Laboratory Robotics and Automation最新文献

We have further developed our microscale automated chemistry workstation for investigating the optimization of reaction conditions. The workstation includes a Cartesian robot for solvent delivery and reagent/sample handling, a 60-vessel reaction block, a UV–Vis absorption spectrometer, and vial racks for compound storage. This article describes the following hardware additions that increase the scope and versatility of the workstation: (a) an analytical high performance liquid chromatography (HPLC) instrument and accompanying hardware interface (slide rail, autosampler); (b) three reactor blocks of 20 vessels each, with independent temperature control of each reactor block between ca. 0 and 80°C; (c) a shaker rack for mixing, dilution, or extraction of samples; (d) a rotary valve on the dispense line for complete isolation of 4 independent solvent lines; (e) sample workup features using disposable cartridges or filters; (f) provisions for dispensing inert gas, for example, for flushing through reactors or for storing solvents and performing transfer/dispense operations under. Using the new features, we are able to obtain useful analytical data from a wider range of reaction mixtures, perform parallel reactions at different temperatures, and handle solvents and sensitive reagents. © 1999 John Wiley & Sons, Inc. Lab Robotics and Automation 11: 217–223, 1999

Solid–liquid extraction behaviors of trivalent rare earths (La–Lu, Y) from ammonium thiocyanate solution by tributyl phosphate using molten paraffin wax as diluent were studied and optimum extraction conditions were determined. In 10 mL of aqueous RE³⁺ solution where C_RE(III) = 4.0 × 10⁻³ mol·L⁻¹, when additions of tributyl phosphate and ammonium thiocyanate are 5.00 mL and 2.80 g, respectively, extraction distribution ratios are over 10. The procedure can be used for rapid extraction separation of rare earths. An extraction mechanism was also investigated, and the complex species extracted into organic phase is RE(TBP)(SCN)(NO₃)₂. © 1999 John Wiley & Sons, Inc. Lab Robotics and Automation 11: 229–233, 1999

A flow-injection (FI) system to match concentrations was used as an auto-diluter in multielement determination by inductively coupled plasma–mass spectrometry (ICP–MS). The flow system comprised loop-based injection or a timed valve that introduced a variable sample volume into a spray chamber through a standard Meinhard nebulizer of an ICP–MS. Routinely analyzed samples such as water, plant, and steel were selected. The accuracy of multielement determination was checked against water standard reference material from the National Institute of Standards and Technology (1643d), plant standard reference material from the National Bureau of Standards (1572 citrus leaves), and steel standard reference material from the National Bureau of Standards (AISI 4340). The measuring system was calibrated with a multielement solution, yielding a linear plot with good precision [relative standard deviation (RSD) < 3%, n = 12]. The results were in agreement at a 95% confidence level with the certified values for the reference materials and also with those obtained by continuous aspiration and by (FI) with a discrete volume. © 1999 John Wiley & Sons, Inc. Lab Robotics and Automation 11: 240–247, 1999

Dynamic responses of self-made potentiometric NH₃, CO₂, and SO₂ sensitive gas sensors are followed in the 10⁻⁵–5 × 10⁻³M concentration range. By least squares fitting of potential versus time curves, Dk product values at the diffusion of NH₃, CO₂, and SO₂ through microporous Teflon are calculated. The obtained results are fairly reflected by the behavior of the sensor. Measurements of potential versus time in mixed solutions of CO₂ and SO₂ with the CO₂ sensitive sensor indicate the presence of the interferent. © 1999 John Wiley & Sons, Inc. Lab Robotics and Automation 11: 224–228, 1999

Several variables that affect flow spectrophotometric titrations in sequential injection analysis (SIA) systems were studied by using titration of a strong acid with a strong base as a model; blue bromothymol was used as an indicator and distilled water was used as a carrier. Both possibilities of performing titrations on SIA systems according to the aspiration sequences (a) titrant B/sample/titrant A and (b) titrant/sample are considered. In case (a) the possibilities regarding the use of different volumes and/or different concentrations of titrant reagents were studied and are discussed. The established methodology allows hydrochloric acid determinations with 0.1 M sodium hydroxide within the range 32–1000 mM by means of logarithmic calibration curves. The analysis rate is of 5 min/sample. © 1999 John Wiley & Sons, Inc. Lab Robotics and Automation 11: 207–216, 1999

The binding mode of Co(en) (en = ethylenediamine) to calf thymus DNA is investigated using electrochemical and spectroscopic methods. Binding constant value (K = 1.284 × 10³ L/mol) is found to be the same by the two methods. Both isomers show the same CV behavior associated with binding to B-form DNA. CD spectra results show no enantoselectivety for both isomers binding to DNA. All of this evidence suggests that the Co(en) complex binds to DNA by an electrostatic mode. © 1999 John Wiley & Sons, Inc. Lab Robotics and Automation 11: 193–196, 1999

The construction and analytical evaluation of a tubular ion-selective electrode coated with an ion pair formed between saccharinate anion and toluidine blue O cation incorporated on a poly(vinylchloride) (PVC) matrix was constructed and adapted in a flow-injection (FI) system. The optimum experimental conditions found were an analytical path of 120 cm, an injection sample volume of 500 μL, a pH of 2.5, a flow rate of 2.3 mL min⁻¹, and a tubular electrode length of 2.5 cm. The linear response to saccharin concentration ranged from 1.0 × 10⁻⁴ to 2.0 × 10⁻² mol L⁻¹, with a slope of −53.1 ± 0.4 mV/decade and a detection limit of 8.0 × 10⁻⁵ mol L⁻¹. The analytical frequency was 40 determinations h⁻¹, and this system was used with success for saccharin determination in several dietary products. © 1999 John Wiley & Sons, Inc. Lab Robotics and Automation 11: 234–239, 1999

This article presents a self-made device used for continuous determination of pH in hard-working industrial conditions: mining and sugar industries. The device consists of a pH detector and a specific pH meter. The tungsten (W) based pH electrode and the mechanical cleaner of the electrode surface are the main parts of the pH detector. The continuous cleaning of the electrode surface ensures the high accuracy (±0.15 pH) of the continuous pH measurements. © 1999 John Wiley & Sons, Inc. Lab Robotics and Automation 11: 147–150, 1999