Concentration Of Analyte In Sample Research Articles

Improving diagnostic performance of coronavirus disease 2019 rapid antigen testing through computer-based feedback training using open-source experimental psychology software

IntroductionRapid antigen testing (RAT) results are visually read as whether colored line is present or absent. The subjective interpretation potentially misses detecting weak lines due to lower analyte concentration in samples tested, requiring training. Although routine test experience has improved the result readout skills, it consumes time and resources. Therefore, we created a computer-based feedback training method using open-source experimental psychology software, wherein participants accumulate RAT result readout experience by repeatedly responding positive/negative to randomly presented pictures showing RAT results; then, they receive feedback on their answers as correct or incorrect and are asked to stare at the pictures again with the knowledge of correct answer. This study aimed to examine the training effects in improving the skills, using coronavirus disease 2019 (COVID-19) RAT. MethodsTwenty-two medical technologists were randomly divided into two groups: the feedback-training and test-experience groups. Using several pictures showing positive and negative results of COVID-19 RAT, after examination of their initial result readout skills, feedback-training group received the feedback training, whereas test-experience group performed an equal number of tests without feedback to accumulate test experience, and their skills were examined again. The ratio of “positive” answers to the pictures showing positive results (i.e., hit rate) was statistically analyzed. ResultsThe feedback-training group showed a significantly higher hit rate after their training, whereas the test-experience group did not. The feedback training effects were manifested in weak line detection. ConclusionsThis computer-based feedback training method can be an effective tool for improving RAT result readout skills.

A smartphone based photothermal-colorimetric immunochromatographic sensor for ultrasensitive and ultra-wide concentration range detection of deoxynivalenol

Immunochromatographic sensor (ICS) is one of the first choices for on-site detection of deoxynivalenol (DON), a common mycotoxin that contaminate food. However, it suffers from unsatisfactory sensitivity and narrow quantitative range. Herein, a photothermal-colorimetric dual mode ICS was established for visually fast screening or accurately quantifying DON. Black phosphorus-gold (BP-Au) nanocomposite with remarkable color and photothermal conversion efficiency up to 46.41% under 808 nm laser irradiation was developed as the dual mode signal probe instead of Au nanoparticles in traditional ICS. Both the photothermal and colorimetric signals could be collected by a smartphone with a commercial IR imaging adapter. The as-prepared BP-Au showed a great thermal contrast amplification (TCA) effect, exhibiting ultra-sensitive response to its amount arrested on test zone of ICS, which is correlated with the concentration of analyte in samples. The developed ICS for DON gave an ultra-sensitive LOD of 0.154 pg mL−1 and an ultra-wide quantitative range of 1–106 pg mL−1 in photothermal mode, which was much more improved than that in colorimetric mode or reported in literatures. It demonstrated good selectivity toward DON over other mycotoxins and recoveries of 95.38%–116.75% in diluted grain extracts. This ICS enables dynamic monitoring tiny variation of food contaminants in time and accurate assessment of the degree they exceeding limitation standards.

Research progress on the application of derived porous carbon materials in solid-phase microextraction

固相微萃取是一种集采样、萃取、富集和进样于一体的样品前处理技术,其萃取效果与涂层材料密切相关。多孔碳材料具有比表面积大、多孔结构可控、活性位点多和化学稳定性好等优点,广泛应用于电池、超级电容器、催化、吸附和分离等领域,也是一种热门的用作固相微萃取探针的涂层材料。衍生多孔碳材料因种类丰富、可设计性强被广泛研究,研究主要集中在对衍生多孔碳材料的结构优化方面。但是衍生多孔碳材料在固相微萃取中的应用还存在如下问题:(1)共价有机框架衍生多孔碳材料的制备已取得较大进展,但将其应用于固相微萃取领域的研究仍较少;(2)有待进一步明确制备出的衍生多孔碳材料用作固相微萃取涂层表现出优异提取能力的机理;(3)有待进一步深入研究将衍生多孔碳材料用作固相微萃取涂层以实现对不同物理化学性质污染物的广谱高灵敏度分析。文章综述了近3年衍生多孔碳材料在固相微萃取中的应用研究,并展望了未来衍生多孔碳材料在固相微萃取中的研究前景。引用文献共56篇,主要来源于Elsevier。

Analysis of Electric Field Distribution for SOI-FET Sensors with Dielectrophoretic Control.

