Vanillylmandelic Acid (VMA), 24 Hour, Urine
Method Description Describes how the test is performed and provides a method-specific reference
Hydrophilic-lipophilic balance (HLB) solid-phase extraction (SPE) is performed on an aliquot of urine from a 24-hour collection. The SPE column is eluted with 1 mL of methanol. The eluate is evaporated at 50 degrees C under nitrogen, and the residue reconstituted in 1 mL of the liquid chromatography-tandem mass spectrometry (LC-MS/MS) mobile phase. LC-MS/MS is performed by injecting 10 mcL of the reconstituted specimen onto an amide-C16 HPLC column. The mobile phase (15% methanol in 0.05% aqueous formic acid) is pumped over the HPLC analytical column at a rate of 1.0 mL/min with the flow diverted to the MS/MS electrospray probe tip by 1:5. Vanillylmandelic acid (VMA) elutes apart from the bulk of the specimen matrix at a retention time of approximately 1.5 minutes. VMA is quantitated using a stable isotope labeled internal standard from calibration over a concentration range 1.03 to 20 mg/L.(Magera MJ, Thompson AL, Stoor AL, et al: Determination of vanillylmandelic acid in urine by stable isotope dilution and electrospray tandem mass spectrometry. Clin Chem 2003;49:825-826)
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Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday; 8 a.m.