Analitica Lab

Calibration and Validation of an Analytical Balance

ABSTRACT

The analytical balance is an instrument used very often in the laboratory environment, if it is not used properly, serious errors can be introduced into the calculations and results of the experiment. In this experiment it is introduced an analytical balance validation method in which is performed a replicate analysis (x10) of a 100g standard mass and a similar replicate analysis to measure three different objects (x3) which standard weights are given. Also we calibrate the balance by accurately the volume of a liquid delivered by a pipet knowing the density of the H2O at the working temperature. The results reflected that the 100g weighting had a 0.000017g standard deviation and the 30 mL delivered volume had a 0.0016g which leads us to very precise results. Through the SOP and USP analysis implemented to validate the analytical balance we obtain precise and very reliable results.

INTRODUCTION

Weighing is the most common and most fundamental procedure in chemical work. Today’s laboratory balances incorporate the latest advancements in electronics, precision mechanics, and materials science. Gains to the chemists are unprecedented ease of use, versatility, and accuracy. An analytical balance is an instrument of daily use at the laboratory. This is the reason why the chemists must dominate some necessary techniques as cleaning validation in order to ensure good practices in their work environment. Validation is the process in which is demonstrated the accuracy and realness of an instrument. Scientists use a lot of equipment in their experiments, and it’s very important for these materials to be calibrated.

Calibration constitutes one of the Standard Operating Procedures (SOP’s) and it’s key to finding reliability in our results. The equipment to be use in the experiment is the analytical balance that throughout the years scientists have seen how it is routinely used to perform organic, metal and traditional chemistry analysis in different basis. The analytical balance is used to determine the highest precision in analytical weighing processes, because it can weigh up to ±0.0001g in a very fast time. This experiment put on practice our skills in order to have lower standard deviation error, in which will be based the experiment’s success. The standard operating procedures to use an analytical balance are a simple gravimetric exercise that consists in various steps: Level the balance using the air-bubble float, observe the required warm-up period or leave the balance constantly under power, handle weighing objects with forceps, always close the sliding doors on the balance when weighing, zeroing, or calibrating, accept and record the displayed result as soon as the balance indicates stability and check the reliability of each balance every day against certified weights, as it is critical to the performance of the laboratory.

It’s important to remember to weight always by difference and never by using tare, because it will eventually affect the realized work. Handling the sample with the hands is another practice that must be avoid because the fingerprints and the oils produced by our hands and gloves can have an effect in the results of an experiment.

The techniques were used in this experiment to prove how effective and how precise is an analytical balance. We measured ten times a standard weigh of 100g, three different standard weights and also a specific delivered volume. The standard deviation and the average of the results were calculated with the purpose of proving the acceptance and reliability of the employed technique, and the accuracy of the work.

EXPERIMENTAL SECTION

The equipment used were; an Analytical Balance (ACCULAB L-Series LA-110 Max.110g),, a 100g standard mass, and three metal standard mass pieces each weighing, 12.3056g, 8.3014g, 4.2450g. Also for the second exercise we need a clean 10 mL pipet and a weighing bottle with distilled water.

A 100g standard mass was weighed in ten replicated analysis in an analytical balance. After this exercise, the weight of 3 standards weights (12.3056g, 8.3014g, 4.2450g),

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