Spectrophotometric method for determination of aluminium content in water and beverage samples employing flow-batch sequential injection system

A sensitive, precise and reliable flow-batch method for the determination of aluminium (Al) was developed using a sequential injection-monosegmented flow system incorporating a mixing chamber unit. Eriochrome cyanine R (ECR) was used as a chromogenic reagent in the presence of N,N-dodecyltrimethylammonium bromide (DTAB). The Al-ECR complex at pH 6 gave a maximum absorption at 584 nm. In-line single standard calibration and a standard addition procedure were developed employing the monosegmented flow technique. Under the optimum conditions, a linear calibration graph in the range of 0.0075–0.625 mg L⁻¹ Al was obtained with limits of detection and quantitation of 0.0020 and 0.0070 mg L⁻¹, respectively. Relative standard deviations were 0.8 and 1.3% for 0.010 and 0.025 mg L⁻¹ Al (n = 11), respectively. A sample throughput of 24 h⁻¹ using an in-line standard calibration approach and 6 h⁻¹ using four standard addition levels was achieved. The developed system was successfully applied to water samples and beverage samples. The results agreed well with those obtained from the ICP-AES method. Good recoveries between 85 and 104% were obtained.     

共沉淀分离富集—火焰原子吸收法测定食盐中的微量铅

利用硝酸铋的共沉淀作用分离富集待测元素 ,建立火焰原子吸收法测定食盐中微量铅的方法。该法简便 ,快速 ,相对标准偏差为 1 5 %～ 6 6% ,回收率为 97 3 %～ 10 1 0 %。对样品的测定结果与仲裁法一致。     

Direct atomic absorption spectrometry determination of arsenic,cadmium, copper,manganese, lead and zinc in vegetable oil and fat samples with graphite filter furnace atomizer

The article presents the results of optimization of operation parameters, investigation of analytical characteristics and the abilities of a graphite filter-furnace (FF) atomizer for the direct electrothermal atomic absorption spectroscopy (ET AAS) determination of trace amounts of Mn, As, Pb, Cu, Cd and Zn in some vegetable oils and fats. The effect of pyrolysis and atomization temperatures of the graphite FF atomizer on atomic absorbance values of the listed elements at their evaporation from some organic solutions in the presence of a Pd-Mg chemical modifier (CM) was investigated. For the ET AAS determination of As, Pb, Cd and Zn with Pd-Mg CM, the temperature of the graphite FF atomizer for the pyrolysis step can be raised by 250–350 °C. This mode allows to eliminate the background absorption, to increase the sensitivity of the elements to be analyzed and to enhance the total content of vegetable oils or fats in organic solutions up to 0.5 g mL⁻¹. The obtained limits of quantification for Mn, As, Pb, Cu, Cd and Zn were 0.002, 0.004, 0.004, 0.002, 0.0008, 0.0004 mg kg⁻¹, respectively. The relative standard deviation (RSD) varied between ∼3 and 8% and the time of one element determination did not exceed ∼3–5 min. The reliability of the proposed method was checked using the reference method. A paired Student's t-test showed no significant difference between the results obtained by both methods on a 95% confidence level.     

An automated preconcentration system for the determination of manganese in food samples

In this work, an on-line automated system for the preconcentration and evaluation of manganese in food samples is proposed. The preconcentration of manganese ions is carried out using two mini-columns packed with 4-(5′-bromo-2′-thiazolylazo)orcinol (Br-TAO) loaded polyurethane foam. After a preconcentration step, a stream of hydrochloric acid is passed through the mini-column in order to transport the manganese directly to the flame atomic absorption spectrometer. The sample frequency was 60 h⁻¹ for a 60 s preconcentration time. The limit of detection and enrichment factor were 0.70 μg L⁻¹ and 17, respectively. The accuracy of the procedure was evaluated by analysis of biological reference materials (spinach leaves, tomato leaves and pine needles). The procedure was successfully applied for the evaluation of manganese in several food samples, such as corn, rice and cassava flour.     

