Sample Pretreatment Procedure Research Articles

Trypsin Encapsulation in the Zeolitic Imidazolate Framework for Low-Molecular Weight Protein Analysis with High Selectivity and Efficiency.

Low-molecular weight proteins (LWPs) are important sources of biological information in biomarkers, signaling molecules, and pathology. However, the separation and analysis of LWPs in complex biological samples are challenging, mainly due to their low abundance and the complex sample pretreatment procedure. Herein, trypsin modified by poly(acrylic acid) (PAA) was encapsulated by a zeolitic imidazolate framework (ZIF-L). Mesopores were formed on the ZIF-L with the introduction of PAA. An alternative strategy for separation and pretreatment of LWPs was developed based on the prepared ZIF-L-encapsulated trypsin with adjustable pore size. The mesoporous structure of the prepared materials selectively excluded high-molecular weight proteins from the reaction system, allowing LWPs to enter the pores and react with the internal trypsin, resulting in an improved separation efficiency. The hydrophobicity of the ZIF-L simplified the digestion process by inducing significant structural changes in substrate proteins. In addition, the enzymatic activity was significantly enhanced by the developed encapsulation method that maintained the enzyme conformation, allowed low mass transfer resistance, and possessed a high enzyme-to-substrate ratio. As a result, the ZIF-L-encapsulated trypsin can achieve highly selective separation, valid denaturation, and efficient digestion of LWPs in a short time by simply mixing with substrate proteins, greatly simplifying the separation and pretreatment process of the traditional hydrolysis method. The prepared materials and the developed strategy demonstrated an excellent size-selective assay performance in model protein mixtures, showing great potential in the application of proteomics analysis.

A multiplex UPLC-MS/MS method for the quantification of three PD-L1 checkpoint inhibitors, atezolizumab, avelumab, and durvalumab, in human serum

Background and aimTo support pharmacokinetic studies, a multiplex UPLC-MS/MS assay was developed and validated to quantify PD-L1 checkpoint inhibitors atezolizumab, avelumab, and durvalumab in serum. MethodsA bottom-up sample pre-treatment procedure was developed to determine atezolizumab, avelumab, and durvalumab in serum. This procedure consisted of (1) precipitation of the monoclonal antibody with ammonium sulfate, (2) reduction with dithiothreitol, (3) denaturation with methanol, and (4) tryptic digestion of the protein. The unique signature peptides resulting after sample pre-treatment of the antibodies were measured using UPLC-MS/MS with a total run time of 11 minutes. The clinical application was evaluated by analyzing 114 atezolizumab patient samples. ResultsThe developed method was found to be accurate and precise for all three analytes over a concentration range of 3.00–150 µg/mL. No endogenous interference was present in serum samples. Cross-interference experiments showed no cross-analyte interference and acceptable cross-internal standard interference. In addition, no substantial carry-over was observed. The stable isotopically labeled signature peptides were most effective in compensating for matrix effects. Recovery based on back-calculated concentrations of calibration standards and quality control samples was found to be high. The analytes were stable for at least three freeze-thaw cycles, for 42 hours at processing conditions, for at least two days at 2–8°C in the final extract, for five days before re-injection analysis at 4°C, and long-term for at least 11 months at −70°C. The assay was tested for its applicability in clinical practice. For this purpose, 114 atezolizumab patient samples were measured. ConclusionA multiplex UPLC-MS/MS assay was developed and validated to quantify atezolizumab, avelumab, and durvalumab in human serum. The applicability of this method was demonstrated by the analysis of clinical atezolizumab samples. The method is suitable to support clinical pharmacokinetic studies involving atezolizumab, avelumab, or durvalumab.

