A new software-controlled time-based multisyringe flow injection system for mercury determination by cold-vapor atomic absorption spectrometry is proposed. Precise known volumes of sample, reducing ...agent (1.1% SnCl
2 in 3% HCl) and carrier (3% HCl) are dispensed into a gas–liquid separation cell with a multisyringe burette coupled with one three-way solenoid valve. An argon flow delivers the reduced mercury to the spectrometer.
The optimization of the system was carried out testing reaction coils and gas–liquid separators of different design as well as changing parameters, such as sample and reagents volumes, reagent concentrations and carrier gas flow rate, among others.
The analytical curves were obtained within the range 50–5000
ng
L
−1. The detection limit (3
σ
b/
S) achieved is 5
ng
L
−1. The relative standard deviation (R.S.D.) was 1.4%, evaluated from 16 successive injections of 250
ng
L
−1 Hg standard solution. The injection and sample throughput per hour were 44 and 11, respectively.
This technique was validated by means of solid and water reference materials with good agreement with the certified values and was successfully applied to fish samples.
A sophisticated measurement system for at‐line determination of the main C‐source glucose, the by‐product acetate, and the N‐source ammonium for high cell density cultivations (HCDC) of Escherichia ...coli K12 TG1 is presented. One flow diffusion technique (FDA) system is used for glucose measurement in the range of 0.5 up to 40 gL–1 in the cultivation broth. Another FDA system detects the amount of the undesired by‐product acetate. The ammonium concentration in the range of 0.2 to 2.5 gL–1 is determined on‐line by a flow injection analysis (FIA) system. For verification purposes, an HPLC system which is also connected to the bioreactor for at‐line measurements is utilized. Several HCDC with cell densities of more than 100 gL–1 have been carried out. The courses of growth‐determining substrates have been detected at‐line. All used systems have shown an excellent compliance with off‐line measurements.
During the cultivation of E. coli, well known for the efficient production of recombinant proteins, like hormones and enzymes, also metabolic by‐products are formed that might cause a decrease in growth and productivity performance. A sophisticated measurement system for at‐line determination of the C source glucose, the by‐product acetate and the N source ammonium for high cell density cultivations of E. coli K12 TG1 is presented. Two different flow diffusion analysis systems and a flow injection analysis system were applied as at‐line measurement devices. For verification purposes, an off‐line HPLC system was used.
Devices and methods for Integrated Bioprocessing have been developed for production of recombinant proteins with the yeast Pichia pastoris. In doing so cross flow filtration techniques for cell ...separation and product concentration are connected directly to high instrumented cultivation processes. These are equipped with on‐line measuring techniques for substrates and products, e.g., glycerol, methanol and pyruvate as well as recombinant proteins, e.g., the chemokines 1–8del MCP‐1 and vMIP‐II. Complex automation structures allow for process development at virtual plants which can be used as the basis for establishing and implementing fully automated real processes. Experiments for determination of reaction kinetics, optimization of productivity in high‐cell density cultures and Integrated Bioprocessing are outlined, along with detailed illustration of the realization of the methods at industrial pilot plant scale.
Devices and methods for integrated bioprocessing have been developed for production of recombinant proteins, such as 1–8del MCP and vMIP‐II, with the yeast Pichia pastoris. Experiments for determination of reaction kinetics, optimization of productivity in high‐cell density cultures and integrated bioprocessing are outlined, along with detailed illustration of the realization of the methods at industrial pilot plant scale.
The development of an apparatus for the on-line sampling, digestion and quantification of total mercury in surface water is described. Detection and quantification is done by flow injection cold ...vapor atomic absorption spectroscopy (FI-CVAAS). Three digestion methods were tested, chemical, microwave and UV. The influence of the digestion parameters (digestion method, digestion time, microwave power, concentration of oxidation solution) on the recovery of mercury in water of the river Elbe have been investigated. Mercury can be determined almost quantitatively (recovery rate > 85%) with some digestion procedures described. The best results were reached by UV digestion. The technique is fast, simple to handle and robust. Each complete analysis only take four minutes. The working range is 10 to 1000 ng/L. The measuring arrangement has been applied successfully in a governmental monitoring station at Schnackenburg/Elbe, Germany.
