Acid In Water Samples Research Articles

Development of facile field-test paper for rapid determination of iron contamination in natural water of acid sulfate soils

Abstract The iron concentration in natural water of acid sulfate soils is usually determined by complicated methods of SMEWW 3111B:2017 or ISO 6332: 1988 E in the laboratory for acidified water samples at pH ∼2–3. Therefore, the rapid field determination of iron content in natural water is a very useful method because it limits the error and reduces the experimental time for analysis. In this study, we proposed, developed, and tested a rapid colorimetric analysis method based on the chemical reaction of ferric and anion thiocyanate (SCN−) ions for an iron concentration range of 0–100 mg/L with a linear equation of ΔE = 0.5955x + 2.0909 and high correlation coefficient (R2) of 0.9864. The results from 10 water samples by this method were very close to those by flame absorption spectroscopy with a difference of less than 5%. Besides the biggest advantage of rapid site testing, this method also gives quite high accuracy compared to the molecular absorption method of ISO 6332:1988 E. In addition, this new method can quantify Fe3+, Fe2+, and total iron in water, suggesting a very useful and potential method for determining the iron content of natural water from acid sulfate soils.

Toxic Elements in Sediment and Water of the Crocodile River (West) System, South Africa, Following Acid Mine Drainage

The upper reaches of the Crocodile River (West) system are located in the western basin of the Witwatersrand mountain chain, an area heavily influenced by gold mining. After the spill of highly acidic and contaminated mining-influenced water into the river system in 2002, chemical water treatment was implemented to compensate for the consequences of acid mine drainage. Some studies thereafter have shown metal concentrations of concern in the system, but never considered longer periods of time. For this study, we investigated water and sediments over a period of 13 months from 7 sampling sites in the system. In addition to physico-chemical parameters such as temperature, pH, and electrical conductivity, a multi-element analysis was conducted. We used various versions of atomic-absorption-spectroscopy, total reflection x-ray fluorescence spectroscopy, and inductively coupled plasma mass spectrometry in filtered and acidified water samples as well as sediment leachates. Concentrations of Ni, Zn, As, Pb, and U in the sediment were clearly elevated at the site closest to the mine as well as further downstream, some of them far exceeding quality guidelines. Moreover, dissolved Mn, Fe, Ni, Zn and U occurred irregularly in concentrations of concern at the site of mining-influenced water inflow. Our findings clearly indicate a risk of further and chronic mobilization of toxic elements from this site and a possible threat to the connected river system.

Longer amplicons provide better sensitivity for electrochemical sensing of viral nucleic acid in water samples using PCB electrodes

The importance of monitoring environmental samples has gained a lot of prominence since the onset of COVID-19 pandemic, and several surveillance efforts are underway using gold standard, albeit expensive qPCR-based techniques. Electrochemical DNA biosensors could offer a potential cost-effective solution suitable for monitoring of environmental water samples in lower middle income countries. In this work, we demonstrate electrochemical detection of amplicons as long as {503},hbox {bp} obtained from Phi6 bacteriophage (a popular surrogate for SARS-CoV-2) isolated from spiked lake water samples, using ENIG finish PCB electrodes with no surface modification. The electrochemical sensor response is thoroughly characterised for two DNA fragments of different lengths ({117},hbox {bp} and {503},hbox {bp}), and the impact of salt in PCR master mix on methylene blue (MB)-DNA interactions is studied. Our findings establish that length of the DNA fragment significantly determines electrochemical sensitivity, and the ability to detect long amplicons without gel purification of PCR products demonstrated in this work bodes well for realisation of fully-automated solutions for in situ measurement of viral load in water samples.

