Linear Calibration Curves Research Articles

Development of a sensitive and selective bioanalytical method of chebulinic acid by liquid chromatography‐electrospray tandem mass spectrometry and its pharmacokinetic application

AbstractChebulinic acid (CA), a polyphenolic compound extracted from the fruits of Terminalia chebula, has been recently reported as a novel neuraminidase inhibitor against the influenza A virus and also for various biological activities that require pharmacokinetic estimation. We report a proposed fragmentation pathway for the formation and selection of sodium and ammonium adducts using molecular thermodynamics. The chebulinic acid ammonium adduct was reproducible and stable compared to the earlier reported sodium adduct to quantify chebulinic acid by liquid chromatography‐tandem mass spectrometry. Chebulinic acid was extracted from plasma by protein precipitation followed by single‐step liquid‐liquid extraction by removing interfering metal adducts such as sodium. chebulinic acid resolution was achieved from the C18 column with mobile phase acetonitrile: methanol mixture and ammonium acetate buffer at a flow rate of 0.5 ml/min. The linear calibration curve (r2 ≥ 0.995) range was 3.52–1800 ng/ml. Finally, we report the oral pharmacokinetic profile of chebulinic acid in male Swiss albino mice plasma using the developed method.

Quantitation and speciation of inorganic arsenic in a biological sample by capillary ion chromatography combined with inductively coupled plasma mass spectrometry

The toxicity and biological activity of arsenic depend on its chemical form. In particular, inorganic arsenics are more toxic than organic ones. Apart from the determination of total arsenics, their accurate speciation is important for toxicity assessment. To separate arsenic species using a cation or an anion separation column, at least 0.5–1.0 mL of sample is required because conventional ion chromatography columns use a sample loop of 100–200 μL. It is thus difficult to analyze samples with small volumes, such as clinical and biological samples. In this study, a method for separating arsenic species using a 5-μL sample loop combined with a capillary ion exchange column has been developed for analyzing small volume of samples. The separated arsenics were determined by inductively coupled plasma mass spectrometry. By oxidizing As(III) to As(V) prior to analysis, the total inorganic arsenics, As(III) and As(V), could be well separated from the organic ones. Linear calibration curves (0.5–50 μg/kg) were obtained for total inorganic arsenics dissolved in water. Sub-picogram-level detection limit was obtained. The analytical capability of this method was successfully validated for certified reference materials, namely water and human urine, with total inorganic arsenic recovery efficiencies of 100% and 121%, respectively. Our method requires less than ~ 10 μL of sample and will be very useful to analyze valuable samples available in limited amounts.

Fast chromatography of pulse triacylglycerols

AbstractA short 10‐min ultra high performance liquid chromatography (UHPLC) method was used for separation and lipidomic analysis of triacylglycerols (TAGs) in 10 pulses: baby lima beans, black beans, black‐eyed peas, butter beans, cranberry beans, garbanzo beans, green split peas, lentils, navy beans, and pinto beans. The lipids extracted using chloroform/methanol averaged 1.9–2.7% across all pulses except garbanzo beans, which gave 6.2% lipids. TAGs were analyzed using dual parallel mass spectrometry (LC1MS2), areas were integrated using LipidSearch 4.2 software, and percent relative TAG compositions were calculated. Fatty acid response factors were calculated by comparison to calibrated GC‐FID, which were used to calculate response‐factor adjusted TAG compositions. Principal component analysis revealed that the pulses separated into three clusters, which were further highlighted using hierarchical cluster analysis. A subset of TAGs was quantified using calibration curves made from alternating sets of regioisomers in the non‐linear high concentration range (~2.5 nMol/ml to ~300 nMol/ml). A linear calibration curve for the sum of tocopherols detected by fluorescence was constructed with a coefficient of determination, r2, >0.99 for low concentrations (0.50–50 μg/ml), but tocopherols in pulses appeared to be inefficiently extracted. TAG regioisomers were quantified based on a Critical Ratio (CR), [AA]+/[AB]+, interpolated between the CRs of two pure regioisomer standards taken from alternating calibration standards. TAG mole percent relative compositions are reported for the first time for most pulses and the compositions are given with more detail and specificity than previously reported.

