A simple method using on-line continuous leaching and ion exchange chromatography coupled to inductively coupled plasma mass spectrometry for the speciation analysis of bio-accessible arsenic in rice

A simple method for the speciation analysis of bio-accessible arsenic (As) in rice was developed using a continuous on-line leaching method to release the bio-accessible fraction. The continuous on-line leaching method has several advantages over commonly used batch methods including quicker and easier sample preparation, reduced risk of contamination and access to real time leaching data. The bio-accessibility of As in the samples was monitored using inductively coupled plasma mass spectrometry (ICP-MS). Results from a certified reference material as well as cooked and uncooked white rice showed that the majority of As was leached by saliva. Results obtained using the continuous on-line leaching method were comparable to those obtained using a batch method. Speciation analysis of the saliva leachate was performed using ion exchange chromatography coupled to ICP-MS. The four most toxic forms of As (As(III), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and As(V)) were clearly separated within 5 min in a single chromatographic run. Over 92% of bio-accessible As in the certified reference material and uncooked white rice sample was in the form of DMA and As(V), whereas it was present as DMA and As(III) in the cooked white rice.     

Estimation of the bio-accessible fraction of Cr,As, Cd and Pb in locally available bread using on-line continuous leaching method coupled to inductively coupled plasma mass spectrometry

A previously developed, efficient and simple on-line leaching method was used to assess the maximum bio-accessible fraction (assuming no synergistic effect from other food and beverage) of potentially toxic elements (Cr, As, Cd and Pb) in whole wheat brown and white bread samples. Artificial saliva, gastric juice and intestinal juice were successively pumped into a mini-column, packed with bread (maintained at 37 °C) connected on-line to the nebulizer of an inductively coupled plasma mass spectrometry (ICP-MS) instrument equipped with a collision-reaction interface (CRI) using hydrogen as reaction gas to minimize carbon- and chlorine-based polyatomic interferences. In contrast to the conventional batch method to which it was compared, this approach provides real-time monitoring of potentially toxic elements that are continuously released during leaching. Mass balance for both methods was verified at the 95% confidence level. Results obtained from the whole wheat brown and white bread showed that the majority of Cr, Cd and Pb was leached by gastric juice but, in contrast, the majority of As was leached by saliva. While there was higher total content for elements in whole wheat bread than in white bread, a higher percentage of elements were bio-accessible in white bread than in whole wheat bread. Both the on-line and batch methods indicate that 40–98% of toxic elements in bread samples are bio-accessible. While comparison of total analyte concentrations with provisional tolerable daily intake values may indicate some serious health concern for children, when accounting for the bio-accessibility of these elements, bread consumption is found to be safe for all ages.     

Capillary electrophoresis with inductively coupled plasma-mass spectrometric and electrospray time of flight mass spectrometric detection for the determination of arsenic species in fish samples

CE was coupled to inductively coupled plasma MS (ICP-MS) and ESI-MS to identify and quantify the arsenic species arsenobetaine (AsB), arsenite (As(III)), arsenate (As(V)), and dimethylarsinic acid (DMA). A GC-flame ionization detector (FID)-based German standard method and ICP-MS were used for validation of the data obtained for arsenobetaine and total arsenic, respectively. LODs obtained with the CE-ESI-TOF-MS method were 1.0x10(-7) M for AsB, 5.0x10(-7) M for DMA, and 1.0x10(-6) M for As(III) and As(V). For the CE-ICP-MS method, LODs were 8.5x10(-8) M for AsB, 9.5x10(-8) M for DMA, 9.3x10(-8) M for As(III), and 6.2x10(-8) M for As(V). While CE-ICP-MS provided high sensitivity and better reproducibility for quantitative measurements, CE-ESI-MS with a TOF mass analyzer proved to be valuable for species identification. With this setup, fish samples were prepared and analyzed and the obtained data were successfully validated with the independent methods.     

