Low level determination of gallium isotopes by ICP-QQQ

Determination of low concentrations of Ga in environmental or biological samples can benefit from interference free measurement of both Ga isotopes. Unfortunately, both isotopes have potential interferences, i.e doubly charged Ba at m/z 69 and MnO at 71. Analysis using collision and reaction gases by ICP-QQQ as an alternative to HR-ICP-MS is investigated here using conventional nebulization and a desolvating nebulizer. Analysis at m/z 71 is not appreciably affected by MnO at 200 ug/l Mn or in either water reference material; excellent detection limits of < 0.1 ng/l were obtained for He, H₂, or on-mass O₂ and NH₃ gas modes. Analysis of Ga at m/z 69 was severely affected by doubly charged Ba across all gas modes except +17 mass-shift (i.e. 69 - 86) NH₃ gas mode. Despite Ga being only 1-2% reactive at the 69-86 mass shift, the doubly-charged interference was not mass-shifted and detection limits of < 1 ng/l and precise and accurate quantification of two water reference materials and nine natural water samples were achievable for this analysis mode.

Evaluation of Gallium as a Tracer of Exogenous Hemoglobin-Haptoglobin Complexes for Targeted Drug Delivery Applications

Haptoglobin (Hp) is a plasma glycoprotein that generates significant interest in the drug delivery community because of its potential for delivery of antiretroviral medicines with high selectivity to macrophages and monocytes, the latent reservoirs of human immunodeficiency virus. As is the case with other therapies that exploit transport networks for targeted drug delivery, the success of the design and optimization of Hp-based therapies will critically depend on the ability to accurately localize and quantitate Hp-drug conjugates on the varying and unpredictable background of endogenous proteins having identical structure. In this work, we introduce a new strategy for detecting and quantitating exogenous Hp and Hp-based drugs with high sensitivity in complex biological samples using gallium as a tracer of this protein and inductively coupled plasma mass spectrometry (ICP MS) as a method of detection. Metal label is introduced by reconstituting hemoglobin (Hb) with gallium(III)-protoporphyrin IX followed by its complexation with Hp. Formation of the Hp/Hb assembly and its stability are evaluated with native electrospray ionization mass spectrometry. Both stable isotopes of Ga give rise to an abundant signal in ICP MS of a human plasma sample spiked with the metal-labeled Hp/Hb complex. The metal label signal exceeds the spectral interferences' contributions by more than an order of magnitude even with the concentration of the exogenous protein below 10 nM, the level that is more than adequate for the planned pharmacokinetic studies of Hp-based therapeutics. Graphical Abstract ᅟ.

A flow method based on solvent extraction coupled on-line to a reversed micellar mediated chemiluminescence detection for selective determination of gold(III) and gallium(III) in water and industrial samples

A rapid and sensitive flow method, based on the combination of on-line solvent extraction with reversed micellar mediated chemiluminescence (CL) detection using rhodamine B (RB), was investigated for the selective determination of Au(III) and Ga(III) in aqueous solutions. 2.0 M HCl was the optimum for extracting Au(III) while a 5.0M HCl solution containing 2.5M LiCl was selected as an optimum acidic medium for extraction of Ga(III). The Au(III) and Ga(III) chloro-complex anions were extracted from the above aqueous acidic solutions into toluene as their ion-pair complexes with the protonated RBH(+) ion followed by membrane phase separation in a flow system. In a flow cell of a detector, the extract was mixed with the reversed micellar solution of cetyltrimethylammonium chloride (CTAC) in 1-hexanol-cyclohexane/water (1.0M HCl) containing 0.10 M cerium(IV) and 0.05 M lithium sulfate. Then uptake of the ion-pair by the CTAC reversed micelles and the subsequent CL oxidation of RB with Ce(IV) occurred easily and the CL signals produced were recorded. Using a flow injection system, a detection limit (DL) of 0.4 μM Au(III) and 0.6 μM Ga(III), and linear calibration graphs with dynamic ranges from the respective DLs to 10 μM for Au(III) and Ga(III) were obtained under the optimized experimental conditions. The relative standard deviations (n=6) obtained at 2.0 µM Au(III) and 4.0 µM Ga(III) were 3.0% and 2.4%, respectively. The presented CL methodology has been applied for the determination of Au(III) and Ga(III) in water and industrial samples with satisfactory results.