Instrumental Detection Limits Research Articles

Strontium monofluoride – a new molecule to measure fluorine using high-resolution continuum source flame molecular absorption spectrometry and its application for gasoline analysis

In this work, for the first time, strontium monofluoride was generated in an air-acetylene flame of a high-resolution continuum source molecular absorption spectrometer with the aim of fluorine determination via molecular absorption. The particular task was the determination of organic fluorine in gasoline/its components dissolved in xylene. Sequential measurements in the area of the most intensive absorption of the molecule were executed to select the spectral range for analysis. The acquired spectra differed from the ones from the literature, especially the emission spectra. The best and comparable sensitivity has been registered near 651 nm and 663 nm in measurements of rotations from the range of the X2Σ+ → A2Π electronic transition of the SrF molecule. Unfortunately, SrOH molecules were also spontaneously formed and absorbed radiation in the selected area. No other spectral interferences were found, except absorption by the SrBr molecule, which could have been formed in the flame despite a relatively low energy bond of 330 kJ/mol. The dependence of generation of the SrF and the SrOH molecules on the flame conditions was studied for pure solvent (xylene) and solutions of investigated samples of gasoline type. The effect of the SrOH molecule was overcome by blank subtraction or the least square background correction. The last method had to be used to overcome the SrBr effect. Due to the various combustion properties of various hydrocarbons and their different behaviour in flame, applying the simplified standard addition method became indispensable. As a source of strontium, an oil Sr standards or Sr acetylacetonate (SrAA) were investigated. The crucial benefit of SrF molecule application was the relatively good solubility (and relatively low price) of SrAA. Under the selected conditions, the characteristic concentration of fluorine was 1.9 and 2.0 mg/L, while the instrumental detection limit was 0.5 and 0.8 mg/L for the 651 and 663 nm ranges, respectively. The analytical technique enables the analysis of samples diluted to a small degree, e.g. 1:3 v:v and the best method detection limit is 1.3 mg/L. The proposed method is fast and cheap.

Optimisation of the analysis procedure of polybrominated diphenyl ethers (PBDEs) in plastic waste from household products

Polybrominated diphenyl ethers (PBDEs) are one group of flame retardants used as additives in many household products, in-cluding plastic products. Determining the residues of PBDEs in household plastic products is required to control their effects on human health and leach into the environment after disposal. This study was conducted to optimise sample preparation conditions for analysing PBDEs in plastic waste from household products. The study results are given that the instrument detection and quantification limits (IDL and IQL) ranged from 4.19 to 28.4 ppb and 14.0 to 94.8 ppb, respectively. In addition, the method detec-tion limit (MDL) and method quantification limit (MQL) were the lowest at 2.20 and 7.35 ng/g (BDE 99) and the highest at 24.1 and 80.3 ng/g (BDE 209), respectively, while the recovery val-ues for spiking samples at different concentrations ranged from 89.1 to 104.5%. The results of the method validation can confirm that the soxhlet extraction and solid phase extraction (SPE) tech-niques combined with gas chromatography mass spectrometry (GC/MS) equipment can be applied to determine the PBDEs in plastic waste samples.

A high-performance method for quantitation of aflatoxins B1, B2, G1, G2: Full validation for raisin, peanut matrices, and survey of related products at Ho Chi Minh City.

