Lecture 2
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What is the difference between and single beam and double beam Spectrophotometers?
Double beam has a chopper that splits the light into 2 different portions into 2 separate cuvette.
What is the advantage of a double beam Spectrophotometers?
equivalent to having two identical spectrophotometers: one for measuring I and one for Io This allows Abs values to be collected at different wavelengths without needing to rescan allows for quick collection of an Absorption spectrum
Spectrophotometer with a photodiode array detector
Light is not separated into different wavelengths until after it goes through sample Monochromator positioned after the light has passed through sample
why does Spectrophotometer with a diode laser light source does not need a monochromator?
Laser puts out light that is such a narrow range of wavelengths it is often described as a single wavelength
What is the advantage of a Spectrophotometer with a diode laser light source?
small inexpensive spectrophotometers
What is the disadvantage of a Spectrophotometer with a diode laser light source?
the instrument can only measure at the wavelength or wavelengths that it has laser lines at
Bandpass
The range of wavelengths that are measured together as a group in a spectrophotometer
Osmoles
all of the moles that contribute to osmotic pressure
Which compounds can dissolve into ions
Acids and ionic compounds Not molecular compounds
Hypertonic solution
cell in a hypertonic solution, lower concentration ions in cell H20 leaves cell Cell shrivels like a raisin
Hypotonic solution
higher concentration of ions inside cell H2O enters cell Cell inflates and bursts
Osmolarity
refers to the number of solute particles per 1 L of solvent Temperature dependent Osmolarity = osmoles/liter
Osmolality
refers to the number of solute particles in 1 kg of solvent Independent of freezing point depression
Freezing point depression
T=Kfm
Serum Osmotic Gap
Measured Osmolality – Estimated Osmolarity
Measured Osmolality
Measured by T/Kf
Estimated Osmolarity
2*sodium (most important) Glucose BUN Measured in in routine blood tests
Abnormally high blood osmolality
dehydration, hypernatremia head trauma hyperglycemia, diabetes insipidus uremia poisoning from ethanol, ethylene glycol, or methanol accumulation of toxins in the patient’s blood
Abnormally low blood osmolality
excess fluid intake or over hydration, hyponatremia/ or low blood sodium, paraneoplastic syndromes; a type of disorder that affects some people with cancer, syndrome of inappropriate ADH secretion (Anti-Diuretic Hormone)
Serum Osmotic Gap: Facts
Values up to 10 are borderline normal normal gap reflects all other substances that are dissolved in the serum but that are not routinely measured
Serum Osmotic Gap: Over
Values >10 reflect dissolved substances of low molecular weight- such as: Drinking alcohol, Solvents from poisoning
Sodium ions
The major extra cellular cation Absorbed passively and excess- excreted by kidneys Parallels Cl- concentration in healthy individuals affected by diarrhea/vomiting, excessive sweating
Potassium ions
K+ higher inside cells
High K+ in blood (outside reference range) can indicate
Renal failure Releases K+ creating false high K+ levels Poor technique in blood collection, sample not centrifuged within timely fashion