Ml Of Nitric Acid Research Articles

Micro-Milli Scale for the Removal of Iron and Copper by a Positively Charged Foam before Nickel Colorimetric Detection using Handy Spectrometer

Introduction: Simple alternative detection of nickel with iron and copper as interferences was proposed. The procedure was based on sampling a milligram sample and a micro-milliliter operation. Methods: The method has been applied to jewelry items. A 50 mg sample was digested by 5 mL of nitric acid with heating. The obtained solution was added with KSCN before passing through polyurethane foam (PUF) (1 cm i.d. × 8 cm length). Some metal ions-SCN complexed (e.g., Fe(III) and Cu(II)) were retained in the column while Ni(II) ions were in the eluate. A 200-500 µL aliquot was added with 4-(2-pyridylazo)-resorcinol (PAR) as the color reagent. At least 30 µL of a portion was measured for the absorbance of the color product using a handy spectrometer. Results: The positively charged foam could remove iron and copper altogether before determining nickel. A standard calibration was a plot of absorbance versus Ni(II) concentration for 1-30 mg/L: absorbance = 0.0123[Ni(II), mg/L] + 0.0435 (R2=0.9945) with a limit of detection (LOD) and limit of quantitation (LOQ) of 0.24 mg/L and 0.81 mg/L, respectively. Two bracelet samples showed the presence of nickel at 0.97 ± 0.25 and 0.27 ± 0.04 mg/g, respectively, and agreed with the reference FlameAAS method. Conclusion: The proposed method could be used to assay nickel in samples containing high levels of iron and copper, such as jewelry. This will benefit general wearers with health concerns associated with nickel, particularly in case of inexpensive accessories. The handy spectrometer used in the study might make be helpful to carry out these studies with a limited tight budget.

Determination of Levels of Selected Essential and Non Essential Metals in Mango (Mangifera indica L.) Cultivated in Wolaita Zone, Southern Ethiopia

Background: Mango (Mangifera indica L.) is one of the most important tropical fruits commercialized and consumed worldwide fresh or processed, having an attractive color and distinct taste and aroma. The main objective of this study is to determine the level of selected essential and non-essential metals in Mango. Methods: The levels of essential and non-essential metals were determined in mango (Mangifera indica L.) samples collected from four different sites (Boloso Bombe, Boloso Sore, Damot woyde and Humbo) in Wolaita Zone, Southern Ethiopia by flame atomic absorption spectrometry. A 0.5 g dried powdered mango sample was digested with 1 mL of nitric acid (HNO3), 3 mL of perchloric acid (HClO4) and 1 mL of hydrogen peroxide (H2O2) at 180°C for 2:00 hours. The study focused on two mango varieties, the Apple mango and the Keitt mango. Result: The metal contents in the apple mango in mg/kg were found in the following order: Mg (20.04-0.34) greater than Ca (1.49-6.78) greater than Zn (2.32-4.23) greater than Fe (2.77-2.85) greater than K (2.03-2.41) greater than Na (1.72-1.97) greater than Mn (0.47-1.36) mg/kg; and that of the Keitt mango samples in mg/kg were in the order of: Mg (2o.08_20.34) greater than Ca (0.95_5.84) greater than Zn (2.69_3.66) greater than Fe (2.69_2.90) greater than K (1.91_2.77) greater than Na (1.79_1.93) greater than Mn (0.38_0.72) mg/kg, respectively. The levels of Cd and Pb were below method detection limit. Analysis of variance (ANOVA) at 95% confidence level indicated that there is significant difference in the mean concentration of all metals between the four sample sites. There was good correlation between the levels of some metals (Mg, Ca, Zn, Fe K, Na and Mn) in both varieties of mango samples. From the results of this study it can be concluded that the studied mango varieties grown in the study area are good source of essential metals and free from the toxic metals: Cd and Pb.

