Claire E. Lenehan

Sequential injection analysis

This article provides a basic overview of the principles of sequential injection analysis. This is followed by a discussion of the instrumental requirements. A brief overview of some of the diverse analytical applications of SIA is also presented.

Optimizing surfactant concentrations for dispersion of single-walled carbon nanotubes in aqueous solution.

The sonication-centrifugation technique is commonly used for dispersing single-walled carbon nanotubes (SWCNTs) in aqueous surfactant solutions. However, the methodologies and materials used for this purpose are widely varied, and few dispersive agents have been studied systematically. This work describes a systematic study into the ability of some well-known (and some less common) surfactants and polymers to disperse SWCNTs fabricated by two different techniques. UV-vis-NIR absorbance spectra of their supernatant solutions showed that the smaller ionic surfactants were generally more effective dispersants, with larger polymer and surfactant molecules exhibiting a reduced performance for ensembles of carbon nanotubes of smaller average diameter. Optimal surfactant concentrations were established for dispersions of carbon nanotubes produced by the electric arc method in aqueous solutions of sodium dodecylbenzene sulfonate, sodium deoxycholate, Triton X-405, Brij S-100, Pluronic F-127, and polyvinylpyrrolidone. This optimum value was determined as the point at which the relative concentration of nanotubes dispersed is maximized, before flocculation-inducing attractive depletion interactions begin to dominate. The aggregation state of carbon nanotubes dispersed in sodium dodecylbenzene sulfonate was probed by AFM at different stages of rebundling, showing the length dependence of these effects.

Comparison of soluble manganese(IV) and acidic potassium permanganate chemiluminescence detection using flow injection and sequential injection analysis for the determination of ascorbic acid in Vitamin C tablets

The limits of detection (3s) for ascorbic acid were 5x10(-8)M with acidic potassium permanganate using both flow injection analysis (FIA) and sequential injection analysis (SIA) whereas the soluble manganese(IV) afforded 1x10(-8)M and 5x10(-9)M for FIA and SIA, respectively. Determinations of ascorbic acid in Vitamin C tablets were achieved with minimal sample pretreatment using a standard additions calibration and gave good agreement with those of iodimetric titration.

Determination of morphine in water immiscible process streams using sequential injection analysis coupled with acidic permanganate chemiluminescence detection

A procedure for the determination of morphine in non-aqueous, water immiscible, process streams by sequential injection analysis is presented. Detection was based upon the chemiluminescence reaction of morphine with acidic potassium permanganate in the presence of sodium polyphosphate, which was carried out in a heterogeneous reaction environment. The calibration graph (range 0.005–0.12% m/v) was non-linear, with a polynomial equation of best fit of y = –384x2 + 139x – 4.84 (R2 = 0.9990), where y represents the singal (mV) and x represents the morphine concentration (% m/v), and was analytically useful over the range 0.01–0.1% m/v. Precision (as measured by relative standard deviation) was 6.0% for 10 replicate analyses of a non-aqueous morphine standard (0.075% m/v).Methyltriphenylphosphonium permanganate was investigated as an alternative chemiluminescent reagent and was found to deliver a similar analytical performance to potassium permanganate. Sequential injection analysis coupled with chemiluminescence detection afforded results for the determination of morphine in non-aqueous process samples which were in good agreement with those obtained using a standard liquid chromatographic method, with an analytical throughput in excess of 120 h–1.

Sequential injection analysis: an alternative approach to process analytical chemistry

Abstract Flow injection analysis (FIA) is well established as a powerful sample handling procedure for laboratory and process analytical chemistry, but the latter application is often hampered by the complexity of the required manifolds particularly for multicomponent analyses. In certain circumstances multicomponent process analytical chemistry is only feasible by utilising several independent FIA systems. This review presents an overview of sequential injection analysis (SIA), which addresses these limitations, and applications of the methodology to the challenging area of process analytical chemistry will be discussed.

Analysis of gold(I/III)-complexes by HPLC-ICP-MS demonstrates gold(III) stability in surface waters.

Understanding the form in which gold is transported in surface- and groundwaters underpins our understanding of gold dispersion and (bio)geochemical cycling. Yet, to date, there are no direct techniques capable of identifying the oxidation state and complexation of gold in natural waters. We present a reversed phase ion-pairing HPLC-ICP-MS method for the separation and determination of aqueous gold(III)-chloro-hydroxyl, gold(III)-bromo-hydroxyl, gold(I)-thiosulfate, and gold(I)-cyanide complexes. Detection limits for the gold species range from 0.05 to 0.30 μg L(-1). The [Au(CN)2](-) gold cyanide complex was detected in five of six waters from tailings and adjacent monitoring bores of working gold mines. Contrary to thermodynamic predictions, evidence was obtained for the existence of Au(III)-complexes in circumneutral, hypersaline waters of a natural lake overlying a gold deposit in Western Australia. This first direct evidence for the existence and stability of Au(III)-complexes in natural surface waters suggests that Au(III)-complexes may be important for the transport and biogeochemical cycling of gold in surface environments. Overall, these results show that near-μg L(-1) enrichments of Au in environmental waters result from metastable ligands (e.g., CN(-)) as well as kinetically controlled redox processes leading to the stability of highly soluble Au(III)-complexes.

