Standard Liquid Research Articles

Development and validation of a quick assay for the total glucosinolate content in horseradish (Armoracia rusticana) using glucose strips and a blood glucose meter.

A quick assay to determine the total glucosinolate content of fresh horseradish roots in less than 10 minutes is described. The method involves the following steps: 1. Maceration of horseradish root with 4% phosphoric acid to avoid enzymatic degradation of endogenous glucosinolates, 2. neutralization of the extract and determination of free glucose using a commercial blood glucose meter, 3. enzymatic hydrolysis of the glucosinolates by exogenous myrosinase, 4. detection of released glucose, again using a blood glucose meter, and 5. calculation of the glucosinolate content on the basis of the difference between the two glucose values determined. The newly developed assay (‘ITC quick test’) was compared with a standard high-performance liquid chromatographic method for glucosinolate analysis.

Monitoring and Predicting Net Longevity by Measuring Surface Levels of Insecticide: Implementing a Faster, Cost Effective, Nondestructive, and Field-Ready Alternative to the World Health Organization Cone Test Bioassay.

An important component of malaria control programs is the ability to assess the effectiveness of the insecticide in insecticide-treated nets (ITNs) during normal usage. The standard technique to measure insecticidal activity is the World Health Organization (WHO) cone test, which in many circumstances, may be difficult to implement. We have evaluated an alternative technique, the colorimetric field test (CFT) on a group of 24-month-old Permanet® 2.0 (Vestergaard-Frandsen, Denmark) nets collected in Colombia. The CFT, which measures surface levels (SL) of deltamethrin is compared with standard high-performance liquid chromatography (HPLC) and the WHO cone test. Effective concentrations of deltamethrin for 80% mortality (EC80) were determined from the CFT and HPLC results. Distribution of insecticide SL after 24 months of use reveal that sampling of the midsection best represents the condition of the entire net. We conclude that the CFT is a practical alternative to the WHO cone test for assessing ITN efficacy.

Intercomparison of methods for measurement of dielectric properties of biological tissues with a coaxial sensor at millimeter-wave frequencies

Coaxial sensors are effective for measurement of dielectric properties of biological tissues. Several measurement methods used to derive dielectric properties have been investigated for the measurement with a coaxial sensor at microwave frequencies. While the measurement accuracy depends on the method used, there has been insufficient intercomparison of these methods and their model approximation errors. On the other hand, we have developed a coaxial sensor for the measurement of complex permittivity at millimeter-wave (MMW) frequencies of up to 100 GHz. However, the scarcity of reference data at MMW frequencies makes the validation of the measurement system difficult. Thus, it is essential to clarify the model approximation error of the method used in the measurement system, particularly at MMW frequencies. This study aims to clarify the model approximation errors of methods for dielectric property measurement using a coaxial sensor at MMW frequencies. The model approximation errors were assessed by comparing results obtained by the methods with those based on the theoretical formula of the full-wave modal expression of Maxwell’s equations. The measurement uncertainty for the theoretical formula was estimated for a standard liquid sample to clarify the contribution of the model approximation errors to the uncertainty. Furthermore, the methods were applied to the measurement of porcine tissues at body temperature, and the measurement accuracy and usability for measurement at MMW frequencies are discussed.

Swelling of samples of automotive rubber products in standard fluid, engine oil and tribotechnical compound

