Sample Introduction Device Research Articles

Accurate determination of ultra-trace REEs in seawater using a membrane desolvation Q-ICP-MS coupled with an online automatic separation system

A highly precise method, based on a traditional Q-ICP-MS coupled with an online automatic separation system and membrane desolvation sample introduction device, was developed for accurate determination of ultra-trace REEs in seawater samples.

Array Point Discharge as Enhanced Tandem Excitation Source for Miniaturized Optical Emission Spectrometer.

A new compact tandem excitation source was designed and constructed by using an array point discharge (ArrPD) microplasma for a miniaturized optical emission spectrometer through coupling a hydride generation (HG) unit as a sample introduction device. Three pairs of point discharges were arranged in sequence in a narrow discharge chamber to construct the ArrPD microplasma, for improved excitation capability owing to the serial excitation. Besides, the discharge plasma region was greatly enlarged, therefore, more gaseous analytes could be intercepted to enter into the microplasma for sufficient excitation, for improved excitation efficiency and OES signal. To better understand the effectiveness of the proposed ArrPD source, a new instrument for simultaneous detection of atomic emission and absorption spectral responses was also proposed, designed, and constructed to reveal the excitation and enhancement process in the discharge chamber. Under the optimized conditions, the limits of detection (LODs) of As, Ge, Hg, Pb, Sb, Se, and Sn were 0.7, 0.4, 0.05, 0.7, 0.3, 2, and 0.08 μg L-1, respectively, and the relative standard deviations (RSDs) were all less than 4%. Compared with a commonly used single point discharge microplasma source, the analytical sensitivities of these seven elements were improved by 3-6-fold. Certified Reference Materials (CRMs) were successfully analyzed with this miniaturized spectrometer, which features low power, compactness, portability, and high detectability, and is thereby a great prospect in the field of elemental analytical chemistry.

Tee-Shaped Sample Introduction Device Coupled with Direct Analysis in Real-Time Mass Spectrometry for Gaseous Analytes.

Ambient ionization mass spectrometry (AIMS) is simple to operate for analytes adsorbed on the surface of various shaped probes. However, gaseous substances or liquids that are easy to evaporate, diffuse, and escape in the atmosphere are harder to capture. In this work, a Tee-shaped sample introduction device coupled with direct analysis in real time mass spectrometry (DART-MS) is developed. The Tee-shaped device is placed between the DART ion source and the MS inlet with a heated sample transfer tube. Gaseous samples from either a Tedlar sampling bag or liquids evaporated from a graduated syringe were tested. The Tee-shaped device was used for several volatile organic compounds with a wide range of boiling points, and detection limits of ng/mL to fg/mL were obtained. To test the device for real-life samples, puff-by-puff analysis of a complex gaseous mainstream smoke was performed. Individual puffs can be analyzed rapidly, and there is no cross contamination between consecutive puffs. The dynamic changes of chemical components among different puffs for different types of cigarettes can be observed. This work provides a universal Tee-shaped sampling device to enhance AIMS for the analysis of volatile compounds and gases, which is adapted to different sampling modules applicable for various forms of samples. The device enables direct exploration of chemical components in complex gaseous samples without tedious sample preparation and time-consuming LC or GC separation.

A Combination MAI and MALDI Vacuum Source Operational from Atmospheric Pressure for Fast, Robust, and Sensitive Analyses.

Previously, vacuum matrix-assisted ionization (vMAI) was employed with matrix/analyte sample introduction into the vacuum of a mass spectrometer on a probe sample introduction device. Low attomole detection was achieved, while no carryover was observed even for concentrated samples. Here, we report a new vacuum ionization source designed to duplicate the sensitivity and robustness of probe device while providing fast multisample introduction to vacuum and rapid sequential ionization. Exposure of a sample to the vacuum of the mass spectrometer provides spontaneous ionization of volatile as well as nonvolatile analytes without the need for external energy input. However, the novel source design described herein, in addition to vMAI, can employ a laser to obtain vacuum matrix-assisted laser desorption/ionization (vMALDI). In particular, ionization by vMAI or vMALDI is achieved by using the appropriate matrix. Switching between ionization modes is accomplished in a few seconds. We present results demonstrating the utility of the two ionization methods in combination to improve the molecular analyses of sample composition. In both ionization modes, multiple samples can be sequentially and rapidly acquired to increase throughput in MS. With the prototype source, samples were acquired in as little as 1 s per sample. Exchanging multisample plates can be accomplished in as little as 2 s, suggesting low-cost high-throughput automation when properly developed.

