What is the difference between an analytical balance and a precision balance?

An analytical balance provides readability of 0.1 mg or better, while a precision balance typically reads to 0.001 g or 0.01 g. Analytical balances include draft shields and are designed for highly sensitive measurements. Precision balances handle larger samples and are less affected by environmental conditions.

What readability do I need for my lab application?

You need a readability that is at least one-tenth of your smallest sample weight or required measurement increment. For example, measuring 100 mg samples may require 0.01 mg readability, while gram-level work may only need 0.01 g. Selecting higher readability than necessary increases cost without improving results.

Do lab balances need to be calibrated?

Yes, all lab balances require regular calibration to maintain accuracy. Calibration ensures measurements remain traceable to certified standards. Internal calibration simplifies this process by automating adjustments, while external calibration requires manual verification with certified weights. In regulated environments, calibration records must be documented and retained.

What is the difference between readability and repeatability?

Readability is the smallest increment of weight a balance will display. Repeatability is the degree of agreement between multiple measurements of the same mass, on the same balance, under the same conditions.

What is the best way to clean my balance to ensure accurate readings?

Inspect and clean before each use. A flannel cloth or soft brush works well for dusting and light cleaning. Use a non-abrasive cleaner for light spills, and a dry flannel cloth for glass parts. Set a regular maintenance schedule for deep cleaning to ensure optimal performance and instrument longevity.

Can vibration affect the accuracy of my balance?

Yes — even slight vibration from a heavy footstep can affect accuracy. Place the balance on a sturdy benchtop away from high-traffic areas such as hallways, elevators, stairways, and doors. If that placement is not possible, an anti-vibration table should be considered.

Analyzing Samples for Metals (Part One)

Lead, cadmium, and chromium are among many metal contaminants that may be present in the environment—in ground water, wastewater, and soil—and can accumulate in the body and cause health risks. Cadmium, for example, is a toxic metal present in industrial work sites. At specified levels of exposure, cadmium can cause kidney and bone damage.

Because of the dangers they pose, the Environmental Protection Agency (EPA) has set maximum contaminant levels (MCL) for metals. Public water supplies are monitored for these metals regularly. Many manufacturers are required to analyze their wastewater for the presence of these contaminants.

The National Pollutant Discharge Elimination System (NPDES) permit program controls water pollution by regulating the sources that discharge pollutants into US waters. Manufacturers with NPDES permits must detect and quantify specified metals on a regular basis. Many self- monitor to remain consistently in compliance.

What equipment is used to detect metals?

The Process: Metals Digestion

The metal digestion process seeks to maintain analytes in a solution and decompose the solids without loss or contamination. The digestion of metals typically involves acids and heat. Acid digestions require a fume hood for venting toxic fumes.

Historically, the digestion process involved taking a beaker containing the sample and adding acid. The beaker was then placed in a stirring hot plate under a hood for several hours.

EPA-approved systems have streamlined the metals digestion process, improving productivity and increasing safety. Equipment, such as the HotBlock^®System, shown at right, uses disposable digestion cups with accurately marked graduations to eliminate transfer steps and reduce sample contamination. PTFE-coated blocks with individual wells bring samples to temperature quickly and maintain uniform heat distribution for up to 54 samples simultaneously.

For the remaining parts of the process, including Post Digestion Filtration and Metals Analysis, read part two in our next blog.

Analyzing Samples for Metals (Part One)

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