Magnesium: programming in a semi-auto biochemistry analyzer


Magnesium is an important factor in the body, along with potassium, for many enzymatic and metabolic processes. You can measure the concentration of magnesium by the xylidyl blue method.

A low magnesium level can be an indication of malabsorption syndrome, hyperparathyroidism, diabetic acidosis, etc. Similarly, a high level can be an indication of uremia, chronic renal failure,  glomerulonephritis, etc.

Normal range (Approximate value) of Magnesium

  • Neonates:- 1.2 – 2.6 mg/dl
  • Children:-  1.5 – 2.3 mg/dl
  • Women:-    1.9 – 2.5 mg/dl
  • Men:-          1.8 – 2.6 mg/dl
  • Urine:-        73 – 122 mg/dl (24 hrs collection)
  • CSF:-           2.1 – 3.3mg/dl


  • Wear an apron and surgical gloves before carrying out the measurement.
  • Look for the expiry date of the reagents during purchase and measurement time. Suppliers tend to give you reagent kits with a low expiry interval.
  • Once you open the reagent bottles, the lifespan will decrease. So, look in your reagent kit literature for that.
  • Bring the reagents and samples to room temperature before you can carry out any measurement.
  • Always store reagents in the refrigerator when not in use.

Working principle (xylidyl blue method)

1. Principle reaction 

Magnesium reacts with xylidyl blue in an alkaline solution to form a color complex. The intensity of the color is directly proportional to the concentration of magnesium in the sample.

2. Sample preparation

The table shown below is valid for analyticon, tulip, and diasys. If you have a reagent of any other company then there can be a minor variation in the procedure.

First of all, make a working solution out of the given two reagents. The ratio of their composition will be given in the literature. But, if you have only one reagent besides the calibrator, then that will act as a working solution.

Then add  ‘x’  μl of sample/calibrator to the ‘100x’ μl of working solution. After that, incubate the solution, at 370C, for 5 mins. Then feed the solution in the semi-auto biochemistry analyzer.

In the case of reagent blank, replace the sample/calibrator with the same volume of distilled water. Then follow the above steps from the beginning.

If the concentration of magnesium in the sample is very high (out of range/ non-linear curve) then dilute the solution with 0.9% NaCl or distilled water at the ratio of 1:y. Finally, when you get the result, multiply it with the dilution factor (1+ y).

Programming of magnesium in a semi-auto biochemistry analyzer (xylidyl blue method)

xylidyl blue, magnesium

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