Determination Of Ultra-trace Levels Research Articles

Determination of ultra-trace rare earth elements in high-salt groundwater using aerosol dilution inductively coupled plasma-mass spectrometry (ICP-MS) after iron hydroxide co-precipitation

Analysis data of rare earth elements (REEs) in high-salt groundwater can potentially provide a series of geochemical indicators. Accurate determination of sub-ng L−1 levels of REEs by inductively coupled plasma-mass spectrometry (ICP-MS) is still a challenge because of low concentrations, significant matrix effects from the highly dissolved salts, and mass spectral interferences. A reliable method, based on online aerosol dilution ICP-MS after co-precipitation with Fe(OH)3, was evaluated for the determination of REEs in high-salt groundwater. First, an Fe(OH)3 co-precipitation procedure effectively separated the target REEs from the high-content matrix elements (i.e. K, Na, Ca, and Mg); over 93% of the matrix elements were removed and target REEs were concentrated 15-fold. Secondly, using the proposed online aerosol dilution technique resulted in diminished residual matrix effects and the reduction of mass spectral interferences from oxide ions (i.e. Ba and light REE-oxides) by up to 10-fold. The detection limits of the method ranged from 0.05ngL−1 for Lu to 0.6ngL−1 for Nd, with the REE recoveries between 90% and 125%. The results for a seawater standard reference material (NASS-6) agreed with literature reported values. The proposed method was employed for the analysis of five high-salt groundwater samples. The accurate results showed that this method has great potential for the determination of ultra-trace levels of REEs in various high-salt water samples.

Determination of ultratrace levels of tributyltin in waters by isotope dilution and gas chromatography coupled to tandem mass spectrometry

The current EU legislation lays down the Environmental Quality Standards (EQS) of 45 priority substances in surface water bodies. In particular, the concentration of tributyltin (TBT) must not exceed 0.2ngL−1 and analytical methodologies with a Limit of Quantification (LOQ) equal or below 0.06ngL−1 are urged to be developed. This work presents a procedure for the determination of ultratrace levels of TBT in water samples by Isotope Dilution and GC–MS/MS operating in Selected Reaction Monitoring (SRM) mode which meets current EU requirements. The method requires the monitorization of five consecutive transitions (287>175 to 291>179) for the sensitive and selective detection of TBT. The measured isotopic distribution of TBT fragment ions was in agreement with the theoretical values computed by a polynomial expansion algorithm. The combined use of Tandem Mass Spectrometry, a sample volume of 250mL, the preconcentration of 1mL of organic phase to 30μL and an injection volume of 25μL by Programmed Temperature Vaporization provided a LOQ of 0.0426ngL−1 for TBT (calculated as ten times the standard deviation of nine independent blanks). The recovery for TBT calculated in Milli-Q water at the EQS level was 106.3±4%. A similar procedure was also developed for the quantification of dibutyltin (DBT) and monobutyltin (MBT) in water samples showing satisfactory results. The method was finally implemented in a routine testing laboratory to demonstrate its applicability to real samples obtaining quantitative recoveries for TBT at the EQS level in mineral water, river water and seawater.

A new ultrasonic-assisted cloud-point-extraction procedure for pre-concentration and determination of ultra-trace levels of copper in selected beverages and foods by flame atomic absorption spectrometry

A new ultrasonic-assisted cloud-point-extraction (UA-CPE) method was developed for the pre-concentration of Cu(II) in selected beverage and food samples prior to flame atomic absorption spectrometric (FAAS) analysis. For this purpose, Safranin T was used as an ion-pairing reagent based on charge transfer in the presence of oxalate as the primary chelating agent at pH 10. Non-ionic surfactant, poly(ethyleneglycol-mono-p-nonylphenylether) (PONPE 7.5) was used as an extracting agent in the presence of NH4Cl as the salting out agent. The variables affecting UA-CPE efficiency were optimised in detail. The linear range for Cu(II) at pH 10 was 0.02–70 µg l–1 with a very low detection limit of 6.10 ng l–1, while the linear range for Cu(I) at pH 8.5 was 0.08–125 µg l–1 with a detection limit of 24.4 ng l–1. The relative standard deviation (RSD %) was in the range of 2.15–4.80% (n = 5). The method was successfully applied to the quantification of Cu(II), Cu(I) and total Cu in selected beverage and food samples. The accuracy of the developed method was demonstrated by the analysis of two standard reference materials (SRMs) as well as recoveries of spiked samples.