A novel amino functionalized three-dimensional fluorescent Zn-MOF: The synthesis, structure and applications in the fluorescent sensing of organic water pollutants

An amino functionalized three-dimensional (3D) Zn-MOF with molecular formula Zn(NH2bdc)(mbib) (complex 1) has been synthesized by using solvothermal method. The structure, purity, stability and morphology of complex 1 was fully characterized with single-crystal X-ray diffraction, PXRD, FT-IR, TGA, TEM, et al. The characterization results revealed that complex 1 crystallizes in the orthorhombic space group Pna21. In the structure of complex 1, each NH2bdc2− ligand connected to two Zn(II) to form a 1D zigzag chain which was further connected by the mbib ligands to give a fourfold interpenetration 3D framework. The single-crystal X-ray diffraction analysis indicated that the 3D framework of complex 1 was functionalized with free amino groups both on the surface and in the channels. Characteristic fluorescent emission centered at 430 nm which could be remarkably enhanced in water was observed, indicating complex 1 might be a promising candidate for the fluorescent sensing of water pollutants. The functionalized amino groups remarkably enhanced the selectivity and sensitivity of complex 1. Gradually fluorescence quenching of complex 1 was recorded in the fluorescent titration experiments with good quantitative relation after addition of acetone or picric acid in water samples. The experimental detection limits for acetone and picric acid were 0.03% (%V) and 340 nM, respectively. Plausible mechanisms for the fluorescent quenching sensing of acetone and picric acid were proposed.

Benzothiazole Pyrazoline: Acid-Switchable Absorption and Fluorescence of Photoinduced Electron Transfer (PET).

Acid-responsive fluorescent compounds were prepared by introducing an ortho-hydroxyphenyl to pyrazoline with a benzothiazole backbone. These compounds demonstrated normal fluorescence photoinduced electron transfer (PET) under neutral conditions but the addition of trifluoroacetic acid showed an arctic blue fluorescence, we verified that a protonation process of nitrogen in the thiazole ring which weakened the ability of thiazole to donate electrons to the pyrazoline and changed the photoinduced electron transfer led to photoinduced electron transfer (PET), which was the mechanism of the fluorescence quenching phenomenon under strongly acidic conditions. The photophysical properties of Benzothiazole pyrazoline exhibited blue emission at 421nm in aqueous DMSO. The blue shift in the emission was switched by acid in DMSO, showing the compound's distinct fluorescence peak at 554nm. To investigate solvatochromism, eight different solvents were used. The red-shift emission observed in enhancing the polarity of solvents and emission in DMSO suggested the conformation of the molecule which led to the intramolecular charge transfer by color and emission changes. Furthermore, the probe was also applied using the High-performance liquid chromatography (HPLC) with a UV detector to determine the trifluoroacetic acid in water samples. Interestingly, the method was found to be linear over the range of 10.0µg L-1 to 250.0µg L-1 (0.999). Under the optimum condition, the separation of trifluoroacetic acid was achieved in 20min with the LOD of 1.3µg L-1 and LOQ of 5.1µg L-1. This proposed method also showed satisfactory results when applied for the analysis of trifluoroacetic acid in a water sample.

Fluorescent probe for the detection of hypochlorous acid in water samples and cell models.

Hypochlorous acid (HClO) is a special kind of reactive oxygen species, which plays an important role in resisting pathogen invasion and maintaining cell redox balance and other physiological processes. In addition, HClO is commonly used in daily life as a bleaching and disinfectant agent. Its excessive use can also lead to death of water animals and serious respiratory and skin diseases in humans. Therefore, it is of great significance to develop a quick and convenient tool for detecting HClO in the environment and organisms. In this paper, we utilize the specific reaction of HClO with dimethylthiocarbamate to develop a novel naphthalene derivative fluorescent probe (BNA-HClO), it was designed and synthesized by using 6-(2-benzothiazolyl)-2-naphthol as the fluorophore and N,N-dimethylthiocarbamate as the recognition group. BNA-HClO shows large fluorescence enhancement (374-fold), high sensitivity (a detection limit of 37.56 nM), rapid response (<30 s), strong anti-interference ability and good specificity in vitro. Based on the outstanding in vitro sensing capability of BNA-HClO, it has been successfully used to detect spiked HClO in tap water, medical wastewater and fetal bovine serum with good recovery. BNA-HClO has also been successfully used as a portable test strip for the in situ semi-quantitative detection of HClO in tap water solutions. In addition, BNA-HClO can successfully enable the detection and imaging of exogenous and endogenous HClO in living cells. This work provides a simple and effective tool for the detection and imaging of HClO in environmental and biological systems, and provides some theoretical guidance for future exploration of biological and pathological studies related to HClO.

