Minimum Measurable Concentration Research Articles

Оптимізація пробопідготовки для визначення 90SR У харчових продуктах

The aim: To determine the possibility of conducting studies of the radionuclide 90Sr in food products in accordance with GN 6.6.1.1-130-2006 «Permissible levels of radionuclides 137Cs and 90Sr in food products and drinking wate»" without concentration by the ashing method. Materials and methods: The article describes the method of calculating the minimum measuring concentration of food products. According to the results of the calculations, the products that can be measured without concentration are determined. Analytical, statistical and computational research methods were used during the work. At the stage of sample preparation for measurement, the question often arises in which form to measure the sample - native or ashed. The specific activities of food products in their native form are in many cases lower than the minimum measurable concentration (MMС) on the spectrometer. Therefore, in order to decide in what form to prepare the sample for research, before starting work, it is necessary to compare the capabilities of the spectrometer, the minimum measured concentration and the permissible level of 90Sr content in the research product. In order to solve the question of the need for ashing of the sample, calculations of MMC were carried out for each food product, as well as the weight of the raw product, necessary to obtain 0.01 kg of ash per measurement was calculated. Results: Tables are compiled based on the results of the calculations. One includes products whose activity can be measured without ashing, and the other includes products with ashing. The use of such tables makes it possible to optimize sample preparation for the study of 90Sr by the spectrometric method. Of the 50 groups of food products, 17 have been identified that can be studied in their native form, which saves time for sample preparation and increases the performance of the spectrometer.

Resonant Measurement of Coaxial Probe Based on Tunable Impedance Matching Network

In this work, we first present a tunable impedance matching network (IMN) to produce an outstanding resonance for improving the sensitivity of coaxial probes. A two-port network based on a three-line coupled (TLC) structure along with a tunable phase shifter is designed to realize conjugate matching. The calculated shape factor for characterizing the sharpness of resonance can be up to 1.4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{5}$</tex-math> </inline-formula> when deionized (DI) water is loaded. The minimum measurable concentration level of ethanol is 0.005 mole fraction. The conventional probe’s sensitivity is enhanced to be comparable with those achieved by other resonance-based sensing methods. Using calibration liquids, the complex permittivity of a liquid can be extracted.

Development of a Spatial Heterodyne Terahertz Raman Spectrometer with Echelle Gratings

This paper introduces an echelle grating spatial heterodyne terahertz Raman spectrometer (E-SHTRS) that combines echelle gratings with spatial heterodyne terahertz Raman spectroscopy technology by replacing the gratings on the interference arms with 36 gr/mm echelle gratings. Echelle gratings are characterized by high diffraction levels and multi-level simultaneous diffraction capability, giving the E-SHTRS higher spectral resolution and a wider detection band range than the conventional spectrometer. The system’s resolution can reach 1.37 cm−1. The spectral detection range of a single level of the proposed system is 701.61 cm−1. A total of nine levels are used in the system, giving a total spectral detection range of 6314 cm−1. Using this system, terahertz Raman spectroscopy of organic acid samples was performed, some food additives and medicines were measured, and a salicylic acid aqueous solution was measured with a minimum measurable concentration of 0.01 mol/L. In addition, the samples were detected over a wide band (10–5131 cm−1) to acquire more complete spectral information. These experiments verify that the E-SHTRS offers good detection performance and has a wide range of possible applications, including a theoretical support role in food safety, biomedicine, environmental protection, and other fields.

Microfluidic Biosensor for Rapid Nucleic Acid Quantitation Based on Hyperspectral Interferometric Amplicon-Complex Analysis.

Nucleic acid detection plays a vital role in both biomedical research and clinical medicine. The temperature circulation changes of the widely used polymerase chain reaction technique are time-consuming and technically challenging for system development. Recombinase polymerase amplification (RPA) is an isothermal method for rapid nucleic acid detection. However, current RPA amplicon detection methods are complicated and expensive and easily generate false positives, restricting the promotion of RPA techniques. In this work, a hyperspectral interferometric amplicon-complex quantitation method is presented, combined with asymmetric dipole complex strategy optical scattering analysis. GelRed dye was utilized to form amplicon-complex particles, and the Fourier domain spectrum computation contributed to complex scattering quantitation. With this method, a supporting microfluidic chip and automatic system were developed to achieve integrated, rapid, quantitative, and miniscule nucleic acid detection. The Plasmodium falciparumdhfr gene was utilized as an example for targeted nucleic acid quantitation and single nucleotide polymorphism detection. The total reaction time was decreased to merely 20 min, and the limit of detection was only 3.17 ng/μL. The minimum measurable concentration of target was 1.68 copies/μL, 31.67 times more sensitive than turbidity detection, and the single reaction chamber was only 9.33 μL. No scattering increase occurred for template-free control, and thus, false positives caused by primer dimers and nonspecific products could be avoided. The experimental results prove that the provided method and system can detect single-base mutations in the dhfr gene and is a reasonable technique for rapid, automatic, and low-cost nucleic acid detection.

