Octopole Reaction Cell Research Articles

High Performance Liquid Chromatography-Determination of Different Speciations of Arsenic in Cosmetics by Inductively Coupled Plasma Mass Spectrometry

There is a way to determine four arsenic speciations simultaneously in cosmetic by using liquid chromatography (HPLC) with inductively coupled plasma mass spectrometer (ICP-MS). After being extracted by phosphoric acid solution, the samples were separated by PRP-X100 anion chromatographic column. The mobile phase was aqueous solution (pH=6.0) containing 1% methanol (V/V), 2.0 mmol/L NaH2PO4 and 0.2 mmol/L ethylene diamine tetraacetic acid (EDTA). The octopole reaction cell was adopted to eliminate mass spectrum interferences. The separation of AsIII､DMA､MMA and AsV was achieved within 12 min with flow rate of 1.00 mL/min and sample size of 100 μL. The recovery rates of AsIII, DMA, MMA and As Vranged from 80.6% to 107.2% and the relative standard deviations were less than 6.24% when the spiked amount was 0.10∼ 1.00 μg in different kinds of cosmetic samples. The developed method has the advantage of simplicity, sensitivity and good reproducibility, and can be used for the determination of arsenic speciations simultaneously in cosmetics.

Accurate Measurement of Selenoproteins with Affinity HPLC‐ICP/MS Using D2 as a Collision Gas

Accurate quantitative measurement of selenoproteins GPx, SelP, and SeAlb in blood serum was achieved by using affinity HPLC‐ICP/MS with Post Column Isotope Dilution (PCID). D2 was used as a collision gas to avoid BrH+ interference that arises from the combination of matrix Br and the H2 collision gas normally used in octopole reaction cell (ORC) ICP/MS. The advantages of using D2 were to be free from isobaric interference, and the use of the ratio of 78Se/80Se which has the higher abundances for higher precision in ID techniques. Ammonium formate, rather than ammonium acetate or ammonium nitrate, was selected as an eluent for affinity chromatography to accomplish an efficient separation of the three selenoproteins and to provide the least baseline change during the gradient elution. The baseline change in PCID during the peak elution was compensated by active background subtraction. The accuracy was verified against the reference blood serum BCR 639 (133 ± 12 ng/g) to give 130.1 ± 6.4 ng/g (97.7% accuracy) with 4% RSD. The distributions of three proteins were 41%, 48%, and 11% for GPx, SelP, and SeAlb, respectively. The abstract should briefly state the problem or purpose of the research, indicate the methodology used, summarize the principal findings and major conclusions.

The Use of D2 Collision Gas in Isotope Dilution for the Analysis of Se with Octopole Reaction Cell Inductively Coupled Plasma‐Mass Spectrometry

D2 was used as a collision/reaction cell gas in Ar inductively coupled plasma‐mass spectrometry for the analysis of selenium with an isotope dilution method. In conventional H2 collision gas, 80[BrH] was generated by the reaction of collision gas with Br in matrix. The use of D2 could generate 81[BrD] instead of 80[BrH], making it possible for the use of m/z 80, which has the highest abundance among Se isotopes. Two collision gases, H2 and D2, were compared with each other for the isotope spikes of 76Se, 77Se, and 78Se. For an inorganic selenium standard, both gases showed good results of 99% accuracy and below 1% Relative Standard Deviation (RSD). However, for complex‐matrix samples, the results were different. For NIST SRM 1567b (wheat flour), which had a relatively simple matrix, accuracy and precision were similar for both gases. For KRISS CRM 108‐04‐001(oyster) and NIST SRM 2976 (mussel), which had a relatively high level of Br matrix, deuterium gas showed better accuracy and precision. For H2, 77Se showed the highest accuracy (98.4% recovery) but low precision (3.24% RSD). For deuterium, all three spikes showed good results, 98% average recovery and less than 1% RSD. The use of D2 collision gas demonstrates that it is effective for the accurate determination of Se, even for a complex matrix.

