through a 0.22 µm membrane if the solution is intended for cell culture use; autoclaving is not recommended as it may reduce solubility.

Storage: The solid should be stored at room temperature in a tightly sealed container away from moisture and direct light. Aqueous solutions are stable at 4 °C for several weeks but should be inspected for particulate matter or turbidity before use. Discard solutions showing any signs of precipitation.

Safety: Calcium Gluconate Monohydrate has a low acute toxicity profile and is generally recognized as safe (GRAS) for handling in standard research laboratories. Standard personal protective equipment (lab coat, gloves, eye protection) is recommended as per good laboratory practice. Consult the Safety Data Sheet (SDS) supplied with product SKU C110858 for comprehensive hazard information before use.

Purity, Grades, and Quality Considerations

For research applications, reagent-grade Calcium Gluconate Monohydrate with purity ≥98% (as determined by titration or HPLC) is typically sufficient for biochemical assays, cell culture, and enzyme studies. Higher purity grades may be required for pharmacological or analytical reference standard applications.

Key quality parameters to verify when sourcing include: assay purity (%), water content (Karl Fischer titration to confirm monohydrate stoichiometry), heavy metal content, and microbiological limits for cell-culture-grade material. Aladdin Scientific's product C110858 is supplied with a certificate of analysis (CoA) detailing these parameters. Researchers should request and review the CoA for each lot to ensure consistency across experiments, particularly in long-running studies where batch-to-batch variability could introduce systematic errors.

Frequently asked questions

What is the difference between Calcium Gluconate Monohydrate and anhydrous Calcium Gluconate?

Calcium Gluconate Monohydrate contains one molecule of water of crystallization per formula unit, giving it a molecular weight of approximately 448.39 g/mol, whereas the anhydrous form has a molecular weight of approximately 430.37 g/mol. When preparing solutions, the correct molecular weight must be used to achieve the target molar concentration. The monohydrate is the most commonly supplied research and pharmaceutical grade due to its greater stability under ambient humidity conditions.

Is Calcium Gluconate Monohydrate suitable for use in mammalian cell culture?

Yes, Calcium Gluconate Monohydrate is widely used to supplement calcium in cell culture systems. The gluconate anion is metabolically inert and well-tolerated by mammalian cells. Solutions should be filter-sterilized through a 0.22 µm membrane before addition to culture media, and the final calcium concentration should be adjusted to match the physiological range (typically 1–2 mM for most cell types) to avoid toxicity from excessive calcium.

Why use Calcium Gluconate instead of Calcium Chloride as a calcium source?

Calcium Chloride dissociates to release chloride ions (Cl⁻), which can interfere with certain assays, electrophysiological recordings, or ionic-strength calculations where chloride concentration must be controlled. The gluconate anion from Calcium Gluconate Monohydrate is largely biologically inert and does not participate in major metabolic pathways, making it preferable when chloride interference is a concern—for example, in patch-clamp intracellular solutions or low-chloride buffer systems.

How should I store Calcium Gluconate Monohydrate solutions long-term?

Aqueous solutions of Calcium Gluconate Monohydrate are best stored at 4 °C in sealed, sterile containers away from light. Under these conditions solutions are generally stable for several weeks. For longer-term storage, preparing aliquots and freezing at −20 °C is advisable; however, solubility should be verified upon thawing before use, as precipitation can occasionally occur. Always inspect solutions visually before use and discard any showing turbidity or particulate matter.

What concentration of Calcium Gluconate Monohydrate is typically used in artificial cerebrospinal fluid (aCSF)?

In many published aCSF formulations designed to minimize chloride, calcium gluconate is used to provide a free Ca²⁺ concentration of approximately 1.2–2.5 mM, mirroring physiological cerebrospinal fluid calcium levels. The exact concentration should be confirmed by reference to the specific aCSF recipe being used in your experimental protocol, as formulations vary between research groups and target brain regions.

References

1. Bhatt DL et al. General principles of calcium physiology and calcium gluconate use in clinical and research settings. Review article — details to be verified.
2. Ringer S. A further contribution regarding the influence of the different constituents of the blood on the contraction of the heart. J Physiol. 1883;4(1):29–42.
3. Hamill OP, Marty A, Neher E, Sakmann B, Sigworth FJ. Improved patch-clamp techniques for high-resolution current recording from cells and cell-free membrane patches. Pflugers Arch. 1981;391(2):85–100.
4. Rowley AT, Nagalla RR, Wang SW, Liu WF. Extracellular Matrix-Based Strategies for Immunomodulatory Biomaterials Engineering. Adv Healthc Mater. 2019. (Alginate crosslinking with divalent cations context — citation details to be verified.)

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