Nebulizer Gas Flow Rate Research Articles

Chemical Fingerprinting by HPLC-DAD-ELSD and Principal Component Analysis of Polygala japonica from Different Locations in China

Aim To establish a high performance liquid chromatographic fingerprint for the quality control of Polygala japonica, a raw material of traditonal Chinese medicine (TCM). Methods The fingerprint was established using HPLC-DAD-ELSD techniques. Chromatographic fingerprint analysis was carried out on a Discovery C 18 analytical column. The mobile phase consisting acetonitrile-methanol-0.05% trifluoroacetic acid (TFA) in gradient program. DAD acquisition wavelength range was set from 200 to 400 nm and the chromatographic display wavelength was set at 350 nm. The evaporator tube temperature of ELSD was set at 105 °C, and with the nebulizing gas flow-rate of 2.6 L·min −1. Results In the DAD chromatogram most peaks showed the characteristic spectra of flavonol derivatives (260 nm, 350 nm), and in the ELSD chromatogram most peaks were identified as triterpenoid saponins by comparsion with that of reference standards. The complementary information between the DAD and ELSD fingerprints was evaluated and the PCA of the fingerprint data led to an accurate classification of various samples from different locations. Conclusion It was demonstrated that the HPLC-DAD-ELSD fingerprint was a powerful tool to characterize the quality of traditional Chinese medicines.

Optimization of the operating conditions using factorial designs for determination of uranium by inductively coupled plasma optical emission spectrometry

A critical evaluation of the determination of uranium by inductively coupled plasma optical emission spectrometry was performed using factorial designs (2 3) involving the factors: acid concentration, radio frequency power and nebulizer gas flow rate. All of the experiments in this study were made for five emission lines, in the presence of nitric and hydrochloric acid. The results demonstrated that, between nitric and hydrochloric acid, the determinations in the presence of nitric acid were most sensitive. The factorial design showed that the nebulizer gas flow rate was the most significant among the factors studied for the five emission lines. Calcium in concentrations of 10 mg L −1 was observed to cause suppression of the emission intensity for some lines. Iron (at least up to 10 mg L −1) did not interfere in the emission intensity of uranium across the five lines studied. Another experiment evaluated simultaneously the effect of 13 other elements, and the results demonstrated that these elements did not affect the emission intensity of uranium for the lines chosen. The optimized method, using the line at 385.957 nm, allows the determination of uranium with limit of quantification of 31 μg L −1 and precision expressed as RSD lower than 2.2% for uranium concentrations of either 500 or 1000 μg L −1. The accuracy was confirmed by analysis of two laboratory reference materials. The developed method was applied to the determination of uranium in an industrial effluent collected from uranium-producing mine in Caetite City, Brazil. The sample was analyzed by inductively coupled plasma mass spectrometry ICP-MS, and the observed recovery was satisfactory.

Determination of multicomponent contents in Calculus bovis by ultra‐performance liquid chromatography–evaporative light scattering detection and its application for quality control

A fast ultra-performance liquid chromatography-evaporative light scattering detection (UPLC-ELSD) method was established for simultaneous quantification of seven components in natural Calculus bovis (C. bovis) and its substitutes or spurious breeds. On a Waters Acquity UPLC BEH C(18) column, seven analytes were efficiently separated using 0.2% aqueous formic acid-acetonitrile as the mobile phase in a gradient program. The evaporator tube temperature of ELSD was set at 100 degrees C with the nebulizing gas flow-rate of 1.9 L/min. The results showed that this established UPLC-ELSD method was validated to be sensitive, precise and accurate with the LODs of seven analytes at 2-11 ng, and the overall intra-day and inter-day variations less than 3.0%. The recovery of the method was in the range of 97.8-101.6%, with RSD less than 3.0%. Further results of PCA on the contents of seven investigated analytes suggested that compounds of cholic acid, deoxycholic acid and chenodeoxycholic acid or cholesterol should be added as chemical markers to UPLC analysis of C. bovis samples for quality control and to discriminate natural C. bovis sample and its substitutes or some spurious breeds, then normalize the use of natural C. bovis and ensure its clinical efficacy.