Confirmation of40Ar+related product ions in the octopole reaction cell of an ICP-QMS/QMS with18O2enriched oxygen as the reaction cell gas

40Ar+ related product ions in an octopole reaction cell (ORC) were observed with an inductively coupled plasma tandem quadrupole mass spectrometer (ICP-QMS/QMS). In order to simplify the ion composition of the plasma, the carrier gas was directly connected to the torch injector, i.e. without introduction of the sample solution. The m/z of the first QMS was set to 40 permitting the passage of 40Ar+. Isotope enriched oxygen gas (18O2) was used as the reaction gas in order to separate the spectra of O3+ and Ar2O2+. The intensities of the ions produced in the ORC were measured by the second QMS. As the products of the reactions among 40Ar+ ions and 18O2 molecules in the ORC, the following ions were observed: 18O+, 18O2+, 18O3+, 18O4+, 40Ar18O+, 40Ar18O2+, 40Ar218O2+, and 40Ar18O22+. At a reaction gas flow rate of 0.3 mL min−1, the ionic species with the highest signal intensity was 18O2+, followed by 40Ar+ and 18O+. The maximum signal intensities of different product ions were obtained at different flow rates of the reaction gas. A lower flow rate of the reaction gas benefited the production of 40Ar18O+ and 18O3+, while a higher flow rate of the reaction gas benefited the production of 40Ar18O2+ and 40Ar218O2+. The maximum transfer efficiency from 40Ar+ to the resulting ionic species was 91%, 2.0%, and 0.12% for 18O2+, 18O+, and 40Ar18O+, respectively. The maximum transfer efficiency to the other investigated ionic species was less than 0.023%. By using 18O2 as the reaction gas, the mechanisms of 40Ar+ resulted ionic species interfering with the measurement of 32S16O+ were confirmed. The results showed that the contributions of 16O3+ and 40Ar2O2+ were almost equivalent to each other.

Interference-free determination of ultra-trace concentrations of arsenic and selenium using methyl fluoride as a reaction gas in ICP-MS/MS.

Interference-free conditions, allowing straightforward As and Se determination, can be obtained by using CH3F (a mixture of 10% CH3F and 90% He) as a reaction gas in tandem ICP-mass spectrometry (ICP-MS/MS). Both target elements react via CH3F addition and subsequent HF elimination, rendering AsCH2 (+) and SeCH2 (+) the respective favored reaction product ions. Instrumental limits of detection were 0.2 ng L(-1) for As and below 10 ng L(-1) for Se, using either (77)Se, (78)Se, or (80)Se. Neither addition of carbon to the solutions, nor admixing of additional He into the octopole reaction cell resulted in a further improvement of the LoDs, despite the increase in analyte signal intensity. By using synthetic matrices, containing elements giving rise to ions interfering at either the original mass-to-charge ratios or those of the reaction products, absence of spectral overlap could be demonstrated. This conclusion was corroborated by successful As and Se determination in a collection of reference materials from plant, animal, or environmental origin, displaying a considerable range of As and Se contents. These accurate results were obtained via external calibration using Te as an internal standard. The high efficiency reaction between As and CH3F and the possibility to use the major isotope of Se provides enhanced detection power versus other techniques, such as sector-field ICP-mass spectrometry, while the possibility to monitor at least three Se isotopes interference-free also enables isotopic analysis.

Potential of methyl fluoride as a universal reaction gas to overcome spectral interference in the determination of ultratrace concentrations of metals in biofluids using inductively coupled plasma-tandem mass spectrometry.

Methyl fluoride (a mixture of 10% CH3F and 90% of He) was evaluated as a reaction gas in inductively coupled plasma-tandem mass spectrometry (ICPMS/MS) in the context of the determination of ultratrace concentrations of medically relevant metals (Al, Co, Cr, Mn, Ni, Ti, and V) in blood serum and urine. Via product ion scanning, whereby only ions of the mass-to-charge ratio of the target nuclide were admitted into the octopole reaction cell, the various reaction product ions formed for each of the target elements were identified at different CH3F gas flow rates. Limits of detection (LODs) and of quantification (LOQs) and linearity of the calibration curve were documented under (i) optimized ICPMS/MS conditions for single-element monitoring and (ii) compromise conditions, allowing for multielement determination. Even under compromise settings, instrumental LODs were below 10 ng/L for all target elements, while the use of CH3F provided interference-free conditions for their determination in the biofluids of interest. Quantitative data obtained for Seronorm blood serum and urine reference materials were in excellent agreement with the corresponding reference values and/or results obtained using double-focusing sector-field ICPMS (for those elements for which no certified values were available or that were affected during reconstitution), proving the potential of this reaction gas for multielement ultratrace analysis via ICPMS/MS.

