This is my first time to write a blog. If it was not part of my busy school life I don’t think I even have the time for writing and blogging. One more thing, writing isn’t really my forte so I hope you guys can bear with me.
FIRST BLOG –hope it’s informative enough for you guys…..
What is magnesium anyway? Is it that important?
Magnesium is the fourth most abundant cation in the human body. Majority of magnesium may be found in the bone. It can also be found in the muscles, soft tissues and blood. Magnesium is an essential element in the body. It is a cofactor for several enzymes in the body. Thanks to it, we are able to function and live normally. Magnesium has been found to have a significant relationship with metabolic, cardiovascular and neuromuscular problems. Therefore the measurement of the increase (hypermagnesemia) and the decrease (hypomagnesemia) in magnesium levels is essential information for the clinician’s diagnosis.
How can magnesium be determined in the body?
Common test used in the clinical laboratory is the colorimetry. Colorimetry makes use of an automated colorimeter. The principle of this method primarily relates the intensity of the color to the concentration of the solution.
Before the test is done, a medical technologist or a phlebotomist will perform venipuncture on the patient in order to withdraw blood. Relax, it wont hurt that much. Magnesium is detectable on blood or specifically in the serum. Nonhemolyzed serum is the preferred specimen in magnesium determination.
There are three common colorimetric methods that are used in magnesium determination. The Calmagite method, as its name implies, makes use of calmagite dissolved in water. It also has other chemicals dissolved together with it.
First, place 50ul of serum in a tube containing 5ml of the reagent. Cover the tube using parafilm and gently mix by inversion. Mg reacts with calmagite to form a red-violet color. The colored solution may be read at 532nm using a colorimeter. The colored chelate is stable for 30 minutes and must be read immediately. The magnesium standard is made by dissolving 44.61g of magnesium iodate tetrahydrate in 1L of water. The use of ethylene glycol tetraacetic acid prevents calcium to bind with calmagite. Cyanide is also present in the reagent to prevent interference of other metals.
Another method is the Formazan dye test. This is a dry-slide method which uses a multi-layered reagent that is magnesium sensitive. It is also imprinted with calcium chelators in order to prevent erroneous results. Magnesium, from the patient’s sample, is dropped on the slide and is evenly distributed to each layer. Magnesium then reacts with the dye. This time, Mg binds with the dye to create a color complex. The amount of colored complex formed is directly proportional to the magnesium present. It is now then measured and is read at 600nm
The reaction sequence of the Formazan dye test maybe simplified by this equation:
Mg2 + Ca+2 = Mg+2 + Ca+2-chelator complex (reaction of the chelator)
Mg+2 + formazan dye derivative = Mg+2-dye complex (reaction of the dye)
The third method, methylthymol blue method, binds Mg with the chromogen to form a blue colored complex. This method is used in the duPont aca using an absorbance of 510nm and 600nm. It is done by mixing 50ul of serum into 2ml of the reagent.
This method makes use of the following reagents:
a. Stock dye (per100ml) contains 18g of methylthymol blue, 0.6g of polyvinyl pyrrolidone , 10ml 1mol HCl
b. Stock base (per 100ml) contains 2.4g of sodium sulfite, 0.1g sodium azide, 750.5mg glycine, 95.1mg ethylene glycol, 10ml 1mol NaOH
The normal range for Mg using these tests is 0.63-1.0 mmol/L (1.2-2.1 mEq/L)
Ooops! Be sure to observe these precautions and limitations before the tests
Always wear your PPE. The remember each specimen is considered infective. Also NEVER EVER let your specimen be contaminated.
Hemolyzed serum should be avoided when performing the tests. This is because the Mg concentration in the RBC is 10 times greater than its extracellular environment. Therefore if these “excess” Mg escapes the cell, it would falsely increase the Mg levels.
Anticoagulants, such as oxalates and EDTA should be avoided because they bind to Mg.
HCl treated 24-hour urine is preferred for analysis. It is acidified with HCl to prevent precipitation.
The tests do not reflect the active free ionized Mg because 25% of Mg found in the body is bound with proteins.
The tests do not also reflect the intracellular amount of Mg.
References:
Clinical Chemistry: Principles, Procedures and Correlations, 5th ed., Michael L. Bishop, et. al, 2005
http://www.clinchem.org/cgi/reprint/33/4/614/b
November 15, 2012 at 9:11 AM
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November 28, 2019 at 8:13 AM