Screening of four beta-blockers and codeine in urine by on-line coupled RPLC-GC with on-line derivatization

On-line coupled reversed phase liquid chromatography-capillary gas chromatography (RPLC-GC) was used in the separation of four derivatized beta-blockers and codeine in urine. Sample clean-up was accomplished in the LC part and compounds were separated in the GC part. After the LC column the aqueous phase was switched to organic solvent by on-line liquid-liquid extraction and the two phases were separated in a sandwich-type phase separator. The organic extract was then transferred to a loop-type LC-GC interface. Beta-blockers were derivatized on-line in the interface before GC analysis. Concurrent eluent evaporation was used during the introduction of the sample fraction, and excess of solvent vapors was removed via an early vapor exit. The sample pretreatment was minimal; the only manual pretreatment step was the filtration of the urine sample.     

毛细管电泳直接分析与水不互溶溶液中痕量物质的新方法

本文采用在线反萃取-场放大进样方法实现了毛细管电泳与溶剂微萃取的直接联用.     

Flow-injection hydride generation atomic absorption spectrometric study of the automated on-line pre-reduction of arsenate, methylarsonate and dimethylarsinate and high-performance liquid chromatographic separation of their -cysteine complexes

An automated on-line pre-reduction of arsenate, monomethylarsonate (MMA) and dimethylarsinate (DMA) using flow injection hydride generation atomic absorption spectrometry (FI-HGAAS) is feasible. The kinetics of pre-reduction and complexation depend strongly on the concentration of -cysteine and on the temperature in the following increasing order: inorganic As(V)<DMA<MMA. Arsenate is pre-reduced/complexed within less than 50 s at 70–100°C compared to 1 h at room temperature, while MMA and DMA require 1.5–2 min at 70–100°C and up to 1–2 h at room temperature. The characteristic masses and concentrations for 100 μl injections are 0.01 ng and 0.1 μg l⁻¹ in integrated absorbance and 0.2 ng and 2 μg l⁻¹ in peak height measurements, and the limits of detection are ca. 0.5 ng and 5 μg l⁻¹, respectively. In a high-performance liquid chromatography (HPLC)–HGAAS system, the -cysteine complexes of inorganic As(III), MMA and DMA are best separated within 7 min by HPLC on a strongly acidic cation exchange column such as Spherisorb S SCX 120×4 mm (5 μm) with a mobile phase containing 12 mmol l⁻¹ phosphate buffer (KH₂PO₄/H₃PO₄)–2.5 mmol l⁻¹ -cysteine, pH 3.3–3.5. Upon dilution to -cysteine levels below 10 mmol l⁻¹, which are compatible with HPLC separations, the DMA–cysteine complex is unstable on storage. No baseline separations are possible with anion exchange and reverse phase C₁₈ HPLC columns. The limits of detection with 50 μl injections in peak area mode are ca. 0.5 ng and 10 μg l⁻¹, respectively.     

On-line ion-exchange preconcentration in a flow injection system coupled to capillary electrophoresis for the direct determination of UV absorbing anions

On-line ion-exchange preconcentration, performed in a flow injection analysis system, has been integrated with capillary electrophoresis via a specially designed interface, and a sensitive and selective method for the determination of nitrite, nitrate, bromide and iodide using direct UV absorbance detection has been developed. Fivefold enrichment of these aforementioned anions can be realised. Separation conditions such as carrier electrolyte and concentration of electroosmotic modifier were investigated. Limits of detection were ca. 10 ng ml⁻¹ for nitrite and nitrate in aqueous samples, and the overall relative standard deviation was about 5%.     

Large-volume liquid chromatographic trace-enrichment system for environmental analysis

The fully automated on-line trace enrichment of 27 (polar) pollutants, using volumes of up to 1,000 mL, on a polymeric precolumn followed by liquid chromatography —diode-array detection has been studied. Various parameters influencing the reproducibility of these large volume injections like breakthrough volume, precolumn capacity, matrix effects, and enrichment flow rate are discussed. The relative standard deviation of the recoveries after enrichment of 25–500 mL of sample is 1–20%. Enrichment flow rates up to 15 mL min⁻¹ can be used with an optimum at 10 mL min⁻¹. A pore size of 300 A provides the best results using the polymeric PLRP-S material. The breakthrough volumes show significant dependence upon the concentration of the analytes in the sample.     

Research on Haar Spectrum in fault diagnosis of rotating machinery

In this paper,Haar Transform(HT)is used in the fault diagnosis of rotatingmachinery,and the“Impulse Sharpness”is presented as a diagnostic index.At present,Fourier Spectrumanalysis is most widely used Compared with FFT,HT is more rapid incomputation and more effective in discrete approximation.It’s very suitable for theextraction of pulses in the signal.However,HT has some shortcomings.It’s greatlyaffected by the starting point and length of the sample.Here,the authors present a methodto improve the stability and comparability of Haar Spectrum.The fault imitating test ofrolling bearing is carried out,and the results obtained have verified the sensitivity of HaarSpectrum and Impulse Index to the fault.     

粘油类产品中钠快速测定方法测量不确定度的评定

对粘油类产品中钠的快速测定方法的不确定度进行了评定,并建立了数学模型,对各不确定度分量进行了分析和量化。测量结果的扩展不确定度为0.40mg/kg。     

壳聚糖在线微柱预富集火焰原子吸收光谱法测定矿石中的痕量金

报道了壳聚糖作在线微柱预富集填料,流动注射与火焰原子吸收光谱联用(FI-FAAS)测定痕量金的方法。将金与硫氰酸钾混合富集在壳聚糖上并以硫脲作洗脱剂。当采样体积10.3 mL时,采样频率36个样/h,富集倍数26倍。检出限(3σ,n=11)0.50μg.L-1,相对标准偏差1.4%(ρAu=0.10 mg/L)和2.4%(ρAu=0.01mg/L)。该方法用于矿石中金的测定,结果满意。并探讨了壳聚糖吸附金的机理。