Method For Determination Of Concentration Research Articles

Microvolume Protein Concentration Determination using the NanoDrop 2000c Spectrophotometer

Traditional spectrophotometry requires placing samples into cuvettes or capillaries. This is often impractical due to the limited sample volumes often used for protein analysis. The Thermo Scientific NanoDrop 2000c Spectrophotometer solves this issue with an innovative sample retention system that holds microvolume samples between two measurement surfaces using the surface tension properties of liquids, enabling the quantification of samples in volumes as low as 0.5-2 μL. The elimination of cuvettes or capillaries allows real time changes in path length, which reduces the measurement time while greatly increasing the dynamic range of protein concentrations that can be measured. The need for dilutions is also eliminated, and preparations for sample quantification are relatively easy as the measurement surfaces can be simply wiped with laboratory wipe. This video article presents modifications to traditional protein concentration determination methods for quantification of microvolume amounts of protein using A280 absorbance readings or the BCA colorimetric assay.

Nanoliter liquid characterization by open whispering-gallery mode dielectric resonators at millimeter wave frequencies

We present an approach for identification and concentration determination of liquids of pico to nanoliter volumes at a frequency of 35 GHz based on a whispering-gallery mode (WGM) dielectric resonator technique. A quasioptical coupling scheme based on dielectric image waveguides was employed to excite high-Q running wave WGMs with uniform azimuthal field distribution in cylindrical sapphire disks with quality factors up to 4×105 at room temperature. Measurement of the liquid induced changes in the resonator quality factor and resonance frequency has been performed for droplets down to 90 pl volume spotted at different positions on the surface of the sapphire disk. We have employed our method for concentration determination of ethanol, glucose, and albumin dissolved in water. Solutions with concentration values well below 10% could be clearly separated from pure water. Our method is promising for the characterization of biological liquids.

Method for concentration determination of mineral-oil fog in the air of workplace

To study the method of concentration determination of mineral-oil fog in the air of workplace. Four filter films such as synthetic fabric filter film, beta glass fiber filter film, chronic filter paper and microporous film were used in this study. Two kinds of dust samplers were used to collect the sample, one sampling at fast flow rate in a short time and the other sampling at slow flow rate with long duration. Subsequently, the filter membrane was weighed with electronic analytical balance. According to sampling efficiency and incremental size, the adsorbent ability of four different filter membranes was compared. When the flow rate was between 10 approximately 20 L/min and the sampling time was between 10 approximately 15 min, the average sampling efficiency of synthetic fabric filter film was 95.61% and the increased weight ranged from 0.87 to 2.60 mg. When the flow rate was between 10 approximately 20 L/min and sampling time was between 10 approximately 15 min, the average sampling efficiency of beta glass fiber filter film was 97.57% and the increased weight was 0.75 approximately 2.47 mg. When the flow rate was between 5 approximately 10 L/min and the sampling time between 10 approximately 20 min, the average sampling efficiency of chronic filter paper and microporous film was 48.94% and 63.15%, respectively and the increased weight was 0.75 approximately 2.15 mg and 0.23 approximately 0.85 mg, respectively. When the flow rate was 3.5 L/min and the sampling time was between 100 approximately 166 min, the average sampling efficiency of filter film were 94.44% and 93.45%, respectively and the average increased weight was 1.28 mg for beta glass fiber filter film and 0.78 mg for beta glass fiber filter film and synthetic fabric synthetic fabric filter film. The average sampling efficiency of chronic filter paper and microporous film were 37.65% and 88.21%, respectively. The average increased weight was 4.30 mg and 1.23 mg, respectively. Sampling with synthetic fabric filter film and beta glass fiber filter film is credible, accurate, simple and feasible for determination of the concentration of mineral-oil fog in workplaces.