The crystal chemistry of Al-bearing goethites: an infrared spectroscopic study

Abstract Aluminium substitution into goethite, α-FeOOH, has been studied systematically by infrared spectroscopy over the frequency interval 150 to 700 cm-1. A range of synthetic compositions, (Fe1-xAlx)OOH, 0 ≤ x ≤ 0.0857, plus end-member diaspore (AlOOH) were examined. The IR spectrum of FeOOH over the range of interest can be deconvoluted into 9 peaks: 670, 633, 497, 451, 409, 396, 360, 290 and 268 cm-1. With addition of Al, the spectra become broader and the frequencies of the modes shift to higher values. An effective line width parameter Δcorr was determined by autocorrelation analysis for each spectrum and there is a significant increase in the Δcorr for compositions with > 5.85 mol.% Al substitution, indicating that there is very significant structural strain associated with this solid solution at compositions where a significant number of Al sites will have an additional Al atom in the first cation coordination sphere. Trends in the values of Δcorr with composition mirrored published enthalpy of mixing values indicating that Al-goethite is metastable with respect to the goethite and diaspore end-members. The role of substitutional strain and possible partial order of Al is briefly discussed.

Extracts from Calendula officinalis Offer in Vitro Protection Against H2O2 Induced Oxidative Stress Cell Killing of Human Skin Cells

The in vitro safety and antioxidant potential of Calendula officinalis flower head extracts was investigated. The effect of different concentrations (0.125, 0.5, 1.0, 2.0 and 5.0% (v/v)) of Calendula extracts on human skin cells HaCaT in vitro was explored. Doses of 1.0% (v/v) (0.88 mg dry weight/mL) or less showed no toxicity. Cells were also exposed to the Calendula extracts for either 4, 24 or 48 h before being exposed to an oxidative insult (hydrogen peroxide H2O2) for 1 h. Using the MTT cytotoxicity assay, it was observed that two independent extracts of C. officinalis gave time‐dependent and concentration‐dependent H2O2 protection against induced oxidative stress in vitro using human skin cells. Pre‐incubation with the Calendula extracts for 24 and 48 h increased survival relative to the population without extract by 20% and 40% respectively following oxidative challenge. The antioxidant potential of the Calendula extracts was confirmed using a complimentary chemical technique, the DPPH● assay. Calendula extracts exhibited free radical scavenging abilities. This study demonstrates that Calendula flower extracts contain bioactive and free radical scavenging compounds that significantly protect against oxidative stress in a human skin cell culture model. Copyright

Evaluation of relative comparator and k 0 -NAA for characterization of Aboriginal Australian ochre

Ochre is a significant material in Aboriginal Australian cultural expression from ceremonial uses to its application on many types of artifacts. However, ochre is a complex material, with associated surrounding minerals potentially challenging the overall analysis. In recent literature several studies have attempted to characterize ochre by a variety of techniques to understand procurement and trade. However, ochre is difficult to differentiate on major elemental or mineralogical composition and requires a detailed analysis of its geochemical “fingerprint”. Neutron activation analysis (NAA) provides the high sensitivity (sub-ppm), precision and accuracy in multi-elemental analysis required for ochre. The elements of interest for ochre generally include rare earth elements (REEs) and certain transition metal elements as well as arsenic and antimony. Data from relative comparator NAA (MURR, University of Missouri, USA) is compared with data from k0-NAA OPAL (ANSTO, Lucas Heights, Australia). A discussion of the two methods will be examined for their utility in “fingerprinting” the provenance of ochre. The continuing importance of NAA to archaeometry will also be discussed.

Preliminary evaluation of dual acidic potassium permanganate and tris(2,2?-bipyridyl)ruthenium(II) chemiluminescence detection for the HPLC determination of Papaver somniferum alkaloids

This paper describes a dual chemiluminescence reagent for the determination of the opiate alkaloids morphine, codeine, oripavine, and thebaine in Papaver somniferum extracts. Detection was achieved using a mixture of acidic potassium permanganate and tris(2,2′-bipyridyl)ruthenium(ii), where the former acted as both the oxidant for the latter and as a chemiluminescence reagent in its own right. The analytes were separated on a C 8 column using ion-pairing HPLC. The application of the mixed reagent detection compared favourably with results obtained using standard HPLC methodology. Detection limits for the alkaloids were 10 -6 , 5 × 10 -7 , 3 × 10 -6 , and 2 × 10 -6 mol L -1 for morphine, codeine, oripavine, and thebaine, respectively.