A graphite furnace electrothermal vaporization system for inductively coupled plasma atomic emission spectrometry

An improved graphite furnace electrothermal vaporization device equipped with an autosampler for inductively coupled plasma atomic emission spectrometry is presented. The transport losses of eight selected analytes in the individual segments of the device were determined by means of the radiotracer technique by applying amounts traced comparable to those to be determined in real samples. The results obtained from the radiotracer study were the basis for further improvement of the interface design, leading to considerable increase of the total transport efficiency, which finally was found to be between 26 (for Cr) and 57% (for Ga). The whole system consists of a graphite furnace vaporizer, a power supply, a gas flow box, and an autosampler with incorporated microbalance. The temperature program, gas flows, and autosampler functions are controlled by a data station which also provides the data acquisition and processing of the transient signals. The performance parameters of the developed system were evaluated using aqueous standard solutions. Absolute limits of detection for most analytes were between 0.1 and 1 ng, and for As, K, Ni and Pb, they were between 2 and 3.2 ng.     

A large bore-direct injection high efficiency nebulizer for inductively coupled plasma spectrometry

A large bore-direct injection high efficiency nebulizer (IB-DIHEN) is introduced that is less prone to capillary blockage and optimally operates at low nebulizer gas pressures compared with the conventional DIHEN used for inductively coupled plasma (ICP) spectrometries. The aerosol quality is examined using a two-dimensional phase Doppler particle analyzer (2D PDPA), and analytical figures of merits are acquired by ICP mass spectrometry. Compared with the DIHEN, the LB-DIHEN produces larger droplets, but the velocity distributions and mean droplet velocities are narrower and lower, respectively, providing longer residence times for the droplets in the plasma. High RF power (1500 W), low nebulizer gas flow rates (0.25-0.35 L/min), and low solution uptake rates (80-110 microL/min) are required to operate the LB-DIHEN at optimum conditions for ICPMS. Detection limits and sensitivities measured with the LB-DIHEN are superior to those of a conventional nebulizer-spray chamber combination, but precision is inferior. The performance of the LB-DIHEN is further explored in the determination of trace elements in an herbal extract.     

Preliminary investigation of electrothermal vaporization sample introduction for inductively coupled plasma time-of-flight mass spectrometry

The coupling of an electrothermal vaporization (ETV) apparatus to an inductively coupled plasma time-of-flight mass spectrometer (ICP-TOFMS) is described. The ability of the ICP-TOFMS to produce complete elemental mass spectra at high repetition rates is experimentally demonstrated. A signal-averaging data acquisition board is employed to rapidly record complete elemental spectra throughout the vaporization stage of the ETV temperature cycle; a solution containing 34 elements is analyzed. The reduction of both molecular and atomic isobaric interferences through the temperature program of the furnace is demonstrated. Isobaric overlaps among the isotopes of cadmium, tin, and indium are resolved by exploiting differences in the vaporization characteristics of the elements. Figures of merit for the system are defined with several different data acquisition schemes capable of operating at the high repetition rate of the TOF instrument. With the use of both ion counting and a boxcar averager, the dynamic range is shown to be linear over a range of at least 6 orders of magnitude. A pair of boxcar averagers are used to measure the isotope ratio for silver with a precision of 1.9% RSD, despite a cycle-to-cycle precision of 19% RSD. Detection limits of 10-80 fg are calculated for seven elements, based upon a 10-microL injection.     

Determination of impurities in aluminum isopropoxide by inductively coupled plasma atomic emission spectrometry

A procedure has been developed for the determination of impurities in aluminum isopropoxide by inductively coupled plasma atomic emission spectrometry. The matrix effect has been compensated by adding a Bi internal standard. The detection limits of impurities are 10⁻⁷ to 10⁻⁵ wt %.     

