Alex Virgilio

Determination of lead in medicinal plants by high-resolution continuum source graphite furnace atomic absorption spectrometry using direct solid sampling

A procedure is proposed for Pb determination in medicinal plants by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) using direct solid sampling. Among Pd(NO(3))(2), Pd/Mg(NO(3))(2), NH(4)H(2)PO(4) and the W-coated platform tested as chemical modifiers, Pd(NO(3))(2) presented the best performance. Calibration plots (10-1000 pg Pb) with regression coefficients better than 0.999 were typically obtained. Accuracy was checked for Pb determination in five plant certified reference materials. Results were in agreement with reference values at a 95% confidence level (paired t-test). Medicinal plant samples were analyzed by the proposed procedure and line-source GF AAS using slurry sampling as a comparative technique. The RSD was 10% (n=3) for a sample containing 0.88 μg g(-1) Pb. The limit of quantification (dry mass) was 0.024 μg g(-1). The contents of Pb in medicinal plant samples varied in the 0.30-1.94 μg g(-1) range.

Determination of Total Sulfur in Agricultural Samples by High-Resolution Continuum Source Flame Molecular Absorption Spectrometry

The usefulness of molecular absorption was investigated for the determination of total sulfur (S) in agricultural samples by high-resolution continuum source flame molecular absorption spectrometry. The lines for CS at 257.595, 257.958, and 258.056 nm and for SH at 323.658, 324.064, and 327.990 nm were evaluated. Figures of merit, such as linear dynamic range, sensitivity, linear correlation, characteristic concentration, limit of detection, and precision, were established. For selected CS lines, wavelength-integrated absorbance equivalent to 3 pixels, analytical curves in the 100-2500 mg L(-1) (257.595 nm), 250-2000 mg L(-1) (257.958 nm), and 250-5000 mg L(-1) (258.056 nm) ranges with a linear correlation coefficient better than 0.9980 were obtained. Results were in agreement at a 95% confidence level (paired t test) with those obtained by gravimetry. Recoveries of S in fungicide and fertilizer samples were within the 84-109% range, and the relative standard deviation (n=12) was typically <5%.

Evaluation of standard dilution analysis (SDA) of beverages and foodstuffs by ICP OES

A procedure is described using the novel standard dilution analysis (SDA) calibration method for the determination of As, Cd, Cr, Cu, Fe, Mn, Pb, Se and Zn in drinks and foodstuffs by Synchronous Vertical Dual View (SVDV) ICP OES. SDA parameters such as standards concentrations, dilution ratio, signal plateau duration and internal standard element and concentrations were evaluated to improve accuracy, precision and sensitivity. Liquid sweetener, soy sauce, vinegar, grape juice, coconut water, red wine, cachaca (Brazilian sugarcane spirit), beer, energy drink, isotonic and soft drink were analyzed after a 10-fold dilution with 1% v/v HNO3. Spiked samples were analyzed to check the methods accuracy. Recoveries were in the 89–111% range, with precisions better than 4.7%. Results were also compared with values obtained with the traditional calibration methods of external calibration, internal standardization and standard additions. Limits of detection for SDA were in the 3–20 μg L−1 range, which are slightly higher than those obtained using external calibration (0.3–9 μg L−1). Arsenic, Cd and Pb were not found in the samples evaluated. Concentrations determined for the other analytes were in the following ranges: 174 ± 23 μg L−1 Cr, 843 ± 41 μg L−1 Cu, 266–3903 μg L−1 Fe, 1420–6700 μg L−1 Mn, 300–1790 μg L−1 Se, and 1030–14 520 μg L−1 Zn. The SDA-ICP OES method is a simpler and faster alternative to perform matrix-matching with adequate accuracy and precision.