HEAVY METALS QUANTIFICATION AND CORRELATIVE CARCINOGENIC-RISKS EVALUATION IN SELECTED ENERGY DRINKS SOLD IN BAYELSA STATE USING ATOMIC ABSORPTION SPECTROSCOPIC TECHNIQUE

Objective: The study aimed to quantify the concentrations and carcinogenic-related health risks assessment of some heavy metals in selected energy drinks frequently utilized in Bayelsa State, Nigeria. Methods: Eleven energy drinks samples were purchased from the general markets in Amassoma and Yenagoa, Bayelsa State, Nigeria, and were labeled D1–D11. The samples were digested using 10 ml of nitric acid at 120-150 ℃, and 2 ml of Perchloric acid was added after attaining room temperature, it was digested further until a clear solution was obtained, then made up to 25 ml with distilled water. The concentration of lead, cadmium, iron, and zinc were determined and quantified using Atomic Absorption Spectrophotometry (AAS), and the health-associated risks of these metals were evaluated using the standard Target Health Quotient (THQ). Results: The EDI (Estimated Daily Intake) of lead (Pd), Cadmium (Cd), iron (Fe), and zinc (Zn) was 0.130, 0.001, 0.726, and 0.193 mg/l, respectively, all were within the World Health Organization (WHO)-acceptable range. The Chronic Daily Intake (CDI) of Pd, Cd, Fe, and Zn was obtained as 0.001 to 0.010, 5.7 x 10-5, 0.001 to 0.050, and 0.0001 to 0.010 mg/l respectively. Conclusion: THQ for all metals analyzed was<1, the WHO acceptable limit. All the heavy metals were within acceptable THQ limits, thus posing no carcinogenic health potential risks on long-term consumption.

Bio-Accumulation of Heavy Metals in Aquatic Organism in Otamiri River in Owerri, Imo State, Nigeria

Depending on a number of variables, heavy metals from both natural and anthropogenic sources may accumulate in fish bodies and heads in aquatic environments. This study intends to evaluate the degree of heavy metal bioaccumulation in Tilipia fish from the Otamiri river. A sample of dry tissue weighing around one gram was weighed, placed into polyethylene tubes, and treated with 8 ML of nitric acid and 4 ML of perchloric acid. An atomic absorption spectrophotometer was used to determine the presence of heavy metals in the fish tissues. The amount of heavy metals present in fish sections was listed as follows: Lead varies from 32.00-7.23mg/kg, and the greatest value was found in the fish head that was caught in the Otammiri River. Zinc ranges from 16.75 mg/kg to 17.13 mg/kg, with the highest value recorded in the fish head. Copper concentrations range from 1.50 to 5.43 mg/kg, and iron concentrations range from 67.25 to 90.58 mg/kg, with the greatest value found in fish heads. Nickel ranges from 5.78 to 13.90mg/kg and cadmium ranges from 1.38 to 3.68mg/kg; the fish head has the highest concentration of these elements. The region of the fish's head was discovered to have the highest concentration of all the heavy metals. This is due to the fact that the fish's gills are the first organs to be exposed to heavy metal exposure and are a significant site for heavy metal intake. However, when the levels of heavy metals in the fish from this Rivers was compared to the WHO's tolerable standard, the concentrations were significantly higher, raising serious concerns because, by all accounts, the Otammiri River is highly contaminated and these fish could have a negative impact on human health if consumed. Therefore, steps should be done to prevent additional River contamination.

Investigation of the changes in some elements that play an active role in MS disease

