Differentiation Between Humic and Non-Humic Substances Using Alkaline Extraction and Ultraviolet Spectroscopy.

Background: Although humic substances are the principal ingredients in processed humic products, there has been no practical way to determine if a material is humified, allowing fake products to be used by farmers instead of genuine humic substances.

Objective: To develop a test method using conventional laboratory techniques to determine if a material is humified.

Method: A neutralized extract is prepared using the standardized extraction protocols specified in ISO 19822:2018(E).

Environmental and Agricultural Relevance of Humic Fractions Extracted by Alkali from Soils and Natural Waters.

To study the structure and function of soil organic matter, soil scientists have performed alkali extractions for soil humic acid (HA) and fulvic acid (FA) fractions for more than 200 years. Over the last few decades aquatic scientists have used similar fractions of dissolved organic matter, extracted by resin adsorption followed by alkali desorption. Critics have claimed that alkali-extractable fractions are laboratory artifacts, hence unsuitable for studying natural organic matter structure and function in field conditions.

Correlation between restriction endonuclease analysis and PCR ribotyping for the identification of Clostridioides (Clostridium) difficile clinical strains.

Restriction endonuclease analysis (REA) and PCR ribotyping are two typing systems that have been frequently utilized for molecular epidemiologic characterization of Clostridioides (Clostridium) difficile. To correlate typing data obtained from each method, we performed both REA and PCR ribotyping on a large and diverse set of historical and contemporary C. difficile infection clinical isolates.

A multilaboratory comparison of calibration accuracy and the performance of external references in analytical ultracentrifugation.

Analytical ultracentrifugation (AUC) is a first principles based method to determine absolute sedimentation coefficients and buoyant molar masses of macromolecules and their complexes, reporting on their size and shape in free solution. The purpose of this multi-laboratory study was to establish the precision and accuracy of basic data dimensions in AUC and validate previously proposed calibration techniques. Three kits of AUC cell assemblies containing radial and temperature calibration tools and a bovine serum albumin (BSA) reference sample were shared among 67 laboratories, generating 129 comprehensive data sets.