Lab Exam 2
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What are the laboratory methods for detecting calcium?
-redox titrations -spectrophotometric titrations -spectrophotometric -atomic absorption -ion selective electrodes
What all use atomic absorption as the reference method?
-calcium -magnesium -potassium -sodium *most often just used for Ca and Mg
Old method for calcium that is no longer used. total calcium is precipitated as calcium ___________. how is it dissolved?
oxalate, acidification
With calcium redox titration, the resulting oxalic acid is titrated against ______________ in a redox reaction and the electrical current is monitored.
potassium permanganate
detection of fluorescence emitted from the calcien-calcium complex formation.
Calcium: Spectrophotometric Titration: Calcien-Calcium Fluorescence
Calcium: Spectrophotometric Titration: Calcien-Calcium Fluorescence the fluorescent complex is titrated with _______ (calcium chelator)
EGTA *volume of added EGTA directly proportional to calcium
what interferences are there with Calcien-Calcium Fluorescence?
no interference from magnesium and phosphate
Calcein-Calcium Fluorescence is useful in Stat labs. Research labs routinely use _______, _______, _______ complexes with calcium-binding domains.
Flura-2, Fluo3, FRET
Calcium: Spectrophotometric Titration: Calcein-Calcium Fluorescence the fluorescent complex is titrated with _______ (calcium chelator)
EGTA *volume of added EGTA directly proportional to calcium
What are the two types of Calcium spectrophotometric titration colorimetric methods?
-O-Cresolphthalein -Methylthymol blue
Calcium spectrophotometric titration colorimetric methods: O-Cresolphthalein method, calcium complexes with o-cresolphthalein in _______________ conditions
alkaline (around 12 pH)
What is added for the O-Cresolphthalein method (Calcium) that chelates Mg and increases the specificity?
*5-hydroxyquinolone
O-Cresolphthalein calcium method forms a highly colored complex that is measured at ______ nm.
580
Calcium: Spectrophotometric titration colorimetric methods: Similar principle to O-Cresolphthalein what is it measured at?
Methylthymol Blue 610 nm
Calcium: Spectrophotometric titration colorimetric methods: what are other reagents that can be used?
alizarin, calcein plasmo-corinth B, GBHA (glyoxaldis-(2-hydroxyanil)
most calcium is in the ionized form. Which method measures TOTAL calcium?
Atomic Absorption*
Most accurate method reference method for calcium
Atomic Absorption*
is Atomic Absorption a direct or indirect method?
indirect -sample is diluted -needs monochromator
Why is lanthanum-Cl used in calcium atomic absorption?
to bind interfering substances
Calcium: Atomic Absorption: Serum diluted into ________________
lanthanum-Cl
The most commonly used method for Calcium
Calcium: Ion Selective Electrode Potentiometry
Detects ionized Ca2+ with ion selective electrode (ISE) ! Sensor solvent mediator system ❖ Sensor either an ion exchanger or neutral carrier ➡ selection based on charged and steric factors ❖ Solvent mediator disperses sensor evenly in polyvinyl chloride matrix ❖ Ca2+ binding to sensors develop electric potential across membrane
Calcium: Ion Selective Electrode Potentiometry
Calcium: Ion Selective Electrode Potentiometry: Solvent mediator disperses sensor evenly in _______________ matrix ❖ Ca2+ binding to sensors develop electric potential across membrane
polyvinyl chloride
What specimen should be used for calcium?
Serum, plasma, or whole blood For whole blood: using Ca2+-titrated heparin