Objective: In this study, we examined the role of several metals which extracted from the hair of patients who affected by multiple sclerosis (MS). The ICP-MS measurements were performed using an Agilent 7500 series. With this procedure, all elements can be simultaneously quantified. Material and Methods: All studies were carried out at Kayseri City Hospital between August 9, 2021, and October 11, 2021. We measured five elements from hair in association with the clinical course in 40 male and female MS subjects, as well as 40 healthy volunteers, using 1 cm hair sections. Using a novel microwave digestion method coupled with ICP-MS, we were able to analyze large numbers of samples per day consisting of 0.5 g of hair in 5 mL of nitric acid. Following digestion, the aliquots were examined to determine the quantities of Hg, Pb, Cu, Cd, and Zn. Results: The quantities recovered for all elements were in an acceptable certified value range of (97.60–99.49%). Cu, Zn, and Hg levels examined were higher in the patient group, and Cd and Pb were higher in the control group. In our patients, a positive correlation was found between age, Hg, Cd, Pb values, and the disability score of multiple sclerosis [EDSS], while there was a negative correlation between Zn and Cu values and EDSS. Additionally, female MS patients showed a higher average hair content than males for the elements studied. Both Cd and Hg levels in patients were increased compared to the controls. Lead content in hair is steadily increasing in individuals of two different age groups. Lead content in hair showed an increased trend with age in the 21-35 year and 36-60 age groups. Conclusion: Our study shows some important changes and relationships with Pb. Also, it has been determined that the Pb element increases with age, and the Cd and Hg levels were noticeably different in the patient and healthy groups, and Cu and Zn values change in parallel. The study can be a guide for diagnosis and treatment of the MS.

Development and validation of single-step microwave-assisted digestion method for determining heavy metals in aquatic products: Health risk assessment

A simple, rapid, and environmentally friendly microwave-assisted digestion method was developed and validated to determine heavy metals in aquatic products. The method could digest 640 samples using only one microwave digester in an 8 h working day. Only 2 mL of nitric acid was required to completely digest 0.2 g of samples, significantly reducing the usage of acid. The method was applied to investigate the heavy metals concentrations in mostly consumed aquatic products in Shenzhen. The investigation showed significant differences between different sampling times and sites in the concentrations of heavy metals, implying the necessity of sampling based on multiple times and sites for the accurate determination of heavy metals. Besides, iAs in crab were found to exceed the Chinese standard limit (GB 2762-2022). Health risk assessment showed that Cd and iAs in P. trituberculatus and R. philippinarum posed potential non-carcinogenic and carcinogenic risks to residents’ health.

The effects of processing parameters on structure of mesoporous γ-alumina granules synthesized by sol-gel/oil-drop method: Modelling via response surface methodology

Sol-gel/oil-drop granulation technique was used to prepare mesoporous ?-Al2O3 granules of 1.5-2mm with high specific surface area and pore volume of 295m2/g and 0.47 cm3/g, respectively. The structure of granules was studied using powder XRD, DTA, TEM and N2 adsorption/desorption techniques. A response surface methodology (RSM) holding CCD approach was used for modelling the influence of process variables on the granule pore structure, having a quadratic function relating the independent variables (calcination temperature, acid amount and ammonia concentration) to the responses (specific surface area, mean pore diameter and pore volume). The interaction effect of variables on each response was studied and all were in acceptable accordance with experimental values. Accordingly, the granules synthesized using 20ml of nitric acid, aged in a 9.25wt.% ammonia solution and calcined at 450?C showed the best properties. The predicted values for the specific surface area and pore volume were 315.64m2/g, 7 nm and 0.53 cm3/g, respectively, which were compatible with experimental values.

Multi-element determination in chocolate bars by microwave-induced plasma optical emission spectrometry

Macro- and microelement determination in chocolate bars by microwave-induced plasma optical emission spectrometry (MIP OES) was evaluated after microwave-assisted sample digestion. Optimization of the sample digestion was carried out, and the recommended conditions were obtained at a temperature of 190 °C, with a digestion time of 40 min and in a mixture constituted by 2.3 mL of nitric acid, 1.0 mL of hydrogen peroxide and 4.7 mL of water. The method was applied in the analysis of chocolate bars, and the concentration ranges of the elements determined were (in mg kg−1): Ca (653–3096); Cr (<0.6–2.8); Cu (<0.16–19.5); Fe (<1.6–227); Mg (147–2775); K (3554–8573); Mn (<0.03–25.2); Na (45.6–1095); Ni (3.2–10.2); P (1111–22594) and Zn (4.8–33.3). The association of the proposed microwave-assisted acid digestion with the MIP OES technique was adequate for multi-element determination in chocolate bars for routine analysis.

