Analytical Flashcards
What is the gold standard method for separating MacroPrl and Prolactin?
Gel filtration chromatography
What are the mechanisms by which lipaemia causes interference? (name 4)
- Spectrophotometric interference (light absorption and light scattering)
- Volume depletion effect (e.g. pseudohyponatreamia)
- Partitioning of the sample
- Physicochemical mechanisms (e.g., disturbance of the electrophoretic pattern).
Methods for removing lipids from a lipaemic sample?
- Ultracentrifugation or high speed centrifugation
- Lipid clearing agents such as Lipoclear
Reaction catalysed by CK used in enzymatic method?
Creatine phosphate + ADP –> Creatine + ATP
In the enzymatic spectrophotometric method of bicarbonate measurement, PEPC catalyses the reaction of HCO3- + PEP to form ___ ?
Oxaloacetic acid
The enzyme PEPC is involved in the spectrophotometric method of bicarbonate measurement. What does PEPC stand for?
Phosphoenolpyruvate carboxylase
Approximately how much CO2 is lost from uncapped tubes per hour?
4mmol/L
What can interfere with the paracetamol enzymatic assay?
N-acetylcysteine
Salicyclic acid
What is the method used for paracetamol measurement?
Enzymatic/colourimetric using aryl acylamidiase
What issue can occur with creatinine measurement in the setting of paracetamol OD?
Therapeutic concentrations of NAC can interfere with the Cr enzymatic method
Method for ethanol measurement?
Enzymatic method using alcohol dehydrogenase
In scanning spectroscopy in investigating for CSF bilirubin, at what wavelengths do the peaks for oxyhaemoglobin and bilirubin occur?
Oxyhaemoglobin peak 415nm
bilirubin peak 476nm
What are the different fractions of bilirubin
Unconjugated (alpha)
Conjugated: mono (beta) and di (gamma)
Delta bilirubin: covalently bound to albumin
Reference method for bilirubin measurement
Modified Jendrassik and Grof
- Caffeine-benzoate-acetate accelerator
Name 6 methods for bilirubin analysis
- Chemical (diazo reaction)
- Direct spectrophotometry
- Enzymatic (oxidation)
- HPLC
- Scanning spectrophotometry (CSF)
- Reflectance (transcutaenous bilirubin)
What can cause interference in Diazo reaction for bilirubin measurement
Haemolysis
Lipaemia
Paraproteinaemia
What is the pKa of bicarbonate?
6.1
What will happen to the pH of sample if the specimen is left uncapped?
pH will increase
Loss of CO2 from sample into room air
What is the difference between actual and standard bicarbonate measurements on blood gas machine?
Actual bicarbonate is a derived measurement calculated from pH and pCO2 on anaerobically collected sample.
Standard bicarbonate indicates bicarbonate level at 37C and pCO2 of 40mmHg
Osmolality is a _______ property of solutions that depends on the number of dissolved particles present in the solution
Colligative
As the number of dissolved particles in a solution increases, the freezing point and vapour pressure of a solution will ________
decrease
Formula for calculating urine osmolality
= 2 x (Na + K) + urea
Interferences in osmolality measurement
Citrate can increased measured osmolality
Any particular matter (e.g. microclots in serum/plasma)
Interferences in analytical measurement of iron?
Chelators (e.g. EDTA, citrate)