New mass spectrometry concepts for characterization of synthetic polymers and additives.

New ionization processes have been developed for biological mass spectrometry (MS) in which the matrix lifts the nonvolatile analyte into the gas phase as ions without any additional energy input. We rationalized that additional fundamental knowledge is needed to assess analytical utility for the field of synthetic polymers and additives. Different mass spectrometers (Thermo Orbitrap (Q-)Exactive (Focus); Waters SYNAPT G2(S)) were employed. The formation of multiply charged polymer ions upon exposure of the matrix/analyte(/salt) sample to sub-atmospheric pressure directly from the solid state and surfaces facilitates the use of advanced mass spectrometers for detection of polymeric materials including consumer products (e.g., gum). Astonishingly, using nothing more than a small molecule matrix compound (e.g., 2-methyl-2-nitropropane-1,3-diol or 3-nitrobenzonitrile) and a salt (e.g., mono- or divalent cation(s)), such samples upon exposure to sub-atmospheric pressure transfer nonvolatile polymers and nonvolatile salts into the gas phase as multiply charged ions. These successes contradict the conventional understanding of ionization in MS, because can nonvolatile polymers be lifted in the gas phase as ions not only by as little as a volatile matrix but also by the salt required for ionizing the analyte through noncovalent metal cation adduction(s). Prototype vacuum matrix-assisted ionization (vMAI) and automated sources using a contactless approach are demonstrated for direct analyses of synthetic polymers and plasticizers, minimizing the risk of contamination using direct sample introduction into the mass spectrometer vacuum. Direct ionization methods from surfaces without the need of high voltage, a laser, or even applied heat are demonstrated for characterization of detailed materials using (ultra)high-resolution and accurate mass measurements enabled by the multiply charged ions extending the mass range of high-performance mass spectrometers and use of a split probe sample introduction device. Our vision is that, with further development of fundamentals and dedicated sources, both spatial- and temporal-resolution measurements are within reach if sensitivity is addressed for decreasing sample-size measurements.

Preparation of a reference material for crude oil trace elements: Study of homogeneity and stability

Trace elements can be found naturally in crude oil or can be added during the production process, transport, or storage. Due to the complexity of the determination of trace elements in crude oil, which is mainly accomplished using multi-element techniques, many reports have been published describing the optimization of instrumental parameters, the development of procedures for sample preparation, and new sample introduction devices. The goal of such research is to improve the sensitivity, precision, and accuracy of the measurements. In all the cases mentioned above, the use of reference materials (RMs) and certified reference materials (CRMs) is recommended to verify the accuracy of the new methods proposed. This paper describes the development of a natural-matrix reference material for quantification of vanadium, nickel, magnesium, sodium, calcium, strontium, and barium in crude oil. 3 kg of crude oil was processed and distributed into 115 units, each containing 20 g. The homogeneity and stability of the prepared reference material were investigated using atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry (ICP OES), and inductively coupled plasma mass spectrometry (ICP-MS) techniques. The results were evaluated using standard univariate analysis of variance (ANOVA), regression analysis, and principal component analysis (PCA). Statistical evaluation of the data showed good homogeneity and stability of the candidate reference material under the conditions studied.

Method of the Simultaneous Determination of Anions and Cations Using a Nanosized Cation Exchanger and On-Column Formation of Anionic Chelates

A method is proposed for the simultaneous determination of anions and cations of chelating metals based on anion chromatography with the chemical suppression of electrical conductivity of the mobile phase. It is distinguished by a high selectivity of the separation of groups of anions and cations. To implement the method, a special treatment of the protecting precolum with a nano-cation exchanger hydrosol solution is carried out and a special mode of operation of the automatic sample introduction device is used. The developed method can be implemented on any ion chromatograph. Examples of rapid analyses of tap and mineral waters for the concentration of inorganic anions, hardness salts, and zinc and copper impurities are given.