Silicon-on-insulator (SOI) nanowire or nanoribbon field-effect transistor (FET) biosensors are versatile platforms of electronic detectors for the real-time, label-free, and highly sensitive detection of a wide range of bioparticles. At a low analyte concentration in samples, the target particle diffusion transport to sensor elements is one of the main limitations in their detection. The dielectrophoretic (DEP) manipulation of bioparticles is one of the most successful techniques to overcome this limitation. In this study, TCAD modeling was used to analyze the distribution of the gradient of the electric fields E for the SOI-FET sensors with embedded DEP electrodes to optimize the conditions of the dielectrophoretic delivery of the analyte. Cases with asymmetrical and symmetrical rectangular electrodes with different heights, widths, and distances to the sensor, and with different sensor operation modes were considered. The results showed that the grad E2 factor, which determines the DEP force and affects the bioparticle movement, strongly depended on the position of the DEP electrodes and the sensor operation point. The sensor operation point allows one to change the bioparticle movement direction and, as a result, change the efficiency of the delivery of the target particles to the sensor.

Boundary values of binding constants determined by affinity capillary electrophoresis.

This study shows that the upper limit of binding (stability) constants determined by mobility shift affinity capillary electrophoresis can be increased from 104 to 106 -109 L/mol if the lowest possible analyte concentration in samples is used (for example, the concentration that gives electrophoretic peaks with a signal-to-noise ratio of 10) and the effective electrophoretic mobility of the analyte is calculated via the parameter a1 of the Haarhoff-Van der Linde function. The equation to calculate the boundary values of binding constants for 1:1 complexes was derived for the case when the constants cannot be calculated in the usual way. These values are obtained from the inequality: the difference between the ionic mobility of the analyte-ligand complex and the effective electrophoretic mobility of the analyte determined at the lowest ligand concentration in the background electrolyte at which the analyte appears as an undistorted peak in electropherograms is less than or equal to the absolute error in mobility measurements. The application of the equation was illustrated by the example of electrophoretic data for a complex between betulin 3,28-diphthalate and (2-hydroxypropyl)-γ-cyclodextrin. An algorithm to determine the binding constants for strong complexation by mobility shift affinity capillary electrophoresis was suggested.

Colorimetric determination of L-cysteine in milk samples with surface functionalized silver nanoparticles

A simple, selective and sensitive method is proposed for determination of cysteine (Cys) in milk samples using ionic liquid functionalized silver nanoparticles (ILs-AgNPs) as a colorimetric probe. ILs-AgNPs was synthesized by simple reduction method using silver nitrate as a precursor and sodium borohydride as a reducing agent and functionalized with ILs to prevent particles from self-aggregation. The sensing mechanism has been dependent on the color change of ILs-AgNPs and red shift of absorption band from 395nm to 560nm in the visible region, which is found proportional to the concentration of target analyte in sample. ILs-AgNPs was characterized in absence and presence of Cys by UV-vis, Fourier transform-infrared (FTIR) spectroscopy, transmission electron microscope (TEM) and dynamic light scattering (DLS). The linear range was acquired in the range of 0-100ngmL-1, with correlation coefficient (R2) of 0.996 and limit of detection (LOD) of 4.0nM. The binding mechanism and interactions between Cys and ILs-AgNPs was confirmed by calculating the binding constant and thermodynamic parameters such as enthalpy (∆H), entropy (∆S) and Gibb's free energy (∆G). The use of ILs-AgNPs exhibited high colorimetric selectivity for Cys in milk samples in presence of other amino acids. This proposed strategy possessed the advantages of simplicity and selectivity, hence is applied for analysis of Cys in milk samples.

