The application of chemical modification in electrothermal vaporization-inductively coupled plasma atomic emission spectrometry

In this paper, several fluoride chemical modifiers have been tested for electrothermal vaporization-inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) determination of different volatile elements, such as refractory element Ti, medium volatile element Ni and easy volatile element Pb. Reagents tested include polytetrafluoroethylene (PTFE), NH(4)F, NaF and CuF(2).2H(2)O. The best overall results are obtained using 6% PTFE added to sample. Under the compromise operating conditions, the detection limits of analytes are in the range of 0.8-59 ng ml(-1) and the calibration curves are linear for over three orders of magnitude. The direct determination of Ti, Ni and Pb in GBW 08505 tea leaves reference sample is shown as an example of PTFE chemical modification.     

Determination of phosphorus and arsenic in trichlorosilane by electrothermal vaporization-inductively coupled plasma mass spectrometry with prior concentration by cuprous chloride

A method for the determination of trace impurities of phosphorus and arsenic in trichlorosilane with prior separation followed by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) has been developed. The preconcentration of the analytes from the sample matrix was made by adding cuprous chloride to a 10 mL trichlorosilane sample for the formation of non-volatile compounds with the elements of interest. Upon evaporation of trichlorosilane, the analytes retained in the residue were then determined in the presence of copper as modifier by ETV-ICP-MS. The dual role of cuprous chloride both in the preconcentration and instrumental determination was investigated and discussed. By meticulous control of experimental conditions, limits of detection for these two elements as low as sub-ng/g can be achieved. The method was applied to the determination of phosphorus and arsenic in a commercially available trichlorosilane sample.     

Determination of phosphorus and arsenic in trichlorosilane by electrothermal vaporization-inductively coupled plasma mass spectrometry with prior concentration by cuprous chloride

A method for the determination of trace impurities of phosphorus and arsenic in trichlorosilane with prior separation followed by electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) has been developed. The preconcentration of the analytes from the sample matrix was made by adding cuprous chloride to a 10 mL trichlorosilane sample for the formation of non-volatile compounds with the elements of interest. Upon evaporation of trichlorosilane, the analytes retained in the residue were then determined in the presence of copper as modifier by ETV-ICP-MS. The dual role of cuprous chloride both in the preconcentration and instrumental determination was investigated and discussed. By meticulous control of experimental conditions, limits of detection for these two elements as low as sub-ng/g can be achieved. The method was applied to the determination of phosphorus and arsenic in a commercially available trichlorosilane sample.     

癌胚抗原毛细管电泳-化学发光均相免疫分析

设计了一种测定人血清中癌胚抗原的毛细管电泳-化学发光检测均相免疫分析新方法。采用四苯硼酸钠增强luminol-H2O2-HRP体系化学发光的原理,化学发光检测经毛细管电泳分离的,用辣根过氧化物酶(HRP)标记的癌胚抗体及免疫复合物。测定癌胚抗原的线性范围2.0~80.0μg/L(R=0.9921),检出限为0.1μg/L(绝对检出限为0.75 fg)。     

癌胚抗原毛细管电泳-化学发光均相免疫分析

建立了一种测定人血清中癌胚抗原的毛细管电泳-化学发光检测的均相免疫分析新方法.采用四苯硼钠增强luminol-H2 O2-HRP体系化学发光的原理,化学发光检测经毛细管电泳分离的,用辣根过氧化物酶(HRP)标记的癌胚抗体及免疫复合物.测定癌胚抗原的线性范围2.0～80.0 μg/L(R=0.9921),检出限为0.1 μg/L(绝对检出限为0.75 fg).     

Element-tagged immunoassay with inductively coupled plasma mass spectrometry for multianalyte detection

The multianalyte immunoassay approach is currently attracting increasing attention due to its high sample throughput, short assay time, low sample consumption and reduced overall cost per assay. This paper reviews progress in the field of multianalyte immunoassays using inductively coupled plasma mass spectrometry, as well as applications of this approach in different fields. Examples related to the combination of protein microarray technology with the multitag approach of the immunoassay ICP-MS method and to the use of ICP-MS in the field of imaging are described. A novel strategy that involves tagging antibodies for ICP-MS detection in sensitive multitag bioassays is also presented. Finally, the outlook for this promising technique is discussed.     