Direct Determination of Dy, Sm, Eu, Tm, and Yb in Geological Samples by Slurry Electrothermal Vaporization Inductively Coupled Plasma Mass Spectrometry

Slurry sample introduction with electrothermal vaporization (ETV) has been applied to inductively coupled plasma mass spectrometry (ICP-MS) for the direct determination of Dy, Sm, Eu, Tm, and Yb in geological samples. The slurries were prepared by mixing 50 mg of the powdered sample, sediment or soil (≤50 µm) with 0.8 mL of 65% m/v nitric acid, 0.4 mL of 40% m/v hydrofluoric acid and 0.4 mL of 30% v/v hydrogen peroxide in PTFE flasks. The mixture was submitted to an ultrasonic bath for 36 min and then diluted to 14 mL with water. The best compromise conditions for the furnace temperature program, the nebulizer gas flow rate, the RF power, and the amount of NaCl used as carrier were determined. By introducing 20 µL of 3.57 mg mL−1 sediment slurry, using 50 µg of NaCl as a physical carrier, and pyrolysis and vaporization temperatures of 1000°C and 2800°C, respectively, the obtained values for four geological reference materials were well within the certified range, using external calibration with aqueous solutions. Under the optimum operating conditions, the detection limits for 164Dy, 152Sm, 153Eu, 169Tm e, 174Yb were of 200, 30, 20, 10, and 10 pg g−1, respectively. The precision was better than 10%.

Perturbations produced by electrospray ionization mass spectrometry in the speciation of aluminium(III)/1,6‐dimethyl‐4‐hydroxy‐3‐pyridinecarboxylate aqueous solutions

Electrospray ionization mass spectrometry (ESI-MS) is very often employed to study metal/ligand equilibria in aqueous solution. However, the ionization process can introduce perturbations which affect the speciation results in an unpredictable way. It is necessary to identify these perturbations in order to correctly interpret the ESI-MS speciation results. Aluminium(III)/1,6-dimethyl-4-hydroxy-3-pyridinecarboxylate (DQ716) aqueous solutions at various pH were analysed by ESI-MS, and speciation results were compared with those obtained by equilibrium techniques. Differences observed were both qualitative and quantitative. The ESI-MS spectral changes due to different settings of the following instrumental parameters were analyzed: the solution flow rate (F(S)), the nebulizer gas flow rate (F(G)), the potential applied at the entrance capillary (E(C)), and the temperature of the drying gas (T(G)). The effects produced by F(S) and E(C) on the spectra strongly suggest the key role of surface activity in determining the relative fraction of the ions reaching the detector. The experimental effects of F(S) and T(G) were interpreted considering the presence of at least two reactions in the gas phase and a dimerization occurring in the droplets. These perturbations cannot be generalized because they appear to be chemical system-related and instrument-dependent. Therefore, the identification of perturbations is a required task for any metal-ligand equilibrium study performed by ESI-MS. Our results indicate that perturbations can be identified by evaluating the effects produced in the spectra by a change of instrumental parameters.

Atmospheric pressure thermospray ionization using a heated microchip nebulizer

When a standard atmospheric pressure chemical ionization (APCI) or atmospheric pressure photoionization (APPI) ion source is used without applying the corona discharge or photoirradiation, atmospheric pressure thermospray ionization (APTSI) of various compounds can be achieved. Although largely ignored, this phenomenon has recently gained interest as an alternative ionization technique. In this study, this technique is performed for the first time on a miniaturized scale using a microchip nebulizer. Sample ionization with the presented microchip-APTSI (microAPTSI) is achieved by applying only heat and gas flow to a nebulizer chip, without any other methods to promote gas-phase ionization. To evaluate the performance of the described microAPTSI setup, ionization efficiency for a set of test compounds was monitored as the microchip positioning, temperature, nebulizer gas flow rate, sample solution composition, and solvent flow rate were varied. The microAPTSI mass spectra of the test compounds were also compared to those obtained with ESI and APCI. The microAPTSI produces ESI-like spectra with low background noise, favoring the formation of protonated or deprotonated molecules of compounds that are ionizable in solution. Multiple charging of peptides without in-source fragmentation was also observed. Unlike ESI, however, the microAPTSI source can tolerate the presence of mobile phase additives like trifluoroacetic acid (TFA) without significant ion suppression. The microAPTSI source can be used with standard mass spectrometer ion source hardware, being a unique alternative to the present interfacing techniques.