Magnetic graphene oxide and vertically-ordered mesoporous silica film for universal and sensitive homogeneous electrochemiluminescence aptasensor platform

Herein, we demonstrated a convenient and highly sensitive homogeneous electrochemiluminescence (ECL) aptasensor platform by combination of magnetic composite probe and vertically-ordered mesoporous silica films (VMSF). Magnetic composite probe composed of biorecognition element (target-specific aptamer), ECL signal reporter (Ru(bpy)32+) and large-scale magnetic graphene oxide (M−GO), can be prepared by simple incubation, magnetic separation and redispersion prior to use. High-affinity and specific binding between target and aptamer can detach aptamer from M−GO and simultaneously release the slight amount of Ru(bpy)32+ into a solution, which can be sensitively detected by VMSF modified indium tin oxide (VMSF/ITO) due to the excellent electrostatic preconcentration capacity of VMSF. In this sensing system, detectable signal of Ru(bpy)32+ can be remarkably amplified by VMSF/ITO and meanwhile background signal can be reduced by the adsorption capacity of M−GO and size exclusion property of VMSF/ITO, effectively promoting the analytical performance of the present homogeneous ECL aptasensor. The applicability and universality of this sensing platform was confirmed by employing alpha fetoprotein (AFP) and prostate specific antigen (PSA) as the target models and their detection limits were 0.08 pg/mL and 9.6 pg/mL, respectively. Furthermore, the designed homogeneous ECL aptasensor platform is label-free, immobilization-free, low-cost, and free of additional electrode modification and sample pretreatment procedures, rendering a simple sensing strategy for quantitative determination of various biomarkers in clinical diagnosis by adapting the specific aptamer.

Development a green analytical methodology for the sensitive determination of antidepressant drugs using fabric phase sorptive extraction as a simple sample pretreatment procedure

A new enrichment and determination method including HPLC-DAD analysis after fabric phase sorptive extraction (FPSE) has been developed to monitor trace amounts of antidepressant drugs including Amitriptyline (AMP), Fluoxetine (FLU), Vilazodone (VLZ), and Duloxetine (DUL). The target antidepressant drug molecules were retained onto the medium-polar sol–gel polytetrahydrofuran (PTHF) coated fabric phase sorptive extraction membrane in the presence of pH 9.0 medium, and back-extracted by desorbing to a smaller volume of acetonitrile (ACN) before chromatographic determinations. Chemical characterization of the used fabric phase sorptive extraction membrane and experimental variables of FPSE were studied step by step and optimized. HPLC analysis of antidepressant drugs were carried out by isocratic elution of 20 % methanol, 50 % trifluoroacetic acid (0.1 %, v:v) (TFA), 30 % acetonitrile (ACN). In the developed method. After enrichment of antidepressant molecules, 20 % Methanol, 50 % trifluoroacetic Acid (0.1 % TFA), and 30 % ACN by using C18 column. The detection limits for target antidepressant drugs under optimized conditions were found lower than 0.38 ng mL−1. The relative standard deviation (% RSD) values were calculated below 4.80 %. The developed method has been successfully applied to synthetic urine, real urine and pharmaceutical tablet samples and quantitative results have been obtained in recovery experiments.

Supramolecular phenylboronic acid@CD-MOFs: Enrichment integrated derivatization strategy for diols-containing short-chain aliphatic compounds

This work explores an enrichment integrated derivatization strategy for diols-containing short-chain aliphatic compounds (DSCAs) by using cyclodextrin (CD)-metal–organic frameworks (MOFs) as adsorbents. For this purpose, α-, β-, γ-CD-MOFs with different sizes of hydrophobic cavities were prepared and their encapsulation ability towards polycyclic aromatic hydrocarbons, especially phenylboronic acid (PBA), was investigated. It is found that the formed supramolecular adsorbents PBA@CD-MOFs can simultaneously perform the enrichment and derivatization of DSCAs in organic solution, simplifying the sample pre-treatment procedure of the DSCAs. Finally, an analytical method based on solid-phase extraction combined with high-performance liquid chromatography (HPLC) was established for the detection of 3-monochloropropane-1,2-diol (3-MCPD) in canned samples. The relative recoveries of three analytes are 82.4 to 87.5 %, the intra- and inter-day relative standard deviations (RSDs) are less than 10.9 %, and the limits of detection (LODs) are 0.934–2.77 ng∙g−1. In conclusion, the enrichment integrated derivatization strategy can be used as an alternative to the traditional sample pretreatment method, which usually requires enrichment, elution and derivatization for the detection of DSCAs in various food samples.

