Waqar Ashraf

Multinuclear NMR ( 1 H, 13 C, 15 N and 107 Ag) studies of the silver cyanide complexes of thiourea and substituted thioureas

Abstract The NMR (1H, 13C, 15N and 107Ag) studies of the silver(I) cyanide (AgCN) complexes of thiourea (Tu), N,N′-dimethylthiourea (Dmtu) and tetramethylthiourea (Tmtu) were carried out in dimethyl sulfoxide. An upfield shift in 13C NMR and downfield shifts in 1H, 15N and 107Ag NMR are consistent with the sulfur coordination to silver(I). The NMR data shows that C S – AgCN complexes are stable in solution and do not undergo disproportionation reactions.

Age- and sex-based comparative distribution of selected metals in the scalp hair of an urban population from two cities in Pakistan.

Concentrations of Cu, Zn, Pb and Ni in the scalp hair of male and female donors, with an age range of 6-60 years, were determined by ICP atomic emission spectroscopy. The donors were drawn from the densely populated city of Lahore and the relatively less-populated capital city of Islamabad for comparative evaluation of the metal levels in relation to age, sex and location. Linear regression analyses and correlation between paired metals indicated a positive correlation between Cu and Zn for both sexes ( [Formula: see text] ) and between Pb and Ni ( [Formula: see text] ) for males and females of Lahore. Metal concentrations varied between the two cities and the two sexes. The highest mean concentration was found for Zn at 180.5 microg g(-1) for males and 202.4 microg g(-1) for females from Lahore, while for counterparts from Islamabad the values were 105.2 microg g(-1) and 206.6 microg g(-1). Copper showed an identical mean concentration (20.8 microg g(-1)) in the hair of both males and females from Lahore; however, relatively lower mean concentrations (7.7 and 10.8 microg g(-1)) were observed for donors from Islamabad. Mean Pb concentrations in hair of male donors from Lahore and Islamabad were 9.4 and 7.0 microg g(-1), respectively; in female groups the concentrations were 14.3 and 5.7 microg g(-1), respectively. Ni showed the lowest concentration range (4.3-4.5 microg g(-1)) of all the four metals for subjects from Lahore, and this was higher than the corresponding range (2.0-3.2 microg g(-1)) for subjects from Islamabad. The findings are discussed in relation to the available data from the literature.

Silver Cyanide Complexes of Heterocyclic Thiones

Silver(I) cyanide complexes of various thiones (imidazolidine-2-thione, diazinane-2-thione and their derivatives) have been prepared and characterized by elemental analysis, i.r. and n.m.r. (1H, 13C, 15N and 107Ag) spectroscopy. It appears from the i.r. data that six out of the ten complexes are nonionic [>C=S—Ag—CN] while the remaining four exist as ionic species [Ag(>C=S)2]+[Ag(CN)2]− in the solid state. An upfield shift in the 13C-n.m.r. and downfield shifts in the 1H-, 15N- and 107Ag-n.m.r. spectra are consistent with the sulfur coordination to silver(I). The n.m.r. data shows that the [>C=S—AgCN] complexes are stable in solution and do not undergo redistribution.

Age and sex dependence of selected trace metals in scalp hair of urban population of Pakistan

Concentrations of ten metals (Ag, Al, Cd, Cr, Cu, Fe, Mn, Sr, Ca and Mg) in scalp hair of urban donors from the city of Lahore, Pakistan were determined by the nitric acid/perchloric acid digestion based method by ICP-AES. The age and sex dependence of metal levels was investigated for the age groups 10-47 and 7-55 years, for females and males, respectively. In total 45 female and 42 male samples were analysed in triplicate. The maximum concentration in the male group was that of Fe, between 45 and 330 mg/kg, followed by Sr between 4.5 and 109 mg/kg. On average, the following order of metal concentration in male hair was observed: Ca > Mg > Fe > Sr > Al > Cu > Mn > Cr > Ag > Cd. For female samples Cu was found to have a maximum concentration (210 mg/kg) followed by Fe (170 mg/kg) and Sr (140 mg/kg). In this group the concentration order was: Ca > Mg > Cu > Fe > Sr > Al > Mn > Ag/Cr > Cd. A metal to metal correlation study showed that different metals were mutually correlated in male and female hair. Regression equations illustrated a distinct dependence of metal concentrations on the age of donors. The data are compared with corresponding data reported in the literature.

Utilization of scalp hair for evaluating epilepsy in male and female groups of the Pakistan population.

Concentrations of Fe, Cu, Zn, Cr, Mg and Ca are determined in scalp hair of adult epileptic and normal male and female subjects by atomic absorption spectroscopy. A total of 85 hair samples for normal male/female subjects and 78 of male/female epileptic subjects were analyzed within the respective age groups of 28 to 30 and 24 to 27 years. The study showed higher average concentration of Zn, Fe and Cu in normal male subjects compared with the epileptic subjects. Levels of Ca, Mg and Cr were lower in normal male adults than those found in epileptic subjects. Epileptic females showed higher average concentrations of Zn, Ca and Cu. The correlation coefficient study indicated significant correlation (r > 0.589 at P = 0.001) between Fe and Cr, Mg, Ca and Cu for epileptic females only. For normal male subjects Ca showed a strong correlation for Zn and Fe and for Cr and Ca. The regression analysis showed the significant role of Zn, Ca, Mg and Cr in scalp hair of normal and epileptic subjects. Accordingly, the metal-to-metal ratio analysis revealed critical Mg/Zn ratios as indicators of healthy (< 1) and epileptic (> 1) subjects. The ratio data are used for evaluation of the status of epileptic patients based on their ailment history.

