Speciation analysis in on-line aerosol mass spectrometry

Ambient aerosol particles affect both the earth's climate and human health. Both effects depend on the chemical composition of the particles including the binding state of specific elements. Modern on-line aerosol mass spectrometry is capable of measuring aerosol composition with high temporal resolution, avoiding artifacts often introduced by classical off-line methods. The two most common types of on-line aerosol mass spectrometers, laser desorption/ionization mass spectrometers (LDI-MS) and thermal desorption electron impact ionization mass spectrometers (TD-EI-MS) provide reliable information on the most common ambient inorganic and organic aerosol species with high temporal resolution. However, for less common aerosol species identification with both types of instrument is frequently associated with large uncertainties. Here, we provide an overview of the element speciation capabilities of current on-line aerosol mass spectrometry for both carbonaceous and non-carbon-containing aerosol species. We describe limitations and other issues for this type of on-line aerosol analysis.     

Speciation analysis of oxides with static secondary ion mass spectrometry

Speciation analysis of inorganic solids, without dissolution of the sample, aims at specific molecular information. Two potentially useful microanalytical techniques emerge, namely, laser microprobe mass spectrometry (LMMS) and static secondary ion mass spectrometry (S-SIMS). This paper focuses on the molecular characterisation of oxides by application of the S-SIMS method. For this purpose, mass spectra of pure oxides were acquired under static conditions. Analytical parameters such as repeatability, accuracy and resolution were assessed. Also, the peak patterns in the mass spectra are discussed in connection with the older Plog model, describing the relative ion yield as a function of the cluster size. Finally, a comparison is made with the mass spectra from a S-SIMS library and with those obtained by Fourier transform LMMS. Copyright 1999 John Wiley & Sons, Ltd.     

Comparison of SSI with APCI as an interface of HPLC-mass spectrometry for analysis of a drug and its metabolites

Sonic spray ionization (SSI) was compared with atmospheric pressure chemical ionization (APCI) as an interface of high-performance liquid chromatography (HPLC)-mass spectrometry (MS) for sensitive analyses of a neuroleptic drug, haloperidol and its two metabolites, such as reduced haloperidol and 4-(4-chlorophenyl)-4-hydroxypiperidine (CPHP), in biological samples. For both SSI and APCI interfaces, HPLC-MS-MS gave higher sensitivity than HPLC-MS. The sensitivities by HPLC-SSI-MS-MS for haloperidol and reduced haloperidol were 100 and 30 times higher, respectively, than those by HPLC-APCI-MS-MS; no spectrum with recognizable peaks was obtained for CPHP with the APCI interface. Therefore, detection limits and regression equations were examined by the HPLC-SSI-MS-MS for human plasma and urine samples spiked with the above drug and its metabolites. Haloperidol, reduced haloperidol, and CPHP showed good linearity in the ranges of 5-800, 10-800, and 100-800 ng/mL, respectively, for both human plasma and urine; their detection limits were 2.5, 5, and 75 ng/mL, respectively, using a new polymer HPLC column which enabled direct application of biological samples.     

氢化物发生原子荧光结合计算法测定大气颗粒物中砷的形态

运用碱式消解法对样品进行前处理,采用氢化物发生-原子荧光光谱数学计算法测定大气颗粒物中As(Ⅲ)和As(Ⅴ)的含量。探讨了还原剂用量、酸介质及其酸度、载气及屏蔽气流量和观测高度等对荧光强度的影响,分析了共存离子对砷测定的干扰。在选定的最佳条件下,得到检出限为0.34μg/L,加标回收率为87.8%～108.2%。方法可用于测定大气颗粒物中不同形态的砷。     

Speciation of metal-EDTA complexes by flow injection analysis with electrospray ionization mass spectrometry and ion chromatography with inductively coupled plasma mass spectrometry