Addressing Domain Specificity in the Development of a Cell-Based Binding Assay for the Detection of Neutralizing Antibodies Against a CD47xPD-L1 Bispecific Antibody

PF-07257876 is a bispecific antibody being developed for the treatment of certain advanced or metastatic solid tumors. To support clinical development of PF-07257876, neutralizing antibody (NAb) assays were developed as part of a tiered immunogenicity testing approach. Because PF-07257876 targets both CD47 and PD-L1, determination of domain specificity of a NAb response may provide additional insight relating to PK, efficacy, and safety. Due to limitations of functional cell systems, two cell-based binding assays were developed using electrochemiluminescence to detect domain-specific NAb. While both NAb assays utilized a cell-based binding approach and shared certain requirements, such as sensitivity and tolerance to potentially interfering substances, the development of each assay faced unique challenges. Among the hurdles encountered, achieving drug tolerance while preserving domain specificity for CD47 proved particularly challenging. Consequently, a sample pretreatment procedure to isolate NAb from potentially interfering substances was necessary. The sample pretreatment procedure developed was based on a bead-extraction and acid dissociation (BEAD) approach. However, the use of the standard BEAD approach with whole drug to capture NAb resulted in loss of NAb detection under certain circumstances. Specifically, mock samples containing a mixture of NAb positive controls against both binding domains of the bispecific antibody produced false-negative results in the cell-based binding assay. An adaptation made to the standard BEAD approach restored domain-specific NAb detection, while also contributing to an assay sensitivity of 1 µg/mL in the presence of a clinically relevant drug tolerance level of up to 400 µg/mL.Graphical

N-Doped Graphene Quantum Dots Confined within Silica Nanochannels for Enhanced Electrochemical Detection of Doxorubicin.

Herein, we describe a fast and highly sensitive electrochemical sensor for doxorubicin (DOX) detection based on the indium tin oxide (ITO) modified with a binary material consisting of vertically-ordered mesoporous silica films (VMSFs) and N-doped graphene quantum dots (NGQDs). VMSFs, with high permeability and efficient molecular transport capacity, is attached to the ITO electrode via a rapid and controllable electrochemical method, which can serve as a solid template for the confinement of numerous NGQDs through facile electrophoresis. By virtue of the excellent charge transfer capacity, π-π and electrostatic preconcentration effects of NGQDs, as well as the electrostatic enrichment ability of VMSF, the presented NGQDs@VMSF/ITO shows amplified electrochemical signal towards DOX with a positive charge, resulting in good analytical performance in terms of a wide linear range (5 nM~0.1 μM and 0.1~1 μM), high sensitivity (30.4 μA μM-1), and a low limit of detection (0.5 nM). Moreover, due to the molecular sieving property of VMSF, the developed NGQDs@VMSF/ITO sensor has good selectivity and works well in human serum and urine samples, with recoveries of 97.0~109%, thus providing a simple and reliable method for the direct electrochemical analysis of DOX without complex sample pretreatment procedures.

