6. Electrolytes

Question 1

Anion gap formula

Answer 1

AG = Na - (Cl + HCO3)

Question 2

The potential difference between 2 electrodes is proportional to ____________

Answer 2

ionic activity of a specific analyte

Question 3

CO2 ISE membrane

Answer 3

Silicone rubber or Teflon

Question 4

Most common class of potentiometric electrodes used in labs today

Answer 4

Liquid/polymer membrane electrode

Question 5

Least commonly used ISE

Answer 5

Solid state

Question 6

4 causes of decreased anion gap

Answer 6

• Hypoalbuminemia
• Hypergammaglobulinemia
• Increased unmeasured cations
• Increased Cl-

Question 7

Components of a reference electrode?

Answer 7

• Metal-metal salt internal reference element
• Saturated internal electrolyte solution
• Salt bridge junction (connecting internal reference electrolyte solution to external solution)

Question 8

3 potential sources of error with ISEs

Answer 8

• electrodes coated with proteins
• air bubbles from refilling internal solution
• membrane’s outer surface dried out

Question 9

The gold standard for diagnosing cystic fibrosis

Answer 9

Coulometry

Question 10

Composition of silver-silver chloride electrode?

Answer 10

• Silver wire coated w/ AgCl sln

- Immersed in saturated salt sln (KCl)

Question 11

This type of ISE’s membrane made be made of silicone rubber, Teflon, or another polyemeric material

Answer 11

Gas sensing

Question 12

ISE most commonly used for measuring H+ activity

Answer 12

Glass

Question 13

Which ref. electrode is found in almost all ISE systems used in clinical labs

Answer 13

Silver-silver chloride electrode

Question 14

What is coulometry?

Answer 14

Measures quantity of electricity (in coulombs) required to convert the analyte to a different state

Question 15

4 things required for potentiometry?

Answer 15

• reference electrode
• indicator electrode
• ammeter/high-impedance voltmere
• chemical buffers and standards

Question 16

Enzymatic measurement of CO2 is determined by measuring the change in absorbance of what?

Answer 16

NADH at 340 nm

Question 17

Composition of calomel electrode?

Answer 17

• Elemental mercury covered by thin coating of calomel (mercury/mercuric chloride) solid
• Immersed in saturated salt sln (KCl)

Question 18

4 types of ISEs?

Answer 18

• Glass
• Liquid/polymer membrane electrode
• Gas sensing
• Solid state

Question 19

3 components of an ISE?

Answer 19

• Internal reference element
• Standard (known) internal electrolyte sln
• Ion selective membrane

Question 20

Chloride ISE membrane

Answer 20

Ag/AgCl membrane or silver sulfide (Ag2S)

Question 21

Potassium ISE membrane

Answer 21

Liquid-ion exchange membrane containing valinomycin

Question 22

Coulometry mostly measures what?

Answer 22

Cl-

Question 23

Purpose of reference electrode?

Answer 23

Provide constant potential

Question 24

2 most common reference electrodes?

Answer 24

• Calomel electrode

- Silver-silver chloride electrode

Question 25

Sodium ISE membrane

Answer 25

Glass-ion exchange