Multivariate optimization by exploratory analysis applied to the determination of microelements in fruit juice by inductively coupled plasma optical emission spectrometry

A method for the direct determination (without sample pre-digestion) of microelements in fruit juice by inductively coupled plasma optical emission spectrometry has been developed. The method has been optimized by a 2 3 factorial design, which evaluated the plasma conditions (nebulization gas flow rate, applied power, and sample flow rate). A 1:1 diluted juice sample with 2% HNO 3 (Tetra Packed, peach flavor) and spiked with 0.5 mg L − 1 of Al, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Sn, and Zn was employed in the optimization. The results of the factorial design were evaluated by exploratory analysis (Hierarchical Cluster Analysis, HCA, and Principal Component Analysis, PCA) to determine the optimum analytical conditions for all elements. Central point condition differentiation (0.75 L min − 1 , 1.3 kW, and 1.25 mL min − 1 ) was observed for both methods, Principal Component Analysis and Hierarchical Cluster Analysis, with higher analytical signal values, suggesting that these are the optimal analytical conditions. F and t-student tests were used to compare the slopes of the calibration curves for aqueous and matrix-matched standards. No significant differences were observed at 95% confidence level. The correlation coefficient was higher than 0.99 for all the elements evaluated. The limits of quantification were: Al 253, Cu 3.6, Fe 84, Mn 0.4, Zn 71, Ni 67, Cd 69, Pb 129, Sn 206, Cr 79, Co 24, and Ba 2.1 µg L − 1 . The spiking experiments with fruit juice samples resulted in recoveries between 80 and 120%, except for Co and Sn. Al, Cd, Pb, Sn and Cr could not be quantified in any of the samples investigated. The method was applied to the determination of several elements in fruit juice samples commercialized in Brazil.

Simultaneous analysis of eight bioactive steroidal saponins in Gongxuening capsules by HPLC-ELSD and HPLC-MSn

Summary Rapid high-performance liquid chromatographic methods with evaporative light scattering detection (HPLC-ELSD) and electrospray ionization multistage mass spectrometry (HPLC-ESI-MSn) have been established and validated for simultaneous qualitative and quantitative analysis of eight steroidal saponins in ten batches of Gongxuening capsule (GXN), a widely commercially available traditional Chinese preparation. The optimum chromatographic conditions entailed use of a Kromasil C18 column with acetonitrile-water (30:70 to 62:38, υ/υ) as mobile phase at a flow rate of 1.0 mL min−1. The drift tube temperature of the ELSD was 102°C and the nebulizing gas flow rate was 2.8 L min−1. Separation was successfully achieved within 25 min. LC-ESI-MSn was used for unequivocal identification of the constituents of the samples by comparison with reference compounds. The assay was fully validated for precision, repeatability, accuracy, and stability, then successfully applied to quantification of the eight compounds in samples. The method could be effective for evaluation of the clinical safety and efficacy of GXN.

Comparison of interface cones for analysis of sodium-rich samples using quadrupole ICP-MS

This study compares analytical figures of merit such as sensitivity, background, % 140Ce16O+/140Ce+, 40Ar16O+, time dependent and matrix induced interference effects for solutions containing up to 500 mg L−1Na for a conventional sampler cone designated as the High Performance Interface (HPI) with that obtained with a so-called Xi cone. HPI counts were higher than those observed using the Xi cone by factors of about 10 at low mass, the difference decreasing with increasing mass, and at high mass they were approximately equal to those observed with the Xi cone. As a consequence of low sensitivity when using the Xi interface, there is potential for determining high concentrations of low mass elements. The 4-times lower 40Ar16O+ signals and up to two times lower % 140Ce16O+ of the Xi cone are important analytical figures of merit for minimizing polyatomic ion interferences. % 140Ce16O+/140Ce+ varied considerably with depth of sampling and were much higher in the HPI cone than in the Xi cone at large depths of sampling. Na-induced variations were mass dependent and larger in the Xi cone than in the HPI cone, amounting to about 25 and 60%, respectively. Long-term variations for 250 min amounted to about 10 and 25%, respectively. It is concluded that the HPI cone when coupled to a robust ICP (power > 1.3 kW, nebulizer gas flow rate < 0.85 L min−1) is more suited for routine analysis of environmental samples. However, in cases where oxide ion interferences must be reduced and high concentrations of low mass analytes are to be determined, the Xi cone has advantages.