Optimization of QuEChERS Method for Antibiotic Residue Analysis in Animal Foods via Response Surface Methodology

The present study employed a modified QuEChERS method to systematically analyze the presence of fifteen quinolone and seven tetracycline antibiotic residues in local animal food. Additionally, a multi-level four-factor Box–Behnken design (BBD) within the framework of response surface methodology (RSM) was utilized to evaluate the factors impacting the detection efficiency of the sample pretreatment procedure. Optimization was performed via Design Expert® 10.0.3, and the factors, including the volume of the acetonitrile, the addition of formic acid, the duration of the extraction, and the addition of EDTA, were combined with experimental design until an optimal solution was reached. Finally, the sample was tested via ultra-high performance liquid chromatography-quadrupole-linear ion trap mass spectrometry (UPLC/MS/MS) in both multiple reaction monitoring (MRM) and enhanced product ion (EPI) scan modes on a QTRAP® 5500 instrument (AB SCIEX instruments, Framingham, MA, USA). The overall average recoveries from actual samples fortified with 22 antibiotics at three levels ranged from 73.8% to 98.5% based on the use of matrix-fortified calibration, with variations ranging from 5.80 to 12.4% (n = 6). The limits of detection and quantification were 0.3 μg kg−1 and 1.0 μg kg−1, respectively. Lastly, the modified method was applied to practical sample analysis in the daily risk monitoring and assessment of food safety with satisfactory stability and robustness.

Simultaneous determination of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in Pu-erh tea by dispersive solid-phase extraction coupled with GC-MS/MS

A novel method for the simultaneous determination of 13 PAHs and 18 PCBs residues in Pu-erh tea samples was established by combining GC-MS/MS with dispersive-solid phase extraction (d-SPE). Sample pretreatment procedure was achieved by NaCl addition and using acetone/ethyl acetate/n-hexane (50:30:20, v/v/v) extraction followed by d-SPE clean-up with strong cationic exchanger (SCX), primary secondary amine (PSA), polyvinylpolypyrrolidone (PVPP) and graphitized carbon black (GCB). The proposed method had good linearity in the range of 0.5–200 μg/L with correlation coefficients (R2 > 0.998). The detection limit ranges (LODs) were from 0.2 to 1.5 µg/kg. The spiked experiments in raw Pu-erh tea and ripened Pu-erh tea at 2.5–50 µg/kg concentrations showed satisfactory recoveries (70.2–114.7%) for all analytes with RSDs of < 10%. The validated methodology was successfully applied to 86 Pu-erh tea samples. No PCBs residue was more than LODs, and the detection frequency and concentration of PAHs in different types of Pu-erh tea varies greatly were found.

Sulfonated magnetic graphite carbon nitride solid-phase extraction-ultra performance liquid chromatography-tandem mass spectrometry for screening malachite green and leucomalachite green in freshwater fish