Oxygen sensing performance improvement by the combination of narrowed electrospinning fibers and multi-cored phosphorescent photosensitizer: Strategy and performance comparison

Electrospinning fibers doped with phosphorescent Cu(I) complexes have been demonstrated as promising O2 sensing systems, but traditional oxygen sensing systems based on electrospinning fibers have low sensitivity (<10). In this work, three multi-cored phosphorescent Cu(I) probes were firstly synthesized and discussed via their single crystals and photophysical analysis. A long-lived lifetime of 7.9 μs with emission peaking at 441 nm and quantum yield of 0.45 was obtained. Time-dependent density functional theory (DFT) calculation was performed at RB3LYP/LANL2DZ level which revealed a metal-to-ligand-charge-transfer-based electronic transition in excited state, favoring oxygen sensing. Then narrowed electrospinning fibers (diameter<200 nm) were synthesized using a high-pressure pump. The Cu(I) probes were doped into these narrowed electrospinning fibers with three doping levels (5wt%, 10wt%, and 15wt%), so that sample specific surface area was increased to allow more collision chances with O2 molecules. A detailed comparison between normal fibers and narrowed fibers was performed. Our optimal sample showed sensitivity of 20.99 with a linear working equation of I0/I=0.656+0.198*[O2], R2=0.999. This value is by far the highest one among oxygen sensors based on phosphorescent Cu(I) complexes. The limit of detection was as low as 2.2% (O2%). Corresponding response and recovery time values were 7 and 20 seconds. It was found that using narrowed fibers as host was an effective way to improve oxygen sensing performance, showing higher sensitivity, linear calibration curve and faster response behavior.

Voltammetric determination of Molnupiravir used in treatment of the COVID-19 at magnetite nanoparticle modified carbon paste electrode

To reduce the progression of the viral process in patients infected with COVID-19, new treatments and drug active substances are needed. One of these drugs is Molnupiravir (MNP) which has a direct antiviral effect and has also proven to be highly effective in reducing the azopharyngeal SARS-CoV-2 infectious virus and viral RNA. Due to the importance and frequent use of this drug in the treatment of COVID-19, its accurate, quick, and cheap detection in pharmaceutical or biological samples is crucial. In this work, electrochemical behavior and sensitive voltammetric determination of MNP are described using a magnetite nanoparticle modified carbon paste electrode (Fe3O4@CPE) for the first time. Fe3O4 nanoparticles (NPs) were characterized by recording their transmission electron microscopy (TEM) images, energy dispersive X-ray (EDX), and X-ray diffraction (XRD) spectra. Cyclic voltammetric measurements showed that MNP was irreversibly oxidized at Fe3O4@CPE at 760 mV in pH 2.0 Britton Robinson buffer solution (BRBS). The peak current of MNP was increased approximately threefold at Fe3O4@CPE compared to bare CPE due to a good electrocatalytic efficiency of Fe3O4 NPs. According to differential pulse voltammetric studies, the fabricated electrode exhibited a linear range (LR) between 0.25 and 750 µM with sensitivity and limit of detection (LOD) of 4591.0 µA mM−1 cm−2 and 0.05 µM, respectively. On the other hand, although lower sensitivity (327.3 µA mM−1 cm−2) was obtained from CV compared to DPV, a wider linear calibration curve between 0.25 and 1500 µM was obtained in CV. Studies performed in tablet samples confirmed that the Fe3O4@CPE exhibits high applicability for selective and accurate voltammetric determination of MNP in real samples.

LC-MS/MS method for determination of r-RGD-hirudin in human plasma and its application in pharmacokinetic study

ObjectiveThis study aimed to develop a simple, sensitive, and selective Liquid chromatography with a Mass spectroscopic method for simultaneous quantification of a recombinant bifunctional hirudin (r-RGD-Hirudin, Bifunctional Hirudin, BFH) in human plasma and verify its effectiveness. MethodsThe analytes and the internal standards from human plasma were extracted using the solid-phase extraction technique. The reconstituted samples were chromatographed on Waters C18 column (BEH 50 × 2.1 mm, 1.7 μm) using a mixture of 0.1% formic acid/acetonitrile (85%/15%, v/v) with gradient elution as the initial mobile phase at a flow rate of 0.3 mL/min. ResultsThe effectiveness of the proposed method was verified over the concentration range of 10–2000 ng/mL for r-RGD-Hirudin. A linear calibration curve was obtained. The precision and accuracy of BFH in the intra- and inter-day runs fell within the range of ±15% at LQC, GMQC, MQC and HQC concentrations. The extraction recoveries and matrix effect at two quality control (QC) levels for BFH were confirmed to conform to the relevant requirement. ConclusionThe proposed method was successfully adapted to examine the pharmacokinetics of BFH in 40 Chinese healthy volunteers, respectively.