A rapid, simple high performance liquid chromatography method for the determination of traditional Chinese medicine ointment Shiunko

A rapid, simple and sensitive reversed-phase HPLC method with Ultraviolet (UV) absorbance measurement at 280 nm was applied for the simultaneous quantitative determination of marker substances in the traditional Chinese herbal ointment Shiunko. Shiunko consists of Lithospermum radix containing shikonin, acetylshikonin, β,β-dimethylacrylshikonin, isobutylshikonin, deoxyshikonin, and isovalerylshikonin, as well as Angelica radix containing ferulic acid. Specimens of Shiunko ointment were extracted with acetonitrile, separated on a reversed-phase C18 (ThermoQuest, 250 × 4.6 mm i.d.) column at ambient temperature, with a solvent system consisting of 47% acetonitrile and 53% acetic acid (v/v, pH 2.56) at a flow rate of 1.0 mL/min. Diclofenac was used as the internal standard. This procedure enabled a run time of within 35 min. In the validation of this analytical method, the RSD and RE were less than 7.0%, indicating satisfactory accuracy and repeatability. The linear relationships between the concentration of analyte in samples within a given range (ferulic acid 0.175- 3.50 μg/mL, shikonin 0.5-10.0 μg/mL, acetylshikonin 0.5-10 μg/mL, β,β-dimethylacrylshikonin 0.35-7 μg/mL, isobutylshikonin 0.4-0.8 μg/mL, deoxyshikonin 0.255-5.1 μg/mL, and isovalerylshikonin 0.25-5 μg/mL) and the corresponding peak area ratio were good indications that this analytical method could be used in quantitative analysis. The lower limit of detection of these marker substances under above conditions was 0.05 μg/mL.

Analysis of the Binding of Analyte-Receptor in a Micro-Fluidic Channel for a Biosensor Based on Brownian Motion

This study experimentally analyses the binding characteristics of analytes mixed in liquid samples flowing along a micro-channel to the receptor fixed on the wall of the micro-channel to provide design tools and data for a microfluidic-based biosensor. The binding or detection characteristics are analyzed experimentally by counting the number of analytes bound to the receptor, with sample analyte concentration, sample flow rate, and the position of the receptor along the micro-channel length as the main variables. A mathematical model is also proposed to predict the number of analytes transported and bound to the receptor based on a probability density function for Brownian motion. The coefficient in the mathematical model is obtained by using a dimensionless mathematical model and the experimental results. The coefficient remains valid for all different conditions of the sample analyte concentration, flow rate, and the position of the receptor, which implies the possibility of deriving a generalized model. Based on the mathematical model derived from mathematical and experimental analysis on the detection characteristics of the microfluidic-based biosensor depending on previously mentioned variables and the height of the micro-channel, this study suggests a design for a microfluidic-based biosensor by predicting the binding efficiency according to the channel height. The results show the binding efficiency increases as the flow rate decreases and as the receptor is placed closer to the sample-injecting inlet, but is unaffected by sample concentration.

Enzymatic Bioelectrocatalysis for Enzymology Applications

AbstractEnzymatic biosensors are commonly used to evaluate the concentration of individual analytes in samples (e. g., glucose in blood, lactate in sweat, etc.), where the working electrode utilizes an enzyme (a “bioelectrode”) as the chemically selective agent for electrochemical analyses. However, those same enzymatic bioelectrodes can be used for the analytical characterization of enzymes as a new biophysical characterization tool for enzymologists. This Minireview will detail recent work focused on utilizing enzymatic bioelectrocataysis for enzymology applications. Specifically, it will talk about the use of enzymatic bioelectrodes for studying kinetics, inhibition, transport, and thermodynamics. It will also compare and contrast electrochemical techniques with spectrophotometric techniques for enzymology.

A Metal Chelator as a Plasmonic Signal-Generation Superregulator for Ultrasensitive Colorimetric Bioassays of Disease Biomarkers.