Quantitative measurements of singlet molecular oxygen in a low pressure ICP

We present measurements of the densities and temperatures (rotational and translational) of the metastable a1Δg (v = 0) state of O2 in a cylindrically symmetric RF driven plasma operating in inductive mode at 100 mTorr total pressure and 300 W applied power. Line-of-sight absorption across the plasma region was determined by diode laser cavity ringdown spectroscopy on the (0, 0) vibrational band of the O2(b1Σg +) ← O2(a1Δg) transition near 1.9 μm. Four rotational quantum states were studied, with a population distribution corresponding to a rotational temperature of 346 ± 38 K. The translational temperature was determined to be 359 ± 16 K from the width of the strongest absorption line, Q(12), and in equilibrium with the rotational distribution. The absolute concentration of O2(a1Δg, v = 0) was measured as (9.5 ± 1.3) × 1013 cm−3, and corresponds to an apparent (3.5 ± 0.45)% contribution to the total number density. Time-resolved CRDS measurements following plasma extinction were used to deduce a wall loss coefficient, γ, of (2.8 ± 0.3) × 10−3 on predominantly Al surfaces. Surmising reasonable concentrations for O2(b1Σg +) and an upper limit for the vibrational temperature places the total contribution of O2(a1Δg) at between 3.6% and 5.85%. The variation of the O2(a1Δg, v = 0) state concentration with RF power shows a clear transition from the E to H mode excitation near an applied power of 150 W. Allan variance analysis yields a minimum measurable concentration of O2(a1Δg, v = 0) of 1.1 × 1012 cm−3 over 100 ringdown events, an order of magnitude more sensitive than previously reported.

Multi-volume hemacytometer

Cell counting has become an essential method for monitoring the viability and proliferation of cells. A hemacytometer is the standard device used to measure cell numbers in most laboratories which are typically automated to increase throughput. The principle of both manual and automated hemacytometers is to calculate cell numbers with a fixed volume within a set measurement range (105 ~ 106 cells/ml). If the cell concentration of the unknown sample is outside the range of the hemacytometer, the sample must be prepared again by increasing or decreasing the cell concentration. We have developed a new hemacytometer that has a multi-volume chamber with 4 different depths containing different volumes (0.1, 0.2, 0.4, 0.8 µl respectively). A multi-volume hemacytometer can measure cell concentration with a maximum of 106 cells/ml to a minimum of 5 × 103 cells/ml. Compared to a typical hemacytometer with a fixed volume of 0.1 µl, the minimum measurable cell concentration of 5 × 103 cells/ml on the multi-volume hemacytometer is twenty times lower. Additionally, the Multi-Volume Cell Counting model (cell concentration calculation with the slope value of cell number in multi-chambers) showed a wide measurement range (5 × 103 ~ 1 × 106 cells/ml) while reducing total cell counting numbers by 62.5% compared to a large volume (0.8 µl-chamber) hemacytometer.

Highly sensitive long range surface plasmon based liquid sensor by shining the radially polarized light in bimetallic taper fiber structure

A new approach towards the enhancement of sensitivity in fiber optic liquid sensor is proposed, designed and simulated using the long range surface plasmon resonance technique shining the radially polarized light in bimetallic fiber structure, which comprises a fiber core coated with 40 nm and 10 nm thin Ag and Au layer respectively. The radially outward field distribution of the radially polarized light enables the multiple point plasmonic interaction on the whole fiber periphery which enhances the sensitivity as well as the dynamic range of refractive index sensing through the proposed sensor. A 13 times and 25 times better sensitivity has been estimated using NaCl and KCl solution as compared with the existing articles till date using p-polarized light. Minimum measurable concentration is 0.5 g/l and 1 g/l for NaCl and KCl solutions for a minimum change in output power of 30.04 μW and 25.60 μW respectively using InGaAs detector. With enhanced sensitivity and higher dynamic range of refractive index, this new idea explores the new avenues in the field of fibre optic liquid sensing applications.