Signal fluctuations due to individual droplets in inductively coupled plasma atomic emission spectrometry

Large emission intensity fluctuations are observed from analyte species in inductively coupled plasmas. Relative standard deviations are as large as 71% when emission is viewed with time resolution of 10 microseconds. Low in the plasma, peaks in atom emission intensity are accompanied by depressions in ion emission. This behavior appears to be due to local cooling by aerosol droplets. High in the plasma, peaks in atom emission are followed by peaks in ion emission. These emission spikes result from atomization and ionization of analyte from vaporizing particles. Laser light scattering experiments show that droplets or particles exist in a conventional 1.0-kW plasma up to 20 mm above the load coil. Emission signals detected high in the plasma correlate with laser light scattering signals below.     

Development and application of acousto-optic background correction for inductively coupled plasma atomic emission spectrometry

In two configurations, a solid-state acousto-optic (AO) deflector or modulator is mounted in a 0.5 m monochromator for background correction with inductively coupled plasma atomic emission spectrometry (ICP-AES). A fused silica acousto-optic modulator (AOM) is used in the ultraviolet (UV) spectral region applications while a glass AO deflector (AOD) is used for the visible (VIS) region. The system provides rapid sequential observation of adjacent on- and off-line wavelengths for background correction. Seventeen elements are examined using pneumatic nebulization (PN) and electrothermal vaporization (ETV) sample introduction. Calibration plots were obtained with each sample introduction technique. Potable water and vitamin tablets were analyzed. Flame atomic absorption (FAA) was used to verify the accuracy of the AO background correction system.     

ICP-AES法测定螺旋藻中的杂质元素铝

探讨用ICP-AES技术测定螺旋藻中杂质元素铝,并对共存元素光谱干扰及其消除进行研究,所建立的分析方法,快速、结果准确,有较好的精密度和准确度,适用于螺旋藻中铝的测定。     

Ultrasound bath-assisted enzymatic hydrolysis procedures as sample pretreatment for the multielement determination in mussels by inductively coupled plasma atomic emission spectrometry

Ultrasound energy has been applied to speed up enzymatic hydrolysis processes of mussel tissue in order to determine trace and ultratrace elements (As, Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn). The element releases, by action of three proteases (pepsin, pancreatin, trypsin), lipase, and alpha-amylase, have been evaluated by inductively coupled plasma atomic emission spectrometry. Different variables such as pH, sonication temperature, ionic strength, hydrolysis time, ultrasound frequency, extracting volume, and enzyme mass were simultaneously studied by applying an experimental design approach (Plackett-Burman design and central composite design). Results showed that the hydrolysis time was statistically nonsignificant (confidence interval of 95%) for most of the elements and enzymes, meaning that the hydrolysis procedure can be finished within a 30-60-min range. These hydrolysis times are far shorter than those obtained when using thermostatic cameras, between 12 and 24 h. Statistically significant factors were the ultrasound frequency (the highest metals releasing at high-ultrasound frequency), pH, sonication temperature, and ionic strength. All metals can be extracted using the same operating conditions (pH of 1.0 and sodium chloride at 1.0% for pepsin; pH of 7.5, temperature at 37 degrees C, and 0.4 M potassium dihydrogen phosphate/potassium hydrogen phosphate buffer for amylase; pH of 8.0 and 0.5 M potassium dihydrogen phosphate/potassium hydrogen phosphate buffer for pancreatin; pH of 5.0 and 0.5 M potassium dihydrogen phosphate/potassium hydrogen phosphate buffer for lipase; pH of 8.0 and 0.2 M potassium dihydrogen phosphate/potassium hydrogen phosphate buffer for trypsin). Analytical performances, such as limits of detection and quantification, repeatability of the overall procedure, and accuracy, by analyzing DORM-1, DORM-2, and TORT-1 certified reference materials, were finally assessed for each enzyme.     

