Showing papers on "Calibration curve published in 2010"

Adaptive calibration system for spectrophotometric measurements

Abstract: This disclosure describes, among other features, systems and methods for customizing calibration curves, parameter algorithms, and the like to individual users. An initial calibration curve generated based on a population can be used as a starting point in an algorithm for measuring a physiological parameter such as glucose. The measurement algorithm can determine one or more initial measurement values for a user based on the initial calibration curve. In certain embodiments, one or more alternative measurements, such as invasive or minimally invasive measurements, can periodically or sporadically be input into the measurement algorithm. The algorithm can use the alternative measurements to adapt the calibration curve to the individual. As a result, measurements for the individual can more accurately reflect the individual's actual parameter values.

High‐precision calibration of spectrographs

Abstract: We present the first stringent tests of a novel calibration system based on a laser frequency comb (LFC) for radial velocity measurements. The tests were obtained with the high-resolution, optical spectrograph, High Accuracy Radial velocity Planet Searcher. By using only one echelle order, we obtain a calibration repeatability of 15 cm s −1 for exposures that are several hours apart. This is comparable with a simultaneous calibration using a Th–Ar lamp that makes use of all 72 echelle orders. In both cases, the residuals are compatible with the computed photon noise. Averaging all LFC exposures, recorded over a few hours, we could obtain a calibration curve with residuals of 2.4 m s −1 . Thanks to the adjustable and optimally chosen line density of the LFC, we resolve a periodicity of 512 pixels in the calibration curve that is due to the manufacturing process of the CCD mask. Previous Th–Ar calibration was unable to resolve these systematic deviations, resulting in a deviation of up to 70 m s −1 from the true calibration curve. In future, we hope to be able to make use of all echelle orders in order to obtain a calibration repeatability below 1 cm s −1 and absolute calibration within a few m s −1 .

Quantitative biomarker assay with microfluidic paper-based analytical devices

Abstract: This article describes the use of microfluidic paper-based analytical devices (μPADs) to perform quantitative chemical assays with internal standards. MicroPADs are well-suited for colorimetric biochemical assays; however, errors can be introduced from the background color of the paper due to batch difference and age, and from color measurement devices. To reduce errors from these sources, a series of standard analyte solutions and the sample solution are assayed on a single device with multiple detection zones simultaneously; an analyte concentration calibration curve can thus be established from the standards. Since the μPAD design allows the colorimetric measurements of the standards and the sample to be conducted simultaneously and under the same condition, errors from the above sources can be minimized. The analytical approach reported in this work shows that μPADs can perform quantitative chemical analysis at very low cost.

Developments in the calibration and modeling of radiocarbon dates

Abstract: Calibration is a core element of radiocarbon dating and is undergoing rapid development on a number of different fronts. This is most obvious in the area of 14C archives suitable for calibration purposes, which are now demonstrating much greater coherence over the earlier age range of the technique. Of particular significance to this end is the development of purely terrestrial archives such as those from the Lake Suigetsu sedimentary profile and Kauri tree rings from New Zealand, in addition to the groundwater records from speleothems. Equally important, however, is the development of statistical tools that can be used with, and help develop, such calibration data. In the context of sedimentary deposition, age-depth modeling provides a very useful way to analyze series of measurements from cores, with or without the presence of additional varve information. New methods are under development, making use of model averaging, that generate more robust age models. In addition, all calibration requires a coherent approach to outliers, for both single samples and where entire data sets might be offset relative to the calibration curve. This paper looks at current developments in these areas.

Integrated Microfluidic Device for Serum Biomarker Quantitation using Either Standard Addition or a Calibration Curve

Abstract: Apparatus and method for determining concentration of one or more target compounds in a sample solution containing one or more nontarget compounds that uses an affinity column to immobilize the target compounds. The target compounds are eluted and passed through a separation/detection system to determine quantitative measure of concentration for each of the target compound.