Enzyme‐based assays have been widely applied in clinical diagnosis for decades. However, the intrinsic limitations of enzymes, such as low operation stability, mediocre sensitivity, and high cost in production and purification, heavily constrain their detection application. Here, an enzyme‐free assay is reported that relies on the strong chelating capability of ethylenediamine tetraacetic acid disodium salt (EDTA•2Na, the chelator) for Au3+ ions, in which the cheap EDTA•2Na labeled by targeting moieties can selectively regulate the growth of plasmonic gold nanoparticles (AuNPs) at the target site subjecting to the concentration of analyte in samples. Independent of ambient temperature and unstable H2O2, EDTA•2Na perform superregulation in AuNPs plasmonic signal generation with distinct tonality and outstanding reliability. Upon integrating with silica nanoparticles as the signal amplifying platform, EDTA•2Na‐regulated bioassay can lead to detection‐sensitivity enhancements exceeding three orders of magnitude in protein detection, compared with the gold‐standard assay. The limit of detection of the HBsAg and alpha fetoprotein (AFP) pushes down to 2.6 × 10−15 and 2.5 × 10−19 g mL−1, respectively. EDTA•2Na‐regulated bioassay is also challenged in the clinical serum sample detection and a good consistency is found with the chemiluminescence immunoassay method in clinics.

A new imaged-based quantitative reader for the gold immunochromatographic assay

Gold immunochromatographic assay (GICA) is widely used for quantitative measuring the concentration of the target analyte in samples. In this paper, a new low-cost quantitative reader is developed for the GICA based on the image processing technology. The image of the GICA strip is captured by the established quantitative reader, which is mainly composed by the microcontroller, image-senor and light source. Then, an automatic image processing framework, which includes image de-noising, extraction of the detection region, test and control lines segmentation and feature calculation, is carried out in the STM32F407ZGT6 microcontroller. Especially, the fuzzy cellular neural network with adaptive threshold (FCNN-AT) algorithm is presented in this paper for segmenting the test and control lines with high accuracy. Several indices are proposed to evaluate the proposed method. Results demonstrate that the presented quantitative reader based on the FCNN-AT algorithm is an effective and practical method for quantitative analysis of GICA.

HIGH PERFORMANCE LIQUID CHROMATOGRAPHY METHOD VALIDATION OF α-MANGOSTIN ASSAY IN MANGOSTEEN (Garcinia mangostana L.) FRUIT RIND EXTRACT FORMULATED IN ORAL SOLUTION

<p>Mangosteen fruit rind extract contain a lot of antioxidants. α-Mangostin is a component in mangosteen fruit rind that has highest antioxidant effect. The oral solution containing mangosteen fruit rind extract is required an assay method for quality assessment. Determination of a very low concentration of analyte in sample with very complex matrix, such as α-mangostin in oral solution, needs a selective and sensitive method, such as high performance liquid chromatography (HPLC). In this study, α-mangostin assay was performed by reverse phase HPLC system using octadecylsilane (C18) as stationary phase, methanol-water (90:10) as mobile phase, the flow rate is 1.0 mL/min, and the UV detector at 316 nm. The retention time of α-mangostin was 9.622 minutes. Peak of α-mangostin was well separated with resolution of 1.725. Linearity was in the range of 1.67-5.01 ppm with correlation coefficient of 0.9986. The relative standard deviation (RSD) was 1.30 %, the recovery was in the range of 95.80-100.76 </p>

Sensing Technology for Rapid Detection of Phosphorus in Water: A Review

Purpose: Phosphorus is an essential element for water quality control. Excessive amounts of phosphorus causes algal bloom in water, which leads to eutrophication and a decline in water quality. It is necessary to maintain the optimum amount of phosphorus present. During the last decades, various studies have been conducted to determine phosphorus content in water. In this study, we present a comprehensive overview of colorimetric, electrochemical, fluorescence, microfluidic, and remote sensing technologies for the measurement of phosphorus in water, along with their working principles and limitations. Results: The colorimetric techniques determine the concentration of phosphorus through the use of colorgenerating reagents. This is specific to a single chemical species and inexpensive to use. The electrochemical techniques operate by using a reaction of the analyte of interest to generate an electrical signal that is proportional to the sample analyte concentration. They show a good linear output, good repeatability, and a high detection capacity. The fluorescence technique is a kind of spectroscopic analysis method. The particles in the sample are excited by irradiation at a specific wavelength, emitting radiation of a different wavelength. It is possible to use this for quantitative and qualitative analysis of the target analyte. The microfluidic techniques incorporate several features to control chemical reactions in a micro device of low sample volume and reagent consumption. They are cheap and rapid methods for the detection of phosphorus in water. The remote sensing technique analyzes the sample for the target analyte using an optical technique, but without direct contact. It can cover a wider area than the other techniques mentioned in this review. Conclusion: It is concluded that the sensing technologies reviewed in this study are promising for rapid detection of phosphorus in water. The measurement range and sensitivity of the sensors have been greatly improved recently.

