Chemical speciation through sequential injection analysis

Abstract

This work gives a thorough insight into the objectivity of adapting the sequential injection analysis (SIA) technique as a tool for chemical speciation. The use of ultraviolet visible spectrophotometry as a single detector greatly simplified the analysis process. This work further ascertained the versatility of the SIA system and broadened its scope of application. This was exemplified through Chapters 3, 4, and 5 which focused on chemical speciation of heavy metals. In Chapter 6 a non-metallic speciation was done with special reference to bromine/bromide. The application spectrum of SIA was furthermore displayed in the chemical speciation of α-amylase and β-amylase as examples of biological substances in Chapters 7. Chapter 8 concludes this research by extending this procedure into organic chemical species through speciation of (R and S)-penindopril. Chapter 9 gives an overall conclusion of the chemical speciation project. Table 3.4 shows the recovery of the developed method and for Fe(III) the % recovery was 100 % and for total Fe it was ± 98 %. From Table 3.5 the % relative standard deviation (RSD) was 0.58 and 0.73 for Fe(II) and Fe(III) respectively by the proposed method whereas in comparison Atomic Absorbtion Spectroscopy (AAS) method had 1.67 % and the titration 2.35 %. At the 95 % confidence level tcalculated ≤ ttababulated showing that the standard method and the proposed method yielded similar results. Mn(II)/ Mn(VII) speciation gave similar results as shown in Table 4.3 by statistical evaluation of the results of the proposed method and the standard method. Table 4.4 shows the results of the recovery upon spiking with 0.2 mg Mn (VII) and the average % recovery was 98. Table 4.5 shows simultaneous determination of Mn(II) and Mn(VII) from synthetic samples by SIA method and the % recovery was ± 99 %. The % RSD was 0.27 and 0.34 for Mn(II) and Mn(VII) respectively which shows great precision. Table 5.3 displays simultaneous determination of Cr(III) and Cr(VI) from samples by the proposed SIA method in comparison with the titrimetric and AAS methods and there was no significant difference for all three methods. Table 5.4 shows the results of the recovery upon spiking with 0.4 mg Cr(III) and there was a 98 % recovery. Table 6.4 shows recovery results and in all cases the average % recovery was 98 %. The % RSD values were 0.8 and 0.7 % for bromine and total bromine, respectively (Table 6.3). Using the proposed system, one can monitor both bromine and total bromine at 30 samples per hour with a very low sample carry-over (~ 1.1%). Table 7.4 displays % Recovery after addition of 0.02 fungal amylase unit (FAU) of both α and β amylase and in both cases it was 98 %. The proposed SIA method and the iodine diastatic method gave similar results as shown in Table 7.5. The calculated % RSD was lower than 0.80 showing excellent precision. The detection limit for α- amylase determination was calculated to be 0.0046 FAU within a working range of (0.015 – 0.04) FAU and the corresponding values for β-amylase were calculated out to be 0.0043 FAU with the same working range. Table 8.3 shows the results obtained for the assay of S-perendopril (S-pdp) in the presence of R-perendopril (R-pdp), and the recovery was above 98 %. Table 8.4 shows results obtained for the assay of R-pdp in the presence of S-pdp and with 98 % recovery. This work highlighted the broad spectrum of SIA adapted to chemical speciation.