Bioimaging of metals in thin mouse brain section by laser ablation inductively coupled plasma mass spectrometry: novel online quantification strategy using aqueous standards

Abstract: A novel solution-based calibration method for quantitative spatial resolved distribution analysis (imaging) of elements in thin biological tissue sections by LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry) is described. A dual flow of the carrier and nebulizer gas is used to transport the aerosol of the laser ablated solid sample (brain tissue) and that of the nebulized aqueous standard into inductively coupled plasma (ICP) source, respectively. Both aerosols are introduced separately in the injector tube inside a special ICP torch and then mixed in the inductively coupled plasma. Calibration curves were obtained via two different calibration strategies: (i) solution based calibration and (ii) with a set of well characterized homogeneous brain laboratory standards. In the first approach matrix matching is performed by solution nebulization of a series of aqueous standards with defined analyte concentrations and simultaneous laser ablation of brain homogenate followed by nebulization of 2% (v/v) HNO3 and laser ablation of a whole brain slice (line by line). In the second approach of calibration a set of brain homogenates with defined analyte concentrations is analyzed by LA-ICP-MS followed by the imaging of brain tissue under the same experimental conditions (dry plasma). Calibration curves of elements of interest (e.g., Li, Na, Al, K, Ca, Ti, V, Mn, Ni, Co, Cr, Cu, Zn, As, Se, Rb, Sr, Y, Cd, Ba, La, Ce, Nd, Gd, Hg, Pb, Bi and U) were obtained using (i) aqueous standards or (ii) the set of synthetic laboratory standards prepared from a mouse brain homogenate doped with elements at defined concentrations. The ratio of the slope of the calibration curves (obtained by using aqueous standards and solid standards) was applied to correct the differences of sensitivity among ICP-MS and LA-ICP-MS. Quantitative images of Li, Mn, Fe, Cu, Zn and Rb in mouse brain were obtained under wet plasma condition (nebulization of HNO3 solution in parallel with ablation of solid brain sample).

Determination of trace mercury in environmental samples by cold vapor atomic fluorescence spectrometry after cloud point extraction

Abstract: A sensitive method is presented for the determination of ultra-trace levels of mercury using cold vapor atomic fluorescence spectrometry along with cloud point extraction. Preconcentration is based on the complexation of Hg(II) by dithizone, followed by micelle-mediated extraction of the complex using the surfactant Triton X-114. Foaming, which is always observed when generating vapor mercury in the presence of surfactant, was strongly reduced by using SnCl2 as a reducing reagent, and a homemade gas–liquid separator. Variables that affect the assay were optimized. These included pH value, concentration of chelating reagent, concentration of Triton X-114, equilibration temperature and time. The preconcentration of a 45-mL sample gave an enhancement factor of 29. The calibration graph is linear in the range from 0.05 to 5.0 ng mL−1 with a correlation coefficient of 0.9991. The limit of detection (3δ) obtained under the optimal conditions is 5 pg mL−1. The relative standard deviation for seven replicate determinations at 0.5 ng mL−1 level is 5.2%. The method was successfully applied to the determination of Hg in real samples.

Determination of trace amounts of palladium by flame atomic absorption spectrometry after ligandless-dispersive liquid–liquid microextraction

Abstract: Ligandless dispersive liquid–liquid microextraction (LL-DLLME) was successfully used as a sample preparation method prior flame atomic absorption determination of trace amount of palladium in water and standard samples. In the LL-DLLME method, carbon tetrachloride and ethanol were used as extraction and dispersive solvents, respectively. Several factors that may be affected on the extraction process, such as extraction and disperser solvent, the volume of extraction and disperser solvent, pH of the aqueous solution and extraction time were optimized. Under the optimum conditions, the calibration curve was linear in the range of 15.0 ng mL−1 to 7.0 µg mL−1 of palladium with R2=0.9993 (n = 9) and detection limit was 1.4 ng mL−1 based on 3Sb. The relative standard deviation of eight replicate determination of 2.0 μg mL−1 palladium was ±1.5%. The LL-DLLME method was applied to the separation and preconcentration of trace quantities of palladium prior to its determination in water and standard samples.

