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.
Concentration of coloured product /10-3 mol dm-3 |
1.00 |
1.50 |
2.00 |
2.50 |
Absorbance |
0.153 |
0.227 |
0.310 |
0.390 |
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?
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