Simultaneous Determination of Pyrethroid Insecticides in Foods of Animal Origins Using the Modified QuEChERS Method and Gas Chromatography-Mass Spectrometry.

Pyrethroid insecticides are used in agriculture to treat parasites in livestock. This study developed a simultaneous residue analysis method to measure seventeen pyrethroid insecticides in foods of animal origin, including beef, pork, chicken, milk, and eggs. The method, which comprises instrumental analysis using gas chromatography-tandem mass spectrometry and a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method for pretreatment, was optimized to verify the applicability of the method. A mixture of acetonitrile, ethyl acetate, and original salt (MgSO4 4 g, NaCl 1 g) was used as the extraction solvent and salt. MgSO4 (150 mg) primary secondary amine (25 mg) and graphitized carbon black (25 mg) were selected for dispersive solid phase extraction (d-SPE). The method limit of quantitation was 0.01 mg/L, and the linearity of the matrix-matched calibration curves was reasonable (R2 &gt; 0.99). Recovery tests were performed at three concentrations (LOQ, 10 LOQ, and 50 LOQ). Good recoveries (75.2109.8%) and reproducibility (coefficient of variation &lt;10%) were obtained. The matrix effects were in the range of -35.8 to 56.0%. The established method was fully validated and can be used as an official analytical method for quantifying pyrethroid insecticides in animal commodities.

Label-free electrochemical detection of glucose and glycated hemoglobin (HbA1c)

Measuring glucose together with glycated hemoglobin (HbA1c) could provide short-term and long-term information of blood glycemic condition after a single treatment. However, it has been a challenge to quantify glucose and HbA1c from single sample drop and strip of electrodes with suitable sensitivity, selectivity, and efficiency. In this paper, we demonstrated a label free & single sample drop electrochemical detection method of glucose and HbA1c by modifying carbon electrodes. Glucose oxidase and capture antibodies (C-Ab) against HbA1c were immobilized onto the first working electrode (WE1) and the second working electrode (WE2) of dual working screen-printed carbon electrodes (DWSPCEs), respectively. WE2 was modified with Gold Nano Flower. After that, 3-mercaptopropionic acid was coated as a linker. Finally, C-Ab was bonded by the linker. The relationship between gold surface area and concentration of HgAuCl4 was evaluated to optimize HbA1c incubation time. Linear calibration curves for glucose concentration (0.02–35 mM), HbA1c concentration (0.01 to 1mgml−1), and HbA1c percentage solution (0–14%) were obtained, with correlation coefficients of 0.99. Sensitivities of the biosensor for glucose and HbA1c were 0.5 μAmm−2mM−1 and 0.09 μAmm−2μg−1ml, respectively. The biosensor also showed proper stability (>93%, 45days) and selectivity (>92%). The efficiency of the proposed biosensor was also compared with those of commercial kits using whole blood samples of diabetic and normal cases. Results of this study demonstrate that this biosensor can measure both glucose and HbA1c electrochemically using label-free methods to overview glycemic conditions of blood samples using cheap and commercially viable dual carbon electrode-based biosensors.

Optimization of a Single Substrate-Based Fluorometric Assay for Glucose and Lactate Measurement to Assess Preimplantation Single Embryo Quality and Blood in Obese Mouse and Clinical Human Samples.

A fluorometric assay for single substrate-based glucose and lactate measurements was demonstrated by adopting an already established protocol for glucose and by optimizing pH, enzyme concentration, substrate concentration, and types of buffers for lactate. Linear calibration curves for glucose and lactate concentrations from 1 to 100 μM were obtained with correlation coefficients (R2) of 0.94 and 0.98, respectively. First, with the optimized protocol, single embryo quality was successfully evaluated. Three different initial stages of embryos (n = 58) were cultured for 24 h, and glycolytic activities were calculated by measuring amounts of glucose consumption and lactate production. Results showed that embryos cultured at a later stage had lower glycolytic activities, implying more developmental activities. Second, glucose and lactate concentrations in blood plasma of diet-induced obese (DIO) mice were measured. Levels of both glucose and lactate in DIO mice were higher than those in normal mice by 2.15 and 3.8 mmol/L, respectively (both p < 0.001). Finally, clinical serum samples were analyzed and categorized into three groups based on their measured glucose concentrations: normal (4.73 ± 0.29 mmol/L), prediabetic (6.49 ± 0.13 mmol/L), and diabetic (11.34 ± 1.36 mmol/L) (p < 0.05). Collectively, this developed technique can be used to select a high-quality embryo for transfer as well as to measure glucose and lactate levels in other biological samples.

