A frozen suspension external calibration strategy for elemental quantitative imaging of fresh plant soft tissues by LA-ICP-MS with cryogenic ablation cell.

A simple and reliable external calibration strategy of LA-ICP-MS for fresh plant soft tissues was developed. The prepared plant suspension was frozen by the designed cryogenic ablation cell and used as external standard for quantitative elemental imaging analysis of fresh plant tissues. The controllable water content of the prepared external standards provides a similar matrix with fresh soft tissues, and a homogeneous elemental distribution could be ensured due to the fine grinding particle sizes. More interestingly, the presence of water increased the signal intensity produced by the suspension by a factor of 1.6 (Pb) to 66.6 (La) compared to that of the pressed cake. The excellent dispersing property and advantage of long-term use were achieved owing to the employment of 0.1% PAANa as suspending agent. A series of plant reference materials were analyzed, and the relative errors of most elements were less than 10 %, indicating that there is a reliable accuracy of the proposed method. The limits of detection (LODs) ranged from 0.1 ng·g-1 (La) to 1279 ng·g-1 (S). This method was used for elemental imaging analysis in rice leaves under arsenic stress, and the results were consistent with previous studies, which mean that the proposed method could provide technical support for researchers in the fields of agriculture and environment.

Elemental Imaging of Fertilized ZnO NP Wheat Endosperms Using Laser Ablation-Inductively Coupled Plasma Optical Emission Spectrometry.

Zinc (Zn) is an essential trace element in the human body, and its deficiency can seriously affect health. Agronomic Zn biofortification with ZnO nanoparticles (ZnO NPs) in consumable wheat prospectively relieves Zn deficiency. We developed an elemental quantitative imaging laser ablation-inductively coupled plasma optical emission spectrometry method to examine the distributions of Zn and other micronutrient elements in wheat grain and the endosperm. After foliar application of ZnO NPs (four rounds), Zn content in the endosperm can be significantly increased (221 ± 61%), and the Zn, Ca, Mg, and P content gradient decreased from the outside seed coat and aleurone layer to the endosperm, whereas the Fe, Mn, K, Cu, Sr, and Ba content gradient decreased from the crease region to the deeper endosperm. This may indicate how different elements enter the endosperm. Foliar application of ZnO NPs did not change the micronutrient accumulation pattern but did change their contents in wheat grain.

Direct multi-elemental analysis of cerebrospinal fluid samples by LA-ICP-MS employing an aerosol local extraction cryogenic ablation cell.

A novel method for direct high-throughput analysis of multi-elements in cerebrospinal fluid (CSF) samples by laser ablation inductively coupled plasma mass spectrometry with an aerosol local extraction cryogenic ablation cell (ALEC-LA-ICP-MS) was developed. Microliter-level CSF samples were frozen by a designed cryogenic ablation cell and directly analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) without time-consuming pretreatment. Compared with the precision obtained at room temperature (20℃), that obtained at low temperature (- 25℃) was significantly improved; the RSDs were reduced from 8.3% (Zn) to 32.6% (Mn) to 2.2% (Pb) to 6.5% (Mn) with six times parallel determination. To meet the analytical requirement of the micro-volume CSF samples, the laminar flow aerosol local extraction strategy was adopted to improve the transmission efficiency of aerosols, and the signal intensity was increased by four times compared with the standard commercial ablation cell. The standard solution with 0.4% bovine serum albumin (BSA) matrix was used as matrix-match external standard, and Rh was added into the samples as internal standard. The limits of detection (LODs) ranged from 0.17 µg·L-1 (Mn) to 8.67 µg·L-1 (Mg). Standard addition recovery experiments and the determination of CRM serum L-1 and L-2 were carried out to validate the accuracy of the method; all results indicated there were excellent accuracy and precision in the proposed method. The matrix-scanning function in the GeoLas software combined with the microwell plate realizes the high-throughput automatic analysis. Twenty-four CSF samples from different patients were determined; the results showed that there might be a correlation between the metal elements in CSF and the diseases, which means that the proposed method has potential in the diagnosis of neurological diseases.

Development of a fully automatic separation system coupled with online ICP-MS for measuring rare earth elements in seawater.

Rare earth elements (REEs) are useful geological indicators of marine geochemistry. However, extremely low concentrations (sub-ng L-1) and high-salt matrices result in inefficient measurements. A fully automatic separation system (ELSPE-2 Precon) is used in the online determination of ultra-trace REEs in seawater using inductively coupled plasma mass spectrometry. This system mainly comprises three sections: (i) an auto-sampler (eas-2A) with 120 positions; (ii) a poly(styrene-divinylbenzene) resin column (Prin-Cen Col007) with iminodiacetic and ethylenediaminetriacetic acid functional groups to eliminate the high-salt matrix (e.g., Na, Ca, K, Mg, Al, Ba, Fe, Sr, P, and S) and preserve the target REEs; and (iii) a Trp002 cleanup column for the reduction of the reagent and procedural blank values. The detection limits (3σ) were in the range 0.002 (Dy)-0.097 ng L-1 (La), and the long-term reproducibility (8 h) was between 80% and 120% for all REEs in a 3.5% NaCl matrix solution. The accuracy of this method was verified using a seawater reference material (NASS-6), and the measured REE concentrations were consistent with those previously reported. The proposed online system was used to investigate coastal water samples with varying salinities from the Pearl River Estuary (Guangdong, China). Variations in the REE distribution patterns of different layers of seawater were observed, which could be due to the mixing of potentially light rare earth element-enriched bottom seawater. Moreover, a positive Gd anomaly in river water and seawater might be attributed to anthropogenic pollution from hospitals and the pharmaceutical industry.

One-step separation of Cu, Fe, Zn and Cd and isotope ratio analysis by MC-ICP-MS for geological samples.

Multi-isotope systems have shown great application potential in tracing geological and environmental processes. In order to obtain the isotopic composition of multiple elements of interest, the common protocol is to separate each element from the matrix by independent procedures, which has some limitations, including poor efficiency, being time-consuming, requiring large samples and being unsuitable for rare samples (e.g., meteorite, lunar soil and atmospheric aerosol samples). In this study, we present an integrated and optimized one-step method to separate Cu, Fe, Zn and Cd from complex matrix elements using the AG MP-1M anion exchange resin. By experimentally optimizing the resin volume, eluent concentration and eluent amount, these target elements can be effectively separated from the matrix elements, such as Cu separation from Ti and Co, Zn separation from Fe and Cd, and Cd separation from Sn. The recoveries of Cu, Fe, Zn and Cd were 100.1 ± 0.8% (2SD, n = 3), 99.8 ± 0.7% (2SD, n = 3), 100 ± 0.8% (2SD, n = 3) and 99 ± 1% (2SD, n = 3), respectively. Moreover, the resolution (R) between the elements of interest and interfering elements was in the range of 1.8-28.1. The process blanks of Cu, Fe, Zn and Cd were 1-1.6 ng, 62-70 ng, 2.1-3 ng and 66-74 pg, respectively. The obtained isotope ratios for the standard reference materials agreed well with the published values. Meanwhile, we have reported the Cu, Fe and Zn isotope ratios of six soil and sediment standard reference materials, namely NIST 2711a, GSS-1, GSD-5a, GSD-7a, GSD-12 and GSD-23, for the first time. These new data can be used for the intercalibration and quality control of soils and sediments in other laboratories. The one-step separation of Cu, Fe, Zn and Cd shows obvious economic and efficiency advantages, making it suitable for the simultaneous separation of multiple elements of interest in geological samples.

Endoscopic type 1 tympanoplasty: comparison of the effects of three different thicknesses grafts.