Qualitative and Quantitative Analysis of CO2 and CH4 Dissolved in Water and Seawater Using Laser Raman Spectroscopy

Abstract: Laboratory experiments have been performed using laser Raman spectroscopy to analyze carbon dioxide (CO2) and methane (CH4) dissolved in water and seawater. Dissolved CO2 is characterized by bands at ∼1275 and 1382 Δcm−1. Dissolved CH4 is characterized by a dominant band at ∼2911 Δcm−1. The laboratory instrumentation used for this work is equivalent to the sea-going Raman instrument, DORISS (Deep Ocean Raman In Situ Spectrometer). Limits of quantification and calibration curves were determined for each species. The limits of quantification are ∼10 mM for CO2 and ∼4 mM for CH4. A ratio technique is used to obtain quantitative information from Raman spectra: the gas bands are referenced to the O–H stretching band of water. The calibration curves relating band height ratios to gas concentration are linear and valid for a range of temperatures, pressures, and salinities. Current instrumentation is capable of measuring the highest dissolved gas concentration observed in end-member hydrothermal fluids. Further development work is needed to improve sensitivity and optimize operational configurations.

Investigation of reproducibility and error associated with qPCR methods using Quantifiler® Duo DNA quantification kit.

Abstract: Reproducibility of quantitative PCR results is dependent on the generation of consistent calibration curves via accurate volume transfers and instrument performance A review of 14 standard curves, using two different QuantDuo® standard DNA lots, showed variability of cycle threshold values between assays were larger than those of the Internal PCR Control (IPC) This prompted a set of experiments designed to determine the source of variability Results showed that error introduced during DNA addition to the plate resulted in little variation A comparison of seven independent series demonstrated cycle threshold variation between dilutions was larger than the variation expected from repeated samples Modeling the influence of pipette errors on dilution series accuracy indicated that a more rigorous approach to external calibration curve production is required and showed that improvement in calibration curve stability is expected if the pipette conditions are carefully chosen and ⁄ or a single validated curve is utilized as the calibrator

Evaluation of minimal 13C-labelling for stable isotope dilution in organic analysis

Abstract: A procedure for Stable Isotope Dilution Analysis in molecular Mass Spectrometry which does not require a methodological calibration graph and can be applied in combination with minimal labelling has been evaluated. This alternative approach is based on the determination of the molar fractions for each pure isotope pattern (natural abundance or labelled) contributing to the isotope pattern observed in the mixture of natural abundance and labelled molecules by multiple linear regression. Two labelled compounds, 13C1-labelled or 13C6-labelled phenol, were compared to study the influence of the number of 13C atoms in the labelled molecule. The procedure was evaluated by comparing the results obtained for the determination of phenol in NIST 1584 CRM by GC-EI-MS using the classical isotope dilution calibration procedure and the new procedure based on multiple linear regression of isotope patterns without a calibration graph. The results obtained using the proposed procedure agreed well with both the certified values and those obtained using the classical Isotope Dilution Mass Spectrometry (IDMS) calibration procedures. For the evaluated procedure, a full uncertainty budget determination has been developed taking into account all uncertainty sources, including those derived from the uncertainties in the isotope patterns of the natural and labelled compounds. The measurements with the 13C1-labelled phenol provided lower propagated uncertainties in comparison to the use of 13C6-labelled phenol.

Femtosecond laser ablation-ICP-mass spectrometry analysis of a heavy metallic matrix : determination of platinum group metals and gold in lead fire-assay buttons as a case study

