Michael A. Healy

Structural studies in main group chemistry : XXIII. Estertin derivatives, structural and spectroscopic studies

Abstract The crystal and molecular structures of three ‘estertin’ derivatives, Cl3SnCH2CH2CO2Me, Cl2Sn[CH2CH2CO2Me]2 and Cl2Sn[CH2CH2CONH2]2, are reported. Cystals of Cl3SnCH2CH2CO2Me are orthorhombic, space group P212121, with a 9.2981, b 10.5389, and c 10.0885 A; those of Cl2Sn[CH2CH2CO2Me]2 are monoclinic, space group P21/c, with a 8.0107, b 15.9104, c 13.4109 A, and β 131.0044°; and those of Cl2Sn[CH2CH2CONH2]2 are also monoclinic, space group Cc, with a 9.1314, b 12.8672, c 13.0317 A, and β 126.6032°. Crystals of Cl3Sn(CH2CH2CO2Me) and Cl2Sn[CH2CH2CO2Me]2 both consist of discrete molecules, but extensive intermolecular hydrogen-bonding occurs in crystals of Cl2Sn[CH2CH2CONH2]2. Intramolecular carbonyl oxygen-to-tin coordination occurs in all three compounds. Vibrational and mass spectra are also reported, and are assigned in accordance with the determined structures. Tin-119 Mossbauer studies demonstrate that it is possible to investigate the nature of organotin additives to PVC by this method. Preliminary investigations show that Bu2Sn(IOTG)2 added to PVC undergoes only partial IOTG for chlorine exchange at the milling stage, but is completely converted to Bu2SnCl2 after thermal degradation. Both BuAcSn(IOTG)3 and BuAcSn(βMeOct)3 undergo complete sulphur ligand for Cl exchange during the milling process giving BuAcSnCl3 as the species detected. Degradation to some unidentified organotin species occurs on heating.

Heavy metals in some Asian medicines and cosmetics

Significant concentrations of heavy metals have been found in a number of Asian medicines and cosmetics. The herbal baby tonic, Bal Jivan Chamcho contained lead leached from the coating of the spoon with which it was supplied. Some samples of Surma were found to have a lead content as high as 86%. Amongst other metals, mercury, lead and arsenic were found in the aphrodisiac and tonic Kushtay. A Warak which purported to be gold was a copper/zinc alloy. No mercury was found in the cosmetic Sandurs and Kum-Kum pastes we examined, but unacceptably high concentrations of lead and antimony were found in some pills, and of lead and arsenic in a powder intended for medicinal use. The use of traditional Asian remedies involves a substantial risk of heavy metal poisoning to which the medical profession should be alerted. Control by legislation alone would not be effective as many of the preparations are sent by relatives in Asia.

Lead poisoning and traditional practices: the consequences for world health. A study in Kuwait.

The extensive use of lead as a fallacious materia medica in certain cultural customs is presenting a serious risk to health for a large section of the worlds population. Data obtained in Kuwait exemplifies the problem. Four case-histories of paediatric patients are presented. These illustrate specific aspects of the clinical manifestations associated with lead poisoning from the use of the traditional preparation, Al Kohl, and practice, Bokhoor, in Kuwait. The lead analyses of 13 such materials are reported; nine of the samples being obtained from the parents of children exhibiting symptoms of plumbism. From examinations of a further 51 patients a maximum “safe” blood lead level for very young infants of 0·48 μmol/l (10 μg/dl) is deduced. In addition preliminary evidence is presented which supports the hypothesis that in neonates lead affects the synaptic inhibitor gamma amino butyric acid. (G.A.B.A.).

LEAD SULPHIDE AND TRADITIONAL PREPARATIONS: ROUTES FOR INGESTION, AND SOLUBILITY AND REACTIONS IN GASTRIC FLUID

Lead sulphide frequently occurs as a fallacious materia medica in traditional preparations used throughout the Moslem world. Although one of the least soluble lead compounds, use of this material as an eye powder has been directly associated with elevated blood‐lead levels in children. Data are presented from animal studies which show the primary route for ingestion of the eye cosmetic is not transcorneal transport. Conversion of the sulphide to the more soluble (and hence more readily absorbed) chloride form is shown to occur in gastric fluid and, significantly, a marked dependence of the rate of dissolution on particle size is found. This may explain the disparity in previous reported values for the extent of absorption of ingested lead sulphide.

COMPLIANCE AND DRUG THERAPY IN FASTING MOSLEM PATIENTS

The effects of fasting on the drug regimens of 81 Asian Moslem patients during the religious month of Ramadan have been examined.

