Hydraulic High-pressure Nebulization Research Articles

Coupling of microwave induced plasma optical emission spectrometry with HPLC separation for speciation analysis of Cr(III)/Cr(VI)

AbstractFeasibility and limitations of direct coupling of high performance liquid chromatographic (HPLC) separation to microwave induced plasma (MIP)-optical emission spectrometry (OES) for elementspecific detection was tested and compared to inductively coupled plasma (ICP)-optical emission spectrometric detection on the basis of the Cr(III)/Cr(VI) speciation analysis of water samples. Coupling was performed by a hydraulic high pressure nebulizer (HHPN) radiative-heating/watercooling interface which provides about 20 % and 80 % aerosol yield in the case of helium and argon carrier gases, respectively. Desolvation efficiency of aqueous solutions was approximately 80 %. Applying the ion-pair HPLC separation, the organic eluents and reagents in the MIP cause a 50–75 % signal suppression for Cr(VI) and 25–50 % for Cr(III). In a pure aqueous solution the MIP Cr(VI) signal was by 20 % lower than that of Cr(III). These effects were lower using the ICP source, but they cannot be neglected. Easily ionizable matrix elements (Na, Ca) can cause 70 % signal suppression in the MIP, and 20 % in the ICP. Therefore, species dependent calibration is required in both cases. In the case of HPLC detection by MIP-OES, the detection limit was 13 ng for Cr(III), and 18 ng for Cr(VI). Using the ICP-OES detection, the detection limit was 0.2 ng for Cr (III) and 0.4 ng for Cr (VI). The linear dynamic ranges in both cases were two orders of magnitude.

Atomic distributions in acetylene-air flame using hydraulic high-pressure nebulization with direct (100%) introduction of solutions Applications to speciation analysis

One of the fundamental factors of the performance of atomic spectrometric methods is the efficiency of sample introduction into flame or plasma. By utilization of the formerly developed hydraulic high-pressure nebulizer, a nebulizer/burner system with solution uptake efficiency of 100% have been worked out. Optimizing operation parameters of nebulizer/burner system, an improvement of 2–12 times was achieved for the signal-to-noise ratio in the flame emission and flame atomic absorption spectrometry, depending on sample flow rate. This nebulizer is especially suitable for development of liquid chromatography-AAS/FES coupled technique for speciation analytical tasks.

Characterisation of a hydraulic high-pressure sample introduction assisted flow injection—inductively coupled plasma time-of-flight mass spectrometry system and its application to the analysis of biological samples

A flow injection (FI) method was developed using hydraulic high-pressure nebulization as a sample introduction system, coupled to inductively coupled plasma time-of-flight mass spectrometer (ICP-TOFMS) for rapid and simultaneous determination of 19 elements. The operating conditions of the system (analyte flow rate, heating and cooling temperatures of the desolvation module, carrier gas flow rate) for the simultaneous determination of 19 analytes were optimised. The optimum parameters of the sample introduction system were found to be 1.4mlmin−1 and 1.35lmin−1 for the analyte solution and nebulizer flow rates, respectively. A compromised condition for heating and cooling stage temperatures of 170 and −5°C was chosen. The detection limits were compared to those obtained by using ICP-TOFMS with alternative sample introduction techniques e.g. conventional nebulization, flow injection chemical hydride generation (FI-CHG) and the obtained results were comparable or better than those resulting from alternative sample introduction. Applying the optimised conditions the simultaneous determination of Ag, As, Ba, Cd, Co, Cu, Ga, In, Li, Mn, Mo, Pb, Sb, Se, Sn, Sr, Tl, V and Zn was carried out. Absolute detection limits (3σ) in the range of 2–750pg and precision between 0.5 and 9.6% from five replicate measurements of 10ngml−1 multielemental sample solutions were achieved by using a 200μl sample loop. The developed method was applied for the analysis of certified reference materials of biological origin (TORT-2 “Lobster Hepatopancrease”, BCR-422 “Cod Muscle” and IAEA MA-B-3/TM “Fish Homogenate”), and the results showed good agreement with the certified values.

