MLAB I - Laboratory Skills I: Reagent/Solution Preparation & Specimen Processing

A comprehensive set of practice flashcards covering key concepts from reagent/solution preparation, solution calculations, and specimen processing including plasma vs. serum, centrifugation, and safety.

What is the main objective of C7-a in Lesson 3?

Demonstrate the ability to prepare/store reagents, solutions, stains or media to specifications and accurately perform calculations/dilutions for reagent preparation.

What does C7-c require students to be able to do?

Perform titrations using a pH meter.

What principle does C10-a cover?

Calculating ratio, proportion, and dilution.

What does C11-a focus on?

Preparation, standardization, and storage of molar, isotonic, and percentage (w/w, v/v, w/v) solutions.

What does C11-b require in reagent preparation?

Accurately perform calculations and preparation of dilutions using concentrated and diluted reagents.

What grades of chemicals should you relate to according to C11-c?

Analytical, technical, commercial, CP, USP, BP, certified ACS.

What is included in C6-f regarding specimens?

Ability to prepare specimens for analysis including the separation of plasma/serum from cells.

Name a hazard associated with reagent preparation.

Chemical, physical, and/or biological hazards.

Before using a chemical, what two sources should you consult?

The chemical label and the MSDS (Material Safety Data Sheet).

What PPE guideline is emphasized for chemical use?

Use the recommended PPE and work practice controls.

Where should fumes-producing chemicals be used?

Only in a fume hood.

What type of containers should reagents be prepared in?

Chemically clean, dry, non-reactive containers.

Why is certified glassware recommended for critical measurements?

Because markings on rough glassware are approximate; certified glassware provides accuracy.

What should be selected for reagent water?

Correct grade of reagent water.

What pipetting consideration is important for liquids?

Correct pipetting techniques must be used.

When should volumetric pipets be used?

For critical measurements and when preparing standards and controls.

Where are standards and controls usually stored?

Refrigerated.

What should you inspect a laboratory reagent for before use?

Signs of deterioration such as color change, precipitation, or turbidity.

Name two high-purity chemical grades mentioned.

ACS reagent grade and ultrapure (spectrograde/nanograde/HPLC pure).

What are lower grades of chemicals that should not be used in clinical reagents?

Purified, practical, technical, or commercial grades.

What are the four methods listed for solution preparation?

Dilutions, ratios, percent solutions, and molar solutions.

What formula is used for dilutions?

C1 x V1 = C2 x V2.

How is a dilution commonly expressed?

As a ratio, proportion, or fraction.

In a 1:5 dilution, what does this mean?

1 part sample to 4 parts diluent, for a total of 5 parts.

In Problem A, what is the final volume when making a 1:5 buffer for 70 mL?

70 mL total; 2 parts A and 5 parts B yield 20 mL of A and 50 mL of B.

What is the general rule for dilutions regarding concentration after dilution?

Divide the original concentration by the dilution factor (the reciprocal of the dilution).

What is a 1:100 dilution of blood in WBC counting achieved by?

Adding 0.02 mL (20 μL) blood to 1.98 mL diluent for a total volume of 2.0 mL.

If a 2 M solution is diluted 1:5, what is the new concentration?

0.4 M.

What is a percent solution?

Concentration expressed as the weight of solute per 100 weight or volume units of solution.

What does w/v stand for in percent solutions?

Weight per volume.

What does v/v stand for in percent solutions?

Volume per volume.

What does w/w stand for in percent solutions?

Weight per weight.

How many grams NaCl are needed to make 1% saline in 100 mL?

1 g NaCl per 100 mL solution.

How would you prepare 0.85% (w/v) saline for 500 mL?

Weigh 4.25 g NaCl, dissolve in ~250 mL water, then fill to 500 mL with water.

What is a 10% bleach (v/v) solution preparation example?

Add 10 mL of chlorine bleach to 90 mL of water to make 100 mL total.

What is a two-fold serial dilution?

Each subsequent tube is twice as dilute as the previous one.

In a nine-tube two-fold dilution starting at 1:2, what is the dilution in tube 9?

1:512.

What is a titer?

The reciprocal of the highest dilution that gives the desired reaction.

What is an end-point titer example in a serum dilution?

If the last reactive tube is 1:64, the titer is 64.

What is an aliquot in specimen handling?

A portion of a specimen used for testing.

Why must serum/plasma be separated from cells within 2 hours?

To preserve analyte stability and accuracy of tests.

Name a common reason for chemistry specimen rejection.

Hemolysis.

Name a common reason for hematology specimen rejection.

Clotting.

List some criteria leading to specimen rejection (non-exhaustive).

Inadequate/missing ID, wrong tube, outdated tube, contamination, improper handling, QNS/NSQ, delay in testing.

Why should tubes awaiting centrifugation be kept upright with stoppers on?

To prevent CO2 loss and pH changes.

What can happen if the stopper is removed after centrifugation?

Loss of CO2 and rise in pH, affecting tests like pH and CO2.

What are common contamination sources in centrifugation tubes?

Sweat droplets, glove powder, evaporation.

What is the difference between serum and plasma?

Serum is the liquid after blood has clotted (no fibrinogen); plasma is the liquid portion of anticoagulated blood.

What top color is used for serum separator tubes (SST)?

Gold top (SST) with gel.

What anticoagulant is used in PST (plasma separating tubes)?

Heparin (often lithium heparin) with gel.

