It was demonstrated that a capillary electrophoresis (CE) method with a non-gel sieving solution has been developed to identify the orientation of DNA fragments in recombinant plasmids in molecular biology. The influences of the concentration of sieving polymer HEC, the applied electric field strength and sampling on CE separation were analyzed concerning the optimization of separation. YO-PRO-1 was used as a DNA intercalating reagent to facilitate fluorescence detection. Under the chosen conditions (buffer, 1 × TBE containing 1 μM YO-PRO-1 and 1.2% HEC; applied electric field strength, 200 V/cm; electrokinetic sampling: time, 5 s; voltage, -6 kV), three DNA markers (φ174/HaeIII, pBR322/HaeIII and λDNA/HindIII) were tested for further evaluating the relationship between the DNA size and the mobility. The established CE method conjugated with the enzymatic approach was successfully applied to identifying the DNA orientation of recombinant plasmid in transgene operations of a newly cloned gene from Arabidopsis Thaliana.
A flow-injection (FI) methodology using tris(2,2′-dipyridyl)ruthenium(II), [Ru(dipy)32+], chemiluminescence (CL) was developed for the rapid and sensitive determination of three thioxanthene derivatives, namely zuclopenthixol hydrochloride, flupentixol hydrochloride and thiothixene. The method is based on the CL reaction of the studied thioxanthenes with [Ru(dipy)32+] and Ce(IV) in a sulfuric acid medium. Under the optimum conditions, calibration graphs were obtained over the concentration ranges 0.002 - 6 μg/ml for zuclopenthixol hydrochloride, 0.5 - 15 μg/ml for flupentixol hydrochloride and 0.05 - 7.5μg/ml for thiothixene. The limits of detection (s/n = 3) were 4.2 × 10-9 mol/l zuclopenthixol hydrochloride, 2 × 10-8 mol/l flupentixol hydrochloride and 4.5 × 10-8 mol/l thiothixene. The method was successfully applied to the determination of these compounds in dosage forms and biological fluids.
A methodology for selecting the measurement conditions in the dye-binding method for determining serum protein has been studied by a theoretical calculation. This calculation was based on the fact that a protein error occurs because of a reaction between the side chains of a positively charged amino acid residue in a protein molecule and a dissociated dye anion. The calculated characteristics of this method are summarized as follows: (1) Although the reaction between the dye and the protein occurs up to about pH 12, a change in the color shade, called protein error, is observed only in a pH region restricted within narrow limits. (2) Although the apparent absorbance (the absorbance of the test solution measured against a reagent blank) is lower than the true absorbance indicated by the formed dye-protein complex, the apparent absorbance correlates with the true absorbance with a correlation coefficient of 1.0. (3) At a higher dye concentration, the calibration curve is more linear at a higher pH than at a lower pH. Most of these characteristics were similarly observed experimentally in the reactions of BPB, BCG and BCP with human and bovine albumins. It is concluded that in order to ensure the linearity of the calibration curve, the measurement should be performed at a higher dye concentration and sufficiently high pH where the detection sensitivity is satisfied.
A new nitrate-selective liquid-membrane electrode based on the tris(2,2′,2″-salicylideneimino)triethylamine-iron(III) complex has been developed. This electrode exhibits a linear Nernstian response over the range 10-1 - 10-4 M of nitrate, with a slope of 54.3 ± 0.9 mV per p[NO3]. The effects of the pH and the liquid-membrane composition were also investigated. The lifetime of the electrode is at least one month. The selectivity coefficients for ten monovalent ions were calculated. The preparation procedure of the electrode is very easy and inexpensive. Moreover, the proposed electrode was applied for the determination of nitrate in fertilizers.
Two sequential extraction procedures (the former proposed by the Standard, Measurements and Testing-SM&T-program of European Union and the latter derived from those of Tessier and Forstner with various modifications) have been compared, by analyzing a reference material (CRM 601) certified for the content of heavy metals in the three solutions resulting from the SM&T procedure. Scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX) was used to evaluate the composition of the residues after various extractions. Reliable results, both in terms of precision and accuracy, were obtained for the first two steps of the SM&T scheme. As regards the third step, because it was modified during this work, a direct comparison of our results with those certified is not possible. SEM analysis confirmed that the scheme previously used in the laboratory was more aggressive compared to the SM&T procedure, which has also the advantage that the only CRM available for metal partitioning in sediments is certified using this method.