Flow injection analysis (FIA) with ESI-MS and ion chromatography (IC) with inductively coupled plasma-MS (ICP-MS) as the complementary technique have been explored for the determination of metal ions as their metal-EDTA complexes. ESI-MS enabled the identification of metal-EDTA complexes such as [Mn(EDTA)](2-), [Co(EDTA)](2-), [Ni(EDTA)](2-), [Cu(EDTA)](2-), [Zn(EDTA)](2-), [Pb(EDTA)](2-), and [Fe(EDTA)](1-) and their MS spectral showed that these metal-EDTA complexes were present in solution. Based on the ESI-MS, ion chromatographic separation and ICP-MS detection of these complexes are possible because IC-ICP-MS requires stable metal-EDTA complex during the chromatographic separation. The separation of these metal-EDTA complexes was achieved on an anion-exchange column with a mobile phase containing 30 mM NH(4)(HPO(4))(2) at pH 7.5 within 7 min with ICP-MS providing element specific detection. The ICP-MS LODs for the metal-EDTA were in the range of 0.1-0.5 microg/L with the exception of Fe (15 microg/L). The proposed method was a simple procedure for sample processing, using direct injection of sample without removal of sample matrix and was successfully applied to the determination of metal-EDTA complexes in real samples.     

Speciation analysis of inorganic arsenic by microchip capillary electrophoresis coupled with hydride generation atomic fluorescence spectrometry

A novel method for speciation analysis of inorganic arsenic was developed by on-line hyphenating microchip capillary electrophoresis (chip-CE) with hydride generation atomic fluorescence spectrometry (HG-AFS). Baseline separation of As(III) and As(V) was achieved within 54 s by the chip-CE in a 90 mm long channel at 2500 V using a mixture of 25 mmol l(-1) H3BO3 and 0.4 mmol l(-1) CTAB (pH 8.9) as electrolyte buffer. The precisions (RSD, n=5) ranged from 1.9 to 1.4% for migration time, 2.1 to 2.7% for peak area, and 1.8 to 2.3% for peak height for the two arsenic species at 3.0 mg l(-1) (as As) level. The detection limits (3sigma) for As(III) and As(V) based on peak height measurement were 76 and 112 microg l(-1) (as As), respectively. The recoveries of the spikes (1 mg l(-1) (as As) of As(III) and As(V)) in four locally collected water samples ranged from 93.7 to 106%.     

Speciation analysis of mercury by solid-phase microextraction and multicapillary gas chromatography hyphenated to inductively coupled plasma-time-of-flight-mass spectrometry

This paper reports the development of an analytical approach for speciation analysis of mercury at ultra-trace levels on the basis of solid-phase microextraction and multicapillary gas chromatography hyphenated to inductively coupled plasma-time-of-flight mass spectrometry. Headspace solid-phase microextraction with a carboxen/polydimethylsyloxane fiber is used for extraction/preconcentration of mercury species after derivatization with sodium tetraethylborate and subsequent volatilization. Isothermal separation of methylmercury (MeHg), inorganic mercury (Hg2+) and propylmercury (PrHg) used as internal standard is achieved within a chromatographic run below 45 s without the introduction of spectral skew. Method detection limits (3 x standard deviation criteria) calculated for 10 successive injections of the analytical reagent blank are 0.027 pg g(-1) (as metal) for MeHg and 0.27 pg g(-1) for Hg2+. The repeatability (R.S.D., %) is 3.3% for MeHg and 3.8% for Hg2+ for 10 successive injections of a standard mixture of 10pg. The method accuracy for MeHg and total mercury is validated through the analysis of marine and estuarine sediment reference materials. A comparison of the sediment data with those obtained by a purge-and-trap injection (PTI) method is also addressed. The analytical procedure is illustrated with some results for the ultra-trace level analysis of ice from Antarctica for which the accuracy is assessed by spike recovery experiments.     