Multi-energy calibration applied to atomic spectrometry

Multi-energy calibration (MEC) is a novel strategy that explores the capacity of several analytes of generating analytical signals at many different wavelengths (transition energies). Contrasting with traditional methods, which employ a fixed transition energy and different analyte concentrations to build a calibration plot, MEC uses a fixed analyte concentration and multiple transition energies for calibration. Only two calibration solutions are required in combination with the MEC method. Solution 1 is composed of 50% v v-1 sample and 50% v v-1 of a standard solution containing the analytes. Solution 2 has 50% v v-1 sample and 50% v v-1 blank. Calibration is performed by running each solution separately and monitoring the instrument response at several wavelengths for each analyte. Analytical signals from solutions 1 and 2 are plotted on the x-axis and y-axis, respectively, and the analyte concentration in the sample is calculated from the slope of the resulting calibration curve. The method has been applied to three different atomic spectrometric techniques (ICP OES, MIP OES and HR-CS FAAS). Six analytes were determined in complex samples (e.g. green tea, cola soft drink, cough medicine, soy sauce, and red wine), and the results were comparable with, and in several cases more accurate than, values obtained using the traditional external calibration, internal standardization, and standard additions methods. MEC is a simple, fast and efficient matrix-matching calibration method. It may be applied to any technique capable of simultaneous or fast sequential monitoring of multiple analytical signals.

Evaluation of Inductively Coupled Plasma Tandem Mass Spectrometry for Determination of As in Agricultural Inputs with High REE Contents

In the present work, an inductively coupled plasma-tandem mass spectrometer (ICP-MS/MS) operating in single quadrupole and mass shift modes were evaluated for As determination in mineral fertilizers and agricultural gypsum with high contents of rare earth elements. For MS/MS mode, oxygen was the gas introduced into the octopole reaction system (ORS3). Samples were prepared by microwave-assisted digestion with diluted nitric acid solution. The accuracy was checked by analysis of a fertilizer certified reference material (NIST SRM 695) and by addition and recovery experiments. When operating in single quadrupole mode, recoveries ranged from 59 to 151%; while values obtained by MS/MS mode varied from 81 to 105% when 0.30 mL min-1 O2 was introduced into the ORS3. Limits of detection for As+ in single quadrupole and AsO+ in MS/MS mass shift mode were 6 and 9 ng L-1, respectively.

Determination of Cd, Ni and V in Spices by Solid Sampling High-Resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry

This work describes a procedure for determination of Cd, Ni and V in spices by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) using direct solid sampling (SS). The use of Pd/Mg(NO3)2 as modifier for Cd, and an additional air-assisted pyrolysis step allowed the use of aqueous calibration for all analytes. Accuracy was checked by analysis of certified reference materials (CRMs) and the results were in agreement to certified values at 95% confidence level (t-test). Eight samples of spices were analyzed by the proposed procedure and by inductively coupled plasma mass spectrometry (ICP-MS). The found concentrations were 88-233 ng g-1 Cd , 113-2842 ng g-1 Ni and 154-1007 ng g-1 V, with precision generally better than 12%. Results obtained by the proposed procedure were in agreement with those obtained by microwave-assisted digestion and ICP-MS determination. The limits of detection were 0.2, 18 and 7 ng g-1 for Cd, Ni and V, respectively.

Critical evaluation of internal standardization in ICP tandem mass spectrometry and feasibility of the oxygen reaction for boron determination in plants

The feasibility of internal standardization and the oxygen reaction in ICP-MS was studied for accurate determination of boron. Lithium, Be and Rh were systematically evaluated as internal standards (I.S.) for B determination in plants by ICP-MS/MS using a single quadrupole mode and MS/MS mode with O2 into a cell, where B and internal standard signal intensities were processed either after both or only one of them reacted. Carbon is a source of spectral and matrix interferences in B determination by ICP-MS. The use of instrumental strategies such as tandem mass spectrometry (MS/MS) concomitantly with internal standardization demands further investigation about the I.S. behaviour regarding the gas phase reaction with oxygen. The behaviours of B and Be, as well as their oxides, were quite similar in an octopole reaction system containing O2. The coexistence of spectral and non-spectral interferences was evidenced by increasing carbon concentrations in samples and checking positive errors caused for 11B+. Recoveries for B determination in plant certified reference materials without I.S. ranged from 98 to 145% and with Be as an internal standard ranged from 98 to 108%. Beryllium presented favourable characteristics as an internal standard for B due to its mass closeness, similar ionization energy, and reactivity with oxygen.