BACKGROUND: The effects of graft thickness on tympanoplasty is uncertain. OBJECTIVE: To compare the results of endoscopic tympanoplasty using different thicknesses of autologous tissues. METHODS: This retrospective analysis included 186 patients who received type I tympanoplasty, divided into three main groups based of grafting material: perichondrium (A), cartilage-perichondrium (B), or cartilage-perichondrium plus additional perichondrium (C). Group A was subdivided based on whether the placement was inside (A1) or outside (A2) of the malleus. The hearing improvement, graft success rate, and surgery duration were analysed. RESULTS: Statistical analysis showed significant hearing improvement in the three main groups (p < .001); recovery in group A occurred the earliest. Six months postoperatively, group A1 showed significantly greater hearing recovery compared with groups B and C (p < .05). There were no statistical differences the other groups (p > .05) or in the graft success rate among the three main groups (p = .235). The surgery duration of group A was significantly longer than that of groups B and C (p < .001). CONCLUSION AND SIGNIFICANCE: Our results suggest that graft thickness affects hearing recovery; however, graft thickness does not affect the rate of grafting success. Endoscopic transplantation of the perichondrium is more difficult and requires more time.

Elemental Analysis of Solid Food Materials Using a Reliable Laser Ablation Inductively Coupled Plasma Mass Spectrometry Method.

Quantification of trace and minor nutrient elements is crucial for maintaining human health. A reliable laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) method for food materials was developed by combining fine food powder (dm < 3 µm) pellets as the external standard with an average C content as the internal standard (IS). The finer and homogeneous aerosol produced by ablating the fine powder pellets is beneficial for transportation and analyte ionization in ICP, which helps alleviate the matrix effects and improves the analytical precision and accuracy. The average C content is 39.9 ± 1.9% for plant-derived foods (n = 22) and 46.9 ± 1.1% for animal-derived foods (n = 7). The accuracy (recovery, 80-120%) and precision (RSD, 0.5-9.8%) were validated by analyzing a series of food certified reference materials. The high-throughput method is a promising alternative for routine sample analysis in food safety laboratories.

Establishment of sperm associated antigen 6 gene knockout mouse model and its mechanism of deafness.

To investigate the effects of knocking out the Sperm associated antigen6 (Spag6) gene on the auditory system of mice, the heterozygous type Spag6 knockout mouse model built in the previous period was used for mating and breeding, and homozygous type Spag6 gene knockout mouse (Spag-/-), heterozygous type Spag6 gene knockout mouse (Spag+/-) and wild type mouse (Spag+/+) were obtained. PCR technology was used to verify mouse models with different genotypes. After verification, the hearing threshold responses of Spag+/+ and Spag-/- genotype mice were detected. The localization of Spag6 gene in the basal membrane of the cochlea of the inner ear was detected by immunofluorescence staining. The changes of middle ear tissues were observed by H.E. staining sections. The relative expression of Prestin gene and Pgrn gene in different age mice was detected by fluorescence quantitative PCR. The relative expression of Prestin gene was detected by western blot. The results showed that Spag-/- mice had hearing impairment compared with Spag+/+ mice. And Spag6 protein is distributed in different genotypes of mouse hair cells; Spag-/- mice showed otitis media. The expression of Prestin mRNA and protein in Spag-/- mice was significantly higher than that in Spag+/+ mice (P < 0.01). The expression of Pgrn gene in Spag+/+ mice was significantly higher than that in Spag-/- mice (P < 0.05). It indicates that the loss of Spag6 gene would lead to the decline of hearing sense in mice. It is likely that the Spag6 gene could affect hearing by regulating the expression of Prestin gene. And the absence of the Spag6 gene causes otitis media in mice. The results of this study can lay a theoretical foundation for the follow-up studies of Spag6 gene in deafness diseases.

Analysis of rice and wheat flour by particle nebulization ICP-MS.

