Slotted Tube Atom Trap Research Articles

A sensitive and accurate analytical method for the determination of cadmium in food samples: Molybdenum coated T-shape slotted quartz tube flame atomic absorption spectrophotometry

In this study, a molybdenum coated T-shaped slotted quartz tube atom trap flame atomic absorption spectrophotometry method (Mo coated-T-SQT-AT-FAAS) was developed for the determination of cadmium with on-line preconcentration. Inner surface of T-SQT was coated with molybdenum to enhance the trapping efficiency. Hydrogen gas was used instead of organic solvents to release trapped atoms. Limit of detection and quantification were found to be 0.057 and 0.082 µg/L, respectively. The developed method has a linear working range between 0.10 and 1.0 µg/L with a low %RSD value (<3.7). About 1202 times enhancement in detection power was recorded over the conventional FAAS system. Recovery experiments were used to determine the applicability of the method developed to real samples (linden, milk powder and mint) and significant results (94.4–100.7%) were obtained for the samples spiked at 0.30, 0.50 and 1.0 µg/L. The method was also applied to Tomato Leaves 1573a SRM to check the accuracy.

Lead determination at ng/mL level by flame atomic absorption spectrometry using a tantalum coated slotted quartz tube atom trap

Flame atomic absorption spectrometry (FAAS) still keeps its importance despite the relatively low sensitivity; because it is a simple and economical technique for determination of metals. In recent years, atom traps have been developed to increase the sensitivity of FAAS. Although the detection limit of FAAS is only at the level of µg/mL, with the use of atom traps it can reach to ng/mL. Slotted quartz tube (SQT) is one of the atom traps used to improve sensitivity. In atom trapping mode of SQT, analyte is trapped on-line in SQT for few minutes using ordinary sample aspiration, followed by the introduction of a small volume of organic solvent to effect the revolatilization and atomization of analyte species resulting in a transient signal. This system is economical, commercially available and easy to use. In this study, a sensitive analytical method was developed for the determination of lead with the help of SQT atom trapping flame atomization (SQT-AT-FAAS). 574 Fold sensitivity enhancement was obtained at a sample suction rate of 3.9mL/min for 5.0min trapping period with respect to FAAS. Organic solvent was selected as 40µL of methyl isobutyl ketone (MIBK). To obtain a further sensitivity enhancement inner surface of SQT was coated with several transition metals. The best sensitivity enhancement, 1650 fold enhancement, was obtained by the Ta-coated SQT-AT-FAAS. In addition, chemical nature of Pb species trapped on quartz and Ta surface, and the chemical nature of Ta on quartz surface were investigated by X-ray photoelectron spectroscopy (XPS) and Raman Spectroscopy. Raman spectrometric results indicate that tantalum is coated on SQT surface in the form of Ta2O5. XPS studies revealed that the oxidation state of Pb in species trapped on both bare and Ta coated SQT surfaces is +2. For the accuracy check, the analyses of standard reference material were performed by use of SCP SCIENCE EnviroMAT Low (EU-L-2) and results for Pb were to be in good agreement with the certified value using SQT-AT-FAAS and Ta coated-SQT.

Sensitive determination of lead, cadmium and nickel in soil, water, vegetable and fruit samples using STAT-FAAS after preconcentration with activated carbon

In this study, lead (Pb), cadmium (Cd) and nickel (Ni) were determined in soil, water, vegetable and fruit samples taken from around oil refinery region in Batman, Turkey. Digestion procedures for samples were optimized and all optimum parameters were used both in digestion and in determination steps. In order to determine Pb and Cd, slotted tube atom trap (STAT) was used to increase the sensitivity in atomic absorption spectrophotometry. Preconcentration procedure under the optimum conditions was applied to water, vegetable and fruit samples to determine Pb, Cd and Ni in trace levels. In soil samples, concentrations of analytes were found in the range of 4.0 ± 0.2-12,000 ± 60 mg/kg for Pb, 0.15 ± 0.01-3.0 ± 0.1 mg/kg for Cd and 21 ± 1-65 ± 3.4 mg/kg for Ni. In all water samples, concentration of Ni was expressed as nanogram per milliliter (ng/mL) and found to be higher than Pb and Cd levels. It was observed that Pb, Cd and Ni concentrations varied from both plant to plant and in same plants at different experimental sites. Pb concentrations in vegetable and fruit samples interested varied between 20 ± 2 and 160 ± 12 ng/g, and the highest level of Pb was found to be in green pepper taken from 1000 m away from refinery.