Separation and determination of microRNAs by high-speed capillary sieving electrophoresis.

In this work, high-speed capillary sieving electrophoresis with laser-induced fluorescence detection was applied to simultaneously determine three microRNAs. A developed manual sample introduction device for the high-speed capillary electrophoresis system was applied to perform sample injection. Strategies, including field-amplified sample injection and electrokinetic injection, were studied to improve the detection sensitivity. Under the optimal conditions, the limit of detection for DNA-159 could be lowered to 5.10×10-12 mol/L. In order to achieve enough separation resolution, two DNA probes were designed to have extra sequences that acted as the drag tails. Under the optimized conditions, the three DNA probes and the complexes of microRNA-156, microRNA-159, and microRNA-166 could be completely separated within 3.2min in backgroundelectrolyte (pH 8.7) containing 2.0% m/m polyvinyl pyrrolidone and 0.4%m/m hydroxyethyl cellulose. The limits of detection for the three microRNAs were 0.051, 0.11, and 0.25nmol/L, respectively. Then the method was applied to analyze the microRNAs spiked in the samples extracted from banana leaves. The recoveries ranged from 114.3 to 121.1% (n=3). The results showed that the method developed in this work was an effective means for microRNA assay.

Miniaturized micromachined gas chromatography with universal and selective detectors for targeted volatile compounds analysis

An effective analytical strategy for targeted analysis of volatile organic compounds which combines two orthogonal separation mechanisms and multiple tunable detection in a compact transportable analytical system is introduced. This strategy uses a commercially available micromachined gas chromatograph comprising a micromachined on-board thermal conductivity detector. The chromatograph capability is enhanced by incorporating a modified diode array detector and a radio frequency modulated ion mobility spectrometry microfabricated electromechanical system. The analytical platform offers powerful detection capabilities of individual compounds and various classes of volatile organic compounds with improved provisional confirmatory capability. The transportable micromachined gas chromatograph employs field replaceable conventional capillary columns for the separation of analytes. The use of a silicon micromachined sample introduction device affords fast injection to minimize band broadening with fast chromatographic separation rendered in the order of minutes. Advantaged synergy also includes leveraging the resolving power of gas chromatography to minimize charge exchange in the ionization chamber of the differential mobility spectrometer for improved detector performance. Performance of this scalable and transportable analytical system is demonstrated with relevant volatile compounds such as acetaldehyde, acetone, carbon disulfide, benzene, and ethyl butyrate having a day-to-day variability less than 5% and with a high degree of reliability.

Flow injection gas chromatography with sulfur chemiluminescence detection for the analysis of total sulfur in complex hydrocarbon matrixes.

A fast and reliable analytical technique for the determination of total sulfur levels in complex hydrocarbon matrices is introduced. The method employed flow injection technique using a gas chromatograph as a sample introduction device and a gas phase dual-plasma sulfur chemiluminescence detector for sulfur quantification. Using the technique described, total sulfur measurement in challenging hydrocarbon matrices can be achieved in less than 10s with sample-to-sample time <2min. The high degree of selectivity and sensitivity toward sulfur compounds of the detector offers the ability to measure low sulfur levels with a detection limit in the range of 20ppb w/w S. The equimolar response characteristic of the detector allows the quantitation of unknown sulfur compounds and simplifies the calibration process. Response is linear over a concentration range of five orders of magnitude, with a high degree of repeatability. The detector's lack of response to hydrocarbons enables direct analysis without the need for time-consuming sample preparation and chromatographic separation processes. This flow injection-based sulfur chemiluminescence detection technique is ideal for fast analysis or trace sulfur analysis.