Multielement analysis of human seminal plasma by octopole reaction cell ICP-MS

The method of simple dilution of seminal plasma allowed sufficiently sensitive and reproducible simultaneous measurement of 20 elements in seminal plasma by ICP-MS.

Evolution of metallotionein isoforms complexes in hepatic cells of Mus musculus along cadmium exposure

Characterization of Cd-binding proteins has great analytical interest due to the high toxicity of Cd to living organisms. Metallothioneins (MTs), as Cd(II)-binding proteins are of increasing interest, since they form very stable Cd chelates and are involved in many detoxification processes. In this work, inductively coupled plasma octopole reaction cell mass spectrometry and nanospray ionization time-of-flight mass spectrometry were used in parallel and combined with two-dimensional chromatography: size exclusion followed by reversed-phase high performance liquid chromatography, to study metal complexes of MT isoforms produced in hepatic cytosols of Mus musculus during exposure experiments to Cd. Exposure experiments were carried out by subcutaneous injection of a growing dose of the toxic element ranging from 0.1 to 1.0mg of Cd per kg of body weight per day during 10days. A control group and three exposure groups at days 2, 6 and 10 of exposure were studied, and different cadmium, copper and zinc complexes with MTs isoforms were isolated and characterized from the two most exposed groups. The results allow gaining insight into the mechanisms involved in metal detoxification by MTs, showing the changes in the stoichiometry of metal complexes-MTs along cadmium exposure.

A Combined Zinc/Cadmium Sensor and Zinc/Cadmium Export Regulator in a Heavy Metal Pump

Heavy metal pumps (P1B-ATPases) are important for cellular heavy metal homeostasis. AtHMA4, an Arabidopsis thaliana heavy metal pump of importance for plant Zn(2+) nutrition, has an extended C-terminal domain containing 13 cysteine pairs and a terminal stretch of 11 histidines. Using a novel size-exclusion chromatography, inductively coupled plasma mass spectrometry approach we report that the C-terminal domain of AtHMA4 is a high affinity Zn(2+) and Cd(2+) chelator with capacity to bind 10 Zn(2+) ions per C terminus. When AtHMA4 is expressed in a Zn(2+)-sensitive zrc1 cot1 yeast strain, sequential removal of the histidine stretch and the cysteine pairs confers a gradual increase in Zn(2+) and Cd(2+) tolerance and lowered Zn(2+) and Cd(2+) content of transformed yeast cells. We conclude that the C-terminal domain of AtHMA4 serves a dual role as Zn(2+) and Cd(2+) chelator (sensor) and as a regulator of the efficiency of Zn(2+) and Cd(2+) export. The identification of a post-translational handle on Zn(2+) and Cd(2+) transport efficiency opens new perspectives for regulation of Zn(2+) nutrition and tolerance in eukaryotes.

Determination of Ge, As, Se and Te in Silicate Samples Using Isotope Dilution‐Internal Standardisation Octopole Reaction Cell ICP‐QMS by Normal Sample Nebulisation

A method for the determination of Ge, As, Se and Te in silicate samples using isotope dilution‐internal standardisation (ID‐IS) octopole reaction cell (ORC) ICP‐QMS by normal sample nebulisation was developed. The method does not involve either hydride generation or ion exchange. Germanium, Se and Te were determined by isotope dilution (ID), and As was determined by ID‐IS. A silicate sample with an added Ge‐Se‐Te spike was digested with an HF‐HNO3‐HBr mixture, dried, re‐dissolved with HF and the supernatant liquid was directly aspirated into an ORC‐ICP‐QMS instrument with He or H2 gas. No matrix effects were observed down to a dilution factor (DF) of ∼ 70 for Ge, Se and Te and DF of ∼ 1000 for As, which resulted in 3s detection limits in silicates of 2, 1, 0.1 and 4 ng g−1, respectively. Advantages of the method are the simple sample introduction as well as a capability of determining S, Ti, Zr, Nb, Mo, Sn, Sb, Hf and Ta by ID‐IS‐ICP‐QMS/SFMS from the same solution. Furthermore, the total sample solution consumption was only 0.253 ml with DF = 2000. Therefore, only a 0.13 mg test portion was required. To demonstrate the applicability of this technique, Ge, As, Se and Te in eight silicate reference materials were determined, as well as S, Ti, Zr, Nb, Mo, Sn, Sb, Hf and Ta in four carbonaceous chondrites.