Development of a sensitive method for lead determination by flame atomic absorption spectrometry using slotted quartz tube in-situ atom trapping and metal coatings

Flame atomic absorption spectrometry (FAAS) still keeps its importance despite the relatively low sensitivity, because it is a simple and economical technique for determination of metals. In recent years, atom traps have been developed to increase the sensitivity of FAAS. Although the detection limit of FAAS is only at the level of mgL−1, with the use of atom traps it can reach to the level of ngmL−1. Slotted quartz tube (SQT) is one of these atom traps; it is applied for determination of volatile elements. It is economical, commercially available and easy to use. In this study, a sensitive analytical method has been developed for the determination of lead with the help of SQT. 1472 fold sensitivity enhancement was obtained using the uncoated slotted quartz tube atom trap flame atomic absorption spectrometry (SQT-AT-FAAS) method at a sample suction rate of 7.4mLmin−1 for 4.0min collection with respect to FAAS. To obtain a further sensitivity enhancement, the inner surface of SQT was coated with several kinds of transition metals. The best sensitivity enhancement, 4600 fold, was obtained by the Ta-coated-SQT-AT-FAAS. In addition, the chemical nature of Pb trapped on quartz and Ta surface, and the chemical nature of Ta on quartz surface were investigated by X-ray photoelectron spectroscopy (XPS).

Indium determination using slotted quartz tube-atom trap-flame atomic absorption spectrometry and interference studies

Sensitivity enhancement of indium determination by flame atomic absorption spectrometry (FAAS) was achieved; using a slotted quartz tube (SQT-FAAS) and slotted quartz tube atom trap (SQT-AT-FAAS). SQT was used as an atom trap (AT) where the analyte is accumulated in its inner wall prior to re-atomization. The signal is formed after re-atomization of analyte on the trap surface by introduction of 10μL of isobutyl methyl ketone (IBMK). Sensitivity was improved 400 times using SQT-AT-FAAS system with respect to conventional FAAS and 279 times with respect to SQT-FAAS without any collection. Characteristic concentration (C0) and limit of detection values were found to be 3.63ngmL−1 and 2.60ngmL−1, respectively, using a sample flow rate of 7.0mLmin−1 and a collection period of 5.0min. In addition, interference effects of some elements on indium signal were studied. In order to characterize indium species trapped, X-ray Photoelectron Spectrometry (XPS) was utilized and it was found that indium was collected on the inner surface of SQT as In2O3. The accuracy of the procedure was checked to determine indium in the standard reference material (Montana Soil, SRM 2710).

Determination of Lead and Manganese in Biological Samples and Sediment Using Slurry Sampling and Flame Atomic Absorption Spectrometry

A procedure was developed for the determination of lead (Pb) and manganese (Mn) using slurry sampling. The two elements were detected using flame atomic absorption spectrometry with a slotted tube atom trap. Slurries were prepared by adding nitric acid solution (0.30%, w/v) to a powdered sample (0.10 g). After homogenization by ultrasonic bath for 15 min, the slurries were introduced directly into the detection equipment. Some conditions of the procedure were evaluated, such as acid concentration, presence of surfactants, and sonication time. Under optimized conditions, the LODs and LOQs achieved were 0.8 and 2.6 microg/g for Pb and 0.5 and 1.6 microg/g for Mn, respectively. The precision obtained varied between 3.1 and 5.8% (Mn), and 2.6 and 5.4% (Pb) for slurries of shrimp and sediment. The analytical curves were established using aqueous standards in nitric acid solutions. The accuracy of the method was assessed through the determination of Pb and Mn in the following certified reference materials: ERM-CE 278 (mussel tissue), CRM 397 (human hair), and SRM 1646a (estuarine sediment). The proposed procedure was successfully applied to the determination of Pb and Mn in six samples of shrimp powder, seasoning, and river sediment. The levels of Mn detected varied from 2.2 to 71.3 microg/g; Pb was detected in only one sediment sample (4.3 microg/g).