Analysis of toxic elements in food samples (e.g., rice and wheat) is very important for human health. A direct nebulization of solid particles for inductively coupled plasma (ICP) ionization and subsequent analysis of toxic elements (i.e., As, Cd, Hg, and Pb) by mass spectrometry (MS) was developed. Dried and well-ground food particles (mean size of 0.9-1.0 µm) were stably dispersed in 0.5% polyethylene-imine (PEI) and the particle slurries were analyzed by ICP-MS using aqueous standard calibration. The transportation and ionization behaviors of particles with different particle sizes in ICP-MS were compared with those of aqueous standards containing equivalent concentrations of the analyte. The results indicated that the upper limits of particle sizes for the efficient transportation and complete ionization were 7.5-8.0 µm and 3.3-3.5 µm, respectively. Satisfactory recovery (94-107%), and precision (0.4-6.5%, RSD, n = 3) were verified by analyzing a series of rice and wheat standard reference materials (SRMs). The limits of quantitation (LOQs, 1.1 ng g-1 (Hg) to 3.5 ng g-1 (As)) are compared with the traditional microwave-assisted acid digestion ICP-MS method, however, the analysis throughput of the proposed method is improved by more than 10 times.

Method Development for Direct Multielement Quantification by LA-ICP-MS in Food Samples.

A novel calibration strategy for the accurate determination of essential and toxic elements in both plant-based and animal-based foods was developed by synthesizing spiked agarose gels as matrix-matched external standards and carbon as the internal standard (IS). Aqueous solutions of agarose (4%, m/v) with defined amounts of the analytes were cast on a mold and then dried to form the agarose-gel standards. The spatial distributions of the analytes in the gel were examined using surface- and depth-mapping laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) protocols, and the gel homogeneity was found to be excellent (i.e., relative standard derivation <10%). Recovery of the 19 spiked elements in the gel standards was in the range of 86.9-94.7%. The limits of detection (LODs) ranged from 0.0005 (Rb) to 33.7 µg g-1 (S). Analysis results were in good agreement with certified values for various certified reference materials (CRMs). Furthermore, a porous rubber sample supporter was developed to improve the analysis throughput by about 3-fold.

Method Development for the Determination of Total Fluorine in Foods by Tandem Inductively Coupled Plasma Mass Spectrometry with a Mass-Shift Strategy.

A method for total F determination in food and tea samples based on a mass-shift strategy using tandem inductively coupled plasma quadrupole mass spectrometry (ICP-MS-MS) was developed. This method consists of four steps: (1) conversion of the hardly ionized F atoms to BaF+ via ICP, (2) use of the first quadrupole (Q1, set at 157) to ensure only the m/z 157 ions (i.e., 138Ba19F+, 157Gd+, and 138Ba18OH+) enter the reaction cell (RC), (3) shifting 138Ba19F+ to a new mass 138Ba19F(14NH3)3+ by reacting with NH3 in RC to avoid the interfering ions (i.e., 157Gd+ and 138Ba18OH+), and (4) passing interference-free 138Ba19F(14NH3)3+ to the second quadrupole (Q2, set at 208) for detection by the MS detector. The mass-shift process of the target F (in ICP and RC) expected to follow the path: F + 138Ba+ → 157BaF+ + 3NH3 → 208BaF(NH3)3+, while the reaction pathway of dominant 157Gd+ in RC proposed to 157Gd+ + NH3 → 157Gd14N1H+ + nNH3 → 157Gd14N1H(14N1H3)n+ (n = 0-5). Under the optimized setting of tandem MS (Q1 → Q2 = 157 → 208) and RC reaction gas flow rate (NH3/He = 10:90, 8.0 mL min-1), the background equivalent concentrations (BECs) and limits of detection (LODs) were 0.021 and 0.022 µg mL-1, respectively. The calibration curve was linear in the range between 0.1 and 10 µg mL-1, with a correlation coefficient of R2 = 0.9999. The results obtained for 14 different food-related standard reference materials (SRMs) were in good agreement with the certified values on a 95% confidence level. The proposed method was then employed to evaluate the F contents of 13 branded tea samples. The total F concentrations ranged from 39.2 to 93.2 µg g-1. The tea infusions contained F between 23.5 and 85.4 µg g-1, with an extraction efficiency of 56.0-91.6%, and the water-soluble F contents of a Pu'er brick tea were 58.7, 21.4, 3.82, and 1.41 µg g-1 for filtrates 1, 2, 3, and 4, respectively.

