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Principle of Scanning Electron Microscopy (SEM) SEM scans a focused electron beam across the specimen’s surface. Secondary electrons emitted from the specimen surface are collected to form an image. SEM provides high-resolution, three-dimensional images that reveal the specimen’s surface topology. Procedure for Scanning Electron Microscopy (SEM) Specimen Preparation: Fixation: The specimen is fixed to preserve … Read more
Principle of Simple Staining: Simple staining involves using a single dye to color bacterial cells, making it easier to observe their shape, size, and arrangement under a microscope. Procedure: Preparation of Smear: A small sample of bacteria is spread on a microscope slide to form a thin film and then air-dried. Fixation: The slide … Read more
Quantitative Measurement of Bacterial Growth involves measuring either the total cell counts or the viable cell count. Total Cell Count Methods Counter Chamber Method (Hemocytometer) Description: A manual counting method using a specialized slide with a grid. Procedure: A known volume of bacterial suspension is placed on the hemocytometer grid. The grid is viewed under … Read more
Phase contrast microscopy is a technique that enhances the visibility of transparent and colorless specimens by converting subtle differences in the optical path length (caused by variations in refractive index and thickness) into variations in contrast. This allows for the observation of live, unstained cells, making internal structures visible without damaging or altering the specimen. … Read more
Electron microscopy offers much higher resolution than light microscopy by using electron beams instead of light. There are several types, each with unique principles and advantages. Types of Electron Microscopy: Transmission Electron Microscopy (TEM): Electrons pass through a thin specimen. Provides detailed images of internal structures. Scanning Electron Microscopy (SEM): Electrons scan the specimen surface. … Read more
Principle of Transmission Electron Microscopy Transmission Electron Microscopy works by transmitting a beam of electrons through an ultra-thin specimen. As electrons interact with the specimen, the transmitted electrons form an image. Due to the short wavelength of electrons, TEM can resolve details as small as 0.1 nm, making it suitable for studying cellular ultrastructure and … Read more
A pharmacopoeia is an authoritative collection of standards for the quality, purity, and strength of drugs, excipients, and dosage forms. It provides guidelines on the composition, preparation, storage, and labeling of pharmaceutical products. Pharmacopoeias are maintained by regulatory authorities and are essential references for pharmacists, chemists, and healthcare professionals. History of Pharmacopoeia: Early Compilations: Ancient … Read more
Definition of Significant figures: Significant figures are the digits in a measurement that carry meaning and contribute to its precision. They include all known digits plus one estimated digit. Rules for Significant Figures: All non-zero digits are significant. Any zeros between significant digits are significant. Leading zeros (zeros to the left of the first non-zero … Read more
Accuracy and precision, significant figures are fundamental concepts in scientific measurement and calculations. Here’s a breakdown of each term: Accuracy Definition: Accuracy refers to how close a measured value is to the true or accepted value of the quantity being measured. Example: If the true value of the mass of an object is 50.0 g, … Read more
Errors in Analytical Chemistry can impact the accuracy and precision of results. Understanding their sources and types helps minimize their effect and improve the reliability of data. Sources of Errors in Analytical Chemistry: Instrumental Errors: Caused by limitations or malfunctions of instruments (e.g., balances, pipettes, spectrophotometers). Contributing factors: calibration errors, temperature fluctuations, mechanical issues. Methodological … Read more
