An accurate determination method for cobalt in sage tea and cobalamin: Slotted quartz tube-flame atomic absorption spectrometry after preconcentration with switchable liquid-liquid microextraction using a Schiff base.

This study reports a stepwise optimization of switchable liquid-liquid microextraction (SLLME) for cobalt determination by flame atomic absorption spectrometry (FAAS) coupled with a slotted quartz tube (SQT). The main purpose of this study was to develop an accurate and sensitive analytical method for cobalt. Extraction method was used to separate and preconcentrate cobalt from sage tea and vitamin B12 samples after complexing with a Schiff base ligand. 107.7 folds enhancement in detection power under the optimum conditions was recorded with respect to direct FAAS. This enhancement correlated to 3.1 µg/L limit of detection and 10 µg/L limit of quantification. The SLLME-SQT-FAAS method was linear over a broad concentration range and low %RSD values established high precision for the method. Appreciable percent recovery results (94-108%) obtained from spiked sage sample and from cobalamin also validated the accuracy of the method.

A green, accurate and sensitive analytical method based on vortex assisted deep eutectic solvent-liquid phase microextraction for the determination of cobalt by slotted quartz tube flame atomic absorption spectrometry.

Preconcentration of cobalt was carried out with deep eutectic solvent based liquid phase microextraction (DES-LPME) for trace determination by a slotted quartz tube (SQT) attached flame atomic absorption spectrometry (FAAS) system. Choline chloride and phenol in a 1:2 M ratio was used as a green solvent to extract cobalt from the aqueous sample solution. Key parameters influencing the extraction efficiency of cobalt were examined and optimized. Under the conditions optimized, the linear dynamic range was found between 5.0 and 50 µg L-1, and the limits of detection and quantification (LOD and LOQ) were calculated as 2.0 and 6.6 µg L-1, respectively. The detection power of the conventional FAAS was improved upon by 67 folds using the optimized DES-LPME-SQT-FAAS method. The developed analytical method was successfully applied for the determination of cobalt in linden tea samples and the recovery results obtained for different spiked concentrations (20, 30 and 40 µg L-1) were remarkable (≈100%).

Accurate and sensitive determination of lead in black tea samples using cobalt magnetic particles based dispersive solid-phase microextraction prior to slotted quartz tube-flame atomic absorption spectrometry.

Newly developed combination of magnetic cobalt particles based dispersive solid-phase microextraction (Co-MP-DSPME) and slotted quartz tube attached flame atomic absorption spectrometry (SQT-FAAS) was utilized to determine lead at trace levels in tea samples. Co-MPs' adsorbent properties were tested and validated for their selectiveness to lead. Only with a few and short extraction steps (i.e. adding MPs, mixing, decanting and eluting) analyte was extracted from sample solution rapidly and efficiently. Limit of detection (LOD) and limit of quantification (LOQ) for the developed method (Co-MP-DSPME-SQT-FAAS) were found to be 7.77 µg/L and 25.9 µg/L, respectively. Matrix matching strategy was performed and outcomes indicated that the developed method is applicable with the high percent recovery values of 110.1 ±â€¯4.5 and %102.9 ±â€¯4.2 for 100 and 300 µg/kg lead standard spiked black tea samples, respectively. The method was also applied to standard reference material to check the accuracy of the method.

Multivariate optimization of ultrasound-assisted extraction using Doehlert matrix for simultaneous determination of Fe and Ni in vegetable oils by high-resolution continuum source graphite furnace atomic absorption spectrometry.

A method for simultaneous determination of Fe (232.036 nm) and Ni (232.195 nm) in vegetable oil samples by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) after an acid extraction of the analytes is proposed. In the extraction step, hydrochloric, nitric and acetic acid solutions were tested. The optimization of the procedure was performed by applying Doehlert matrix, and multiple response was used for simultaneous evaluation of the performance of the extraction. The optimum conditions were: extraction time of 17 min, extraction temperature of 39 °C and sonication amplitude of 42%, employing 0.5 mol L-1 HCl as the extracting solvent. The limits of quantification were 60 and 160 ng g-1 for Fe and Ni, respectively. The method was applied to the analysis of vegetable oil samples and the results were compared with a method employing inductively coupled plasma optical emission spectrometry (ICP OES).