Heated-spray chamber-based low sample consumption system for inductively coupled plasma spectrometry

A systematic study about the effect of the heating of a modified version of the so-called Torch Integrated Sample Introduction System (TISIS) has been performed. The results showed that when working at liquid flow rates of 20–40 µl min−1, it was possible to raise the chamber wall temperature up to 100 °C without degradation of plasma thermal characteristics. Furthermore, a sheathing gas stream was added to the spray chamber so as to improve the aerosol transport towards the plasma. Under these conditions, sensitivity enhancements ranging from 8 to 15 with regard to those found under standard conditions (i.e., with neither chamber heating nor sheathing gas inlet) were reached for the different ionic and atomic emission lines studied. As a result, limits of detection at 20 µl min−1 were improved by a factor between 2.5 and 13. These LODs were only 1.7 to 2 times lower than for a cyclonic spray chamber at an uptake rate of 1 ml min−1. Two direct injection nebulizers were used for comparison: the conventional direct injection high efficiency nebulizer (DIHEN) and its demountable version (d-DIHEN). When TISIS was used under standard conditions quite similar results were found as those provided by d-DIHEN, although at low nebulizer gas flow rates (i.e., 0.1 l min−1), the DIHEN gave rise to higher sensitivities. However, by heating the TISIS chamber at 100 °C, sensitivities were enhanced by a factor up to one order of magnitude with respect to both the DIHEN and d-DIHEN. The result was ascribed both to the production of a finer tertiary aerosol and to the improved plasma excitation conditions. Furthermore, lower limits of detection were encountered for the hot chamber as compared to direct injection nebulizers. Hence, the developed system could be considered to be very promising for the analysis of very low liquid sample volumes through ICP techniques.

Method development and validation of simultaneous determination of seventeen metals in water by ICP/MS

A simple, precise, accurate, and sensitive method is developed and validated for simultaneous determination of seventeen metals (Li, Sr, Ba, Tl, Pb, Bi, Al, K, Cr, Mn, Co, Ni, Cu, Zn, Mo, Ag, and Cd) in water by ICP-MS. The optimum conditions of the ICP-MS are as follows: nebulizer gas (argon) flow rate: 0.9 L/min, auxiliary gas (argon) flow 0.3 L/min, plasma (argon) gas flow: 15 L/min, reaction gas flow (helium) 4mL/min. This method is validated according to the requirements for new methods, which include linearity and range, accuracy, precision, selectivity, limit of detection (LOD), and limit of quntitation (LOQ). The current method demonstrates good linearity over the range of 1-1000 ppb with r2 greater than 0.999 for the seventeen metals. The recovery of the metals from water samples ranges from 97.5 to 101.7%. The method is selective where minimal interferences between the metals is observed (CeO/Ce = 1%, and Ce+2/Ce+1 = 1%), and with good resolution (0.8 amu at 10% height). The method is also precise where the RSD of the responses (cps) of replicates of the metals at three concentration levels is less than 1%. Low LOD and LOQ of metals using this method enable the detection and quantitation of these metals at low concentrations. Real water samples from West Bank in Palestine (groundwater) were analyzed for their trace metals content using this method.