Investigations on the on-line determination of metals in air flows by capacitively coupled microwave plasma atomic emission spectrometry

Plasma optical emission spectrometry with a capacitively coupled microwave plasma (CMP) operated with air has been investigated with respect to its possibilities for real-time environmental monitoring of combustion processes. The unique feature is the possibility to operate the CMP with air as working gas, as is usually the case in exhaust gases of combustion processes. The CMP also is shown to be stable in the presence of large amounts of water and CO 2, which makes this source ideally suitable for this purpose. The detection limits obtained for the environmentally relevant elements Cd, Co, Cr, Fe, Mg, Ni and Pb show the possibility to monitor directly heavy metals in air in an on-line mode and down to the 2–160-μg m −3 level. These detection limits are generally lower than the threshold limit values of the ‘Federal Law for Immission Protection’ in Germany in the gaseous effluents of industrial plants. In order to investigate the influence of the water loading (32–222 g m −3) on the detection limits a comparison of results obtained with three different nebulizers (Légère nebulizer, hydraulic high-pressure nebulizer and ultrasonic nebulizer) was made, with which aerosols with different water loading are entered into the plasma. For the hydraulic high-pressure nebulizer and the ultrasonic nebulizer no desolvation unit was found to be necessary. It was shown that especially for elements with lines having high excitation energy (Cd) or for which ion lines are used (Mg II) the increase in water loading deteriorates the detection limits. The rotational temperatures ( T rot) and excitation temperatures ( T exe) in the case of different amounts of water are of the order of 3700–4900 K and 4700–7100 K, respectively. The temperatures show that changes in the geometry and temperature distribution in the case of T rot but also the values of T exe themselves are responsible for this increase in detection limits. Furthermore, different amounts of CO 2 mixed to the working gas (3–22%) while the total gas flow rate was kept constant at 1.2 l min −1 were also shown to increase the detection limits.

Combinación de sistemas de flujo de baja y alta presion para la determinacion de Mg, Ca y Sr en salmueras por espectrofotometria de absorcion atomica con llama

This article describes the combination of low- and high-pressure flow systems for the determination of Magnesium, Calcium and Strontium by flame atomic absorption spectrometry (FAAS). In the low-pressure system a short C-18 RP column (length 0,5 cm) was utilized for the preconcentration/matrix separation step, xylenol orange was used as chelating agent and tetrabutylamonium acetate for ion pair formation. The hydraulic high pressure nebulization (HHPN) was used for sample transport and sample introduction in the high pressure system. The repeatabilities and detection limits for Mg, Ca and Sr were determined and compared with those obtained by pneumatic nebulization (PN). The results show that the detection limits obtained using the HHPN for Mg, Ca and Sr are between 1.5 to 2 times better than those obtained by PN when the signal transient was measured in area. The system presented a sampling frequency of 130 h-1 for direct determination of Mg, Ca or Sr in samples of saturated sodium chloride used in the production of chlorine and sodium hydroxide.

Hydraulic High-Pressure Nebulization of Solutions and Dispersions for Respiratory Drug Delivery*

The purpose of this investigation was to assess hydraulic high-pressure nebulization as a means for respiratory drug delivery. A hydraulic high-pressure nebulizer was designed and constructed. In a design study, the output efficiency and the aerosol particle size were determined for the nebulizer as a function of nozzle diameter (5, 10, and 20 μm), gas flow rate (2 and 8 l/min), applied hydraulic pressure (2200 and 4000 psig), and distance between the nozzle orifice and impaction surface (0.25–4 cm) with an aqueous solution of fluorescein. The output efficiency was also measured with an ethanol solution and an aqueous phospholipid dispersion of liposomes. For the design study, each factor had an effect. The efficiency tended to increase with a decrease in the nozzle diameter, although the differences between the 5- and 10-μm nozzle were more sensitive to the air flow rate and nozzle-to-impaction-surface distance. Greater efficiencies were always obtained at the higher ancillary air flow rates. Operating the nebulizer at different pressures caused a change in the functional relationship between the efficiency and the nozzle-to-impaction-surface distance. For the 5-μm nozzle at high pressure, efficiency fell with increasing nozzle-to-impaction-surface distance, whereas for the data obtained with the 20-μm nozzle, the efficiency increased with nozzle-to-impaction-surface distance, with lower efficiencies obtained at the higher pressures. For the remaining observations made with the 5- and 10-μm nozzles, the efficiency as a function of nozzle-to-impaction-surface distance appeared to be variable. For the 5- and 10-μm size nozzle, there was no significant effect of the air flow rate, pressure, or nozzle-to-impaction-surface distance on the mass median aerodynamic diameter and geometric standard deviation. For the 20-μm size nozzle, the particles were not completely dried. Ethanol solutions gave somewhat higher efficiencies, whereas the phospholipid dispersion gave efficiencies comparable to the aqueous solutions nebulized under similar conditions. The efficiency of the hydraulic high-pressure nebulizer appears to be correlated with the calculated properties of the liquid jet. For respiratory drug delivery, the hydraulic high-pressure nebulizer provides reasonably high outputs of respirable particles independent of time from a single pass of liquid through the nebulizer.

