Robert Kingsford-Adaboh

Topological analysis of DL-arginine monohydrate at 100 K

Abstract The charge density of DL-arginine monohydrate has been extracted from a synchrotron data set of 212121 reflections collected at 100 K with a Bruker CCD area detector up to a resolution of sin θ/λ = 1.40 Å-1 (d = 0.36 Å). DL-arginine monohydrate is characterised by a neutral α-amino group and a notable different hydrogen bond pattern compared to previously examined free arginine structures. All bond critical points of the electron density at the covalent and hydrogen bonds were located. We compare the local topological indices of ρ(r) with other amino acids. The conformation obtained from the experimental structure is found to be different from the Hartree-Fock (HF) optimization for the isolated molecule, thus the topology obtained from the static experimental charge density is compared to that derived from calculations at experimental and optimized geometry at HF and B3LYP levels of theory.

DL-arginine monohydrate at 100 K.

In the title compound, C(6)H(14)N(4)O(2).H(2)O, the alpha-amino group is neutral. The molecular side chain including the guanidinium group is not fully extended, having a near gauche-gauche conformation [chi(3) = 59.0(1)degrees; chi(4) = 72.8(1)degrees]. The network of hydrogen bonds stabilizing the crystal lattice includes those formed between the deprotonated and negatively charged alpha-carboxylate groups and the positively charged amino groups of the guanidinium group of neighbouring molecules. N-H...O=C and water-mediated N-H...O hydrogen bonds link individual molecules to produce pairs of spiral motifs laterally connected by N-H...O and C-H...O hydrogen bonds.

Pesticide residues in fruits and vegetables in Ghana: a review

Pesticides are known to improve agriculture yield considerably leading to an increase in its application over the years. The use of pesticides has shown varying detrimental effects in humans as well as the environment. Presently, enough evidence is available to suggest their misuse and overuse in the last few decades in most developing nations primarily due to lack of education, endangering the lives of farmers as well as the entire population and environment. However, there is paucity of data especially over long durations in Ghana resulting in the absence of effective monitoring programs regarding pesticide application and subsequent contamination in fruits and vegetables. Therefore, this review discusses comprehensively pesticide type and use, importation, presence in fruits and vegetables, human exposure, and poisoning in Ghana. This is to alert the scientific community in Ghana of the need to further research into the potential implications of pesticide residues in food commodities in order to generate a comprehensive and reliable database which is key in drafting policies simultaneous with food regulation, suitable monitoring initiatives, assessment, and education to minimize their effects thereon.

Synthesis and crystal structure studies of three n-phenylphthalimide derivatives

The three N-phenylphthalimide derivatives, 2-(3,4-dichlorophenyl)isoindoline-1,3-dione (I), 2-(2,4-dichlorophenyl)isoindoline-1,3-dione (II) and 2-(2,4,5-trichlorophenyl)isoindoline-1,3-dione (III), were synthesized by the condensation of equimolar amounts of phthalic anhydride and 3,4-dichloroaniline, 2,4-dichloroaniline, 2,4,5-trichloroaniline, respectively, under acetic acid reflux and their structures determined by a combination of elemental analysis, FT-IR, 1H & 13C-NMR spectroscopy and single crystal X-ray diffraction studies. Compounds I and II crystallize in a monoclinic crystal system (space group P21/c) with cell parameters of a = 5.7414(2), b = 8.0917(6), c = 26.077(1) Å and β = 99.4709(12)o for compound I, and a = 12.7133(9), b = 13.4328(9), c = 7.2603(5) Å and β= 93.210 (2)o for compound II. On the other hand, compound III crystallizes in a tetragonal crystal system (space group I41/a) with a = 13.4607(9) and c = 30.100(2) Å. The phthalimide moieties of these compounds are essentially planar, while the chloro-substituted phenyl ring of each compound shows consistent twist from the phthalimide plane with dihedral angles of 61.02(3), 69.09(3) and 85.78(5)o, respectively, for I, II and III. In the crystal structures of these compounds, a few weak C–H···O interactions form double-tape structures of centrosymmetric dimers of graph-set notation R22(10) for I and III, and an inversion dimer of graph-set motif R22(14) for II. In addition, some short contacts of C···C, C···O and Cl···Cl are observed for I, II and III, respectively.Graphical AbstractThis paper presents the synthesis, characterization and structural studies of three derivatives of Phthalimides which are well known cytotoxic DNA intercalating agents and potential anti-cancer agents, inhibit the acute inflammatory response and HIV-1 reverse transcriptases and found usefulness in OLEDs. Compounds I and II crystallize in a monoclinic crystal system (space group P21/c) while compound III crystallizes in a tetragonal crystal system (space group I41/a). The phthalimide moieties of these compounds are essentially planar, while the chloro-substituted phenyl ring of each compound shows consistent twist from the phthalimide plane. A few weak C–H···O interactions form double-tape structures for I and III, and a dimer for II.