Total arsenic determination and speciation in infant food products by ion chromatography-inductively coupled plasma-mass spectrometry

Health risk associated with dietary arsenic intake may be different for infants and adults. Seafood is the main contributor to arsenic intake for adults while terrestrial-based food is the primary source for infants. Processed infant food products such as rice-based cereals, mixed rice/formula cereals, milk-based infant formula, applesauce and puree of peaches, pears, carrots, sweet potatoes, green beans, and squash were evaluated for total and speciated arsenic content. Arsenic concentrations found in rice-based cereals (63-320 ng/g dry weight) were similar to those reported for raw rice. Results for the analysis of powdered infant formula by inductively coupled plasma-mass spectrometry (ICP-MS) indicated a narrow and low arsenic concentration range (12 to 17 ng/g). Arsenic content in puree infant food products, including rice cereals, fruits, and vegetables, varies from <1 to 24 ng/g wet weight. Sample treatment with trifluoroacetic acid at 100 degrees C were an efficient and mild method for extraction of arsenic species present in different food matrixes as compared to alternative methods that included sonication and accelerated solvent extraction. Extraction recoveries from 94 to 128% were obtained when the summation of species was compared to total arsenic. The ion chromatography (IC)-ICP-MS method selected for arsenic speciation allowed for the quantitative determination of inorganic arsenic [As(III) + As(V)], dimethylarsinic acid (DMA), and methylarsonic acid (MMA). Inorganic arsenic and DMA are the main species found in rice-based and mixed rice/formula cereals, although traces of MMA were also detected. Inorganic arsenic was present in freeze-dried sweet potatoes, carrots, green beans, and peaches. MMA and DMA were not detected in these samples. Arsenic species in squash, pears, and applesauce were not detected above the method detection limit [5 ng/g dry weight for As(III), MMA, and DMA and 10 ng/g dry weight for As(V)].     

Determination of arsenic compounds in beverages by high-performance liquid chromatography-inductively coupled plasma mass spectrometry

Arsenic compounds including arsenous acid (As(III)), arsenic acid (As(V)), dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) were separated by high-performance liquid chromatography (HPLC) and detected by inductively coupled plasma mass spectrometry (ICP-MS). A Hamilton PRX-100 anionic-exchange column and a pH 8.5 K₂HPO₄/KH₂PO₄ 5.0 × 10⁻³ mol L⁻¹ mobile phase were used to achieve arsenic speciation. The separation of arsenic species provided peaks of As(III) at 2.75 min, DMA at 3.33 min, MMA at 5.17 min and As(V) at 12.5 min. The detection limits, defined as three times the standard deviation of the lowest standard measurements, were found to be 0.2, 0.2, 0.3 and 0.5 ng mL⁻¹ for As(III), DMA, MMA and As(V), respectively. The relative standard deviation values for a solution containing 5.0 μg L⁻¹ of As(III), DMA, MMA and As(V) were 1.2, 2.1, 2.5 and 3.0%, respectively. This analytical procedure was applied to the speciation of arsenic compounds in drinking (soft drink, beer, juice) samples. The validation of the procedure was achieved through the analysis of arsenic compounds in water and sediment certified reference materials.     

胆汁返流性胃炎病入血清和胃液中锌、铜、铁、钙含量及意义

采用火焰原子吸收法检测了36例胆汁运流性胃炎病人和30例健康对照者血清和胃液中微量元素Zn、Cu、Fe、及Ca的含量。结果显示，胆汁返流组血清Zn、Cu、Fe含量均明显低于对照组；胃液中Zn、Cu、含量则明显高于对照组；血清和胃液中Ca含量在2组间未见明显差异。该研究为开展胆汁返流性胃炎的病因学和治疗学研究提供了有益的资料。     

Distribution of arsenic species in environmental samples collected in Northern Chile

Gradient ion chromatographic separation coupled with ICP-MS was used to resolve and determine the most common arsenic species in environmental and biological samples of carrots, trout, soil, sediment and river water from Region II of Chile. The carrot and trout samples showed a concentration of 49 and 168 µg g^?1, respectively, of total As. Both concentrations are high considering the basal level. In the carrots, percentage of 45 and 31% of total As were found for As(III) and As(V) species, respectively. In the trout, the higher concentration related to AsB at 39% of the total As. As(III) and DMA were also present in relatively high concentrations. The River Loa and the soil in which the carrots are growing also present very high As(V) concentrations of 100 and 17 µg g^?1, respectively. The ratio between the concentration for the same As species found in the living organisms (carrots and trout) and the environment in which they grow (soil and water) can provide important information about the possible absorption or biotransformation of As species in living beings. As(III) and DMA are the species in which the greatest accumulation occurs with respect to the medium in which they are present, and biotransformation also appears to take place.     