Simultaneous determination of seven perfluoroalkyl carboxylic acids in water samples by 2,3,4,5,6-pentafluorobenzyl bromide derivatization and gas chromatography-mass spectrometry

A new derivatization reagent, 2,3,4,5,6-pentafluorobenzyl bromide (PFBBr), was employed to determine seven perfluoroalkyl carboxylic acids (PFCAs) simultaneously in tap water with gas chromatography-mass spectrometry (GC-MS) technique in this study. Firstly, seven PFCAs were derivatized to their corresponding esters under alkaline condition. The derivatization conditions including the amount of PFBBr and K2CO3, derivatization temperature and time were optimized to increase the derivatization efficiency. The 14 tap water samples collected from different places of China were enriched and purified through solid phase extraction pretreatment. The limits of detection (LODs) and the limits of quantitation (LOQs) ranged from 0.1 ng/L to 0.28 ng/L and from 0.3 ng/L to 0.84 ng/L, respectively. The new method offers a linear relationship in the range from 2 ng/L to 2000 ng/L, and the correlation coefficients ranged from 0.9938 to 0.9994. The results showed that GC-MS combined with pre-column derivatization is a reliable method for the analysis of PFCAs in the aqueous environment.

4-t-Butylbenzylation of carboxylic acid for GC\u2013MS analysis

We report a 4-t-butylbenzyl derivatization for the analysis of carboxylic acids by GC–MS (EI). Carboxylic acids were analyzed as a 4-t-butylbenzyl ester after the derivatization with 4-t-butylbenzyl bromide. On the mass spectra of 4-t-butylbenzyl ester, [M-15]+ ions were observed with high intensity. These ions were tertiary benzyl cations generated by the elimination of a methyl radical from molecular ions. After optimization of the 4-t-butylbenzyl derivatization conditions using microwave reactor, we established a method for the determination of the carboxylic acids in water samples. The method showed good sensitivity and good reproducibility, and was successfully applied to the analysis of rain water samples.

Applicability of mixed-mode chromatography for the simultaneous analysis of C1-C18 perfluoroalkylated substances.

A new analytical method for the determination of 22 perfluoroalkylated (carboxylic and sulfonic) acids in water samples is presented. The method's objective was to achieve the simultaneous quantification of compounds with different chain lengths (from C1 to C18). To this end, 500mL of water were extracted with Oasis WAX solid-phase extraction cartridges and eluted with 3mL of 5% ammonia in methanol. After evaporation to dryness, extracts were reconstituted in methanol:ultrapure water (1:1) and analyzed by mixed-mode liquid chromatography-tandem mass spectrometry (MMLC-MS/MS) using a weak anion exchange/reversed-phase column. The method provided good results, with limits of quantification lower than 1ng/L in river water for most of compounds, except the two perfluorocarboxylic acids with the longest alkyl chain (>C14) and trifluoroacetic acid, for which a blank contamination problem was observed. The method proved good trueness and precision in both ultrapure and river water (R ≥ 81%, RSD ≤ 15%). After validation, the method was applied to the analysis of nine water samples where nine perfluoroalkylated acids were quantified. Seven of them were ultrashort- (C1-C4) and short-chain (C4-C8) perfluoroalkylated acids, pointing out the importance of developing methods capable to target such substances for further monitoring.

Solid-phase extraction of seventeen alternative flame retardants in water as determined by ultra-high-performance liquid chromatography-tandem mass spectrometry