In this paper the change in the properties of rubber products of automobile under the influence of temperatures and when working in an aggressive environment was studied by authors. The radial tire protector samples (Barum 155/70 R13 75T Brillantis 2) with dimensions not exceeding 2×10-2×1.5×-2×5×10-3 [m], seal samples (of 2108-170342-01 type) in the form of a semicircle of 2.7·10-2×7·10-3×2·10-3 [mm] size, both original and aged rubber samples were tested. Aging was carried out in a stream of air, forcibly pumped through the reactor with the rubber placed in it. The heat treatment time was 12-100 hours, the temperature was 70-150 ° C. The change in the properties of rubber was evaluated by the parameter of the change in the mass of the samples (original and aged) after their contact with the liquid. The resistance of rubber to the action of liquids was studied, the kinetics of rubber swelling was studied. As the standard liquid the isooctane (2,2,4-trimethylpentane) was used. The experiments were carried with synthetic engine oil (SEO) “GENESIS CLARITECH” 5W-30 and tribotechnical composition (tribotechnical compounds; TC) “ACTIVE PLUS” (“suprotec”). The use of tribotechnical composition as a test fluid for rubbers was motivated by the purpose of assessing the chemical activity of the “suprotec”, when used in engines operating under conditions of high loads. The kinematic viscosity of SEO and TC was determined (in the temperature range from 20 ° C to 100 ° C) by the HPLC-4 viscometers, the density (ρ) of the liquids was measured with oil-meters. The hardness of the rubber samples was evaluated by measuring the resistance of the rubber by immersion of the indenter (a spring-loaded rod) into it. The indicator of the hour type ICh-02 (accuracy class 0) was used as a gauge.

Voltammetric determination of ethylvanillin and methylvanillin sum at carbon paste electrode modified by sodium dodecyl sulfate in selected foodstuffs

A new voltammetric method without using high cost and health risk nanomaterials has been developed for quantitative determination of ethylvanillin and methylvanillin sum, compounds that are used as food additives. The method is based on direct electrochemical oxidation of these biologically active compounds using square wave voltammetry at carbon paste electrode with surface modified by sodium dodecyl sulfate (SDS/CPE) performed in 0.1 M phosphate pH 6.0 buffer. Working conditions such as pH value of supporting electrolyte, type of surfactant, accumulation time of surfactant, and parameters of square wave voltammetry were optimized. In comparison with bare carbon paste electrode, excellent reproducibility characterized by a relative standard deviation of approximately 0.3% was obtained at the SDS/CPE. Linear range from 1.0 × 10−6 to 2.0 × 10−5 M, limits of quantification 9.8 × 10−8 M and detection 2.9 × 10−8 M were found at pulse amplitude 70 mV and frequency 50 Hz selected as optimum for ethylvanillin quantification. For methylvanillin, a linear range from 7.0 × 10−8 to 2.0 × 10−5 M and limits of quantification 7.0 × 10−8 M and detection 2.0 × 10−8 M were also determined. The procedure was validated using standard high-performance liquid chromatography method in the analysis of selected complex foodstuffs such as commercial baking sugar, biscuits, and an alcoholic drink. The results showed that a direct voltammetric approach is economically advantageous and reliable for the determination of ethyl- and methylvanillin, which is fully comparable to the reverse phase HPLC used as the ISO standard.

Systematic investigations of novel validity parameters in urine drug testing and prevalence of urine adulteration in a two-year cohort.

Urinalysis is well established for drug screening. Various methods of urine adulteration such as dilution, addition of oxidative/reductive chemicals or detergents, and handing over urine-like fluids are used to circumvent a positive screen. Validity parameters such as determination of pH, gravidity, urine temperature, or testing for oxidative/reductive chemicals are therefore used to uncover adulterated urine specimens. However, synthetic urine ("fake urine") has nowadays been used for manipulations, leading to inconspicuous results with common validity test systems. Therefore, the aims of the study were (a) to evaluate additional validity parameters, (b) to evaluate the prevalence of urine adulteration, (c) to identify adulteration markers in purchased fake urine samples. Urine samples (n=550) submitted for drug abstinence testing were analyzed by a standard urine liquid chromatography-tandem mass spectrometry (LC-MS/MS) screening approach using library-assisted identification of 10 different endogenous biomolecules. The detection rates of biomolecules in authentic samples were phenylalanine (93.4%), tryptophan (97.1%), propionyl-carnitine (67.1%), butyryl-carnitine (99.6%), isovaleryl-carnitine (92.8%), hexanoyl-carnitine (91.0%), heptanoyl-carnitine (97.1%), octanoyl-carnitine (98.9%), and indoleacetylglutamine (98,2%). Phenylacetylglutamine was detected in each authentic sample. Based on the detection rates and measured creatinine levels, six manipulated samples were identified in this study. In two cases, fake urine was handed over, one time fake urine was most likely used for dilution. Once dilution with other fluids was used as adulteration method, while in another sample a detergent solution was handed over. Additionaly, one sample contained reactive chemicals. All fake urine samples were additionally identified by the detection of unique polyglycole patterns, which were observed in purchased fake urine samples.