Simultaneous determination of jujuboside A, B and betulinic acid in semen Ziziphi spinosae by high performance liquid chromatography-evaporative light scattering detection

A reverse phase high performance liquid chromatographic (HPLC) method with evaporative light scattering detection (ELSD) was developed for simultaneous determination of jujuboside A, B and betulinic acid in semen Ziziphi spinosae. The analysis was performed by gradient elution, using an aqueous mobile phase (containing 0.1% acetic acid) modified by acetonitrile. The evaporator tube temperature of ELSD was set at 45 °C, and with the nebulizing gas flow-rate of 1.8 l/min. The method was validated for accuracy, reproducibility, precision and limits of detection and quantification. Quantification of the three active compounds in semen Ziziphi spinosae from different locations was performed by this method, which provides a new tool for quality assessment of semen Ziziphi spinosae.

Metal–ligand solution equilibria studied by electrospray ionization mass spectrometry: effect of instrumental parameters

Electrospray ionization mass spectrometry (ESI-MS) is being increasingly employed in the study of metal-ligand equilibria in aqueous solution. In the present work, the ESI-MS spectral changes due to different settings of the following instrumental parameters are analyzed: the solution flow rate (F(S)), the nebulizer gas flow rate (F(G)), the sprayer potential (E), and the temperature of the entrance capillary (T). Twenty-eight spectra were obtained for each of six samples containing aluminum(III) and 2,3-dihydroxypyridine at various pH, in the absence or in the presence of a buffer and of sodium ions. Among the considered instrumental parameters, T produced the largest effects on the ionic intensities. F(S) and F(G) affected the ESI-MS spectra to a lower extent than T. In the investigated conditions E had the weakest effects on the spectra.The correlations observed between the ionic intensities and these instrumental parameters were interpreted considering the presence of three kinds of perturbations occurring in the ESI-MS ion source: formation of some dimers in the droplets, different transfer efficiencies from the droplets to the gas phase for different complexes (according to their surface activity), and subsequent partial thermal decomposition of the dimers and of one of the monomeric complexes in the gas phase. Our results show that the evaluation of the effects produced in the ESI-MS spectra by a change of instrumental parameters can allow to identify the perturbations occurring when metal-ligand solutions are studied by ESI-MS.

A new insight into suction and dilution effects in capillary electrophoresis coupled to mass spectrometry via an electrospray ionization interface. Part I‐Suction effect

The hyphenation of CE with MS is nowadays accepted as a powerful analytical approach. Employing ESI, the most common interface, one challenge is to provide quantitative information, which is quite a difficult task, as it is linked, among other factors, to suction and dilution effects. In the coaxial ESI configuration, the suction effect has been presented in literature as stemming from nebulizing gas (NG) flow rate and drying gas temperature. But as this interface consists in three concentric capillaries, allowing for BGE, sheath liquid (SL) and NG mixing, it is demonstrated herein that other parameters are also involved in this suction effect: the CE capillary protrusion from the interface needle, SL flow rate, and overall BGE flow rate and velocity profile. Whereas NG flow rate is the parameter affecting suction to a greater extent, separation capillary protruding length, SL, and overall BGE flow rate have a significant additional impact on this phenomenon. It is shown that SL flow rate can affect suction differently according to the NG velocity, which may be explained by modification of the Taylor cone geometry. Furthermore, it appears that suction effect is noticeably favored by a parabolic velocity profile of the BGE, again probably due to the Taylor cone shape modification. Finally, the temperature gradient created by the contact between the heated NG and the separation capillary enhances this effect.

Design and evaluation of a continuous flow, integrated nebulizer-hydride generator for flame atomic absorption spectrometry

An evaluation of the performance of a continuous flow hydride generator-nebulizer for flame atomic absorption spectrometry was carried out. Optimization of nebulizer gas flow rate, sample acid concentration, sample and tetrahydroborate uptake rates and reductant concentration, on the As and Se absorbance signals was carried out. A hydrogen-argon flame was used. An improvement of the analytical sensitivity relative to the conventional bead nebulizer used in flame AA was obtained (2 (As) and 4.8 (Se) µg L-1). Detection limits (3σb) of 1 (As) and 1.3 (Se) µg L-1 were obtained. Accuracy of the method was checked by analyzing an oyster tissue reference material.

