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We established a method for the separation and detection of nine hydroxylated polychlorinated biphenyls in whole blood and urine samples using ultra high performance liquid chromatography coupled with electrospray negative ionization tandem mass spectrometry. Clean‐up procedures involved a filtration step, and optimization involved a pretreatment step consisting of a simple liquid–liquid extraction using hydrated silica‐gel chromatography (5%). Nine hydroxylated polychlorinated biphenyls were separated on an ultra high performance liquid chromatography HSS T3 column using a gradient elution program of 2 mmol ammonium formate aqueous solution (A) and methanol (B). Recovery ranged from 84.0 to 105.4% for the nine different hydroxylated polychlorinated biphenyls in urine with three spiked levels of 0.1, 1, and 2 ng and from 73.5 to 98.6% for the blood with spiked levels of 0.2, 1, and 2 ng. The relative standard deviations were <8.7% (n = 6), and the limits of detection in urine and whole blood for the nine hydroxylated polychlorinated biphenyls were in the range of 1.5–4 and 20–100 pg/g, respectively. This analytical method may enable the simultaneous detection of various hydroxylated polychlorinated biphenyls from complex tissue matrices. [ABSTRACT FROM AUTHOR]

A robust ultra high performance liquid chromatography with tandem mass spectrometry method at peptide level was established for measuring α-lactalbumin in various dairy products. An isotope-labeled winged peptide (VKKILDKVG *INYW *LAHKALCSEKL) with extra amino acids of the sequence of signature peptide concatenated at each end as the internal standard was spiked in samples to participate in the whole tryptic digestion process. The peptide VG *INYW *LAHK that resulted from the isotope-labeled winged peptide was used as the final isotopically labeled internal standard of the α-lactalbumin signature peptide (VGINYWLAHK) during the quantitative analysis. The contents of α-lactalbumin in samples were calculated based on the equimolar relationship between the α-lactalbumin protein and signature peptide. The optimized molar ratio of trypsin to protein (1:60) and enzymatic digestion time (5 h) could not only improve the digestion efficiency and reduce the cost, but also minimize the period of sample pretreatment. Considering the robustness of the current method using the isotopically labeled internal standard and acceptable measurement cost, its application may promote the development of nutrient investigation and quality control of α-lactalbumin in dairy products. This protein analysis method might provide a new reference strategy for food analysis and quantitative protein analysis. [ABSTRACT FROM AUTHOR]

A series of NCO/NCS pincer precursors, 3-(Ar2OCH2)-2-Br-(Ar1NCH)C6H3 ((Ar1NCOAr2)Br, 3a, 3b, 3c, 3d) and 3-(2,6-Me2C6H3SCH2)-2-Br-(Ar1NCH)C6H3 ((Ar1NCSMe)Br, 4a and 4b) were synthesized and characterized. The reactions of [Ar1NCOAr2]Br/ [Ar1NCSMe]Br with nBuLi and the subsequent addition of the rare-earth-metal chlorides afforded their corresponding rare-earth-metal-pincer complexes, that is, [(Ar1NCOAr2)YCl2(thf)2] ( 5a, 5b, 5c, 5d), [(Ar1NCOAr2)LuCl2(thf)2] ( 6a, 6d), [(Ar1NCOAr2)GdCl2(thf)2] ( 7), [{(Ar1NCSMe)Y( μ-Cl)}2{( μ-Cl)Li(thf)2( μ-Cl)}2] ( 8, 9), and [{(Ar1NCSMe)Gd( μ-Cl)}2{( μ-Cl)Li(thf)2( μ-Cl)}2] ( 10, 11). These diamagnetic complexes were characterized by 1H and 13C NMR spectroscopy and the molecular structures of compounds 5a, 6a, 7, and 10 were well-established by X-ray diffraction analysis. In compounds 5a, 6a, and 7, all of the metal centers adopted distorted pentagonal bipyramidal geometries with the NCO donors and two oxygen atoms from the coordinated THF molecules in equatorial positions and the two chlorine atoms in apical positions. Complex 10 is a dimer in which the two equal moieties are linked by two chlorine atoms and two ClLiCl bridges. In each part, the gadolinium atom adopts a distorted pentagonal bipyramidal geometry. Activated with alkylaluminum and borate, the gadolinium and yttrium complexes showed various activities towards the of isoprene, thereby affording highly cis-1,4-selective polyisoprene, whilst the NCOlutetium complexes were inert under the same conditions. [ABSTRACT FROM AUTHOR]

A method of ultra-performance liquid chromatography combined with electrospray ionization triple quadrupole tandem mass spectrometry ( UPLC- ESI- MS/ MS) has been established for simultaneous determination of major disialoganglioside 3 ( GD3) and monosialoganglioside 3 ( GM3) in infant formulas and whey protein concentrates. Gangliosides were extracted by using the technique of Svennerholm and Fredman and then cleaned up with OASIS HLB solid-phase extraction ( SPE) cartridges. The various molecular species of gangliosides were separated on an Acquity UPLC BEH C8 column and analyzed under the negative ion mode. GD3 and GM3 were rapidly quantified using internal standard ( IS) method. The developed method was further validated by determining the linearity, average recovery, sensitivity (limit of quantification), and precision. The results presented high correlation coefficients ( R2 > 0.993) of the selected 16 gangliosides molecular species and provided the respective linear ranges. The limit of quantification was 0.325-0.734 mg/100 g for eight molecular species of GD3 and 0.008-0.312 mg/100 g for eight molecular species of GM3, respectively. The reasonable average recoveries (81-95%) and precision (relative standard deviation [ RSD] ≤15%) were also demonstrated in three different spiked levels. This new method would be very useful in the quantitative determination of gangliosides in infant formulas and whey protein concentrates. [ABSTRACT FROM AUTHOR]

An ultra-high-performance liquid chromatography-electrospray ionization coupled to mass spectrometry method has been developed for determining caseinoglycomacropeptide (CGMP) in infant formulas by selected ion reaction and area monitoring modes. The present study focused on the optimization of sample pretreatment, chromatographic resolution and mass spectrometry parameters. After a simple sample pretreatment, the two genetic variants of caseinoglycomacropeptide, CGMPA and CGMPB, were separated using a BEH300 C18 column by gradient elution. The established method was extensively validated by determining the linearity ( R2 >0.999), average recovery (95.8-118.4%), inter-day precision (relative standard deviation ≤7.81%) and intra-day precision (relative standard deviation ≤6.99%) based on two scan modes. To further verify the applicability of the method, 21 brands of commercial available infant formulas were analyzed. The results showed that the present method is selective, sensitive and reliable for separating and quantifying two genetic variants (CGMPA and CGMPB) of caseinoglycomacropeptide in infant formulas with complex matrix. [ABSTRACT FROM AUTHOR]