Inductively Coupled Plasma Mass Spectrometry (ICP-MS) Applications in Quantitative Proteomics.

Recent advances in inductively coupled plasma mass spectrometry (ICP-MS) hyphenated to different separation techniques have promoted it as a valuable tool in protein/peptide quantification. These emerging ICP-MS applications allow absolute quantification by measuring specific elemental responses. One approach quantifies elements already present in the structure of the target peptide (e.g. phosphorus and sulphur) as natural tags. Quantification of these natural tags allows the elucidation of the degree of protein phosphorylation in addition to absolute protein quantification. A separate approach is based on utilising bi-functional labelling substances (those containing ICP-MS detectable elements), that form a covalent chemical bond with the protein thus creating analogs which are detectable by ICP-MS. Based on the previously established stoichiometries of the labelling reagents, quantification can be achieved. This technique is very useful for the design of precise multiplexed quantitation schemes to address the challenges of biomarker screening and discovery. This review discusses the capabilities and different strategies to implement ICP-MS in the field of quantitative proteomics.

Application of laser microdissection ICP-MS for high resolution elemental mapping in mouse brain tissue: a comparative study with laser ablation ICP-MS.

Mapping of elements in biological tissue by laser induced mass spectrometry is a fast growing analytical methodology in life sciences. This method provides a multitude of useful information of metal, nonmetal, metalloid and isotopic distribution at major, minor and trace concentration ranges, usually with a lateral resolution of 12-160 µm. Selected applications in medical research require an improved lateral resolution of laser induced mass spectrometric technique at the low micrometre scale and below. The present work demonstrates the applicability of a recently developed analytical methodology - laser microdissection associated to inductively coupled plasma mass spectrometry (LMD ICP-MS) - to obtain elemental images of different solid biological samples at high lateral resolution. LMD ICP-MS images of mouse brain tissue samples stained with uranium and native are shown, and a direct comparison of LMD and laser ablation (LA) ICP-MS imaging methodologies, in terms of elemental quantification, is performed.

A coupling system of capillary gel electrophoresis with inductively coupled plasma-mass spectrometry for the determination of double stranded DNA fragments.

The coupling system of capillary gel electrophoresis (CGE) and inductively coupled plasma-mass spectrometry (ICP-MS) was newly developed and successfully applied to the double-stranded (ds) DNA quantification. The developed system combines the separation technique for large biomolecules and element selective detection of ICP-MS. This coupling was achieved by using the modified high performance concentric nebulizer (HPCN) with the PTFE tube (HPCN-PT), which can produce the liquid jet by the flow focusing effect. The HPCN-PT effectively nebulizes the highly viscous solution containing gel buffer even at a low flow rate. At a liquid flow rate of 0.010 mL min(-1) and a nebulizer gas flow rate of 1 L min(-1), the Sauter mean diameter (D3,2) of primary aerosols generated by the HPCN-PT was 3.4 µm, and over 90% (v/v) of the aerosol droplets were less than 10 µm in diameter. The electrophoresis capillary filled with gel buffer was connected to the HPCN-PT via the interface. This interface has two connectors and an electrode that can connect CE and ICP-MS. After the electrophoretic separation at atmospheric pressure, the samples were transferred to the ICP-MS through the interface by applying additional pressure. Fragments of dsDNA, which were commercially available as a ladder marker solution, were successfully separated and analyzed by measuring (31)P(+) with CGE-ICP-MS, and a linear calibration curve of the phosphorus standard solution (R(2) = 0.999) was obtained from 2.7 to 27 mg kg(-1). The detection limit (LOD) and absolute detection limit of P were 3.7 µg kg(-1) and 0.6 pg (equivalent to 6 pg of DNA), respectively. This absolute detection limit value was equal to the conventional fluorescence determination of DNA.

Determination of zinc and copper in edible plants by nanometer silica coated, slotted quartz tube, flame atomic absorption spectrometry.

