LOD) And Quantification Research Articles

Determination of trace anions in battery-grade lithium carbonate by double-inhibition on-line matrix-removal ion chromatography

A method was developed for the determination of trace anions in battery-grade lithium carbonate. In this method, lithium carbonate was dissolved in ultrapure water with ultrasound assistance, and its matrix was removed using an on-line matrix-removal method. In the matrix-removal process, the sample was first passed through an ADRS600(4 mm) suppressor (suppressor current, 150 mA; external water flow rate, 2 mL/min). Hydrogen and lithium ions were then completely exchanged via the ion-exchange membrane in the suppressor, converting the lithium carbonate into carbonic acid. The carbonic acid entered the waste-liquid channel in the form of carbon dioxide through a CRD 200(4 mm) carbonate removal device to remove the lithium carbonate matrix. Finally, the target anions were automatically enriched on an IonPac UTAC-LP2 concentration column (35 mm×3 mm) and automatically transferred to a chromatographic system using valve-switching technology. The chromatographic system featured an IonPac AG18 column (50 mm×2 mm) as the protection column and an IonPac AS18 column (250 mm×2 mm) as the analytical column. The column temperature was 30 ℃, gradient elution was performed using KOH solution as the eluent, and the pump flow rate was 0.30 mL/min. An ADRS600(2 mm) suppressor, suppressor current of 25 mA, injection volume of 250 μL, and conductance detector were also used. The results showed good linear relationships (r≥ 0.999) for F-, Cl-, [Formula: see text] in their respective concentration ranges. The limits of detection (LODs) and quantification (LOQs) were 0.05-0.88 and 0.15-2.92 μg/L, respectively. Lithium carbonate samples were tested six consecutive times, and the relative standard deviations (RSDs) of the peak areas of each ion were less than 0.73%. The same lithium carbonate samples were injected after 0, 2, 4, 8, 12, 18, and 24 h, and the RSD of the peak areas of each ion was less than 0.96%. The average recoveries ranged from 93.3% to 99.3%, and the RSDs (n=6) of samples spiked at three levels were in the range of 0.97%-3.45%. The proposed method has a low method limit of quantification of only 0.5 mg/kg for each ion analyzed and is capable of the simultaneous analysis of multiple ions. Thus, it is suitable for the detection of trace anions in battery-grade lithium carbonate.

Determination of 35 prohibited pesticide residues in Saussurea costus by modified QuEChERS method based on multi-walled carbon nanotubes coupled with gas chromatography-tandem mass spectrometry

Saussurea costus, a perennial herb belonging to the Asteraceae family, is a vital ingredient in traditional Chinese medicine. Increased demands for the herb have led to its widespread cultivation in China, but the corresponding increase in pesticide use has raised concerns about pesticide residues. Such residues would affect the safety and global market potential of Saussurea costus. Thus, a simple method is crucial to detect pesticide residues. The QuEChERS technique, in combination with gas chromatography-tandem mass spectrometry (GC-MS/MS), is commonly used for residue detection. However, traditional adsorbents may be unable to purify complex herbal mixtures well, affecting accuracy and instrument performance. Choosing suitable purification materials for Saussurea costus samples with complex matrices is of significant importance. This study focused on the detection of 35 prohibited pesticides in Saussurea costus. A rapid detection method was established by combining the QuEChERS technique with GC-MS/MS and utilizing a combination of multiwalled carbon nanotubes (MWCNTs), octadecylsilane-bonded silica gel (C18), and anhydrous magnesium sulfate (MgSO4) as the purification adsorbent. The samples were extracted with acetonitrile, purified by an improved QuEChERS process, subjected to GC-MS/MS analysis in multiple reaction monitoring (MRM) mode, and quantified using the internal standard method. The purification effects of four materials (C18, MWCNTs, N-propyl ethylenediamine (PSA), and graphitized carbon black (GCB)) and their optimal dosages were investigated by considering the matrix characteristics of the samples. An orthogonal experimental design was employed to optimize the ratio of adsorbent combinations, and the optimal adsorbent combination was determined to be 450 mg of MgSO4, 400 mg of C18, and 50 mg of MWCNTs. Matrix effect (ME) evaluation of the S. costus matrix showed that 31 target compounds strongly exhibited matrix-enhancement effects. Thus, matrix-matched calibration was employed in this study. Methodological investigation revealed that the standard curves for the 35 pesticides exhibited good linearity, with correlation coefficients (r2) greater than 0.9970. The average recoveries at three spiked levels ranged from 69.6% to 126.9%, and the relative standard deviations (RSDs) for parallel groups were all less than 10%. The limits of detection (LODs) and quantification (LOQs) ranged from 0.2 to 5.4 μg/kg and from 0.6 to 18.1 μg/kg, respectively. The developed method was used to screen and detect 35 pesticide residues in 20 batches of S. costus samples, and the target compounds were detected in six batches. The proposed method is simple, sensitive, and accurate. Thus, it is suitable for the rapid screening and detection of the 35 pesticide residues in S. costus and provides technical support for the cultivation, production, and quality control of the herb.