REVERSE PHASE HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY-ULTRAVIOLET-BASED APPROACH FOR METHOD DEVELOPMENT AND VALIDATION OF LACOSAMIDE ESTIMATION IN HUMAN SERUM

Objective: The main aim of the study was to develop and validate a simple, accurate, and rapid isocratic reverse phase high-performance liquid chromatographic method with UV detection for the determination of lacosamide, an antiepileptic agent, in human serum. Methods: Chromatographic separation was performed using a reverse phase chromatographic column (Zorbax SB-C18, 5 μm 4.6×250 mm) with a mobile phase being a mixture of potassium dihydrogen phosphate buffer (pH adjusted to 3.0 with orthophosphoric acid) and acetonitrile (ratio of 83:17 v/v) at a flow rate of 1.2 mL/min. UV detection was carried out at 210 nm and the sample temperature was maintained at 4°C. Results: Linear calibration curves in the range of 1.012–40.894 μg/ml gave a correlation coefficient of 0.9988. The intra-day (n=6) and inter-day (n=18) precision (expressed as relative standard deviation) were in the range of 0.79–2.485% and from 0.99 to 3.21%, respectively. The retention time (in minutes) of lacosamide and internal standard was approximately 8.785±0.19 and 3.985±0.77, respectively, with no matrix interference. The method was validated for system suitability, specificity, precision, accuracy, robustness, linearity, limit of detection, and limit of quantification following the International Conference on Harmonization guidelines. The method was further validated using sera of epileptic patients consuming lacosamide, and it was observed that the results matched with the patients’ clinical response. Conclusion: Our method developed to estimate serum lacosamide level is simple, cost-effective, and reliable for therapeutic drug monitoring.

Validation of a Multi-Residue Analysis Method for 287 Pesticides in Citrus Fruits Mandarin Orange and Grapefruit Using Liquid Chromatography-Tandem Mass Spectrometry.

Since the introduction of the positive list system (PLS) for agricultural products in the Republic of Korea, the demand for a quick, easy multi-residue analysis method increased continuously. Herein, the quick, easy, cheap, effective, rugged, and safe (QuEChERS) technique combined with liquid chromatography−tandem mass spectrometry was employed to optimize a method for the multi-residue analysis of 287 pesticide residues in mandarin orange and grapefruit. Method validation was conducted in terms of selectivity, limit of quantitation (LOQ), linearity, accuracy, precision, and matrix effect. All the compounds at low spiking levels (1, 2.5, 5, or 10 mg/kg) could be quantified at LOQs lower than 0.01 mg/kg (PLS level). The linearity of the matrix-matched calibration curve for each compound is in the range 0.5−50 μg/L, and its coefficient of determination (R2) is >0.990. Satisfactory recovery values of 70−120% with a relative standard deviation of ≤20% are obtained for all compounds in the mandarin orange and grapefruit samples. A negligible matrix effect (−20−20%) is observed for more than 94.8% and 85.4% of the pesticides in mandarin orange and grapefruit, respectively. Therefore, this analytical method can contribute to pesticide residue analyses of citrus fruits for routine laboratory testing.

A customizable cost-effective design for printed circuit board-based nanolayered gold screen-printed electrode: From fabrication to bioapplications.

Screen-printed electrodes (SPEs) are promising candidates for fabricating biosensing platforms in the laboratory and industry due to the various advantages they involve. The primary method for fabricating SPEs is 2D printing. However, commercial SPEs have some limitations due to the specific ports and connections they require, inflexible design, high prices, and decreased efficiency after a short time. This article introduces high performance, feasible, and cost-effective gold SPEs based on the combination of printed circuit board substrate (PCBs) and sputtering methods for electrochemical biosensing platforms. First, we discuss a general gold SPE development procedure that helps researchers to develop specific designs. The final developed version of SPEs was characterized in the second step, showing positive performance in electrochemical parameters because of the optimization of design and fabrication steps. In the study's final phase, SPEs were used to fabricate a simple platform for breast cancer cell detection as a proof of concept without using any linker or labeling step. The designed immunosensor is very simple and cost-effective, showing a linear calibration curve in the range of 10 - 2× 102 cellsmL-1 (R 2 = 0.985, S/N = 3). This research can be used as a reference for future studies in SPEs-based biosensors because of the flexibility of its design and the accessibility of the manufacturing equipment required.