毛细管电泳-电感耦合等离子体质谱法测定藻类中6种不同形态的砷化合物

建立了一种利用毛细管电泳与电感耦合等离子体质谱联用技术(CE-ICP-MS)分析检测6种不同形态砷化合物的方法。详细研究了缓冲溶液的种类、pH值和浓度,分离电压以及进样时间等因素对6种砷化合物的分离度、灵敏度和重现性等的影响。结果表明,在最佳条件下,三价砷(As3+)、一甲基砷(MMA)、二甲基砷(DMA)、五价砷(As5+)、砷胆碱(AsC)和砷甜菜碱(AsB)6种化合物在25 min内得到完全分离。6次平行测定中,6种砷化合物峰面积的相对标准偏差(RSD)为3%～5%,检出限(以As计)(3倍信噪比)为0.08～0.12 μg/L。应用该方法成功地对海带中6种砷化合物进行了分析,回收率为90%～103%。该方法具有耗时短、灵敏度高、样品消耗量少、稳定性好等优点,可用于藻类样品中不同形态砷化合物的分析。     

Speciation analysis of organoarsenical compounds in biological matrices by coupling ion chromatography to atomic fluorescence spectrometry with on-line photooxidation and hydride generation

The optimisation of an on-line decomposition based on UV photooxidation for the analysis of organoarsenic species by coupling cation-exchange chromatography and atomic fluorescence spectrometry with hydride generation, is described. In this study, special consideration is given to the compatibility of mobile phases with post-column treatments. Results show that the most commonly used mobile phase, aqueous pyridine solutions, decreases species conversion efficiency, leading to a significant loss of sensitivity. New fully-compatible chromatographic conditions are proposed to separate arsenobetaine, arsenocholine, trimethylarsine oxide and tetramethylarsonium ion within 20 min. The very low absolute limits of detection, 4-12 pg(As), allow speciation at trace levels. Analysis of a certified reference fish tissue (DORM-2) and other seafood samples (French and Chilean oysters and mussel) highlights the robustness and the accuracy of the optimised system.     

Speciation analysis of arsenic in traditional Chinese medicines by hydride generation-atomic fluorescence spectrometry.

A method has been described for the determination of arsenic species (arsenite and arsenate) by hydride generation-atomic fluorescence spectrometry (HG-AFS). The experimental conditions that influence the fluorescence intensity and the reduction of arsenic were investigated and optimized, and the influences from foreign ions and their elimination were studied. The detection limit was found to be 79.7 ng L(-1). The proposed method was applied to the determination of arsenic species in water leachate of traditional Chinese medicines with a recovery range of 91.1-109.5%.     

Direct-injection mass spectrometry adds the time dimension to (B)VOC analysis

In the past decade, we have witnessed rapid development of direct-injection mass spectrometric (DIMS) technologies that combine ever-improving mass and time resolution with high sensitivity and robustness. Here, we review some of the most significant DIMS technologies, which have been applied to rapid monitoring and quantification of volatile organic compounds (VOCs) and biogenic VOCS (BVOCs). They include MS-e-noses, atmospheric-pressure chemical ionization (APCI), proton-transfer-reaction mass spectrometry (PTR-MS), and selected ion-flow-tube mass spectrometry (SIFT-MS). DIMS-based MS-e-noses provide the possibility to screen large sample sets and may yield rich analytical information. APCI is a widespread ionization method and pioneered DIMS in environmental and flavor-release applications. SIFT-MS and PTR-MS allow better control of precursor-ion generation and hence of the ionization process. SIFT-MS puts the focus on control of the ionization process, while PTR-MS does so on sensitivity. Most (B)VOCs of interest can be efficiently detected and often identified by DIMS, thanks also to the possibility of switching between different precursor ions and the recent realization of time-of-flight-based equipments. Finally, we give selected examples of applications for each of the key technologies, including research in food-quality control (MS-e-nose), flavor release (APCI), environmental sciences (PTR-MS) and health sciences (SIFT-MS).     

Speciation of chromium in solid materials with the aid of soft-X-ray spectrometry

Chromium compounds can be found in many different forms in steel and steel coatings. They are capable of strongly influencing the mechanical and technological properties of the material. Chromium occurs in steel mainly as a metal or in the carbide or nitride form. In the surface refinement of steel sheets, Cr(III) and Cr(VI) compounds are also used. With the development and optimisation of metallurgical processes, there is an increased demand for the determination of compounds in which chromium is present. X-Ray-spectra in the soft-X-ray area (2–15 nm) contain all the information necessary for characterisation and quantification of the chromium compounds. Generation and analysis of these X-ray spectra is in principle easily possible with a common wavelength-dispersive X-ray-fluorescence spectrometer. When an electron source for low-energy electrons (2–6 keV) is used instead of the usual X-ray tube, essentially better results are obtained, in comparison to the conventional X-ray-fluorescence spectrometer. The technical steps for changing an X-ray-fluorescence-spectrometer to a soft-X-ray-spectrometer are described. At the hand of the examination of galvanised steel sheets the analytical potential of this method was tested. The differentiation between Cr(III) and Cr(VI) is possible with sufficient precision.     