Simultaneous iron, zinc, sulfur and phosphorus speciation analysis of barley grain tissues using SEC-ICP-MS and IP-ICP-MS

The increasing prevalence of iron (Fe) and zinc (Zn) deficiencies in human populations worldwide has stressed the need for more information about the distribution and chemical speciation of these elements in cereal products. In order to investigate these aspects, barley grains were fractionated into awns, embryo, bran and endosperm and analysed for Fe and Zn. Simultaneously, phosphorus (P) and sulfur (S) were determined since these elements are major constituents of phytic acid and proteins, respectively, compounds which are potentially involved in Fe and Zn binding. A novel analytical method was developed in which oxygen was added to the octopole reaction cell of the ICP-MS. This approach greatly improved the sensitivity of sulfur, measured as (48)SO(+). Simultaneously, Fe was measured as (72)FeO(+), P as (47)PO(+), and Zn as (66)Zn(+), enabling sensitive and simultaneous analysis of these four elements. The highest concentrations of Zn, Fe, S and P were found in the bran and embryo fractions. Further analysis of the embryo using SEC-ICP-MS revealed that the speciation of Fe and Zn differed. The majority of Fe co-eluted with P as a species with the apparent mass of 12.3 kDa, whereas the majority of Zn co-eluted with S as a 3 kDa species, devoid of any co-eluting P. Subsequent ion pairing chromatography of the Fe/P peak showed that phytic acid (myo-inositol-1,2,3,4,5,6-hexakisphosphate: IP(6)) was the main Fe binding ligand, with the stoichiometry Fe(4)(IP(6))(18). When incubating the embryo tissue with phytase, the enzyme responsible for degradation of phytic acid, the extraction efficiency of both Fe and P was doubled, whereas that of Zn and S was unaffected. Protein degradation on the other hand, using protease XIV, boosted the extraction of Zn and S, but not that of Fe and P. It is concluded that Fe and Zn have a different speciation in cereal grain tissues; Zn appears to be mainly bound to peptides, while Fe is mainly associated with phytic acid.

Speciation of manganese binding to biomolecules in pine nuts (Pinus pinea) by two‐dimensional liquid chromatography coupled to ultraviolet and inductively coupled plasma mass spectrometry detectors followed by identification by electrospray ionization mass spectrometry

Advances in analytical methodology for speciation of manganese in pine nuts are presented in this work. The approach is based on the use of orthogonal chromatographic systems, namely size-exclusion chromatography (SEC) of the extracts and strong anion exchange (IEC) of the fractions collected by the first column. In both columns, manganese elution is first monitored by a quadrupole inductively coupled plasma mass spectrometry (ICP-MS) instrument equipped with an octopole reaction cell and an ultraviolet (UV) detector. SEC is performed by using two columns covering the molecular weight range from <10 to 70 kDa that allows an initial screening of the molecular weight of the Mn species. The higher resolution capability of the low molecular weight range column is the reason to use the latter for further experiments. The fraction from SEC-ICP-MS in which Mn is present at highest concentration is submitted to IEC-ICP-MS allowing Mn-citrate and MnCl(2) identification by retention time matching with standards. The concentration of these species is estimated to be 75 and 125 microg kg(-1) (as Mn), respectively, in the pine nuts samples and the presence of Mn-citrate is confirmed by nanoelectrospray ionization quadrupole time-of-flight mass spectrometry (nESI-QqTOF-MS). In the same fraction, a third Mn-containing peak is detected in the IEC-UV-ICP-MS chromatogram. This peak corresponds to a protein containing Mn that was later submitted to a tryptic digestion and analyzed by nESI-QqTOF. The MS/MS data of a doubly charged peptide are used to obtain the sequence of the protein with the Mascot search engine. The peak turned out to be isocitrate dehydrogenase, a protein commonly associated with Mn.

Development of a new method for sulfide determination by vapor generator–inductively coupled plasma–mass spectrometry

A new sensitive methodology for the determination of total reduced sulfur species in natural waters and acid volatile sulfides in sediments at low levels (μg L − 1 ) is described. Reduced sulfur species were separated from the water matrix in the form of H 2S after reaction with hydrochloric acid in a commercial vapor generator coupled to an inductively coupled plasma quadrupole mass spectrometer (VG–ICP–QMS) equipped with a reaction cell. The method avoided the effect of polyatomic isobaric interferences at m/z 32 caused by 16O 16O + and 14N 18O + through the elimination of the aqueous matrix, a source of oxygen. By introducing a mixture of helium and hydrogen gases into the octopole reaction cell, a series of ion-molecule reactions were induced to reduce the interfering polyatomic species. Operating conditions of the octopole reaction cell system and the analyzer were optimized to get the best signal to background ratio for 32S; a full factorial 2 3 experimental design was developed in order to evaluate which variables had a significant effect and a simplex methodology was applied to find the optimum conditions for the variables. The new method was evaluated by comparison to the standard potentiometric method. The analytical methodology developed was applied to the analysis of reduced sulfur species in natural waters and acid volatile sulfides in sea sediments.