HIGH PERFORMANCE LIQUID CHROMATOGRAPHY METHOD VALIDATION OF α-MANGOSTIN ASSAY IN MANGOSTEEN (Garcinia mangostana L.) FRUIT RIND EXTRACT FORMULATED IN ORAL SOLUTION

<p>Mangosteen fruit rind extract contain a lot of antioxidants. α-Mangostin is a component in mangosteen fruit rind that has highest antioxidant effect. The oral solution containing mangosteen fruit rind extract is required an assay method for quality assessment. Determination of a very low concentration of analyte in sample with very complex matrix, such as α-mangostin in oral solution, needs a selective and sensitive method, such as high performance liquid chromatography (HPLC). In this study, α-mangostin assay was performed by reverse phase HPLC system using octadecylsilane (C18) as stationary phase, methanol-water (90:10) as mobile phase, the flow rate is 1.0 mL/min, and the UV detector at 316 nm. The retention time of α-mangostin was 9.622 minutes. Peak of α-mangostin was well separated with resolution of 1.725. Linearity was in the range of 1.67-5.01 ppm with correlation coefficient of 0.9986. The relative standard deviation (RSD) was 1.30 %, the recovery was in the range of 95.80-100.76 </p>

Dose–response curve of a microfluidic magnetic bead-based surface coverage sandwich assay

Magnetic micro- and nanoparticles ('magnetic beads') have been used to advantage in many microfluidic devices for sensitive antigen (Ag) detection. Today, assays that use as read-out of the signal the number count of immobilized beads on a surface for quantification of a sample's analyte concentration have been among the most sensitive and have allowed protein detection lower than the fgmL(-1) concentration range. Recently, we have proposed in this category a magnetic bead surface coverage assay (Tekin et al., 2013 [1]), in which 'large' (2.8μm) antibody (Ab)-functionalized magnetic beads captured their Ag from a serum and these Ag-carrying beads were subsequently exposed to a surface pattern of fixed 'small' (1.0μm) Ab-coated magnetic beads. When the system was exposed to a magnetic induction field, the magnet dipole attractive interactions between the two bead types were used as a handle to approach both bead surfaces and assist with Ag-Ab immunocomplex formation, while unspecific binding (in absence of an Ag) of a large bead was reduced by exploiting viscous drag flow. The dose-response curve of this type of assay had two remarkable features: (i) its ability to detect an output signal (i.e. bead number count) for very low Ag concentrations, and (ii) an output signal of the assay that was non-linear with respect to Ag concentration. We explain here the observed dose-response curves and show that the type of interactions and the concept of our assay are in favour of detecting the lowest analyte concentrations (where typically either zero or one Ag is carried per large bead), while higher concentrations are less efficiently detected. We propose a random walk process for the Ag-carrying bead over the magnetic landscape of small beads and this model description explains the enhanced overall capture probability of this assay and its particular non-linear dose response curves.

A miniaturized analyzer for the catalytic determination of iodide in seawater and pharmaceutical samples