Controlling contamination for determination of ultra-trace levels of priority pollutants chlorophenols in environmental water matrices

Recently, environmental scientists have been focused their attention on the occurrence of emerging contaminants in water, such as disinfection by products (DBPs), including chlorophenols. These pollutants can be a public health problem due to their carcinogenic properties. In this work, ultra-high pressure liquid chromatography (UHPLC) coupled to a photodiode array detector (PDA) was used for the development of an analytical method capable of simultaneous identification and quantification of two chlorophenols namely, 2-chlorophenol and 2,4-dichlorophenol in water samples. In addition, a solid phase extraction (SPE) procedure for the extraction of these compounds was optimized. The chlorophenols were separated by an Acquity BEH C18 (100×2.1mm, 1.7μm) column with a mobile phase of acetonitrile/ultrapure water/formic acid (55/45/0.1, v/v/v). The flow rate of the mobile phase was 0.4mLmin−1. The optimized SPE–UHPLC/PDA technique was evaluated in terms of robustness, considering the enrichment factor for all of the studied chlorophenols. Linear calibration was obtained with correlation coefficients r2⩾0.998. Intra-day and inter-day precision was less than 5% and accuracy ranged from 99.95% to 103.32%, respectively. The obtained extraction recoveries were higher than 98%. The pre-concentration factor was 2.500 for the both analytes. Under optimized conditions, the detection limits of the overall SPE–UHPLC/PDA method were in the ngL−1 level. The excellent performance of the developed method, as well as the short analysis time makes it a promising analytical tool for the screening of chlorophenols in environmental water samples.

Development of an LC–MS method for ultra trace-level determination of 2,2,6,6-tetramethylpiperidine-1-oxl (TEMPO), a potential genotoxic impurity within active pharmaceutical ingredients

TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) is a stable free radical which has been widely used for various research and industrial applications, including the manufacture of many active pharmaceutical ingredients. TEMPO has been identified as a potential genotoxic impurity resulting in the need for analytical methodology to accurately determine its level at several orders of magnitude less than typical impurity quantitation limits. TEMPO can undergo disproportionation to form both oxidized and reduced TEMPO, making individual determination unreliable. To overcome this challenge, all TEMPO related species were converted to the reduced form through reduction with sodium ascorbate. Given the ultra-trace (0.5ppm) level requirements and the lack of UV response in the reduced form, a single quadrupole mass spectrometer (MS) was utilized. In order to implement a highly sensitive MS method in a GMP environment, several approaches were employed to optimize accuracy and robustness including: internal standard correction for drift elimination, six-level standard addition to reduce matrix effects, and weighted linear regression to cover a broad analytical range. The method was fully validated according to ICH guidelines. The method is specific, linear, accurate, precise, and robust within a range of 0.5–100ppm.

Synthesis and application of ion-imprinted polymer nanoparticles for the extraction and preconcentration of copper ions in environmental water samples.

Novel Cu(II) ion-imprinted polymers (Cu-IIP) nanoparticles were prepared by using Cu(II) ion-thiosemicarbazide complex as the template molecule and methacrylic acid, ethylene glycol dimethacrylate (EGDMA), and 2,2'azobisisobutyronitrile (AIBN) as the functional monomer, cross-linker, and the radical initiator, respectively. The synthesized polymer nanoparticles were characterized by using infrared spectroscopy (IR), thermo gravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopic (SEM) techniques. Some parameters such as pH, weight of the polymer, adsorption time, elution time, eluent type, and eluent volume which affect the extraction efficiency of the polymer were studied. In the proposed method, the maximum sorbent capacity of the ion-imprinted polymer was calculated to be 38.8 mg g(-1). The preconcentration factor, relative standard deviation, and limit of detection of the method were found to be 80, 1.7%, and 0.003 μg mL(-1), respectively. The prepared ion-imprinted polymer nanoparticles have an increased selectivity toward Cu(II) ions over a range of competing metal ions with the same charge and similar ionic radius. The method was applied to the determination of ultra trace levels of Cu2+ in environmental water samples with satisfactory results.

Ultra trace level determination of fenoxanil by highly sensitive square wave adsorptive stripping voltammetry in real samples with a renewable silver amalgam film electrode

A new, simple, and highly sensitive voltammetric method for the determination of low concentrations of a novel fungicide, fenoxanil (Fen), was developed using square wave voltammetry (SWV) and square wave adsorptive stripping voltammetry (SWAdSV) on a renewable silver amalgam film electrode (Hg(Ag)FE). The electrochemical reduction of Fen at the Hg(Ag)FE in Britton-Robinson (B-R) buffer at pH 6.8 was studied for the first time. The effect of the supporting electrolyte, pH, conditioning potential and conditioning time, frequency, amplitude, step potential, and accumulation potential and accumulation time were studied to select the optimum experimental conditions. The developed method can determine Fen in the concentration range of 5×10−7–4×10−6molL−1 for SWV and 1×10−10–9×10−10molL−1 for SWAdSV. Validation of the method was carried out. The method was successfully applied for trace level determination of Fen in spiked Warta River water and spiked rice samples by the standard addition method. The interference of common agents and metal ions was also examined. Fen adsorption at the mercury electrode was studied.