Nanometer SiO(2) was coated onto the inner wall of a slotted quartz tube atomizer (STAT) and then was used as a new atomizer (NSC- STAT) for the determination of Zn and Cu by flame atomic absorption spectrometry (FAAS). Compared to conventional STAT-FAAS, the analytical performance of NSC-STAT-FAAS was improved as follows: (a) the linear range of calibration curves was expanded from 30.0-200.0 ng mL(-1) to 5.0-400.0 ng mL(-1) for Zn, and from 100.0-1000.0 ng mL(-1) to 50.0-2000.0 ng mL(-1) for Cu; and (b) the characteristic concentration was decreased from 6.0 ng mL(-1)/1% to 2.7 ng mL(-1)/1% for Zn and from 25.0 ng mL(-1)/1% to 10.1 ng mL(-1)/1% for Cu. NSC-STAT-FAAS was applied for the determination of Zn and Cu in edible plants, including herbal medicine, marine algae, tomato leaves (NIST 1573), and apple leaves (NIST 1515).

[Electrothermal atomic absorption determination of arsenic in plants and plant products].

The authors have developed the optimal temperature-time parameters of electrothermal atomic absorption determination of arsenic in plants after their acid predigestion. The matrix modifier is 1% nickel nitrate or palladium nitrate solution. Cuvettes (ovens) are simple, made of porous or pyrolytic graphite. The analytical program is suitable for both spectrometers with Zeeman and deuterium background correction. The correctness of the procedure has been estimated from the results of analysis of state reference samples certified for their arsenic content. The coefficient of variation was 20-35% for the concentration range of 0.02-0.2 mg/kg.

Automatic flow-batch system for cold vapor atomic absorption spectroscopy determination of mercury in honey from Argentina using online sample treatment.

An automatic flow-batch system that includes two borosilicate glass chambers to perform sample digestion and cold vapor atomic absorption spectroscopy determination of mercury in honey samples was designed. The sample digestion was performed by using a low-cost halogen lamp to obtain the optimum temperature. Optimization of the digestion procedure was done using a Box-Behnken experimental design. A linear response was observed from 2.30 to 11.20 µg Hg L(-1). The relative standard deviation was 3.20% (n = 11, 6.81 µg Hg L(-1)), the sample throughput was 4 sample h(-1), and the detection limit was 0.68 µg Hg L(-1). The obtained results with the flow-batch method are in good agreement with those obtained with the reference method. The flow-batch system is simple, allows the use of both chambers simultaneously, is seen as a promising methodology for achieving green chemistry goals, and is a good proposal to improving the quality control of honey.

Determination of selenium in serum samples of preterm newborn infants with bronchopulmonary dysplasia using a validated hydride generation system.

Bronchopulmonary dysplasia (BPD), also known as chronic lung disease, is one of the most challenging complications in premature newborn infants. Selenium plays a role in antioxidant system by protecting cell membranes and neutralizing the deleterious effects of free radicals. The aim of this study was to determine the relationship between selenium concentration and incidence of bronchopulmonary dysplasia using a validated analytical method. Umbilical cord blood and blood samples 30 days after the birth were collected from 38 preterm newborn infants with gestation age of 32 weeks or less, and the separated serums were kept at -70°C until analysis time. Selenium concentration of serum was determined using an atomic absorption spectrophotometer. The method was validated on the basis of standard validation techniques. The analytical method was linear in the range of 1 to 500 µg/L with the limit of detection of 0.4 µg/L. Samples were collected from 38 infants whose gestation age was 32 weeks or less. The blood samples were collected from the umbilical cord blood at birth in 19 cases. In 25 cases, blood samples were collected 1 month after birth. Of the 15 patients diagnosed with BPD, 10 were boys (p = 0.02). The mean serum selenium concentration was not different at birth between patients with and without BPD, but it was significantly lower at 30 days after birth in patients with BPD (38.5 ± 14.1vs. 45.4 ± 18.7 µg/L, p = 0.02). Preterm newborn infants with BPD had lower serum selenium concentrations 1 month after birth.

Review of analytical methods for the quantification of iodine in complex matrices.