A comprehensive method was developed for the sensitive and fast determination of trace levels of methyltin compounds in aqueous samples. Tin compounds in aqueous solution at pH 5 were converted to the corresponding volatile hydrides: CH3SnH3, (CH3)2SnH2, and (CH3)3SnH, by reaction with potassium borohydride. A CP-4010 purge and trap injector (PTI) was used to purge analyte species from water directly. The volatile derivatives were base-line separated on a capillary column in an Angilent-6890 gas chromatograph by a suitable temperature program and were detected by a flame photometric detector (FPD). The detection limits were 18 ng L-1 for monomethyltin, 12 ng L-1 for dimethyltin, and 3 ng L-1 for trimethyltin, respectively. This method was successfully applied to the determination of methyltin compounds in different aqueous samples.
A spectrophotometric method for the determination of total carbonate in water samples was developed. The method is based on the color change of an acid-base indicator in relation to the concentration of permeable gas substances through a membrane. By using a new portable FIA system equipped with a gas-diffusion unit, a highly sensitive and on-site determination of total carbonate in aqueous solutions was investigated. A new color-change system with 4-(2′,4′-dinitrophenylazo)-1-naphthol-5-sulfonic acid (DNN5S) was developed. Absorbance changes of the reagent solution were measured at 450 nm with a light-emitting diode (LED) as a light source. A new type of gas-diffusion unit was used, and was constructed with double tubing: the inner tubing was a micro porous PTFE (polytetrafluoroethylene) tubing (1.0 mm inner diameter and 1.8 mm outer diameter, pore size 2 μm, porosity 50%); the outer tubing was made of glass with 2.0 mm inner diameter. The optimized system conditions were as follows: the sample size was 200 μl, the temperature of the air bath for the gas-diffusion unit was 25°C, and the length of the gas-diffusion unit was 15 cm; each flow rate was 0.3 ml min-1. For measuring carbonate at low concentrations, a method for preparing water with less carbonate was proposed: the carbonate content of the water was decreased down to 5 × 10-7 M. The calibration graph was rectilinear from 1 × 10-6 M to 10-3 M, and the detection limit (corresponding to a signal-to-noise ratio of 3) was 1 × 10-6 M of carbonate. The relative standard deviation (RSD) of ten measurements of 2.3 × 10-5 M Na2CO3 solution was 1.9%. The total carbonate in various kinds of water (such as river, sea, rain, distilled and ultra purified) was determined.
The quantitative extraction of cationic surfactant (CS+) in river sediments was studied. Further, the developed method was applied to the spectrophotometric determination of CS+ in urban river sediment samples by solid-phase extraction with membranes. A mixture of methanol and hydrochloric acid was proposed as an eluent. Dried sediment was digested in the eluent under ultrasonic irradiation. After elution, the eluent was evaporated to almost dryness. The residue was dissolved in a small volume of methanol and diluted to a certain volume with water. The pH of the solution was adjusted to 4 - 5 to separate iron and some other metals as precipitates of hydroxides. The solution was passed through two-piled membranes: first glass-fiber and then polytetrafluoroethylene (PTFE) membranes. A small volume of methanol was passed through the membranes to elute any CS+ retaining on the membranes. After passing the methanol solution through a cationic exchange resin column, the retained CS+ was eluted with methanol containing a high concentration of sodium chloride. Water, Bromophenol Blue (BPB) and hydrochloric acid were added to the solution. The solution was passed through a mixed cellulose ester membrane filter to retain an ion associate of CS+·BPB-. The retained ion associate was dissolved in a small volume of N,N-dimethylformamide together with the membrane filter, followed by the addition of triethanolamine to make the solution alkaline. The absorbance due to BPB2- was measured at 603 nm against a reagent blank. This method was applied to the determination of CS+ in river water and sediment. A cationic surfactant in sediments at 10-5 mol kg-1 levels was detected with satisfactory precision. It was found that CS+ was about 500-fold enriched in the sediment from water at the place where domestic wastewater was discharged.
Acrylic oligomers such as pentaerythritolacrylates (PEA), which are often utilized in the field of functionalized materials, generally consist of very complex homologous series. In this work, measuring conditions for packed-column supercritical fluid chromatographic separation of a complex PEA sample manufactured industrially were systematically examined using temperature programming or modifier gradient technique. Under the conditions thus optimized, not only the main components, PEA homologues containing different number of acryloyl groups, but also trace constituents such as their by-products formed through Michael addition reactions were favorably resolved on the resulting chromatograms. The fact that the coefficient of variation (CV) for relative intensity of each peak was approximately 3 - 6% even for the minor components suggested that detailed compositional analysis of PEAs could be performed precisely by the proposed method.
