% for the procedure in which the loaded beads are transported directly to the graphite furnace for pyrolysis and atomization, and even improved in comparison to the traditional unidirectional and bidirectional repetitive elution procedures which under comparable conditions yield R.S.D.-values of 5.8 and 4.9%, respectively. The tolerance limits for cations such as Pb (II), Zn (II), Co (II) and Mn (II) were improved up to 10-50-folds, and the linear calibration range extended to comprise 0.02-1.20g l−1. Because of lower operating temperature, the life time of the graphite tube is extended. An enrichment factor of 71.1 and a detection limit of 10.2ng l−1 along with a sampling frequency of 12 h−1 were obtained, which are at the same levels as those for the previously described procedure without elution. The present approach was validated by determination of the nickel contents in two certified reference materials, an industrial waste water sample and a human urine sample.

A novel way of exploiting flow injection/sequential injection (FIA/SIA) on-line ion-exchange preconcentration with detection by electrothermal atomic absorption spectrometry (ETAAS) is described and demonstrated for the determination of trace-levels of nickel. Based on the use of a renewable microcolumn incorporated within an integrated micro FI-system, the column is loaded with a defined volume of small beads of an SP Sephadex C-25 cation-exchange resin and subsequently exposed to a metered amount of sample solution. However, instead of eluting the retained analyte from the organic ion-exchange resin, the beads are along with 30ml of carrier (buffer) solution transported via air segmentation directly into the graphite tube, where they are ashed during the pyrolysis and atomization process. The ETAAS determination is performed in parallel with the preconcentration process of the ensuing sample. An enrichment factor of 72.1, a detection limit of 9ng l−1, along with a sampling frequency of 12h−1 were obtained with 150 s of sample loading time at a sample flow rate of 12ml s−1 (corresponding to 0.72ml min−1). The relative standard deviations were 3.4%. The procedure was validated by determination of the nickel contents in two certified reference materials and in a human urine sample.

A micro-sequential injection spectrophotometric procedure for DNA assay was developed based on the employment of a lab-on-valve (LOV) meso-fluidic analytical system. A small amount of crystal violet solution (10μl) was de-colored inside the flow cell of the LOV at the presence of 5μl λ-DNA/HindIII within a certain pH range, and the absorbance decrease of crystal violet solution at 591 nm was measured via optical fibers and was employed as the basis of quantification. A uni-variant approach was adopted for the optimization of experimental parameters, including buffer pH, concentration and volume of crystal violet solution, reaction time and sample/reagent loading flow rates. A linear calibration graph was obtained within 0.2-6.0μgml−1, along with a detection limit of 0.07μgml−1. The procedure was applied for the determination of λ-DNA/HindIII in synthetic samples in comparison with a documented procedure.

An automated sequential injection hydride generation (HG) atomic fluorescence spectrometric (AFS) method was developed, with the aim of screening blood lead levels for Chinese citizens, especially for children. Lead hydride was generated from acid solution, with potassium ferricyanide as an oxidizing agent, by reaction with alkaline tetrahydroborate solution. The hydride was separated from the reaction medium in a gas–liquid separator (GLS1) and swept directly into the atomizer. A thorough scrutiny was made of the various factors, including the modification of the AFS instrument and related parameters, the various wet digestion protocols, the variables of the flow system and the reaction conditions. Under the optimized conditions the blank signal was satisfactorily minimized, giving rise to a limit of detection of 0.014μgl-1, defined as 3 times the blank standard deviation divided by the slope of calibration graph, and a RSD value of 0.7%(at the 2.0μgl-1 level, n=11), along with a sampling frequency of 120h-1. The sensitivity of the procedure was found to be significantly superior to those obtained by HG-atomic emission spectrometry (AES), direct sampling electrothermal atomic absorption spectrometry (ETAAS), tungsten filament atomizer ETAAS, and quartz tube atomizer HG-AAS; it was even lower than those by in-atomizer-trapping HG-ETAAS and comparable to ICPMS-based methods. The accuracy and practical applicability of the procedure were validated by analysing certified reference materials of frozen cattle blood GBW 09139 and GBW 09140, and further demonstrated by spiking recoveries of lead in human whole blood samples.

An automatic protocol for in-situ assay of dsDNA is presented by employing a micro-sequential injection lab-on-valve meso-fluidic system, which facilitates precise fluidic handling at the 0.1-10ml level. Sub-nano-liter to a few micro-liters of DNA sample and ethidium bromide (EB) solutions were introduced into the meso-fluidic system, where EB binding onto DNA takes place and an intercalated DNA-EB adduct was formed, which was afterwards excited in the flow cell of the LOV by a 473nm laser beam, and the emitted fluorescence was monitored in-situ via optical fibers. The experimental variables, i.e., pH of the buffer solution, the concentration and volume of EB solution, the reaction time and the fluid flow rates, were investigated. By loading 600nl sample and 1.0ml EB solution, a linear calibration graph was obtained within 0.03-3.0mg ml21 (dsDNA), and a detection limit (3s) of 0.009mg ml21 was achieved, along with a sampling frequency of 60h21 and a precision of 1.9% at the 1.0mg ml21 level. The detection limit was further improved to 0.006mg ml21 by increasing the sample volume to 2.0ml. Plasmid DNA in E. Coli extraction and l-DNA/Hind III in four synthetic samples were assayed by using this procedure. For the plasmid DNA, a good agreement with the documented UV method was obtained, while spiking recoveries for the synthetic samples were 95.6-103.4%.