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Molecular analysis (Instrument Methods of Analysis) Essay Example

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Molecular analysis (Instrument Methods of Analysis)

The mass spectrum above was obtained by chemical ionization and shows one of the metabolites of cocaine. The principal higher mass ions seen are at m/z = M+Na+, M+H+ and at 168). Identify the metabolite and briefly highlight the benefits of chemical ionization over electron impact ionization (five marks).One of the benefits of chemical ionization over electron impact ionization is that the former is a lower energy alternative to the latter. In addition, chemical ionization is considered a softer ionization method as compared to the electronic impact ionization, which releases a lot of energy.Cocaine is, in part, metabolised in the liver to benzoylecgonine (BZE) and ecgonine and these molecules are excreted in urine. Only 1–9% of a cocaine dose is excreted in urine unchanged, while 35–54% and 32–49% is excreted as the metabolites BZE and ecgonine methyl ester, respectively. Hence a mid-range value of 45% is identified for BZE and it is scaled up to give a figure for the amount of cocaine consumed.Benzoylecgonine (ecgonine benzoate) is a metabolite of cocaine hence possesses a slightly different chemical structure from cocaine though with a lot of similarities. Notably, benzoylecgonine is the hydrolyzed form or product of cocaine hence it is a carboxylic acid while cocaine is a tropane alkaloid. Whereas the molar mass for benzoylecgonine is 289, cocaine’s molar mass is 303. Based on this benzoylecgonine is more polar than cocaine given the hydrogen atoms lost during the hydrolysis process that leads to the formation of the metabolite benzoylecgonine.Different methods can be used to back-calculate the amount of consumed cocaine from concentrations of cocaine and its metabolites in influent wastewater. The following is based on the concentration of BZE, the major metabolite of cocaine, which is present in wastewater at relatively high concentrations. From concentrations of BZE (ng/L) and with the flow rate (L/day) of the wastewater stream, BZE loads (g/day) can be calculated. These loads are then further transformed into an amount of cocaine consumed (g/day) taking into account the molecular mass ratio of cocaine to BZE (1.05) and the mid-range excretion percentage of 45% as BZE. These two factors are combined to give a value of 2.In the box below show data to confirm that, by taking the mid-range excretion percentage of 45% benzoylecgonine, it is possible to

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preview essay on Molecular analysis (Instrument Methods of Analysis)
  • Pages: 4 (1000 words)
  • Document Type: Essay
  • Subject: Environmental Studies
  • Level: Undergraduate
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