摘要:

An analytical approach involving aqueous-phase derivatization followed by gas chromatography/ion trap mass spectrometry (GC/ITMS) for the determination of methylmercury in waters is described. The aqueous-phase derivatization is based on the formation of a more hydrophobic compound between MeHg+and BPh−4, i.e. MeHgPh, which is extractable into dichloromethane. The detection limit of the method for MeHg is 1 ng/mL for Hg when 100 ml water was analyzed. Recoveries from standard addition to tap water, lake water are 96 ± 8% and 92 ± 8%, respectively.

ISSN:0003-2719    

DOI:10.1080/00032719708001767

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Stripping voltammetry (SV), in common with all trace voltammetric analytical techniques, suffers from poor signal-to-noise (S/N) ratios due to external interference pick up and inherent generation of noise in the electrochemical system. In addition to other methods developed to smooth noisy data (such as time and frequency domain filtering), optimisation methods can also be used to reject the noise present in electrochemical measurements. In this paper, an optimisation method, based on a modified Simplex procedure, is presented. The method is based on minimising the deviation (in terms of the mean square error) between the recorded data and a theoretical model of the data. In this case, the model was a response surface consisting of one or more peak-shaped functions of one of the following types: Gaussian (G), exponentially modified Gaussian (EMG), Lorentzian (L), combined Gaussian-Lorentzian (GL) and theoretical voltammetric peak (TVP). The method was successfully applied to stripping signals obtained for the trace quantification of riboflavin and for the simultaneous determination of zinc, cadmium lead and copper by SV.

ISSN:0003-2719    

DOI:10.1080/00032719708001768

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A new epoxy-urea chelating resin was synthesized from epoxy resin and used for the preconcentration and separation of trace Bi(III), In(III), Sn(IV), Zr(IV), V(V) and Ti(IV) ions from solution samples. The analyzed ions can be enriched at pH 5 at a flow rate of 1–4 ml/min, and can be also desorbed with 10 mL of 2 M HCl +0.1g NH4F solution from the resin column, with recoveries over 97%. The chelating resin reused 6 times can still adsorb quantitatively the Bi, In, Sn, Zr, V and Ti ions, and eighty to thousand-fold excesses of Ca(II), Mg(II), Cu(II), Zn(II), Al(III), Sb(III), Ni(II), Mn(II) and Fe(III) cause little interference with the enrichment and determination of these ions. The RSDs of the proposed method for the determination of 500–50 ng/ml Bi, In and Sn, 50–5.0 ng/ml Zr, V and Ti were in the range of 0.4 ∼ 4.0%, the enrichment factor of the resin for the ions is in the range of 10–100. The recoveries of added standard in waste water are between 96% and 100%, and the concentration of each ion in alloy steel sample determined by the method is in good agreement with the reference value analyzed by a steel plant with average error <2.8%.

ISSN:0003-2719    

DOI:10.1080/00032719708001769

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A flow-injection system with biamperometric detection for L-ascorbic acid (vitamin C) determination was designed. The method is based on L-ascorbic acid oxidation to dehydroascorbic acid, in acidic medium, using iodine-iodide solution as oxidizing reagent. The iodine amount consumed in the redox reaction was biaperometrically detected and it was proportional to the amount of L-ascorbic acid from the sample. The calibration graph was linear over the range of concentration 5×10−5-5×10−4M of vitamin C. The RSD for a 2.5×10−4M standard solution of vitamin C was 1.08% (n=10) and the throughput was 60 samples h−1. The selectivity of the proposed FIA method was verified using an ascorbate oxidase solution as carrier stream. It was found that L-ascorbic acid could be determined in natural products with a good selectivity and rapidity.

ISSN:0003-2719    

DOI:10.1080/00032719708001770

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0003-2719    

DOI:10.1080/00032719708001756

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor