Coupled Plasma Mass Spectrometric Detection Research Articles

Development of a novel online sequential extraction method for the characterisation of fine dust sources using inductively coupled plasma mass spectrometric detection

Multi-elemental analysis in combination with statistical models has the potential to support the apportionment of numerous sources of airborne dust. Lack of selectivity can be overcome by the application of sequential extraction schemes. However, classical offline extraction schemes are designed for >0.5 g of sample and are not suitable for particulate matter in (sub-)mg range.Therefore, a novel online sequential extraction (OSE) scheme was developed based on the well-established Tessier and BCR schemes. The solvent composition (deionised water, ammonium nitrate, acetic acid and hydroxylammonium chloride) was adapted to allow direct online introduction of the extracts into sector-field inductively coupled plasma mass spectrometry (ICP-MS). The OSE setup was optimised regarding sample containment, flow rates, transfer lines and ICP-MS transient data recording. Four model dust source samples (soil, coal, mine overburden and road dust) were screened by OSE for elemental fractionation patterns. Characteristic fractograms were obtained demonstrating the difference in mobility of the investigated elements Na, Mg, Al, K, Ca, V, Cr, Mn, Co, Ni, Cu, Zn, Rb, Sr, Cd, Ba and Pb in the chosen sample matrices. Results for the road dust, a very fine and homogenous matrix, showed high repeatability with most relative standard deviations from quadruplicate analysis <10%. Standard deviations for the other model samples were partly higher due to lower homogeneity of these matrices at the applied sample mass of only 5 mg.Verification of the elemental fractionation via the novel OSE was performed for the road dust model sample. A flow injection setup was applied to check the accuracy of the applied post-cartridge calibration approach. Recoveries for the QC standard were 90% with SD 4%. Bracketing the OSE runs with flow injection of the QC standard demonstrated the stability of the OSE operation over several days of measurement. Variation of the sample mass revealed a significant increase of the extracted mass fractions at lower mass of 2 mg. The results of this optimised road dust OSE data set were compared to offline sequential extractions of the same sample. Average recovery for the first fraction (water-soluble) was 87% with SD 21% indicating comparable extraction efficiency by OSE. Recoveries for the other extraction steps were partly lower due to lower reagent concentrations and much shorter extraction times. However, the OSE provided repeatable results matching the extraction pattern of the offline extraction. Overall, the summed extracted mass fractions of all 4 OSE extraction steps equalled 72% of the same fractions obtained with offline extraction. Considering the operationally defined character of all sequential extraction schemes these results demonstrate the reliability of OSE for elemental fractionation of fine particulate samples at mg range sample mass.

Mercury volatile species generation from HCl and TRIS buffer media: Quantification of generation efficiency and characterization of severe changes in speciation information due to de-alkylation

Severe changes in speciation information were observed during volatile species generation (VSG) due to de-alkylation of generated Hg species as proven by cryogenic trapping with inductively coupled plasma mass spectrometric detection (CT-ICP-MS). Methyl mercury hydride is de-methylated to Hg0 by 45% and 6%, respectively, in HCl and TRIS buffer media. Ethylmercury hydride is de-ethylated to Hg0 by 71% and 28%, respectively in HCl and TRIS buffer media. Only Hg0 as a volatile product was observed when generating from phenylmercury regardless of the reaction medium employed. These findings limit significantly the application of VSG to Hg speciation analysis, especially the possibility of generation of alkyl-substituted mercury hydrides for cryogenic trapping/separation or gas chromatography. On the contrary, post-column VSG of Hg species prior to spectrometric detection can be employed to enhance sensitivity without any negative effects on accuracy and precision of the results.

Speciation of inorganic and organic species of mercury and arsenic in lotus root using high performance liquid chromatography with inductively coupled plasma mass spectrometric detection in one run

Multi-elemental speciation analysis in a single run reduces costs, waste and time, and also sample consumption, which is favorable to a large set of instable samples. This work demonstrates mercury and arsenic speciation in a single run using high performance liquid chromatography with inductively coupled plasma mass spectrometric detection (HPLC/ICP-MS). Thiol compounds in mobile phases interfered with the elution of arsenite because of coordination action, which was overcome by gradient elution (elution of As(III) by thiol-free mobile phases at first). Four arsenic forms (As(III), DMA, MMA and As(V)) and three mercury species (Hg(II), MeHg and EtHg) were separated and detected by HPLC/ICP-MS using 4 mM tetrabutylammonium hydroxide (TBAH) (pH 6.0) in the first 1.0 min and 4 mM TBAH + 20 mM L-cysteine (pH 6.0) in the next 9.0 min. The detection limits were obtained at 0.078 for As(III), 0.081 for DMA, 0.078 for MMA and 0.15 μg L−1 for As(V), and 0.016 for Hg(II), 0.027 for MeHg and 0.032 μg L−1 for EtHg, and the reproducibilities (50 μg L−1 for each As-species and 10 μg L−1 for each Hg-species) were all lower than 3.7%. The proposed method was successfully applied for speciation analyses of arsenic and mercury in five lotus roots, which indicated DMA (3.5–7.9 μg kg−1) as the only arsenic species and MeHg (0.6–1.0 μg kg−1) as the only mercury species. Analyses of two certified reference materials demonstrated good agreement between determined values and certified values. All results prove its advantages including high sensitivity and high analytical efficiency, which are beneficial for routine speciation analyses of arsenic and mercury in a single run in environmental and food fields.

Graphene oxide as a stationary phase for speciation of inorganic and organic species of mercury, arsenic and selenium using HPLC with ICP-MS detection.

This work demonstrates the power of graphene and graphene oxide (GO) as stationary phases for high performance liquid chromatography (HPLC) based elemental speciation analysis combined with detection by inductively coupled plasma mass spectrometry (ICP-MS). Inorganic mercuric and organomercuric compounds coordinate with 2-thiosalicylic acid (TSA) to form Hg-TSA complexes. These complexes are retained by GO owing to its strong π electron stacking capability for TSA. Separation of the four mercury species tested was achieved within 12min with resolutions of 1.8-3.4. Similarly, inorganic anionic species of arsenic and selenium, and organoarsenicals are electrostatically attracted by aromatic quaternary ammonium cations in the mobile phases. Organoarsenicals also can be separated by using long alkyl quaternary ammonium compounds. Aromatic quaternary ammonium compounds possess particularly high affinity to GO because of strong π interaction. This leads to effective retention of the As/Se anions. A comparison between graphene and GO as stationary phases for HPLC separation of mercury and arsenic species demonstrates negligible difference. Arsenic species are separated within 32min, and selenium species are achieved within 20min. The mobile phase also allows efficient separation of iodate, iodide, bromate, bromide, chromic acid and chromate. Analysis of a certified fish tissue by HPLC-ICP-MS using the GO@SiO2 column demonstrates its feasibility for routine elemental analysis. Good agreement is found between experimental results and certified values, with recoveries ranging between 92 and 96%. Graphical abstract Graphene oxide as a stationary phase for high performance liquid chromatography with inductively coupled plasma mass spectrometric detection (HPLC-ICP-MS) in speciation analyses of mercury, arsenic, selenium, iodine, bromine and chromium is achieved for the first time.

Determination of Non-Transferrin Bound Iron, Transferrin Bound Iron, Drug Bound Iron and Total Iron in Serum in a Rats after IV Administration of Sodium Ferric Gluconate Complex by Simple Ultrafiltration Inductively Coupled Plasma Mass Spectrometric Detection.

A rapid, sensitive and specific ultrafiltration inductively-coupled plasma mass spectrometry method was developed and validated for the quantification of non-transferrin bound iron (NTBI), transferrin bound iron (TBI), drug bound iron (DI) and total iron (TI) in the same rat serum sample after intravenous (IV) administration of iron gluconate nanoparticles in sucrose solution (Ferrlecit®). Ultrafiltration with a 30 kDa molecular cut-off filter was used for sample cleanup. Different elution solvents were used to separate each form of iron from sample serum. Isolated fractions were subjected to inductively-coupled mass spectrometric analysis after microwave digestion in 4% nitric acid. The reproducibility of the method was evaluated by precision and accuracy. The calibration curve demonstrated linearity from 5–500 ng/mL with a regression (r2) of more than 0.998. This method was effectively implemented to quantify rat pharmacokinetic study samples after intravenous administration of Ferrlecit®. The method was successfully applied to a pharmacokinetic (PK) study of Ferrlecit in rats. The colloidal iron followed first order kinetics with half-life of 2.2 h and reached background or pre-dose levels after 12 h post-dosing. The drug shown a clearance of 0.31 mL/min/kg and volume of distribution of 0.05 L/kg. 19.4 ± 2.4 mL/h/kg.

Quantitative Evaluation of Cisplatin Uptake in Sensitive and Resistant Individual Cells by Single-Cell ICP-MS (SC-ICP-MS).

One of the main limitations to the Pt-therapy in cancer is the development of associated drug resistance that can be associated with a significant reduction of the intracellular platinum concentration. Thus, intracellular Pt concentration could be considered as a biomarker of cisplatin resistance. In this work, an alternative method to address intracellular Pt concentration in individual cells is explored to permit the evaluation of different cell models and alternative therapies in a relatively fast way. For this aim, total Pt analysis in single cells has been implemented using a total consumption nebulizer coupled to inductively coupled plasma mass spectrometric detection (ICP-MS). The efficiency of the proposed device has been evaluated in combination with flow cytometry and turned out to be around 25% (cells entering the ICP-MS from the cells in suspension). Quantitative uptake studies of a nontoxic Tb-containing compound by individual cells were conducted and the results compared to those obtained by bulk analysis of the same cells. Both sets of data were statistically comparable. Thus, final application of the developed methodology to the comparative uptake of Pt-species in cisplatin resistant and sensitive cell lines (A2780cis and A2780) was conducted. The results obtained revealed the potential of this analytical strategy to differentiate between different cell lines of different sensitivity to the drug which might be of high medical interest.

Identification and determination of selenohomolanthionine – The major selenium compound in Torula yeast

Torula yeast (Candida utilis) was found to metabolize selenium in a totally different way to Brewer’s yeast (S. cerevisiae) leading to the biosynthesis of selenohomolanthionine (SeHLan), a major selenium compound accounting for 60–80% of the total selenium. The identity of SeHLan was confirmed by retention time matching in hydrophilic ion interaction chromatography (HILIC) with inductively coupled plasma mass spectrometric detection (ICP MS) using a custom synthesized standard molecule and by HILIC – Orbitrap MS and MS-MS fragmentation. Selenohomolanthionine escapes the current assays for the organic character of Se-rich yeast based on the protein-bound selenomethionine determination. A HILIC – ICP MS method was developed for the quantitative determination of selenohomolanthionine in yeast supplements with a detection limit of 146ng/g.

Photochemical vapor generation of lead for inductively coupled plasma mass spectrometric detection

Photochemical vapor generation (PCVG) of lead was successfully achieved with a simplified and convenient system, in which only low molecular weight organic acid and a high-efficiency photochemical reactor were needed. The reactor was used to generate lead volatile species when a solution of lead containing a small amount of low molecular weight organic acid was pumped through. Several factors, including the concentration of acetic acid, the concentration of hydrochloride acid, and the irradiation time of UV light were optimized. Under the optimal conditions, including the addition of 0.90% (v/v) acetic acid and 0.03% (v/v) hydrochloride acid, and irradiation time of 28s, intense and repeatable signal of lead volatile species was successfully obtained and identified with inductively coupled plasma mass spectrometry (ICPMS). In addition, the effects from inorganic anions and transition metal ions, including Cl−, NO3−, SO42−, Cu2+, Fe3+, Co2+ and Ni2+, were investigated, which suggests that their suppression to the PCVG of lead was in the order of Cl−<SO42−<NO3− for anions and Ni2+, Co2+<Fe3+<Cu2+ for transition metal ions. Under optimized conditions, relative standard derivation (RSD) of 4.4% was achieved from replicate measurements (n=5) of a standard solution of 0.1μgL−1 lead. And, the limit of quantitation (LOQ, 10σ) of 0.012μgL−1 lead was obtained using this method and the method blank could be easily controlled down to 0.023μgL−1. To validate applicability of this method, it was also employed for the determination of lead in tap water, rain water and lake water.

Rapid extraction and reverse phase-liquid chromatographic separation of mercury(II) and methylmercury in fish samples with inductively coupled plasma mass spectrometric detection applying oxygen addition into plasma

A simple and sensitive procedure was developed for extraction and speciation of mercury in fish. Species separation was accomplished with reverse phase-high performance liquid chromatography (HPLC) hyphenated to inductively coupled plasma mass spectrometry (ICP-MS). Oxygen addition into plasma allowed use of organic-rich mobile phase, achieving species separation in 4min. Mercury species extraction was achieved by microwave exposure for 2min at mild conditions (60°C, pH 2.0), avoiding necessity of neutralizing sample prior to injection in HPLC, and reducing number of sample preparation steps, analytical source of errors and inter conversion of species. Limit of detection for entire procedure was found to be 0.2 and 0.1ngg−1 for mercuric ion and methylmercury, respectively. The method was applied to certified reference materials (TORT-2 and DORM-2) and commercialized fish samples (Mullus barbatus, Sparus aurata, Trachurus mediterraneus, Mugil soiuy, Dicentrarchus labrax, and Pomatomus saltatrix) from Black Sea.

In-house validation of a method for determination of silver nanoparticles in chicken meat based on asymmetric flow field-flow fractionation and inductively coupled plasma mass spectrometric detection

Nanomaterials are increasingly used in food production and packaging, and validated methods for detection of nanoparticles (NPs) in foodstuffs need to be developed both for regulatory purposes and product development. Asymmetric flow field-flow fractionation with inductively coupled plasma mass spectrometric detection (AF4-ICP-MS) was applied for quantitative analysis of silver nanoparticles (AgNPs) in a chicken meat matrix following enzymatic sample preparation. For the first time an analytical validation of nanoparticle detection in a food matrix by AF4-ICP-MS has been carried out and the results showed repeatable and intermediately reproducible determination of AgNP mass fraction and size. The findings demonstrated the potential of AF4-ICP-MS for quantitative analysis of NPs in complex food matrices for use in food monitoring and control. The accurate determination of AgNP size distribution remained challenging due to the lack of certified size standards.

Online photochemical vapour generation of inorganic tin for inductively coupled plasma mass spectrometric detection

A highly reproducible method based on the online PCVG technique with ICPMS detection was developed for the quantitative determination of trace levels of inorganic tin for the first time.

Mercury speciation in liquid petroleum products: Comparison between on-site approach and lab measurement using size exclusion chromatography with high resolution inductively coupled plasma mass spectrometric detection (SEC-ICP-HR MS)

The accuracy of two different analytical methods dedicated to the speciation of mercury in liquid hydrocarbons is discussed in the present paper. A first step involving the comparison of a modified UOP 938 method—based on filtration, purge and extraction—with size exclusion chromatography coupled to ICP-HR MS (SEC-ICP-HR MS) was carried out on specific synthetic model mercury compounds. The modified UOP 938 method (defined here as operational speciation) allowed various mercury compounds to be grouped into different families, i.e. particulate, volatile, ionic and organic non-ionic mercury, whereas SEC-ICP-HR MS provided size distribution profiles of mercury-containing molecules. In a second step, comparison of the two different approaches was then performed with real hydrocarbon feeds, such as crude oil, condensate and straight-run gasoline samples. It was demonstrated that even though elemental Hg was present for the North Sea condensate, all of them contained ionic Hg associated to molecules containing few to many tens of carbon atoms.

Multi-dimensional Nuclear Magnetic Resonance Characterizations of Dynamics and Saturations of Brine/Crude Oil/Mud Filtrate Mixtures Confined in Rocks: The Role of Asphaltene

We propose multi-dimensional one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) techniques for probing quantitatively the different saturations and dynamics of brine/crude oil/mud filtrate mixtures confined in a rock system that could be used potentially down-hole. The rock samples and petroleum fluids have been characterized by standard petrophysical techniques. Electron spin resonance (ESR) quantitatively measured levels of the paramagnetic vanadyl ions VO2+ and organic radicals trapped in the used crude oils with and without asphaltene. Size-exclusion microchromatography with a high-resolution inductively coupled plasma–mass spectrometric detection technique has demonstrated the trapping of metalloporphyrine (MP) by asphaltene nanoaggregates. These two latter techniques have shown that around 2/3 of VO2+ is trapped in MP embedded within asphaltene nanoaggregates, while 1/3 stayed in the bulk. Standard gas chromatography (GC) and gel permeation chromatography (GPC) have exten...

Bead Injection Extraction Chromatography Using High-Capacity Lab-on-Valve as a Front End to Inductively Coupled Plasma Mass Spectrometry for Urine Radiobioassay

A novel bead injection (BI) extraction chromatographic microflow system exploiting a high-capacity lab-on-valve (LOV) platform coupled with inductively coupled plasma mass spectrometric detection is developed for rapid and automated determination of plutonium in human urine. A column attached to the LOV processing unit is loaded online with a metered amount of disposable extraction chromatographic resin (up to 330 mg of TEVA (abbreviation for tetravalent actinides)) through programmable beads transport. Selective capture and purification of plutonium onto the resin beads is then performed by pressure driven flow after preliminary sample pretreatment. The analytical results demonstrate the large capacity of bead surfaces for uptake of Pu within the tailor-made LOV platform that fosters processing of large-sized biological samples, e.g., 1 L of human urine, along with good reproducibility for automatic column renewal (0.319 ± 0.004 g, n = 5). The chemical yields of plutonium were averagely better than 90% under the optimal experimental conditions, and the entire analytical procedure could be accomplished within a short time frame (<3 h) as compared to manual counterparts (1-2 days). Therefore, the developed system is well suited for expedient analysis of low-level plutonium in urine of exposed individuals as required in emergency situations.

Trapping of Metallic Porphyrins by Asphaltene Aggregates: A Size Exclusion Microchromatography With High-Resolution Inductively Coupled Plasma Mass Spectrometric Detection Study

A combined liquid chromatography coupled to a mass spectrometer with an ICP detector (μSEC-HR ICP MS; μSEC ICP for brevity) technique was used to analyze the metals in four asphaltenes and their corresponding A1 (toluene insoluble), A2 (toluene soluble), and trapped compound (TC, heptane soluble) fractions. For three of the asphaltene samples, the normalized μSEC ICP profiles for both nickel and sulfur were very similar, showing that nickel porphyrins were distributed in almost all types of asphaltene aggregates. Extensive overlapping with sulfur profiles was observed for all vanadium and nickel profiles at retention times below the maximum bands. This suggests that large amounts of nickel and other organometallic or metal-porphyrin-type (MP) compounds are interlocked with asphaltene molecules, forming aggregates in solution. The separation of MP compounds using common separation techniques is very difficult as extraction would require dissociation into several molecules. The presence of TCs (e.g., compounds other than asphaltenes that are soluble in n-heptane) in asphaltene aggregates was related to the fractal structure of asphaltene aggregates in which voids are filled with components coming from the surrounding media. Apparently, complete trapping of TCs is achieved by performing aggregate rearrangement after penetration, leading to an aggregate structure in which the TCs remain trapped. A similar trapping mechanism is proposed herein for the MP compounds. Accordingly, no covalent bonds or specific interactions appear to be required to account for the presence of MPs within asphaltene aggregates.

Relationships between cisplatin-induced adducts and DNA strand-breaks, mutation and recombination in vivo in somatic cells of Drosophila melanogaster, under different conditions of nucleotide excision repair

Cisplatin is a chemotherapeutic drug widely used in the treatment of several tumours, but this chemotherapy presents problems in terms of side-effects and patient resistance. The detection and determination of cisplatin-induced adducts and the relationship with the physiological or clinical effects of this drug under different repair conditions could be a good measure to assess patient's response to such chemotherapy. A new methodological approach to detect and quantify cisplatin adducts by use of high-performance liquid chromatography with inductively coupled plasma mass-spectrometric detection (HPLC–ICP-MS) and isotope-dilution analysis (IDA), is evaluated for its application in vivo, under different repair conditions. This analysis is combined with the use of the Comet assay, which detects DNA strand-breaks, and the w/ w + SMART assay, which monitors induction of somatic mutation and recombination in Drosophila melanogaster in vivo under different conditions of nucleotide-excision repair. Results show that (i) cisplatin induces in Drosophila several adducts not detected in mammals. The two most abundant cisplatin-induced adducts, identified by electrospray-mass spectrometry as G monoadduct and G–G intrastrand cross-links, were quantified individually; (ii) cisplatin induces higher levels of G monoadducts and G–G cross-links in NER-proficient than in NER-deficient cells; (iii) the level of adducts correlates with their biological consequences, both in terms of DNA strand-breaks (tail-moment values), and of somatic mutation and recombination (frequency of mosaic eyes and clones in 10 4 cells), when the repair status is considered. This work demonstrates the validity and potential of the adduct detection and quantification methodology in vivo, and its use to correlate adducts with their genetic consequences.

Highly Sensitive Immunoassay Based on Immunogold−Silver Amplification and Inductively Coupled Plasma Mass Spectrometric Detection

In this work, we demonstrated a highly sensitive inductively coupled plasma mass spectrometric (ICPMS) method for the determination of human carcinoembryonic antigen (CEA), which combined the inherent high sensitivity of elemental mass spectrometric measurement with the signal amplification of catalytic silver deposition on immunogold tags. The silver amplification procedure was easy to handle and required cheap reagents, and the sensitivity was greatly enhanced to 60-fold after a 15 min silver amplification procedure. The experimental conditions, including detection of gold and silver by ICPMS, immunoassay parameters, silver amplification parameters, analytical performance, and clinical serum samples analysis, were investigated. The ICPMS Ag signal intensity depends linearly on the logarithm of the concentration of human CEA over the range of 0.07-1000 ng mL(-1) with a limit of detection (LOD, 3σ) of 0.03 ng mL(-1) (i.e., 0.15 pM). The LOD of the proposed method is around 2 orders of magnitude lower than that by the widely used enzyme-linked immunosorbent assay (ELISA) and 1 order of magnitude lower than that by clinical routine chemiluminescence immunoassay (CLIA) or time-resolved fluoroimmunoassay (TRFIA) and conventional ICPMS immunoassay. The present strategy was applied to the determination of human CEA in clinical human serum samples, and the results were in good agreement with those obtained by chemiluminescence immunoassay.