Optimization and validation for simultaneous quantitation of four aflatoxins B1, B2, G1, and G2 in peanuts and raisins were performed on ultra-performance liquid chromatography in a combination of fluorescence detector, without derivatization. The advantages were short analysis time, simple sample handling, and reduced solvent consumption. Instrument detection limits of AFB1, AFB2, AFG1, and AFG2 were 0.07, 0.01, 0.1, and 0.008 μg/kg, respectively, lower than those obtained by LCMSMS and HPLC-FLD with derivatization. Two solvent mixtures were chosen for two different matrices whose matrix effect was not negligible (2.81%-8.04% for peanuts and 5.63%-11.43% for raisins). The linear ranges were from 0.2 to 20 μg/L for AFB1 and AFG1 and from 0.05 to 5 μg/L for AFB2 and AFG2. The limits of detection and quantification were 0.025-0.1 and 0.075-0.3 μg/kg for peanuts and raisins, respectively. Recoveries at three other concentrations from 0.75 to 125 μg/kg of total aflatoxins were obtained between 76.5% and 99.8% (with RSD < 6%) following the SANTE 11312/2021. Validation parameters complied with the requirements of ISO/IEC 17025:2017. The extracts and the sample could be stabilized at 4°C and 20°C for 24 h and at -20°C for up to 21 days, respectively. Thus, the study can be used as a standard method for the analysis of Aflatoxins (AFs) in peanut and raisin matrices. Investigation of 350 peanut samples collected at Markets in the central districts of HCM city showed that 28.6% were contaminated with AFB1 from 0.31 up to 554 μg/kg; 13.4% contained AFB2, and 5.7% of AFG1 in the range of 0.4-53 μg/kg and 0.4-9.57 μg/kg, respectively; AFG2 (about 0.6%) was detected from 0.45 to 0.75 μg/kg. Meanwhile, 12.8% exceeded the total aflatoxins limit, and 13.4% exceeded the AFB1 limit. AFs were almost not found in the 350 raisin samples.

Spatial extrapolation of downscaled geochemical data using conditional GAN

Multi-scale geochemical data play an important guiding role in mineral exploration and environmental assessment. However, due to the influence of certain factors such as terrain, sampling cost and time, and instrument detection limit, geochemical data obtained from a study area are often incomplete or sparse. In this study, a conditional generative adversarial network (GAN) model was developed as a stochastic simulation technique for spatial extrapolation of downscaled geochemical data by learning nonlinear relationships between two soil geochemical datasets with different sampling densities, one set called fine data and the other coarse data. Taking Qianjiang City, Hubei Province, China as an example, first the fine data and coarse data were divided separately into training area and verification area for simulation in the GAN model. Then, exploratory data analysis, error analysis and variogram analysis were used to evaluate the realizations. Finally, Ni anomalies related to soil heavy metal pollution were extracted by combined concentration–area (C–A) fractal model and uncertainty analysis, in the verification area. Our studies indicate that the proposed conditional GAN model is efficient in extrapolating downscaled geochemical data, since both the realizations and fine data maintain similar spatial autocorrelation and statistical distribution.

Validasi Metode Penetapan Bahan Aktif Permethrin dalam Insektisida dengan High Performance Liquid Chromatography (HPLC)

Insecticides are substances or chemicals that are used to kill or eradicate insects. One of the active ingredients contained in insecticide products is permethrin. One of the tests carried out was testing the levels of the active ingredient such as permethrin in insecticides. This testing was carried out by High Performance Liquid Chromatography (HPLC). This method is a new method that will be used for routine analysis testing laboratory at Laboratory. The method that is used refers to the journal Validated High Performance Liquid Chromatography (HPLC) Method for Quantifying Permethrin in Pharmaceutical Formulations. Therefore, it is necessary to validate this method regarding elements that can cause variations in the test results and identify factors that can affect the performance of the method and determine the magnitude of the effect. Based on the test results, it can be concluded that all the validation parameters of the testing method for determining the active ingredient permethrin by high performance liquid chromatography gave the results of specificity, linearity, instrument detection limit (LDI), quantitation limit (LQ), repeatability precision, intermediate precision, accuracy, and the rigidity of the method meets the CIPAC 3807 requirements. Keywords: Insecticide, Permethrin, CIPAC 3807&#x0D; &#x0D; Keywords: Insecticide, Permethrin, CIPAC 3807

Method development for thermal desorption-gas chromatography-tandem mass spectrometry (TD-GC–MS/MS) analysis of trace level fluorotelomer alcohols emitted from consumer products

The scientific foundation for per- and polyfluoroalkyl substances (PFAS) measurements in water, soils, sediments, biosolids, biota, and outdoor air has rapidly expanded; however, there are limited efforts devoted to developing analytical methods to measure vapor-phase PFAS in indoor air. A gas chromatography-tandem mass spectrometry (GC–MS/MS) method coupled with thermal desorption (TD) sorbent tube analysis was developed to quantify trace levels of fluorotelomer alcohols (FTOHs) emitted from consumer products in the indoor environment. Method evaluation included determination of instrument detection limits (IDLs), quality assurance checks of target standards purchased from different vendors, sample loss during storage, and TD sorbent breakthrough with tubes coupled in-series. The IDLs for TD-GC–MS/MS analyses ranged from 0.07 – 0.09 ng/tube. No significant loss of FTOHs was observed during stability tests over 28 days with relative standard deviations (RSDs) of spiked TD tubes ranging from 3.1 – 7.7% and the RSDs of polypropylene copolymer vial storage of standard solutions ranging from 4.3 – 8.4%. TD tube breakthrough was minimal with recovered FTOHs in the second tubes <1% of the spiked concentrations in the first tubes with carrier gas volume up to 20 L. The method has been applied to determine FTOH emissions from three consumer products in micro-scale chambers. A liquid stone cleaner/sealer product contained the highest levels of 6:2, 8:2, and 10:2 FTOHs, while the mattress pad products contained lower levels of 8:2 and 10:2 FTOHs. The emission parameters, including the initial emission factors and first order decay rate constants, were obtained based on the experimental data. The developed methods are sensitive and specific for analysis of all four target FTOHs (4:2, 6:2, 8:2, 10:2 FTOHs) with chamber testing. The methods can be extended to indoor air sampling and could be applicable to ambient air sampling.

Analysis of polyhalogenated carbazoles and two related compounds in earthworms using a modified QuEChERS method with GC/MS and GC/MS/MS.

A precise analytical method based on QuEChERS has been proposed for the concurrent determination of 11 polyhalogenated carbazoles (PHCZs), benzocarbazole (BZCZ), and 9H-carbazoles (CZ). The quantification was confirmed by gas chromatography using triple quadrupole tandem mass spectrometry (Shimadzu GC-MS/MS-TQ8040) and gas chromatography coupled mass spectrometry (Agilent 7890A-5973 GC-MS). The developed method was validated by testing the following parameters: linearity, instrument limit of detection (LOD), instrument limit of quantification (LOQ), method limit of detection (MLD), method limit of quantification (MLQ), matrix effect (ME), accuracy, and precision. All compounds showed good linearity in the range of 0.005-0.2μg/mL with correlation coefficients higher than 0.992. The method demonstrated satisfactory recoveries (ranging from 71.21 to 105.04%) for most of the compounds with relative standard deviation precision (RSD) < 10.46%, except 3-BCZ (Recovery = 67.53%, RSD = 2.83%). The values of LOD and LOQ varied from 0.05 to 0.24ng and 0.14 to 0.92ng, respectively, while those of MLD and MLQ ranged from 0.02 to 0.12ng/g wet weight (ww) and 0.07 to 0.45ng/g ww, respectively. The developed method represents a reliable tool for the routine analysis of PHCZ congeners in invertebrate animals.

Ultrasound-Assisted Extraction, Followed by Gas Chromatography-Mass Spectrometry for the Simultaneous Quantification of Ethinyl Estradiol and Drospirenone in Contraceptive Formulations.

Contraceptive tablets typically contain a combination of two synthetic versions of an estrogen and a progestogen, which work together to inhibit the ovulation process. An accurate and precise quantification of these components is essential for contraceptive producers. In this study, we have developed the first gas chromatography-mass spectrometry (GC-MS) method for the simultaneous quantification of 17α-ethinyl estradiol (EE) and drospirenone (DP) in contraceptive formulations. Under the final working conditions, analytes were extracted from the solid by ultrasound-assisted extraction (15 min) in methanol. The resulting suspension was diluted in ethyl acetate, subjected to centrifugation and, finally, the supernatant was directly injected into the GC-MS system. No derivatization reagents were utilized. To correct for instrumental variations, calibration was performed using the internal standard method, with cholesterol as the internal standard. A good linearity was achieved throughout the calibration range for both EE (3-12 µg mL-1) and DP (300-1200 µg mL-1), with R2 values exceeding 0.99. Trueness, assessed in terms of percentages of recovery, was also found to be satisfactory for both analytes, with recovery rates of 106 ± 8% for EE and 93 ± 9% for DP. Furthermore, intra-day and inter-day precision studies yielded relative standard deviation values below 6% for both analytes. In terms of sensitivity, the instrumental limits of detection were 0.25 µg mL-1 for EE and 6.6 µg mL-1 for DP, and the instrumental limits of quantification 0.82 µg mL-1 for EE and 22 µg mL-1 for DP. The method was successfully applied to the analysis of contraceptive tablets from three different pharmaceutical companies. No differences were observed between the measured and the declared amount of active principle per tablet, demonstrating the applicability of the procedure. In addition, a stability study conducted on both the standards and sample extracts demonstrated that they can be stored at room temperature for a minimum period of seven days.

Determination of glyphosate and its derivative, aminomethylphosphonic acid, in human urine by gas chromatography coupled to tandem mass spectrometry and isotope pattern deconvolution

An analytical method for the simultaneous determination of glyphosate (GLY) and its main derivative, aminomethyl-phosphonic acid (AMPA), in human urine has been developed using gas chromatography coupled to tandem mass spectrometry (MS/MS) operated in multiple reaction monitoring mode (MRM). Sample preparation involved dilution of urine with water and derivatization with a mixture of trifluoroacetic acid anhydride and trifluoroethanol. Derivatization conditions such as reaction time and temperature, derivative stability, injection solvent, MS ionization mode and MS-MS transitions, among others, were studied to obtain the highest method sensitivity. The target compounds were initially quantified by the isotope dilution method using isotopically labelled analogs of GLY and AMPA as internal standards. However, due to spectral overlap between GLY and labelled GLY in the selected quantitative transition, a quantification method based on isotope pattern deconvolution (IPD) has been developed. The instrumental limits of detection were 0.05 ng mL−1 for both compounds, while the method detection limits were 0.39 and 0.25 ng mL−1, for AMPA and GLY, respectively. The mean recoveries from urine and water spiked at different concentrations were 77 and 69% for AMPA and 90 and 102% for GLY, respectively, with mean relative standard deviations of 8–10% (urine samples, n = 12) and 3.6–4% (water samples, n = 6). Once validated, the feasibility of the method was tested by determination of AMPA and GLY in human urine samples from people living close to agricultural areas. The developed method affords the determination of these compounds at trace concentrations in complex matrices such as urine, avoiding elaborate handling and cleanup steps. Isotope pattern deconvolution has proven to be a successful alternative to calibration curve for GLY overriding the method uncertainties associated to spectral overlapping.

Assessment of the Impacts of Artisanal Refinery of Crude Oil On Surface Water, Ground Water And Sediment Quality At Obi-Ayagha Community In Delta State Nigeria

&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Aim: &lt;/strong&gt;This study aims to assess the impacts of artisanal refinery activities on the quality of surface water, ground water, sediment and microbial density of the recipient environment at the abandoned artisanal refinery site in Obi-Ayagha community, Ughelli South, Delta State.&lt;/p&gt; &lt;p style="text-align: justify;"&gt;&lt;strong&gt;Place and Duration of Study: &lt;/strong&gt;Abandoned artisanal refinery hydrocarbon impacted site, Obi-Ayagha, Ughelli South, Delta State, Nigeria. During was from September 2021- February 2022.&lt;/p&gt; &lt;p style="text-align: justify;"&gt;&lt;strong&gt;Methodology: &lt;/strong&gt;&lt;strong&gt;F&lt;/strong&gt;ield sampling techniques were consistent with established and standards methodologies, Environmental Guidelines and Standards for Petroleum Industries in Nigeria (EGASPIN) and Federal Ministry of Environment (FMENV) procedural guidelines. Composite surface water samples were collected using a water sampler, ground water was collected using a water pump from drilled boreholes in the study site. Sediment sample was collected using Eckman dredge (grab) from the surrounding river around the study site. Physicochemical, microbial and metal parameters were analysed in the collected samples and controls, using standard methods to assess the impact of hydrocarbon contaminant from the artisanal refinery activities on the recipient environment.&lt;/p&gt; &lt;p style="text-align: justify;"&gt;&lt;strong&gt;Results: &lt;/strong&gt; The study revealed that there was a significant difference in Biochemical Oxygen Demand (BOD&lt;sub&gt;5&lt;/sub&gt;) values for the three borehole water sampled, with a mean value of 5.23± 3.0 mg/l and the control borehole site (3.00 ± 2mg/l). Total Petroleum Hydrocarbon results were below the instrument detection limit for the surface and ground water samples, while it recorded 5.38mg/kg for the sediment sample. Polyaromatic hydrocarbon results for all samples analysed were below the instrument detection limit of &lt;0.0001mg/kg. Total heterotrophic Bacteria counts obtained were between 2.08 -2.13 x 10&lt;sup&gt;3&lt;/sup&gt; CFU/ml, 1.13 - 1.26 x 10&lt;sup&gt;3 &lt;/sup&gt;CFU/ml and 2.36 x 10&lt;sup&gt;5 &lt;/sup&gt;CFU/g for surface water, groundwater and sediment samples respectively. Values obtained for all metals analysed in the study samples were within regulatory stipulated limits. Iron metal, though does not have available limits for sediment samples, recorded the highest concentration of 5585 ± 2.12 mg/kg in relation to other metals.&lt;/p&gt; &lt;p style="text-align: justify;"&gt;&lt;strong&gt;Conclusion:&lt;/strong&gt;Results obtained from the environmental samples analysed showed the parameters assessed were within regulatory limits. This could have been due to natural attenuation(remediation) of the environment giving the prolonged period of abandonment of the artisanal refining activities&lt;strong&gt;.&lt;/strong&gt;&lt;/p&gt; &lt;p style="text-align: justify;"&gt;The integration of artisanal and modular refinery operations into the oil and gas sector will curtail illegal oil activities in the Niger Delta regions and will also promote the availability of petroleum products, stabilize prices, eliminate shipping costs and provide employment opportunities for the inhabitants in the region and Nigeria in general. It is further recommended that with enough artisanal and modular refineries being granted license by the Federal Government in the country, Nigeria should be able to conserve foreign exchange currently utilized for the importation of petroleum products and promote socio-economic development.&lt;/p&gt;

Estimating transformations for evaluating diagnostic tests with covariate adjustment.

Receiver operating characteristic analysis is one of the most popular approaches for evaluating and comparing the accuracy of medical diagnostic tests. Although various methodologies have been developed for estimating receiver operating characteristic curves and their associated summary indices, there is no consensus on a single framework that can provide consistent statistical inference while handling the complexities associated with medical data. Such complexities might include non-normal data, covariates that influence the diagnostic potential of a test, ordinal biomarkers or censored data due to instrument detection limits. We propose a regression model for the transformed test results which exploits the invariance of receiver operating characteristic curves to monotonic transformations and accommodates these features. Simulation studies show that the estimates based on transformation models are unbiased and yield coverage at nominal levels. The methodology is applied to a cross-sectional study of metabolic syndrome where we investigate the covariate-specific performance of weight-to-height ratio as a non-invasive diagnostic test. Software implementations for all the methods described in the article are provided in the tram add-on package to the R system for statistical computing and graphics.

Determination of hydrazine in air by liquid chromatography/tandem mass spectrometry combined with precolumn derivatization.

In this study, we developed a determination method for hydrazine in the air. Hydrazine was derivatized with p-dimethyl amino benzaldehyde (DBA) to yield p-dimethylaminobenzalazine, which was subjected to liquid chromatography-electrospray tandem mass spectrometry (LC/MS/MS) analysis. The derivative exhibited good sensitivity in the LC/MS/MS analysis, and its instrument detection limit and instrument quantification limit were 0.003 and 0.008ng/mL, respectively. The air sample was collected using an air sampler equipped with a peristaltic pump at 0.2L/min for 8h. We demonstrated that a silica cartridge impregnated with DBA and 1,2-bis(4-pyridyl) ethylene can collect hydrazine in the air stably. The mean recovery rates in outdoor and indoor locations were 97.6% and 92.4%, respectively. Further, the method detection and quantification limits were 0.1 and 0.4ng/m3, respectively. The proposed method does not require any pretreatment and/or concentration step, enabling high-throughput analyses.

Improvement approach for determination of cadmium at trace levels in soils by handheld X-ray fluorescence analyzers

Determining trace levels of cadmium in soils by the handheld X-ray fluorescence analyzer is severely hampered by the spectrum baseline. To improve the peak-to-background ratio of the characteristic Cd-Kα X-ray, the filter structure, material, and thickness were optimized; to find the most informative variables for the PLS analysis of trace Cd, the related information enhancement competitive adaptive reweighted sampling (rieCARS) was proposed as a variable selection approach, which contains correlated spectral selection (CSS), double logarithmic processing(DLP), competitive adaptive reweighted sampling (CARS). To eliminate the interference of the K-series line of the Ag anode target on trace Cd, the X-ray tube was used with the Tungsten anode target. One combined filter containing a 0.4 mm thickness Cu and a 0.5 mm thickness Fe was selected, which was placed between the X-ray tube and the sample. The instrumental limit of detection for the Cd descended from 32 mg/kg to 0.02 mg/kg . Sixty-four soil samples were used to establish the model for the filtered signal. The model was compared with PLS, CARS+PLS, DLP + CARS+PLS, CSS + PLS, and CSS + CARS+PLS. The application of rieCARS improved the performance of the calibration model for trace Cd. The coefficient of determination R2 of the rieCARS+PLS model on the calibration set was 0.990; the RMSEP on the test set was 0.28 mg/kg; the average of the relative error in the Poyang Lake soil samples was 0.18; the relative standard deviation for the thirteen replicates of the GSD17 was 0.07. The developed analytical procedure will lay the foundation for the analysis of heavy metal pollution sources in soils and ecological sustainability assessment.

Determination of polychlorinated biphenyls in marine fish samples by gas chromatography tandem mass spectrometry (GC-MS/MS)

Polychlorinated biphenyls (PCBs) are a typical group of persistent organic pollutants (POPs), which have been listed under Annex A (Elimination) and Annex C (Unintentional production) of the Stockholm Convention. In this study, a gas chromatography tandem mass spectrometry method was developed and applied to analyze concentrations of 28 PCB congeners in some Vietnamese marine fish samples. PCBs in fish samples were ultrasonically extracted with an acetone/n-hexane (1/1, v/v) mixture. The extracts were cleaned up by using multilayer silica gel columns with dichloromethane/n-hexane (1/1, v/v) as elution solvent. PCBs were separated on a DB-5MS column and quantified by using a triple quadrupole mass spectrometer. The MS detector was operated in positive electron impact ionization (EI) mode and selected reaction monitoring (SRM) mode. Calibration curves of 28 PCBs exhibited good linearity (R2 &amp;ge; 0.9998). Instrument detection limits (IDLs) and method detection limits (MDLs) ranged from 0.08 to 0.023 ng/mL and from 0.07 to 1.84 ng/g, respectively. Recoveries of 28 PCBs native and 7 labeled standards in matrix-spike samples ranged from 62.3 to 88.1% and from 75.5 to 91.9%, satisfying criteria proposed by AOAC (recovery 60-115% for 10-100 ppb levels). The validated method was applied to analyze 10 marine fish samples, showing levels of &amp;sum;28PCBs from 17 to 851 (mean 230) ng/g lipid. The sum of 6in-PCBs (PCB-28; -52; -101; -138; -153; -180) based on wet weight (w/w) ranged from 1.24 to 3.15 ng/g, which is lower than the maximum level recommended by The European Union (75 ng/g (w/w). Congeners PCB-126 and PCB-169 were not detected in marine fish samples.

A Rapid Derivatization for Quantitation of Perfluorinated Carboxylic Acids from Aqueous Matrices by Gas Chromatography-Mass Spectrometry.

Ultrashort-chain perfluorinated carboxylic acids (PFCAs) are receiving more attention due to their ever-increasing presence in the environment. Methods have been established for the analysis of short- and long-chain PFCAs, while robust quantitation of ultrashort-chain species is scarce. Here, we develop a novel derivatization method using diphenyl diazomethane for quantitation of C2-C14 PFCAs in aqueous matrices. The method is highlighted by rapid completion of derivatization (<1 min) and retention and separation of ultrashort-chain (C2/C3) PFCA derivatives using H2 carrier gas (R > 1.5). A weak anion exchange solid-phase extraction procedure for analyte recovery from representative aqueous samples was developed and validated by spike and recovery from ultrapure water, synthetic ocean water, and simulated denuder extracts used for collecting gaseous PFCAs. Recoveries for PFCAs ranged from 83 to 130% for the majority of analytes and matrices. The instrument detection limits (IDLs) range from 8 to 220 fg per injection, and method detection limits (MDLs) range from 0.06 to 14.6 pg/mL for 500 mL aqueous samples, which are within an order of magnitude to conventional LC-MS/MS methods. The method was applied to the analysis of real samples of tap water, rainwater, ocean water, and annular denuder extracts. The overall method provides a cost-effective alternative to conventional LC-MS/MS methods, overcoming the typical GC-MS drawbacks of high detection limits and long sample preparation times while being able to simultaneously analyze the complete spectrum of environmentally relevant PFCAs.

Modular Set of Reagents in Lateral Flow Immunoassay: Application for Antibiotic Neomycin Detection in Honey

A scheme of modular competitive immunochromatography with an analyte-independent test strip and changeable specific immunoreactants has been proposed. Native (detected) and biotinylated antigens interact with specific antibodies during their preincubation in solution, that is, without the immobilization of reagents. After this, the detectable complexes on the test strip are formed by the use of streptavidin (which binds biotin with high affinity), anti-species antibodies, and immunoglobulin-binding streptococcal protein G. The technique was successfully applied for the detection of neomycin in honey. The visual and instrumental detection limits were 0.3 and 0.014 mg/kg, respectively, and the degree of neomycin revealed in honey samples varied from 85% to 113%. The efficiency of the modular technique with the use of the same test strip for different analytes was confirmed for streptomycin detection. The proposed approach excludes the necessity of finding the condition of immobilization for each new specific immunoreactant and transferring the assay to other analytes by a simple choice of concentrations for preincubated specific antibodies and the hapten-biotin conjugate.

Highly sensitive measurement method for photosensitizers based on dual-excitation laser modulation technique

A dual-excitation laser modulation technique for the sensitive measurement of photosensitizers in tumor is proposed. The technique is based on the difference in optical absorption properties of photosensitizers and biological tissues at 405 nm and 450 nm. The 405 nm and 450 nm laser beams, with the same modulation frequency and 180° phase difference, were coupled into a single fiber simultaneously. A periodic signal with a frequency of 1 kHz was generated in alternating excitation, and was processed by phase sensitive detectors. The weak photosensitizer fluorescence masked by tissue autofluorescence can be effectively separated through the proposed method, so that the final signal intensity is only related to the concentration of photosensitizer. The method with a sensitivity of 0.22 mL/ng was determined by measuring the low concentration of protoporphyrin IX (PpIX) solution, and the detection limit of instrument reached 0.5 ng/mL. The puncturable optical probe with a diameter of 675 µm ensures that PpIX in can be detected with spatial resolution, which was performed in the measurement of PpIX in tumor bearing nude mice.

Quantifying lead, copper, iron and arsenic in hair dye samples.

Heavy metals are very hazardous to human health. In the USA, the Food and Drug Administration (FDA) regulates cosmetics so that they are safe for consumer use. However, internet shopping has made it easier for non-FDA approved cosmetics to come into the United States. People have reported serious health problems after using counterfeit cosmetics purchased online. This project focuses on analyzing commercial hair dyes for the presence of As, Cu, Fe, and Pb. Dyes were purchased locally and online, digested in aqua regia and tested with a Shimadzu AA-7000 flame atomic absorption instrument. The concentrations of Cu, Fe and Pb were below the instrument detection limits of 0.02, 0.06, 0.4 ppm respectively, and the amount of As in one sample was inconclusive due to quality control failure. Overall, no significant amounts of metals were detected in the samples. This work was made possible by NASA West Virginia Space Grant Consortium Grant #80NSSC20M0055, and Fairmont State University Chemistry Program.

In-situ Diffusive Gradients in thin-films passive sampling coupled with ex-situ small-sized electrothermal vaporization capacitively coupled plasma microtorch optical emission spectrometry as green and white method for the simultaneous determination of labile species of toxic elements in surface water

This study presents for the first time the coupling between in-situ Diffusive Gradient in Thin-film (DGT) passive sampling technique and ex-situ small-sized instrumentation based on electrothermal vaporization capacitively coupled plasma microtorch optical emission spectrometry (SSETV-μCCP-OES) for the simultaneous determination of Cd, Pb, Cu, Zn and Hg in surface water. Unique features of the DGT-SSETV-μCCP-OES are low power and low Ar consumption for plasma generation (15 W, 150 mL min−1) and significant improvement of the detection limits following DGT passive sampling. The new method was validated in terms of river water analysis in comparison with graphite furnace atomic absorption spectrometry and thermal decomposition atomic absorption spectrometry. Combining the abilities of preconcentration by in-situ Chelex-DGT passive sampling with plasma microtorch equipped with a low resolution microspectrometer provided multielemental simultaneous determination with detection limits of (μg L−1) 0.01 (Cd, Zn and Hg), 0.02 (Cu) and 0.07 (Pb) in water, at least one order of magnitude better than using grab sampling without preconcentration. It was possible the quantification of labile fraction of priority hazardous metals (Cd, Pb) in river water below the instrumental limits of detection (μg L−1) of 0.12 and 0.80 obtained in SSETV-μCCP-OES without DGT sampling. The precision of the method was in the range 15.3–22.4% (combined uncertainty), while the accuracy was 95–103% and trueness of 27–33% (expanded uncertainty, k = 2). The DGT-SSETV-μCCP-OES coupling proved to be an ideal and powerful tool for surface water analysis in compliance with green and white analytical chemistry concepts. The application of the RGB-12 algorithm provided very good red/green (AGREEprep)/blue/white scores (%) of 100/80/98/93, determined primarily by in-situ DGT passive sampling, very good detection limits and cost-effective SSETV-μCCP-OES instrumentation.

Probe-based mass spectrometry approaches for single-cell and single-organelle measurements.

Exploring the chemical content of individual cells not only reveals underlying cell-to-cell chemical heterogeneity but is also a key component in understanding how cells combine to form emergent properties of cellular networks and tissues. Recent technological advances in many analytical techniques including mass spectrometry (MS) have improved instrumental limits of detection and laser/ion probe dimensions, allowing the analysis of micron and submicron sized areas. In the case of MS, these improvements combined with MS's broad analyte detection capabilities have enabled the rise of single-cell and single-organelle chemical characterization. As the chemical coverage and throughput of single-cell measurements increase, more advanced statistical and data analysis methods have aided in data visualization and interpretation. This review focuses on secondary ion MS and matrix-assisted laser desorption/ionization MS approaches for single-cell and single-organelle characterization, which is followed by advances in mass spectral data visualization and analysis.