Surveillance of pesticide residues in fruits and vegetables from Accra Metropolis markets, Ghana, 2010–2012: a case study in Sub-Saharan Africa

Monitoring of pesticide residues in food commodities of plant origin is part of the regular controls on food to safeguard consumer’s health. This study reports for the first time in Ghana a 3-year (2010–2012) monitoring of pesticide contamination of fruits and vegetables and their health implications. A total of 3483 samples were purchased in notable markets within Accra Metropolis and analysed for pesticide residues, employing the modified quick, easy, cheap, effective, rugged and safe analytical procedure. The results indicated that almost all the fruits and vegetables studied had residues above maximum residue limits (MRLs). The commodities with the greatest concentrations exceeding the European Union (EU) MRLs were long green beans (60.6%) and lettuce (57.1%) with watermelon (10%) and green pepper (8.6%) having the least. The relative occurrence of the pesticides was fenvalerate 11.3%, fenitrothion 5.6%, lambda-cyhalothrin 3.6%, dimethoate 3.2%, permethrin 2.7% and deltamethrin 2.2%. These results will serve as a baseline on which annual or other long-term studies could be compared with, thus emphasizing the need for continuous monitoring programmes to regulate trends of pesticide residues in fruits and vegetables to safeguard the consumers’ health.

Validation of QuEChERS method for the determination of 36 pesticide residues in fruits and vegetables from Ghana, using gas chromatography with electron capture and pulsed flame photometric detectors

In this study, “Quick, Easy, Cheap, Effective, Rugged and Safe” ‘QuEChERS’ method was modified for the determination of 36 pesticides fortified at (0.01–1.0) mg kg−1 in three vegetables and a fruit (lettuce, carrot, tomatoes and pineapples respectively) from Ghana. The method involved extraction with acetonitrile, phase separation with primary secondary amine and magnesium sulfate; the final injection solution was reconstituted in ethyl acetate. Organochlorine and synthetic pyrethroids residues were detected with electron capture detector whereas organophosphorus, pulsed flame photometric detector was used. The recoveries at different concentration levels (0.01, 0.1 and 1.0 mg kg−1) were in the range of 83% and 93% with relative standard deviation ranging from 2% to 10% (n = 5) and the coefficient of determination (R2) was greater than 0.99 for all the 36 pesticides. The method was successfully tested on 120 real samples from Accra markets and this proved to be useful for monitoring purposes particularly in laboratories that have no gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry.

Bis[(3-chloro­benz­yl)ammonium] 2-phenyl­propane­dioate dihydrate

In the asymmetric unit of the title compound, 2C7H9ClN+·C9H6O4 2−·2H2O, there are two crystallographically independent cations, one dianion and two water molecules. The dihedral angle between the two carboxylate groups of the dianion is 78.1 (2)°. In the crystal, the components are held together by N—H⋯O, O—H⋯O and C—H⋯O hydrogen bonds, forming a layer parallel to the bc plane, with the hydrophilic and hydrophobic groups located in the inner and outer regions of the layers, respectively.