Malachite green (MG) and its metabolite, leucomalachite green (LMG), exert toxic effects on the human body. The use of these dyes is illegal, but they are still detected in aquatic products. Freshwater fish are aquatic products with the high non-qualified rates. Therefore, the sensitive screening of MG and LMG in freshwater fish is of great importance to ensure the safety of aquatic products. Owing to the low contents of MG and LMG in fish and the complex matrix of actual samples, sample preparation is required before detection to purify impurities and enrich the target compounds. Graphite carbon nitride (GCN), a polymer material composed of C, N, and H, has good chemical and thermal stability, a large specific surface area, and a large number of active sites. It has a wide range of application prospects in adsorption and can be used in food safety testing when compounded with Fe3O4 to form magnetic graphite carbon nitride (MGCN). In this study, sulfonated magnetic graphite carbon nitride (S-MGCN) was prepared by further functionalizing MGCN with sulfonic acid. After characterization by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and vibrating sample magnetometry (VSM), a magnetic solid-phase extraction (MSPE) method based on S-MGCN was established to extract MG and LMG from freshwater fish. The targets were screened using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Following sulfonic acid functionalization, S-MGCN showed increased electrostatic interactions based on the MGCN adsorption mechanism, which includes hydrogen bonds and π-π interactions; thus, its adsorption efficiency was significantly improved. The matrix effects were -42.21% and -33.77% before functionalization, -11.40% and -7.84% after functionalization, thus confirming that S-MGCN has significant matrix removal ability. Given that S-MGCN demonstrated excellent efficiency as an MSPE adsorbent, the adsorption conditions for S-MGCN were optimized. The optimal conditions were as follows: adsorbent dosage, 15 mg; adsorption time, 2 min; solution pH, 5; and ionic strength, not adjusted. Under these conditions, the adsorption efficiency of S-MGCN could reach 94.2%. Different organic solvents were used to elute adsorbed MG and LMG, and the desorption efficiency peaked when 1%(v/v) ammonia acetonitrile was used as the elution solvent. The elution volume was also optimized, and a maximum desorption efficiency of 93.2% was obtained when 1 mL of 1%(v/v) ammonia acetonitrile was added to S-MGCN. The limits of detection (LODs) and quantification (LOQs) of the two targets were determined at signal-to-noise ratios (S/N) of 3 and 10, respectively. The LODs and LOQs were 0.075 μg/kg and 0.25 μg/kg, respectively. The linear ranges of the two target compounds were 0.25-20.0 μg/kg with correlation coefficients (r) greater than 0.998. To assess accuracy and precision, we prepared spiked samples at three levels (low, medium, and high) with six parallel samples per level (n=6). The recoveries ranged from 88.8% to 105.9%. The intra- and inter-day relative standard deviations were 5.4%-13.7% (n=6) and 3.3%-11.1% (n=3), respectively. Compared with the national standard method, the proposed method features simpler sample pretreatment procedures, less use of organic reagents (5 mL), and a shorter extraction time (2 min); moreover, the method does not require complicated elution steps, and the eluent can be directly analyzed by UPLC-MS/MS. The test results of actual samples were consistent with those obtained via the national standard method, thus confirming the practical feasibility of the developed method. The proposed MSPE method based on S-MGCN is an efficient and environmentally friendly method that could provide a new methodological reference for the sensitive screening of MG and LMG in actual samples.

Targeted quantitative metabolomics with a linear mixed-effect model for analysis of urinary nucleosides and deoxynucleosides from bladder cancer patients before and after tumor resection.

In the present study, we developed and validated a fast, simple, and sensitive quantitative method for the simultaneous determination of eleven nucleosides and deoxynucleosides from urine samples. The analyses were performed with the use of liquid chromatography coupled with triple quadrupole mass spectrometry. The sample pretreatment procedure was limited to centrifugation, vortex mixing of urine samples with a methanol/water solution (1:1, v/v), evaporation and dissolution steps. The analysis lasted 20min and was performed in dynamic multiple reaction monitoring mode (dMRM) in positive polarity. Process validation was conducted to determine the linearity, precision, accuracy, limit of quantification, stability, recovery and matrix effect. All validation procedures were carried out in accordance with current FDA and EMA regulations. The validated method was applied for the analysis of 133 urine samples derived from bladder cancer patients before tumor resection and 24h, 2weeks, and 3, 6, 9, and 12months after the surgery. The obtained data sets were analyzed using a linear mixed-effect model. The analysis revealed that concentration level of 2-methylthioadenosine was decreased, while for inosine, it was increased 24h after tumor resection in comparison to the preoperative state. The presented quantitative longitudinal study of urine nucleosides and deoxynucleosides before and up to 12months after bladder tumor resection brings additional prospective insight into the metabolite excretion pattern in bladder cancer disease. Moreover, incurred sample reanalysis was performed proving the robustness and repeatability of the developed targeted method.

HiSorb sorptive extraction for determining salivary short chain fatty acids and hydroxy acids in heart failure patients