Fabrication of chitosan nanoparticles for the determination of phenylisatin and its analytical application in biological sample

The synthesis of 1Phenylisatin (Ph) incorporated chitosan nanoparticles (Ph CSNPs) was done utilizing the conventional sol–gel method. For the characterization of CSNPs and Ph CSNPs, different techniques like FTIR, SEM, XRD and TEM were utilized. The Ph CSNPs and the pure Ph were interacted with bovine serum albumin (BSA). The results of fluorescence quenching confirm that both the systems are static in nature. The decreased Ksv value for the nanoparticles confirms the increased remedial efficiency of the Ph CSNPs and therefore the synthesized CSNPs can be used as a drug delivery system. The developed fluorescence-based method also reports the quantification and detection limit values for the Ph molecule. The linear dynamic range after the optimization of experimental conditions was found to be 2.91–6.54 µg mL−1. The values of limit of detection (LOD) and quantification (LOQ) for pure Ph system are 0.462 µg mL−1 and 1.54 µg mL−1 respectively, while for the Ph CSNPs system the values are 0.560 µg mL−1 (LOD) and 1.86 µg mL−1 (LOQ). These values were reported with high correlation coefficient values.

Determination of seven perfluoroalkyl and polyfluoroalkyl substances in serum of pregnant women and evaluation of neonatal neurobehavior based on high performance liquid chromatography-tandem mass spectrometry

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) have been extensively used as synthetic fluorine-containing compounds in various consumer products, including surfactants, cookware, lubricants, clothing, and food packaging, since the 1950s. Evidence has shown that PFASs cross the placental barrier and interfere with fetal thyroid hormone homeostasis, which is crucial for fetal growth and neurobehavioral development in children aged 2-9 years. However, no epidemiological data on the association between prenatal PFAS exposure and neonatal neurobehavioral development are available. In this study, we explored the association between prenatal PFAS exposure and neonatal neurobehavioral development based on the Ezhou cohort study. Blood samples (10 mL) were collected during the third trimester of pregnancy (28-36 weeks) at the Ezhou maternal and child health hospital. The blood specimens were centrifuged at 4000 r/min for 15 min immediately after collection, separated, stored at -80 ℃. The samples were analyzed for seven PFASs, namely, perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroheptanesulfonic acid (PFHpS), and perfluorooctane sulfonamide (PFOSA). The PFASs were separated using a C18 column (100 mm×2.1 mm, 1.7 μm) at an oven temperature of 40 ℃, injection volume of 10 μL, and flow rate of 0.4 mL/min via gradient elution with methanol and ammonium acetate aqueous solution. The instrument was operated in negative electrospray ionization mode with multiple reaction monitoring. The correlation coefficients (r2), limits of detection (LODs) and quantification (LOQs), and spiked recoveries of the seven PFASs were 0.993-0.999, 0.006-0.020 ng/mL, 0.020-0.066 ng/mL, and 84.6%-116.8%, respectively. Neonatal behavioral neurological assessment (NBNA) was used to evaluate newborn cognitive development 72 h after birth; this tool consisted of five clusters, including behavior (six items), passive muscle tone (four items), active muscle tone (four items), primitive reflexes (three items), and general assessment (three items). Each item was rated on a three-point scale (0, 1, or 2), with the 20 items having a maximum score of 40. A total of 379 mother-newborn pairs were included in the analysis. The PFASs with the highest exposure levels was PFOA, with median levels of 19.4 ng/mL. Linear regression models were used to test the effects of ln-converted PFAS levels in newborns. After adjusting for confounding factors, the linear regression model showed that PFOS exposure during pregnancy was associated with decreased active muscle tone(β(95% CI): 0.36(-0.64, 0.08)) and general assessment(β(95% CI): 0.34(-0.61, 0.07)) in all newborns. Furthermore, PFNA exposure was associated with decreased passive muscle tone(β(95% CI): 0.38(-0.74, 0.01)) and total NBNA(β(95% CI): 0.37(-0.68, 0.06)). PFDA exposure was associated with decreased behavior(β(95% CI): 0.28(-0.54, 0.01)), while PFHxS exposure was associated with elevated total NBNA(β(95% CI): 0.27(0.05-0.48)). Gender stratification analysis showed that PFOS exposure during pregnancy was associated with decreased active muscle tone(β(95% CI): 0.54(-0.73, 0.35)) and general assessment(β(95% CI): 0.50(-0.88, 0.13)), PFNA exposure during pregnancy was associated with decreased passive muscle tone(β(95% CI): 0.67(-1.2, 0.14)) and total NBNA(β(95% CI): 0.45(-0.91, 0.01)), PFDA exposure during pregnancy was associated with decreased behavior(β(95% CI): 0.44(-0.71, 0.17)), PFHxS exposure was associated with elevated total NBNA(β(95% CI): 0.41(0.02-0.80)) in male newborns, and PFOA exposure was associated with decreased general assessment(β(95% CI): -0.27(-0.51, 0.02)), and PFDA exposure was associated with elevated behavior(β(95% CI): 0.46(0.40-0.52)) in female newborns. The proposed method separates and detects various PFASs without the need for cumbersome pretreatment processes, and has the advantages of low LODs, satisfactory recoveries, and accurate precision. Thus, it allows for the simultaneous analysis of trace PFASs in microserum samples from pregnant women. Our results also showed that prenatal PFAS exposure can lead to neurobehavioral disorders in offspring, with male newborns showing greater sensitivity than female newborns.

Modification of sensitive pyridine-pyrazolone method for determination of blood cyanide and its possible applications in fatal aircraft accidents

BackgroundFatal aviation accidents are a critical concern for armed forces, necessitating precise toxicological analysis of postmortem blood samples. This paper introduces a novel spectrophotometric method for quantifying cyanide in blood samples with an aim to aid in aircraft accident reconstruction in the future. MethodsBlood samples were collected from healthy non-smokers aged 20–45 years, excluding individuals with hepatic impairment, or those using drugs affecting blood cyanide levels. The spectrophotometric method involved cyanide adsorption in a sodium hydroxide solution using microdiffusion discs and chemical reactions resulting in a pinkish-purple end product. The optimal absorption wavelength (λmax) was determined, and the lower limits of detection and quantitation were established. The method underwent validation for precision, sensitivity, specificity, linearity, and accuracy. ResultsThe procedure yielded a pinkish-purple compound with an optimal absorption wavelength (λmax) of 531 nm. The established limits of detection (LoD) and quantitation (LoQ) were 0.0625 μg/ml and 0.125 μg/ml, respectively. The method demonstrated strong linearity up to cyanide concentrations of 4 μg/ml. It exhibited a sensitivity of 99.7% and accuracy of 85.92%. The intraday and inter-day precision were determined as 9.04% and 4.27%, respectively. The method was highly specific, showing no interference with blanks at the peak wavelength with a working range of 0.125–4 μg/ml. ConclusionThe study describes developing and validating a sensitive method for quantitatively estimating cyanide in blood samples. Incorporating this method into the existing postmortem toxicological sample collection and investigation protocol will enhance the analysis capabilities and improve aircraft accident investigation outcomes within the country.

Method Development and Optimization of Liquid-Liquid Microextraction Based on the Decomposition of Deep Eutectic Solvent for the Determination of Chromium (VI) in Spinach: Assessment of the Greenness Profile Using Eco-scale, AGREE, and AGREEprep

A simple, effective, and ligandless liquid-liquid microextraction (LLME) procedure based on the decomposition of hydrophobic deep eutectic solvents (HDES) was developed for the separation and pre-concentration of chromium (VI) ions in spinach leaves, before the determination by flame atomic absorption spectrophotometry. In the proposed study, the first stage involved the leaching of chromium (VI) from spinach leaves with 0.1 M Na2CO3, and in the second stage, chromium (VI) extract was preconcentrated with the LLME procedure using a DES prepared from the combination of DL-menthol and formic acid as a chelating agent and extraction solvent. The DES decomposed in an aqueous donor phase resulting in the dispersion of menthol and extraction of Cr (VI) ions. Under optimal experimental conditions, the limits of detection (LOD) and quantification (LOQ) were 0.63 and 2.1 µg L−1, respectively. The relative standard deviation (RSD) was less than 7%, and the pre-concentration factor (PF) was found to be 31.25. The accuracy of the present methodology was tested by recovery experiments. The greenness of the developed method was assessed using three quantitative green metrics tools: Analytical Eco-scale, AGREE, and AGREEprep, with only Analytical Eco-scale qualifying the proposed method as green.

A Ratiometric Biosensor Containing Manganese Dioxide Nanosheets and Nitrogen-Doped Quantum Dots for 2,4-Dichlorophenoxyacetic Acid Monitoring.

Nanomaterials are desirable for sensing applications. Therefore, MnO2 nanosheets and nitrogen-doped carbon dots (NCDs) were used to construct a ratiometric biosensor for quantification of 2,4-dichlorophenoxyacetic acid. The MnO2 nanosheets drove the oxidation of colorless o-phenylenediamine to OPDox, which exhibits fluorescence emission peaks at 556 nm. The fluorescence of OPDox was efficiently quenched and the NCDs were recovered as the ascorbic acid produced by the hydrolyzed alkaline phosphatase (ALP) substrate increased. Owing to the selective inhibition of ALP activity by 2,4-D and the inner filter effect, the fluorescence intensity of the NCDs at 430 nm was suppressed, whereas that at 556 nm was maintained. The fluorescence intensity ratio was used for quantitative detection. The linear equation was F = 0.138 + 3.863·C 2,4-D (correlation coefficient R2 = 0.9904), whereas the limits of detection (LOD) and quantification (LOQ) were 0.013 and 0.040 μg/mL. The method was successfully employed for the determination of 2,4-D in different vegetables with recoveries of 79%~105%. The fluorescent color change in the 2,4-D sensing system can also be captured by a smartphone to achieve colorimetric detection by homemade portable test kit.

Preparation of deep-eutectic solvent and study on the detecting methods of crystal violet by deep-eutectic solvent

This paper prepared deep eutectic solvent using choline chloride (hydrogen bond acceptor) and phenol (hydrogen bond donor) as raw materials in molar ratio of 1:3. The prepared DES showed hydrophobic properties, sodium carboxymethyl cellulose was used as an emulsifier to pretreat crystal violet (CV), and the prepared DES was used as an excellent extractant to extract CV for detection. Ultraviolet spectrophotometry was used to determine the absorbance of CV after extraction to calculate the corresponding extraction concentration. In addition, the influences of external influencing factors, such as appropriate extractant and emulsifier, required centrifugation time, and proper pH on the experimental results were also explored. Under the optimized conditions, the detected content of CV (pH = 4, centrifugation time 10 min) showed good linear relationship in the range of 5∼40 mg/L, the limit of detection (LOD) and quantification (LOQ) were 1.01 μg/L and 1.53 μg/L. The proposed method was applied to blue frame label paper and blue ball ink commonly used in the laboratory as the determination method of marking experiments. As a result, the recovery rates obtained were more than 80 %, confirming the feasibility of the proposed method.

The High-Precision Liquid Chromatography with Electrochemical Detection (HPLC-ECD) for Monoamines Neurotransmitters and Their Metabolites: A Review.

This review highlights the advantages of high-precision liquid chromatography with an electrochemical detector (HPLC-ECD) in detecting and quantifying biological samples obtained through intracerebral microdialysis, specifically the serotonergic and dopaminergic systems: Serotonin (5-HT), 5-hydroxyindolacetic acid (5-HIAA), 3,4-dihydroxyphenylacetic acid (DOPAC), dopamine (DA), 3-metoxytryptamin (3-MT) and homovanillic acid (HVA). Recognized for its speed and selectivity, HPLC enables direct analysis of intracerebral microdialysis samples without complex derivatization. Various chromatographic methods, including reverse phase (RP), are explored for neurotransmitters (NTs) and metabolites separation. Electrochemical detector (ECD), particularly with glassy carbon (GC) electrodes, is emphasized for its simplicity and sensitivity, aimed at enhancing reproducibility through optimization strategies such as modified electrode materials. This paper underscores the determination of limits of detection (LOD) and quantification (LOQ) and the linear range (L.R.) showcasing the potential for real-time monitoring of compounds concentrations. A non-exhaustive compilation of literature values for LOD, LOQ, and L.R. from recent publications is included.

A Validated RP-HPLC Method for Simultaneous Quantification of Abacavir and Zidovudine and their Impurities in Combined Dosage Forms

Develop a simple, accurate, and precise method for simultaneous analysis of Abacavir and Zidovudine, along with their related impurities, in combined pharmaceutical dosage forms. A reverse- phase high-performance liquid chromatography (RP-HPLC) method was developed using an LC-20 AT C18 column and a Water: Methanol (80:20) mobile phase. Detection was carried out at 240 nm. The method successfully separated Abacavir, Zidovudine, and their respective impurities with distinct retention times. Validation demonstrated good linearity, accuracy, and precision for both drugs and their impurities. Limits of detection (LOD) and quantification (LOQ) were determined and found to be suitable for analyzing impurities in commercial dosage forms. The developed RP-HPLC method offers a simple, accurate, and reliable tool for simultaneous quantification of Abacavir, Zidovudine, and their impurities in combined dosage forms, thereby contributing to quality control and ensuring drug safety. Keywords Abacavir, Zidovudine, Related Substance RP-HPLC Method, ICH Q2 (R1) guidelines

A simple and effective graphene oxide-zinc oxide nanocomposite based solid phase extraction method for the determination of cadmium in tea matrix at trace levels by flame atomic absorption spectrophotometry

In this study, an easy, environmentally friendly and fast approach was introduced for the synthesis of GO-ZnO nanocomposite (NC). Characterization tools including X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) were used to verify the synthesized nanomaterial. Afterward, the combination of GO-ZnO NC based dispersive solid phase microextraction (dSPME) and flame atomic absorption spectrophotometry (FAAS) was used to preconcentrate and determine Cd with high precision and accuracy. In the optimization experiments, all parameters that affecting extraction yield were optimized. Limit of quantification (LOQ) and detection (LOD) values for the GO-ZnO NC-dSPME-FAAS system were calculated as 12.76 µg L−1 and 3.83 µg L−1, respectively. In order to check the applicability and accuracy of the developed method, recovery experiments were performed on three different hibiscus tea samples. The percent recovery values calculated from the spike experiments were in the range of 84 – 111%.

A simple and green ion-pairing extraction colorimetric determination of chlorhexidine employing coconut oil as a natural solvent with image processing

A cost-effective, simple, and green determination of chlorhexidine is proposed. A commonly available bromothymol blue serves as a reagent. The ion-pairing of chlorhexidine and bromothymol blue in an aqueous solution can be extracted into an organic phase of coconut oil, which is proposed as an alternative natural green solvent, replacing the conventional toxic organic solvents. An investigation of the chlorhexidine-bromothymol blue ion pair was made spectrophotometrically and via image processing using a smartphone camera. Downscaling is operated for the extraction of 500 μL of an aqueous mixture containing chlorhexidine and bromothymol blue in phosphate buffer (pH 7.5, 5 mmol/L) with 500 μL of coconut oil for 3 min by hand-shaking. A set of 12 extraction tubes can be operated in one run. After phase separation by centrifuging (3000 rpm, 3 min), the 12 tubes are photographed in one shot using a smartphone. Images of both aqueous and organic phases are evaluated for red-green-blue (RGB) color intensity system. Linearity equations: R intensity = 1.205 [Chlorhexidine] – 23.6 (r2: 0.9795), and ΔB intensity = 1.525 [Chlorhexidine] – 36.75 (r2: 0.9907), are obtained for aqueous and organic phases, respectively. The limits of detection (LOD) and quantitation (LOQ) were 12 and 40 mg/L for aqueous, while 11 and 34 mg/L for organic phases, respectively. The proposed procedure was applied to real samples of active pharmaceutical ingredients (API), disinfectant cleaner, and mouthwash. The results obtained by the proposed procedure agree with the high-performance liquid chromatography (HPLC) reference method that utilizes a UV detector. In evaluations using the green analytical procedure index (GAPI) and analytical greenness (AGREE), the proposed procedure was found to be the greenest compared to the conventional spectrophotometric method and HPLC. The proposed procedure involved the UN-SDGs #3, #4, and #12 and scored the highest value of the need, quality, and sustainability (NQS) index. The proposed procedure encourages sustainable chemistry and pharmacy.

Development of a QuEChERS-HPLC-FLD Procedure for the Simultaneous Detection of Residues of Florfenicol, Its Metabolite Florfenicol Amine, and Three Fluoroquinolones in Eggs.