Non-invasive and isotope-selective laser-induced fluorescence spectroscopy of nitric oxide in exhaled air

The detection of nitric oxide (NO) is of considerable medical interest. NO is involved in a multitude of mammal physiological processes, and various non-invasive concentration determination methods for NO have been developed during the last few years. Regarding time resolved metabolism behavior the quantitative determination of the 15N16O-isotopologue in combination with 15N-labeled drugs and amino acids is a central interest of current medical research. We apply laser-induced fluorescence (LIF) spectroscopy for isotope-selective detection of NO in various biological environments with a theoretical detection limit below 0.1 parts per trillion (ppt). Electronic excitation of the AX-transition in the UV provides fluorescence around 247 nm from . For an online measurement of human exhaled air, a respiratory mask has been constructed and integrated into our system. This paper gives an overview of the applied LIF device for non-invasive detection of NO originated from exhaled human air. The main advantages of this device compared to established methods are as follows: high sensitivity for NO concentrations in the ppt region, a high time resolution of 20 ms and isotopic selectivity to distinguish between 14NO and 15NO. Visualizations of single-exhalation profiles and long-time online measurements including the determination of absolute NO concentrations are presented and the influence of quenching gases present during the experiment is discussed. To our knowledge, we present for the first time time-resolved 15NO online profiles of exhaled human air.

Prediction of acute toxicity of chemicals in mixtures: Worms Tubifex tubifex and gas/liquid distribution

The aim of this contribution is to support our proposal of the procedure for predicting acute toxicity of binary mixtures by QSAR analysis techniques. The changes of a mixture composition are described by molar ratio R and visualized in the R -plot (QCAR--quantitative composition-activity relationships). The approach was inspired by Rault and Dalton's laws, their positive and negative deviations in the behavior of a mixture of real gases, by Loewe and Muischnek isoboles and by the Finney test of additivity. Acute toxicity was determined by the laboratory test with worms Tubifex tubifex . The additivity of the acute toxicity in the binary mixture benzene+nitrobenzene was confirmed and a new interaction is described: "mixed interaction" with the binary mixture aniline+ethanol. The "mixed interaction" means that depending on mixture composition, both potentiation and inhibition can occur. As the first physicochemical descriptor of the changes caused by the changing composition of binary mixtures, the gas/liquid equilibrium was studied and a composition of the gaseous phase was determined by a gas chromatographic method. The method for determination of concentrations in the gaseous phase was described. The gaseous phase composition of benzene+nitrobenzene, benzene+ethanol , benzene+aniline and ethanol+aniline mixtures was analyzed. It was found that if the concentrations of the mixture's components in the gaseous phase behave non-ideally (they are not additive), the acute toxicity of the same mixture is not additive as well. Another descriptor to distinguish between potentiation and inhibition will be, however, necessary. The properties, both gaseous phase composition and the acute toxicity, of the benzene+nitrobenzene mixture are additive. In mixtures with the mixed interaction, the R -plot of the composition of the gaseous phase is complex with a large variation of results.

カラムスイッチング高速液体クロマトグラフィーによる銅電解液中のにかわ分析

A new method for determination of concentrations of trace glue in copper electrolyte solutions, and the molecular weight distribution of the glue, and its change with time using a combination of the size exclusion chromatography (SEC) and the column-switching methods was developed. Trace amount of glue can be separated from a large amount of copper sulfate and sulfuric acid in the electrolyte solutions by pretreatment of the SEC resin column. Then, only a fraction containing the glue could be introduced into an analytical column by the column-switching technique, and the determination of concentrations of glue and the molecular weight distribution of the glue could be analyzed. This method was applied to electrolyte solutions containing mg L-1 level glue to determine concentrations and molecular weight distributions of the glue of molecular weight larger than about 2, 500.Degradation behavior of the glue in the electrolyte solutions was also investigated. The velocities speed of the hydrolysis reaction are depended on the concentrations of sulfuric acid. By the temperature dependency of the hydrolysis reaction rate constant of glue, the apparent activation energy of hydrolysis was estimated to be 65kJ/mol using an Arrhenius plot.

