Validation of an updated fractionation and indirect speciation procedure for inorganic arsenic in oxic and suboxic soils and sediments.

A sequential extraction procedure (SEP) for the speciation analysis of As(III) and As(V) in oxic and suboxic soils and sediments was validated using a natural lake sediment and three certified reference materials, as well as spike recoveries of As(III) and As(V). Many of the extraction steps have been previously validated making the procedure useful for comparisons to similar previous SEP studies. The novel aspect of this research is the validation for the SEP to maintain As(III) and As(V) species. The proposed five step extraction procedure includes the extraction agents (NH4)2SO4, NH4H2PO4, H3PO4 + NH2OH·HCl, oxalate + ascorbic acid (heated), and HNO3 + HCl + HF, targeting operationally defined easily exchangeable, strongly sorbed, amorphous Fe oxide bound, crystalline Fe oxide bound, and residual As fractions, respectively. The third extraction step, H3PO4 + NH2OH·HCl, has not been previously validated for fraction selectivity. We present evidence for this extraction step to target As complexed with amorphous Fe oxides when used in the SEP proposed here. All solutions were analyzed on ICP-MS. The greatest concentrations of As were extracted from the amorphous Fe oxide fraction and the dominant species was As(V). Lake sediment materials were found to have higher As(III) concentrations than the soil materials. Because different soils/sediments have different chemical characteristics, maintenance of As species during extractions must be validated for specific soil/sediment types using spiking experiments.

A case-control study investigating factors of preoperative delay in emergency laparotomy.

BACKGROUND: Emergency laparotomy (EL) is a procedure that puts a strain on healthcare resources and is associated with a significant morbidity and mortality. Despite these implications little improvement in the outcome of patients undergoing this procedure has been made in the UK over the last few decades. A delay in transferring patients to theatre has been shown to negatively affect outcome of EL. A prospective case-control study was carried out to evaluate which preoperative factors may contribute towards a delay in theatre transfer. METHODS: The time between decision to operate and anaesthetic start time was recorded for all patients undergoing EL between April and September 2013 at Gloucestershire Royal Infirmary. Patient selection criteria were based on the National Emergency Laparotomy Audit guidelines. Patients were divided into two groups depending on whether the transfer to theatre was delayed or not. Binary logistic regression analysis was performed on perioperative factors to determine independent predictors of delay. RESULTS: A total of 84 EL were included for analyses with 31 classified as delayed. In the delayed group time for theatre transfer was increased at 6.9 vs. 2.3 h (p < 0.005) respectively. Unavailability of emergency theatres due to other cases taking priority was the most frequent cause for delay (n = 24). On binary logistic regression analysis, indication for laparotomy (OR 4.96, CI 1.4-17.6, p < 0.05), patient age (OR 1.04, CI 1.00-1.07, p < 0.04) and presence of a consultant surgeon (OR 0.16, CI 0.03-0.79, p < 0.03) were found to be independent predictors of delay in EL. CONCLUSION: In this study, factors that were associated with a delay in commencing EL were operative indication and patient age whereas the presence of a consultant surgeon made a delay less likely. These findings may highlight points of interest for researchers analysing and auditing the provision of EL in the UK.