A method utilizing high-performance liquid chromatography-fluorescence detection (HPLC-FLD) has been developed and refined for the simultaneous detection of florfenicol (FF) and its metabolite florfenicol amine (FFA) along with three fluoroquinolone (ciprofloxacin (CIP), enrofloxacin (ENR), and sarafloxacin (SAR)) residues in different parts of eggs (whole egg, egg yolk, and egg albumen). The QuEChERS ("Quick, easy, cheap, effective, rugged, and safe") procedure utilized 0.1 M disodium EDTA solution, water, and acetonitrile as extractants; sodium sulfate, sodium chloride, and trisodium citrate as dehydrating salts; and N-propylethylenediamine and C18 as adsorbents. A dual-channel FLD method was utilized to analyze the target compounds using an XBridge BEH C18 chromatographic column (4.6 mm × 150 mm, 5 μm). The mobile phase was employed isocratically using a solution of 0.01 M sodium dihydrogen phosphate, 0.005 M sodium dodecyl sulfate, and 0.1% triethylamine (pH 4.8) in combination with acetonitrile at a ratio of 65:35 (V/V). The limits of detection (LOD) and quantification (LOQ) of the analytes ranged from 0.03 to 1.5 µg/kg and from 0.1 to 5.0 µg/kg, respectively. The recoveries of the analytes in the blank egg samples ranged from 71.9% to 94.8% when reference standard concentrations of the LOQ, half of the maximum residual limit (MRL), MRL, and twice the MRL were added. The parameters of the presented protocol were validated and subsequently applied to the analysis of real samples, demonstrating the applicability and reliability of the method.

Rapid determination of 87 prohibited ingredients in cosmetics by ultra performance liquid chromatography-tandem mass spectrometry

The methods of detecting numerous prohibited components are not included in the Technical Specifications for Cosmetic Safety (2015 Edition). Recently, owing to its high speed, sensitivity, and anti-interference properties, ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) became the preferred method of detecting banned substances in cosmetics. In this study, a UPLC-MS/MS method was developed for use in determining 87 prohibited ingredients in cosmetics, including 33 sex hormones, 20 anti-infective drugs, 15 antihistamines, 7 coumarins, 4 sedative-hypnotic drugs, 4 antipyretic and analgesic drugs, 2 allergenic fragrances, and 2 drugs with vasoconstriction effects. The main factors affecting the response, recovery, and sensitivity of the method, such as the type of extraction solvent, extraction time, ratio of the mobile phases, and MS conditions, were optimized during sample pretreatment and instrumental analysis. Accordingly, approximately 0.2 g of the toner or cream sample was dispersed in 2 mL acetonitrile in a 10 mL colorimetric tube. After diluting to 10 mL with 50% acetonitrile aqueous solution, the sample was ultrasonically extracted for 20 min and centrifuged, and the mixture was then filtered through a 0.22 μm membrane. Approximately 0.2 g of the oil sample was dispersed in 2 mL n-hexane in a 15 mL polypropylene centrifuge tube and extracted twice with 3 mL 70% acetonitrile aqueous solution. The extracts were transferred into a 10 mL colorimetric tube and diluted to 10 mL with 50% acetonitrile aqueous solution, and the mixture was then filtered through a 0.22 μm membrane. The samples were separated using a CORTECS C18 column (150 mm×2.1 mm, 2.7 μm), employing a gradient elution program with acetonitrile and 0.1% formic acid aqueous solution as the mobile phases. The flow rate, column temperature, and injection volume were respectively set at 0.3 mL/min, 40 ℃, and 2 μL. The 87 compounds were monitored in multiple reaction monitoring (MRM) mode with electrospray ionization (ESI) under positive and negative conditions. Matrix-matched external standard calibration was used for quantification, and the analysis was completed within 33 min. The prohibited compounds exhibited good linear relationships, with r values of >0.99, and the limits of detection (LODs) and quantification (LOQs) for the 87 compounds were 0.07-0.38 and 0.21-1.15 μg/g, respectively. Three types of cosmetic matrices were selected to verify the recovery and precision of the method at LOQ, 2 LOQ, and 10 LOQ levels. The average recoveries of the 87 prohibited compounds were in the range of 81.7%-115.4%, and the relative standard deviations (RSDs, n=6) were 0.4%-9.9%. The reliability of the developed method was demonstrated by applying it to 349 commercial cosmetics obtained from the market, and 8 positive samples were identified. The positive components included trimethoprim, terbinafine, naphazoline, 7-methoxycoumarin, and 7-methylcoumarin. The established method displays the advantages of simple operation and rapidness and a high sensitivity and good recovery. And, this method provides technical support for rapid risk screening and the revision of national standards for cosmetics.