Calibration of high performance size exclusion chromatography (HPSEC) for molecular weight estimation of aquatic humic substances

Three high performance size exclusion chromatography (HPSEC) columns were compared, along with mobile phase chemistry and calibration standards, for the determination of apparent molecular weight (AMW) of aquatic humic substances using a UV absorbance detector (λ = 254 nm). The addition of 10 % organic solvent did not influence peak elution times of sodium polystyrene sulfonate (PSS) standards or chromatograms of Suwannee River humic acid (SRHA) or fulvic acid (SRFA) but did result in an additional peak being detected in a treated municipal wastewater sample (WWT). Mobile phase concentration was found to have a greater effect on peak position of PSS standards and SRHA than mobile phase pH or sample injection volume. Several chemicals of known molecular weight were tested alongside PSS standards, with salicylic acid (138.1 Da) and 4-chlorobenzoic acid (156.6 Da) resulting in retention times that aligned with the PSS MW standards. Of the three columns tested, the two with comparable pore sizes (i.e., 250 and 300 Å) were found to result in similar peak elution times and highly linear calibration curves over the range of 210–17,000 Da, while the column with the smaller pore size (i.e., 100 Å) gave better peak separation in the low AMW range (i.e., < 1000 Da). Estimations of AMW of SRHA using various sets of calibration standards on one of the three columns tested ranged from 1080 to 2799 Da using 0.02 M NH4CH3CO2 as eluent and 60-µL injections. AMW of SRFA ranged from 939 to 2434 Da for the same conditions.

English

The chemical analysis of CaCO3 contents of soils provide information about not only efficiency of soil for supplying plant with nutrients but also identification of factors affecting this efficiency in the soil. The aim of the current experiment was to develop new methods based on sensors and compare with conventional Scheibler method. The CO2 liberated by the action of HCl on CaCO3 content of the soil in a reaction bottle and an accumulation chamber was determined by pressure sensor and CO2 sensor, respectively. The CaCO3 contents of soils were estimated using the regression equation of standard curves. The CaCO3 contents of soils obtained using Scheibler calcimetric, pressure and CO2 sensor methods ranged from 0.20 to 54.74%, 0.25 to 54.10% and 0.55 to 53.05%, respectively. On the basis of linearity of calibration curve and high correlation with Scheibler calcimetric method it can be said that developed pressure and CO2 sensor methods appears to be very useful for quantification of CaCO3 contents of soils. The pressure sensor has provided the opportunity in developing a simple and handy device with an affordable cost to measure CaCO3 contents of soils as accurately as Scheibler calcimeter when compared with CO2 sensor method. Even if there is a good relationship between Scheibler calcimetric method and CO2 sensor method the cost of CO2 sensor method may limit the use in determination of CaCO3 contents of soils. However, CO2 sensor method can be used to monitor CO2 evolved in biochemical process such as respiration and fermentation

Nano-ZnO-assisted matrix solid phase dispersion microextraction combined with an in situ DES-based aqueous two-phase system for the enrichment of multiple active compounds in honeysuckles

In this work, a novel method of matrix solid phase dispersion-assisted aqueous two-phase system microextraction as sample pretreatment was developed, and ultra-high performance liquid chromatography was used to separate multiple active compounds in honeysuckles. Nano-ZnO was used as the adsorbent for matrix solid phase dispersion microextraction, and green deep eutectic solvents were used as the extraction solvent for enrichment of target analytes in an aqueous two-phase system. In this work, single-factor experiments and Box-Behnken experimental design combined with response surface methodology were used to study and optimize the parameters of matrix solid phase dispersion-assisted aqueous two-phase system microextraction. The fitted models extracted from chlorogenic acid, loganin, sweroside, rutin, luteoloside, isochlorogenic acid A, and isochlorogenic acid C were successfully established and validated. Based on the optimal conditions, the correlation coefficient ranges from 0.9983 to 0.9998, and the detection limits of each analyte are in the range of 1.360–13.531 ng/mL, indicating that the method has a good linear calibration curve and good sensitivity. The recoveries of the seven target analytes in honeysuckles at two levels of intensification are between 71.35% and 104.77%, and the relative standard deviations are lower than 4.28%, showing that the mentioned method has satisfactory recovery efficiency and high reproducibility. In conclusion, this study demonstrates that matrix solid phase dispersion-assisted aqueous two-phase system microextraction is a novel method that is efficient, environmentally friendly and economical and has the potential to extract multiple active components from honeysuckles.

