clinical chemistry chapter 8

What is an analyte?

A solute dispersed in a solution that is measured in laboratory practice; also called a measurand.

What is a buffer solution?

A solution containing a weak acid and its salt OR a weak base and its salt that resists changes in pH.

What is centrifugation?

The use of centrifugal force to separate lighter portions of a solution from heavier portions.

What is a chemical hygiene plan (CHP)?

An OSHA-required plan listing responsibilities of employers, employees, and the chemical hygiene officer; includes an updated chemical inventory and safety information for chemicals.

What is CLSI?

Clinical and Laboratory Standards Institute; an organization that develops standards and guidelines to help laboratories meet quality and safety goals.

What is ergonomics?

The study of capabilities in relation to work demands, focusing on postures and conditions that reduce unnecessary static work and forces on the body.

What is an exposure control plan?

An OSHA-required plan that protects laboratory workers from potential exposure to bloodborne pathogens and ensures medical waste is safely managed.

What is OSHA?

Occupational Safety and Health Administration; a U.S. federal agency that regulates employee safety.

What is a pipette?

A device used to transfer a volume of liquid from one container to another.

What is a reagent?

A chemical used in laboratory applications, often requiring high purity.

What is a reference material?

A material or substance with established physical or chemical properties used for calibration, method verification, assigning values, or evaluating comparability of results.

What is relative centrifugal force (RCF)?

The force required to separate two phases, such as liquid and solid, in a centrifuge; expressed as multiples of gravity (×g).

What is a safety data sheet (SDS/MSDS)?

A technical document containing information about a hazardous chemical, including composition, hazards, safe handling, first aid, spill cleanup, disposal, and protective equipment.

What are standard precautions?

An infection-control approach that treats human blood and certain body fluids as if they are known to contain bloodborne pathogens.

What are the three methods of preparing reagent-grade water?

Distillation, ion exchange, and reverse osmosis.

What is distillation?

A process of vaporizing and condensing a liquid to purify or separate substances; distillation alone does not meet CLRW conductivity requirements.

What is ion exchange?

A process that removes ions to produce mineral-free deionized water.

What is reverse osmosis?

A process that forces water through a semipermeable membrane acting as a molecular filter; generally used as a preliminary purification method.

What is CLRW?

Clinical Laboratory Reagent Water; reagent-grade water meeting CLSI specifications for laboratory use.

What are the three major criteria/components used to evaluate CLRW?

Microbiological content, resistivity, and particulate/organic content according to CLRW specifications.

What is a primary reference material?

A highly purified material that is directly weighed or measured and dissolved to produce a solution with an exactly known concentration.

What is a secondary reference material?

A solution whose concentration is determined by analyzing an aliquot using an acceptable reference method calibrated with a primary reference material.

What is the main difference between primary and secondary reference materials?

Primary materials have concentration established directly from highly purified material; secondary materials have concentration established by analysis against a reference method.

What are primary reference materials used for?

Preparing solutions of known concentration and calibrating solutions of unknown strength.

What are secondary reference materials used for?

Supporting calibration and measurement procedures when concentration cannot be established simply by weighing the solute.

What are standard reference materials (SRMs)?

Well-characterized materials available from NIST with certified information about their chemical or physical properties.

What are certified reference materials (CRMs)?

Reference materials with certified values; available from organizations such as IRMM and WHO.

What are reference materials used for?

Calibrating instruments, validating methods, assigning values to materials, and evaluating comparability of results.

What are the three major types of pipettes used in the clinical laboratory?

Manual transfer/measuring pipettes, micropipettes, and electronic/mechanical pipetting devices.

What is a transfer pipette?

A pipette designed to transfer a single known volume of liquid.

What are examples of transfer pipettes?

Volumetric and Ostwald-Folin pipettes.

What is a measuring pipette?

A graduated pipette used to measure and deliver different volumes up to its maximum capacity.

What are examples of measuring pipettes?

Mohr and serologic pipettes.

What is a micropipette?

A pipette used to measure microliter volumes.

What are micropipettes mainly used for?

Accurate measurement and transfer of very small volumes, usually in microliters.

What are electronic/mechanical pipettes?

Programmable pipetting devices that use disposable plastic tips to aspirate and dispense specific volumes.

What is the main advantage of disposable pipette tips?

They reduce cross-contamination, eliminate washing between samples, and improve measurement precision.

What is the difference between a Mohr and serologic pipette?

Mohr pipettes are graduated between two marks; serologic pipettes are graduated to the tip and must be blown out to deliver the entire volume.

What is the proper pipetting position?

Hold the pipette vertically when adjusting the liquid level and during delivery.

What is a meniscus?

The curved upper surface of a liquid; the lowest part of the meniscus should be aligned with the calibration line at eye level.

What is centrifugation used for?

Separating lighter and heavier components of a solution.

What is the principle of centrifugation?

Centrifugal force causes particles of different density to separate.

What is RCF expressed as?

Multiples of gravity, such as 500 × g.

What is the RCF formula?

RCF = 1.118 × 10⁻⁵ × r × rpm².

What does r represent in the RCF formula?

The radius in centimeters from the center of rotation to the bottom of the tube.

What does rpm represent?

Revolutions per minute of the centrifuge rotor.

What factors affect sedimentation during centrifugation?

Rotational speed, rotor radius, and the effective path length traveled by particles.

What is an important centrifuge safety practice?

Balance tubes properly and use tubes that can withstand the required RCF.

What should be checked before centrifuging blood tubes?

Inspect tubes for cracks and check the centrifuge components for damage or contamination.

Why should blood tubes be centrifuged before opening?