Possibilities for the simultaneous preconcentration and flame atomic absorption spectrometric determination of Cr(III) and Cr(VI) using a C18 column and sorption loop

The sorption loop as a preconcentration unit used so far in the low-pressure flow injection (FI) system was combined with the hydraulic high-pressure nebulizer (HHPN) and a high-pressure liquid chromatographic (HPLC) column. Thus, the sorption preconcentration of Cr(VI) can be coupled to a powerful sample introduction method or preconcentration techniques of Cr(III). The subsequent determination of the Cr(VI) content of the samples was carried out by flame atomic absorption (FAAS).

Application of MIP-AES as element specific detector for speciation analysis

An MIP-AES element specific detector has been directly coupled to an HPLC separation system by means of hydraulic high-pressure nebulization (HHPN) with an appropriate desolvation unit. This system was applied to Cr(III)/Cr(VI) speciation analysis. The linear dynamic range of Cr(III) and Cr(VI) determination was two orders of magnitude, absolute detection limits were 13 ng for Cr(III) and 18 ng for Cr (VI), respectively. The matrix effect caused by the easily ionizable elements (Na, Ca, K) was significant in real samples.

Determination of arsenic compounds in marine mammals with high-performance liquid chromatography and an inductively coupled plasma mass spectrometer as element-specific detector

Total arsenic concentrations and the concentrations of individual arsenic compounds were determined in liver samples of pinnipeds [nine ringed seals (Phoca hispida), one bearded seal (Erginathus barbatus)] and cetaceans [two pilot whales (Globicephalus melas), one beluga whale (Deliphinapterus leucus)]. Total arsenic concentrations ranged from 0.167 to 2.40 mg As kg -1 wet mass. The arsenic compounds extracted from the liver samples with a methanol/water mixture (9:1, v/v) were identified and quantified by anion- and cation-exchange chromatography. An ICP-MS equipped with a hydraulic highpressure nebulizer served as the arsenic-specific detector. Arsenobetaine (0.052-1.67 mg As kg -1 wet mass) was the predominant arsenic compound in all the liver samples. Arsenocholine was present in all livers (0.005-0.044 mg As kg -1 wet mass). The tetramethylarsonium cation was detected in all pinnipeds (<0.009 to 0.043 mg Askg -1 ) but not in any of the cetaceans. The concentration of dimethylarsinic acid ranged from < 0.001 to 0.109mgAskg -1 wet mass. Most of the concentrations for methylarsonic acid (<0.001 to 0.025 mg As kg -1 wet mass) were below the detection limit. Arsenous acid and arsenic acid concentrations were below the detection limit of the method (0.001 mg As kg -1 ). An unknown arsenic compound was present in all liver samples at concentrations from 0.002-0.027 mg As kg -1 .

Retention Behavior of Inorganic and Organic Selenium Compounds on a Polymer-Based Cation Exchange Column

The retention behavior of selenous acid, selenic acid, selenomethionine, selenoethionine, selenocystine, selenohomocystine, trimethyl-selenonium iodide, and (3-amino-3-carboxy-1-propyl)-dimethylselenonium iodide was studied on the polymer-based PRP-X200 cation exchange column with an aqueous solution of pyridine (20 to 100 mM) in the pH range 1.1-6.0 adjusted with formic acid as the mobile phase. An inductively coupled plasma mass spectrometer equipped with a hydraulic high pressure nebulizer served as selenium specific detector. The retention behavior was rationalized in terms of the pH-dependent deprotonation of the selenium compounds and of the pyridinium cation and of the formation of ion-pairs between hydrogen selenite, selenate, or the zwitterionic groups of the selenoamino acids with the pyridinium cation. A good separation of seven selenium compounds was achieved within 5.0 min at 40°C with 20 mM pyridine (pH 3.70). Selenoethionine eluted 15 min after injection. Peak areas and peak heights of the chromatographic signals provided linear calibration curves (r2 > 0.990). Detection limits obtained were 1 μg/L with the exception of selenoethionine (5 μg/L).