Iodine is an essential element of human nutrition. Nearly a third of the global population has insufficient iodine intake and is at risk of developing Iodine Deficiency Disorders (IDD). Most countries have iodine supplementation and monitoring programs. Urinary iodide (UI) is the biomarker used for epidemiological studies; only a few methods are currently used routinely for analysis. These methods either require expensive instrumentation with qualified personnel (inductively coupled plasma-mass spectrometry, instrumental nuclear activation analysis) or oxidative sample digestion to remove potential interferences prior to analysis by a kinetic colorimetric method originally introduced by Sandell and Kolthoff ~75 years ago. The Sandell-Kolthoff (S-K) method is based on the catalytic effect of iodide on the reaction between Ce(4+) and As(3+). No available technique fully fits the needs of developing countries; research into inexpensive reliable methods and instrumentation are needed. There have been multiple reviews of methods used for epidemiological studies and specific techniques. However, a general review of iodine determination on a wide-ranging set of complex matrices is not available. While this review is not comprehensive, we cover the principal developments since the original development of the S-K method.

Simultaneous quantitative analysis of arsenic, bismuth, selenium, and tellurium in soil samples using multi-channel hydride-generation atomic fluorescence spectrometry.

The basic principles and the application of hydride-generation multi-channel atomic fluorescence spectrometry (HG-MC-AFS) in soil analysis are described. It is generally understood that only one or two elements can be simultaneously detected by commonly used one- or two-channel HG-AFS. In this work, a new sample-sensitive and effective method for the analysis of arsenic, bismuth, tellurium, and selenium in soil samples by simultaneous detection using HG-MC-AFS was developed. The method detection limits for arsenic, bismuth, tellurium, and selenium are 0.19 µg/g, 0.10 µg/g, 0.11 µg/g, and 0.08 µg/g, respectively. This method was successfully applied to the simultaneous determination of arsenic, bismuth, tellurium, and selenium in soil samples.

Determination of mercury and selenium in herbal medicines and hair by using a nanometer TiO2-coated quartz tube atomizer and hydride generation atomic absorption spectrometry.

The nanometer TiO(2) particle was coated onto the inner wall of a T-shaped quartz tube atomizer (QTA) and then was used as a new atomizer (NT-QTA) for the determination of Hg and Se by hydride generation atomic absorption spectrometry (HGAAS). After coating 67.4 mg TiO(2) on a quartz tube, the analytical performance of NT-QTA-HGAAS was compared to conventional QTA-HGAAS and it was improved as follows: (a) the linear range of the calibration curves was expanded from 10.0-80.0 ng mL(-1) to 5.0-150.0 ng mL(-1) for Hg, and from 10.0-70.0 ng mL(-1) to 5.0-100.0 ng mL(-1) for Se; (b) the characteristic concentration of was decreased from 2.8 ng mL(-1)/1% to 1.1 ng mL(-1)/1% for Hg and from 1.2 ng mL(-1)/1% to 0.8 ng mL(-1)/1% for Se; and (c) the interference from the coexistence of As on the determination of Hg and Se could be eliminated. The achieved technique was applied for the determination of Hg and Se in herbal medicines and hair.

Improvement of AOAC Official Method 984.27 for the determination of nine nutritional elements in food products by Inductively coupled plasma-atomic emission spectroscopy after microwave digestion: single-laboratory validation and ring trial.

A single-laboratory validation (SLV) and a ring trial (RT) were undertaken to determine nine nutritional elements in food products by inductively coupled plasma-atomic emission spectroscopy in order to improve and update AOAC Official Method 984.27. The improvements involved optimized microwave digestion, selected analytical lines, internal standardization, and ion buffering. Simultaneous determination of nine elements (calcium, copper, iron, potassium, magnesium, manganese, sodium, phosphorus, and zinc) was made in food products. Sample digestion was performed through wet digestion of food samples by microwave technology with either closed or open vessel systems. Validation was performed to characterize the method for selectivity, sensitivity, linearity, accuracy, precision, recovery, ruggedness, and uncertainty. The robustness and efficiency of this method was proved through a successful internal RT using experienced food industry laboratories. Performance characteristics are reported for 13 certified and in-house reference materials, populating the AOAC triangle food sectors, which fulfilled AOAC criteria and recommendations for accuracy (trueness, recovery, and z-scores) and precision (repeatability and reproducibility RSD and HorRat values) regarding SLV and RT. This multielemental method is cost-efficient, time-saving, accurate, and fit-for-purpose according to ISO 17025 Norm and AOAC acceptability criteria, and is proposed as an improved version of AOAC Official Method 984.27 for fortified food products, including infant formula.

