Can we trust mass spectrometry for determination of arsenic peptides in plants:comparison of LC-ICP-MS and LC-ES-MS/ICP-MS with XANES/EXAFS in analysis of Thunbergia alata

The weakest step in the analytical procedure for speciation analysis is extraction from a biological material into an aqueous solution which undergoes HPLC separation and then simultaneous online detection by elemental and molecular mass spectrometry (ICP-MS/ES-MS). This paper describes a study to determine the speciation of arsenic and, in particular, the arsenite phytochelatin complexes in the root from an ornamental garden plant Thunbergia alata exposed to 1 mg As L(-1) as arsenate. The approach of formic acid extraction followed by HPLC-ES-MS/ICP-MS identified different As(III)-PC complexes in the extract of this plant and made their quantification via sulfur (m/z 32) and arsenic (m/z 75) possible. Although sulfur sensitivity could be significantly increased when xenon was used as collision gas in ICP-qMS, or when HR-ICP-MS was used in medium resolution, the As:S ratio gave misleading results in the identification of As(III)-PC complexes due to the relatively low resolution of the chromatography system in relation to the variety of As-peptides in plants. Hence only the parallel use of ES-MS/ICP-MS was able to prove the occurrence of such arsenite phytochelatin complexes. Between 55 and 64% of the arsenic was bound to the sulfur of peptides mainly as As(III)(PC(2))(2), As(III)(PC(3)) and As(III)(PC(4)). XANES (X-ray absorption near-edge spectroscopy) measurement, using the freshly exposed plant root directly, confirmed that most of the arsenic is trivalent and binds to S of peptides (53% As-S) while 38% occurred as arsenite and only 9% unchanged as arsenate. EXAFS data confirmed that As-S and As-O bonds occur in the plants. This study confirms, for the first time, that As-peptides can be extracted by formic acid and chromatographically separated on a reversed-phase column without significant decomposition or de-novo synthesis during the extraction step.

John Rich as Opera Patron

This article traces the sustained support that theatre manager John Rich offered to operatic endeavours in 18th-century London. Rich effectively entered the contemporary discourse regarding the valid definition of opera through the kinds of works he supported, and also through the prefatory comments to two works staged at his theatre.

Race, space and politics in Mid-Victorian Ireland: the ethnologies of Abraham Hume and John McElheran

There has been much scholarly debate about the significance and influence of racialist thinking in the political and cultural history of nineteenth-century Ireland. With reference to that ongoing historiographical discussion, this paper considers the racial geographies and opposing political motivations of two Irish ethnologists, Abraham Hume and John McElheran, using their racialist regimes to query some of the common assumptions that have informed disagreements over the role and reach of racial typecasting in mid-nineteenth-century Ireland. As well as examining in detail the racial imaginaries promulgated by Hume and McElheran, the paper also argues for the importance of situating racialist discourse in the spaces in which it was communicated and contested. Further, in highlighting the ways in which Hume and McElheran collapsed together race, class and religion, the paper troubles the utility of a crisp analytical distinction between those disputed categories.

A pilot study to evaluate aflatoxin exposure in a rural Ugandan population

Objectives: The fungal metabolite aflatoxin is a common contaminant of foodstuffs, especially when stored in damp conditions. In humans, high levels can result in acute hepatic necrosis and death, while chronic exposure is carcinogenic. We conducted a pilot study nested within an existing population cohort (the General Population Cohort), to assess exposure to aflatoxin, among people living in rural south-western Uganda. Methods: Sera from 100 adults and 96 children under 3 years of age (85 male, 111 female) were tested for aflatoxin-albumin adduct (AF-alb), using an ELISA assay. Socio-demographic and dietary data were obtained for all participants; HIV serostatus was available for 90 adults and liver function tests (LFTs) for 99. Results: Every adult and all but four children had detectable AF-alb adduct, including five babies reported to be exclusively breastfed. Levels ranged from 0 to 237.7 pg/mg albumin and did not differ significantly between men and women, by age or by HIV serostatus; 25% had levels above 15.1 pg/mg albumin. There was evidence of heterogeneity between villages (P = 0.003); those closest to trading centres had higher levels. Adults who consumed more Matooke (bananas) had lower levels of AF-alb adduct (P = 0.02) than adults who did not, possibly because their diet contained fewer aflatoxin-contaminated foods such as posho (made from maize). Children who consumed soya, which is not grown locally, had levels of AF-alb adduct that were almost twice as high as those who did not eat soya (P = 0.04). Conclusions: Exposure to aflatoxin is ubiquitous among the rural Ugandans studied, with a significant number of people having relatively high levels. Sources of exposure need to be better understood to instigate practical and sustainable interventions. © 2014 John Wiley & Sons Ltd.