To reduce the chance of producing an aerosol when the tube is opened.

What is dilution?

The process of decreasing the concentration or activity of a solution by adding solvent.

What is a simple dilution?

A single dilution in which a concentrated solution is diluted to a desired concentration.

What is a serial dilution?

A sequential set of dilutions performed in mathematical sequence.

What is the difference between simple and serial dilutions?

Simple dilution is one dilution step; serial dilution involves multiple sequential dilution steps.

What is the dilution equation?

C₁ × V₁ = C₂ × V₂.

What does C₁ represent in C₁V₁ = C₂V₂?

The initial or concentrated solution concentration.

What does V₁ represent in C₁V₁ = C₂V₂?

The volume of the initial concentrated solution used.

What does C₂ represent in C₁V₁ = C₂V₂?

The desired final concentration.

What does V₂ represent in C₁V₁ = C₂V₂?

The final total volume of the diluted solution.

How do you calculate final volume using the dilution formula?

V₂ = (C₁ × V₁) ÷ C₂.

What is the dilution factor?

The reciprocal of the dilution of the initial solution.

What does a 1:5 dilution mean?

One volume of initial solution is present in a total of five volumes of final solution.

What is the purpose of diluting to volume?

To reduce errors when mixing liquids of different composition.

What type of flask is commonly used to prepare an exact final volume?

A volumetric flask.

What is the purpose of a chemical hygiene plan?

To establish responsibilities and procedures for safely handling chemicals and maintaining chemical safety information.

Who is responsible for a chemical hygiene plan?

The laboratory, including employers, employees, and the designated chemical hygiene officer.

What are major elements of a chemical hygiene plan?

Responsibilities of employers/employees/chemical hygiene officer, updated chemical inventory, accessible chemical safety information, and procedures for safe chemical handling.

How often should the chemical inventory be updated?

Annually.

What information does an SDS/MSDS provide?

Chemical identity, composition, physical and chemical hazards, exposure limits, toxicity, first aid, spill cleanup, disposal, and required protective equipment.

What is the purpose of an exposure control plan?

To protect laboratory workers from bloodborne pathogens and ensure medical waste is safely handled.

What hazards does the exposure control plan address?

Potential exposure to bloodborne pathogens and safe management of medical waste.

What is a tuberculosis (TB) control plan?

A documented plan designed to minimize employee exposure to Mycobacterium tuberculosis.

What should a TB control plan include?

Defined employee exposure intervals and process controls to minimize aerosolization of Mycobacterium tuberculosis.

What is the purpose of Standard Precautions?

To prevent infection by treating blood and certain potentially infectious body fluids as infectious.

What specimens are handled using Standard Precautions?

Blood, serum, plasma, blood products, vaginal secretions, semen, CSF, synovial fluid, concentrated HBV/HIV, and any specimen visibly contaminated with blood.

What PPE is used under Standard Precautions?

Gloves, gowns/lab coats, face shields or masks, and eye protection.

What is one important Standard Precaution for pipetting?

Never perform mouth pipetting or blow out pipettes containing potentially infectious material.

How should potentially infectious material be mixed?

Do not bubble air through the liquid.

What should be done with sharps?

Dispose of sharps appropriately in rigid containers without unnecessary handling.

When should hands be washed?

Whenever gloves are changed and when leaving the laboratory.

What should be done to contaminated laboratory surfaces?

Decontaminate them with appropriate registered hospital disinfectants.

What is the purpose of an ergonomics program?

To prevent work-related musculoskeletal disorders.

What are common ergonomic risks in the clinical laboratory?

Awkward posture, repetitive motion, repeated force, poor workstation design, and improper equipment design.

What should an ergonomics program include?

Employee training, engineering controls, and assessment/remediation of ergonomic risks.

What is a biological hazard?

A hazard caused by infectious or potentially infectious biological materials.

What are examples of biological hazards in the laboratory?

Patient specimens, bloodborne pathogens, infectious agents, contaminated needles, and unfixed tissues.

How can biological exposure occur?

Needlestick injuries, splashes/sprays, spills, centrifuge accidents, and cuts from contaminated materials.

How are biological hazards controlled?

Use Standard Precautions, PPE, proper sharps disposal, handwashing, decontamination, biosafety procedures, and exposure-control practices.

What is a chemical hazard?

A hazard caused by chemicals that can produce burns, toxic effects, fumes, explosions, or fires.

How are chemical hazards controlled?

Proper labeling, storage, PPE, fume hoods, spill kits, safe handling, and following SDS instructions.

What is the proper way to dilute concentrated acid?

Slowly add acid to water while mixing; never add water to concentrated acid.

What should be used when handling acids or alkalis?

Safety glasses and appropriate protective equipment.

What is the purpose of a chemical fume hood?

To control harmful vapors and fumes, prepare reagents that produce fumes, and safely heat flammable solvents.

What is an electrical hazard?

A hazard involving electrical equipment or connections that can cause shock or fire.

How are electrical hazards controlled?

Replace worn wires, properly ground equipment, keep electrical equipment dry, and avoid using damaged or wet equipment.

Can electrical equipment be handled with wet hands?

No.

What should be done if liquid spills on electrical equipment?

Turn the equipment off immediately and dry it thoroughly; do not use it until safe.

What is the laboratory rule regarding extension cords?

Their use is generally prohibited; if temporarily necessary, strict safety requirements apply.

What is a fire hazard?

A condition or material that can cause or contribute to a laboratory fire.

What are common laboratory fire hazards?

Flammable liquids, gases, solvents, electrical equipment, and combustible materials.