A Simple and Rapid Analytical Method for the Determination of Nutrient and Toxic Elements in Nut-Based Milk Alternative Beverages by ICP-OES

Plant-based drinks are non-dairy milk alternative beverages that are nowadays widely consumed across the world. Among them, nut-based milk alternative beverages such as almond drink, walnut drink, and peanut drink are gaining more and more popularity. This study presents the development and validation of an inductively coupled plasma–optical emission spectrometry (ICP-OES) method for the determination of nutrient and toxic metals elements in nut-based drinks. The determined metals were Ag, Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, In, Mg, Mn, Ni, Pb, and Zn. The mineralization process of drink samples was optimized in order to achieve complete dissolution. Under optimized conditions, mineralization of 2 g of the nut-based drinks was achieved by the addition of 3 mL of nitric acid and heating at 120°C for 60 min into Teflon autoclaves. The proposed method was validated in terms of linearity, accuracy, precision, limits of detection (LODs), and limits of quantification (LOQs). The relative standard deviations (RSD%) for all elements were 0.4–10.8%, and the relative recovery values (RR%) were 90.0–109.7%, demonstrating that the method offered good precision and accuracy. The LODs for the determined elements were found to be 0.03–1.08 mg kg−1, while the LOQs were found to be 0.10–3.23 mg kg−1. The developed method was successfully employed for the analysis of different commercial nut-based drinks (e.g., almond-based drinks, walnut-based drinks, peanut-based drinks etc.) obtained from the local market.

Analysis of Heavy Metal Contents of Marsilea crenata Presl. Leaves and Soils from East Java Province, Indonesia

Introduction: Marsilea crenata Presl. grows in East Java Province, Indonesia, and showed several pharmacological activities due to its phytoestrogen content. Research indicated its phytoremediation property, and therefore has an impact on heavy metal accumulation in the plants. Lead, cadmium, and mercury are amongst heavy metals that are toxic to the human body. This study aimed to determine and compare Pb, Cd, and Hg mineral contents of soils and leaves of the plants grew in Batu, Pasuruan, Surabaya, and Kediri cities in the province. Method: 10 g of dried powdered leaves and soils were put in separate crucible porcelains, and add 2ml of nitric acid. All were burnt in low heat until white smoke were not formed, and then stood to cool. Ashes obtained were examined using AA 6200 Atomic Absorption Spectrometer (AAS). Result: Showed that leaves samples from the areas showed no Pb and Hg mineral contents that exceeded the permissible limit. Batu City leaf sample had Cd heavy metal content of 2.79 ± 0.01 ppm, which exceeded the permissible limit. Conclusion: Analysis of heavy metal contents of soils from all of the areas showed no exceed limit of Pb and Hg mineral concentrations. Cd soil contents of Surabaya and Kediri cities, were 0.73 ± 0.00 and 2.61 ± 0.08 ppm respectively.

Development and Application of an ICP-AES Method for the Determination of Nutrient and Toxic Elements in Savory Snack Products after Autoclave Dissolution

In this study, a method for the determination of trace elements in snacks using inductively coupled plasma–atomic emission spectrometry (ICP-AES) is presented. The examined elements were Pb, Ni, Cr, Cu, Mg, Zn, Fe, Al, Ba, Ca, Co, Mn and Cd. Under the optimized conditions, digestion of 300 mg of the snack samples was performed by the addition of 5 mL of nitric acid in a Teflon autoclave and by heating the obtained mixture at 120 °C for 75 min. In order to evaluate the efficiency of the proposed protocol, method linearity, accuracy precision, limits of detection (LODs) and limits of quantification (LOQs) were evaluated. The relative standard deviations (RSD%) for all elements were lower than 13.5%, demonstrating that the method offered good precision. The relative recoveries values (R%) ranged between 80–120%, demonstrating that the method offered good accuracy. The LODs for all the trace elements ranged between 0.18 and 3.75 μg g−1, while the LOQs ranged between 0.60 and 12.50 μg g−1. Finally, the proposed protocol was implemented for the analysis of a wide variety of savory snack samples including commercial snacks from corn, potato chips, popcorns, puffed rice cake and crackers.