Magnetic nanoparticles used in headspace extraction coupled with DSI-GC-IT/MS for analysis of VOCs in dry Traditional Chinese Medicine

Abstract A novel magnetic method using polystyrene modified magnetic nanoparticles to perform thermo-headspace extraction was successfully developed for extraction and preconcentration of volatile organic components in dry Traditional Chinese Medicine (TCM) based on gas chromatography-ion trap/mass spectrometry with a ChromatoProbe direct sample introduction device. The dried fruit of Amomum testaceum Ridl. was used as the object TCM. The optimum parameters of headspace magnetic solid-phase extraction were investigated, in which desorption solvent ethyl acetate played a key role in this method, and the headspace extraction temperature of 90 °C and the headspace extraction time of 15 min finally decided. Headspace solid-phase microextraction method was also used to analyze volatile compounds in the TCM to compare with the proposed method. The results show that 60 components were identified totally by two methods; most of the low boiling point chemical compounds are isolated by this new method. In this work, an environmental-friendly and cheap analytical method was established, and a new approach to analyze volatile compounds in dry Traditional Chinese Medicine was also provided.

Study of the Interference effects of Aluminium on the Atom- And Ion-Lines of Alkaline Earth Metals in Aqueous Solutions Using an ICP Spectrometer with Axially Viewed Plasma

Abstract The main advantage of inductively coupled plasma spectrometers with axially viewed plasma relative to the radially viewed plasma is the better detection power. The detection limits of the former are about 5-10 times lower than the latter. On the other hand, the axially viewed plasma has disadvantages. The most notable is the increased number of interference effects. In this paper, the study of the interference effects of aluminium on the atom- and ion-lines of alkaline earth metals are presented by examining different types of sample-introduction devices, such as a simple Meinhart-type concentric nebuliser, a V-groove nebuliser using a Sturman-Masters spray chamber, and an ultrasonic nebuliser

Microwave-Assisted Extraction/Dispersive Liquid–Liquid Microextraction Coupled with DSI-GC-IT/MS for Analysis of Essential Oil from Three Species of Cardamom

A novel method of microwave-assisted extraction coupled with polyethylene Pasteur-pipette-based dispersive liquid–liquid microextraction applying low-density organic solvent (MAE-LDS-DLLME) was successfully developed for extraction and preconcentration of essential oil from three species of cardamom (Semen Alpiniae Katsumadai, Fructus Amomi Rotundus, and Semen Myristicae). The essential oil was analyzed by gas chromatography-ion trap/mass spectrometry (GC-IT/MS) using a ChromatoProbe direct sample introduction (DSI) device. The effects of various parameters affecting the extraction process, such as the type of extraction solvent and dispersive solvent, ionic strength, microwave power, and irradiation time, were investigated thoroughly and optimized. The optimal conditions were extraction solvent of toluene, dispersive solvent of methanol, microwave power of 80 W, irradiation time of 4.0 min, plant material amount of 0.1 g, and no addition of salt. Compared with hydrodistillation, MAE-DLLME-DSI-GC–MS is a simple, rapid, low-cost, efficient, and environmentally friendly method, and the essential oil contains higher amounts of oxygenated compounds, which play an important and valuable role in terms of their contribution to the fragrance of the essential oil. In this work, we also studied the main components of the three varieties of cardamom. Qualitative and quantitative differences in the components of the three essential oils were found to be present. Based on comparison of the main bioactive compounds of essential oil, a significant difference was found between Semen Alpiniae Katsumadai or Fructus Amomi Rotundus and Semen Myristicae. This study also provides a new approach for quality assessment of traditional Chinese medicines.

Automated high‐speed CE system for multiple samples

A high-speed CE system for multiple samples was developed based on a short capillary and an automated sample introduction device consisting of a commercial multi-well plate and an x-y-z translation stage. The spontaneous injection method was used to achieve picoliter-scale sample injection from different sample wells. Under the optimized conditions, a 40 μm-long sample plug (corresponding to 78-pL plug volume) was obtained in a 50 μm id capillary, which ensured both the high separation speed and high separation efficiency. The performance of the system was demonstrated in the separation of FITC-labeled amino acids with LIF detection. Five FITC-labeled amino acids including arginine, phenylalanine, glycine, glutamic acid, and asparagine were separated within 15 s with an effective separation length of 1.5 cm. The separation efficiency ranged from 7.96 × 10(5)/m to 1.12 × 10(6)/m (corresponding to 1.26-0.89 μm plate heights). The repeatability of the peak heights calibrated with an inner standard for different sample wells was 2.4 and 2.7% (n = 20) for arginine and phenylalanine, respectively. The present system was also applied in consecutive separations of 20 different samples of FITC-labeled amino acids with a whole separation time of less than 6 min.