Reversed phase ion-pairing HPLC-ICP-MS for analysis of organophosphorus chemical warfare agent degradation products

The separation and analysis of three organophosphorus chemical warfare degradation products is described. Ethyl methylphosphonic acid (EMPA, the major hydrolysis product of VX), isopropyl methylphosphonic acid (IMPA, the major hydrolysis product of Sarin (GB)), and methylphosphonic acid (MPA, the final hydrolysis product of both) were the analytes and were separated by reversed phase ion-pairing high-performance liquid chromatography (RP-IP-HPLC) with the use of myristyl trimethylammonium bromide as ion-pairing reagent and an ammonium acetate–acetic acid buffer system (pH 4.85). An Agilent 7500ce inductively coupled plasma mass spectrometer (ICP-MS) equipped with collision/reaction cell technology was coupled to the chromatographic system for detection of 31P and 47PO+. Historically, ICP-MS detection of phosphorus has been limited due to its high first ionization potential (10.5 eV) and the presence of severe nitrogen polyatomic interferences (such as 14N16O1H+ and 15N16O+) overlapping its only isotope at m/z = 31. Implementation of an octopole reaction cell with helium as the cell gas allowed for removal of the nitrogen polyatomic interferences and reduction of background signal. Detection limits for EMPA, IMPA, and MPA were found to be 263, 183 and 139 pg mL−1, respectively, with separation in less than 15 min. The developed method was successfully applied to the analysis of spiked environmental water and soil samples.

Validation of LA-ICP-MS fluid inclusion analysis with synthetic fluid inclusions

Laser ablation—inductively coupled plasma—mass spectrometry (LA-ICP-MS) has become recognized as a sensitive, efficient, and cost-effective approach to measuring the major-, minor-, and trace-solute compositions of individual fluid inclusions in minerals. As a prerequisite for the routine analysis of natural inclusions in our laboratory, the precision and accuracy of the technique was assessed using sets of multi-element synthetic fluid inclusions. Five multi-element standard solutions were prepared, and incorporated as fluid inclusions in quartz crystals at 750 °C and 7 kbar. Fluid inclusions were ablated with a 193 nm ArF excimer laser and analyzed with a quadrupole ICP-MS, equipped with an octopole reaction cell for the removal of Ar-based interferences. The internal standard used in all cases was Na. Analytical precision for K, Rb, and Cs is typically better than 15% RSD, whereas Li, Mg, Ca, Sr, Ba, Mn, Fe, Cu, Zn, and Cl analyses are typically reproducible within 30% RSD. Measured concentrations approximate a Gaussian distribution, suggesting that analytical errors are random. Analyses for most elements are accurate within 15%. Limits of detection vary widely according to inclusion volume, but are 1 to 100 μfor most elements. These figures of merit are in excellent agreement with previous studies. We also demonstrate that, over the range investigated, precision and accuracy are insensitive to inclusion size and depth. Finally, the combination of our LA-ICP-MS analyses with microthermometric data shows that charge-balancing to NaCl-H2O equivalent chloride molality is the most valid approach to LA-ICP-MS data reduction, where chloride-dominated fluid inclusions are concerned.

Effects of deuterium in octopole reaction and collision cell ICP-MS on detection of selenium in extracellular fluids

Inductively coupled plasma-mass spectrometry (ICP-MS) equipped with a reaction/collision cell has been successfully used for dissociating polyatomic interferences. Hydrogen (H 2) is one of the most effective and frequently used reaction/collision gases. However, the H 2 reaction produces interference in the detection of selenium (Se) in bromine (Br)-containing samples, such as extracellular fluids. In this study, deuterium (D 2) was evaluated for possible use as a reaction gas instead of H 2. Although Se concentration in serum and urine was over-estimated in the H 2 reaction mode, it was determined accurately in the D 2 one. In speciation analyses, the background counts at m/ z 77, 78 and 80 were reduced and the signal-to-noise (S/N) ratios were improved by either the H 2 or the D 2 reaction. The 79Br 1H + and 81Br 1H + interferences appearing at m/ z 80 and 82, respectively, were decreased by changing from the H 2 reaction mode to the D 2 one. Thus, D 2 was effective in dissociating polyatomic interferences and removing Br interferences during Se determination and speciation, suggesting that the D 2 reaction mode is useful for selenometallomics, particularly in samples containing Br, such as serum, urine and cell culture medium.