Optimization and Application of ICPMS with Dynamic Reaction Cell for Precise Determination of 44Ca/40Ca Isotope Ratios

An inductively coupled plasma mass spectrometer with dynamic reaction cell (ICP-DRC-MS) was optimized for determining (44)Ca/(40)Ca isotope ratios in aqueous solutions with respect to (i) repeatability, (ii) robustness, and (iii) stability. Ammonia as reaction gas allowed both the removal of (40)Ar+ interference on (40)Ca+ and collisional damping of ion density fluctuations of an ion beam extracted from an ICP. The effect of laboratory conditions as well as ICP-DRC-MS parameters such a nebulizer gas flow rate, rf power, lens potential, dwell time, or DRC parameters on precision and mass bias was studied. Precision (calculated using the "unbiased" or "n - 1" method) of a single isotope ratio measurement of a 60 ng g(-1) calcium solution (analysis time of 6 min) is routinely achievable in the range of 0.03-0.05%, which corresponded to the standard error of the mean value (n = 6) of 0.012-0.020%. These experimentally observed RSDs were close to theoretical precision values given by counting statistics. Accuracy of measured isotope ratios was assessed by comparative measurements of the same samples by ICP-DRC-MS and thermal ionization mass spectrometry (TIMS) by using isotope dilution with a (43)Ca-(48)Ca double spike. The analysis time in both cases was 1 h per analysis (10 blocks, each 6 min). The delta(44)Ca values measured by TIMS and ICP-DRC-MS with double-spike calibration in two samples (Ca ICP standard solution and digested NIST 1486 bone meal) coincided within the obtained precision. Although the applied isotope dilution with (43)Ca-(48)Ca double-spike compensates for time-dependent deviations of mass bias and allows achieving accurate results, this approach makes it necessary to measure an additional isotope pair, reducing the overall analysis time per isotope or increasing the total analysis time. Further development of external calibration by using a bracketing method would allow a wider use of ICP-DRC-MS for routine calcium isotopic measurements, but it still requires particular software or hardware improvements aimed at reliable control of environmental effects, which might influence signal stability in ICP-DRC-MS and serve as potential uncertainty sources in isotope ratio measurements.

Determination of seventeen main flavonoids and saponins in the medicinal plant Huang‐qi (Radix Astragali) by HPLC‐DAD‐ELSD

A simple, rapid, and reliable method, namely high-performance liquid chromatography coupled with diode array and evaporative light scattering detectors (HPLC-DAD-ELSD), was developed to simultaneously determine twelve major flavonoids and five main saponins in different parts of the medicinal plant Huang-qi (Radix Astragali). The DAD wavelength was set at 280 nm for the UV detection of flavonoids, while the drift tube temperature was set at 105 degrees C and the nebulizing gas flow rate at 2.7 L/min for ELSD detection of saponins. The method was fully validated with respect to linearity (r2 >0.998), sensitivity, precision, and accuracy (recovery rate between 93.3 and 104.2%). The analytical results of different parts of the medicinal plant Huang-qi revealed that the levels of total flavonoids or saponins in individual parts can vary considerably and the concentration of each compound in different parts is also significantly different. The aerial parts (stems and leaves) contain even higher total contents of flavonoids (although of different kinds) than the commonly used roots of the plants. In addition, the concentration of total flavonoids and saponins in the extract of the fibrous roots was surprisingly highest among all parts of Astragalus species. All of these findings provide clear evidence and scientific support for utilization of different parts of the medicinal plant Huang-qi and also for reduction in waste of plant resources.

Improvement of Metals and Phosphorus Analysis in Water Samples by Inductively Coupled Plasma Optical Emission Spectroscopy, Radio Frequency Power, and Nebulizer Gas Flow Rate Modification

Inductively coupled plasma optical emission spectrometry (ICP‐OES) is a powerful tool for simultaneous multielement analysis. The objective of this study was to determine optimum ICP‐OES operational parameters for aluminum (Al), copper (Cu), iron (Fe), manganese (Mn), sodium (Na), phosphorus (P), and zinc (Zn) in natural water samples. Five radio‐frequency forward powers (RF powers) and four nebulizer gas flow rates were tested. Different RF power values and nebulizer gas flow rates were found to be ideal for each element. Performance was best for Al, Na, and P at 1400 W RF power, whereas the optimal nebulizer gas flow rate for Na, Fe, Zn, and Al was 1 L min−1. The differences in RF power and nebulizer gas flow rates were found to be driven by changes in 1) element emission lines for different RF powers and 2) evaporation rates, mean diameter drop sizes, solvent loading, and analyte signal intensities for different nebulizer gas flow rates and analyte concentrations. Grouping the elements with similar parameters will avoid reading delays.