Fabric phase sorptive extraction combined with high performance liquid chromatography for the determination of favipiravir in human plasma and breast milk

A fast procedure obtained by the combination of fabric phase extraction (FPSE) with high performance liquid chromatography (HPLC) has been developed and validated for the quantification of favipiravir (FVP) in human plasma and breast milk. A sol-gel polycaprolactone-block-polydimethylsiloxane-block-polycaprolactone (sol-gel PCAP-PDMS-PCAP) coated on 100% cellose cotton fabric was selected as the most efficient membrane for FPSE in human plasma and breast milk samples. HPLC-UV analysis were performed using a RP C18 column under isocratic conditions. Under these optimezed settings, the overall chromatographic analysis time was limited to only 5 min without encountering any observable matrix interferences. Following the method validation procedure, the herein assay shows a linear calibration curve over the range of 0.2–50 µg/mL and 0.5–25 µg/mL for plasma and breast milk, respectively. The method sensitivities in terms of limit of detection (LOD) and limit of quantification (LOQ), validated in both the matrices, have been found to be 0.06 and 0.2 µg/mL for plasma and 0.15 and 0.5 µg/mL for milk, respectively. Intraday and interday precision and trueness, accordingly to the International Guidelines, were validated and were below 3.61% for both the matrices. The herein method was further tested on real samples in order to highlight the applicability and the advantage for therapeutic drug monitoring (TDM) applications. To the best of our knowledge, this is the first validated FPSE-HPLC-UV method in human plasma and breast milk for TDM purposes applied on real samples. The validated method provides fast, simple, cost reduced, and sensitive assay for the direct quantification of favipiravir in real biological matrices, also appliyng a well-known rugged and cheap instrument configuration.

Electrochemical Sensor for Ascorbic Acid, Acetaminophen and Nitrite Based on Organoclay/Zr‐MOF Film Modified Glassy Carbon Electrode

AbstractA composite (Sa‐HTDMA/UiO‐66) consisting of organoclay (Sa‐HTDMA) and a metal‐organic framework (UiO‐66) was prepared using organically modified natural Cameroonian clay and Zr‐MOF. The organoclay was obtained by intercalating in its interlayer hexadecyltrimethyl ammonium cation (HTDMA). The composite was then used to form a film onto a glassy carbon electrode (GCE) by drop coating (Sa‐HTDMA/UiO‐66/GCE). Electrochemical responses recorded at the as‐prepared modified electrodes for ascorbic acid (AA), acetaminophen (AC) and nitrite (NO2−) were investigated using cyclic and linear sweep voltammetry. The results revealed that Sa‐HTDMA/UiO‐66/GCE exhibited a favorable behavior for individual and simultaneous sensing of AA, AC and NO2−. Additionally, compared with UiO‐66 modified GCE, the composite enabled good performance of the electrode. Under the optimum conditions, the linear calibration curves were attained in the following ranges: 1–650 μM for AA, 1–700 μM for AC and 1–600 μM for NO2− with the respective detection limits of 0.01, 0.19 and 0.33 μM. Application of the sensors to determine AA and AC in pharmaceutical preparations, and NO2− in tap water, was successful.