The extraction rates of cadmium(II) and zinc(II) with dithizone (H2dz) in the presence of nitrilotriacetic acid (NTA) were measured, and the possible kinetic separation of cadmium(II) from zinc(II) was investigated. Upon the addition of NTA, the difference in the extraction rate between cadmium(II) and zinc(II) became large. Based on the observed rate constant under the condition [NTA] = 1 × 10-2 mol dm-3, [H2dz]org = 1 × 10-3 mol dm-3, and pH = 7.0, the shaking time required for the quantitative separation of cadmium(II) from zinc(II) was calculated to be between 326 and 995 s. The experimental results agreed with the prediction, and the quantitative separation of cadmium(II) from zinc(II) was performed within the above-mentioned range of shaking times.
A simple method for the rapid extraction and determination of ultra-trace amounts of Ag+ ions using octadecyl-bonded silica membrane disks modified with a recently synthesized fulvalen (tetramethyltetrathiafulvalen) (TMTTF) and graphite furnace atomic absorption spectrometry is presented. The extraction efficiency and influence of the flow rate, pH, nature of the counter ion and type and the least amount of eluent for the stripping of Ag+ from disks and breakthrough volume were evaluated. The maximum capacity of the membrane disks modified by 5 mg of TMTTF used was found to be 482 ± 6 μg Ag+. The detection limit of the proposed method is 1.0 ng/dm3. The method was applied to the recovery of Ag+ ions from different synthetic and water samples.
A rapid and sensitive spectrophotometric method is described for the determination of trace amounts of selenium using Variamine Blue (VB) as a chromogenic reagent. The proposed method is based on the reaction of selenium with potassium iodide in an acidic medium to liberate iodine, which oxidizes Variamine Blue to form a violet-colored species having an absorption maximum at 546 nm. Beer’s law is obeyed in the range 2 - 20 g of selenium in a final volume of 10 ml. The molar absorptivity and Sandell’s sensitivity were found to be 2.6 × 104 l mol-1 cm-1 and 0.003 μg cm-2, respectively. The optimum reaction conditions and other analytical parameters were evaluated. The effect of interfering ions on the determination is described. The proposed method has been successfully applied to the determination of selenium in real samples of water, soil, plant materials, human hair, and synthetic samples of cosmetics and pharmaceutical preparations.
The centrifugal liquid membrane (CLM) method, designed for the rapid sample injection, was applied to the kinetic study of the complexation of palladium(II) with 2-(5-bromo-2-pyridylazo)-5-diethyaminophenol (5-Br-PADAP) in the heptane/water system. The formation rates of Pd(II)-5-Br-PADAP complex, which existed only at the heptane/water interface, could be directly measured by the CLM method combined with transmission spectrophotometry. We found that the formation rates of Pd(II)-5-Br-PADAP complex were accelerated by the protonation of 5-Br-PADAP at the diethylamino-group that did not coordinate to Pd(II) ion and that the rate constant for the reaction of protonated 5-Br-PADAP at the interface was close to that in the aqueous phase. The present study demonstrated that the CLM method was easily applicable for the measurements of relatively fast interfacial reactions.
A rapid spectrophotometric method for the determination of platinum in 20% Pt-Ru (Pt:Ru (1:1)) carbon-supported catalyst has been developed. The samples of catalyst (0.85 - 12.60 mg) have been digested 1) in aqua regia after preliminary separation of carbon by burning or 2) directly in aqua regia in the presence of carbon. The detection of platinum was carried out in the obtained solutions after conversion of the metal into the iodide complex. The interfering effect of ruthenium on the detection of platinum was eliminated by the use of derivative spectrophotometry. Platinum was selectively determined by numerical calculation of the 4th-order-derivative absorption spectrum of the mixture of iodide complexes of both metals.
An important advance in surface science has been the evolution of sum frequency generation to the application of studying surface structure and chemistry of liquid surfaces at the molecular-level by probing the vibrational signatures of surface molecules. Recently, broad-bandwidth sum frequency generation (BBSFG) spectroscopy has become an important tool for investigating gas-solid interfaces. BBSFG spectroscopy allows, theoretically, a surface sum frequency spectrum to be acquired within one pulse of the laser. In this paper, the viability of BBSFG to study inherently small nonlinear response interfaces and the time-resolving capability of this surface-selective technology are demonstrated. Presented here are the first published accounts of spectra from a liquid surface utilizing the broad-bandwidth sum frequency technology with acquisition times as low as 500 milliseconds.