Hydrogen bulk states in stainless-steel related to hydrogen release kinetics and associated redistribution phenomena

Hydrogen represents the main residual gas in UHV and EHV stainless-steel chambers and to suppress its outgassing rate, the material is usually thermally treated in vacuum. In an attempt to prove the hypothesis that hydrogen in stainless steel is located in more than one bulk state, the thermal extraction method for concentration determination was applied from 305 to 1000°C. A thin AISI 304 sample was inductively heated and released gases were accumulated and subsequently analysed by a quadrupole mass spectrometer (QMS). Measurements began at low temperature and several cycles were repeated until the outgassing rate approached the detection limit of the set-up. The same procedure was used at higher temperatures. The observed outgassing behaviour cannot be explained by a model where the diffusion in the bulk over single states limits the kinetics nor by a model where only surface reactions limit it. The amount of extracted hydrogen was 5.1×10 19 H atom/cm 3 (total heating time 59.3 h) which greatly exceeded the value calculated on the basis of published data for solubility. At higher temperatures more hydrogen atoms were available to escape from the bulk than at lower temperatures although the sample seemed to be previously “outgassed”. The redistribution occurred even at room temperature and diminished the effect of previous treatments. A simple second-order kinetics model was introduced to obtain some relevant parameters, which may be applied for a more accurate prediction of hydrogen release kinetics.

Simultaneous Determination of Micro Bromide and Iodide by Kinetic Spectrophotometric Method

ABSTRACT ABSTRACTA new kinetic spectrophotometric method for the simultaneous determination of concentrations of micro bromide and iodide has been proposed. It is based on their catalytic effects on the reaction of m-cresol purple oxidized by potassium periodate in hydrochloride acid medium. The reaction rate was monitored by measuring the decrease in absorbance at 528nm and the increase in absorbance at 455nm. The total difference in absorbance of the sum of bromide and iodide is identical with determination of bromide was carried out after Cr(VI) oxidized I− to I2, and I2 was removed by extraction with CCI4, and the amount of iodide was measured by subtracting the absorbance change of bromide from the total absorbance change in the presence of bromine and iodide. The optimum conditions influencing the reaction rate were studied. The linear range of determination is 0∼4.0μg/ml for Br− and 0∼3.0 μg/ml for I−. The detection limits are 0.032μg/ml for Br− and 0.059 μ/ml for I−. The method was successfully applied to the determination of micro amounts of bromide and iodide in food and life samples.

The Selected Ion Flow Tube Method for Workplace Analyses of Trace Gases in Air and Breath: Its Scope, Validation, and Applications

Abstract We report the results of experiments that have validated our novel selected ion flow tube (SIFT) method as a rapid, real-time determination of the concentrations of trace organic vapors in air. This flow tube method relies on the soft ionization of the trace gases (to the exclusion of the major atmospheric gases) with an appropriate precursor ion species; in all these validation experiments H3O+ ions were used. Standard atmospheres were created in air of several organic vapors, including ethanol, acetone, benzene, and toluene, over the concentration range from 10 ppb to 30 ppm using both the syringe dilution and the permeation tube methods, and the concentrations were measured directly using our flow tube method. Good agreement is observed between the generated concentrations as derived by these standard methods and those measured by our flow tube method, with the regression coefficients ranging from 0.91 to 1.13, the measured values being on average about 10 percent higher than the syringe-generated concentrations and about 4 percent lower than those generated by the permeation tubes. We therefore conclude that the SIFT method is a reliable, rapid method for the simultaneous determination of concentrations of several trace gases in air in real time. This technique can now be used with confidence for biological monitoring in health and safety practice, as is well demonstrated by two simple examples of breath analysis.

Determination of active single chain antibody concentrations in crude periplasmic fractions

We have measured active single chain antibody (scFv) concentrations under mass transfer limitation conditions using surface plasmon resonance on the BIAcore. For the creation of a standard curve scFv 4Dwt, derived from monoclonal antibody (mAb) 4D, directed against human chorionic gonadotropin (hCG), was purified by positive affinity chromatography. Determination of the active antibody fraction after purification was performed using anti-FLAG, reactive against a tag sequence C-terminally fused to the scFv. Two independent experiments showed that the activity remaining represented over 75% of the total amount of purified protein. Calibration curves on high density antigen surfaces showed a linear relationship between antibody concentration and binding rates. Periplasmic fractions of six mutant scFvs, also derived from mAb 4D, revealed a clear difference in the amount of soluble active scFv expressed in the periplasm of E. coli compared with the total amount of antibody present, indicating the necessity of measuring active antibody concentrations. This rapid concentration determination method will be particularly useful for accurately comparing affinity constants, using antibody concentrations determined with the BIAcore, of the many different scFv fragments routinely isolated from phage display libraries.