A novel cascade signal amplification strategy integrating CRISPR/Cas13a and branched hybridization chain reaction for ultra-sensitive and specific SERS detection of disease-related nucleic acids

The molecular diagnosis of disease by high-sensitively and specifically detecting extremely trace amounts of nucleic acid biomarkers in biological samples is still a great challenge, and the powerful sensing strategy has become an urgent need for basic researches and clinical applications. Herein, a novel one-pot cascade signal amplification strategy (Cas13a-bHCR) integrating CRISPR/Cas13a system (Cas13a) and branched hybridization chain reaction (bHCR) was proposed for ultra-highly sensitive and specific SERS assay of disease-related nucleic acids on SERS-active silver nanorods sensing chips. The Cas13a-bHCR based SERS assay of gastric cancer-related miRNA-106a (miR-106a) can be achieved within 60 min and output significantly enhanced SERS signal due to the multiple signal amplification, which possesses a good linear calibration curve from 10 aM to 1 nM with the limit of detection (LOD) low to 8.55 aM for detecting gastric cancer-related miR-106a in human serum. The Cas13a-bHCR based SERS sensing also shows good specificity, uniformity, repeatability and reliability, and has good practicability for detection of miR-106a in clinical samples, which can provide a potential powerful tool for SERS detection of disease-related nucleic acids and promise brighter prospects in the field of clinical diagnosis of early disease.

Needle extraction device for rapid and quantitative gas chromatographic determination of volatile chlorinated hydrocarbons and benzene in soil

A rapid and quantitative analytical method for volatile chlorinated hydrocarbons and benzene, such as chloroethylene, dichloromethane, and carbon tetrachloride, in soil samples was developed using a needle-type extraction device packed with activated carbon-based adsorbents. The soil sample of 10 g was placed in a glass cartridge and fixed with quartz wool to make sure not to move during the extraction process. After the internal standard solution was spiked into the soil sample, the cartridge was sealed with a polytetrafluoroethylene adapter, and the needle extraction device was used to collect the headspace gas. Analytes were purged from the soil sample and collected on the adsorbent, while pure nitrogen gas was introduced to the soil sample during the sample collection. The sampling time was approximately 10 min for 100 mL of gas sampling. After the sampling process, the extraction needle was directly inserted into a heated injection port of gas chromatography equipped with flame ionization detector (GC-FID) or that hyphenated to mass spectrometry (GC–MS). The extracted VOCs were thermally desorbed and simultaneously introduced to a GC capillary column for subsequent separation and determination. The limit of detection and limit of quantification of all the examined analytes was less than 20 and 60 ng/10 g soil in GC-FID and less than 2.5 and 7.5 ng/10 g soil in the case of GC–MS. Linear calibration curves were obtained up to 10 μg/10 g soil for all the analytes. The relative standard deviations of the ratio of analyte peak area and internal standard peak area were less than 10%. The recovery and sensitivity of analytes confirmed in the proposed method were compared with that obtained with a standard method conventionally employed.

Synthesis of oil palm empty fruit bunch-based magnetic-carboxymethyl cellulose nanofiber composite for magnetic solid-phase extraction of organophosphorus pesticides in environmental water samples

This study investigated the development of a magnetic-carboxymethyl cellulose nanofiber (Fe3O4-cmCNF) composite from oil palm empty fruit bunch (OPEFB) as a promising adsorbent for the determination of organophosphorus pesticides (OPPs) in water samples via the magnetic solid-phase extraction (MSPE). The Fe3O4-cmCNF was prepared via the alkaline method and surface-modified using the carboxymethylation and sol–gel technique. The physicochemical characteristics of the Fe3O4-cmCNF were evaluated via FT-IR, VSM, SEM, TEM, XRD, TGA, and BET analysis. Diazinon, fenitrothion, and malathion were selected as the model analytes to examine the feasibility and performance of the Fe3O4-cmCNF-based MSPE to detect OPPs in real environmental water samples using gas chromatography-micro-electron capture detector (GC-µECD). Experimental parameters that affected the extraction efficiency were optimized, including the type and amount of adsorbent, extraction time, pH, type of elution solvent, and ionic strength. Based on the results, the prepared adsorbent showed a high affinity towards OPPs through hydrogen bonding as well as hydrophobic and electrostatic interaction. Under optimum conditions, the linear calibration curves were achieved for diazinon, fenitrothion, and malathion with a concentration range of 0.1–200 ng mL−1 and a suitable determination coefficient (r2) between 0.9962 and 0.9995. Furthermore, acceptable intra- and inter-day precisions were obtained between the range 1.7–4.9 % and 2.0–14.0 %, respectively. The LOD for diazinon, fenitrothion, and malathion was determined at 0.03 ng mL−1, with a satisfactory relative recovery range of 81.8–119.6 %. OPPs residues were detected in river water (0.27–0.39 ng mL−1) and wastewater (0.41–1.31 ng mL−1), indicating that the Fe3O4-cmCNF is a suitable composite for the determination of OPPs in real samples.