Influence of chemical species on the determination of arsenic using inductively coupled plasma mass spectrometry at a low liquid flow rate

The effect of common arsenic species on the ICP-MS signal working at a low liquid flow rate was investigated, taking into account the influence of the analytical concentration and of the matrix, comparing various sample introduction systems. Significant decrease (up to 65%) in the relative sensitivity of arsenite compared to arsenate was found, while methylarsonate, dimethylarsinate and arsenobetaine gave the same response (within 6%) as arsenate, throughout the 20–1000 μL min−1 liquid flow rate range. The effect was independent of the analytical concentration in the 1–100 μg L−1 range, and it was ascribed to processes related to both the sample introduction system and the ion generation and transport. Ion defocussing due to dissimilar kinetic energy of the arsenic ions generated from arsenite and arsenate was ruled out. Results obtained by various micronebulizer/spray chamber configurations showed that the temperature of the spray chamber is relevant in determining the relative responses of the arsenic species: heating the spray chamber at 60 °C caused a decrease in relative sensitivity of arsenite and dimethylarsinate compared to arsenate, while the arsenite-to-arsenate signal ratio was improved by cooling at 4 °C. The relative response of arsenite and arsenate was also significantly influenced by the presence of ammonium phosphate, which mitigated the difference between the species using conventional sample introduction devices. The influence of the chemical species on the ICP-MS signal was also investigated for species of other elements, finding significant differences in sensitivity for Hg, Se and Sn compounds when working at a low liquid flow rate. The results proved to have an effect on the accurate quantification of total concentration, as well as for arsenic speciation analysis by μHPLC/ICP-MS.

Developments in analytical technology

ABSTRACT Developments made in ICP-AES (inductively coupled plasma–atomic emission spectrometry) and ICP-MS (mass spectrometry) analytical technology over the last ten years are reviewed, focusing primarily on advancements that have impacted procedures widely available from commercial geochemical laboratories. Examples of this are the increasingly reliability of ICP-MS instrumentation that now makes it a standard production instrument providing trace analysis close to or at crustal abundance for most elements. The other significant change is the development of echelle grating solid-state detector ICP emission instruments. The high resolution offered by the echelle grating coupled with the full range of element selection and wavelength choices have dramatically improved accuracy and reduced costs. Developments in ICP-MS are reviewed, the most notable development being the wider application of high resolution ICP-MS. A magnetic sector mass spectrometer is used either with an electron multiplier detector or with individual mass collectors. The magnetic sector has improved resolution by several orders of magnitude allowing accurate determinations of elements such as Li, Bi, K, Cl, Fe, As, Se and Au at low levels and in difficult matrices. Mass throughput is superior to quadrupole detectors so that detection limits are improved, enabling highly sensitive analysis of vegetation and waters for exploration. Multi-collector (MC) technology allows for isotopic analyses that are comparable to those from thermal ionization mass spectrometry (TIMS). Sample introduction devices such as laser ablation can be used for direct analysis of solids and to determine the composition of mineral grains and inclusions. In this area, MC-ICP-MS can provide superior results to TIMS.

Design and evaluation of a new fully microwave-assisted liquid sample introduction device for inductively coupled plasma atomic emission spectrometry