Lead-207 chemical shift data for bivalent lead compounds: thermodynamics of the equilibrium Pb(O2CCH3)2⇄[Pb(O2CCH3)]++O2CCH3− in aqueous solution in the temperature range 303-323 K

Lead-207 n.m.r. chemical shift data have been recorded for the following bivalent lead compounds (solvent in parentheses) : Pb(NO3)2(water), Pb(ClO4)2·3H2O (water), Pb(O2CCH3)2·3H2O (water), Pb(O2CC6F5)2(tetrahydrofuran, thf), Pb[S2P(OR)2]2(R = C2H5 or i-C4H9)(thf and dichloromethane). The nature of the solution species is discussed. The very high-field chemical shifts exhibited by the hydrated lead(II) dication and the monoacetato- and mononitrato-lead(II) monocations are ascribed to efficient nuclear shielding resulting from the confinement of the lead(II) lone pair to the metal 6s orbital. Chemical shifts of the other species occur at much lower field, and structures in which the lone pair is stereochemically active and occupying a hybrid sp3dn orbital are proposed. Analysis of the concentration-dependence data has been employed to evaluate the association constant at 298 K, Kassoc., of [Pb(NO3)]+(1.233 dm3 mol–1), and the dissociation constant at 298 K, Kdissoc., of Pb(O2CCH3)2(0.0139 mol dm–3), for the aqueous lead(II) nitrate and acetate systems, respectively. Data for the systems Pb(O2CC6F5)2(tetrahydrofuran) and Pb[S2P(OEt)2]2(dichloromethane) have been interpreted in terms of a dimer ⇌ monomer equilibrium, with dissociation constants at 298 K of the dimer, Kdissoc., of 0.143 and 0.268 mol dm–3, respectively. The concentration-independent chemical shift of the lead(II) dithiophosphoridates in tetrahydrofuran is ascribed to the formation of a stable thf solvate in solution. Thermodynamic data for the equilibrium Pb(O2CCH3)2⇌[Pb(O2CCH3)]++ O2CCH3– in aqueous solution at 298 K have been evaluated as ΔH298=–14.2 kJ mol–1, ΔG298= 10.5 kJ mol–1, and ΔS298=–82.95 J K–1 mol–1.

Infrared detection in supercritical-fluid chromatography using xenon

Abstract Supercritical-fluid chromatography coupled to Fourier transform infrared spectroscopy (SFC-FTIR) combines high resolution chromatographic separation of thermally labile, high-molecular-weight materials with on-line finger-printing of eluted components by infrared spectroscopy. With supercritical xenon as the mobile phase, the system becomes a powerful and cost effective analytical tool with high sensitivity.

Fast time-resolved i.r. spectroscopy of biological molecules in aqueous solution: The reaction kinetics of myoglobin with carbon monoxide

Abstract The recombination of myoglobin (Mb) and CO, generated by the u.v. flash photolysis of carboxymyoglobin (MbCO) is monitored by time-resolved i.r. spectroscopy (TRIR) on a microsecond timescale. The TRIR measurements are made on the ν(CO) i.r. band of MbCO centered at 1945 cm −1 . Experiments have been performed over a wide range of concentrations of both Mb and CO and the rate constants derived are in excellent agreement with those obtained by conventional flash photolysis. The results represent a significant improvement in sensitivity over previous i.r. experiments of this type.

The reaction of lead(II) acetate with dimethylphosphite. A model for the interaction with ATP

Abstract Adenosine 5′-triphosphate (ATP) forms a complex of composition Pb 2 ATP·2H 2 O with lead(II) acetate or nitrate in aqueous media. The complex is only sparingly soluble in water, but the observation of two distinct 207 Pb nmr resonances indicates the presence of two different lead sites. In the solid the complex is amorphous precluding X-ray studies, and structural correlations are made with the known structure of the hydrated disodium salt, Na 2 ATP·3H 2 O. The complex is unstable, and decomposes at an as yet unknown rate on standing under water over three days. The complex Pb(O 2 CCH 3 ) 2 ·[(MeO) 2 HP(O)]· 3H 2 O, from lead(II) acetate and dimethylphosphite in water or methanol, decomposes spontaneously by stepwise elimination of methyl acetate affording lead phosphite as the final product.

Dramatic advances in on-line Fourier transform IR detection for capillary supercritical fluid chromatography

Abstract We have shown that a flow cell Fourier transform (FT) IR detector for capillary supercritical fluid chromatography (cSFC) can give minimum detection limits which are much lower than any previously reported for on-line cSFC—FT-IR. The system was tested using a range of analytes. The following reproducible values were obtained, using supercritical CO2 as the mobile phase: 2 ng for a polycyclic aromatic hydrocarbon (pyrene) — a rather weak infrared absorber, 95 pg for caffeine — a strong infrared absorber, and ca. 20 pg for the organometallic complex (mesitylene)chromium tricarbonyl — which has some intense infrared absorptions. These figures represent an improvement by a factor of at least 25 on comparable data in the literature. For caffeine a linear dynamic range of more than three orders of magnitude was established for this sytem.