The Journal of Automatic Chemistry最新文献

A high impedance unit was developed for use with a fluoride/pH electrode system for the measurement of serum fluoride. The linearity, accuracy, precision and detection limit of the system is reported. At a pH of 1.55, the system was linear over a range of serum fluoride concentrations up to 100 mumol l(-1), with a lower limit of detection of 0.3 mumol l(-1). Recoveries at this pH were 94-105% in the range 2.6-100 mumol l(-1). Within-run CVs ranged from 4.2% at a level of 2.3 mumol l(-1) to 1.2% at a level of 55.7 mumol l(-1), while day-to-day CVs ranged from 12.8% at a level of 2.2 mumol l(-1) to 4.6% at a level of 51.7 mumol l(-1). The system demonstrated a rapid response time and has the potential for a smaller sample size requirement with alternative electrode shape. Continued development of this unit into an automated fluoride ion selective electrode system is recommended, since the measurement of serial serum fluoride samples is of greatest importance in assessing the impact of new anaesthetic agents on renal function.

An automatic procedure for calibration in continuous-flow systems is proposed. A flow gradient unit in the sample channel, controlled via a switching valve, delivers a concentration gradient of the standard so that the standard concentration varies with time after the flow-rate gradient is started. Thus, the signal (absorbance)- concentration relationship can be determined and checked for (recalibration) as frequently as required. The procedure was applied to a simulated continuous monitoring of hydrazine in waters, as well as to specific water samples that were spiked with hydrazine at different concentrations.

A simple automatic analytical system, consisting of separate modules, for liquid chromatography has been constructed. The different parts of the automatic machine are an auto sampler, an auto dispenser, a selector valve with eight channels, a heater/cooler, a mixing chamber and a pressure air driven injector valve. The process was controlled by a PC from an easily changeable run protocol. The system was applied to analysis of primary amines. The analysis was performed as a pre-column derivatization reaction of the amines and separation by isocratic reversed-phase HPLC with fluorescent detection. Reproducibility and analytical precision have been studied. Comparison between automatically and manually made derivatization reaction and injection was also made. The automatic system was easy to handle, cost-effective and gave good reproducibility.

The paper describes the development of an automatic on-line column pre-concentration technique using a time based-flow injection atomic absorption spectrometry system. A manifold incorporating a micro-column containing 25 mg of Dowex 50W-X8 was used with a time-based injector for the pre-concentration and determination of copper in natural and drinking waters. The system features depend on the alternate positions of a solenoid valve. The 3sigma detection limits, enrichment factors, sampling frequency, relative standard deviations and linear calibration graphs were, respectively, in the range 0.6-1.5 mug/l, 25-60, 15-30 measurements/h, 1.0-3.1% and 1-65 mug/ml for pre-concentration times of 1 min. The procedure was successfully applied to a range of water samples and the accuracy was assessed through recovery experiments, the analysis of certified reference water samples and by independent analysis by atomic absorption spectrometry with electrothermal atomization.