LA-ICP-MS of rare earth elements concentrated in cation-exchange resin particles for origin attribution of uranium ore concentrate

Rare earth elements (REE) concentrated on cation-exchange resin particles were measured with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to obtain chondrite-normalized REE plots. The sensitivity of REE increased in ascending order of the atomic number, according to the sensitivity trend in pneumatic nebulization ICP-MS (PN-ICP-MS). The signal intensities of REE were nearly proportional to the concentrations of REE in the immersion solution used for particle-preparation. Minimum measurable concentration calculated from the net signals of REE was approximately 1ng/g corresponding to 0.1ng in the particle-preparation solution. In LA analysis, formation of oxide and hydroxide of the light REE and Ba which causes spectral interferences in the heavy REE measurement was effectively attenuated due to the solvent-free measurement capability, compared to conventional PN-ICP-MS. To evaluate the applicability of the proposed method, the REE-adsorbed particles prepared by immersing them in a U-bearing solution (commercially available U standard solution) were measured with LA-ICP-MS. Aside from the LA analysis, each concentration of REE in the same U standard solution was determined with conventional PN-ICP-MS after separating REE by cation-exchange chromatography. The concentrations of REE were ranging from 0.04 (Pr) to 1.08 (Dy) μg/g-U. The chondrite-normalized plot obtained through LA-ICP-MS analysis of the U standard sample exhibited close agreement with that obtained through the PN-ICP-MS of the REE-separated solution within the uncertainties.

Silica-coated super paramagnetic iron oxide nanoparticles (SPION) as biocompatible contrast agent in biomedical photoacoustics

In this study, we report for the first time the use of silica-coated superparamagnetic iron oxide nanoparticles (SPION) as contrast agents in biomedical photoacoustic imaging. Using frequency-domain photoacoustic correlation (the photoacoustic radar), we investigated the effects of nanoparticle size, concentration and biological media (e.g. serum, sheep blood) on the photoacoustic response in turbid media. Maximum detection depth and the minimum measurable SPION concentration were determined experimentally. The nanoparticle-induced optical contrast ex vivo in dense muscular tissues (avian pectus and murine quadricept) was evaluated and the strong potential of silica-coated SPION as a possible photoacoustic contrast agents was demonstrated.

Side-by-side comparison of automatic pollen counters for use in pollen information systems

Recent effort to build an unmanned pollen monitoring network in Japan has led to new developments in automatic pollen counters. In-the-field performance tests of these automatic counters have not been reported. To characterize recently developed automatic pollen counters, with a view of using their data in pollen information systems. We performed side-by-side comparisons between 2 recently developed automatic pollen counters and 2 reference samplers at 2 sites during the 2005 pollen season. Both automatic counters were found to have similar overall performance in terms of their correlations with the reference samplers. The linear correlation coefficient between the hourly values of the counters and one of the reference samplers was larger than 0.8 at both sites for both counters. Although these results are encouraging, our analysis also points to weaknesses of the investigated automatic counters in the areas of pollen discrimination, minimum measurable concentration, and calibration. Both counters were found to be affected by large concentrations of particulate matter, although the conditions and extent to which the particulate matter disrupted the measurements differ for the 2 sensors. The effect of particulate matter is particularly noticeable at the start and end of the pollen season, that is, when pollen concentration is low relative to particulate matter concentration. Further, it was found that one of the automatic counters could not differentiate snow particles from pollen grains. The tested automatic pollen counters had good overall performances, but weaknesses in the areas of pollen discrimination, minimum measurable concentration, and calibration still have to be addressed for these counters to find widespread use in the allergy community.