Flame retardants have evoked public concerns owing to their extensive usage in consumer products and potential adverse effects on human health. In this study, a rapid and sensitive solid-phase extraction-ultra-high-performance liquid chromatography-tandem mass spectrometry (SPE-UPLC-MS/MS) method was developed to determine hexabromocyclododecane (HBCD), tetrabromobisphenol-A (TBBPA), six bromophenols (BPs), and nine organophosphate flame retardants (OPFRs) in water. Because of the differences in elution conditions and ionization modes for group 1 (HBCD, TBBPA, and the BPs) and group 2 (OPFRs), we had to run them twice under the different conditions to analyse group 1 and group 2 using UPLC-MS/MS. The method detection limits were 0.1–2.5 ng/L, linearity range was 0.1–100.0 ng/L for group 1 (HBCD, TBBPA, and the BPs). The method detection limit was 0.10 ng/L, and the linearity range was 0.25–250 ng/L for the OPFRs. First, the pH values of the water samples were adjusted to the range of 2–3. Then, the acidified water samples were extracted by hydrophilic-lipophilic-balance solid phase extraction (HLB-SPE) cartridges, which were eluted with 12 mL of acetonitrile. Finally, the recoveries of HBCD, TBBPA, and the BPs were 76.2–98.1%, and the relative standard deviations (RSDs, n = 5) were 2.0–28.5%. Regarding the OPFRs, the recoveries were 72.4–110.3%, and the RSDs were 0.6–6.9%. The stability experiment showed that the concentration differences were less than 15%, meeting the requirement for quality control samples. This proposed method was successfully applied to surface water, ground water, raw water, finished water, tap water, and bottled water samples.

Bar adsorptive microextraction coated with multi-walled carbon nanotube phases - Application for trace analysis of pharmaceuticals in environmental waters

Bar adsorptive microextraction devices were modified with multi-walled carbon nanotubes for the first time. A bar adsorptive microextraction method followed by microliquid desorption and high-performance liquid chromatography with diode array detection was developed for the determination of trace levels of ketoprofen, diclofenac, gemfibrozil and mefenamic acid in water samples. The mean parameters affecting the bar adsorptive microextraction and microliquid desorption efficiency were studied and optimized using a univariate optimization strategy. The methodology was validated in terms of linearity, limits of detection and quantification, recovery, intra- and inter-day precision, accuracy, and matrix effect.The developed method showed lower limits of quantification of 0.35 μg L−1, calibration curves from 0.35 up to 1000.0 μg L−1 and determination coefficients higher than 0.9917. Recoveries in tap, surface, sea and waste water samples at three spiking levels were between 70.2 and 117.3% for all the pharmaceuticals. The coefficients of variation values for intra- (n = 6) and inter-day precisions (n = 18) were below 9.7%. The proposed analytical methodology allowed preconcentration factors up to 250 and proved to be cost-effective, easy to operate and environmentally friendly.

Removal of Humic Acid from Water by Magnetic Chitosan-Grafted Polyacrylamide

For high-efficiency removal of humic acid (HA), a natural organic matter in the water source, an adsorbent named magnetically modified chitosan-grafted polyacrylamide (MC-g-PAM) was developed by using an in situ coprecipitation method. Analytical instruments, such as a Fourier transform infrared (FTIR) spectroscope, scanning electron microscope (SEM), vibrating sample magnetometer (VSM), and specific surface area tester (BET), were used to characterize and analyze this material. With the aid of batch tests, the removal efficiency and mechanism of humic acid in water samples were investigated. The results show that the specific surface area and specific saturation magnetization values of the prepared MC-g-PAM are 27.065 m2·g-1 and 9.63 emu·g-1, respectively. The adsorption of humic acid by MC-g-PAM is an endothermic process and the Langmuir isotherm model and the pseudo-second-order kinetic equation fit the adsorption process well. At 25℃, the equilibrium adsorption capacity of MC-g-PAM to humic acid reaches 120.77 mg·g-1.

Synthesis of Fluorescent Nitrogen-Doped Carbon Quantum Dots for Selective Detection of Picric Acid in Water Samples.

In this work, fluorescent nitrogen-doped carbon dots (N-CDs) were pyrolysis synthesized using edetic acid and acrylamide as precursors without further surface modication. The as-prepared N-CDs were mono-dispersed spherical nanoparticles with an average diameter of 3.25 nm. The blue fluorescence emission was dependent of the excitation wavelengths, releasing stable and strong blue fluorescence under the maximum excitation wavelength. More strikingly, after adding picric acid (PA), the fluorescence of N-CDs aqueous solution gave rise to the obviously fluorescence quenching due to the inner filter effect. Under the optimum conditions, the fluorescence probe can be used for the selective detection of PA with a wide linear relationship in the range of 0.01-32 μM and the detection as low as 0.046 μM. Depending on the fluorescence quenching phenomenon, the resultant fluorescent probe for accurate and selective monitor of PA in Fenhe river samples was explored. The recoveries fell in the range of 97.13%-106.21% and the relative standard deviation was below 3% with satisfactory results.