A new fully microwave-assisted liquid sample introduction system (MASIS) is presented and evaluated in Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). The device employs a single TM010 microwave cavity for the simultaneous aerosol generation and desolvation. The different experimental requirements of both physical processes demand a careful system design and a judicious selection of the experimental conditions. The behavior of the MASIS depends on the: (i) microwave power; (ii) nebulizer nozzle inner diameter; (iii) sample uptake rate; and, (iv) matrix nature (i.e. acids, salts) and concentration. Thus, optimum operating conditions are obtained when increasing the microwave power, the matrix concentration and the sample uptake rate as well as when decreasing the nebulizer nozzle inner diameter. The analytical figures of merit afforded by the MASIS in ICP-AES are compared to those obtained with: (1) a pneumatic concentric nebulizer coupled to a cyclonic spray chamber (CS); (2) a microwave thermal nebulizer (MWTN) coupled to a cyclonic spray chamber; and (3) a pneumatic nebulizer coupled to a microwave desolvation system (MWDS). MASIS provides limits of detection up to 50 times lower than those obtained with the CS and up to 8 times lower than those with the MWTN and MWDS. No significant difference in the signal precision between the different devices tested is observed (i.e. 2–5%). Regarding the wash-out times, both MASIS and MWDS show the highest values of this parameter (i.e. 70 s) due to their higher inner volume. Wash-out time values for both MWTN and CS are lower than 30 s.

Dynamic hollow fiber protected liquid phase microextraction and quantification using gas chromatography combined with electron capture detection of organochlorine pesticides in green tea leaves and ready-to-drink tea

The dynamic hollow fiber protected liquid phase microextraction (DHFP-LPME) technique was evaluated for the extraction of organochlorine pesticides (OCPs) in green tea leaves and ready-to-drink tea prior to gas chromatography combined-electron capture detection (GC–ECD) analysis. A conventional microsyringe with a 1.5 cm length of hollow fiber attached to its needle was connected to a syringe pump to perform the extraction. The microsyringe was used as both the microextraction device and the sample introduction device for GC–ECD analysis. In this work, the organochlorine pesticides were extracted and condensed to a volume of 3 μl of organic extracting solvent (1-octanol) confined within a 1.5 cm length of hollow fiber. The effects of extraction solvent, extraction time, sample agitation, plunger speed, and extraction temperature and salt concentration content on the extraction performance were also investigated. Good enrichments were achieved (34–297-fold) with this method, and good repeatabilities of extraction were obtained, with full name (RSDs) below 12.57%. Detection limits were much below 1 μg l −1 for ready-to-drink tea and much below 1 μg g −1 for green tea leaves.

Determination of procymidone residues in ginseng by GC–ECD and GC–MS equipped with a solvent-free solid injector

A rapid method for determination of the insecticide procymidone in ginseng was studied by gas chromatographic analysis equipped with a solvent-free solid injector, Keele injector. Ginseng samples were freeze-dried, weighed carefully in milligram quantities and introduced into a glass tube in a Keele injector at a gas chromatograph injection port. The glass tube was then crushed to allow the sample to directly carry onto a capillary column in a normal manner. The recoveries of procymidone by the Keele injector method were close to those by a traditional method using a syringe, giving the recovery values ranging from 86% to 92% at the tested concentrations of 0.1 and 1.0 mg/kg. The Keele injector method was examined to detect procymidone in ginsengs obtained from agricultural markets. When 27 ginseng samples were analyzed by GC–MS and GC–ECD equipped with the Keele injector method, 14 samples of them contained procymidone in concentrations ranging from 0.2 to 0.8 mg/kg, which was the same results by the traditional method. Using the Keele injector method could skip sample preparation steps required generally in the traditional method. The data suggest that the Keele injector can be used as a sample introduction device for GC–ECD or GC–MS analysis of procymidone residues in ginsengs.

On-site environmental analysis by membrane extraction with a sorbent interface combined with a portable gas chromatograph system

A novel device, membrane extraction with a sorbent interface (MESI) coupled with a portable gas chromatograph (GC) system, has been developed. The main components of this system include a membrane module, a microtrap, and a control unit for the heater and cooler. The membrane module, as an on-line sample-introduction device for this system, can be manipulated in different configurations, allowing for the selective permeation of analytes across the membrane into the carrier/stripping gas. The analytes are trapped and concentrated onto a microtrap, which serves as an injector for gas chromatography separation. A concentration pulse of the trapped analytes is generated through direct electrical heating of the microtrap. The characteristics of this system have been explored, and its applicability and effectiveness have been demonstrated in field monitoring applications including the analysis of toluene in wastewater, Volatile organic compounds (VOCs) in laboratory air, and chloroform in swimming-pool water. This system is very promising, as it is a simple, fast, and portable tool for on-site process environmental monitoring.