Babajide I. Alo

Comparison of three sequential extraction protocols for the fractionation of potentially toxic metals in coastal sediments

In the determination of the best sequential extraction procedures (SEP) for the speciation of metals in sediment samples from the Lagos lagoon system, three sequential extraction procedures were compared for the fractionation of Cd, Cr, Cu, Pb, and Zn. The SEP compared included a modified Tessier’s procedure carried out in five steps, while the two other procedures were the three-step original Community Bureau of Reference (BCR) and the modified BCR techniques (four steps). Quantification of the metal concentration was achieved with a flame atomic absorption spectrophotometer. The results obtained by the three methods were compared, and the modified BCR and Tessier SEP were found to extract more Cu, Cr, Pb, and Zn in the reducible phase and therefore a decrease in the oxidizable phase than the original BCR SEP. The most mobile elements were found to be Cd, Pb, and Zn. These are of environmental concern, as these potentially toxic metals could be easily released into the aquatic environment with consequent ingestion by aquatic organisms, thereby entering the food chain. The mass balance (percent recovery) was found to be between 85% and 115% in most cases. Prior to the comparison, the analytical performance of the laboratory was tested using a secondary reference material, GLAURM, using the three-step modified BCR procedure. The results showed high reliability of the analytical performance of the laboratory for all the metals considered.

NEW SYNTHESES OF THE MARINE ALKALOIDS EUDISTOMINS D AND U

Abstract Short and convergent syntheses of eudistomins U and D are reported. The approach is based on a convergent methodology which involves such reactions as metalation and heteroring cross-coupling.

Profile of medical waste management in two healthcare facilities in Lagos, Nigeria: a case study

Proper management and safe disposal of medical waste (MW) is vital in the reduction of infection or illness through contact with discarded material and in the prevention of environmental contamination in hospital facilities. The management practices for MW in selected healthcare facilities in Lagos, Nigeria were assessed. The cross-sectional study involved the use of questionnaires, in-depth interviews, focused group discussions and participant observation strategies. It also involved the collection, segregation, identification and weighing of waste types from wards and units in the representative facilities in Lagos, Nigeria, for qualitative and quantitative analysis of the MW streams. The findings indicated that the selected Nigerian healthcare facilities were lacking in the adoption of sound MW management (MWM) practices. The average MW ranged from 0.01 kg/bed/day to 3.98 kg/bed/day. Moreover, about 30% of the domestic waste from the healthcare facilities consisted of MW due to inappropriate co-disposal practices. Multiple linear regression was applied to predict the volume of waste generated giving a correlation coefficient (R2) value of 0.99 confirming a good fit of the data. This study revealed that the current MWM practices and strategies in Lagos are weak, and suggests an urgent need for review to achieve vital reversals in the current trends.

Abereamines, water-soluble seed alkaloids from Hunteria umbellata

Abstract The isolation and characterization by spectroscopic methods of four isomeric 14-isopropyl-dihydroxydeoxyisocorymines with the lactone bridge open are described. These are water-soluble alkaloids named abereamines from the seeds of Hunteria umbellata .

Carbolines, Part VIII. An Original Synthesis of the Antibiotic Eudistomin T

Abstract An original and short synthesis of Eudistomin T is reported. The approach is based on a convergent methodology which involves such reactions as metalation, heteroring cross-coupling and cyclization.

The contribution of roadside soil to phosphorus loading in the eutrophic Lagos Lagoon, Nigeria

Roadside soils were sampled from the Lagos Lagoon catchment during the wet and dry seasons over the period 2005-2009. Lagoon sediment samples were also collected within the same period. All samples were digested with aqua regia to determine total phosphorus and extracted with 0.5 M sodium bicarbonate to determine the bioavailable fraction (Olsen-P). A segmented flow analyser method was used for analysis and good accuracy was demonstrated for two reference soils (SO-2 from CCMET and SRM 2711 from NIST). The Lagos Lagoon is a hypereutrophic water body (1270 ± 1170 μg P L(-1)), with significant areas of anoxia and water hyacinth growth. The total phosphorus concentrations in roadside soils (16 sites; mean ± 2 S.D.) were 285 ± 279 mg kg(-1) in the wet season and 424 ± 629 mg kg(-1) in the dry season, indicating that rainwater leaching is a major source of phosphorus in the lagoon. The bioavailable fractions were 5.17 ± 3.47 mg kg(-1) (2.1 ± 1.5% of the total) in the wet season and 13.0 ± 8.7 mg kg(-1) (4.3 ± 4.5% of the total) in the dry season.

Use of the nuclear Overhauser effect in the determination of the orientation of aromatic substitution in tricyclic quinoxalinones

1 H N.m.r. nuclear Overhauser enhancement studies involving the amide NH of 7,8,9,10-tetrahydropyrido[1,2-a]quinoxalin-6-ones have been used to identify the aromatic proton signals of the quinoxalin-6-ones and to show that bromination with bromine in glacial acetic acid takes place at C-3 whilst nitration with potassium nitrate–concentrated sulphuric acid takes place at C-2.