Variations in salivary short-chain fatty acids and hydroxy acids (e.g., lactic acid, and 3-hydroxybutyric acid) levels have been suggested to reflect the dysbiosis of human gut microbiota, which represents an additional factor involved in the onset of heart failure (HF) disease. The physical–chemical properties of these metabolites combined with the complex composition of biological matrices mean that sample pre-treatment procedures are almost unavoidable. This work describes a reliable, simple, and organic solvent free protocol for determining short-chain fatty acids and hydroxy acids in stimulated saliva samples collected from heart failure, obese, and hypertensive patients. The procedure is based on in-situ pentafluorobenzyl bromide (PFB-Br) derivatization and HiSorb sorptive extraction coupled to thermal desorption and gas chromatography-tandem mass spectrometry. The HiSorb extraction device is completely compatible with aqueous matrices, thus saving on time and materials associated with organic solvent-extraction methods. A Central Composite Face-Centred experimental design was used for the optimization of the molar ratio between PFB-Br and target analytes, the derivatization temperature, and the reaction time which were 100, 60 °C, and 180 min, respectively. Detection limits in the range 0.1–100 µM were reached using a small amount of saliva (20 µL). The use of sodium acetate-1-13C as an internal standard improved the intra- and inter-day precision of the method which ranged from 10 to 23%. The optimized protocol was successfully applied for what we believe is the first time to evaluate the salivary levels of short chain fatty acids and hydroxy acids in saliva samples of four groups of patients: i) patients admitted to hospital with acute HF symptoms, ii) patients with chronic HF symptoms, iii) patients without HF symptoms but with obesity, and iv) patients without HF symptoms but with hypertension. The first group of patients showed significantly higher levels of salivary acetic acid and lactic acid at hospital admission as well as the lowest values of hexanoic acid and heptanoic acid. Moreover, the significant high levels of acetic acid, propionic acid, and butyric acid observed in HF respect to the other patients suggest the potential link between oral bacteria and gut dysbiosis.

Determination of A1 and A2 β-Casein in Milk Using Characteristic Thermolytic Peptides via Liquid Chromatography-Mass Spectrometry

β-casein, a protein in milk and dairy products, has two main variant forms termed as A1 and A2. A1 β-casein may have adverse effects on humans. The fact that there is only one amino acid variation at the 67th position between A1 and A2 β-casein makes it difficult to distinguish between them. In this study, a novel method using characteristic thermolytic peptides is developed for the determination of A1 and A2 β-casein in milk. Firstly, caseins extracted from milk samples are thermolytic digested at 60 °C without any denaturing reagents required for unfolding proteins, which simplifies the sample pretreatment procedure. The characteristic thermolytic peptides (i.e., fragments 66–76 and 59–76 for A1 and A2 β-casein, respectively) selected to specifically distinguish A1 and A2 β-casein only have eleven or eighteen amino acid moieties. Compared with tryptic characteristic peptides with a length of 49 amino acid moieties, these shorter thermolytic characteristic peptides are more suitable for LC-MS analysis. This novel method, with the advantages of high specificity, high sensitivity, and high efficiency, was successfully applied for the analysis of six milk samples collected from a local supermarket. After further investigation, it is found that this method would contribute to the development of A2 dairy products for a company and the quality inspection of A2 dairy products for a government.

Determination of misoprostol in workplace air by high performance liquid chromatography

Objective: To establish a high performance liquid chromatography method for the determination of misoprostol in workplace air. Methods: From February to August 2021, the misoprostol in the workplace air was collected by glass fiber filter membrane, and theeluent was separated by C18 liquid chromatography column, determined by UV detector, and quantified by external standard method. Results: The quantitative lower limit of misoprostol determination method was 0.05 μg/ml, and the lowest quantitative concentration was 1.4 μg/m(3) (calculated by collecting 75 L air sample). The concentration of misoprostol has a good linear relationship between 0.05 to 10.00 μg/ml. The relative coefficient was 0.9998. The regression equation of the standard working curve was y=495759x-45257. The range of average recovery rates were from 95.5% to 102.8%. The intra-assay precision of the method was 1.2%-4.6%, and the inter-assay precision was 2.0%-5.9%. The samples could be stored stably for 7 days at 4 ℃. Conclusion: The high performance liquid chromatography method for the determination of misoprostol has high sensitivity, good specificity and simple procedure of sample pretreatment. It is suitable for the detection of misoprostol in the workplace air.