Determination of phosphorus, sulfur and the halogens using high-temperature molecular absorption spectrometry in flames and furnaces--A review.

The literature about the investigation of molecular spectra of phosphorus, sulfur and the halogens in flames and furnaces, and the use of these spectra for the determination of these non-metals has been reviewed. Most of the investigations were carried out using conventional atomic absorption spectrometers, and there were in essence two different approaches. In the first one, dual-channel spectrometers with a hydrogen or deuterium lamp were used, applying the two-line method for background correction; in the second one, a line source was used that emitted an atomic line, which overlapped with the molecular spectrum. The first approach had the advantage that any spectral interval could be accessed, but it was susceptible to spectral interference; the second one had the advantage that the conventional background correction systems could be used to minimize spectral interferences, but had the problem that an atomic line had to be found, which was overlapping sufficiently well with the maximum of the molecular absorption spectrum. More recently a variety of molecular absorption spectra were investigated using a low-resolution polychromator with a CCD array detector, but no attempt was made to use this approach for quantitative determination of non-metals. The recent introduction and commercial availability of high-resolution continuum source atomic absorption spectrometers is offering completely new possibilities for molecular absorption spectrometry and its use for the determination of non-metals. The use of a high-intensity continuum source together with a high-resolution spectrometer and a CCD array detector makes possible selecting the optimum wavelength for the determination and to exclude most spectral interferences.

Determination of nickel, calcium and magnesium in xylem sap by flame atomic absorption spectrometry using a microsampling technique.

INTRODUCTION: Knowledge of xylem sap chemical composition is important to the understanding of translocation, detoxification and tolerance mechanisms. However, the small amount of sample available often hampers its characterisation. Hence, low volume consumption techniques are needed for xylem sap analysis. OBJECTIVE: To develop a microsampling technique for the determination of elements in xylem sap from different plants by flame atomic absorption spectrometry (FAAS). METHODOLOGY: The microsampling device was optimised in terms of sample volume and integration time. The analytical characteristics of the microsampling technique (micro-FAAS) were established and compared with those of FAAS with traditional continuous nebulisation. The method was validated by means of an independent technique. RESULTS: Ca, Mg and Ni were determined in a 50 microL aliquot of xylem sap solution/element that was introduced directly into the flame via the microsampling accessory. Good precision was obtained with relative standard deviations of 1.1, 0.6 and 2.3% for Ca, Mg and Ni, respectively. Matrix effects resulting from the physical characteristics of the samples and possible chemical interferences caused by phosphate and/or sulphate were ruled out. CONCLUSION: A simple, rapid and reproducible microsampling technique coupled to FAAS was developed and successfully applied in the determination of Ca, Mg and Ni in xylem sap.

Interlaboratory validation of the Mehlich 3 method for extraction of plant-available phosphorus.