AIE-active luminogen for highly sensitive and selective detection of picric acid in water samples: Pyridyl as an effective recognition group

Detection of nitroaromatic explosives especially picric acid (PA) is considerably worth concern on human safety and homeland security. Herein, we developed an effective probe (APPTPEP) for PA detection in aqueous medium by combination of 1,4-dihydropyrrolo[3,2-b]pyrrole with tetraphenylethylene and pyridine units. The incorporation of tetraphenylethylene unit in the backbone endows the APPTPEP a significant aggregation induced emission (AIE) behavior. Pyridyl group was proved as recognition site for PA and their strong interaction was confirmed by 1H NMR titration and supported by theoretical calculation. Owing to this strong affinity, APPTPEP exhibited high selectivity and sensitivity (limit of detection 31.5 nM) to PA over other nitroaromatic compounds. This research provides new insights into the rational design of AIE-active materials for effective sensing application.

Advantage of liquid chromatography with high-resolution mass spectrometry for the detection of the small and polar molecules trifluoroacetic acid and sulfamic acid.

This study addresses the selectivity of liquid chromatography with tandem mass spectrometry for the analysis of the polar analytes trifluoroacetic acid and sulfamic acid in water samples. Such analytes often lack sufficient retention in standard reversed-phase liquid chromatography and rarely produce mass spectrometry transition products of high diagnostic evidence by collision-induced dissociation. The chromatography based on an extra-dense bonding liquid chromatography column for trifluoroacetic acid and on hydrophilic interaction chromatography for sulfamic acid. This enabled sufficient retention of more than twice the void volume for both analytes. Liquid chromatography coupled to low-resolution mass spectrometry was compared with high-resolution mass spectrometry. The limits of quantification for direct injection analysis were determined to<0.05μg/L for trifluoroacetic acid and<0.5μg/L for sulfamic acid. Correction of matrix effects either by internal standards or the standard addition is strongly recommended as matrix effects may vary strongly. The concentrations determined for trifluoroacetic acid and sulfamic acid for real samples were comparable between low and high-resolution mass spectrometry. However, low-resolution mass spectrometry does not fulfill the identification criteria of the analytes following the European Commission council directive 96/23/EC or the SANTE/11945/2015. Since low-resolution mass spectrometry for these analytes may result in false-positive findings, such findings may be controlled by high-resolution mass spectrometry.

A sensitive and specific solid-phase extraction-gas chromatography-tandem mass spectrometry method for the determination of 11 haloacetic acids in aqueous samples.

A method for the analysis of 11 haloacetic acids in water samples has been developed. It involves enrichment of the target analytes from water samples by solid-phase extraction, derivatization to methyl esters, and gas chromatography coupled with tandem mass spectrometry determination. Gas chromatography conditions were optimized for a good separation of all haloacetic acids in a short runtime. Data were acquired in the multiple reaction monitoring mode. Six solid-phase extraction sorbents among the most widely used in environmental analysis were tested. Bakerbond SDB was retained because it has been shown to provide the best results for a large class of targeted haloacetic acids. The performances of the developed method have been assessed according to the French Standard NF T 90-210. The calibration curves for all the studied haloacetic acids had consistent slopes with r2 values > 0.99. Quantification limits between 0.01 and 0.50 µg l-1 were achieved. Satisfactory repeatability (relative standard deviation ≤ 14.3%) and intermediate precision (relative standard deviation ≤ 15.7%) were obtained. Applied to the analysis of 15 untreated water samples collected from three rivers, the method allowed the detection of five haloacetic acids including monochloroacetic acid (in 100% of the samples, <0.5-1.85 µg l-1), dichloroacetic acid (87%, <0.05-0.22 µg l-1), trichloroacetic acid (93%, <0.05-0.52 µg l-1), dibromoacetic acid (53%, <0.01-0.40 µg l-1), tribromoacetic acid (20%, <0.05-0.14 µg l-1), and bromodichloroacetic acid (6%, < 0.05 µg l-1).