Magnetic polyphosphazene@Au particles as substrates for multiple-detection of immunoproteins by surface-enhanced Raman spectroscopy

Au coated magnetic polyphosphazene (MPCTP) composite particles (MPCTP@Au) were fabricated with sensitive SERS activity. The MPCTP particles were generated by coating polyphosphazene on Fe3O4 nanoparticles through precipitation polycondensation of hexachlorocyclotriphosphazene and phloroglucinol. MPCTP@Au composite particles were obtained by deposition of Au nanoparticles on MPCTP by the reduction of HAuCl4. The size and the thickness of the Au shell can be controlled by varying the amount of HAuCl4. The magnetic core endowed the composite particles with good magnetic responsiveness, which allowed the analyte to be enriched and separated from the complex matrix, and significantly simplifying the sample pretreatment procedure. The SERS activity of MPCTP@Au composite particles were evaluated by DTNB as model Raman reporter, and the limits of detection (LOD) of DTNB was 10-8 mol/L. A high efficient SERS immunoassay system based on the MPCTP@Au substrates for the detection of immunoproteins was developed. Human IgG and rabbit IgG were quantitatively determinated simultaneously by this immunoassay system. The quantitative determination of the immunoglobulin G (IgG) was achieved and the LOD of human IgG, rabbit IgG and the mixture of human IgG and rabbit IgG were as low as 10 fg/mL, 100 pg/mL and 1 ng/mL, respectively. The results showed that the MPCTP@Au composite particles have broad application prospects as high performance SERS active substrates for immunoprotein analysis.

Classification and geographic origin discrimination of Chinese prickly ash using X-ray fluorescence and machine learning

Chinese prickly ash (CPA) is a widely used seasoning with numb taste and a traditional Chinese medicine. Discrepancies among cultivating regions may pose a direct impact on the elemental contents, and ultimately on the flavor and quality of CPA. This study explored the elemental composition of CPAs by X-ray fluorescence spectrometry (XRF). Combined with chemometric methods such as principal component analysis, linear discriminant analysis, k-nearest neighbor, partial least squares discriminant analysis, support vector machine and random forest, the classification and discrimination of CPAs from different cultivation regions were realized with high accuracy. Taking advantage of XRF for direct non-destructive analysis, sample digestion essential in common analytical atomic spectrometry was omitted, which significantly simplified the sample pretreatment procedure and retained matrix components that are probably indicative of the geographic origins as well. The top ten important elements for discrimination were K, Sr, C, Ca, P, S, Fe, O, Mg and Si based on the importance score of random forest. The proposed strategy has been demonstrated as a simple, rapid yet efficient method for CPA classification, and may be applied to other food and medicinal samples.

Simultaneous Quantification of Some Fluoroquinolone Residues in Real Wastewater Effluents Using CZE

Since active pharmaceutical ingredients (APIs) are directly related to human health, monitoring and quantifying them in the environment is a crucial and challenging issue. Using capillary-zone electrophoresis (CZE), four frequently used fluoroquinolones (FQs), ciprofloxacin, sparfloxacin, moxifloxacin, and gatifloxacin, were efficiently isolated and measured in pharmaceutical industrial wastewater. Solid-phase extraction (SPE) was developed and used as an efficient sample pretreatment procedure. The capillary electrophoretic procedure’s various parameters were tuned to produce the optimal separation pattern for the drugs under consideration. All of the drugs under study were quantified in a concentration range of 0.5 to 50 µg/mL. After full assay validation in compliance with ICH-Q2B criteria, real wastewater samples were subjected to effective SPE, and the proposed assay was successfully used to determine the examined FQs in real wastewater samples.