Determination of ultratrace-levels of 99Tc in low-level radioactive waste samples using ICP-QMS

This paper proposes a rapid, accurate method of measuring 99Tc in low-level radioactive waste using microwave digestion, TEVA resin for chemical separation, and inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS). The minimum detectable activity of ICP-QMS for the determination of 99Tc was 8.5 mBq g−1 (13.6 pg g−1). The proposed method achieved chemical recovery of 88 % and with sensitivity superior to that of alternative radiochemical methods (e.g., liquid scintillation analyzer or LSA) when the data acquisition time for identical, low-concentration samples was taken into account.

Ultratrace-level determination of N-Nitrosodimethylamine, N-Nitrosodiethylamine, and N-Nitrosomorpholine in waters by solid-phase extraction followed by liquid chromatography-tandem mass spectrometry

AbstractN-nitrosamines are a new class of emerging nitrogenous drinking water disinfection by-products. These compounds are probably carcinogenic which could seriously affect the safety of drinking water consumers. The aim of this study is to develop a simple, fast, and specific analytical method for the routine determination of low part per trillion levels of N-nitrosamines in waters. An ultra high pressure liquid chromatography coupled with tandem mass spectrometry (UHPLC/MS/MS) method was developed for the qualitative and quantitative analysis of N-nitrosamines in waters. N-nitrosamines were extracted, purified and concentrated from water samples in one step using a solid-phase extraction (SPE). The compounds were detected in multiple reaction monitoring via electrospray ionisation source with positive ionisation mode. To achieve symmetrical peak shapes and a short chromatographic analysis time, the mobile phase consisting of acetonitrile, water and formic acid (60:40:0.1, v/v/v) was used in the experiment. Chromatographic separation of N-nitrosamines was done in less than two minutes. All calibration curves had good linearity (r2≥ 0.9989). The intra- and inter-day precision of the assay ranged from 0.59% to 3.11% and accuracy ranged from 99.66% to 104.1%. The mean recoveries of N-nitrosamines in spiked water were 98%-101%. The reproducability was acceptable with relative standard deviations of less than 3.53%. The proposed method yielded detection limits very low which ranges from 0.04 to 0.16 ng L−1. Finally, the developed analytical method was successfully applied to the analysis of N-nitrosamines in natural water sample

A novel electrochemical sensor based on a silver nanoparticle modified carbon ionic liquid electrode for selective and sensitive determination of levetiracetam in pharmaceutical tablets and blood plasma samples

An electrochemical sensor based on a silver nanoparticle (AgNP) modified carbon ionic liquid electrode (CILE) was prepared for the determination of ultra trace levels of levetiracetam (LEV) in human plasma and pharmaceutical tablets. The AgNPs were electrodeposited on the CILE surface using a double pulse potentiostatic technique, which can suitably control the size and morphology of AgNPs electrodeposited on the electrode. The AgNPs deposited on the CILE surface revealed an excellent electrocatalytic activity towards the oxidation of LEV. The sensor exhibited a fast response towards LEV with a linear concentration range of 1–300 ng mL−1 and a limit of detection of 0.7 ng mL−1. The possible interference from several common ions and drugs that usually accompany LEV was tested. The method was successfully applied to the determination of LEV content in real samples such as tablets and human plasma samples with good recovery, and the obtained results were checked by HPLC. The proposed sensor is suitable for routine analysis of LEV in plasma samples to monitor the therapeutic or toxic levels of LEV and for drug pharmacokinetic studies.

Use of core–shell nanoring amino-functionalized superparamagnetic molecularly imprinted polymer for matrix solid phase dispersion extraction and preconcentration of ultratrace levels of BPA from water samples

Determination of ultratrace levels of BPA in water by MSPD with a core–shell nanoring amino-functionalized magnetic molecularly imprinted polymer adsorbent followed by UFLC-MS/MS.