A study on the geometry of sinkers used for calibration of hydrometers with the ring method

The geometry of three types of sinkers used during the calibration of hydrometers by the ring method in a density standard liquid was studied. An experiment was designed with two factors: the geometry and the metrologist, with three levels for the geometry of sinkers and two levels for the metrologist factor. Even when the variable under study was the geometry, it was useful to observe the variation due to the metrologist when same method, system, hydrometer, and the temperature was used (reproducibility of the metrologist). Two response variables were monitored: the measurement bias and the time to carry out the calibration at one point. The calibration point selected was the closest point to the sinker in the measurement scale. The results show that the best geometry regarding measurement bias also results in the worst geometry regarding the productivity of the calibration laboratory, that is, the geometry which gives the lower time for calibration is also the geometry with the bigger measurement bias, and vice versa. These results allow the calibration laboratories to choose the best trade-off design of the sinkers to use for calibration of hydrometers in a density standard liquid.

New determination of the 229Th half-life.

A new determination of the 229Th half-life was made based on measurements of the 229Th massic activity of a high-purity solution for which the 229Th molality had previously been measured. The 229Th massic activity was measured by direct comparison with SRM 4328C using 4παβ liquid scintillation counting, NaI counting, and standard addition liquid scintillation counting. The massic activity was confirmed by isotope dilution alpha spectrometry measurements. The calculated 229Th half-life is (7825 ± 87) years (k = 2), which is shorter than the three most recent half-life determinations but is consistent with these values within uncertainties.

Rapid SERS detection of acid orange II and brilliant blue in food by using Fe3O4@Au core–shell substrate

With the widespread application of synthetic pigments in the food industry, food safety incidents caused by illegal addition of pigments have become more frequent. In this study, we synthesized core–shell nanomaterials for use in sensitive, fast, convenient, nondestructive detection and having good surface-enhanced Raman scattering (SERS) effect. The optimal synthetic conditions were selected to study semi-quantitative detection. Calculations for acid orange II and brilliant blue were done using density functional theory, and the characteristic peaks and vibration conditions for each pigment were identified. Acid orange II and brilliant blue in the food samples yellow croaker, braised pork, red pepper, green dumpling, and red wine were detected by SERS screening. Results were compared with those obtained by standard high-performance liquid chromatography method in order to verify the SERS method. The core–shell nanoparticles showed good performance in the rapid detection of pigments in food.

A microfluidic sensor in coplanar waveguide configuration for localized micrometric liquid spectroscopy in microwaves regime

In this work, we present a sensor suitable for performing the spectroscopy on a localized micrometric volume of a generic liquid, in the spectral range comprised between 1 and 20 GHz. The sensor is based on two ungrounded, open-ended coplanar waveguides, acting as Input/Output ports, with a microfluidic channel passing through them. It works by detecting the change of the reflection and transmission of microwaves due to the variation of the dielectric properties characteristic of the liquid. The devices have been designed and numerically simulated to obtain the electromagnetic response in different conditions: an empty channel for having a zero-reference response and for observing variations as a function of liquids filling the channel. We considered standard (i.e., common in literature) liquids (deionized water, ethanol, and glycerol); by means of that set of simulations we were able to start the creation of the calibration curves and defining the sensitivity of the sensor with respect to dielectric properties of the liquid under test. Then, we realized a batch of prototypes utilizing a standard photolithographic process. Later we proceeded to check the operation of the sensors. We recorded experimental data by a Vector Network Analyser connected to the devices by means of microwave probes. Sensors are designed to perform both reflection and transmission measurements on the liquid sample, and local microscopy on a micrometric volume of the solution under test. Actually, the device works avoiding any contact between the metallic parts and the liquid that can flow uncontaminated through the microfluidic channel.