New coupling of planar chromatography with direct analysis in real time mass spectrometry

The coupling of planar chromatography with direct analysis in real time time-of-flight mass spectrometry (DART-TOF-MS) was shown for the first time. Cutting the plate within a track led to substance zones positioned on the plate edge which were directly introduced into the DART gas stream. Mass signals were obtained instantaneously within seconds. Detectability was shown in the very low ng-range per zone on the example of isopropylthioxanthone. The coupling was perfectly suited for identification and qualitative purposes, but it was initially critical for quantification of results. Analytical response (R2 0.8202) and repeatability were strongly dependent from proper manual positioning of the HPTLC plate into the electronic or vibronic excited-state gas stream of the ion source. This drawback was overcome by using stable isotope-labeled standards shown on the example of caffeine. This way, analytical response (R2 0.9892) and repeatability (RSD < +/- 5.4%, n=6) were improved to a high extent. Spatial resolution by an in-house-built plate holder system was shown to be better than 3 mm. The decay of the signal was observed. The efficacy of this new coupling was compared to a plunger-based extraction device for HPTLC/electrospray ionisation-MS. The latter device showed detectability down to the pg-range, e.g. the limit of quantification for isopropylthioxanthone was found to be 100 pg. Repeatability was comparable (RSD +/- 6.7%), however, without the need of internal standard correction. Analytical response was slightly better and showed a determination coefficient R2 of 0.9983. Similar data were obtained for caffeine as well. Spatial resolution was 2 mm or 4 mm depending on the plunger head used. The comparison showed that HPTLC/DART-TOF-MS is a useful coupling method regarding qualitative aspects and it has the potential to cope also with the difficulties of quantification if isotope-labeled standards were used or if a plate holder system is employed as initially shown.     

Speciation of butyltin compounds by ion chromatography coupled to electrothermal atomic absorption spectrometry

A new method for the determination of butyltin species by ion-exchange chromatography linked with graphite-furnace electrothermal atomic absorption spectrometry (ETAAS) is presented. The separation is achieved on a strong cation-exchange column with a 0.18 mol dm^?3 solution of diammonium citrate at pH 6.5 with a step change to pH 4.0 in 60:40 methanol/water solvent. ETAAS detection is performed on-line using an oxidizing matrix modifier. Mono-, di- and tri-butyltin may be determined in a single experiment with detection limits of (respectively) 0.5, 1.1 and 0.8 ng (Sn). Applications to actual samples are reported.     

Speciation analysis of selenium in rice samples by using capillary electrophoresis-inductively coupled plasma mass spectrometry

An enzyme-assisted extraction used to extract all species of selenium in rice sample and a sensitive analytical method for the determination of ultratrace Se(VI), Se(IV), SeCys₂ (selenocystine) and SeMet (selenomethionine) with capillary electrophoresis-inductively coupled plasma mass spectrometry were firstly described in this study. The extraction method is simple, effective and can be used to extract trace selenium compounds in rice with high extraction efficiency and no altering its species. The analytical method has a detection limit of 0.1-0.9 ng Se/mL, and can be used to determine trace Se(VI), Se(IV), SeCys₂ and SeMet in rice directly without any derivatization and pre-concentration. With the help of above methods, we have successfully determined Se(VI), Se(IV), SeCys₂ and SeMet in selenium-enriched rice within 18 min with a recovery of 90-103% and a RSD (relative standard deviation, n = 6) of 3-7%. Our results indicated that selenium-enriched rice contained only one species of selenium, SeMet, and its concentration is in range of 0.136-0.143 μg Se/g dried weight. The proposed method providing a realistic approach for the nutritional and toxical evaluation of different selenium compounds in nutritional supplements.     