Signal enhancement effect of halogen matrix in electrothermal vaporization-inductively coupled plasma-mass spectrometry

In tungsten furnace electrothermal vaporization(ETV)-inductively coupled plasma mass spectrometry(ICP-MS), the presence of halogen matrices caused a signal enhancement for volatile elements such as Zn, Cd and Pb, whose halides melting and boiling points were relatively low. In order to clarify the mechanism of signal enhancement in ETV-ICP-MS, the effects of chemical interaction between analytes and halogen matrices on the surface of ETV furnace, the transport efficiency of vaporized analytes from the furnace into the ICP and the physical properties of the ICP itself and of the micro plasma (interface plasma) in the interface region between the sampling and the skimmer cones were investigated by atomic absorption and atomic emission spectrometry. Among the effects mentioned above, neither the chemical interaction on the surface of the ETV furnace nor the transport efficiency of vaporized analytes could be related to the analyte signal enhancements. The degree of enhancement was found to depend on the ionization potential of the coexisting halogen and was not caused by a variation in the physical properties of the ICP but rather by a variation of those of the interface plasma. These results suggest that the halogen matrices may affect the physical properties of the interface plasma, contributing to the promotion of the ionization of analytes.     

Analyte transport efficiency with electrothermal vaporization inductively coupled plasma mass spectrometry

Reported are results for the quantitative determination of absolute transport efficiency in electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) for the Perkin-Elmer HGA-600MS electrothermal vaporizer. The absolute transport efficiencies for Mo, In, Tl and Bi were determined using experimental conditions typical of those applied to real analysis by ETV-ICP-MS. Experiments using an on-line filter trapping apparatus indicated that particles produced by the ETV device were smaller than 0.1 μm in diameter. The nature and condition of the ETV graphite surface, the length of the transfer tube, and the effect that diluted seawater and palladium modifiers have on analyte transport efficiency were investigated. Transport efficiency was comparable for all elements studied and was enhanced with previously used, rather than new, graphite tubes and when seawater and palladium carriers were present. When analyte was vaporized without carrier from a new graphite tube, the transport efficiency to the plasma was approximately 10%. Approximately 70% of the total amount of analyte vaporized was deposited within the ETV switching valve, 19% onto the transfer tubing and 1% onto the components comprising the torch assembly. These conditions represent the `worst case scenario', with analyte transport to the plasma increasing to approximately 20% or more with the addition of carrier.     

Cerium oxide-deposited mesoporous silica nanoparticles for the determination of carcinoembryonic antigen in serum using inductively coupled plasma-mass spectrometry

CeO₂-deposited mesoporous silica nanoparticles were synthesized as a probe to determine carcinoembryonic antigen (CEA) in serum by inductively coupled plasma-mass spectrometry (ICP-MS). The prepared mesoporous nanoparticles were modified and tagged to the target for sandwich-type immunoassay. Fe₃O₄ magnetic nanoparticles (MNPs) were also synthesized and immobilized with antibody to extract the target biomarker. The calibration curve of the synthesized CeO₂-deposited silica nanoparticles, which was plotted by the signal ratio of ¹⁴⁰Ce/⁵⁷Fe measured by ICP-MS vs. the concentration of CEA, showed excellent linearity and sensitivity owing to the signal amplification and low spectral interference. Under optimal conditions, the sandwich-type analytical method was applied to determine CEA in serum spiked in the range of 0.001–5 ng mL⁻¹ and showed a limit of detection of 0.36 ng mL⁻¹. Since the deposited CeO₂ in the mesoporous silica layer can be substituted by other metal compounds, various kinds of metal-deposited nanoparticles can be prepared as probe materials for multiplex detection in bioanalysis.     

Analyte transport efficiencies in electrothermal vaporization for inductively coupled plasma mass spectrometry

A modified graphite furnace for solid-sampling atomic absorption spectrometry as an electrothermal vaporizer (ETV) was coupled to a Perkin–Elmer/Sciex ELAN 6000 ICP mass spectrometer. The integrals obtained from electrothermal vaporization of aliquots containing As, Cd, Cu, Co, Fe, Mn, Pb, Se, and Zn were compared with those obtained from pneumatic nebulization of the same aqueous standard solution. The pneumatic nebulizer was calibrated by weighing the mass of aqueous aerosol trapped on a filter. With “wet plasma” conditions maintained also for measurements with the ETV and reference signals for analyte signals obtained with the calibrated pneumatic nebulization, the transport efficiency of the ETV system, e.g. the ratio of the analyte amount introduced into the plasma to that amount dosed into the vaporizer, was determined. The transport efficiency of two different tube and interface designs has been evaluated. Investigations with and without the use of trifluoromethane as reactive gas, with different furnace heating rates, and with varying gas flows were performed. In general, the tube equipped with a nozzle led to generally higher transport efficiency than the standard tube. Without trifluoromethane transport efficiencies ranged from 10% to 35% with the standard tube and from 15% to 50% with the nozzle-type tube. With addition of 2 mL min^–1 trifluoromethane to the argon flow of 400 mL min^–1 through the tube, transport efficiencies from 20% to 70% and from 70% to100% were achieved with the standard and nozzle-type tubes, respectively.     