Simultaneous separation and determination of six arsenic species in rice by anion‐exchange chromatography with inductively coupled plasma mass spectrometry

The simultaneous separation and determination of arsenite As(III), arsenate As(V), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AsB), and arsenocholine (AsC) in rice samples have been carried out in one single anion‐exchange column run by high‐performance liquid chromatography with inductively coupled plasma mass spectrometry. To estimate the effect of variables on arsenic (As) speciation, the chromatographic conditions including type of competing anion, ionic strength, pH of elution buffer, and flow rate of mobile phase have been investigated by a univariate approach. Under the optimum chromatographic conditions, baseline separation of six As species has been achieved within 10 min by gradient elution program using 4 mM NH₄HCO₃ at pH 8.6 as mobile phase A and 4 mM NH₄HCO₃, 40 mM NH₄NO₃ at pH 8.6 as mobile phase B. The method detection limits for As(III), As(V), MMA, DMA, AsB, and AsC were 0.4, 0.9, 0.2, 0.4, 0.5, and 0.3 μg/kg, respectively. The proposed method has been applied to separation and quantification of As species in real rice samples collected from Hunan Province, China. The main As species detected in all samples were As(III), As(V) and DMA, with inorganic As accounting for over 80% of total As in these samples.     

Cathodic stripping voltammetric analysis of arsenic species in environmental water samples

A simple, fast and sensitive arsenic speciation method has been developed for environmental water analysis by using differential pulse cathodic stripping voltammetry (CSV) performed on a hanging mercury drop electrode (HMDE). Electroactive As(III) is determined by direct CSV analysis. As(V) is converted to As(III) species first and is subsequently quantified by the concentration difference between total inorganic arsenic and As(III). A new batch-mode As(V) reduction procedure by l-cysteine was developed in this study. The optimized parameters for quantitative As(V) reduction include treatment with 20 mM l-cysteine and 0.03 M HCl for 6 min at 70 °C. Organic arsenic, including monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), can be decomposed to As(V) through UV photooxidation with peroxydisulfate and quantified through subtracting total inorganic arsenic from the total arsenic. At optimum condition, the detection limits for As(III), As(V), and organic arsenic (MMA and DMA) were all 0.3 μg/L and with the linear range from 2.5 to 190 μg/L. Interference from ions common in natural water (Mn, Fe, Cr, Cd, Ca, Zn, Mg, and phosphate) is minimal. The method was validated by analyzing the NIST 1640 natural water standard reference material and by recovery tests on spiked tap water and groundwater. When applied to on-site analysis of sediment pore water and stream water, the CSV results agree well with those obtained by inductively coupled plasma–mass spectrometry (ICP–MS) and graphite furnace atomic absorption spectrometry (GFAAS) methods.     

Methodology to Quantify and Screen the Demineralization of Teeth by Immersing Them in Acidic Drinks (Orange Juice,Coca-Cola™, and Grape Juice): Evaluation by ICP OES

Oral health problems may occur as a result of the ingestion of acid drinks. The objective of this in vitro study was to quantify and screen the concentration of potassium (K), phosphorus (P), calcium (Ca), magnesium (Mg), manganese (Mn), zinc (Zn), iron (Fe), copper (Cu), barium (Ba), lead (Pb), arsenic (As), cadmium (Cd), aluminum (Al), cobalt (Co), chromium (Cr), molybdenum (Mo), sodium (Na), nickel (Ni), selenium (Se), and vanadium (V) released from bovine incisors during an erosive challenge at different times of exposure when immersed in Coca-Cola™, orange juice, and grape juice. A total of 240 samples of bovine incisor teeth were used for the erosive challenge and allocated in groups. Digestion of drinks was performed using microwave-assisted digestion. The content in acidic drinks was monitored before and after the erosive challenge at exposure times of 1, 5, and 60 min using inductively coupled plasma optical emission spectrometry (ICP OES). The drinks’ pH varied slightly during the erosive challenge but remained below the critical value of pH 5 to cause tooth demineralization. The concentrations of elements released from the bovine incisors during the in vitro erosive challenge depend on exposure times when immersed in acidic beverages. For some elements such as Ca, Mn, Zn, Fe, Cu, Ba, Pb, As, and Cd, quantified in acidic drinks, grape juice had greater erosive potential than Coca-Cola™ and orange juice. Quantification and monitoring of chemical elements in bovine teeth can be performed considering a longer erosive time and other types of acidic drinks. Further analysis using human teeth is still not available and must be conducted. The demineralization of teeth not only occurs in acidic beverages; physical and chemical factors play other roles and should be investigated.     