Abstract: Owing to the shorter time interval during which energy is delivered to the sample material, femtosecond (fs) laser ablation is preferable over nanosecond laser ablation for metallic samples. In this project, the influence of various laser parameters—beam diameter, repetition rate and laser fluence—on the ablation of Pb as a heavy metallic matrix using an infrared (λ = 795 nm) fs-LA system (150 fs pulse duration) was studied. The merits of Ar and He as carrier gases were compared and as He did not provide a substantial improvement in the limits of detection, while deposition of sample material on the window of the ablation chamber was more pronounced, Ar was selected for all further measurements. The effect on the ICP caused by the introduction of various amounts of sample aerosol was studied by monitoring the signal intensity for 38Ar+. It was shown that maximizing the amount of sample ablated and thus, the amount of sample aerosol introduced into the ICP, did not result in maximum sensitivity, which was rather obtained under ‘compromise’ conditions. Subsequently, femtosecond LA-quadrupole-based ICP-mass spectrometry (ICP-MS) was used for the determination of traces of the platinum group metals (PGMs) Rh, Pd, Ru, Ir and Pt and of Au in Pb buttons obtained by fire assay of platiniferous ore reference materials. The signal of 204Pb+ was used as an internal reference, correcting for variations in the laser ablation and transport efficiencies and in the instrument's sensitivity. The spectral interferences established for some of the target nuclides due to the occurrence of Pb2+ ions were successfully overcome by pressurizing the reaction cell with NH3. Quantification versus a calibration curve constructed on the basis of the results obtained for matrix-matched standards (> 99% Pb) provided excellent accuracy, superior to those obtained using nanosecond LA-ICP-MS. Also the limits of detection were improved by a factor ranging between 3 and 10 and are <0.010 μg g−1 for the most important PGMs (Rh, Pd, Pt) and Au. Several measures, such as the use of a large ablation cell and housing up to 10 Pb buttons, were taken to increase the sample throughput. In the same context, day-to-day reproducibility of the calibration curve was also examined. When recording a ‘fresh’ calibration curve every day, the average bias between the experimental results and the corresponding reference values was established to be <2.5% for every target element. When using one calibration curve during three consecutive days, the bias still remains <10%, while the sample throughput is increased and analysis of several tens of buttons per day is feasible (10–15 min total analysis time per sample).

A Wide-Range Particle Spectrometer for Aerosol Measurement from 0.010 µm to 10 µm

Abstract: The Wide-range Particle Spectrometer (WPS™) is a recently introduced commercial instrument with the unique capability to measure size distributions of aerosols from 0.01 to 10 µm in diameter. The instrument includes a Scanning Mobility Spectrometer (SMS) comprised of a Differential Mobility Analyzer (DMA) and a Condensation Particle Counter (CPC) for particle measurement from 0.01 to 0.5 µm and a Laser Particle Spectrometer (LPS) for measurement in the ~0.4 to 10 µm range. These components are small enough to fit into a small portable cabinet (~26 kg) with all accompanying control hardware and electronics. No external pumps are required and power consumption is only about 150 W. The DMA is calibrated with Standard Reference Materials (SRM) from the U.S. National Institute of Standards and Technology (NIST), including SRM 1691 and SRM 1963a. These are uniform size polystyrene latex (PSL) spheres available from NIST with mean diameters of 0.269 µm and 0.1018 µm respectively. The CPC has a dual reservoir design to prevent the working fluid from being contaminated by water due to moisture condensation in the condenser. The LPS is calibrated with four NIST-traceable PSL sphere sizes. Calibration curves are generated not only for PSL (real refractive index of 1.585), but also for discrete values real refractive index ranging from 1.30 to 1.60. This procedure allows the user to select the most appropriate curve for determination of the light-scattering-equivalent sphere size that takes into account the effect due to refractive index of real aerosols. The LPS has a wide-angle collection optics design to produce a monotonic response curve for routine measurement in the field.

Application of HPLC and HPTLC for the simultaneous determination of cefixime trihydrate and ambroxol hydrochloride in pharmaceutical dosage form

Abstract: Two sensitive and reproducible methods are described for the quantitative determination for the simultaneous estimation of cefixime trihydrate and ambroxol hydrochloride. The first method was based on HPTLC followed by densitometric measurements of their spots at 254 nm. The separation was on HPTLC aluminium sheets of silica gel 60 F254 using acetonitrile: methanol: triethylamine (8.2:1:0.8, v/v/v) as mobile phase. The linear regression analysis was used for the regression line in the range of 200 - 1000 ng spot -1 for cefixime and ambroxol, respectively. This system was found to give compact spots for cefixime and ambroxol, after development. The second method was based on HPLC separation of the two drugs on the column [C18 (5 µ, 25 cm×4.6 mm, i.d.)] at ambient temperature using a mobile phase consisting of acetonitrile: methanol (50:50, v/v). Quantitation was achieved with UV detection at 254 nm based on peak area with linear calibration curves at concentration ranges 4 18 and 4 - 28 μg mL -1 for cefixime and ambroxol, respectively. Both methods have been successively