Heat-assisted slurry sampling GFAAS method for determination of lead in food standard reference materials

A valid method based on heat-assisted slurry sampling graphic furnace atomic absorption spectrometry (HASS-GFAAS) was developed for the accurate determination of trace Pb in food standard reference materials (SRMs). The HASS technique significantly improved Pb recovery and precision compared to conventional slurry sampling techniques. The optimized HASS procedure was performed as follows: first, the sample (particle size ≤ 150 μm) was diluted with 0.05% (v/v) Triton X-100 containing 2% HNO₃ and 1% H₂O₂ followed by heating for 20 min at 120 °C on a heating block. Next, the obtained slurry was sonicated in an autosampler cup, and finally, the slurry was introduced into a graphite tube and analyzed by the GFAAS with a Pb electrodeless discharge lamp (EDL). Calibration with aqueous standard solutions was used for Pb determination in food samples. The characteristic mass and limit of detection for Pb based on the integrated absorbance for a 2% (m/v) sample were 12 ± 0.6 pg and 0.003 mg kg⁻¹, respectively. The accuracy (95.1–102% recovery) and good precision (0.1–3.6%) of this procedure are illustrated by the results obtained for the 12 food reference materials. The proposed method is suitable for determination of trace Pb in solid food samples.     

Development of a new method for determination of aluminum (Al) in Jordanian foods and drinks: Solid phase extraction and adsorption of Al3+-d-mannitol on carbon nanotubes

In this work, a new method was developed for determination of aluminum (Al) in traditional Jordanian foods (Mansaf, Kofta, Tabboola, Hummous, bread), tea, Arabian coffee and water samples. The method involved solid phase extraction (SPE) of Al³⁺ from the digested samples after complexation with d-mannitol using carbon nanotubes (CNT) as the extractive sorbent. Formation of the Al³⁺-d-mannitol complex was confirmed by infrared spectroscopy. Optimization of the SPE method involved sample pH, d-mannitol-to-Al mole ratio, sample loading and elution flow rates, adsorbent mass, eluent concentration and volume. Based on spiked water samples, the characteristics of the method were as follows: the limit of quantification: 23 μg l⁻¹; sensitivity: 0.0036 (mg l⁻¹)⁻¹; %RSD range: 0.4–1.9%; recovery range: 76.0–93.0%. The equilibrium, thermodynamic and kinetic adsorption studies of Al³⁺-d-mannitol on CNT revealed that adsorption was spontaneous, exothermic, preferred, of physical nature; followed second-order rate kinetics; pore diffusion was not the only rate-controlling step; both Langmuir and Freundlich isotherms represented the data satisfactorily.     

Assessment of trace metals in foodstuffs grown around the vicinity of industries in Bangladesh

In the present study, we investigated the levels of chromium (Cr), nickel (Ni), copper (Cu), arsenic (As), cadmium (Cd) and lead (Pb) in eight groups of foods, namely, cereals, pulses, vegetables, fruit, fish, meat, eggs and milk. The range of Cr, Ni, Cu, As, Cd and Pb in the foodstuffs was 0.18–4.8, 0.008–10, 0.47–22, 0.003–0.98, 0.0003–0.85 and 0.005–3.7 mg/kg fw, respectively. The daily intakes (EDIs) of Cr, Ni, As, Cd and Pb were higher than the maximum tolerable daily intake (MTDI), indicating their potential sources from dietary intake. The combined metal hazard quotients (∑HQs) from rice, fruit, vegetables and fish were higher than 1, meaning that metals may pose a considerable risk to local inhabitants due to consumption of these four food items. From the human health point of view, this study showed that the studied foods were not safe for the local inhabitants, and potential risk cannot be neglected for regular or excessive consumers.     

