Description

1.      a)         Compare the instruments used for flame atomic absorption spectroscopy and inductively-coupled plasma atomic emission spectroscopy, commenting on the similarities and differences between the systems.

            b)         An analysis of the active ingredient (B) of a tablet by UV spectrometry was carried out as follows: 2.5436 g of powdered tablet was dissolved in acid

(10 cm3) and the digest diluted to 100 cm3 in a volumetric flask to form the sample solution. A 10 cm3 aliquot of the sample solution was pipetted into a second 100 cm3 volumetric flask along with excess of a reagent which reacted 1:1 with B to form a coloured product and the mixture diluted to volume. A sample of the test solution was placed in a 1 cm pathlength cell and the absorbance measured at 537 nm. This was found to be 0.301. Table 1 shows the absorbance of a series of standard solutions of the coloured product. Using a graphical method, calculate the concentration of B in the test solution and hence, given that the relative molecular mass of B is

265.1 g mol-1, calculate the dose of B administered from a 250 mg tablet made from the powder.

Table 1. Absorbance of standard solutions of B

2.      Describe, with appropriate diagrams, the construction of a Fourier-Transform Infrared (FTIR) spectrometer and discuss the techniques which FTIR has now made routine.

3.      a)           Describe the processes involved in electron impact and electrospray ionisation for analysis by mass spectrometry. What sample types would these two techniques be used for?

  b)           In an experiment using a time-of-flight (tof) mass spectrometer, the following experimental parameters are used: Accelerating voltage (V) = 14000 V; path length (L) = 1.2 m. A protein molecule has a relative molecular mass of

4710 g mol-1 and is ionised by adsorption of ammonium ions (Mr = 18). What would be the predicted detection time if:

                           i)        one (1) ammonium ion and

          ii)       twelve (12) ammonium ions

                                     have been adsorbed to form an ion?

NA = 6.022 x 1023 mol-1

                                    e    = 1.602 x 10-19 C

4.      Fentanyl (Figure 1) is a very potent opioid analgesic and can be detected in the

          sub – ppb to low ppb range following chromatographic separation through a C18 column using reversed phase (RP) HPLC conditions.

Figure 1 – Fentanyl

a)        When fentanyl and the internal standard D5-fentanyl were separated

    using RP-HPLC the retention times of the two components were

    5.0 minutes and 7.0 minutes respectively. The retention time of the mobile

    phase was 1.5 minutes. If the resolution (RS) was 1.5, using a suitable

    expression, calculate the number of theoretical plates required to

    facilitate this separation.

b)        Fentanyl can be routinely analysed using a RP HPLC system linked to

    a MS (ESI) detector. What characteristics must the interface possess if

    it is to adequately link the instrumentation to allow for detection of the

    analyte?

c)         What are the guidelines for method validation that would enable the

    determination of fentanyl (and its derivatives) using RP HPLC?