Cr(III)/Cr(VI) determination in waste water by ICP/AES with on-line HPLC (HHPN) sample introduction

Using hydraulic high-pressure nebulization (HHPN) for sample introduction, an on-line high-pressure flow system (HPLC system) becomes a functional component of the ICP spectrometer. By placing additionally an HPLC column between the sample valve and the high-pressure injection/nebulization nozzle, an improved species analysis is attained. An example is given by on-line separation and determination of Cr(III)/Cr(VI) in real waste water samples with ICP/AES. The detection limit of each Cr oxidation state is 4 μg L–1 with an analysis cycle time of 5 min. In comparison to conventional coupling of HPLC and ICP spectrometry a considerably higher sensitivity is achieved. Using spiked samples the recovery of HHPN-ICP/AES was on an average better than 98% in contrast to only 79% for Cr(VI) determination with a UV photometric reference method. Due to chromatographic separation of Cr(VI) from matrix components and Cr (III), the technique no longer shows the typical spectral interferences caused by Ca (267.716 nm Cr line) and Fe (283.563 nm Cr line).

Flame Atomic Absorption Spectrometric Determination of Total Chromium and Cr(VI) in Cigarette Ash and Smoke using Flow Injection/Hydraulic High-Pressure Sample Introduction

Abstract Total chromium and Cr(VI) contents of cigarettes, ash, and smoke formed while burning cigarettes were determined. The determinations of chromium species were carried out according to procedures developed earlier. Cr(VI) was determined in a combined system, which involves a flow injection (FI) sorption preconcentration system, hydraulic high-pressure nebulization (HHPN) sample introduction technique, and flame atomic absorption spectrometric (FAAS) detection. The total chromium of samples in Cr(VI) form was determined in this same combined system after ashing cigarettes at 800°C [after total conversion of Cr(III) of the sample to Cr(VI)]. It was found that while burning cigarettes 0.8–1.2% of the original chromium content of the cigarettes comes to smoke in the toxic Cr(VI) form.

On-Line Multielement Preconcentration and Inductively Coupled Plasma Atomic Emission Spectrometric Determination of Transition Metals Using a Flow Injection Hydraulic High-Pressure Nebulization–Desolvation Sample Introduction System

A method was developed for simultaneous preconcentration and on-line determination of 15 transition metals (Ag, Au, Cd, Cr, Cu, Fe, In, Ni, Pb, Pd, Pt, Ti, Tl, V, Zn). A polyether–ether–ketone (PEEK) loop as preconcentration unit introduced by us earlier was used for the multielement flow injection (FI) preconcentration of transition metal–pyrrolidinedithiocarbamate complexes. The preconcentrated complexes were eluted with isobutylmethyl ketone and introduced into the inductively coupled plasma with a hydraulic high-pressure nebulizer (HHPN) and desolvation unit. The desolvation system, the use of which was necessary for aerosol of isobutylmethyl ketone eluant, was optimized. The enrichment factors of the 15 transition metals were 14–67 due to 2 min of preconcentration time.

Speciation of organic selenium compounds by reversed-phase liquid chromatography and inductively coupled plasma mass spectrometry. Part I. Sector field instrument with low mass resolution

The speciation of selenocystine, selenocystamine, selenomethionine and selenoethionine was studied by on-line coupling of high performance liquid chromatography with inductively coupled plasma mass spectrometry with hydraulic high pressure nebulization (HHPN) for sample introduction employing a double-focusing magnetic sector field mass spectrometer in order to achieve the utmost sensitivity. Reversed-phase chromatography was applied to separate the organic Se compounds. The eluent was 30 mm ammonium buffer adjusted to pH 3.0 in methanol-water (5+95 v/v). The operating conditions for chromatographic separation (pH of the mobile phase, methanol content of the mobile phase, pH of the sample and sample uptake rate) were carefully optimized. With the developed procedure, detection limits below 0.02 ng ml –1 were achieved, so that even low pg levels could be detected when applying sample volume of 200 μl.

