Clinical Chemistry Lecture Guide

Transcription

1 Clinical Chemistry Lecture Guide Key Terms Basic Principles Buffer Centrifugation Colligative property Conductivity Deionized water Density Dilution Distilled water Equivalent weight ( EqW ) Molality Molarity ( M ) Normality ( N ) Osmotic Pressure Oxidation / Reduction Oxidizing / Reducing Agent Percent Solution ph pk Pipet Primary / Secondary Standard Serial Dilution Solute / Solvent Specific Gravity Standard Reference Materials Whole Blood / Serum / Plasma Valence Celsius / Fahrenheit To Deliver / To Contain Review of Textbook Chapter Objectives Define the prefixes commonly used in units of measurements Perform simple conversions ( temperature and common measurements) Identify different grades of purity for chemical reagents Define different types of standards that are used in clinical chemistry Define the terms in the Key Terms list Describe different pipets and their proper uses Define 3 different types of specimens that are commonly used in a clinical laboratory Identify the anticoagulants and colored tops associated with blood collection tubes I. Units of Measure A. Basic SI quantities and units Quantity Metric Symbol SI Basic Unit length meter m meter mass gram g kilogram volume liter L not recognized quantity / amount of substance mole mol mole time second s? B. Metric or SI prefixes Prefix Factor Symbol -18 atto 10 a -15 femto 10 f -12 pico 10 p MLAB Clinical Chemistry Basic Principles 1

2 Prefix Factor Symbol -9 nano 10 n -6 micro 10 ì -3 milli 10 m -2 centi 10 c -1 deci 10 d 1 deka 10 da 2 hecto 10 h 3 kilo 10 k 6 mega 10 M 9 giga 10 G 12 Tera 10 T 15 Penta 10 P 18 exa 10 E 1. Converting like units a. Combine a prefix with a basic unit results in a statement of a specific length, weight or volume b. Most conversions within the metric system occur in units of TEN where changing a unit of measure to a higher or lower designation requires moving the decimal one place either to the left or to the right. When converting measures in either the high end of the scale (example kilo to mega) or the low end of the scale (examples milli to micro, micro to nano, etc.) the decimal must be moved three places right or left as the prefix designations are assigned only to every third unit in the extreme ends. femto pico nano micro milli centideciunitdekahectokilo mega c. Rules for converting units of measure in the range between milli and kilo (1) To change a unit of measure to the next larger unit; multiply by 0.1 OR move the decimal one place to the left (2) To change a unit of measure to the next smaller unit; multiply by 10 OR move the decimal one place to the right MLAB Clinical Chemistry Basic Principles 2

3 2. Scientific notation 3. Chemistry calculations a. Temperature (1) Scientific measurement of temperature is always expressed in the Celsius ( C) scale, not Fahrenheit ( F ) (2) Measurement of temperature is an important component of the clinical lab. Instruments, refrigerators and incubators are required to operate within specific temperatures that must be maintained and monitored. (3) Each laboratory must have a NIST calibrated thermometer in order to ensure the accuracy of other thermometers in the laboratory (4) Celsius scale: 0 degrees = freezing point of water 100 degrees = boiling point of water (5) Conversion of Celsius to Fahrenheit and Fahrenheit to Celsius F = ( C x 1.8 ) + 32 Or sometimes written: Centigrade to Fahrenheit (9/5 C) + 32 = F Or: C = ( F - 32 ) 1.8 Fahrenheit to Centigrade 5/9(F - 32) = C b. Solutions (1) Solutions are mixtures of substances. (2) Dispersed phase - the substance is dissolved (3) Concentration - c. Expressing concentration (1) The concentration of a solution refers to the weight or volume of the solute present in a specified amount of the solvent or solution (2) Examples (a) Percent solution (parts/100) i) % w/w a) weight to weight b) solid mixed with a solid c) example units: gm/gm, mg/gm ii) % w/v a) weight to volume b) solid in a liquid c) example units: mg/dl, gm/l MLAB Clinical Chemistry Basic Principles 3

4 iii) % v/v a) volume into a volume b) liquid diluted in another liquid c) example units: ml/l d) Note: volumes of liquids are not necessarily additive * (b) Molar solutions * (c) Molal solution i) number of moles of solute in 1 liter of solution ii) a mole is obtained from the molecular or formula weight i) rarely used ii) number of moles added to 1,000 grams of solution (d) Normal solutions i) number of equivalent weights in 1 liter of solution ii) equivalent weight is obtained from the molecular weight divided by the positive valence of the compound iii) working with normality is most important when dealing with acids or bases in neutralization reactions iv) conversions and tips a) N=M x valence b) M=N / valence c) M is always N d. Calculation tips (1) Use ratio and proportion when NOT changing concentration. calculations (2) For calculations changing concentrations, use:v C = V C (3) While you can always make a dilution; you can never make a solution more concentrated. e. Titration Method of measuring concentration of one solution by comparing it with a measured volume of a solution whose concentration is known. General formula: MLAB Clinical Chemistry Basic Principles 4

5 f. Dilution The ratio of the concentrate to the total (final) volume Example 1: Procedure result exceeds linearity. 1 part serum 1 serum 1 X = parts diluent 4 total = X 4 parts total After running the diluted specimen (and determining its concentration) multiply results X 4 Figuring series of dilutions. Another Example 6 tubes, each has 0.5 ml DI water Into first tube, place 0.2 ml serum, and serially dilute. g. Hydrate When a chemical (reagent) comes in a hydrated form (i.e., CuSO 4! 5H2O), the weight of the water must be taken into account when figuring the gram molecular weight h. Density An expression in terms (usually) of a mass per unit of volume MLAB Clinical Chemistry Basic Principles 5