Instrumental Neutron Activation Analysis (INAA) and Inductively Coupled Plasma/Mass Spectrometry (ICP-MS) for Trace Element Biomonitoring using Mosses

Two analytical methods - instrumental neutron activation analysis (INAA) and inductively coupled plasma mass spectrometry (ICP-MS) - were used for the trace element analysis of naturally growing mosses for a heavy metal biomonitoring survey. The techniques were applied to reference mosses to evaluate the feasibility, analytical variability, detection limits and accuracy. These parameters were evaluated using 563 mosses sampled in the 1996 French survey. All the elements of interest in the European program "Atmospheric Heavy Metal Deposition in Europe - estimation based on moss analysis" (As, Cd, Cr, Cu, Fe, Hg, Pb, Ni, V, Zn) were able to be determined by ICP-MS. INAA appeared suitable for the determination of As, Cr, Fe, Hg, V and Zn. The Cd, Cu, Ni and Pb concentrations determined by ICP-MS were preferred to the INAA results, because of increased feasibility or accuracy. The results provided by both methods on the French mosses were statistically compared for 14 elements. Significant linear correlation appeared for: Ba, Ce, Cs, La, Rb, Sm, Th and V. Among these eight elements, Ba, Cs, La and Sm concentrations determined by both methods exhibited a strong statistical similarity. The correlations obtained for As, Eu, Fe and Sb were not as strong and no correlation at all was observed for Co and Cr. These differences were attributed to instrumental factors (e.g. spectral interference occurred for both methods) or due to the sample preparation prior to ICP-MS. The consequences of such results on the regional trend evaluation of atmospheric heavy metal deposition were discussed.     

Speciation of Arsenic in Rice by Ion Chromatography with Online Anion Suppression and Inductively Coupled Plasma Mass Spectrometry

Arsenic speciation in rice has received attention due to its impact on food safety and human health. In this study, a sensitive method was developed for the determination of inorganic arsenic in rice using online anion suppression with ion chromatography and inductively coupled plasma mass spectrometry. HCl of 0.01?mol/L was the optimal extracting agent, and 38?mmol/L sodium carbonate and 15?mmol/L sodium acetate were used as the mobile phase to separate dimethylarsinic acid (DMA), arsenite, monomethylarsonic acid (MMA), and arsenate. The results showed that there were no significant losses or transformations with the anion suppressor and an improvement in sensitivity. The limits of quantification were 0.1?µg/L for DMA, As(III) and MMA, and 0.2?µg/L for As(V). The procedure was used to determine inorganic arsenic in rice; As(III) and DMA were the primary forms present. The reproducibility from seven measurements showed that the relative standard deviation was less than 1.68%. The recoveries were from 99.76 to 110.42%. The present work offers a new approach for the determination of inorganic arsenic in rice.     

Application of fast ultrasound water-bath assisted enzymatic hydrolysis--high performance liquid chromatography-inductively coupled plasma-mass spectrometry procedures for arsenic speciation in seafood materials

Enzymatic hydrolysis of seafood materials for isolating arsenic species (As(III), As(V), DMA and AsB) has been successfully performed by assisting the procedure with ultrasound energy (35 kHz) supplied by an ultrasound water-bath. The use of pepsin, as a proteolytic enzyme, under optimized operating conditions (pH 3.0, temperature 40 °C, enzyme to sample ratio of 0.3) led to an efficient assistance of the enzymatic process in a short period of time (from 4.0 to 30 min). The enzymatic extract was then subjected to a clean-up procedure based on ENVI-Carb™ solid phase extraction (SPE). An optimized anion exchange high performance liquid chromatography (HPLC) coupled to inductively coupled plasma-mass spectrometry (ICP-MS) permitted the fast separation (less than 15 min) of six different arsenic species (arsenite, As(III); arsenate, As(V); dimethylarsinic acid, DMA; and arsenobetaine, AsB; as well as monomethylarsonic acid, MMA; and arsenocholine, AsC) in a single run. Relative standard deviations (n = 11) of the over-all procedure were 7% for AsB and DMA, 11% for As(III) and 9% for MMA. HPLC–ICP-MS determinations were performed using aqueous calibrations covering arsenic concentrations of 0, 5, 10, 25, 100 and 200 μg L⁻¹ (expressed as arsenic) for As(III), As(V), MMA, DMA and AsC; and 0, 125, 250, 500, 750, 1000 and 2000 μg L⁻¹ (expressed as arsenic) for AsB. Germanium (5 μg L⁻¹) was used as an internal standard. Analytical recoveries from the anion exchange column varied from 96 to 105% (enzymatic digests spiked with low target concentrations), from 97 to 104% (enzymatic digests spiked with intermediate target concentrations), and from 98 to 103% (enzymatic digests spiked with high target concentrations). The developed method was successfully applied to two certified reference materials (CRMs), DORM-2 and BCR 627, which offer certified AsB and DMA contents, and also to different seafood samples (mollusks, white fish and cold water fish). Good agreement between certified and found AsB concentrations was achieved when analyzing both CRMs; and also, between certified and found DMA concentrations in BCR 627. In addition, the sum of the different arsenic species concentrations found in most of the analyzed samples was statistically similar to the assessed total arsenic concentrations after a total sample matrix decomposition treatment.     