The content of selected minerals and vitamin C for potatoes (Solanum tuberosum L.) from the high Tiber Valley area,southeast Tuscany

Potatoes (Solanum tuberosum L.) from the high Tiber valley area (TVA; Tuscany, Italy), have been sampled and analyzed for selected mineral content (Na, Mg, K, Ca, and Mn, Fe, Cu and Zn) and vitamin C, the year 2012; some samples from 2011 and 2013 crops were also collected and analyzed. The varieties were Daytona (DAY), Kennebec (KEN), Sifra (SIF) and Volare (VOL). Control samples consisted of mixed commercial varieties from the local market, namely C1, C2 and C3. The low content of sodium, especially for KEN (46 ± 3 mg/kg FD (freeze dry), year 2012) and SIF (47 ± 3) (VOL (55 ± 3) and DAY (61 ± 3) have a little higher values) is worth of note and in agreement with the scarce concentration of Na in the soil (291 ± 12 mg/kg DM). Magnesium was abundant in KEN (1434 ± 75 mg/kg FD, year 2012) and VOL (1334 ± 70). The content of K for DAY and KEN (13,147 ± 900 and 13,185 ± 900 mg/kg FD) was higher than for VOL and SIF; whereas Ca was in the range 340 ± 16–490 ± 28 mg/kg FD. The contents of Cu and Zn were higher in KEN (8.1 ± 0.3 and 25 ± 1 mg/kg FD) when compared to the other varieties and controls. The content of vitamin C is high for KEN and SIF and decreased significantly upon cooking (50% for KEN).     

Zirconium nanoparticles based ligandless dispersive solid phase extraction for the determination of antimony in bergamot and mint tea samples by slotted quartz tube-flame atomic absorption spectrophotometry

A sensitive and effective analytical method was developed to preconcentrate antimony from the bergamot and mint tea samples for its determination at trace levels by slotted quartz tube-flame atomic absorption spectrophotometry (SQT-FAAS) system. The developed method was based on vortex assisted ligandless dispersive solid phase extraction (VA-LDSPE) using zirconium nanoparticles (Zr-NPs) as sorbent material for the adsorption of the target analyte. All variables involved in the DSPE method (pH value, nanoparticle amount, mixing and eluent type/volume) were optimized to boost the absorbance signal of antimony. Using the optimal parameters, the method provided satisfactory detection and quantification limits of 8.0 and 26.8 μg L⁻¹, respectively. A 180 folds enrichment factor was achieved by the developed method when compared with the detection power of the FAAS. Linear range of the proposed method was found to be 30–250 μg L⁻¹, with a coefficient of determination value of 0.9992. The established Zr-NPs-VA-LDSPE-SQT-FAAS method was successfully implemented to bergamot tea samples in order to check accuracy and applicability. The obtained recovery values ranged between 93–102%, and this demonstrated that the complex matrices tested did not affect the accuracy of quantifying antimony.     

Two-phase hollow fiber liquid phase microextraction for preconcentration of pyrethroid pesticides residues in some fruits and vegetable juices prior to gas chromatography/mass spectrometry

A sensitive and reliable extraction method based on two-phase hollow fiber liquid phase microextraction followed by gas chromatography–mass spectrometry has been developed for determination of three pyrethroid pesticides. The various parameters affecting the extraction efficiency were studied via rotatable-centered cube central composite design (CCD). The optimization results showed that speed of agitation, extraction time and ionic strength were significantly important in the extraction process. A response surface equation was derived, and the statistical parameters of the derived model were obtained as R² = 0.9862 and F = 142.46. The response surface plots revealed a separation optimum with 480 rpm speed agitation, extraction time of 41 min and NaCl concentration of 3% (w/v). Method detection limits were obtained in the range of 0.02–0.07 ng/mL, and limits of quantitation were between 0.08 and 0.10 ng/mL. The proposed method was successfully applied for the determination of pyrethroid pesticides in some fruits and vegetable juice samples and satisfactory results were obtained.