A modified sandwich ELISA for accurate measurement of HbF in α-thalassemia carriers containing Hb Bart’s and Hb Portland 1

ABSTRACTHemoglobin F (HbF) in blood lysate can be accurately measured by various methods, including immunoassay. In this study, we have produced polyclonal antibody (pAb) against HbF and established a modified sandwich-type ELISA for HbF quantification in blood lysates. The modified sandwich ELISA utilized anti-γ-globin monoclonal antibody clones Thal N/B as the capture antibody (Ab) coated on solid-phase, fluorescein isothiocyanate (FITC)-labeled pAb as the detecting Ab, and HPR-labeled anti-FITC Ab as the signal-generating Ab. By using an optimized blood lysate dilution, the HbF could be measured with no interference from hemoglobin Bart’s (Hb Bart’s) and hemoglobin Portland (Hb Portland 1) presented in α-thalassemia carriers. HbF levels measured by the modified sandwich ELISA were comparable to those quantified by the standard cation-exchange high performance liquid chromatography. We suggested that this modified sandwich ELISA was able to accurately measure HbF levels even in α-thalassemia carriers containing Hb Bart’s and Hb Portland 1 and be an alternative method for HbF measurement.

Bare carbon electrodes as simple and efficient sensors for the quantification of caffeine in commercial beverages.

Food quality control is a mandatory task in the food industry and relies on the availability of simple, cost-effective and stable sensing platforms. In the present work, the applicability of bare glassy carbon electrodes for routine analysis of food samples was evaluated as a valid alternative to chromatographic techniques, using caffeine as test analyte. A number of experimental parameters were optimized and a differential pulse voltammetry was applied for quantification experiments. The detection limit was found to be 2 × 10−5 M (3σ criterion) and repeatability was evaluated by the relative standard deviation of 4.5%. The influence of sugars, and compounds structurally related to caffeine on the current response of caffeine was evaluated and found to have no significant influence on the electrode performance. The suitability of bare carbon electrodes for routine analysis was successfully demonstrated by quantifying caffeine content in seven commercially available drinks and the results were validated using a standard ultra-high performance liquid chromatography method. This work demonstrates that bare glassy carbon electrodes are a simple, reliable and cost-effective platform for rapid analysis of targets such as caffeine in commercial products and they represent therefore a competitive alternative to the existing analytical methodologies for routine food analysis.

Leidenfrost Self-Rewetting Drops.

As discovered by Leidenfrost, liquids placed on very hot solids levitate on a cushion of their own vapor. This is also called the calefaction phenomenon, a dynamical and transient effect, as vapor is injected below the liquid and pressed by the drop weight. To account for the film vapor, we consider the surface tension magnitude as well as the Marangoni effect (in particular the thermal one) which arise with imbalance of surface tension forces. For standard liquids, these forces contribute to amplify the thickness of the film layer and the levitation of the droplet. Our findings imply the ability of recent binary mixture liquids, called self-rewetting fluids, to reduce the vapor film thickness and demonstrate the powerful influence exerted by different binary mixtures to enhance the heat transfer at high temperature. Such self-rewetting fluids are presenting a high value of surface tension at high temperature, and in which the Marangoni forces are inversed as from critical temperature. We consider our assay to be a way for improvement in the high temperature mass cooling applications.

Chromatographic characterisation of 11 phytocannabinoids: Quantitative and fit-to-purpose performance as a function of extra-column variance.