The Mehlich 3 (M3) method is widely used for extraction of plant-available phosphorus (P) from soil over a wide range of pH values. The method is also used by many laboratories to determine multiple plant-available nutrients simultaneously. However, this method has not been statistically validated within and among laboratories. The objective of this study was to determine the repeatability (within-laboratory performance) and reproducibility (among-laboratories performance) of the M3 method by using a wide variety of soils. An in-house homogeneity test was conducted for 10 soils. Three replicates of each of the 10 soils were sent to 26 domestic and international laboratories primarily for P analysis. Samples were scooped, weighed, or both scooped and weighed for extraction. The P in extracts was quantified by the participating laboratories by using inductively coupled plasma-atomic emission spectrometry (ICP-AES) or colorimetrically. For the scooped samples analyzed colorimetrically, the repeatability relative standard deviation (RSDr) ranged from 2.07 to 12.1%; the RSDr ranged from 2.2 to 21.4% for the scooped samples analyzed by ICP-AES. For the weighed samples analyzed colormetrically, the RSDr values were 1.09-9.34%, and for the weighed samples analyzed by ICP-AES, they were 1.70-5.76%. For the reproducibility data, the RSDR values ranged from 6.85 to 50.8% for the scooped-colorimetry category, from 6.95 to 73.9% for the scooped-ICP-AES category, from 7.19 to 42.6% for the weighed-colorimetry category, and from 5.29 to 35.9% for the weighed-ICP-AES category. The greatest RSD values were associated with the Susitna soil, which had the smallest concentration of extractable P. Because of the relatively small concentration of P in this soil, the laboratories were attempting to measure solution concentrations that were close to the detection limits. The Horwitz ratios (HorRat) were also used to evaluate the repeatability, HorRat(r), and reproducibility, HorRat(R). Overall, the M3 P method appears to be both repeatable and reproducible across the 4 categories, and the vast majority of the HorRat values for both repeatability and reproducibility were within the acceptable range. The results of this study indicate that the M3 P method for the determination of plant-available P in soil is both accurate and precise when standardized procedures are used. The method has been shown to be suitable for use as a reference method for testing soil materials for extractable P.

Taguchi OA16 orthogonal array design for the optimization of cloud point extraction for selenium determination in environmental and biological samples by tungsten-modified tube electrothermal atomic absorption spectrometry.

Orthogonal array design (OAD) was applied for the first time to optimize cloud point extraction (CPE) conditions for Se(IV) determination by electrothermal atomic absorption spectrometry (ETAAS) in environmental and biological samples. Selenium was reacted with o-phenylenediamine to form piazselenol in an acidic medium (pH 2). Using Triton X-114, as surfactant, piazselenol was quantitatively extracted into small volume (about 30 microL) of the surfactant-rich phase after centrifugation. Five relevant factors, i.e. surfactant concentration, pH, ionic strength, equilibrium time and temperature were selected and the effects of each factor were studied at four levels on the extraction efficiency of Se(IV) and optimized. The statistical analysis revealed that the most important factors contributing to the extraction efficiency are ionic strength, pH and percent of surfactant. Based on the results obtained from the analysis of variance (ANOVA), the optimum conditions for extraction were established as: pH 6; vial temperature=50 degrees C; extraction time=7 min and 0.3% (w/v) of Triton X-114. The method was permitted to obtain a detection limit of 0.09 ng mL(-1) and two linear calibration ranges from 0.6 to 1.0 and 1.0 to 80.0 ng mL(-1) Se. The precision (%RSD) of the extraction and determination for the six replicates of Se at 20 ng mL(-1) was better than 3.6% and the enrichment factor of 63.5 was achieved. The studied analyte was successfully extracted and determined with high efficiency using cloud point extraction method in water and biological matrices.

Flow injection-hydride generation atomic absorption spectrometric determination of selenium, arsenic and bismuth.

A simple and robust flow injection system which permits low sample and reagent consumption is described for rapid and reliable hydride generation atomic absorption spectrometric determination of selenium, arsenic and bismuth. The system, which composed of one peristaltic pump and one four channel solenoid valve, used water as the carrier streams for both sample and NaBH(4) solution. Rapid off-line pre-reduction of the analytes was achieved by using hydroxylamine hydrochloride for selenium and a mixture of potassium iodide and ascorbic acid for arsenic and bismuth. Transition metal interference was eliminated with the addition of thiourea and EDTA into the NaBH(4) solution and significant sensitivity enhancement was observed for selenium in the presence of thiourea in the reductant solution. Under optimised conditions, the method achieved detection limits of 0.2 ng mL(-1) for Se, 0.5 ng mL(-1) for As and 0.3 ng mL(-1) for Bi. The method was very reproducible, achieving relative standard deviations of 6.3% for Se, 3.6% for As and 4.7% for Bi, and has a sample throughput of 360 h(-1). Successful application of the method to the quantification of selenium, arsenic and bismuth in a certified reference river sediment sample is reported.