| Arsenic and mercury are human carcinogens, and the toxicity of them varies widely from species to species involved. Hence, a better understanding of toxic mechanism of arsenic and mercury is significantly important. However, biological experiments and its speciation analysis can lead to limited availability of sample, and collection of samples in the range of 10-50 nL is very common in this field. Nano high performance liquid chromatography (NanoHPLC) shows high chromatographic resolution and low solvent consumption and is often coupled with highly sensitive and element-specific detectors, among which inductively coupled plasma mass spectrometry (ICP-MS) is one of the best choices for arsenic and mercury speciation. The coupling of nanoHPLC with ICP-MS is often problematic due to flow rate incompatibilities. Hence the development of dedicated nanoflow nebulizers for sheathless coupling of ICP-MS and nanoHPLC is highly desirable.The research was based on these aspects, including the progress of arsenic and mercury speciation analysis in the trace samples, nanoHPLC hyphenated with ICP-MS, and nanoflow nebulizers for inductively coupled plasma spectrometries. The research purpose was to achieve the coupling of nanoHPLC with ICP-MS, and the main research work was summarized as follows:First, a simple, low-cost and small-dead-volume demountable nanoflow nebulizer (d-NN) was fabricated, which consisted of a nebulizer body, a solution capillary and an adapter. The tip of the solution capillary of the nanonebulizer was ground with sandpapers to obtain a thin nozzle (5?m thick and 20 ?m i.d.). The experimental results indicated that the performances of the proposed nanoflow nebulizer at 500 nL/min were similar to or even better than those obtained with d-CMN and other nanoflow nebulizers.Then, the developed nanonebulizer was utilized as the sheathless interface for nanoHPLC-ICP-MS to separate arsenic species on a reversed-phase capillary column and an anion exchange capillary column, respectively. The separation of arsenic species (50 nL samples) was achieved within 16 min on a homemade reversed-phase capillary column (150 ?m i.d. × 450 ?m o.d. × 15 cm) with 2.0 mmol/L tetrabutyl ammonium hydroxide (TBAH) aqueous solution (pH 6.58) as the mobile phase. In comparison with the chromatogram by the reversed-phase capillary column, more effective separation and higher sensitivity of the As-analytes were achieved on a strong anion exchange capillary column (100 ?m i.d. × 360 ?m o.d.× 25 cm), packed in the laboratory, with 10.0 mmol/L of sodium tartrate-tartaric acid solution (pH 6.90) as the mobile phase at 620 nL/min.Last, the separation of mercury species was performed by usage of the nanoflow nebulizer for sheathless interfacing nanoHPLC with ICP-MS. The mercury species were separated within 13 min on a reversed-phase capillary column (150 ?m i.d.× 450 ?m o.d. × 15 cm) with 10.0 mmol/L of L-cysteine solution (pH 5.00) as the mobile phase.The originality in this thesis:A low-cost demountable nanoflow nebulizer (d-NN) was first fabricated. Low dead volume, ultra-low self-aspiration, narrower aerosol size distribution and higher analyte transport efficiency (nearly 100%) were obtained with the proposed nebulizer. Furthermore, the ICP-MS instrument could tolerate direct introduction of 100% organic solvents by using the developed nebulizer operating at nanoflow rates. It was utilized to sheathless interface nanoHPLC-ICP-MS for arsenic speciation analysis with higher sensitivity (by 2-3 fold). The separation of meury species in a nanoscale samples was first attained by using low-volume mobile phase. |
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