Cannabis sativa L. (cannabis) is utilised as a therapeutic and recreational drug. With the legalisation of cannabis in many countries and the anticipated regulation of potency that will accompany legalisation, analytical testing facilities will require a broadly applicable, quantitative, high throughput method to meet increased demand. Current analytical methods for the biologically active components of cannabis (phytocannabinoids) suffer from low throughput and/or an incomplete complement of relevant phytocannabinoids. To develop a rapid, quantitative and broadly applicable liquid chromatography-tandem mass spectrometry analytical method for 11 phytocannabinoids in cannabis with acidic and neutral character. Bulk diffusion coefficients were calculated using the Taylor-Aris open tubular method, with four reference compounds used to validate the experimental set-up. Three columns were quantitatively evaluated using van Deemter plots and fit-to-purpose performance metrics. Low (1.2μL2 ) and standard (3.6μL2 ) extra-column variance ultra-high pressure liquid chromatography (UPLC) configurations were contrasted. Method performance was demonstrated with methanolic cannabis flower extracts. Bulk diffusion coefficients and van Deemter plots for 11 phytocannabinoids are reported. The developed chromatographic method includes the challenging Δ8 /Δ9 -tetrahydrocannabinol isobars and, at 6.5min, is faster than existing methods targeting similar panels of biologically active phytocannabinoids. The bulk diffusion coefficients and van Deemter curves informed the development of a rapid quantitative method and will facilitate potential expansion to include additional compounds, including synthetic cannabinoids. The developed method can be implemented with low or standard extra-column variance UPLC configurations.

Determination of vitamin K1 using square wave adsorptive stripping voltammetry at solid glassy carbon electrode

A new electroanalytical method for determination of phylloquinone (vitamin K1) occuring in food samples of plant origin has been developed. Presented method is based on adsorptive accumulation of this biologically active compound onto the surface of solid glassy carbon electrode with subsequent electrochemical detection using square wave adsorptive stripping voltammetry in 0.1 M HCl. Two linear ranges of phylloquinone determination were 1.0 × 10−8–1.0 × 10−6 mol L−1 and 5.0 × 10−6–1.0 × 10−4 mol L−1 with the detection limits of 8.9 × 10−9 and 5.1 × 10−8 mol L−1, respectively. Obtained results have shown that square wave voltammetry with adsorptive accumulation step is very sensitive method for the determination of vitamin K1, being comparable to standard high performance liquid chromatography method for food analysis (EN 14148:2003).

Analisis Kandungan Nitrogen (N) dan Posforus (P) pada Limbah Jeroan Ikan Mujair (Oreochromis mosambicus) Danau Lindu

An effort to minimize the environmental pollution is using that waste as a base material of organic fertilizer. This study was conducted to determine the levels of Nitrogen (N) and phosphorous (P) contained in the offal waste of mujair fish (Oreochromis mosambicus) from Lindu lake. Samples of mujair offal waste were taken from fish saler on the street Towua, Palu. Analysis of Nitrogen levels usedKjeldhal method which consists of three phases, namely destruction, distillation, and titration. On the other hand, for Phosphorus analysis was using wet digestion method, followed by absorbance measurements of samples with spectronic 20 at a wavelength of 720 nm. Based on the analysis, the average of nitrogen (N) levels in mujair offal waste was 2.78%, while the average of phosphorus (P) levels was 2.48%. From these results, it is known that mujair offal waste contains more nitrogen (N) compared to phosphorous (P). In addition, when compared to the quality standard liquid organic fertilizer N and P content in mujair offal almost meets the quality standard liquid fertilizer, where the minimum technical requirements of organic liquid fertilizer should contain a total N content of 3-6% and 3-6% P2O5.