Coconut shell biochar application in liquid-solid microextraction of triazine herbicides from multi-media environmental samples

A rapid, fast, widely applicable liquid-solid microextraction and purification method of triazine herbicides (TRZHs) in muti-media samples using salting-out assisted liquid-liquid extraction (SALLE) combined with self-assembled monolithic spin columns-solid phase micro extraction (MSC-SPME) was developed. Environmentally friendly coconut shell biochar (CSB) was used as the adsorbents of MSC-SPME. Ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was the separation and determination method. The adsorption kinetics and isotherms were investigated to indicate the interaction between CSB and TRZHs. Several parameters influencing the liquid-solid microextraction efficiency, such as sample pH, salting-out solution volume and pH, sample loading speed, elution speed, elution ratio and volume of eluent were systematically investigated with the aid of orthogonal design. The whole extraction process was operated within 10 min. Under the optimum extraction and determination conditions, good linearities for three TRZHs were obtained in a range of 0.10–200.00 ng mL−1, with linear coefficients (R2) greater than 0.999. The limits of detection (LODs) and limits of quantification (LOQs) were in the range of 6.99–11.00 ng L−1 and 23.33–36.68 ng L−1, respectively. The recoveries of the three TRZHs in multi-media environmental samples were ranged from 69.00% to 124.72%, with relative standard deviations (RSDs) lower than 0.43%. This SALLE-MSC-SPME-UPLC-MS/MS method was successfully applied to the determination of TRZHs in environmental and food samples and exhibited the advantages of high efficiency and sensitivity, low cost, and environmental friendliness. Compared with the methods published before, CSB-MSC was green, rapid, easy-operated, and reduced the whole cost of the experiment; SALLE combined MSC-SPME eliminated the matrix references effectively; what's more, the SALLE-MSC-SPME-UPLC-MS/MS method could be applied to various sample without complicated sample pretreatment procedure.

How Saliva Interferes with Colorimetric Gold Nanoparticle Aptasensors: Understanding and Mitigating Surface Interactions

Colorimetric gold-nanoparticle-based biosensors are an attractive platform for the detection of small-molecule analytes. Taking advantage of the adsorption of DNA aptamer probes on AuNPs, these sensors can be simple, rapid, sensitive, selective, and cost-effective. These properties are important for rapid detection of drugs like methamphetamine in biological matrices. Saliva is a highly desirable matrix for development of diagnostic tests because saliva sampling is minimally invasive and drug levels relate to recent use rather than accumulation from historical use. However, saliva is a complex fluid that presents a multitude of challenges when applying colorimetric aggregation assays. Here, we show that the contents of saliva interfere with the sensor in two main ways: (i) suppressing color change signals due to proteins nonspecifically adsorbing to nanoparticles and (ii) blocking aggregation and generating false signals due to specific electrolytes that induce aggregation. With this knowledge, we examine strategies to mitigate these effects, including sample collection and pretreatment procedures. These measures ultimately result in a sensor that can detect methamphetamine spiked into saliva samples and suggest immense promise for the feasibility of these platforms for on-site diagnostic applications.

Construction of CdTe@γ-CD@RBD nanoprobe for Fe3+-sensing based on FRET mechanism in human serum

A Fe3+ optical sensor (CdTe@γ-CD@RBD) has been developed by using gamma-cyclodextrin (γ-CD) as a bridge to link CdTe quantum dots (QDs) and a Rhodamine B derivative (RBD). The RBD molecule can enter the cavity of the γ-CD anchored onto the surfaces of the QDs. In the presence of Fe3+, the fluorescence resonance energy transfer (FRET) process from QDs to RBD will be initiated, rendering the nanoprobe to display a response to Fe3+. The degree of fluorescence quenching presented a satisfactory linearity between 10 and 60 μΜ with the incremental concentrations of Fe3+, and the calculated limit of detection was 2.51 μΜ. Through sample pretreatment procedures, the probe has been used in the determination of Fe3+ in human serum. The average recoveries in the spiking levels are ranged from 98.60 % to 107.20 % with a relative standard deviation of around 1.43 %-2.96 %. This finding leads to a method for fluorescent detection of Fe3+ with high sensitivity and exceptional selectivity. We believe that this study can give a new insight into the rational design and application of FRET-based nanoprobes.