Organometallic Compounds and Metal-Ligand Complexes

Di- and trimethyl lead, di- and triethyllead, and methyl- and ethylmercury were resolved from each other and rainwater contaminants on a Cjg column (A = 235 nm) using a 40/60 methanol/water (0.1 M citric acid at pH 5.9 with 2.2 mM methyl thioglycate) mobile phase. Elution was complete in 50 min and detection limits of 280-800 ng/L (analyte dependent) were reported [146]. 

Nine organomercury compounds (e.g., methyl-, methoxyethyl-, phenyl-, tolyl-and benzoyl-mercury nitromersol and mersalylic acid) were baseline resolved on a C g column (A = 230nm) using a 25min 30/70 -y 50/50 methanol/water (50 mM ammonium acetate buffer at pH 5.0 with 0.1 mM 2-mercaptoethanol) gradient [147]. Note that the mercaptoethanol has a strong stench and so the system should be located in a well-ventilated area. Detection limits fi om 7 to 95 pg/L were reported (analyte dependent). 

Four butyltin and phenyltin compounds (diphenyltin, dibutyltin, triphenyltin, tributyltin) were separated on a Cg column (A = 425 nm, ex 496 nm, em) using an 84/15/1/0.03 methanol/water acetic acid/triethylamine mobile phase [148], Separation was complete in 14 min. Monophenyltin and monobutyltin required acetic acid levels of up to 10% for elution. In these cases where particularly aggressive mobile phases are needed, a precolumn should be used to protect the analytical column. Plots of k vs. % water and % triethylamine were presented. Linear ranges of 0.5-800 pg/L Sn and limits of detection and quantitation of 0.1-5 pg/L Sn (S/N = 3) and 0.5-11 pg/L Sn (S/N = 10, analyte dependent), respectively, were reported. 

A series of ions (Pd(II), Bc(II), Ga(in), Fe(III), AI(III) and Cu(II)) were extracted from water as their acetylacetone complexes and baseline resolved on a C g column (A = 330nm) using a 58/35/6/1 methanol/water/dichloromethane/acetic acid mobile phase [151]. Elution was complete in 40 min and detection limits of 1-5 ppb were reported. Peak shapes were uniformly good. The authors used this technique to determine Cu(II) and Fe(III) levels in tap water. It should be noted that other ]3-diketone complexing agents, used like ion pair reagents, should also be eflective here. 

Saitoh et al. [152] separated seven rare-earth ions (Nd(III), Gd(III), Tb(III), Dy(ni), Ho(ni), Er(III), Lu(III)) as their tetraphenylporphine complexes using a C 8 column (2 = 555 nm) and a 90/10 methanol/water (0.5% acetylacetone with 0.68% triethylamine) mobile phase. Injections of 10 pL of 0.1 mM metal-complex solutions were made. The Nd(III) complex was stable for less than one hour in any of the solvents methanol, acetone, acetonitrile, or dichloromethane. Elution was complete in 15 min. Similarly, the tetraphenylporphine complexes of VO(IV), Cu(II), Ni(II), Zn(II), and Pd(II) were resolved on a C g column (X = 420nm) using a metha-nol/octane mobile phase where octane was present at less than 0.1 mole fraction [153]. (It should be noted that 0.1 mole fraction octane is equivalent to 21% in methanol.) A 1 pL injection of a standard containing 4 x 10 M metal complex was readily detected. 

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