High-Throughput Sequential Injection Method for Simultaneous Determination of Plutonium and Neptunium in Environmental Solids Using Macroporous Anion-Exchange Chromatography, Followed by Inductively Coupled Plasma Mass Spectrometric Detection

This paper reports an automated analytical method for rapid and simultaneous determination of plutonium and neptunium in soil, sediment, and seaweed, with detection via inductively coupled plasma mass spectrometry (ICP-MS). A chromatographic column packed with a macroporous anion exchanger (AG MP-1 M) was incorporated in a sequential injection (SI) system for the efficient retrieval of plutonium, along with neptunium, from matrix elements and potential interfering nuclides. The sorption and elution behavior of plutonium and neptunium onto AG MP-1 M resin was compared with a commonly utilized AG 1-gel-type anion exchanger. Experimental results reveal that the pore structure of the anion exchanger plays a pivotal role in ensuring similar separation behavior of plutonium and neptunium along the separation protocol. It is proven that plutonium-242 ((242)Pu) performs well as a tracer for monitoring the chemical yield of neptunium when using AG MP-1 M resin, whereby the difficulties in obtaining a reliable and practicable isotopic neptunium tracer are overcome. An important asset of the SI setup is the feasibility of processing up to 100 g of solid substrates using a small-sized (ca. 2 mL) column with chemical yields of neptunium and plutonium being ≥79%. Analytical results of three certified/standard reference materials and two solid samples from intercomparison exercises are in good agreement with the reference values at the 0.05 significance level. The overall on-column separation can be completed within 3.5 h for 10 g of soil samples. Most importantly, the anion-exchange mini-column suffices to be reused up to 10-fold with satisfactory chemical yields (>70%), as demanded in environmental monitoring and emergency scenarios, making the proposed automated assembly well-suited for unattended and high-throughput analysis.

Multielement molecular size fractionation in crude oil and oil residue by size exclusion microchromatography with high resolution inductively coupled plasma mass spectrometric detection (HR ICP MS)

Microchromatography using permeation through gels with the increasing exclusion limit (5000, 400000 and 20000000 Da) was combined with high resolution (R = 4000) ICP MS to measure the distribution of Co, Cr, Fe, Ni, S, Si, V and Zn as a function of the molecular mass fraction of crude oil and oil vacuum distillation residue. The accuracy of the simultaneous multielement determination was verified by the µflow-injection-ICP MS analysis of certified reference materials (wear-metals in lubricating oils: SRM 1084a and SRM 1085b). The method allowed the acquisition of chromatograms with high sensitivity competitive existing methods, showing element- and sample origin-dependent morphology.

Combining asymmetrical flow field-flow fractionation with light-scattering and inductively coupled plasma mass spectrometric detection for characterization of nanoclay used in biopolymer nanocomposites

It is expected that biopolymers obtained from renewable resources will in due course become fully competitive with fossil fuel-derived plastics as food-packaging materials. In this context, biopolymer nanocomposites are a field of emerging interest since such materials can exhibit improved mechanical and barrier properties and be more suitable for a wider range of food-packaging applications. Natural or synthetic clay nanofillers are being investigated for this purpose in a project called NanoPack funded by the Danish Strategic Research Council. In order to detect and characterize the size of clay nanoparticulates, an analytical system combining asymmetrical flow field-flow fractionation (AF4) with multi-angle light-scattering detection (MALS) and inductively coupled plasma mass spectrometry (ICP-MS) is presented. In a migration study, we tested a biopolymer nanocomposite consisting of polylactide (PLA) with 5% Cloisite®30B (a derivatized montmorillonite clay) as a filler. Based on AF4-MALS analyses, we found that particles ranging from 50 to 800 nm in radius indeed migrated into the 95% ethanol used as a food simulant. The full hyphenated AF4-MALS-ICP-MS system showed, however, that none of the characteristic clay minerals was detectable, and it is concluded that clay nanoparticles were absent in the migrate. Finally, by means of centrifugation experiments, a platelet aspect ratio of 320 was calculated for montmorillonite clay using AF4-MALS for platelet size measurements.