Biomedical subjects

Zhaoguang Yang

Publications and source records attributed to Zhaoguang Yang.

5 recordsLinked to original sources

PubMed2003

Bromate assay in water by inductively coupled plasma mass spectrometry combined with solid-phase extraction cartridges.

Based on selective sorption of bromide, bromoacetic acids (BAA) and bromomethanes on solid-phase extraction (SPE) cartridges, a sensitive and convenient method was developed for the determination of bromate in waters by inductively coupled plasma mass spectrometry (ICP-MS). Dionex OnGuard Ag and reversed-phase (RP) cartridges were tested for retention characteristics for bromide, BAA and bromomethanes. When a sample acidified with nitric acid was passed through an RP cartridge, BAA and bromomethanes were retained, afterwards bromide was absorbed as a precipitate of silver bromide and bromate was unretained when the nearly neutral sample passed a combination of Ag and H cartridges. After SPE pretreatment the recovery of bromate was 96-106%, and bromide remaining in the aqueous phase was found to be less than 0.06 microg L(-1) when the original bromide concentrations were less than 5 mg L(-1). Effectiveness of stacked Ag and H cartridges in removing bromide from chloride-containing samples was also examined. Common cations and other anions did not interfere with bromate determination. The detection limit for bromate is 57 ng L(-1). This method has been applied to analyse waters from various sources, and the recovery of the spiked bromate was in the range of 92-107%.

Journal Article↗

PubMed2003

Speciation analysis of tellurium by solid-phase extraction in the presence of ammonium pyrrolidine dithiocarbamate and inductively coupled plasma mass spectrometry.

Under acidic conditions tellurium(IV) formed a complex with ammonium pyrrolidine dithiocarbamate (APDC). The tellurium(IV) complex was completely retained on a non-polar Isolute silica-based octadecyl (C(18)) sorbent-containing solid-phase extraction (SPE) cartridge, while the uncomplexed Te(VI) passed through the cartridge and remained as a free species in the solution. Only partial Te(IV) was retained on the SPE cartridge for samples without addition of APDC. On the basis of different retention behaviours of the complexed Te(IV) and uncomplexed Te(VI), a simple and highly sensitive method is proposed for the determination of total tellurium and Te(VI) by SPE separation and inductively coupled plasma mass spectrometry (ICP-MS) detection. The Te(IV) concentration was calculated as the difference between total tellurium and Te(VI) concentrations. The detection limit (3 sigma) is 3 ng L(-1) tellurium. Factors affecting the separation and detection of tellurium species were investigated. Coexisting ions did not show significant interferences with the Te(IV)-APDC complex retention and the subsequent ICP-MS detection of Te. The method has been successfully applied to the tellurium speciation analysis in waters with spiked recoveries for Te(IV) and Te(VI) of 86.0-108% and 87.1-97.4%, respectively.

Mass Spectrometry↗

PubMed2003

Large-volume sample stacking combined with separation by 2-hydroxypropyl-beta-cyclodextrin for analysis of isoxyzolylpenicillins by capillary electrophoresis.

A simple, quick and sensitive capillary electrophoretic technique has been developed for the pharmaceutical analysis of isoxazolylpenicillins (oxacillin, cloxacillin and dicloxacillin) at trace levels for the first time. This method comprises large-volume sample stacking using the electroosmotic flow (EOF) pump (LVSEP), separation using 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CD) as selective complex-forming background electrolyte additive, and direct UV detection. A complete resolution was achieved in the optimal background electrolyte containing 5.2 mM HP-beta-CD. LVSEP was successfully applied in their determinations to improve the sensitivity, where the EOF in the buffer zone was suppressed by using an acidic buffer with pH 3.6. The detection limits of the current technique were found to be 2.0 microg/L for each of the isoxazolylpenicillins based on the signal-to-noise ratio of 3. The curves of peak response versus concentration were linear from 5.0 to 400.0 microg/L with regression coefficients of 0.9982, 0.9986 and 0.9976, respectively. The interaction of isoxazolylpenicillins with HP-beta-CD was discussed. The association constants for complexes of HP-beta-CD with isoxazolylpenicillins were determined by electrophoretic method. The obtained association constants were 27.3, 34.9, and 48.5 M(-1), respectively, being proportional to their hydrophobic properties and steric hindrances. A simple and easy-manipulative sample preparation method was developed and validated by analyzing commercially available milk samples. It was found that with current sample preparation process and instrumentation system, 0.1 mL of milk sample is enough for the analysis of isoxazolylpenicillins to meet European Union (EU) guideline of 30 microg/kg.

2-Hydroxypropyl-beta-cyclodextrin↗

PubMed2002

Large-volume sample stacking for analysis of ethylenediaminetetraacetic acid by capillary electrophoresis.

A simple, quick, and sensitive capillary electrophoretic technique-large volume stacking using the electroosmotic flow (EOF) pump (LVSEP) - has been developed for determining ethylenediaminetetraacetic acid (EDTA) in drinking water for the first time. It is based on a precapillary complexation of EDTA with Fe(III) ions, followed by large-volume sample stacking and direct UV detection at 258 nm. The curve of peak response versus concentration was linear from 5.0 to 600.0 microg/L, and 0.7 to 30.0 mg/L. The regression coefficients were 0.9988 and 0.9990, respectively. The detection limit of the current technique for EDTA analysis was 0.2 microg/L with an additional 10-fold preconcentration procedure, based on the signal-to-noise ratio of 3. As opposed to the classical capillary zone electrophoresis (CE) method, the detection limit was improved about 1000-fold by using this LVSEP method. To the best of our knowledge, it represents the highest sensitivity for EDTA analysis via CE. Several drinking water samples were tested by this novel method with satisfactory results.

Buffers↗

PubMed2002

Antimony speciation by inductively coupled plasma mass spectrometry using solid phase extraction cartridges.

A novel and simple method for inorganic antimony speciation is described based on selective solid phase extraction (SPE) separation of antimony(III) and highly sensitive inductively coupled plasma mass spectrometric (ICP-MS) detection of total antimony and antimony(V) in the aqueous phase of the sample. Non-polar SPE cartridges, such as the Isolute silica-based octyl (C8) sorbent-containing cartridge, selectively retained the Sb(III) complex with ammonium pyrrolidine dithiocarbamate (APDC), while the uncomplexed Sb(V) remained as a free species in the solution and passed through the cartridge. The Sb(III) concentration was calculated as the difference between total antimony and Sb(V) concentrations. The detection limit was 1 ng L(-1) antimony. Factors affecting the separation and detection of antimony species were investigated. Acidification of samples led to partial or complete retention of Sb(V) on C8 cartridge. Foreign ions tending to complex with Sb(III) or APDC did not interfere with the retention behavior of the Sb(III)-APDC complex. This method has been successfully applied to antimony speciation of various types of water samples.

Antimony↗