Urinary arsenic species in Devon and Cornwall residents, UK. A pilot study.

First void urine samples were collected from 24 residents in an area of past intense mining and smelting activity of arsenical ores. Seven samples were also taken from a control village. The arsenic species in the urine were separated and quantified with an HPLC-ICP-MS system equipped with a hydraulic high-pressure nebulizer. The detection limit for arsenic in urine using this system is 0.05 microgram dm-3. Creatinine was also determined for all samples to remove the influence of urine density and all results were expressed in microgram As g-1 creatinine. The results showed elevated levels of both organic and inorganic arsenic compounds in the 'exposed' population's urine when compared with those of the control group. The total As concentrations (less arsenobetaine) in the 'exposed' population were in the range 2.7-58.9 micrograms g-1 creatinine (mean 13.4, median 9.2 micrograms g-1) compared with the control group data range 2.5-5.3 micrograms g-1 (mean 4.2, median 4.7 micrograms g-1).

Retention Behavior of Inorganic and Organic Selenium Compounds on a Polymer-Based Cation Exchange Column

The retention behavior of selenous acid, selenic acid, selenomethionine, selenoethionine, selenocystine, selenohomocystine, trimethyl-selenonium iodide, and (3-amino-3-carboxy-1-propyl)-dimethylselenonium iodide was studied on the polymer-based PRP-X200 cation exchange column with an aqueous solution of pyridine (20 to 100 mM) in the pH range 1.1-6.0 adjusted with formic acid as the mobile phase. An inductively coupled plasma mass spectrometer equipped with a hydraulic high pressure nebulizer served as selenium specific detector. The retention behavior was rationalized in terms of the pH-dependent deprotonation of the selenium compounds and of the pyridinium cation and of the formation of ion-pairs between hydrogen selenite, selenate, or the zwitterionic groups of the selenoamino acids with the pyridinium cation. A good separation of seven selenium compounds was achieved within 5.0 min at 40°C with 20 mM pyridine (pH 3.70). Selenoethionine eluted 15 min after injection. Peak areas and peak heights of the chromatographic signals provided linear calibration curves (r2 > 0.990). Detection limits obtained were 1 μg/L with the exception of selenoethionine (5 μg/L).

Retention behavior of inorganic and organic selenium compounds on a silica-based strong-cation-exchange column with an inductively coupled plasma mass spectrometer as selenium-specific detector

The retention behavior of eight selenium compounds (selenous acid, selenic acid, selenocystine, selenohomocystine, selenomethionine, selenoethionine, trimethylselenonium iodide, and dimethyl(3-amino-3-carboxy-1-propyl)selenonium iodide) with aqueous solutions of pyridine (20 mmol/l) in the pH range 2.0–5.7 on a Supelcosil LC-SCX cation-exchange column was investigated. An inductively coupled plasma mass spectrometer was employed as the selenium-specific detector. To increase the nebulization efficiency, the Meinhard concentric glass nebulizer was replaced by a hydraulic high-pressure nebulizer. At pH 5.0, seven selenium compounds could be separated within 400 s, but selenohomocystine and selenomethionine had the same retention time. Selenomethionine can be separated from selenohomocystine with an aqueous solution of pyridine (20 mmol/l) adjusted with formic acid to pH 2.0. At 1 ng Se ml −1, the relative standard deviations ( n=5) of the signal area for the eight selenium compounds ranged from 7 to 11%, and at 50 ng Se ml −1 from 0.6 to 2.6%.

