In biochemistry and diagnostic reagent formulation, the choice of buffer directly affects the pH stability of the system. CAPS (3-cyclohexylamino-1-propanesulfonic acid) is a biological buffer suitable for high pH ranges. Its physicochemical properties and buffering characteristics give it certain advantages in applications such as electrophoresis, cell culture, and diagnostic reagents.
Basic molecular information and morphological characteristics
The chemical name of CAPS is 3-(cyclohexylamino)-1-propanesulfonic acid, with a CAS number of 1135-40-6, a molecular formula of C₉H₁₉NO₃S, and a molecular weight of 221.3 grams per mole. From the appearance, CAPS is a high-purity white crystalline powder, odorless and tasteless, with a characteristic of easy moisture absorption. Therefore, it needs to be kept moisture-proof during storage and weighing. These physical properties determine its operational requirements under conventional laboratory conditions - dry environment, sealed storage, and timely use after opening.
Key quality indicators
The quality control of CAPS products primarily revolves around several core indicators: purity, moisture content, solubility, and heavy metal residue. The purity level must not be lower than 99.0%, which is determined using titration. The loss on drying should not exceed 0.5%, measured after drying at 105 degrees Celsius for 3 hours, reflecting the level of moisture control in the product. In terms of solubility, CAPS is easily soluble in water. When prepared into an aqueous solution of 0.5 mol/L, it appears colorless, clear, and transparent, indicating that the product has good solubility in aqueous systems and can dissolve quickly in conventional buffer preparation without requiring special dissolution aids. The residue on ignition is controlled below 0.1%, and the heavy metal content does not exceed 10 ppm.
Characteristics of buffer system
The buffering properties of CAPS are determined by its molecular structure. The pH value of its 1% aqueous solution ranges from 5.0 to 6.5, indicating that free CAPS is weakly acidic in water. The pKa value of CAPS at 25 degrees Celsius is 10.4, which is a key parameter reflecting its buffering characteristics. pKa determines the effective working range of the buffer. CAPS has good buffering capacity between pH 9.7 and 11.1, belonging to an alkaline buffering system, which is suitable for experiments or production scenarios that require maintaining the stability of the solution environment under high pH conditions.
Compared to the commonly used Tris buffer (effective range pH 7.0 to 9.0) and HEPES buffer (effective range pH 6.8 to 8.2), CAPS covers a higher pH range. This characteristic makes CAPS irreplaceable in applications where alkaline reaction conditions or high pH environments are required to maintain the stability of biomolecules.
Application advantages and limitations
CAPS exhibits excellent buffering capacity at high pH values and has no chelating effect on metal ions. This means that in reaction systems involving metal ions as cofactors, CAPS will not chelate and consume these essential ions, avoiding indirect inhibition of metal-dependent enzyme activity. This characteristic may have reference value in the study of metalloproteins and the formulation of diagnostic reagents containing metal ions.
CAPS is suitable for electrophoresis experiments, especially for operations that require alkaline buffering conditions such as protein transfer. In cell culture, CAPS can be used in specific culture systems that require maintaining a higher pH environment. In the preparation of diagnostic reagents, CAPS provides buffering support for reaction systems that exhibit better stability under alkaline conditions.
The CAPS products manufactured by Hubei XinDesheng Material Technology Co., Ltd. have a purity of no less than 99.0% and a heavy metal content controlled below 10ppm. They are suitable for biological buffering scenarios under high pH conditions and can meet the quality requirements for buffers in related experiments and production. If you have any recent purchasing needs, please visit our official website for more details or contact me!