Quantum cascade laser-based integrated cavity output spectroscopy of exhaled nitric oxide

A nitric oxide (NO) sensor employing a thermoelectrically cooled, continuous-wave, distributed feedback quantum cascade laser operating at 5.47 μm (1828 cm-1) and off-axis integrated cavity output spectroscopy was used to measure NO concentrations in exhaled breath. A minimum measurable concentration (3σ) of 3.6 parts-per-billion by volume (ppbv) of NO with a data-acquisition time of 4 s was demonstrated. Five prepared gas mixtures and 15 exhaled breath samples were measured with both the NO sensor and for intercomparison with a chemiluminescence-based NO analyzer and were found to be in agreement within 0.6 ppbv. Exhaled NO flow-independent parameters, which may provide diagnostic and therapeutic information in respiratory diseases where single-breath measurements are equivocal, were estimated from end-tidal NO concentration measurements collected at various flow rates. The results of this work indicate that a laser-based exhaled NO sensor can be used to measure exhaled nitric oxide at a range of exhalation flow rates to determine flow-independent parameters in human clinical trials.

IMAZALIL ON-LINE CONTROL IN POST-HARVEST TREATMENTS OF CITRUS FRUIT

Penicillium digitatum and Penicillium italicum represent the main causes of post-harvest loss in citrus fruit for medium and long term storage. They can be controlled using fungicide as Imazalil, (IMZ) and fruits are generally treated on-line in the packing line. One of the more effective treatments is the fruit immersion in a tub located on the packing line after the fruit dumping. However, at the present the fungicide concentration during the whole day, related to the amount of fruit packed in the line, is not controlled. The aim of this work has been to set up a technique to monitor the Imazalil concentration in the washing tubs used for the dip treatment of citrus fruits. With this aim, several parameters of the water/Imazalil solution have been tested, as pH, conductivity and redox potential, but they have shown no correlation with the Imazalil concentration. Then the spectrophotometry has been used to assay the Imazalil concentration: sample solutions (0.5 to 250 ppm) have been exposed to ultraviolet (UV) and near infrared (NIR) wavelengths. The tests performed have shown that NIR gives good correlation between Imazalil and the prediction model: the standard error of correlation (SEC) is 0.6 and the standard error of validation (SEV) is 3.7, such errors are acceptable both for the quick analysis method and for the minimum measurable concentration. Then UV has been successfully employed for the quick determination of the Imazalil concentration (SEC= 0.6, SEV= 1.5), then it was built a feedback control system that controls the variation of the IMZ concentration in the tub at a rate of 3.2 ppm per minute: this is accurate enough for most application and particularly for the purpose of constantly monitoring the IMZ concentration in dipping tubs for citrus fruits.

Long period gratings in multimode optical fibers: application in chemical sensing

We propose and demonstrate a new technique for evanescent wave chemical sensing by writing long period gratings in a bare multimode plastic clad silica fiber. The sensing length of the present sensor is only 10 mm, but is as sensitive as a conventional unclad evanescent wave sensor having about 100 mm sensing length. The minimum measurable concentration of the sensor reported here is 10 nmol/l and the operating range is more than 4 orders of magnitude. Moreover, the detection is carried out in two independent detection configurations viz., bright field detection scheme that detects the core-mode power and dark field detection scheme that detects the cladding mode power. The use of such a double detection scheme definitely enhances the reliability and accuracy of the results. Furthermore, the cladding of the present fiber need not be removed as done in conventional evanescent wave fiber sensors.

Mechanized assay of plasma prekallikrein by activation with Pseudomonas aeruginosa elastase and amidolysis of chromogenic substrate

An automated assay of plasma prekallikrein is described. Prekallikrein was converted to kallikrein with Pseudomonas aeruginosa elastase, and the hydrolytic activity of kallikrein to H-D-Pro-Phe-Arg-paranitroanilide subsequently measured. The conversion was complete within 8 minutes and the amidolytic activity remained stable at least another 10 min at 37 ° C. This method worked in plasma deficient in Hageman factor (blood coagulation factor XII). Using anti-prekallikrein antibody and plasma deficient in prekallikrein, the amidolytic activity generated in normal plasma was identified as due to kallikrein. With plasma samples, the coefficients of variation (CV) for multiple measurements within run ( n = 10) and between run ( n = 10) were as low as 5.0% and 6.6%, respectively, and the minimum measurable concentration of prekallikrein in plasma was 10% of the normal level.

Simplified determination of antipyrine clearance by liquid chromatography of a microsample of saliva or plasma.