Time-resolved inductively coupled plasma mass spectrometry measurements with individual, monodisperse drop sample introduction

Individual ion clouds, each produced in the ICP from a single drop of sample, were monitored using time-resolved mass spectrometry and optical emission spectrometry simultaneously. The widths of the ion clouds in the plasma as a function of distance from the point of initial desolvated particle vaporization in the ICP were estimated. The Li(+) cloud width (full width at halfmaximum) varied from 85 to 272 μs at 3 and 10 mm from the apparent vaporization point, respectively. The Sr(+) cloud width varied from 97 to 142 μs at 5 and 10 mm from the apparent vaporization point, respectively. The delays between optical and mass spectrometry signals were used to measure gas velocities in the ICP. The velocity data could then be used to convert ion cloud peak widths in time to cloud sizes in the ICP. Li(+) clouds varied from 2.1 to 6.6 mm (full width at half-maximum) and Sr(+) clouds varied from 2.4 to 3.5 mm at the locations specified above. Diffusion coefficients were estimated from experimental data to be 88, 44, and 24 cm(2)/s for Li(+), Mg(+), and Sr(+), respectively. The flight time of ions from the sampling orifice of the mass spectrometer to the detector were mass dependent and varied from 13 to 21 μs for Mg(+) to 93 to 115 μs for Pb(+).     

Analysis of pure scandium,yttrium, and their oxides using methods of inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry

The analytical possibilities of direct detection of rare earth and non-rare-earth impurities in pure scandium, yttrium, and their oxides using the ICP-AES and ICP-MS methods are investigated. The analytical lines and isotopes of the sought elements that are the most free from folding are selected. The effect of the sought impurities of the matrix elements on the analytical signal is studied. The detection and determination limits for impurities in scandium and yttrium are estimated. The lower limits of determining impurities in scandium, yttrium, and their oxides at the level of n × 10⁴ mass fractions, %, are reached using the ICP-AES method; those at the level of n × 10⁻⁶ mass fractions, %, are reached using the ICP-MS method. The joint application of the ICP-AES and ICP-MS methods for the analysis of standard specimens of yttrium and scandium oxide is implemented. The control of the validity is accomplished by comparing the obtained results with the certified values of standard specimens and by the method of addition.     

Sample preconcentration using ion-exchange polymer film for laser ablation sampling inductively coupled plasma atomic emission spectrometry

An efficient sample pretreatment/introduction technique for the inductively coupled plasma atomic emission spectrometry (ICP-AES) using ion exchange for analyte preconcentration and matrix separation and laser ablation sampling for sample introduction has been developed. Ammonium pyrrolidine dithiocarbamate (APDC)-polystyrene films are coated on glass plates for analyte preconcentration. Repetitive laser ablation sampling of the polymer film removes the ion-exchanged metal ions from the polymer film as fine particles for sample introduction into the ICP. After immersing the sample probe in a sample solution for 5 min, the ICP emission intensity for laser ablation of the polymer film is a few times larger than that after solution nebulization. The sample probe removes only a small fraction of the sample solution and, therefore, in principle, does not disturb the original solution significantly. Single-pulse laser ablation of the polymer film shows that the ion-exchanged metal ion concentration in the film reduces exponentially with the depth of the polymer film. Ion exchange to the polymer film is probably limited by the rate of metal ion diffusion into the film. Calibration curves for Cu, Hg, Pb, and Zn show linear dynamic range of ～1-2 orders of magnitude. The linear dynamic range for Cu increases to >3 orders of magnitude when using Pb as an internal standard. RSD of the ICP emission intensity is ～8%.     

Determination of platinum and palladium in dead catalysts using inductively coupled plasma atomic emission spectrometry after sample digestion by high-temperature fusion

A technique for the determination of platinum and palladium in dead catalysts using ICP-AES after sample digestion by high-temperature fusion with potassium pyrosulfate is described. The technique is universal; it offers the possibility to analyze various brands of catalysts and their mixtures at a content of platinum and palladium of 0.1% to whole units of percent in a short time. The accuracy of results of determination of platinum and palladium is confirmed by comparison with the data of interlaboratory control. The relative standard deviation in the developed technique is 4–2.5% for the content of platinum and palladium of 0.1 to 0.5% and 2–1% for higher concentrations of these elements.