Evaluation of the phenyl-bonded silica-based sorbent for pre-concentration of the booster antifouling biocides Zinc Pyrithione, Zineb and Ziram using solid-phase extraction technique and Inductively Coupled Plasma Mass Spectrometry

A robust method of solid-phase extraction technique with use of the phenyl-bonded silica-based sorbent (Si-PH sorbent) for pre-concentration of three booster antifouling biocides: zinc pyrithione, Zineb and Ziram in ultrapure water fortified and estuarine water sample was evaluated for zinc determination by collision cell technology-inductively coupled plasma-mass spectrometry (CCT-ICP-MS). Decontamination process to remove metals and prevent (trans-) metallization of the Si-PH sorbent with 20 mL of nitric acid 0.006 mol L-1 was performed. This proposed solid-phase extraction efficiency of three booster antifouling biocides by the phenyl-bonded silica-based sorbent (Si-PH sorbent) was evaluated in 40 mL of ultrapure water fortified sample (40 μg L-1 of the zinc biocides). The adsorption of zinc pyrithione, Zineb and Ziram were 94.2 ± 0.1%, 85.13 ± 0.04% and 93.35 ± 0.09%, respectively. The limit of detection and limit of quantification values obtained were 0.66 μg L-1 and 2.19 μg L-1, respectively. Good recoveries of zinc pyrithione (85 ± 2%), Zineb (89 ± 5%) and Ziram (111 ± 2%) in the elution step for booster antifouling biocides from the fortified estuarine water were obtained.

Simultaneously determination of copper and zinc in human serum and urine samples based on amoxicillin drug by dispersive ionic liquid- liquid microextraction coupled to flame atomic absorption spectrometry

In this work the effect of amoxicillin on copper and zinc (Cu and Zn) deficiency was evaluated by determining of Cu and Zn concentration in human serum and urine samples. By dispersive ionic liquid cloud point extraction procedure (DIL-CPE), 0.03 g of pure amoxicillin drug was added to mixture of 0.1 g of hydrophobic ionic liquid and 0.2 mL acetone which was injected to 2 mL of serum or urine samples which was diluted with DW up to 10 mL. The cloudy solution was shacked for 7 min and Cu and Zn ions was extracted based on sulfur group on amoxicillin ligand at pH of 7 by DIL-CPE. Then, the solution centrifuged and after back extraction with I mL of nitric acid (0.2 M), the remained solution was determined by flame atomic absorption spectrometry (F-AAS).

Facile synthesis of a modified HF-free MIL-101(Cr) nanoadsorbent for extraction nickel in water and wastewater samples

A novel sorbent based on MIL-101(Cr) nanoadsorbent as MOF structure was used for nickel extraction from water and wastewater samples. In this study, 30 mg of MIL-101(Cr) nanoadsorbent dispersed in 50 mL of water or wastewater samples, after sonication and adjusting pH =8.5, the nickel ions was extracted by carboxyl groups of terephthalic acid (MOF-(C6H4 (COO)-2…. Ni2+) by dispersive suspension micro solid phase extraction (DS-μ-SPE).The MOF was separated from liquid phase with filter membrane (0.2 μm), eluted with 0.5 mL of nitric acid as back-extraction solution and finally, the nickel concentration in eluent determined by atom trap-flame atomic absorption spectrometry (AT-FAAS) after dilution with DW up to 1 mL.The LOD, the linear range and preconcentration factor were achieved 1.5 µg L−1, 5-160 µg L−1 and 49.7, respectively.The absorption capacity of MOF for nickel was obtained 136.8 mg g-1.The results of procedure were validated by spiking of samples and ET-AAS analyzer.