Clinical relationship between auditory neuropathy and nervous system diseases.

OBJECTIVE: To explore the clinical relationship between auditory neuropathy (AN) and nervous system diseases. METHODS: A total of 134 AN patients who were treated in our hospital from December 2011 to April 2016 were selected. Then 120 cases (240 ears) with complete data of pure tone audiometry and acoustic immittance test were selected as an AN1 group, which was compared with 30 patients (49 ears) with general sensorineural hearing loss (SHL) in regard to the results of pure tone audiometry and acoustic immittance test. On the other hand, 79 cases (158 ears) of the 134 patients with complete data of DP otoacoustic emission test were selected as an AN2 group, which was compared with 30 normal subjects (60 ears) regarding the results of DP otoacoustic emission test. RESULTS: Increases in the pure-tone hearing threshold by air conduction of AN1 group significantly exceeded those of SHL group at 0.125 and 0.25 kHz (low frequency) (P<0.05). The former group had significantly lower values at 1.0, 2.0 kHz (moderate frequency) and 4.0, 8.0 kHz (high frequency) (P<0.05). Of 134 patients, 14 (19 ears) had evoked V wave upon auditory brainstem response, whereas no waves after I wave were evoked in other tested ears. Distortion product (DP) otoacoustic emissions could all be evoked. AN2 group had significantly higher amplitudes of DP-gram than those of normal control group at 0.5 and 0.7 kHz (low frequency) (P<0.05). Except for three cases of unsteady walking and 10 of dizziness, others did not suffer from typical symptoms of vertigo attack. As to caloric test-induced electronystagmograms, there were 30 bilaterally normal cases (75.0%), one case of left-side semicircular canal paresis (25%) and nine cases of bilateral semicircular canal paresis (22.5%). Four patients with other nervous system diseases were complicated with AN. Other nervous system disorders included three cases of optic nerve atrophy and 7 of lower limb nerve damage. CONCLUSION: According to characteristic hearing dysfunction, AN may occur in the afferent pathway of acoustic nerve, probably accompanied by the pathological changes of efferent nerve in the olivocochlear system inside the brainstem.

Evaluation of flow injection-solution cathode glow discharge-atomic emission spectrometry for the determination of major elements in brines.

A new method for the determination of major metal elements in high salinity brines was developed by solution cathode glow discharge (SCGD) with flow injection analysis (FIA). The matrix interferences of major cations and anions in brines have been evaluated. It was found that high concentration of Na(+) and K(+) could interfere each other, K(+) at a concentration of 400mgL(-1) enhanced the signal intensity of Na(+) more than 20%. The effect of the anions was observed and it was noted that the signal intensity of both Ca(2+) and Mg(2+) were suppressed significantly when the SO4(2-) reached 100mgL(-1). It was demonstrated that some low molecular weight organic substances such as formic acid, glycerol and ascorbic acid could eliminate interference of SO4(2-) even with volume percentages of 0.5%. Under the optimized condition, the proposed FIA-SCGD can determine K, Na, Ca and Mg with the limits of detection of 0.49 (K), 0.14 (Na), 11 (Ca) and 5.5 (Mg) ngmL(-1). The proposed method has been successfully applied to the analysis of 5 salt lake samples and compared with those obtained with inductively coupled plasma atomic emission spectrometry (ICP-AES). The advantages of small size, low energy consumption, good stability and repeatability indicated that the SCGD is promising for the determination of major ions in brine samples.

Simultaneous Determination of Size and Quantification of Gold Nanoparticles by Direct Coupling Thin layer Chromatography with Catalyzed Luminol Chemiluminescence.