A monolithic flow conduit was especially designed and coupled to a multisyringe unit (MSFIA) in order to develop a kinetic analytical method. The new device, denoted CHIP, integrates different functions in a reduced size including confluent mixing, reaction coil, and thermostating, which allowed minimizing the dimensions of the entire analyzer system. The CHIP–MSFIA was satisfactorily applied to the determination of iodide using the Sandell–Kolthoff reaction. The resulting system allows fast, simple and automatic analysis in seawater samples and a pharmaceutical preparation. By the use of an additional syringe, reagent blank, sample blank, unspecific interferences, and sample analyte concentration was evaluated by simply changing the mode of operation. The instrumentation and analytical procedures were optimized in respect of sensitivity. A limit of detection of 4.7μgL−1 and linear working range of 4.3–70μgL−1 were achieved.Two new modes of air bubble elimination were developed and employed in this work, leading to improved reproducibility (RSD %=1.5%) and method robustness. The accuracy of analysis for seawater samples was evaluated by an Add–Recovery test obtaining recoveries between 97 and 106%. For the quantification of iodide in the pharmaceutical sample, standard addition calibration was required. No significant differences between the found and the certified value were found. The entire analytical procedure lasted about 150s enabling a measuring frequency of 23h−1.

Sodium dodecyl sulfate coated γ-alumina support modified by a new Schiff base for solid phase extraction and flame-AAS determination of lead and copper ions

A simple and fast approach for solid phase extraction is herein described, and used to determine trace amounts of Pb2+ and Cu2+ metal ions. The solid phase support is sodium dodecyl sulfate (SDS)-coated γ-alumina modified with bis(2-hydroxy acetophenone)-1,6-hexanediimine (BHAH) ligand. The adsorbed ions were stripped from the solid phase by 6 mL of 4 M nitric acid as eluent. The eluting solution was analyzed by flame atomic absorption spectrometry (FAAS). The sorption recovery of metal ions was investigated with regard to the effects of pH, amount of ligand, γ-alumina and surfactant and the amount and type of eluent. Complexation of BHAH with Pb2+ or Cu2+ ions was examined via spectrophotometry using the HypSpec program. The detection limit for Cu2+ was 7.9 µg L-1 with a relative standard deviation of 1.67%, while that for Pb2+ was 6.4 µg L-1 with a relative standard deviation of 1.64%. A preconcentration factor of 100 was achieved for these ions. The method was successfully applied to determine analyte concentrations in samples of liver, parsley, cabbage, and water.

HDL3, but not HDL2, stimulates plasminogen activator inhibitor-1 release from adipocytes: the role of sphingosine-1-phosphate

Sphingosine-1-phosphate (S1P) is a bioactive lysophospholipid that regulates numerous key cardiovascular functions. High-density lipoproteins (HDLs) are the major plasma lipoprotein carriers of S1P. Fibrinolysis is a physiological process that allows fibrin clot dissolution, and decreased fibrinolytic capacity may result from increased circulating levels of plasminogen activator inhibitor-1 (PAI-1). We examined the effect of S1P associated with HDL subfractions on PAI-1 secretion from 3T3 adipocytes. S1P concentration in HDL3 averaged twice that in HDL2. Incubation of adipocytes with increasing concentrations of S1P in HDL3, but not HDL2, or with S1P complexed to albumin stimulated PAI-I secretion in a concentration-dependent manner. Quantitative RT-PCR revealed that S1P(1-3) are expressed in 3T3 adipocytes, with S1P(2) expressed in the greatest amount. Treatment of adipocytes with the S1P(1) and S1P(3) antagonist VPC23019 did not block PAI-1 secretion. Inhibiting S1P(2) with JTE-013 or reducing the expression of the gene coding for S1P(2) using silencing RNA (siRNA) technology blocked PAI-1 secretion, suggesting that the S1P(2) receptor mediates PAI-1 secretion from adipocytes exposed to HDL3 or S1P. Treatment with the phospholipase C (PLC) inhibitor U73122, the protein kinase C (PKC) inhibitor RO-318425, or the Rho-associated protein kinase (ROCK) inhibitor Y27632 all significantly inhibited HDL3- and S1P-mediated PAI-1 release, suggesting that HDL3- and/or S1P-stimulated PAI-1 secretion from 3T3 cells is mediated by activation of multiple, downstream signaling pathways of S1P(2).