Arsenic compounds in a marine food chain

A three-organism food chain within a rock pool at Rosedale, NSW, Australia, was investigated with respect to arsenic compounds by high performance liquid chromatography – hydraulic high pressure nebulization – inductively coupled plasma mass spectrometry (HPLC-HHPN-ICP-MS). Total arsenic concentration was determined in the seaweed Hormosira banksii (27.2 μg/g dry mass), in the gastropod Austrocochlea constricta (74.4 μg/g dry mass), which consumes the seaweed, and in the gastropod Morula marginalba (233 μg/g dry mass), which eats Austrocochlea constricta. The major arsenic compounds in the seaweed were (2′R)-dimethyl[1-O-(2′,3′-dihydroxypropyl)-5-deoxy-β-d-ribofuranos-5-yl]arsine oxide and an unidentified compound. The herbivorous gastropod Austrocochlea constricta transformed most of the arsenic taken up with the seaweed to arsenobetaine. Traces of arsenite, arsenate, dimethylarsinic acid, arsenocholine, the tetramethylarsonium cation, and several unknown arsenic compounds were detected. Arsenobetaine accounted for 95% of the arsenic in the carnivorous gastropod Morula marginalba. In Morula marginalba the concentration of arsenocholine was higher, and the concentrations of the minor arsenic compounds lower than in the herbivorous gastropod Austrocochlea constricta.

New strategies for trace analyses of ZrO 2 , SiC and Al 2 O 3 ceramic powders

The progress possible in the analysis of refractory powders such as ZrO2, SiC and Al2O3 by the use of new sample preparation, processing and introduction techniques elaborated for AAS, ICP-OES and ICP-MS with low and high mass resolution is demonstrated. For optimized sample preparation techniques based on dissolution of ZrO2, e.g. fusion with (NH4)2SO4, it is shown to what extent impurities present in (NH4)2SO4 determine the detection limit. Hydraulic high pressure nebulization with and without matrix removal by complexing the impurities with dithiocarbamates (Cu, Co, Cr and Ni) or oxine (Fe, Mn and Mo) and fixing them on a C18 solid phase for subsequent solid phase extraction coupled with flame atomic absorption was used to determine Fe, Cu, Cr, Mn, Ni, Co and Mo impurities in (NH4)2SO4 in the 10–100 ng/g range. Further a method to synthesize (NH4)2SO4 with higher purity than some commercially available high-purity (NH4)2SO4 with respect to Fe, Cu, Cr and Mn using high-purity NH3 and chlorosulphonic acid is shown. Reliable determinations of Fe and Al at the 100 μg/g level in ZrO2 with ICP-OES with matrix removal as well as with ICP-MS without matrix removal are reported. For the direct analysis of Al2O3 powders, slurry nebulization ICP-MS sample introduction is shown to improve detection limits and to reduce sample preparation, if the leachable and non-leachable fractions are analyzed separately. For powders such as SiC, the matrix or solvents can cause spectral interferences. Matrix removal is shown to be useful to improve detection limits for the interfered elements. High resolution ICP-MS can be used to control the completeness of matrix removal techniques and to overcome limitations due to spectral interferences even in case of complex materials.

Arsenic compounds in terrestrial organisms. III: Arsenic compounds inFormica from an old arsenic smelter site

Total arsenic concentrations in the freeze-dried pulverized ants (Formica sp.) and material from an ant-hill collected at a former arsenic roasting facility were determined by inductively coupled plasma mass spectrometry (ICP-MS) after microwave digestion with nitric acid and hydrogen peroxide. The ants contained 12.6 ± 0.9 mg As/kg dry mass, the ant-hill material 5420 ± 90 mg As/kg dry mass. Total arsenic concentrations in needles of Picea abies and Larix decidua (spruce and larch needles) were also determined, because needles are the main constituents of the upper layer of ant-hill material. Needles of Picea abies contained 1.17 mg As/kg dry mass and needles of Larix decidua 3.71 mg As/kg. The Formica sp. and ant-hill material were extracted with water or methanol/water (9:1). The extracts were chromatographed on a cation-exchange and an anion-exchange column. Water extracted 20% of the arsenic from the ants and only 3% from the ant-hill material. With methanol/water (9:1) only 7% of the arsenic was released by the ants and 0.5% by the ant-hill material. The arsenic compounds in the column effluents that were introduced into the plasma via a hydraulic high-pressure nebulizer (HHPN) were quantified on-line by ICP-MS. Arsenite and arsenate were the major arsenic compounds in the extract. Dimethylarsinic acid and traces of methylarsonic acid and arsenobetaine were also detected. The extracts of the ant-hill material contained the same compounds. Additionally, traces of trimethylarsine oxide were found. The presence of arsenobetaine was confirmed by spiking an extract of the ants with synthetic arsenobetaine bromide.