The increasing use of metal-based nanoparticle products has raised concerns in particular for the aquatic environment and thus the quantification of such nanomaterials released from products should be determined to assess their environmental risks. In this study, a simple, rapid and sensitive method for the determination of size and mass concentration of gold nanoparticles (AuNPs) in aqueous suspension was established by direct coupling of thin layer chromatography (TLC) with catalyzed luminol-H2O2 chemiluminescence (CL) detection. For this purpose, a moving stage was constructed to scan the chemiluminescence signal from TLC separated AuNPs. The proposed TLC-CL method allows the quantification of differently sized AuNPs (13 nm, 41 nm and 100 nm) contained in a mixture. Various experimental parameters affecting the characterization of AuNPs, such as the concentration of H2O2, the concentration and pH of the luminol solution, and the size of the spectrometer aperture were investigated. Under optimal conditions, the detection limits for AuNP size fractions of 13 nm, 41 nm and 100 nm were 38.4 µg L(-1), 35.9 µg L(-1) and 39.6 µg L(-1), with repeatabilities (RSD, n = 7) of 7.3%, 6.9% and 8.1% respectively for 10 mg L(-1) samples. The proposed method was successfully applied to the characterization of AuNP size and concentration in aqueous test samples.

Antibiotic and heavy-metal resistance of Vibrio parahaemolyticus isolated from fresh shrimps in Shanghai fish markets, China.

Vibrio parahaemolyticus is a causative agent of human serious seafood-borne gastroenteritis disease and even death. Shrimps, often eaten raw or undercooked, are an important reservoir of the bacterium. In this study, we isolated and characterized a total of 400 V. parahaemolyticus strains from commonly consumed fresh shrimps (Litopenaeus vannamei, Macrobrachium rosenbergii, Penaeus monodon, and Exopalaemon carinicauda) in Shanghai fish markets, China in 2013-2014. The results revealed an extremely low occurrence of pathogenic V. parahaemolyticus carrying two major toxic genes (tdh and trh, 0.0 and 0.5 %). However, high incidences of antibiotic resistance were observed among the strains against ampicillin (99 %), streptomycin (45.25 %), rifampicin (38.25 %), and spectinomycin (25.50 %). Approximately 24 % of the strains derived from the P. monodon sample displayed multidrug resistant (MDR) phenotypes, followed by 19, 12, and 6 % from the E. carinicauda, L. vannamei, and M. rosenbergii samples, respectively. Moreover, tolerance to heavy metals of Cr(3+) and Zn(2+) was observed in 90 antibiotic resistant strains, the majority of which also displayed resistance to Cu(2+) (93.3 %), Pb(2+) (87.8 %), and Cd(2+)(73.3 %). The pulsed-field gel electrophoresis (PFGE)-based genotyping of these strains revealed a total of 71 distinct pulsotypes, demonstrating a large degree of genomic variation among the isolates. The wide distribution of MDR and heavy-metal resistance isolates in the PFGE clusters suggested the co-existence of a number of resistant determinants in V. parahaemolyticus population in the detected samples. This study provided data in support of aquatic animal health management and food safety risk assessment in aquaculture industry.

Quantitative Characterization of Gold Nanoparticles by Coupling Thin Layer Chromatography with Laser Ablation Inductively Coupled Plasma Mass Spectrometry.

