Basic Laboratory Equipment

A setting, graduation, or display is only a nominal value. The laboratory must know what an item contains, delivers, weighs, heats, cools, or separates under the conditions in which it is used. Selection begins with the measurement procedure’s required performance. Verification then shows whether the individual item remains fit for that use.

Temperature-controlled equipment

Reaction rates, material stability, incubation, and chromatography all depend on temperature. Water baths, heating blocks, incubators, refrigerators, freezers, and instrument compartments should be checked at the temperatures used by the procedure. A display reading alone cannot establish the temperature at the sample position.

Metrological traceability is a property of a measurement result. It requires a documented, unbroken chain of calibrations to a specified reference, with every link contributing to the measurement uncertainty. A label that says “NIST traceable” does not establish that chain by itself. Records should identify the reference device, calibration results and uncertainty, relevant calibration points, correction factors, and the device being checked.²

For a 37 °C bath, allow the bath and reference probe to equilibrate, measure at the working setpoint and representative sample locations, apply the reference correction, and compare the result with the acceptance interval in the measurement procedure. Map locations when uniformity matters. Set check and recalibration intervals from manufacturer instructions, stability history, use, and the effect of an incorrect temperature. There is no single annual or semiannual interval for every device.

Temperature conversions are reviewed in Laboratory Mathematics and Diagnostic Performance.

Volumetric glassware and pipettes

Contain, deliver, and approximate

Volumetric apparatus is marked for a specific function and calibration temperature. To contain (TC) ware holds its stated volume. Residual liquid remains after pouring. To deliver (TD) ware is calibrated so that the stated volume leaves the device when the specified drainage procedure is followed. ASTM E694 defines general requirements for Class A and Class B laboratory glass volumetric apparatus. Class B tolerances are generally twice the corresponding Class A range.³

For clear aqueous liquids, read the bottom of the meniscus at eye level unless the device or procedure specifies another convention. Use a pipette aid. A blowout pipette has a manufacturer marking and requires expelling its residual liquid. A self-draining pipette completes delivery by gravity after the stated drainage time. Treating every pipette the same creates a systematic volume error.

Class and marking establish the apparatus specification. Fitness for a task also depends on cleanliness, damage, temperature, drainage time, and the uncertainty allowed by the measurement procedure. An intact Class A flask can be suitable for preparing a calibrator and still be unsuitable if its material interacts with the analyte.

Piston pipettes

An air-displacement pipette moves an air cushion between the piston and liquid. Temperature differences, evaporation, viscosity, tip fit, immersion depth, aspiration angle, and plunger timing can change the delivered volume. A positive-displacement pipette moves a piston in direct contact with the liquid inside a capillary or tip. This design can improve delivery of viscous, volatile, foaming, or dense liquids. The selected device must cover the intended volume within its specified operating range.

A sound pipetting sequence uses the specified tip, conditions the tip when the procedure calls for it, aspirates with the device near vertical at a consistent depth, pauses long enough for liquid entry, withdraws without droplets on the outside, and dispenses smoothly against the receiving vessel as instructed. Reverse pipetting, prewetting, or a positive-displacement device can address particular liquids, but each changes the procedure and requires local verification.

Gravimetric calibration determines delivered volume from the mass of water, water density at the measured temperature, evaporation controls, and replicate deliveries. ISO 8655-2:2022 specifies metrological requirements and maximum permissible errors for air-displacement and positive-displacement pipettes. The laboratory still chooses acceptance criteria that satisfy the intended use and follows the pipette manufacturer’s maintenance requirements.⁴ Routine performance checks can detect leakage, seal wear, contamination, and operator technique between full calibrations. Their frequency should follow risk, use, and performance history.

Containers, cleaning, and compatibility

Container material can adsorb an analyte, release additives, transmit gas or vapor, or fail in contact with a solvent. These effects depend on the exact polymer, analyte, concentration, contact time, and temperature.

Use the measurement procedure and the product’s compatibility data. Trace-element, molecular, cell, and protein work may require dedicated, certified-clean, low-binding, nuclease-free, sterile, or single-use ware. Those descriptions are separate properties and should not be assumed from the polymer name.

Cleaning starts before residue dries. Use a laboratory detergent and validated process, rinse with water of the required grade, inspect the item, and prevent recontamination during drying and storage. Residual detergent can alter pH, suppress enzymes, change surface tension, and add optical background. A final-rinse check is useful only when the check can detect the contamination relevant to the procedure.

Balances, desiccators, and mass standards

A balance estimates mass by comparing the load with a calibrated response. Readability is the smallest displayed increment; capacity is the greatest permitted load; repeatability describes agreement among repeated weighings; linearity describes response across the range. These characteristics answer different questions.

