Magnesium is the second most abundant intracellular cation after potassium and is essential for many metabolic reactions as a cofactor for DNA, RNA, polyphosphate processes related to ATP, and chlorophyll. Magnesium compounds serve as laxatives, neutralizers, and to regulate abnormal nerve stimulation and vascular eclampsia stability.

Magnesium levels are low in malabsorption syndrome, diuretics, aminoglycoside therapeutics, hyperparathyroidism, and diabetic acidosis. They are high in uremia, chronic renal failure, glomerulonephritis, Addison's disease, and anti-acid therapy.

This method determines the magnesium concentration by observing the color change in the visible region by the formation of a chelate complex between Xyridyl Blue-I (XB-I) and magnesium.

Xyridyl Blue-I forms a complex with magnesium under alkaline conditions, and changes color from purple to red. This Mg-XB-I complex increases absorbance at 520 nm, while the absorbance from XB-I at 600-680 nm decreases. The magnesium concentration can be determined by observing this change in absorbance.

◯ Samples that can be directly quantified with this kit

Examples: serum, plasma

The denaturant in the kit dissociates magnesium from the protein and develops color after reducing agent reduces it. No specific pretreatment is required.

※ Do not use blood collection tubes containing EDTA which may affect the assay value.

◯ Samples that require dilution

Example: Urine

There is a possibility that the measurement range will be exceeded so dilute samples to 2x for measurement.

※ If using urine as a sample, preserve it by adding hydrochloric acid. When measuring, adjust the pH to 2~3.

※ The components of urine change from time to time, so the dilution ratio may vary. Be careful especially with the dilution ratio for early morning urine.

※ If you dilute a sample, be careful not to forget to multiply the dilution ratio when calculating the concentration.

◯ Samples that require acid extraction

Examples: cell lysates, tissue homogenates, and other aqueous solution samples

The pH of the samples was adjusted to low level to dissociates the magnesium from the protein, and the supernatant was used as the assay sample. However, only the following chemicals can be measured.

・Free magnesium

・Protein-bound (coordinated) magnesium (Protein-Mg2+, e.g. albumin)

・Other coordination-bound magnesium

※ Do not use lysis buffers containing EDTA as they may affect the measured values.

※ Acid digestion should be performed in the case of organic magnesium.

◯ Samples that require microwave method and organic matter mixed acid decomposition

Example: Samples containing strong chelating agents such as EDTA, organic magnesium (-C-Mg-C- single bonded), or magnesium encapsulated in a cyclic ligand.

Acid extraction is necessary when measuring chemical species that cannot be dissociated or samples containing interfering substances such as strong magnesium chelating agents.

※ After decomposition of organic matter, adjust the pH to 2-3, and use the sample as the assay sample.

(1) Add 3 µl of DIW, standard solution, and assay sample to wells of a 96-well plate.

(2) Add 250 µl of RA solution to each well

(3) Incubate the plate at room temperature for 5 minutes.

(4) Measure absorbance at main wavelength 660 nm.

(5) Calculate the magnesium concentration using the following formula:

(1) Measurement of magnesium concentration in control serums using this kit

Figure 1: Results of measurement of control serum with known magnesium concentration.

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