Cadmium separation in human biological samples based on captopril-ionic liquid paste on graphite rod before determination by electrothermal atomic absorption spectrometry

A mixture of captopril nanoparticles (CAP-NPs) and ionic liquid (IL, [HMIM] [PF6]) paste on micro graphite rod (CAP-IL-MGR) and was used for separation cadmium in human serum and urine samples by micro solid phase extraction (μ-SPE). 0.01 g of CAP-NPs and 0.1 g of [HMIM] [PF6] mixed with 1 mL of acetone and mixture passed physically on micro graphite rod (MGR) at 55oC. Then, the graphite probe placed on 10 mL of human biological samples with 5 min of sonication, then cadmium ions complexed by thiol group of captopril (CAP-SH) at pH=5.5. The cadmium ions on micro probe were back extracted with 0.25 mL of nitric acid (0.5 M) which was diluted with DW up to 0.5 mL and finally, the cadmium concentration determined by ET-AAS. By optimizing of amount of captopril, the absorption capacity and recovery were obtained 132.4 mg g-1 and more than 96%, respectively.

Analysis of Chemical Composition of Different Irreversible Hydrocolloids.

Irreversible hydrocolloids (IR) is a dental impression material commonly used in Brazilian and European dental practice because it is inexpensive, easy to handle, has good reproductive detail and is comfortable for the patient. This research aimed to analyze the chemical composition of eight different IRs for dental use. A sample of 0.2 g was weighed and transferred to a Teflon beaker moistened with drops of distilled or deionized water; 5 mL of nitric acid was added until total solubility of the sample; the solution was transferred to a 100 mL volumetric flask, the volume was filled with distilled or deionized water and homogenized. Thirty-five chemical elements were found: Lithium, Beryllium, Boron, Sodium, Magnesium, Aluminum, Silicon, Phosphorus, Potassium, Titanium, Manganese, Cobalt, Nickel, Vanadium, Zinc, Rubidium, Arsenic, Iron, Copper, Strontium, Yttrium, Zirconium, Niobium, Molybdenum, Ruthenium, Cadmium, Tin, Antimony, Barium, Lanthanum, Cerium, Mercury, Lead, Thorium and Uranium. Only one of the samples contained no Nickel, Antimony and Lead; and Arsenic and Uranium were found in 2 samples. This study provided evidence of high toxicity of the IR brands, pointing out the need for better quality control of this product, in order to prevent health damage in dentists, prosthesis technicians and patients.

Method Development and Quantitative Elemental Analysis of Mentha Longifolia L. Leaves from Saudi Arabia by Total Reflection X-Ray Fluorescence

ABSTRACTA method has been developed for the quantitative elemental analysis of Mentha longifolia L. leaves collected from different cities in Saudi Arabia using total reflection X-ray fluorescence. Using a microwave digestion system, 100 mg of each sample was completely digested using 3 mL of nitric acid and 2 mL of hydrogen peroxide. The stabilization of the digested samples on the silicon reflectors was studied using a silicone solution and polyvinyl alcohol. 5 µL of either silicone solution or polyvinyl alcohol (1% m/v) was pipetted and dried on the silicon reflector prior to the deposition of the digested samples. It was recognized that there is some enhancement on the intensity of the peak area with the silicone solution at photon energies less than 11 keV. However, the obtained results confirm the ability of using silicone solution or polyvinyl alcohol (1% m/v) as the stabilizer prior to the deposition of the sample droplet on the quartz reflector. However, the silicone solution was more applicable. Based on the developed method, 15 elements were quantified, namely, P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Cu, Zn, Br, Rb, Sr, and Ba. Based on the present quantitative analysis results, M. longifolia samples collected from Al-Madina city had the highest concentration of P, Cl, K, Ti, Fe, Ni, and Cu. The lowest concentrations of P, S, Cl, K, Mn, Ni, and Br were found in Taif-Shafa.