A sequential injection analysis (SIA) method for the at-line determination of formaldehyde in a cultivation process of
Pichia pastoris is presented. A genetically modified yeast strain was used for ...cultivation processes wherein methanol feed induced the production of the recombinant protein 1-3del I-TAC. Recurring measurements of culture medium, its blank and including standard addition were performed with Nash reagent using an automated syringe device and photometric detection. The apparatus was coupled via a laboratory-made flow-through adapter to a continuous filtered and cell-medium flow from the bioreactor. At-line monitoring of formaldehyde was performed at two cultivations, each of 250
h during fed-batch phases with glycerol and methanol as carbon sources. High reliability, robustness and reproducibility of the method, the software and the instrumentation as well as the high selectivity of the reaction were demonstrated.
A novel sample introduction valve, based on the tubing clamp operation principle, is described for teaching flow-injection analysis. It was developed to overcome the shortage of instrumentation in ...elementary instruction courses in analytical chemistry at Fachhochschule Hamburg. The materials for one valve, which can be easily build-up by the students, is <$10.
A smart and versatile flow system for the at-line monitoring of glycerol based on sequential injection analysis is proposed. Formaldehyde, generated by oxidation of glycerol with sodium periodate, is ...transformed into 2,4-diacetyl-1,4-dihydrolutidine applying the Hantzsch condensation reaction with acetylacetone and ammonium. Dual-wavelength detection was carried out to minimize the contribution of the schlieren effect using a single blue LED. In-line sample dilution is accomplished applying the concept of zone-penetration and a new concept of sample splitting. Under optimized physical and chemical variables, regression curves over two dynamic working ranges of 0.1–4 and 1–40
g
l
−1 were attained. The injection throughputs were 14 and 12
h
−1, respectively. Applying on-line data evaluation and conditional inquiries, the smart and independent selection of the adequate analytical procedure for the required working range was accomplished. The system was successfully applied to the at-line monitoring of glycerol in a continuous, cell-free medium flow from a yeast cultivation process during batch and fed-batch phase with glycerol as the only carbon source.
A novel and expeditious approach for the direct determination of total mercury in seawater coupled on-line to a flow manifold and a cold vapor atomic absorption spectrometer is described. The ...detection limit of 0.1
ng/l was improved by optimizing the flow system, adding a drying unit for the mercury vapor and a gold amalgam preconcentration. The relative standard deviation of three measurements of 0.5
ng/l Hg
2+ was 2.7%. The long-time (12
h) reproducibility was 6.2% R.S.D. (
n=25) of 0.5
ng/l Hg
2+. The system has on-line UV digestion with a recovery rate of about 90% and a throughput of 10
samples/h. The accuracy of the method was evaluated by the analysis of certified reference materials. The results showed good agreement with the certified values. The system was applied on the research vessel Alexander von Humboldt (Baltic Sea Research Institute, Warnemünde, Germany) in the Baltic Sea. Total mercury concentrations Hg
T were measured in the surface water in a range of 0.2–1.87
ng/l. The technique is fast, simple to handle and robust.
A monitor is described which provides the on-line determination of mercury in river water at concentrations from 20 to 1000 ng/L. The measurement includes an on-line digestion with Br-/BrO3- and ...UV-radiation. Each determination is controlled by an on-line addition of 50 and 100 ng/L mercury carried out by pre-dilution of a 500 and 1000 ng/L stock solution using sequential injection analysis (SIA). One cycle of analysis takes 20 min and results in nine signals. A five days stand-alone operation has been performed successfully. Details are also published at web page: "http/www.rzbd.fh-hamburg.de/-prmercol".
The instrumental set-up for the on-line sampling, digestion and quantification of total mercury in seawater is described. Based on a flow system and cold vapour atomic absorption spectrometry (CVAAS) ...detection limit was improved by a gold amalgam preconcentration to 0.5 ng l
−1. The manifold design was optimized by the variation of the gas flow, length of reaction coils, shape and material of the gas–liquid separator and flow rate of the reductant. A calibration following the equations
p=0.039
c+0.0813 (
p, peak area;
c, concentration) and a correlation coefficient of
r=0.9996 was obtained. The relative standard deviation of three measurements of 0.5 ng l
−1 Hg
2+ was 3.8%. The long-time (12 h) reproducibility was 6.2% RSD (
n=25) of 0.5 ng l
−1 Hg
2+. With a recovery rate >90% mercury can be determined after on-line UV digestion. For a complete analysis, 6 min is required. The technique is fast, simple to handle and robust. The apparatus is designed for the use on research vessels under sea conditions.