胃液中微量元素含量测定及临床意义

采用原子吸收法测定了６０例受试者空腹胃液中Ｚｎ，Ｃｕ，Ｆｅ，Ｃａ的含量，以探讨微量元素与胃部疾病的关系，结果显示，Ｚｎ元素在萎缩性胃炎和胃癌组较对照明显升高，而在胃溃疡组则较为对照组明显降低；Ｃｕ元素在萎缩性胃炎和胃癌组较对照组明显升高，Ｆｅ，Ｃａ元素在病例组与对照组间未见差异，Ｚｎ／Ｃｕ比值在胃溃疡和胃癌组较对照组明显降低，本研究为开展微量元素与胃病关系的研究提供了有益资料。     

The extraction and speciation of arsenic in rice flour by HPLC-ICP-MS

Several solvent mixtures and techniques for the extraction of arsenic (As) species from rice flour samples prior to their analysis by HPLC-ICP-MS were investigated. Microwave-assisted extraction using water at 80 °C for 30 min provided the highest extraction efficiency. Total recoveries of extracted As species were in good agreement with the total As concentrations determined by ICP-MS after microwave-assisted acid digestion of the samples. Arsenite [As(III)], arsenate [As(V)] and dimethylarsinic acid (DMAA) were the main species detected in rice flour samples.     

Determination of urinary arsenic species using an on-line nano-TiO2 photooxidation device coupled with microbore LC and hydride generation-ICP-MS system

We have developed an on-line digestion device-based on the nano-TiO₂-catalyzed photooxidation of arsenic species—for coupling between microbore anion-exchange chromatography (μ-LC) and hydride generation (HG)-inductively coupled plasma mass spectrometry (ICP-MS) systems that can be used for the determination of urinary arsenic species. To maximize the signal intensities of the desired arsenic species, we optimized the photocatalytic oxidation efficiency of the analyte species and developed a rapid on-line pre-reduction process for converting the oxidized species into As(III) prior to HG-ICP-MS determination. Under the optimized conditions for the nano-TiO₂-catalyzed photooxidation-i.e., using 1 g of nano-TiO₂ per-liter, at pH 5.2, and illuminating for 3 min- As(III), monomethylarsenoic acid (MMA), and dimethylarseinic acid (DMA) can be converted quantitatively into As(V). To attain maximal hydride generation efficiency, 0.5% Na₂S₂O₄ solution, which can reduce As(V) to As(III) virtually instantaneously upon on-line mixing, was added as a pre-reductant prior to performing the HG step. In light of all the HG efficiency of tested arsenicals were improved and a segmented-flow technique was employed to avoid the loss of peak resolution when using our proposed on-line μ-LC-UV/nano-TiO₂/HG-ICP-MS, the detection limits for As(III), MMA, DMA, and As(V) were all in the range of sub-microgram-per-liter (based on 3 sigma). A series of validation experiments-analysis of neat and spiked urine samples-indicated that our proposed methods can be applied satisfactorily to the determination of As(III), MMA, DMA, and As(V) in urine samples.     