Development of a dynamic headspace - capillary GC - MS method for the determination of ultra-trace levels of vinyl chloride in water samples and during migration studies

A method based on automated dynamic headspace sampling followed by thermal desorption – capillary GC – MS was developed to monitor ultratraces of vinyl chloride in water samples. The method shows excellent performance including a limit of quantification (LOQ) below 10 ng/L, good linearity (r2 > 0.999) in the 10 to 200 ng/L concentration range and an RSD below 10% at all calibration levels. The method was applied to study the release of traces of vinyl chloride monomer (VCM) in water from aged polyvinyl chloride (PVC) pipes installed in water supply systems. A solution to avoid this leaching would be the insertion of a polyethylene pipe inside the PVC pipe provided that vinyl chloride does not permeate through polyethylene. Vinyl chloride migration through a high density polyethylene (HDPE) film was therefore studied with the developed sampling method.

Accurate determination of ultra-trace levels of Ti in blood serum using ICP-MS/MS

Ti is frequently used in implants and prostheses and it has been shown before that the presence of these in the human body can lead to elevated Ti concentrations in body fluids such as serum and urine. As identification of the exact mechanisms responsible for this increase in Ti concentrations, and the risks associated with it, are not fully understood, it is important to have sound analytical methods that enable straightforward quantification of Ti levels in body fluids (for both implanted and non-implanted individuals). Until now, only double-focusing sector field ICP-mass spectrometry (SF-ICP-MS) offered limits of detection that are good enough to deal with the very low basal levels of Ti in human serum. This work reports on the development of a novel method for the accurate and precise determination of trace levels of Ti in human serum samples, based on the use of ICP-MS/MS. O2 and NH3/He have been compared as reaction gases. While the use of O2 did not enable to overcome all spectral interferences, it has been shown that conversion of Ti+ ions into Ti(NH3)6+ cluster ions by using NH3/He as a reaction gas in an ICP-QQQ-MS system, operated in MS/MS mode, provided interference-free conditions and sufficiently low limits of detection, down to 3ngL−1 (instrumental detection limit obtained for the most abundant Ti isotope). The accuracy of the method proposed was evaluated by analysis of a Seronorm Trace Elements Serum L-1 reference material and by comparing the results obtained with those achieved by means of SF-ICP-MS. As a proof-of-concept, the newly developed method was successfully applied to the determination of Ti in serum samples obtained from individuals with and without Ti-based implants. All results were found to be in good agreement with those obtained by means of SF-ICP-MS. The typical basal Ti level in human serum was found to be <1μgL−1, while values in the range of 2–6μgL−1 were observed for implanted patients.

Determination of lead and cadmium using an ionic liquid and dispersive liquid–liquid microextraction followed by electrothermal atomic absorption spectrometry

A procedure for the determination of ultratrace levels of lead and cadmium using dispersive liquid–liquid microextraction followed by electrothermal atomic absorption spectrometry (ETAAS) has been developed. The ionic liquid, 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C8MIm][NTf2]), is formed in situ and used to extract the lead and cadmium complexes with ammonium pyrrolidinedithiocarbamate. The very fine droplets of ([C8MIm][NTf2]) allow effective dispersion without the need for organic solvents. After centrifugation, the concentrations of lead and cadmium in the sedimented phase can be determined by ETAAS. Using a 10mL aqueous sample, the enrichment factor of the procedure was 280 and detection limits of 0.2 and 3ngL−1 were obtained for cadmium and lead, respectively. The relative standard deviations for 10 replicates at the 10ngL−1 cadmium and 0.2μgL−1 lead levels were 6.5 and 7.3%, respectively. The method was successfully applied to the analysis of waters as well as to lixiviates obtained from toys made of plastic materials.

Determination of dioxin-like polychlorinated biphenyls in 1 mL whole blood using programmable temperature vaporization large volume injection coupled to gas chromatogram and high-resolution mass spectrometry

A sensitive method based on programmable temperature vaporization large volume injection coupled to gas chromatogram and high-resolution mass spectrometry (PTV-GC–HRMS) has been developed for the determination of ultra trace levels of dioxin-like polychlorinated biphenyls (DL PCBs) in small amounts of human blood. Blood samples (1mL) were first extracted by column extraction and then purified with column chromatorgraphies. Final extracts (20μL) were introduced to the PTV injector under the solvent vent mode and detected by GC–HRMS (SIM mode). PTV parameters were observed by changing one factor at a time (practical conditions: vent flow: 50mLmin−1, vent pressure: 0kPa and vent time: 0.1min), recoveries of most PCB congeners ranged from 55.1% to 108%, and method detection limits were in the range of 0.11–1.63pgg−1.