Determination of Zinc, Copper, Iron, and Manganese in Different Regions of Lamb Brain

The levels of zinc, copper, iron, and manganese were measured in the hippocampus, thalamus, gyrus cinguli, hypothalamus, and in the prefrontal, parietal, temporal, and occipital cortexes of lamb brain by flame atomic absorption spectrometry. Standard addition method was also applied to samples and it was observed that there was no matrix interference affecting the determination of elements interested. In the determination of Cu, a slotted tube atom trap was used to improve sensitivity. One-way analysis of variance was used for the statistical evaluation of the results for each element. Limit of detection results for Zn, Cu, Fe, and Mn were found to be 24, 4.5, 60, and 25ng/mL, respectively. Region-specific differences were found for all elements interested. Mn concentration ranging from 0.29 ± 0.04 to 0.61 ± 0.04mg/kg was found to be the lowest in all brain regions among the all elements interested.

Online preconcentration for the determination of lead, cadmium and copper by slotted tube atom trap (STAT)-flame atomic absorption spectrometry

An online sensitivity enhancement by using atom trapping in flame atomic absorption spectrophotometry was examined for increasing the residence time of the analyte atoms in the light path. For this purpose, various parameters of quartz tubes of the slotted tube atom trap were tested. The studied parameters include the internal diameter, the length of the upper slot and the wall thickness of quartz tube. The best sensitivities as high as 7-fold, 13-fold and 3-fold enhancement were achieved by the tubes having an internal diameter of 6 mm, an upper slot length of 1.0 cm and the wall thickness of 1.5 mm for lead, cadmium and copper, respectively. The limits of quantitation were found to be 30 ng mL −1 for Pb and 3 ng mL −1 for Cd and 30 ng mL −1 for Cu by the optimized method. The achieved technique was applied to determine the concentrations of Pb, Cd and Cu in different plant leaves taken around cement and textile industries.

Determination of lead, cadmium and copper in roadside soil and plants in Elazig, Turkey

The concentrations of lead, cadmium and copper in roadside soil and plants in Elazig, Turkey were investigated. Soil samples were collected at distances of 0, 25 and 50 m from the roadside. The concentrations of lead, cadmium and copper were measured by Flame Atomic Absorption Spectrophotometry (FAAS). A slotted tube atom trap (STAT) was used to increase the sensitivity of lead and cadmium in FAAS. Lead concentrations in soil samples varied from 1.3 to 45 mg kg(-1) while mean lead levels in plants ranged from120 ng g(-1) for grape in point-4 to 866 ng g(-1) for apple leaves in point-2. Lead analyses showed that there was a considerable contamination in both soil and plants affected from traffic intensity. Overall level of Cd in soil samples lies between 78 and 527 ng/g while cadmium concentration in different vegetations varied in the range of 0.8-98.0 ng g(-1). Concentrations of copper in soil and plant samples were found in the range of 11.1-27.9 mg kg(-1) for soil and 0.8-5.6 mg kg(-1) for plants. Standard reference material (SRM) was used to find the accuracy of the results of soil analyses.

Comparison of trace element concentrations in cancerous and noncancerous human endometrial and ovary tissues

Question of whether trace metal concentrations in tissues are increased or decreased in cancerous patients in comparison with noncancerous patients has not been answered yet, due to the fact that the data known in this field are rare and have contradictory results. Although Zn and Cu concentrations in serum and tissues of cancerous patients have extensively been studied, the precise role of these metals in carcinogenesis is not clearly understood. There are few studies on the concentrations of essential and toxic trace/minor metals in human tissue samples in comparison with serum and plasma samples. Trace metal concentrations including Cd, Cu, Zn, Fe, Mg, Ca, and Ni in both cancerous and noncancerous endometrial, ovary, and cervix uteri tissues were determined by atomic absorption spectrometry. The tissue samples were digested by using microwave energy. Slotted tube atom trap was used to improve the sensitivity of copper and cadmium in flame atomic absorption spectrometry determination. The concentrations of iron in cancerous endometrial tissues were found to be significantly higher than those in noncancerous samples (P < 0.01). On the contrary Fe, Zn concentration in cancerous endometrial tissue was found to be lower significantly than those in noncancerous samples (P= 0.005), whereas the other studied metals were not observed different. Furthermore, Cu and Ca concentrations in cancerous ovary samples were observed to be higher than those in noncancerous ovary tissues (P < 0.01 for Cu and P= 0.1 for Ca), whereas Mg, Fe, and Zn levels in cancerous ovary samples were not found to be different than those in noncancerous tissues.

Distribution of trace metal concentrations in paired cancerous and non-cancerous human stomach tissues.