Identification and quantification of major species of arsenic in rice

A study was undertaken to develop a method for the chemical speciation of As in rice on the basis of current knowledge in this field for use in preparing a certified reference material (CRM). Samples of the Arborio rice variety were ground to a fine powder, which was extracted under sonication with a water-methanol mixture (1 + 1, v/v). The resulting solutions were injected into a high-performance liquid chromatograph combined on-line with a quadrupole inductively coupled plasma-mass spectrometer. This hyphenated system allowed for the quantification of As species in one analytical step. Four forms of As were detected: inorganic As (III), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), and inorganic As (V) at concentrations of 88.2 +/- 7.1, 50.8 +/- 5.0, 15.2 +/- 1.7, and 51.2 +/- 3.5 ng/g, respectively. The concentration of total As was 211 +/- 7 ng/g. The limits of detection (3sigma criterion) and the quantitation (10sigma criterion) were, respectively, as follows (in ng/g): As (III), 0.095 and 0.320; As (V), 0.082 and 0.273; MMA, 0.110 and 0.367; and DMA, 0.145 and 0.480. Ten hours were needed for the extraction procedure, 6 h for the evaporation, and 30 min for quantification of the analytes. This investigation was performed in the frame of a European Commission Project on the feasibility of CRMs for As and Se species.     

Stability studies of arsenic, selenium, antimony and tellurium species in water, urine, fish and soil extracts using HPLC/ICP-MS

The stability of arsenic, selenium, antimony and tellurium species in water and urine (NIST SRM 2670n) as well as in extracts of fish and soil certified reference materials (DORM-2 and NIST SRM 2710) has been investigated. Stability studies were carried out with As(III), As(V), arsenobetaine, monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), phenylarsonic acid (PAA), Se(IV), Se(VI), selenomethionine, Sb(III), Sb(V) and Te(VI). Speciation analysis was performed by on-line coupling of anion exchange high-performance liquid chromatography (HPLC) with inductively coupled plasma mass spectrometry (ICP-MS). Best storage of aqueous mixtures of the examined species was achieved at 3 degrees C whereas at -20 degrees C species transformation especially of selenomethionine and Sb(V) took place and a new selenium species appeared within a period of 30 days. Losses and species transformations during extraction processes were investigated. Extraction of the spiked fish material with methanol/water led to partial conversion of Sb(III), Sb(V) and selenomethionine to two new antimony and one new selenium species. The other arsenic, selenium and tellurium species were almost quantitatively extracted. For soil spiked with MMA, PAA, Se(IV) and Sb(III), recoveries after extraction with water and sulfuric acid (0.01 mol/L) were below 20%.     

Determination of arsenite,arsenate, monomethylarsonic acid and dimethylarsinic acid in cereals by hydride generation atomic fluorescence spectrometry

A fast, sensitive and simple non-chromatographic analytical method was developed for the speciation analysis of toxic arsenic species in cereal samples, namely rice and wheat semolina. An ultrasound-assisted extraction of the toxic arsenic species was performed with 1 mol L^− 1 H₃PO₄ and 0.1% (m/v) Triton XT-114. After extraction, As(III), As(V), dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) concentrations were determined by hydride generation atomic fluorescence spectrometry using a series of proportional equations corresponding to four different experimental reduction conditions. The detection limits of the method were 1.3, 0.9, 1.5 and 0.6 ng g^− 1 for As(III), As(V), DMA and MMA, respectively, expressed in terms of sample dry weight. Recoveries were always greater than 90%, and no species interconversion occurred. The speciation analysis of a rice flour reference material certified for total arsenic led to coherent results, which were also in agreement with other speciation studies made on the same certified reference material.     

X-ray fluorescence determination of As, Bi, Co, Cu, Fe, Ni, Pb, Se, V and Zn in natural water and soil extracts after preconcentration of their pyrrolidinedithiocarbamates on cellulose filters

A simple method for the elements preconcentration on thin-layer paraffin-treated cellulose filters was proposed. It was found that pyrrolydinedithiocarbamates of As(III), Bi, Cd, Co, Cu, Fe(III), Ni, Pb, Se(IV), V(V) and Zn obtained after mixing of sample (3-5 ml min⁻¹) and reagent (0.7-1.0 ml min⁻¹) streams were quantitatively recovered from 100 ml sample. The sample acidity was adjusted to pH 4.8-5.2 for preconcentration of Cd, Co, Cu, Fe(III), Ni, Pb, V(V) and Zn, and to 2 M HCl for preconcentration of As, Bi and Se. The optimum reagent concentration was found to be 0.1%. The elements were determined on the filters by X-ray fluorescence spectrometry. The detection limits achieved were 0.1-4.0 μg of element on the filter. Relative standard deviation (R.S.D.) was not higher than 0.08 while determining 5-50 μg of elements on filter. Accuracy and precision of the technique proposed were evaluated by the analysis of spiked natural samples.