Metal nanoparticles (NPs) determination has recently attracted considerable attention because of the continuing boom of nanotechnology. In this study, a novel method for separation and quantitative characterization of NPs in aqueous suspension was established by coupling thin layer chromatography (TLC) with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Gold nanoparticles (AuNPs) of various sizes were used as the model system. It was demonstrated that TLC not only allowed separation of gold nanoparticles from ionic gold species by using acetyl acetone/butyl alcohol/triethylamine (6:3:1, v/v) as the mobile phase, but it also achieved the separation of differently sized gold nanoparticles (13, 34, and 47 nm) by using phosphate buffer (0.2 M, pH = 6.8), Triton X-114 (0.4%, w/v), and EDTA (10 mM) as the mobile phase. Various experimental parameters that affecting TLC separation of AuNPs, such as the pH of the phosphate buffer, the coating of AuNPs, the concentrations of EDTA and Triton X-114, were investigated and optimized. It was found that separations of AuNPs by TLC displayed size dependent retention behavior with good reproducibility, and the retardation factors (R(f) value) increased linearly with decreasing nanoparticle size. The analytical performance of the present method was evaluated under optimized conditions. The limits of detection were in the tens of pg range, and repeatability (RSD, n = 7) was 6.3%, 5.9%, and 8.3% for 30 ng of 13 nm AuNPs, 34 nm AuNPs, and 47 nm AuNPs, respectively. The developed TLC-LA-ICP-MS method has also been applied to the analysis of spiked AuNPs in lake water, river water, and tap water samples.

Elemental determination of microsamples by liquid film dielectric barrier discharge atomic emission spectrometry.

In this study, a new liquid-film dielectric barrier discharge (LFDBD) atomic emission source was developed for microsample elemental determination. It consists of a copper electrode, a tungsten wire electrode, and a piece of glass slide between them, which serves as the dielectric barrier as well as the sample plate. The sample solution with 1 mol L(-1) nitric acid, when deposited onto the surface of the glass slide, forms a thin liquid film. The plasma is generated between the tip of the tungsten wire electrode and the liquid film surface when alternating-current (ac) high voltage (peak voltage ~3.7 kV, frequency ~30 kHz) is applied on the electrodes. Qualitative and quantitative determinations of metal ions in the sample solution were achieved by atomic emission measurements in the plasma and were demonstrated in this study with elements Na, K, Cu, Zn, and Cd. Detection limits were in the range from 0.6 ng (7 µg L(-1)) for Na to 6 ng (79 µg L(-1)) for Zn. Repeatability, expressed as relative standard deviation from seven repetitive analyses of samples with analyte concentrations at 1 mg L(-1), varied from 2.1% to 4.4%. Compared with other liquid discharge systems that operate at atmospheric pressure, the current system offers several advantages: First, it eliminates the use of a sample flow system (e.g., syringe or peristaltic pump); instead, a small aliquot of sample is directly pipetted onto the glass slide for analysis. Second, it is a microanalysis system and requires sample volume ≤80 µL, a benefit when a limited amount of sample is available. Third, because the sample is applied in aliquot, there is no washout time, and the analysis can be easily extended to sample array for high-throughput analysis. The proposed LFDBD is promising for in-field elemental determination because of its simplicity, cost effectiveness, low power supply, and no inert gas requirement.

Solution cathode glow discharge induced vapor generation of mercury and its application to mercury speciation by high performance liquid chromatography-atomic fluorescence spectrometry.

A novel solution cathode glow discharge (SCGD) induced vapor generation was developed as interface to on-line couple high-performance liquid chromatography (HPLC) with atomic fluorescence spectrometry (AFS) for the speciation of inorganic mercury (Hg(2+)), methyl-mercury (MeHg) and ethyl-mercury (EtHg). The decomposition of organic mercury species and the reduction of Hg(2+) could be completed in one step with this proposed SCGD induced vapor generation system. The vapor generation is extremely rapid and therefore is easy to couple with flow injection (FI) and HPLC. Compared with the conventional HPLC-CV-AFS hyphenated systems, the proposed HPLC-SCGD-AFS system is very simple in operation and eliminates auxiliary redox reagents. Parameters influencing mercury determination were optimized, such as concentration of formic acid, discharge current and argon flow rate. The method detection limits for HPLC-SCGD-AFS system were 0.67 µg L(-1) for Hg(2+), 0.55 µg L(-1) for MeHg and 1.19 µg L(-1) for EtHg, respectively. The developed method was validated by determination of certified reference material (GBW 10029, tuna fish) and was further applied for the determination of mercury in biological samples.