Analytical Validation Study with Uncertainty Evaluation of the Method for Quantitative Determination of Hesperidin in the Extracted Product and Mandarin Processing Waste

The aim of this study was to develop and validate an alternative, selective, reproducible, and high-yield extraction-based method by ultrasound-assisted technique combined with an effective, specific, sensitive, and rapid analytical HPLC procedure for obtaining hesperidin from mandarin (Citrus unshiu) peel as waste material in citrus processing industries and its quantitative determination in the obtained extracted product and citrus waste materials as well. The evaluation of the uncertainty of the developed method is also described in the present work. The proposed method is focused not only on obtaining hesperidin but also provides the possibility for obtaining other valuable bioactive compounds within the single stepwise extraction process. The proposed method was validated concerning the following validation parameters: robustness, system suitability test, specificity, linearity range, precision, accuracy, sensitivity, limits of quantification (LOQ), and detection (LOD). A design of experiments using the Placket-Burman approach was used for the robustness study of the combined method. The measurement uncertainty of the proposed method was evaluated based on the four-step process using a combination of two appropriate - bottom-up and top-down approaches using the method validation data. The LOD and LOQ of the analytical procedure were 0.00001 mg/mL and 0.000025 mg/mL, respectively. The calibration curve (0.000025-0.5 mg/mL) is linear and the square of the correlation coefficient is equal to 0.99992. The determined average amount of hesperidin in the dry citrus peel samples is equal to 35.36 ± 3.14 mg/g (k=2, 95 % level of confidence). The mean recovery of the combined method is 91.48 %. The purity of the dry-extracted product of hesperidin is not less than 90 %.

Cloud point method applied to the extraction and preconcentration of thiabendazole pesticide from whole grape juice samples and amperometric detection by HPLC.

A cloud point method was developed and applied for the first time to extract and preconcentrate thiabendazole (TBZ) from commercial whole grape juice samples, with determination by high performance liquid chromatography coupled to electrochemical detection (HPLC/EC), using a cathodically pretreated boron-doped diamond electrode (BDD). The best conditions for extraction and preconcentration of TBZ by cloud point extraction (CPE) were performed at pH 6.0, by adding 1 mL of the surfactant Tergitol TMN-6 at 10% (mass-to-mass ratio), without heating (at 27 °C) and ultrasonic stirring time of (20 kHz) for 60 min. The HPLC/EC determination was duly validated in a C8 column, in mobile phase with a 69 : 31 ratio (V/V) of phosphate buffer (pH 7.0):ACN, at a flow rate of 1.2 mL min-1 and electrochemical detection with BDD electrode by applying 1.40 V × Ag/AgCl (3.0 mol L-1). Under these conditions, the procedure showed a preconcentration factor (FC) of 21.7, and limits of detection (LOD) and quantification (LOQ) of 6.64 × 10-9 mol L-1 (or 1.33 μg L-1) and 1.66 × 10-8 mol L-1 (or 3.34 μg L-1), respectively. The method provided a percent recovery of 81% to 98%, with a coefficient of variation between 3% and 15%.

Improved matrix purification using a graphene oxide-coated melamine sponge for UPLC-MS/MS-based determination of 37 veterinary drugs in milks.

A rapid and highly sensitive method was established for the analysis of 37 veterinary drug residues in milk using a modified QuEChERS method based on a reduced graphene oxide-coated melamine sponge (rGO@MeS) coupled with UPLC-MS/MS. Under optimal chromatographic and mass spectrometric conditions, the effects of different dehydrated salts (MgSO4 and Na2SO4) and metal chelating agents (Na2EDTA) on extraction efficiency were first investigated. Next, the influence of a dynamic and static purification mode was evaluated in terms of drug recoveries. Calibration curves of 37 veterinary drugs were constructed in the range 0.6-500 μg kg-1, and good linearities were obtained with all determination coefficients (R2) ≥0.992. The limits of detection (LODs) and quantitation (LOQs) were in the range 0.3-1.1 μg kg-1 and 0.6-3.5 μg kg-1, respectively. The recoveries of all compounds were in the range 61.3-118.2% at three spiked levels (20, 100, and 200 μg kg-1) with RSDs ≤15.4% for both intra- and inter-day precisions. Compared to pristine melamine sponges and commercial adsorbents (C18, PSA, and GCB), rGO@MeS demonstrated an equal or even better purification performance in terms of recoveries, matrix effects, and matrix removal efficiency. This method is rapid, simple, efficient, and appropriate for the qualitative and quantitative analyses of 37 veterinary drug residues in milk, providing a new detection strategy and technical support for the routine analysis of animal-derived food.

The determination of underivatized chlormequat, fosetyl-aluminium and phosphonic acid residues in maize and soybean by LC-MS/MS.