Analyte transport efficiencies in electrothermal vaporization for inductively coupled plasma mass spectrometry

A modified graphite furnace for solid-sampling atomic absorption spectrometry as an electrothermal vaporizer (ETV) was coupled to a Perkin-Elmer/Sciex ELAN 6000 ICP mass spectrometer. The integrals obtained from electrothermal vaporization of aliquots containing As, Cd, Cu, Co, Fe, Mn, Pb, Se, and Zn were compared with those obtained from pneumatic nebulization of the same aqueous standard solution. The pneumatic nebulizer was calibrated by weighing the mass of aqueous aerosol trapped on a filter. With "wet plasma" conditions maintained also for measurements with the ETV and reference signals for analyte signals obtained with the calibrated pneumatic nebulization, the transport efficiency of the ETV system, e.g. the ratio of the analyte amount introduced into the plasma to that amount dosed into the vaporizer, was determined. The transport efficiency of two different tube and interface designs has been evaluated. Investigations with and without the use of trifluoromethane as reactive gas, with different furnace heating rates, and with varying gas flows were performed. In general, the tube equipped with a nozzle led to generally higher transport efficiency than the standard tube. Without trifluoromethane transport efficiencies ranged from 10% to 35% with the standard tube and from 15% to 50% with the nozzle-type tube. With addition of 2 mL min(-1) trifluoromethane to the argon flow of 400 mL min(-1) through the tube, transport efficiencies from 20% to 70% and from 70% to 100% were achieved with the standard and nozzle-type tubes, respectively.     

Parameter optimization of electrothermal vaporization inductively coupled plasma mass spectrometry for oligoelement determination in standard reference materials

The operational parameters of the graphite furnace for electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS), i.e. the internal carrier gas flow rate, the total carrier gas flow rate, the sample pretreatment temperature and the volatilization temperature, are optimized for oligoelement determinations (⁷⁵As, ⁹Be, ¹¹²Cd, ⁵⁰Cr, ⁶⁵Cu, ¹⁰³Rh, ¹²³Sb). The volatilization temperatures of As and Cr are compared to those obtained by graphite furnace atomic absorption spectrometry (GFAAS). Several modifiers Mg(NO₃)₂, Pd(NO₃)₂, Mg(NO₃)₂/Pd(NO₃)₂, Ni(NO₃)₂, KI, (NH₄)H₂PO₄ have been tested using the concentrations recommended for GFAAS. The concentration of Mg(NO₃)₂ alone and in combination with NaCl has been varied to find the optimal modifier conditions. ETV-ICP-MS signal enhancements by a factor of 10 to 130 respective to those of conventional nebulization have been obtained. The optimized parameters are evaluated by analyzing the water standard reference NIST 1643c and the aqua regia solution of the lake sediment reference material BCR 280.     

Parameter optimization of electrothermal vaporization inductively coupled plasma mass spectrometry for oligoelement determination in standard reference materials

The operational parameters of the graphite furnace for electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS), i.e. the internal carrier gas flow rate, the total carrier gas flow rate, the sample pretreatment temperature and the volatilization temperature, are optimized for oligoelement determinations (⁷⁵As, ⁹Be, ¹¹²Cd, ⁵⁰Cr, ⁶⁵Cu, ¹⁰³Rh, ¹²³Sb). The volatilization temperatures of As and Cr are compared to those obtained by graphite furnace atomic absorption spectrometry (GFAAS). Several modifiers Mg(NO₃)₂, Pd(NO₃)₂, Mg(NO₃)₂/Pd(NO₃)₂, Ni(NO₃)₂, KI, (NH₄)H₂PO₄ have been tested using the concentrations recommended for GFAAS. The concentration of Mg(NO₃)₂ alone and in combination with NaCl has been varied to find the optimal modifier conditions. ETV-ICP-MS signal enhancements by a factor of 10 to 130 respective to those of conventional nebulization have been obtained. The optimized parameters are evaluated by analyzing the water standard reference NIST 1643c and the aqua regia solution of the lake sediment reference material BCR 280.     