UV-Vis spectroscopic detection coupled with chemometrics for the measurement of mixed organic acids in water samples enriched by radial electric focusing solid phase extraction

UV-Vis spectroscopic detection coupled with chemometrics for the measurement of mixed organic acids in water samples enriched by radial electric focusing solid phase extraction

Comparison of methods for determination of total oil sands-derived naphthenic acids in water samples

There are several established methods for the determination of naphthenic acids (NAs) in waters associated with oil sands mining operations. Due to their highly complex nature, measured concentration and composition of NAs vary depending on the method used. This study compared different common sample preparation techniques, analytical instrument methods, and analytical standards to measure NAs in groundwater and process water samples collected from an active oil sands operation. In general, the high- and ultrahigh-resolution methods, namely high performance liquid chromatography time-of-flight mass spectrometry (UPLC-TOF-MS) and Orbitrap mass spectrometry (Orbitrap-MS), were within an order of magnitude of the Fourier transform infrared spectroscopy (FTIR) methods. The gas chromatography mass spectrometry (GC-MS) methods consistently had the highest NA concentrations and greatest standard error. Total NAs concentration was not statistically different between sample preparation of solid phase extraction and liquid-liquid extraction. Calibration standards influenced quantitation results. This work provided a comprehensive understanding of the inherent differences in the various techniques available to measure NAs and hence the potential differences in measured amounts of NAs in samples. Results from this study will contribute to the analytical method standardization for NA analysis in oil sands related water samples.

Application of a dispersive solid-phase extraction method using an amino-based silica-coated nanomagnetic sorbent for the trace quantification of chlorophenoxyacetic acids in water samples.

Herein, an amino-based silica-coated nanomagnetic sorbent was applied for the effective extraction of two chlorophenoxyacetic acids (2-methyl-4-chlorophenoxyacetic acid and 2,4-dichlorophenoxyacetic acid) from various water samples. The sorbent was successfully synthesized and subsequently characterized by scanning electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. The analytes were extracted by the sorbent mainly through ionic interactions. Once the extraction of analytes was completed, they were desorbed from the sorbent and detected by high-performance liquid chromatography with ultraviolet detection. A number of factors affecting the extraction and desorption of the analytes were investigated in detail and the optimum conditions were established. Under the optimum conditions, the calibration curves were linear over the concentration range of 1-250, and based on a signal-to-noise ratio of 3, the method detection limits were determined to be 0.5μg/L for both analytes. Additionally, a preconcentration factor of 314 was achieved for the analytes. The average relative recoveries obtained from the fortified water samples varied in the range of 91-108% with relative standard deviations of 2.9-8.3%. Finally, the method was determined to be robust and effective for environmental water analysis.

Standard method design considerations for semi-quantification of total naphthenic acids in oil sands process affected water by mass spectrometry: A review

Naphthenic acids are a complex class of thousands of naturally occurring aliphatic and alicyclic carboxylic acids found in oil sands bitumen and in the wastewater generated from bitumen processing. Dozens of analytical methods have been developed for the semiquantification of total naphthenic acids in water samples. However, different methods can give different results, prompting investigation into the comparability of the many methods. A review of important methodological features for analyzing total naphthenic acids is presented and informs the design of future standard methods for the semiquantification of total naphthenic acids using mass spectrometry. The design considerations presented are a synthesis of discussions from an Environment and Climate Change Canada (ECCC) led taskforce of 10 laboratory experts from government, industry and academia during April 2016 and subsequent discussions between University of British Columbia and ECCC representatives. Matters considered are: extraction method, solvent, pH, and temperature; analysis instrumentation and resolution; choice of calibration standards; use of surrogate and internal standards; and use of online or offline separation prior to analysis. The design considerations are amenable to both time-of-flight and Orbitrap mass spectrometers.