To assess whether trace metal concentrations (which influence metabolism as both essential and non-essential elements) are increased or decreased in cancerous tissues and to understand the precise role of these metals in carcinogenesis. Concentrations of trace metals including Cd, Ni, Cu, Zn, Fe, Mg and Ca in both cancerous and non-cancerous stomach tissue samples were determined by atomic absorption spectrometry (AAS). Tissue samples were digested using microwave energy. Slotted tube atom trap was used to improve the sensitivity of copper and cadmium in flame AAS determinations. From the obtained data in this study, the concentrations of nickel, copper and iron in the cancerous human stomach were found to be significantly higher than those in the non-cancerous tissues, by using t-test for the paired samples. Furthermore, the average calcium concentrations in the cancerous stomach tissue samples were found to be significantly lower than those in the non-cancerous stomach tissue samples by using t-test. Exceedingly high Zn concentrations (207-826 mg/kg) were found in two paired stomach tissue samples from both cancerous and non-cancerous parts. In contrast to the literature data for Cu and Fe, the concentrations of copper, iron and nickel in cancerous tissue samples are higher than those in the non-cancerous samples. Furthermore, the Ca levels are lower in cancerous tissue samples than in non-cancerous tissue samples.

The synthesis of new polymeric sorbent and its application in preconcentration of cadmium and lead in water samples

Metal determinations at low concentration levels (≤ng mL −1) comprise one of most important targets in analytical chemistry. This interest also increases in different areas such as biology, medicine, environment and food samples. In spite of inherent high sensitivities obtained for electrothermal atomic absorption spectrometry (ETAAS) and inductively coupled plasma–mass spectrometry (ICP–MS), these techniques have some limitations depending on the concomitants. As a result, interest in preconcentration techniques still continues increasingly for trace metal determinations by flame atomic absorption spectrometry (FAAS) due to the high accuracy of this method. In this work, thioureasulfonamide resin was synthesized, characterized and applied as a new sorption material for determinations of cadmium and lead in water samples. The method is based on the sorption of Cd and Pb ions on the synthesized resin without using any complexing reagent. The optimization of experimental conditions was performed using factorial design including pH, amount of resin, contact time, first sample volume and final eluent volume. Using the experimental conditions defined in the optimization, the method was applied to the determination and preconcentration of Cd and Pb at ng mL −1 level in natural water. Flame AAS was used for trace metal determinations. This method exhibits the superiority in compared to the other adsorption reagents because of the fact that there is no necessity of any complexing reagent and optimum pH of solution presents in acidic media. Consequently, 600- and 360-fold improvements in the sensitivity of FAAS were achieved by combining the slotted tube atom trap–atomic absorption spectrometry (STAT–FAAS) and the purposed enrichment method for Cd and Pb, respectively.

The improvement of sensitivity in lead and cadmium determinations using flame atomic absorption spectrometry

Various designs of quartz tubes of the slotted tube atom trap were examined to improve the sensitivity of flame atomic absorption spectrophotometry. The studied designs include the diameter length and the length of the upper slot of quartz tubes. Tubes having a diameter of 5 and 6 mm and an upper slot length of 2.3 cm produce the best sensitivity—as high as 6- and 10-fold enhancement for lead (Pb) and cadmium (Cd), respectively. The limits of quantitation were found to be 35 and 4 ng ml −1 for Pb and Cd, respectively, by the optimized method. The achieved technique was applied to determine the concentrations of Pb and Cd in cancerous (malign) and noncancerous (adenoma) human thyroid tissues.

Sensitivity enhancement in flame atomic absorption spectrometry for determination of copper in human thyroid tissues.

Various designs of quartz tube in a slotted tube atom trap were examined for improving the sensitivity of flame AAS. A 3.5-fold enhancement in the sensitivity was obtained by using the optimized method. The method was applied to the determination of Cu in cancerous and non-cancerous human thyroid tissues. The Cu concentrations of the cancerous samples tended to increase compared with the non-cancerous samples. Zn concentrations of the same tissues were also determined.

Identification of Chemical Forms of Lead, Cadmium and Nickel in Sewage Sludge of Waste Water Treatment Facilities

Lead, cadmium and nickel levels in sewage sludge of a waste water treatment facility were determined by slotted tube atom trap (STAT)-flame atomic absorption spectrometry after using different extraction reagents. In addition, a sequential extraction procedure was applied to the same samples and the results were compared. It was found that Pb and Cd were relatively mobile as organically bound, carbonate or adsorbed on the Fe–Mn oxides and the concentrations in the extracts were higher than 50%. However, the percentage of Ni bound to these phases was found to be very low.

