Potassium phosphate monobasic (KH₂PO₄, CAS 7778 77 0) is a white crystalline, highly water-soluble inorganic salt used as a buffering agent, pH stabiliser, nutrient source, and analytical reagent across pharmaceutical, food, agricultural, and laboratory applications. Also known as potassium monophosphate or potassium dihydrogen orthophosphate monobasic, it is one of the most widely used phosphate salts in analytical chemistry and biochemistry. Lab Chemicals supplies this compound in the Merck EMPARTA® ACS grade manufactured and certified by Merck KGaA, Darmstadt, Germany in multiple pack sizes with Certificate of Analysis and pan-India delivery.
Potassium phosphate monobasic is the monobasic (monopotassium) salt of phosphoric acid. Its name reflects its composition: one potassium ion (K⁺) paired with the dihydrogen phosphate anion (H₂PO₄⁻). This makes it the most acidic of the three potassium phosphate salts — more so than dibasic (K₂HPO₄) and tribasic (K₃PO₄) and accounts for its acidic buffering action in the pH 4.5–7.0 range. In solution, it dissociates completely to give K⁺ and H₂PO₄⁻ ions, the latter of which acts as the buffering species.
Chemical formula: KH₂PO₄ | Molar mass: 136.09 g/mol | CAS: 7778-77-0
Potassium monophosphate comprises one potassium ion bonded to the dihydrogen phosphate group. The tetragonal crystal structure gives it a white, granular powder appearance. It is non-combustible and chemically stable under standard laboratory conditions. Procurement documentation and method SOPs referencing CAS 7778 77 0 or CAS 7778-77-0 are specifying this same compound.
All properties preserved from original content:
EMPARTA® is a registered trademark of Merck KGaA and designates a reagent grade specifically manufactured and certified for analytical use, meeting the specifications of the American Chemical Society (ACS) Reagent Chemicals standard. EMPARTA® ACS grade potassium phosphate monobasic (product code 1.93205) meets or exceeds ACS specifications for heavy metals (≤0.001%), iron (≤0.001%), chloride, nitrate, and insoluble matter the full analytical certificate is provided with each batch.
For laboratories operating under ISO 17025 accreditation, GMP conditions, or pharmacopoeial analytical methods (USP <791>, BP, EP), EMPARTA® ACS grade provides the documented purity and traceability required for method validation and regulatory submission. It also meets USP, EP, and BP monograph specifications for potassium dihydrogen phosphate, making it the appropriate grade for pharmaceutical buffer and excipient preparation.
Potassium dihydrogen orthophosphate monobasic is one of the most versatile analytical reagents in regular laboratory use. Its applications span five major industry sectors:
The primary analytical chemistry application of potassium phosphate monobasic is phosphate buffer preparation. Mixed with dibasic potassium phosphate (K₂HPO₄) or dibasic sodium phosphate in appropriate molar ratios, it produces phosphate buffer solutions across the pH 5.8–8.0 range one of the most commonly used buffer systems in biochemistry, cell culture, protein chemistry, and HPLC. In reversed-phase HPLC, potassium phosphate buffers are used as the aqueous component of mobile phases for the separation of polar and ionisable analytes, where precise pH control of the mobile phase determines retention time and peak symmetry. The ACS grade is essential here lower-purity grades introduce UV-absorbing impurities that raise baseline noise in UV and DAD detection. When preparing pH buffer solutions for instrument calibration or sample preparation, potassium phosphate monobasic ACS grade is the correct reagent for phosphate-based reference standards.
In pharmaceutical applications, potassium phosphate monobasic is used as an electrolyte in IV fluids and oral rehydration salts (ORS), as a buffer in tablet and liquid formulations, and as a mineral supplement providing both potassium and phosphorus. Its pharmacopoeial compliance (USP, EP, BP) makes it acceptable for use in drug product manufacturing without additional qualification steps. It is also used alongside analytical reagents such as silver nitrate in potentiometric titration methods for chloride determination in pharmaceutical raw materials where precise phosphate buffering of the titration medium is required for accurate endpoint detection.
In the food industry, potassium phosphate monobasic is approved as food additive E340(i) used as an acidity regulator, sequestrant, and mineral supplement. Applications include buffering in energy drinks and sports nutrition formulas, mineral supplementation in ORS powders and electrolyte beverages, texture and stability improvement in processed dairy products and baked goods, and as a yeast nutrient in fermentation processes.
Potassium phosphate monobasic is a key source of both phosphorus (P) and potassium (K) in agricultural fertiliser formulations. Its complete water solubility makes it ideal for hydroponic nutrient solutions, fertigation systems, and foliar spray applications where NPK delivery in dissolved form is essential. In hydroponics, it is used to support root development, flowering, and fruiting phases where P and K demand is highest.
In water treatment, potassium dihydrogen orthophosphate monobasic is used as a corrosion inhibitor in heating and cooling water systems, forming a thin protective phosphate film on metal surfaces that prevents scale deposition and corrosion. It is also used as a standard reference material in phosphate determination methods for drinking water and wastewater quality analysis.
Lab Chemicals is an authorised Merck distributor supplying EMPARTA® ACS grade analytical reagents to pharmaceutical manufacturers, NABL-accredited testing laboratories, food and beverage QC facilities, and research institutions across India for over three decades. We supply potassium phosphate monobasic EMPARTA® ACS (Merck product code 1.93205) in 500g, 5kg, and 50kg pack formats with Certificate of Analysis confirming compliance with ACS, USP, EP, and BP specifications. Our technical team can advise on grade selection, buffer preparation protocols, and documentation requirements for GMP or pharmacopoeial analytical method validation.
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