Determination of Elemental Content in Solder Mask Samples Used in Printed Circuit Boards Using Different Spectroanalytical Techniques

Solder masks are essential materials used in the manufacture of printed circuit boards (PCB). This material protects PCBs against several types of damage and performance failure. In this study, the capabilities of laser-induced breakdown spectroscopy (LIBS) were investigated for the direct analysis of solder masks typically commercialized for homemade PCB production, and inductively coupled plasma–optical emission spectrometry (ICP-OES) was used to obtain a chemical profile for the target analytes Al, As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Sb, Sn, and Zn. Inductively coupled plasma–mass spectrometry (ICP-MS) was also employed for the determination of potentially toxic elements, such as As, Cd, Cr, Pb, and Hg. In addition to the qualitative information that may be useful for obtaining the spectral profile related to the raw materials present in solder masks formulations, LIBS was also applied for major elements (Al, Ba, Cu, Fe, Mg, and Zn) determination, but due to the low sensitivity, the obtained results were only semi-quantitative for Ba. Regarding Cd, Cr, Hg, and Pb, the samples analyzed were following the restriction of hazardous substances (RoHS) directive of the European Union.

Elemental Analysis of Phytotherapeutic Products by Inductively Coupled Plasma-Tandem Mass Spectrometry

ABSTRACT A procedure for the determination of As, Cd, Cr, Ni, Pb, and V in phytotherapy medicines by inductively coupled plasma–tandem mass spectrometry is reported. The use of tandem mass spectrometry with oxygen into an octopole reaction system at various gas flow rates and the combination of on-mass and mass-shift modes was evaluated. Cadmium, Cr, Ni, and Pb were determined as free atomic ions while As and V were determined as the oxides AsO+ and VO+ in the same run. Samples were prepared by microwave-assisted digestion with dilute nitric acid and hydrogen peroxide. Two plant-certified reference materials (apple leaves and tomato leaves) were used to check the accuracy. For tandem mass spectrometry with 0.5 mL min−1 O2, recoveries in the 85–113% were typically obtained and no statistical differences were observed at the 95% confidence level (t-test) in comparison with the certified values. Using these conditions, the limits of detection for the method were 0.01, 0.0002, 0.008, 0.008, 0.003, and 0.002 µg g−1 for As, Cd, Cr, Ni, Pb, and V, respectively. The procedure was used for the analysis of four phytotherapic drugs and the determined concentrations were up to 0.168 µg g−1 As, 0.03 µg g−1 Cd, 0.82 µg g−1 Cr, 1.18 µg g−1 Ni, 0.52 µg g−1 Pb, and 2.4 µg g−1 V with average precision values of 8% as the relative standard deviation. The found concentrations were compared with limits proposed in official guidelines and, in most cases, the values were below the maximum limits allowed.

Determination of copper at wide range concentrations using instrumental features of high-resolution continuum source flame atomic absorption spectrometry.

This work describes a method to determine Cu at wide range concentrations in a single run without need of further dilutions employing high-resolution continuum source flame atomic absorption spectrometry. Different atomic lines for Cu at 324.754 nm, 327.396 nm, 222.570 nm, 249.215 nm and 224.426 nm were evaluated and main figures of merit established. Absorbance measurements at 324.754 nm, 249.215 nm and -1 -1 -1 224.426 nm allows the determination of Cu in the 0.07 - 5.0 mg L , 5.0 - 100 mg L and 100 - 800 mg L concentration intervals respectively with linear correlation coefficients better than 0.998. Limits of detection -1 -1 -1 were 21 µg L , 310 µg L and 1400 µg L for 324.754 nm, 249.215 nm and 224.426 nm, respectively and relative standard deviations (n = 12) were £ 2.7%. The proposed method was applied to water samples spiked with Cu and the results were in agreement at a 95% of confidence level (paired t-test) with those obtained by line-source flame atomic absorption spectrometry.