We describe a simplified and rapid liquid chromatographic determination of antipyrine clearance (CLAP) calculated from peak height ratios of drug/internal standard. Saliva or plasma was collected 24 hr after the oral administration of 1 g of antipyrine to the subject. A 25-microliter aliquot of the sample is deproteinized with acetonitrile containing 3-nitrophenol (internal standard) and injected into a radial compression module equipped with a 10-micron, 8 mm x 10-cm C18 cartridge, using a 0.025 M aqueous solution of sodium acetate and acetonitrile (88.5:11.5). The minimum measurable concentration was 0.2 microgram/ml. The obtained CLAP values in five healthy subjects and five patients with chronic liver disease coincided well (r greater than 0.9994) with those generated by the use of an established method. The antipyrine clearance in the healthy subjects ranged from 2.203 to 5.721 liters/hr, while in patients with chronic liver disease it was significantly (P less than 0.0027) less (range, 0.544 to 1.103 liter/hr). We also determined antipyrine clearance in two of these subjects given lower doses of this drug and found that the dose has no significant impact on this parameter.

A Modified Assay for Cyclosporin in Blood Using Solid-Phase Extraction with High-Performance Liquid Chromatography

A modified procedure for measuring cyclosporin in whole blood by high-performance liquid chromatography is described and evaluated for clinical use. Sample preparation uses solid-phase extraction cartridges that can be reused. Life of the reverse-phase analytical column exceeds 1,000 injections at 70 degrees C. Cyclosporins A and D (internal standard) elute after 5.6 and 7.6 min, respectively. Calibration plots are linear from 50 ng/ml to at least 2,000 ng/ml. Within-day and between-day imprecision is less than 9% (coefficient of variation). Minimum measurable concentration is 50 ng/ml.

Biosensors for environmental control

Abstract

Use of a copper-phthalocyanine membrane electrode for rapid preliminary detection of polycyclic mutagens

Preliminary screening of polycyclic mutagens is achieved within 20 min by using a biomimetic electrode composed of an oxygen electrode and a copper-phthalocyanine membrane. When benzo[α]pyrene (0.05 mM) was added to the buffer solution in the presence of 0.98 M hydrogen peroxide, the current of the phthalocyanine electrode decreased. A linear relationship was obtained between the current decrease and the benzo[α]pyrene concentration over the range 0.19–0.60 mM. The minimum measurable concentration for benzo[α]pyrene was 0.01 mM. Such responses were not obtained for other organic compounds such as alcohol, ether, n-hexane and cyclohexane. The copper-phthalocyanine membrane electrode has selectively detected polycyclic mutagens such as amino acid pyrolysis products. The current decrease was 1.18–1.46 μA when 0.05 mM amino acid pyrolysis products were employed.

Determination of gold by atomic absorption spectrometry after extraction into the non-desulphurized fraction of crude oil distillate

The extraction of gold from aqueous chloride solutions into non-desulphurized fractions of crude oil distillates, especially paraffin oil, is described. The fraction boiling at 150–220°C exhibited optimum properties. The extraction is tested for solutions containing chlorides, dissolved chlorine and 0.1–3 M hydrochloric acid. Nitric acid should be absent. The distribution coefficient of gold varies from 400 to 900. Extracts containing ⩽ 0.3 g l −1 gold are stable for at least 12 months. The organic extract is sprayed into a lean acetylene/air flame with measurement at 242.8 nm (background correction). The calibration graph has linear portions over the ranges 0–2.5 and 2.5–16 mg l −1. The limit of detection is 0.03 mg l −1 gold in the extract (0.001 mg l −1 in the aqueous phase). The minimum measurable concentration for gold in auriferous rocks and ores is 0.018 g per ton with 25-g samples.

Immobilized antibody-based flow type enzyme immunosensor for determination of human serum albumin

A flow-type enzyme immunosensor was prepared for the electrochemical determination of human serum albumin (HSA). The immunosensor was constructed from the immobilized antibody (anti-HSA IgG) reactor and an oxygen electrode. The immunochemical reaction of catalase-labelled antibody with HSA was completed with 30 min. After the immunochemical reaction, hydrogen peroxide solution was injected into the system and a peak current was obtained within 2 min. A linear relationship was observed between the current increase and the logarithm of HSA concentration in the range 10 −8-10 −6 g ml −1. The minimum measurable concentration was 10 −8 g ml −1. The current increase was reproducible with 10% of the relative errors when a sample solution containing 10 −7 g ml −1 of HSA was used. The minimum measurable concentration increased to 10 −9 g ml −1 when hydrogen peroxide was recycled for 5 min in the reactor system. The immobilized antibody reactor could be reused. HSA in human serum was determined by the system proposed.