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Test Code LAB406 Magnesium - 24 Hour Urine

Department

CHEMISTRY

Collection Requirements

24 hour urine.

Do not add preservatives to the collection container.

Keep the container on ice or refrigerated during collection.

Primary Collection Container

24 HR Urine container

Transport

Urine refrigerated

Preferred Transport Temperature

Refrigerated

Processing

Measure total volume.

Adjust pH to less than 3 with 6N HCl.

Aliquot, centrifuge and refrigerate.

Note total volume and PH on the label.

Stability

Ambient: 1 week

Refrigerated: 1 week

Minimum Testing Volume

0.1 mL

Reference Range

74 – 124 mg/24hr

Methodology

The magnesium method is a modification of the methylthymol blue (MTB) complexometric procedure described by Connerty, Lau, and Briggs. MTB forms a blue complex with magnesium. Calcium interference is minimized by forming a complex between calcium and Ba-EGTA (chelating agent). The amount of MG-MTB complex formed is proportional to the magnesium concentration and is measured using a bichromatic (600 and 510 nm) endpoint technique. Siemens Dimension Vista.

Performed

Sunday – Saturday

Reported

As completed

CPT Codes

83735

Unacceptable Conditions

Urine not acidified.

Additional Information

Other acceptable preservative is KBS.

pH must be <4.0.