Profiling oestrogens and testosterone in human urine by stable isotope dilution/benchtop gas chromatography–mass spectrometry

Oestrogens, such as oestrone (E 1), 17β-oestradiol (E 2), oestriol (E 3) and their biologically active metabolites 2-methoxyoestrone (2-MeOE 1), 2-hydroxyoestradiol (2-OHE 2) 16-ketooestradiol (16-OE 2), 16-epioestriol (16-epiE 3), as well as testosterone (T) play an important role in physiological and pathological developmental processes during human development. We therefore aimed at developing an isotope dilution/bench top gas chromatography–mass spectrometry (ID/GC–MS) method, based on benchtop GC–MS, for the simultaneous determination (‘profiling’) of the above analytes in children. The method consisted of equilibration of urine (5 ml) with a cocktail containing stable isotope-labelled analogues of the analytes as internal standards ([2,4- 2H 2]E 1, [2,4,16,16- 2H 4]E 2, [2,4,17- 2H 3]E 3, [16,16,17- 2H 3]T, [1,4,16,16- 2H 4]2-MeOE 1, [1,4,16,16,17- 2H 5]2-OHE 2, [2,4,15,15,17- 2H 5]16-OE 2 and [2,4- 2H 2]16-epiE 3). Then, solid-phase extraction (C 18 cartridges), enzymatic hydrolysis (sulphatase from Helix pomatia (type H-1)), re-extraction, purification by anion exchange chromatography and derivatisation to trimethylsilyl ethers followed. The samples were analysed by GC–MS (Agilent GC 6890N/5975MSD; fused silica capillary column 25 m × 0.2 mm i.d., film 0.10 μm). Calibration plots were linear and showed excellent reproducibility with coefficients of determination ( r 2) between 0.999 and 1.000. Intra- and inter-assay coefficients of variation (CV) were <2.21% for all quantified metabolites. Sensitivity was highest for 2-OHE 2 (0.25 pg per absolute injection: signal-to-noise ratio (S/N) = 3) and lowest for 16-epiE 3 (2 pg per absolute injection: S/N = 2.6), translating into corresponding urine sample analyte concentrations of 0.025 ng ml −1 and 0.2 ng ml −1, respectively. Accuracy – determined in a two-level spike experiment – showed relative errors ranging between 0.15% for 16-OE 2 and 11.63% for 2-OHE 2. Chromatography showed clear peak shapes for the components analysed. In summary, we describe a practical, sensitive and specific ID/GC–MS assay capable of profiling the above-mentioned steroids in human urine from childhood onwards.

A Disposable Multianalyte Electrochemical Immunosensor Array for Automated Simultaneous Determination of Tumor Markers

Automated and convenient multianalyte detection with high throughput is increasingly needed in clinical diagnosis. We developed a disposable 4-by-2 array for programmed simultaneous amperometric immunoassay of 4 tumor markers. We used a screen-printed technique, 1-step immobilization method, and flow injection technique. We immobilized carcinoembryonic antigen, alpha-fetoprotein, beta-human choriogonadotropin, and carcinoma antigen 125 as model analytes in a redox mediator-grafted, biopolymer-modified, screen-printed carbon electrode array to capture corresponding horseradish peroxidase-labeled antibodies in competitive immunoreactions. The simultaneous multianalyte immunoassay was automatically carried out to amperometrically monitor the mediator-catalyzed enzymatic response to hydrogen peroxide, which decreased in proportion to the concentrations of analytes in samples. The multianalyte immunosensor array had a throughput of 60 samples/h and allowed simultaneous detection of carcinoembryonic antigen, alpha-fetoprotein, beta-human choriogonadotropin, and carcinoma antigen 125 in clinical serum samples with concentrations up to 188 microg/L, 250 microg/L, 266 IU/L, and 334 kIU/L, respectively. The detection limits (limits of the blank, mean of blank plus 3 SD) were 1.1 micro/L, 1.7 microg/L, 1.2 IU/L, and 1.7 kIU/L. The inter- and intraassay imprecision (CVs) of the immunosensor arrays were <7.8% and <9.0%, respectively. The immunosensor arrays were stable for 28 days. This newly constructed immunosensor array provides a simple, automated, simultaneous multianalyte immunoassay with high throughput, short analytical time, and sufficiently low detection limits for clinical application. This method offers the capability of miniaturizing the multianalyte detection device.