Before weighing, confirm that the balance is level, within its verified range, clean, stable, and protected from drafts, vibration, temperature gradients, and static charge. Center the load, close the draft shield, allow the reading to stabilize, and use tare only as the procedure intends. Fingerprints and moisture change small mass standards, so handle them with clean forceps or gloves. Checks should use suitable standards at masses that challenge the working range, with documented traceability and uncertainty.^1,2

A desiccator protects hygroscopic material and allows a heated vessel to cool in a low-moisture enclosure before weighing. The desiccant’s indicator, regeneration limit, and replacement schedule belong in the procedure. Anhydrous identifies a chemical form without water of crystallization; it does not guarantee that an opened reagent has remained dry.

Centrifugation

A centrifuge creates a radial acceleration that separates components according to density, size, shape, medium, and run conditions. Revolutions per minute describe rotor speed. Relative centrifugal force (RCF) accounts for both speed and rotor radius:

RCF = 1.118 × 10⁻⁵ × r × rpm²

Here, r is the radius in centimeters specified for the separation point. For a 10 cm radius at 3,200 rpm:

RCF = 1.118 × 10⁻⁵ × 10 × 3,200² = 1,145 × g

The same rpm produces a different RCF in a different rotor. Report or program RCF when a method specifies RCF, and use the radius definition in the rotor instructions. A fixed-angle rotor sediments material toward the outer wall and bottom of the tube. A swinging-bucket rotor lets tubes become horizontal, which supports layered separations and level interfaces.

Before a run, inspect the rotor, buckets, seals, and rated tubes; verify that the load, speed, temperature, and time match the procedure; and balance opposing positions by mass as the manufacturer directs. Close the lid and allow the rotor to stop completely. Aerosol-generating materials require the containment and opening practice in the laboratory’s safety procedure. Speed, timer, temperature, and braking performance are checked on the schedule justified for the instrument and application.¹

Reagents and laboratory water

Labels such as reagent grade, spectrophotometric grade, and chromatography grade describe different specifications. Choose the grade named by the measurement procedure. A NIST Standard Reference Material carries certified property values, uncertainties, intended uses, and a certificate. Its status and certificate must be checked for the use at hand; “reference material” alone does not mean every value is certified.²

CLSI GP40, fifth edition, organizes medical-laboratory water by application. Its scope includes clinical laboratory reagent water, special reagent water, molecular biology water as a type of special reagent water, instrument feed water, water supplied by a method manufacturer, autoclave and wash water, and commercially bottled purified water. The laboratory validates that the selected water is fit for its purpose and monitors relevant ionic, organic, microbial, particulate, and colloidal contamination over time.⁵

Purification can combine prefiltration, reverse osmosis or distillation, ion exchange, activated carbon, ultraviolet treatment, and membrane filtration. The needed sequence follows the incoming water and final specification. Storage and distribution can recontaminate water after purification, so monitoring must represent the point of use. Commercially bottled water also requires verification for its intended application.

Mixing and solution preparation

Mixing should produce a uniform material without damaging it. Gentle inversion can resuspend anticoagulated blood; rocking can maintain cellular controls; vortexing can disperse a compatible reagent. The specimen, material instructions, and downstream measurement determine the motion and duration. Foaming, aerosol production, hemolysis, cell damage, and incomplete resuspension are observable reasons to stop and correct the technique.

Solution preparation links the equipment above:

1. Confirm the chemical form, purity, formula mass, and safety precautions.
2. Weigh with a balance suitable for the required uncertainty.
3. Dissolve in less than the final solvent volume using compatible ware.
4. Transfer quantitatively to a suitable volumetric flask.
5. Equilibrate to the flask’s calibration temperature when volume accuracy matters.
6. Bring to the mark, mix completely, label, and store as the procedure requires.

For 300 mL of 0.200 mol/L anhydrous calcium chloride with a formula mass of 111.0 g/mol, the required mass is 0.200 mol/L × 0.300 L × 111.0 g/mol = 6.66 g. Water of hydration or an assay value below 100% changes the mass calculation. Molarity, molality, reaction-specific normality, dilutions, pH, and buffer calculations are covered in Laboratory Mathematics and Diagnostic Performance.¹

References

1. Bishop ML, Fody EP, Van Siclen C, Mistler JM, Moy M. Clinical Chemistry: Principles, Techniques, and Correlations. 9th ed. Jones & Bartlett Learning; 2023.
2. Bruce SS, Possolo A, Watters RL Jr. Metrological Traceability: Frequently Asked Questions and NIST Policy. NIST Technical Note 2156. National Institute of Standards and Technology; 2021. Accessed August 31, 2026.
3. ASTM International. Standard Specification for Laboratory Glass Volumetric Apparatus. ASTM E694-18(2024). ASTM International; 2024.
4. International Organization for Standardization. Piston-Operated Volumetric Apparatus: Part 2, Pipettes. ISO 8655-2:2022. International Organization for Standardization; 2022. Accessed August 31, 2026.
5. Clinical and Laboratory Standards Institute. Preparation and Testing of Reagent Water in the Medical Laboratory. 5th ed. CLSI guideline GP40. Clinical and Laboratory Standards Institute; 2024. Accessed August 31, 2026.