Synthesis of 2-mercaptobenzothiazole/magnetic nanoparticles modified multi-walled carbon nanotubes for simultaneous solid-phase microextraction of cadmium and lead

ABSTRACTThis study describes the successful sequential modification of multi-walled carbon nanotube (MWCNT) by Fe3O4 magnetic nanoparticles and 2-mercaptobenzothiazole (MBT) followed by its application as a novel sorbent for simultaneous magnetic solid phase microextraction of lead and cadmium. Fourier transform infrared spectroscopy and scanning electron microscopy were employed to confirm the chemical surface modification of the MWCNT. The ions retained on the 2-MBT/magnetic nanoparticles modified MWCNTs were eluted with 1.0 mL of nitric acid (0.8 mol L−1) in methanol solution and determined by the flame atomic absorption spectrometry. All parameters affecting the extraction condition were thoroughly investigated and optimised. Under the optimised condition preconcentration factor of 150.0, enhancement factors of 149.0 and 149.2 and limits of detection of 0.21 and 0.01 µg L−1 were achieved for lead and cadmium, respectively. Using the prepared magnetic nanocomposite, the possible interference of other common ions associated with lead and cadmium determination was effectively avoided and the method was successfully applied to the simultaneous determination of the target ions in various environmental water samples.

Otimização multivariada de metodologia para digestão de micropartículas poliméricas carreadoras de cátions metálicos

There are not reports in the literature of digestion processes of metallic cation carrier microparticles. Multivariate experimental designs were utilized to ensure an appropriate digestion for further analysis by atomic absorption spectroscopy. It was used a heater plate and the polimeric degradation was evaluated utilizing an analyzer of total organic carbon (TOC). For the total carbon (TC) content, the full factorial design 24 pointed the significance of sample volume (VAm), in relation to the variables acid volume (VAc), temperature (T) and digestion time (t). However, according to the normal distribution graph it was noted a possible significance of the T and t effects. The same was observed for TOC, including the VAm × VAc × T effect suggestive of complex behavior. In the central composite design all variables were again studied and the VAM was significant, promoting a TC decreasing at the lower evaluated level. By ANOVA a quadratic model without lack of fit was found, with the significant quadratic term. The best digestion condition was: 5.00 mL of sample, 10.00 mL of nitric acid, 60 oC and 90 min. The multivariate optimization allowed an efficient digestion, with the initial carbon concentration of 4.60 mg L-1 decreased to 0.55 mg L-1.

Determination of lead, cadmium and nickel in hennas and other hair dyes sold in Turkey

The concentrations of lead, nickel and cadmium in various hennas and synthetic hair dyes were determined by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS). For this purpose, 1 g of sample was digested using 4 mL of hydrogen peroxide (30%) and 8 mL of nitric acid (65%). The digests were diluted to 15 mL and the analytes were determined by HR-CS GFAAS. All determinations of Pb and Cd were performed using NH4H2PO4 as a modifier. The analytes in hair certified reference materials (CRMs) were found within the uncertainty limits of the certified values. In addition, the analyte concentrations added to hair dye were recovered between 95 and 110%. The limits of detection of the method were 48.90, 3.90 and 12.15 ng g−1 for Pb, Cd and Ni, respectively and the characteristic concentrations were 8.70, 1.42 and 6.30 ng g−1, respectively. Finally, the concentrations of the three analytes in various synthetic hair dyes with different brands, shades and formulae as well as in two henna varieties were determined using aqueous standards for calibration. The concentrations of Pb, Cd and Ni in hair dyes were in the ranges of LOD-0.56 μg g−1, LOD-0.011 ng g−1 and 0.030–0.37 μg g−1, respectively, whereas those in the two hennas were 0.60–0.93 μg g−1, 0.033–0.065 ng g−1 and 0.49–1.06 μg g−1, respectively.