Rapid detection of diuretics by atmospheric pressure chemical ionization (apci) tandem mass spectrometry
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Date
2003
Authors
Muhamad Noh, Hayati
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Abstract
Diuretics are banned by the International Olympic Committee (IOC) in sport. The IOC
requires mass spectra of at least three diagnostic ions to confirm a positive urine. The
cmTent detection method by gas chromatography-mass spectrometry (GC-MS) utilizes
derivatization and sample clean-up procedure, which in most instances is a timeĀ·
consuming step. The recent development of liquid chromatography (LC) tandem mass
spectrometry has demonstrated the capability of detecting a number of drugs; however
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the sample clean-up procedure applied to the urine samples is still a time consuming
step. A simplified sample preparation followed by detection using LC tandem mass
spectrometry was investigated in this study. Atmospheric pressure chemical ionization
(APCI) was selected for detection using selected reaction monitoring (SRM) in negative
ion mode. The mobile phase containing acetonitrile and 0.05 M ammonium acetate with
0.1% triethylamine (TEA), adjust~d to pH 6.6 established constant ionization conditions
for all compounds. Fast gradient elution was accomplished with five minutes run time
and a total of eight minutes of analysis cycle time and the diuretics were well separated
by their masses. The divert valve on the instrument assist in preventing premature
contamination from the early elution. The quadrupole mass analyzer ,parameters
including scan speed, resolution, multiplier gain and tube lens were further optimized.
Throughout the method validation period, diuretics were detected at the limit of
detection of 0.1 ~tg/mL as set by the IOC. All diuretics were also detected by selected
ion monitoring (SIM) at the first quadrupole (Ql); however, the urine matrix was
subjected to liquid-liquid acidic extraction prior to analysis. The full scan MS/MS
product ion spectra demonstrated the capability to confinn the positive urine and can be
extended to produce at least three diagnostic ions within 20% relative abundance to
fulfil the criteria set by the IOC. The X-calibur program incorporated into the analysis
method produces results automati-cally following completion of the analysis. The
printed results in concise macro windows assisted in the interpretation of data,
consistent with standard IOC screening procedures.
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Keywords
Atmospheric pressure , Spectrometry