Synthesis of 1,2,4-benzothiadiazines via readily generated iminium ions

A general method for the regiospecific synthesis of 1,2,4-benzothiadiazines, which are powerful diuretics and antihypertensive agents, has been developed. The N-arysulphonylprolyl chlorides (5)–(7) reacted instantaneously with silver trifluoromethanesulphonate at room temperature to give the iminium salts (9)–(11) which provided the nitroamines (13)–(15) in quantitative yield. Reductive cyclisation of the nitroamines led to the tetrahydro-1H-pyrrolo[1,2-b][1,2,4]benzothiadiazine 5,5-dioxides (17)–(20) in very good yields. No optimisation of yields was attempted.Efficient methods for the synthesis of some new substituted N-(nitrobenzenesulphonyl)-pyrrolidinecarboxylic acids (1)–(4), which were not readily available, are also described.

Studies and Transactions on Pollution Assessment of the Lagos Lagoon System, Nigeria

The Lagos Lagoon system is a brackish coastal lagoon—the largest in the West African coast with a large series of estuaries—located between longitude 3o23′ and 3o40′E and between latitude 6o27′ and 6o48′N. It is a shallow expanse of water (0.3–3 m deep), 50 km long and 3–13 km wide and separated from the Atlantic Ocean by a narrow strip of barrier bar complex. This report is on the levels of pollution and nutrients status of the Lagos Lagoon system including physicochemical properties, pesticides organochlorines (OC), polyaromatic hydrocarbons (PAHs), heavy metal species and nutrients observed between 2002 and 2008. Watersheds of the highways on the lagoon had higher concentrations of nutrients (phosphorus and nitrates) relative to other locations on the Lagoon. The western part of the Lagoon was found to have higher concentrations of Cd, Cu, Pb and Zn than the other points. Lagos Lagoon and the adjoining creeks show high anthropogenic input of PAHs and other persistent organic pollutants (POPs). The major hydrocarbon index in most samples was at C29, C31 and C27, indicating vascular plants sources. Mean PBT levels in water and in sediment increased with time between 2004 and 2007. PBT distribution in the lagoon followed the pattern, sediment > biota > water, though some exceptions occurred where the biota bioaccumulated more PBTs than are found in both sediment and water. The Lagoon biota bioaccumulated organochlorine pesticides above allowable limits and thus pose a high risk to human health. The levels of some pollutants in the Lagoon have negatively impacted on the environmental quality which has indirectly affected the social and economic activities of the dependants and this requires improved management strategies to ameliorate. Indeed with the high population that the estuary/lagoon system supports, consideration for its designation as an international waterbody and its concomitant attention is now paramount.

Assessment of occupational exposure to polycyclic aromatic hydrocarbons via involuntary ingestion of soil from contaminated soils in Lagos, Nigeria

Soils from 12 sites in Lagos area, Nigeria impacted by anthropogenic activities were extracted by ultrasonication and analysed for the concentration of 16 priority polycyclic aromatic hydrocarbons (PAHs) by gas chromatograph-mass spectrometer (GC-MS). The concentration of the sum of PAHs ranged from 0.2 to 254 μg/g at these sites. The sum benzo[a]pyrene-equivalent dose (BaPeq) at the sites ranged from 0.0 (K, forest soil) to 16.7 μg/g (C, the lubricating oil depot soil). Mean daily intake (MDI) for the composite soils samples when compared that of food revealed that some of the individual PAH in samples from sites A (Dump site), C (Depot and loading point for used for black oil), F (Dump site), G(petroleum depot), H (Roadside) and L (Car park) exceeded the recommended the recommended MDI threshold for food, indicating some risk associated with activities on these sites based on this ingestion estimate exceeded value. 8.2 × 10−6, 7.1 × 10−7, 1.2 × 10−4, 4.9 × 10−7, 7.3 × 10−7, 1.4 × 10−5, 7.9 × 10−5, 4.6 × 10−6, 3.4 × 10−7, 2.4 × 10−7, 2.2 × 10−7 and 1.1 × 10−4 estimated theoretical cancer risk (ER) for an adult with a body weight of 70 kg working on sites were composite soil samples A, B, C, D, E, F, G, H, I, J, K and L respectively were sampled. The ER from occupational exposure to surface soil based on oral ingestion were all higher than the target risk of 1 × 10−6 for normal exposure but were all within the 1 × 10−4 for extreme exposure for most of the sites except for site C and L. The differences in concentration and risk were related to the different activities (e.g., handling of petroleum products, open burning, bush burning) undertaken at these locations. However, it should be noted here that the resultant risk could be overestimated, since these calculations were based on an exhaustive extraction technique which may be different from uptake by the human guts (bioavailability study).