Dilute-and-shoot procedure for the determination of mineral constituents in vinegar samples by axially viewed inductively coupled plasma optical emission spectrometry (ICP OES)

Samples of commercial wine vinegar were introduced in an axially viewed inductively coupled plasma optical emission spectrometry instrument (AX-ICP OES) equipped with different sample introduction systems: a cross-flow nebulizer combined with a double-path spray chamber (CF-DP) and cone spray associated with a cyclone spray chamber (CS-CC). Samples of white and red wine vinegar were diluted with water before analysis. Higher magnesium Mg II/Mg I ratios (11 and 10 for CS-CC and CF-DP, respectively) were obtained using a nebulization gas flow rate of 0.6 l min−1 and an applied power of 1.3 kW. The background equivalent concentrations (BEC) and signal-to-background ratio (SBR) of analytes were improved using scandium (Sc) as the internal standard. The limits of detection (LOD) and limits of quantification (LOQ) for mineral constituents were similar for both introduction systems. Best recoveries values were obtained using a plasma under robust conditions, CS-CC system and Sc as the internal standard. The concentration determined in 13 commercial samples of wine vinegars varied between 0.2 and 3.0, between 0.02 and 0.4, between 8.5 and 100.0, between 0.01 and 0.05, between 27.0 and 540.0, between 4.0 and 79.0, between 0.4 and 10.0, and between 0.01 and 2.0 for aluminium (Al), barium (Ba), calcium (Ca), copper (Cu), potassium (K), magnesium (Mg), manganese (Mn), and zinc (Zn), respectively.

Study of the absence of recondensation with low liquid delivery rates by using a cavity sheathing gas in inductively coupled plasma-atomic emission spectrometry

In order to elucidate the absence of recondensation when using very low liquid delivery rates, the effect of flow rate of a sheathing gas injected in a single-pass spray chamber placed before the torch (i.e., cavity chamber) of an inductively coupled plasma atomic emission spectrometer (ICP-AES) on analytical performance and aerosol characteristics using analytical figures of merit was studied. Five different cavities of the so-called torch integrated sample introduction system (TISIS) were evaluated. Furthermore, two nebulizers were used: a PFA micronebulizer and a high efficiency nebulizer (HEN). A low inner volume cyclonic spray chamber (Cinnabar) was taken as the reference system. The studies were performed in terms of sensitivities, limits of detection and extent of the matrix effects and the elements evaluated were Al, As, Ba, Bi, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Sb, Se, Sr, V and Zn. The results indicated that the sheathing gas effect was dependent on the cavity inner volume as well as on the delivery liquid flow rate. For low liquid flow rates (i.e., 28 and 40 μl min−1) and long cavities, the increase in the sheathing gas flow rate caused an initial increase in the ICP-AES sensitivity and, then, a decrease. At higher liquid flow rates (i.e., 80 and 120 μl min−1) and for short spray chambers, an increase in the sheathing gas flow rate led to a decrease in the signal. These trends were explained in terms of the increased primary aerosol mean size (with Sauter mean diameters going from 8.2 to 17.0 μm as the nebulizer gas flow rate decreased from 0.8 to 0.2 l min−1) and reduced droplet inertial losses. The data obtained for the two nebulizers demonstrated that for the HEN, the effect of the sheathing gas was less significant than for the PFA. The TISIS cavities compared favourably with respect to the Cinnabar in terms of sensitivities. Long cavities gave rise to sensitivities up to 2.5 times higher than the Cinnabar. Matrix effects caused by inorganic (nitric acid) as well as organic (ethanol) concomitants were less pronounced for long than for short cavities for all the elements tested. The sheathing gas flow rate did not have a marked effect on the extent of the interferences.