Nanogold-actuated biomimetic peroxidase for sensitized electrochemical immunoassay of carcinoembryonic antigen in human serum

We present a method for the simultaneous determination of guanidinosuccinic acid (GSA) and guanidinoacetic acid (GAA) from urine by protein precipitation and liquid chromatography/tandem mass spectrometry. The chromatographic separation was performed using a cation exchange column with an elution gradient of 0.1 mM and 20 mM ammonium acetate buffers. GSA was detected with the mass spectrometer in negative ion mode monitoring at m/z 174.1, and GAA, creatinine, arginine, and homoarginine were in positive ion mode monitoring at m/z 118.1, 114.1, 175.1, and 189.1, respectively. As an internal standard, l-arginine-¹³C₆ hydrochloride and creatinine-d₃ (methyl-d₃) were used. The calibration ranges were 0.50-25.0 μg mL⁻¹, and good linearities were obtained for all compounds (r > 0.999). The intra- and inter-assay accuracies (expressed as recoveries) and precisions at three concentration levels (1.00, 5.00 and 25.0 μg mL⁻¹) were better than 83.8% and 7.41%, respectively. The analytical performance of the method was evaluated by determination of the compounds in urine from male C57BL/J Iar db/db diabetes mellitus (DM) mice. The values of GSA and GAA corrected by the ratios of the individual compounds to creatinine were significantly increased in DM mice compared with control mice. These results indicated that the newly developed method was useful for determining urinary guanidino compounds and metabolites of arginine.     

Solvent bar microextraction combined with electrothermal vaporization inductively coupled plasma mass spectrometry for the speciation of inorganic arsenic in water samples

A new method of solvent bar microextraction (SBME) combined with electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) for the speciation of As(III) and As(V) in water samples was developed. The method is based on the chelation of As(III) and ammonium pyrrolidine dithiocarbamate (APDC) under the selected conditions, and the As(III)-PDC complex could be extracted into the organic phase, while As(V) remained in aqueous solution. The post-extraction organic phase was directly injected into ETV-ICP-MS for determination of As(III) with the use of iridium as permanent chemical modifier. As(V) was reduced to As(III) by L-cysteine and was then subjected to SBME prior to total As determination. The assay of As(V) was based on subtracting As(III) from total As. The factors affecting on the SBME, such as organic solvent, sample pH, chelating reagent concentration, stirring rate and extraction time, and chemical modification of iridium in ETV-ICP-MS have been studied. Under the optimized conditions, the enrichment factor of 220-fold could be achieved in 15 min extraction, the limit of detection (LOD) for As(III) was 0.32 pg mL^− 1, and the relative standard deviation (RSD) was 8.8% (0.1 ng mL^− 1, n = 9). Compared with hollow fiber liquid phase microextraction (HF-LPME), SBME has a higher enrichment factor and faster extraction kinetics. In order to validate the accuracy of the method, a Certified Reference Material of GSBZ50004-88 (No. 200420) water sample was analyzed and the results obtained were in good agreement with the certified values. The developed method was also applied to the speciation of inorganic As in environmental waters with satisfactory results.     

Microwave sample-digestion procedure for determination of arsenic in moss samples using electrothermal atomic absorption spectrometry and inductively coupled plasma mass spectrometry

Arsenic in moss samples was determined by electrothermal atomic absorption spectrometry (ETAAS) after microwave-assisted sample digestion. Two different sample masses (500 mg and 1000 mg) and three different microwave ovens were used in the digestion. There was a slight difference in the digestion efficiency, as determined by the residual carbon concentrations of 500 mg digested samples, between the microwave ovens. The arsenic results obtained for moss reference samples were, in most cases, satisfactory. However, phosphorus was found to have a reducing influence on the arsenic peak area in the ETAAS determination. According to the results, it was not possible to reduce the phosphorus interference by increasing the amount of Mg(NO(3))(2) in the Pd-Mg chemical modifier. The arsenic results obtained by ETAAS were compared to those obtained by inductively coupled plasma mass spectrometry (ICP-MS).     

Slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry for the determination of As and Se in soil and sludge

Slurry sampling electrothermal vaporization (ETV) inductively coupled plasma mass spectrometry (ICP-MS) has been applied to determine As and Se in soil and sludge samples. The influences of instrument operating conditions and slurry preparation on the ion signals were reported. Pd and ascorbic acid were used as mixed modifiers to enhance the ion signals. The effectiveness of ETV sample introduction technique for alleviating various spectral interferences in ICP-MS analysis has been demonstrated. This method has been applied to determine As and Se in NIST SRM 2709 San Joaquin soil reference material and NIST SRM 2781 domestic sludge reference material and a farmland soil sample collected locally. Since the sensitivities of As and Se in slurry solution and aqueous solution were different, analyte addition technique was used to determine As and Se in these samples. The As and Se analysis results of the reference materials agreed with the certified values. The precision between sample replicates was better than 5% for all determinations. The method detection limit estimated from analyte addition curves was about 0.03 and 0.02 μg g⁻¹ for As and Se, respectively, in original soil and sludge samples.     

Slurry sampling fluorination assisted electrothermal vaporization-inductively coupled plasma-atomic emission spectrometry for the direct determination of metal impurities in aluminium oxide ceramic powders

A new analytical procedure for the direct determination of metal impurities (Cr, Cu, Fe and V) in aluminium oxide ceramic powders by slurry sampling fluorination assisted electrothermal vaporization-inductively coupled plasma-atomic emission spectrometry (ETV-ICP-AES) is reported. A polytetrafluoroethylene (PTFE) emulsion was used as a fluorinating reagent to promote the vaporization of impurity elements in aluminium oxide ceramic powders from the graphite tube. A vaporization stage with a long ramp time and a short hold time provided the possibility of temporal analyte-matrix separation. The experimental results indicated that a 10 μL 1% m/v slurry of aluminium oxide could be destroyed and vaporized completely with 600 μg PTFE under the selected conditions. Two aluminium oxide ceramic powder samples were used without any additional pretreatment. Analytical results obtained by using standard addition method with aqueous standard solution were checked by comparison of the results with pneumatic nebulization (PN)-ICP-AES based on the wet-chemical decomposition and analyte-matrix separation. The limits of detection (LODs) between 0.30 μg g^–1 (Fe ) and 0.08 μg g^–1 (Cu) were achieved, and, the repeatability of measurements was mainly better than 10%. Received: 28 August 2000 / Revised: 1 November 2000 / Accepted: 12 November 2000     

Direct determination of arsenic in fresh and saline waters by electrothermal vaporization inductively coupled plasma mass spectrometry

A method is described for the direct determination of arsenic in fresh and saline waters by electrothermal vaporization inductively coupled plasma mass spectrometry. Arsenic could be determined directly in waters containing up to 10 000 μg ml⁻¹ NaCl without interference from the formation of ⁷⁵ArCl⁺. For non-saline waters, arsenic was determined directly with the addition to both aqueous calibration standards and samples of 0.1 μg each of Pd and Mg to act as physical carriers. For the analysis of highly saline waters, the use of Pd and Mg chemical modifier served to thermally stabilize arsenic up to a temperature of 1000°C, while the separate addition of 8 mg of ammonium nitrate was used to remove chloride from the sample. This eliminated serious spectral interference on ⁷⁵As⁺ from ⁷⁵ArCl⁺. Although the ArCl⁺ spectral interference was completely eliminated, residual Na co-volatilized with As caused signal suppression, requiring the use of the method of standard additions for calibration. An absolute limit of detection limit for As of 0.069 pg was obtained corresponding to 6.9 pg ml⁻¹ in a 10 μl sample.     

Slurry sampling fluorination assisted electrothermal vaporization-inductively coupled plasma-atomic emission spectrometry for the direct determination of metal impurities in aluminium oxide ceramic powders

A new analytical procedure for the direct determination of metal impurities (Cr, Cu, Fe and V) in aluminium oxide ceramic powders by slurry sampling fluorination assisted electrothermal vaporization-inductively coupled plasma-atomic emission spectrometry (ETV-ICP-AES) is reported. A polytetrafluoroethylene (PTFE) emulsion was used as a fluorinating reagent to promote the vaporization of impurity elements in aluminium oxide ceramic powders from the graphite tube. A vaporization stage with a long ramp time and a short hold time provided the possibility of temporal analyte-matrix separation. The experimental results indicated that a 10 microL 1% m/v slurry of aluminium oxide could be destroyed and vaporized completely with 600 micrograms PTFE under the selected conditions. Two aluminium oxide ceramic powder samples were used without any additional pretreatment. Analytical results obtained by using standard addition method with aqueous standard solution were checked by comparison of the results with pneumatic nebulization (PN)-ICP-AES based on the wet-chemical decomposition and analyte-matrix separation. The limits of detection (LODs) between 0.30 microgram g-1 (Fe) and 0.08 microgram g-1 (Cu) were achieved, and, the repeatability of measurements was mainly better than 10%.