Stripping Voltammetric Determination of Uranium in Water Samples Using Hg-Thin Film Modified Multiwall Carbon Nanotube Incorporated Carbon Paste Electrode

The variables affecting determination of ultra trace levels of uranium (VI) in aqueous samples by differential pulse cathodic stripping voltammetry were examined in detail using Hg-thin film modified carbon paste and multiwall carbon nanotube (MWCNT) incorporated carbon paste electrode. Carbon paste electrode prepared in the laboratory was modified with Hg thin film and used as the working electrode. MWCNT was incorporated into the carbon paste for enhancement in sensitivity of the measurements. Electrochemical response for the uranium (VI) reduction peak was found to be well resolved on the thin mercury film modified carbon paste surface and also with the MWCNT modification. Characteristics of the adsorption preconcentration process were investigated using electrochemical impedance measurements. Electrochemical signals were observed to be enhanced on MWCNT modification of the carbon paste.

Ultra trace quantification of chromium(VI) in food and water samples by highly sensitive catalytic adsorptive stripping voltammetry with rubeanic acid

Abstract A simple and highly selective and sensitive catalytic adsorptive stripping voltammetric procedure for determination of ultra trace levels of chromium(VI) on hanging mercury drop electrode is reported. The method is based on the adsorptive preconcentration of the Cr(III)–dithiooxamide (rubeanic acid) complex and the utilization of the catalytic reaction in the presence of nitrate. At optimized conditions the calibration graph is linear from 0.01 to 6 ng/ml and detection limit is 0.002 ng/ml for accumulation time of 50 s. The interference of some common ions was studied and this method has been applied to the determination of chromium in food and waste water samples with satisfactory results.

Solid phase separation and ICP-OES/ICP-MS determination of rare earth impurities in nuclear grade uranium oxide

A simple, effective and low cost solid phase extraction procedure was standardized for the trace and ultra-trace level determination of rare earth impurities, such as, Ce, Dy, Sm, Gd, Eu, Er etc. which act as neutron poisons, in nuclear grade uranium oxide (U3O8 > 99.9% by weight). The method involves selective separation of these elements as their fluorides with the help of activated charcoal from major uranium matrix followed by determination by ICP-MS and high resolution ICP-OES. The residual uranium content of the solution was <10 μg/mL. The recovery of REEs ranges from 85 to 105%. The method was validated with nuclear grade uranium oxide standards CRM-I to CRM-V (BARC, Mumbai, India) in addition to some synthetic standards. The RSD of the method was ±12% (n = 3).

Dissolved inorganic antimony, selenium and tin species in water samples from various sampling sites of river vardar in Macedonia and Greece

A highly effective liquid phase semi-microextraction procedure was applied for determination ofultra trace levels of dissolved inorganic species of antimony, tin and selenium in river Vardar (from the 2ndup to 420th km of the river) and its tributaries Crna Reka, Treska, Bregalnica, Pchinja and Lepenec usingelectrothermal atomic absorption spectrometry (ETAAS) for quantification. The concentrations for totaldissolved inorganic antimony were between 6 and 242 ng/l Sb, for Sn(II, IV) – in the range of 2.7–61 ng/lSn and for Se(IV, VI) – in the range of 15–75 ng/l Se. The higher oxidation states of antimony and seleniumwere found as the predominant form in the studied surface waters.

Rapid and interference free determination of ultra trace level of uranium in potable water originating from different geochemical environments by ICP-OES

Direct determination of uranium in the concentration range of 8 μg L−1 to mg L−1 in water samples originating from different geochemical environments has been done using Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). Uranium detection with 2–3% RSD (relative standard deviation) has been achieved in water samples by optimizing the plasma power, argon and sheath gas flow. These parameters were optimized for three different emission lines of uranium at 385.958, 409.014 and 424.167 nm. Interference arising due to the variation in concentration of bicarbonate, sodium chloride, calcium chloride, Fe and dissolved organic carbon (DOC) on the determination of uranium in water samples was also cheeked as these are the elements which vary as per the prevailing geochemical environment in groundwater samples. The concentration of NaHCO3, CaCl2 and NaCl in water was varied in the range 0.5–2.0%; whereas Fe ranged between 1 and 10 μg mL−1 and DOC between 0.1–1%. No marked interference in quantitative determination of uranium was observed due to elevated level of NaHCO3, CaCl2 and NaCl and Fe and DOC in groundwater samples. Concentration of uranium was also determined by other techniques like adsorptive striping voltametry (AdSv); laser fluorimetry and alpha spectrometry. Results indicate distinct advantage for uranium determination by ICP-OES compare to other techniques.