What must be complete before centrifuging serum tests?

Complete clotting of the specimen.

How long does complete clotting typically take at room temperature?

30 to 60 minutes.

How quickly do serum separator tubes clot when mixed properly after collection?

Usually within 15 minutes.

How quickly does BD rapid serum tube (RST) clot?

About 5 minutes.

What is the recommended processing timeframe after collection?

Processing should occur within 2 hours.

What should be done if enzyme tests require immediate separation?

Freeze the serum/plasma as soon as possible.

Why store samples in the dark?

Bilirubin is degraded by light.

What is an aliquot's purpose when multiple tests are ordered?

To test different tests/instruments on the same specimen without cross-contamination.

What is OSHA guidance for handling blood or infectious materials during aliquoting?

Minimize splashing, spraying, splattering, and droplet generation.

What precaution should you take when transferring serum/plasma to aliquot tubes?

Avoid pouring; use disposable transfer pipettes to minimize aerosols.

Why must aliquot tubes be labeled with the same ID as the specimen?

To ensure correct test matching and patient identification.

Why should you avoid mixing serum and plasma from different anticoagulants in the same aliquot tube?

To prevent cross-interference and incorrect results.

What should you do with aliquot tubes after filling?

Cover or cap them.

What PPE is typically required when processing specimens?

Gloves, lab coat; eye protection; possibly a face shield or splash shield.

What is a serum tube with a red/gray mottled stopper commonly called?

Serum Separator Tube (SST).

What are the red-top tubes used for?

Serum collection (no anticoagulant or clot activator in plain red tubes).

What is the function of the gel in gel separator tubes during centrifugation?

Forms a barrier between serum and cells.

What is the difference between serum and plasma in terms of clotting factors?

Serum lacks clotting factors (fibrinogen) because they are consumed during clotting; plasma contains clotting factors.

What does the term 'anticoagulant' indicate when describing plasma samples?

Blood collected with an anticoagulant to prevent clotting.

What color top tubes denote the presence of anticoagulants such as lithium heparin or Na citrate?

Green, light-green (PST), and blue tops indicate anticoagulants; specific additives vary.

What is the purpose of centrifugation in specimen processing?

To separate liquid component (serum/plasma) from cells.

What is the typical range for complete clotting time at room temperature for serum tests?

30–60 minutes.

What does 'centrifugation' do to the gel in some tubes?

Pushes gel to form a barrier between serum/plasma and cells.

What is a 'buffer' dilution problem example?

A problem where 2 parts A to 5 parts B produce a 70 mL buffer, solved by determining a volume per part.

What formula helps solve dilution problems using parts?

Total parts = parts A + parts B; solve for part volume given total.

What is the concept of a 'dilution factor' in serial dilutions?

The reciprocal of the dilution; e.g., 1:100 has a dilution factor of 100.

What is the key difference between a 1:2 dilution and a 1:10 dilution?

1:2 halves the concentration; 1:10 reduces concentration tenfold.

What is the isotonic principle in solutions?

A solution with the same osmotic pressure as another solution (e.g., physiological saline is isotonic with blood).

What is the composition of physiological saline typically cited in labs?

0.85% NaCl (about 0.15 M).

What does 'molar (M) solution' mean?

A solution containing 1 mole of solute per liter of solution.

How is a 1 M NaCl solution defined in terms of moles and liters?

1 mole of NaCl per liter of solution.

What is the formula weight concept used to calculate molarity?

Moles = weight of solute / formula weight.

What is the importance of using 1 L as the final volume when making a 1 M solution?

You add solute to dissolve and then bring the solution to a volume of 1 L.

What is meant by 'mole' in solution chemistry?

A unit equal to 6.022 x 10^23 particles of a substance.

What is the relationship between molarity and grams per liter?

Molarity is moles per liter; grams per liter depends on molecular weight.

What is the difference between 'analytical grade' and 'technical grade' chemicals?

Analytical (ACS) is suitable for quantitative and qualitative work; technical grade is lower purity for non-clinical use.

What does 'ACS' stand for in chemical grades?

American Chemical Society.

What does 'HPLC grade' indicate?

Ultrapure grade for high-performance liquid chromatography.

What is the recommended storage temperature for many reagents used in solution prep?

Refrigerated or room temperature as specified; standards/controls are often refrigerated.

What is the purpose of standardizing solutions?

To ensure accuracy and reliability of test results by calibrating concentration.

What is a 'pH meter titration' used for in this course?

To determine the acidity or basicity during titration experiments.

What is 'CLRW' an acronym for?

Certified Laboratory Reagents Water.

What is a critical measurement glassware type used when accuracy matters?

Volumetric flasks.

What is a common unit for percent solutions in w/v form?

grams of solute per 100 mL of solution.

What is the recommended handling practice when a specimen is contaminated?

Dispose of the specimen and follow proper biosafety procedures.

What is the titer used for in serology?

To indicate the level of a component (such as antibody) by testing serial dilutions.

What is the 'end-point' in a serial dilution test?

The last dilution that shows a reaction.

What is the 'buffer solution' in dilution problems often expressed as?

A mixture of two reagents in specified parts.

What is the consequence of opening a stopper during specimen handling?

Potential aerosols and droplet formation; precautions include gauze and splash shield.

What is the primary goal of aliquoting in multi-test workflows?

To allocate portions of a specimen for different tests or instruments while maintaining ID integrity.