Rapid amino acid quantitation with pre-column derivatization; ultra-performance reverse phase liquid chromatography and single quadrupole mass spectrometry

BackgroundWe optimized a quantitative amino acid method with pre-column derivatization, norvaline (nva) internal standard and reverse phase ultra-performance liquid chromatography by replacing the ultraviolet detector with a single quadrupole mass spectrometer (MSnva). MethodWe used 13C15N isotopically labeled amino acid internal standards and a C18 column with 1.6μm particles to optimize the chromatography and to confirm separation of isobaric compounds (MSlis). We compared the analytical performance of MSnva with MSlis and the original method (UVnva) with clinical samples. ResultsThe chromatography time per sample of MSnva was 8min, detection capabilities were <1μmol/L for most components, intermediate imprecisions at low concentrations were <10% and there was negligible carryover. MSnva was linear up to a total amino acid concentration in a sample of approximately 9500μmol/L. The agreements between most individual amino acids were satisfactory compared to UVnva with the latter prone to outliers and suboptimal quantitation of urinary arginine, aspartate, glutamate and methionine. MSnva reliably detected argnininosuccinate, β-alanine, citrulline and cysteine-s-sulfate. ConclusionMSnva resulted in a more than fivefold increase in operational efficiency with accurate detection of amino acids and metabolic intermediates in clinical samples.

A large coaxial reflection cell for broadband dielectric characterization of coarse-grained materials

Knowledge of the frequency-dependent electromagnetic properties of coarse-grained materials is imperative for the successful application of high frequency electromagnetic measurement techniques for near and subsurface monitoring. This paper reports the design, calibration and application of a novel one-port large coaxial cell for broadband complex permittivity measurements of civil engineering materials. It was designed to allow the characterization of heterogeneous material with large aggregate dimensions (up to 28 mm) over a frequency range from 1 MHz–860 MHz. In the first step, the system parameters were calibrated using the measured scattering function in a perfectly known dielectric material in an optimization scheme. In the second step, the method was validated with measurements made on standard liquids. Then the performance of the cell was evaluated on a compacted coarse-grained soil. The dielectric spectra were obtained by means of fitting the measured scattering function using a transverse electromagnetic mode propagation model considering the frequency-dependent complex permittivity. Two scenarios were systematically analyzed and compared. The first scenario consisted of a broadband generalized dielectric relaxation model with two Cole–Cole type relaxation processes related to the interaction of the aqueous phase and the solid phase, a constant high frequency contribution as well as an apparent direct current conductivity term. The second scenario relied on a three-phase theoretical mixture equation which was used in a forward approach in order to calibrate the model. Both scenarios provide almost identical results for the broadband effective complex relative permittivity. The combination of both scenarios suggests the simultaneous estimation of water content, density, bulk and pore water conductivity for road base materials for in situ applications.

Detection of Thermospermine and Spermine by HPLC in Plants.

Thermospermine, a structural isomer of spermine, is widely spread in the plant kingdom and has recently been shown to play a key role in the repression of xylem differentiation in vascular plants. However, a standard high-performance liquid chromatography (HPLC) protocol for detecting polyamines as their dansyl derivative cannot distinguish themospermine from spermine. These isomers become separated from each other after benzoylation. In this chapter, we describe a simple protocol for extraction, benzoylation, and HPLC detection of thermospermine and spermine with other polyamines from plant material.

A temperature compensated dielectric test cell for accurately measuring the complex permittivity of liquids.

A measurement of the complex permittivity, εr, of a liquid can give valuable information about the molecular polarizability and dielectric losses. This can be obtained by means of an impedance measurement using a parallel plate test cell. However, highly accurate and precise measurements are challenging, in particular when measuring as a function of temperature. Thermal expansion affects the geometry of a test cell and thus the measured capacitance from which εr is calculated. In this paper, a broadband four-terminal dielectric test cell is presented that is insensitive to temperature fluctuations. This was achieved by means of a cell geometry exploiting the thermal expansion coefficient of different materials. Experimental measurements on the manufactured cell yielded a stable capacitance of 35.322 ± 0.001 pF across 20 °C-90 °C. The capacitance stayed within ±0.01 pF over multiple experimental cycles of cleaning and assembly. A finite element modeling showed a theoretical accuracy in measuring εr better than 99.995%. The measured εr values for a number of standard liquids showed an agreement of 99.7% compared to literature values.