In this study, a simple, rapid and sensitive method was developed for the simultaneous determination of chlormequat, fosetyl-aluminium and phosphonic acid residues in maize and soybean using liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS). Analytes were extracted with acetic acid solution, purified on an HLB column, and then filtered through a 0.2 μm hydrophilic microporous filter membrane. They were then separated on an IC column using a separation phase consisting of polyvinyl alcohol particles with quaternary ammonium groups. The mobile phase optimised with water was denoted as mobile phase A and that optimised with 200 mmol L-1 ammonium bicarbonate solution containing 0.05% ammonium hydroxide was denoted as mobile phase B. The residues were detected by tandem mass spectrometry with negative electrospray ionization in a multi-reaction monitoring mode. The correlation coefficient (R ≥ 0.997) showed good linear regressions for all analytes in water as well as in maize and soybean matrices with a wide dynamic range of 0.001 to 0.5 mg L-1 for calibration. The mean recoveries (RSDs) of the analytes were in the range 85.0-106.4% (5.5-14.9%), 81.7-109.5% (2.7-11.0%) and 74.7-104.4% (2.9-6.1%) at three concentration levels (0.05, 0.1 and 1 mg kg-1) for the interday test (n = 15). The limit of quantification (LOQ) and detection (LOD) of the method for different matrices were 0.01 and 0.003 mg kg-1, respectively. In conclusion, the established analytical approach has high sensitivity and good accuracy and precision and is suitable for monitoring chlormequat, fosetyl-aluminium and phosphonic acid residues in maize and soybean.

RP-HPLC method development and validation of Albendazole and its impurity

Oxibendazole is a type of benzimidazole that is commonly used as an antiparasitic medication for both humans and animals. However, it is also a significant impurity found in albendazole, and it is crucial to follow the ICH Q3B criteria when analysing oxibendazole impurities. Therefore, it is recommended to use a simple, fast, sensitive, and precise RP-HPLC approach to identify oxibendazole impurities in bulk and pharmaceutical formulations of albendazole.To separate the oxibendazole impurity, acetonitrile and 10 nM potassium phosphate were used as a mobile phase. Orthophosphoric acid was used to accurately adjust the pH of the mobile phase to 2.03, ensuring optimal conditions. A nucleosil C18 column (250 x 4.6 mm, 5 µm) was used for the separation process, and it effectively provided the necessary separation. The gradient elution was set at a wavelength of 235 nm and a flow rate of 1 mL/min. The analytical technique was successfully designed and validated. The AQbD technique was used to optimize the analytical conditions for the suggested methodology, and the Design Expert 13® trial version was used for the central composite design optimization of analytical conditions. The procedure's linearity was verified using a regression coefficient of 0.999 within a working range of 0.5 to 3 μg/ml. Accuracy research showed results of 99.94–100.10% at 50, 100, and 150% levels of the working concentration. The oxibendazole impurity's average retention time was found to be 6.40 minutes, with a relative standard deviation of less than 2%, indicating high accuracy. The limits of detection (LOD) and quantification (LOQ) were found to be 0.073 and 0.091 μg/ml, respectively. Following the ICH Q2(R1) criteria, other validation criteria, such as robustness, were also evaluated. In conclusion, the proposed approach is suitable for analysing albendazole and oxibendazole in bulk and pharmaceutical formulations, making it ideal for detecting oxibendazole impurities.

A simple, fast and inexpensive approach to quantify low concentrations of iron in biodiesel by voltammetry after extraction induced by microemulsion breaking.

An alternative approach to assay iron (Fe) in biodiesel by differential pulse adsorptive cathodic stripping voltammetry (DPAdCSV) is presented herein. The sample treatment involved a simple, rapid, but effective extraction of Fe from biodiesel into an aqueous phase after microemulsion (ME) breaking. Then, Fe was determined as the complex Fe(III)-PAN (1-(2-pyridylazo)-2-naphthol) on a glassy carbon electrode (GCE) in the presence of bismuth (Bi(III)). The extraction induced by microemulsion breaking (EIMB) was achieved by adding 0.80 mL of ultrapure water into a water-in-oil ME containing 7.00 mL biodiesel, 2.70 mL n-propanol and 0.30 mL of 0.25 mol L-1 HNO3 solution. No deliberate addition of surfactant was necessary to form and maintain the ME. The EIMB resulted in a 1.30 mL lower aqueous phase extract (APhEx) and an upper oily phase. DP voltammograms were recorded with a portable potentiostat, showing the potentiality of carrying out the determination out of a central laboratory. Another feature was the non-necessity of deaerating the solution to eliminate the dissolved O2. The limits of detection (LOD) and quantification (LOQ) were 1.7 μg L-1 (140 mg kg-1) and 5.5 μg L-1 (455 mg kg-1), respectively. The accuracy of the method was evaluated by recovery assays of spiked samples, by analyzing a standard reference material and by comparisons with high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS).