Analysis of the steroid, nandrolone, in urine Free Essay Example, 1000 words

If GC/MS in electron ionization is used exclusively in selected ion monitoring, it can result in misidentification and poor quantification because of interference from same m/z value compounds in the matrix. One method to improve selectivity and sensitivity of the test is to use positive chemical ionization with ammonia as reagent (Wuest, 2004). Instrumentation The analysis of the metabolites can be performed by gas chromatography–mass spectrometry. The method of analysis allows both quantification and qualitative analysis. The analyses are performed using a gas chromotography equipped with autosampler and coupled with mass-selective detector. A computer and ChemStation software are employed for instrument control and data processing. Gas chromatography separation can be achieved on 5% phenyl–95% dimethyl-polysiloxane or Phenomenex column. The dimensions of the column which are usually employed are 30 m x 0.25 mm with 0.25-Â µm film thickness. The operation is done with helium inlet pressure of 103 kPa. the temperature programming which will be usually followed is 100 Â °C for 1 min, increased at 16 Â °C/min to 220 Â °C, increased at 3.80 Â °C/min to 270 Â °C, and held for 3 min. We will write a custom essay sample on Analysis of the steroid, nandrolone, in urine or any topic specifically for you Only $17.96 $11.86/pageorder now 1 micro liter of samples of urine should be injected at 270 degree at one minute into as in the splitless mode split-splitless injection port with an inner glass liner which is silanized. the transfer line is heated to 280 degrees. The source of ion is operated at 70eV in the electron impact mode. The analysis should be performed in single-ion monitoring mode. For [12C] nandrolone, ions m/z 420, 405, and 315 must be used and for [13C] nandrolone, m/z 422, 407, and 317 must be used. For [12C] nandrolone, m/z 405 can be used for quantification and 407 for [13C] nandrolone (Baume et al, 2004). Figure. 3. Mass spectra of 12C-NA (A) and 13C-NA (B) bis-trimethylsilyl derivatives (Baume et al, 2004). Along with performance of these qualitative and quantitative tests, specific gravity of the urine sample also must be checked. If the value is less than 1.02, then no correction is required. If the value is above 1.02, a correction threshold must be made using the formula (WADA, 2004). Threshold1.020 ng/mL= (Specific gravity of the Sample – 1) / (1.020 – 1) * 2 ng/mL If steroids are analysed by positive chemical ionisation, the GC/MS system must be able to provide precise control of GC carrier gas, accurate and reproducible temperature ramping of the oven, stable and controllable source of ion and temperatures of quadrupole and precise and stable reagent gas control.