Standard Solutions
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Buffer solutions
Scharlau Standard Solutions
Scharlau standard solutions represent a critical component in analytical chemistry, providing the reference points necessary for instrument calibration and volumetric quantification. These solutions are technically formulated to provide exact molarities, normalities, or mass concentrations, depending on the application. The range includes volumetric solutions for titration, buffer solutions for pH calibration, and high-purity standards for advanced instrumental techniques like ICP, AAS, and Ion Chromatography. Every solution is prepared using high-purity raw materials and ultra-pure water, ensuring that the final product is free from interfering ions and contaminants that could compromise analytical integrity.
A key technical feature of Scharlau standards is their direct traceability to National Institute of Standards and Technology (NIST) reference materials. This traceability is documented in a comprehensive Certificate of Analysis (CoA) that specifies the certified value, the associated uncertainty, and the expiration date.
NIST Traceability and the Metrological Chain
The reliability of Scharlau standard solutions is based on a robust metrological chain. Each standard is calibrated against primary reference materials from NIST. This technical link ensures that measurements performed in any laboratory using these standards are globally comparable. The traceability process includes a rigorous assessment of all variables in the preparation process, ensuring the certified value remains accurate.
Certified Reference Materials (CRM) under ISO 17034
Scharlau manufactures Certified Reference Materials (CRMs) following the requirements of ISO 17034. Technically, this involves long-term stability studies and homogeneity testing to ensure the concentration remains constant throughout the product's shelf life. These CRMs are used in highly regulated industries where the measurement of uncertainty must be clearly defined. The inclusion of a detailed uncertainty budget in the CoA provides the user with the statistical confidence required for critical quantitative analysis.
Precision Volumetric Solutions for Titration
Volumetric solutions, such as Silver Nitrate, Sodium Hydroxide, or Iodine, are standardized to specific normalities. The titration process used for standardization is performed using automated potentiometric systems to eliminate human error. These solutions are formulated to have a "factor" as close to 1.000 as possible, reducing the need for complex calculations during routine laboratory titrations and ensuring high precision in acid-base, redox, and precipitation reactions.
Single and Multi-Element Standards for ICP and AAS
For elemental analysis, Scharlau provides high-purity standards intended for Inductively Coupled Plasma (ICP) and Atomic Absorption Spectroscopy (AAS). These standards are typically prepared in a 2% to 5% nitric acid matrix to maintain the stability of the metal ions. Technically, they are checked for trace metal impurities using high-resolution mass spectrometry, ensuring that the background signal remains negligible. Multi-element blends are also available, precisely mixed to prevent chemical incompatibilities or precipitation between different elements.
pH Buffer Calibration and Temperature Compensation
Scharlau pH buffer solutions are technically validated to provide accurate pH values at 25 C. Because pH is temperature-dependent, each bottle features a detailed table showing the pH variation relative to temperature. These buffers are color-coded for easy identification (e.g., pH 4 in red, pH 7 in yellow) and are stabilized with preservatives to prevent microbial growth, which could otherwise shift the pH and affect electrode calibration accuracy.
Ion Chromatography Standards and Matrix Matching
In Ion Chromatography (IC), the purity of the standard is paramount to prevent peak interference. Scharlau IC standards are prepared from salts with 99.999% purity and dissolved in ultra-pure water with a conductivity of less than 1muS/cm. This technical attention to detail ensures that the baseline remains stable and that the retention times for anions like chloride, nitrate, and sulfate are highly reproducible, even at low parts-per-million (ppm) concentrations.
Shelf-Life Stability and Induction Sealing Technology
To prevent the degradation of standard solutions due to evaporation or atmospheric contamination, Scharlau employs induction sealing technology. This creates an airtight moisture barrier that prevents the entry of CO2, which could alter the pH of buffers or the normality of basic solutions. Stability tests are conducted under various storage conditions to define the expiration date accurately, ensuring the reagent remains within its certified specification until the moment the seal is broken.
Volumetric Concentrates for Space-Saving Preparation
For high-volume laboratories, Scharlau offers volumetric concentrates. These are technically prepared solutions housed in specialized ampoules or bottles that, when diluted to 1000 mL with distilled water, yield an exact 0.1 M or 1 M solution. This format provides a technical advantage by reducing shipping weight and storage space while maintaining the same NIST-traceable accuracy as pre-prepared large-volume solutions, provided that the dilution is performed with calibrated volumetric flasks.
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