Direct Graphite Furnace–Atomic Absorption Method for Determination of Lead in Edible Oils and Fats: Summary of Collaborative Study

The IUPAC Commission on Oils, Fats, and Derivatives undertook development of a method and collaborative study for the determination of lead in oils and fats by direct graphite furnace-atomic absorption spectrophotometric method. Various types of graphite furnaces were used with or without platform. Twenty-three collaborators from 12 countries participated in the study. The materials tested were edible oils (soybean oil) and fats (cocoa butter) containing lead at 3 concentration levels (low, medium, and high). Each level was represented by 2 batches provided in duplicate (blind coded), so that each collaborator received a total of 24 test samples. Collaborators were instructed to analyze each in duplicate and report both results. Twenty collaborators returned the results of the study. After data from laboratories that did not follow the instructions were excluded, only 16 sets of data were evaluated statistically. The method for determination of lead in oils and fats by direct graphite furnace-atomic absorption spectrophotometry has been adopted first action by AOAC INTERNATIONAL as an IUPAC-AOCS-AOAC method.

Trace analysis of ceramic surfaces by laser ionization mass spectrometry

Laser ionization mass spectrometry (LIMS) is an analytical method for the simultaneous determination of concentrations of trace elements in solid samples and for the analysis of layers with thicknesses >1 μm. This laser-induced surface analytical method is limited by the laser focus and crater depth of the laser system applied. Results of mass spectrometric trace analysis on a silicon carbide surface, ZrO2 and high-Tc superconducting ceramics are discussed.

Sterische Stabilisierung und Flockung von wäßrigen TiO2‐ und SiO2‐Suspensionen durch Polymerenadsorptionsschichten

AbstractThe effect of adsorbed polymers on the stability of aqueous TiO2 and SiO2 suspensions was studied by a centrifugation technique in combination with spectrophotometric particle concentration determinations. TiO2 suspensions showed a marked resistance against sedimentation following the adsorption of polyvinyl alcohol) at higher concentrations and room temperature. The sedimentation velocity was lowest at pH = 5.9. An increase or decrease of the pH or of the adsorption temperature brought about destabilization. Aqueous SiO2 suspensions could be stabilized by adsorbed poly(oxyethylene) at pH 6.8 and 7.3 but were destabilized after adsorption of this polymer at lower pH values via the formation of a viscoelastic gel structure. The observed effects are interpreted as steric stabilization in the TiO2 and SiO2 adsorption systems and as bridging flocculation in the SiO2 system at low pH. They are correlated with adsorption isotherms of the polymers established by a turbidimetric concentration determination method.

Pharmacokinetics of high-dose methotrexate in dogs. An experimental model with diffusion chambers.

The usefulness of a diffusion chamber method for determination of concentrations of cytostatic drugs in the interstitial fluid of tissues was tested. Chambers with a permeable membrane (pore size: 0.45 micrometer) were implanted in the liver, kidney, bladder wall, and prostate of dogs. After administration of high doses of methotrexate (100 mg/kg body wt) the concentrations in the chamber fluid and in serum were measured simultaneously and repeatedly for 72 h. The method proved to be effective for collecting data on the distribution of drugs in different organs. The results show that knowledge of the serum concentration does not permit predictions of the drug concentration in the interstitial fluid of various tissues to be made.

Photocolorimetric method for determination of concentration of KP-2 inhibitor in tarring mixture

Photocolorimetric method for determination of concentration of KP-2 inhibitor in tarring mixture

Radiative transfer in the ocean: a method for determination of absorption and scattering properties

Radiative transfer in the ocean: a method for determination of absorption and scattering properties

A Radiometric Method for Determination of Absorption of Ammoniated Mercury from Ointments

Ammoniated mercury-Hg 203 was prepared from mercuric chloride-Hg 203 . The labeled ammoniated mercury was incorporated into ointment bases and used to determine absorption of ammoniated mercury through intact and abraded skin of rats. Twenty-four hours after application of the ointment, both kidneys were removed and assayed for mercury content by beta and gamma radiometric rocedures. The two radiometric methods were found to give comparaile results.

Absorption of Iron as a Problem in Human Physiology A Critical Review

Absorption of Iron as a Problem in Human Physiology A Critical Review