SIMULTANEOUS ENRICHMENT OF Cd, Pb, Ni, AND Al AND THEIR DETERMINATION IN WATER BY STAT-FAAS

Toxic metals such as Cd, Pb, Ni and Al were determined in drinking, dam lake, stream and lake water by using flame atomic absorption spectrometry (FAAS) after enrichment. In the enrichment procedure, their chelates with cupferron were preconcentrated on activated carbon. For increasing the sensitivity of cadmium and lead, slotted tube atom trap (STAT) was used as accessory in the FAAS. 150 fold preconcentration was achieved.

Speciation of lead in soils and relation with its concentration in fruits

The lead concentrations of the fruit samples were determined by using slotted tube atom trap (STAT)-enrichment-flame and graphite furnace atomic absorption spectrometry (FAAS and GF-AAS). The soil samples related to these fruits were also analysed for Pb after extraction with various chemical reagents. The relation between the fruit-lead and soil-extractable lead concentrations was examined in order to explain the bioavailability of lead. A linear relation was observed between the hot Na2EDTA extraction-soluble Pb contents in the soil and the Pb concentrations in the mulberry (R2=0.95), strawberry and apple grown on these soils. Probable chemical forms of lead in soil were evaluated. Acceptable agreement (at least 91%) was achieved between the results of STAT-enrichment-FAAS and GF-AAS.

Determination of cadmium and lead in human urine by STAT-FAAS after enrichment on activated carbon

M. Yaman, J. Anal. At. Spectrom., 1999, 14, 275 DOI: 10.1039/A807432A

Speciation of four selenium compounds using high performance liquid chromatography with on-line detection by inductively coupled plasma mass spectrometry or flame atomic absorption spectrometry

An analytical method for the speciation of selenomethionine, selenocystine, selenite and selenate by high performance liquid chromatography (HPLC) with atomic spectrometric detection is presented. An organic polymeric strong anion exchange column was used as the stationary phase in combination with an aqueous solution of 6 mmol L–1 of salicylate ion at pH 8.5 as the mobile phase which allowed the isocratic separation of the four selenium analytes within 8 minutes. The separated selenium species were detected on-line by flame atomic absorption spectrometry (FAAS) or inductively coupled plasma mass spectrometry (ICP-MS). The signal-to-noise ratio of the FAAS detector was optimized using a hydrogen-argon entrained-air flame and a slotted-tube atom trap (STAT) in the flame. The limit of detection (3 σ) achieved by the HPLC-FAAS system was 1 mg L–1 of selenium (100 μL injections) for each of the four selenium species. More powerful selenium detection was achieved using an ELAN 5000 ICP-MS instrument. Selenium was measured at m/z = 82. The ICP-MS signal intensity was enhanced by a factor of 3–4 after addition of 3% methanol to the chromatographic mobile phase and by using an increased plasma power input of 1300 W. The limit of detection achieved under these conditions was 1 μg L–1 (100 μL injections). The HPLC-ICP-MS system was used for selenium speciation of selenite and selenate in aqueous solutions during a BCR certification exercise and for selenium speciation in the certified reference material, BCR No. 402 White Clover. Extraction experiments revealed that the selenium species in the biological material were extractable only in the presence of water in the extraction medium. The results indicated that selenate and a compound of unknown identity U were present in the plant sample.

Metal determinations with a novel slotted-tube water-cooled atom trap

Data is presented for lead and cadmium using a novel collecting device, which consists of a commercially available slotted-tube atom trap (STAT) and a single silica tube water-cooled atom trap (WCAT), fabricated in house. A diagram is given which shows this device (slotted-tube water-cooled atom trap or STWCAT) mounted on a new holder, showing its physical orientation over the slot of the burner. Data is also given showing the improvement in sensitivity and precision over other forms of atom trapping with characteristic concentrations of 0.112 and 1.042 ng ml–1 for cadmium and lead, respectively. A series of samples was collected, ranging from local river water to sewage effluent, and determined using three different atom trapping techniques, such as the single-tube WCAT, the dual “bent” WCAT and the STWCAT. It was found that the new STWCAT performed very well in comparison with the other two tubes, showing very high sensitivity with excellent precision.