Speciation analysis of arsenic compounds in edible oil by ion chromatography-inductively coupled plasma mass spectrometry

An inductively coupled plasma mass spectrometer (ICP-MS) was used as an ion chromatographic (IC) detector for the speciation analysis of arsenic in edible oil. The arsenic species studied include arsenite, arsenate, monomethylarsonic acid, dimethylarsinic acid, arsenobetaine and arsenocholine. Gradient elution using (NH(4))(2)CO(3) and methanol at pH 8.5 allowed the chromatographic separation of all species in less than 8 min. Effluents from the IC column were delivered to the nebulizer of ICP-MS for the determination of arsenic. The concentrations of arsenic species have been determined in several used and fresh vegetable oil samples. In this study, a microwave-assisted extraction method was used for the extraction of arsenic species from oil samples. The extraction efficiency was better than 92% and the recoveries from spiked samples were in the range of 90-105%. The precision between sample replicates was better than 8% for all determinations. The limits of detection were in the range of 0.008-0.024 ng mL(-1) for various arsenic species based on peak height, which corresponded to 0.08-0.24 ng g(-1) in the original oil sample. The major arsenic species in the used oil samples varied based on the food items cooked.     

Speciation analysis of manganese in tea samples using flame atomic absorption spectrometry after cloud point extraction

The speciation of Mn(II) in tea infusion was studied using cloud point extraction (CPE). In tea infusion, the flavonoid-bound Mn(II) was extracted at pH 5.0 using Triton X-100 (TX-100), the remaining free aquated Mn(II) and weakly-complexed Mn(II) in solution were both chelated with 8-hydroxyquinoline (HOx) and CPE-preconcentrated with TX-100. The enriched analyte was determined by flame AAS. The optimal concentrations for CPE of 0.02 ppm Mn were as follows: TX-100, 0.2% (v/v); HOx, 1.0 × 10⁻⁴ M; NaCl, 1.0% (w/v). LOD was 1.9 μg/L with a preconcentration factor of 10–20. The method was validated using a standard XAD-resin separation procedure and applied to synthetic seawater and CRM samples.     

Speciation analysis of mercury and lead in fish samples using liquid chromatography-inductively coupled plasma mass spectrometry

A liquid chromatography-inductively coupled plasma mass spectrometric (LC-ICP-MS) method for lead and mercury speciation analysis was described. Sample containing ionic lead and mercury compounds was subjected to liquid chromatographic separation before injection into the direct injection high efficiency nebulizer (DIHEN, 170-AA). The species studied include inorganic lead (Pb(II)), trimethyl lead (trimethyl-Pb), triethyl lead (triethyl-Pb), inorganic mercury (Hg(II)), methyl mercury (methyl-Hg) and ethyl mercury (ethyl-Hg), which were well separated by reversed-phase liquid chromatography with a C18 column as the stationary phase and a pH 2.8 solution of 0.2% (v/v) 2-mercaptoethanol, 1 mg L(-1) ETDA, 174.2 mg L(-1) sodium 1-pentanesulfonate and 12% (v/v) methanol as the mobile phase. The lead and mercury species in biological tissues were quantitatively extracted, into 10 g L(-1) EDTA and 0.2% (v/v) 2-mercaptoethanol solution taken in a closed centrifuge tube and kept on water bath, using microwaves at 65 degrees C for 2 min. The spike recovery of individual lead and mercury species determined by spiking the samples with suitable concentration of lead and mercury mixture standard were between 93% and 99%. The detection limits of the species studied were in the range 0.1-0.3 microg Pb L(-1) and 0.2-0.3 microg Hg L(-1). The procedure has been applied for the speciation analysis of two reference samples namely NRCC DOLT-3 Dogfish Liver and DORM-2 Dogfish Muscle and a swordfish sample obtained locally. The sum of the concentrations of individual species has been compared with the certified values for total lead and mercury to verify the accuracy of the method. The precision between sample replicates was better than 10% with LC-DIHEN-ICP-MS method.