Comparison of trace metal levels in the hair of Pakistani Urban and rural adult male populations

Human scalp hair samples obtained from the urban and rural adult male populations in Pakistan were investigated for six essential elements (Ca, Fe, Mg, Cu, Cr, Mn), three toxic metals (Cd, Pb, Ni), and for Al and Sr. The maximum concentration in both segments of population was that of Ca 1880–4680 ug/g for the urban; 2357–4691 μg/g for rural population. On the average the following order of metal concentrations in urban hair was observed: Ca > Mg > Fe > Al > Sr > Pb > Cu > Ni > Mn > Cr > Cd. For the rural population Cd showed the minimum concentration level (0.17–1.9 μg/g). In this group the concentration order was: Ca > Mg > Fe > Al > Pb > Sr > Mn > Cu > Ni > Cr > Cd. Metal‐to‐metal correlation study between two groups showed that different metals were weakly correlated in rural and urban hair. Regression equations indicated a distinct dependence of metal concentrations on the habitats of donors. The data were compared with corresponding data reported in literature.

Concentrations of selected metals in scalp hair of an occupationally exposed population segment of Pakistan

Levels of five essential metals (Co, Cu. Fe, Mn and Zn) and four macroelements (Ca, K, Mg and Na) were determined in the scalp hair of an occupationally exposed male population of Karachi, Pakistan. These levels were compared with those of non‐exposed population so as to ascertain the current status of environmental pollution and the extent of occupational exposure to these metals. A comparison between the metal levels of washed and unwashed hair was also made. For an industrially exposed population, in case of essential metals, the maximum level was observed for Fe(225.1 μg/g), followed by Zn(170.7 μg/g) and Cu(17.0 μg/g). Statistical analysis showed that levels of all the metals analyzed were higher in the scalp hair of an exposed population. The age‐wise distribution of metals in the hair of an exposed population showed that Cu and Fe levels increased distinctly with increasing age, whereas for a non‐exposed counterpart no such behavior was observed. The results of the present study were found to be in...

Cadmium cyanide complexes with heterocyclic thiones: solid state and solution NMR studies.

Cadmium(II)cyanide complexes of various thiones (imidazolidine-2-thione, diazinane-2-thione and their derivatives) have been prepared and characterized by elemental analysis, IR and solid as well as solution NMR spectroscopy. It appears from the IR data that all complexes are non-ionic [(>C=S)(2)Cd(CN)(2)]. An upfield shift in the (13)C NMR and downfield shifts in the (1)H NMR are consistent with the sulfur coordination to cadmium(II). The solid (113)Cd NMR data show the presence of different coordination numbers in some complexes.

31P NMR studies of Redox reactions of Bis (Trialkylphosphine) Gold(I) Bromide (Alkyl = Methyl, Ethyl) with Disulphide and Diselenide ligands

Redox reactions of bis (trialkylphosphine) gold(I) bromide (alkyl = methyl, ethyl) with two diselenides (R′Se–SeR′), selenocystine and selenocystamine and their corresponding disulfides were studied in D2O by 31P NMR spectroscopy. Upon interaction of diselenides with (Me3P)2AuBr or with (Et3P)2AuBr, the Se–Se bond is broken, resulting in the formation of R3PAu+, R′SeH, R′Se–Au–PR3, R3PO and (AuSeR′) n . Second-order rate constants were determined for the decomposition of (R3P)2AuBr. Selenocystamine reacts with (Et3P)2AuBr about 100 times faster than its corresponding disulfide. However, cystamine reacts twice as fast with (Me3P)2AuBr compared to its corresponding diselenide.

LEVELS OF SELECTED TRACE METALS IN THE SCALP HAIR OF AN INDUSTRIALLY EXPOSED POPULATION SEGMENT OF PAKISTAN

Levels of nine metals (Ag, Al, As, Cr, Cd, Hg, Ni, Sr and Pb) were determined in the scalp hair of industrially exposed male population of Karachi, Pakistan. These levels are compared with those of non‐exposed population so as to ascertain the current status of environmental pollution and the extent of occupational exposure. A comparison is also made between metal levels of washed and unwashed hair samples. For industrially exposed population the maximum level was observed for Pb(34.6 μg/g), followed by Al(17.2 μg/g) and Ni(10.1 μg/g). Statistical analysis showed that the levels of industrial metals (Cr, Cd, Pb, Ni and Ag) were higher in case of industrially exposed population. The age‐wise distribution of heavy metals in the hair of exposed population showed that Ag and Ni levels increased distinctly with increasing age. The regression analysis showed fractional slope values indicating the concentrations of the metals in the hair of exposed population sector substantially exceeding those from the urban s...