Determination of essential and toxic total elements in premature human milk by inductively coupled plasma mass spectrometry (ICP-ORC-MS), using an octopole reaction cell

The analytical potential of a quadrupole ICP-MS instrument equipped with an octopole reaction cell for the multielemental determination of essential (Cr, Mn, Fe, Co, Cu, Zn, Se and I) and toxic (Al, Cd and Pb) elements in whole premature breast human milk and premature infant formulae was demonstrated. Milk samples were digested using a microwave assisted digestion method in order to destroy the organic matrix. Different parameters affecting the octopole reaction cell were optimised in order to minimize/remove polyatomic interferences caused by argide species from the ICP. The accuracy of the proposed method was tested by analysing a milk powder reference material (BCR 063R) with satisfactory results. The detection limits in a synthetic matrix obtained using a collision cell ranged from 0.5 ng g−1 to 11 ng g−1 for the elements under study. After validation the method was applied to the multielemental analysis of premature human milk samples (after 28–32 gestational weeks) at three different lactating stages during the first month after birthday, and to formula milks commercially available for premature newborns. Results of total concentrations of the above mentioned elements in the two sample types compared here (human milk and formula milk) are discussed. Important differences between human and formula milk in their respective contents of essential elements are shown and the nutritional significance of such differences is highlighted.

Multielemental distribution patterns in premature human milk whey and pre-term formula milk whey by size exclusion chromatography coupled to inductively coupled plasma mass spectrometry with octopole reaction cell

Size exclusion chromatography (SEC), carried out on a Superdex 200 column, has been coupled on line to a quadrupole ICP-MS instrument, equipped with an octopole reaction cell (ORC), for the multielemental speciation of several essential (P, S, Cr, Mn, Fe, Co, Cu, Zn, Br, Se and I) and toxic elements (such as Al) in premature human breast milk whey and premature infant formulae. Human milk samples were centrifuged at 31000g to obtain the milk whey. A SEC-ICP-(ORC)MS hyphenated technique was optimised and then applied to the multielemental fractionation of such elements in premature (after 28–32 gestational weeks) human milk whey at four different lactating stages, covering the first month after birth (namely: colostrum, 6th day, 14th day and 28th day milks after delivery). Similarly, the technique was also applied to essential and toxic elements fractionation in several formula milks, commercially available for feeding of premature newborns. Results of distribution patterns of the above mentioned elements in the two sample types under study (human and formula milks) are discussed. Important differences in trace element speciation between premature human and formula milks have been demonstrated for many essential elements (e.g. Cu, Fe and Zn). The nutritional significance and practical implications of such differences is highlighted from the point of view of formula milks production for premature babies.

Determination of sulfur and selected trace elements in metallothionein-like proteins using capillary electrophoresis hyphenated to inductively coupled plasma mass spectrometry with an octopole reaction cell.

The determination of sulfur in biologically relevant samples such as metalloproteins is described. The analytical methodology used is based on robust on-line coupling between capillary electrophoresis (CE) and octopole reaction cell inductively-coupled plasma mass spectrometry (ORC-ICP-MS). Polyatomic ions that form in the plasma and interfere with the determination of S at mass 32 are minimised by addition of xenon to the collision cell. The method has been applied to the separation and simultaneous element-specific detection of sulfur, cadmium, copper, and zinc in commercially available metallothionein preparations (MT) and metallothionein-like proteins (MLP) extracted from liver samples of bream ( Abramis brama L.) caught in the river Elbe, Germany. Instrumental detection limits have been calculated according to the German standard procedure DIN 32645 for the determination of sulfur and some simultaneously measured trace elements in aqueous solution. For sulfur detection limits down to 1.3 microg L(-1) ((34)S) and 3.2 microg L(-1) ((32)S) were derived. For the other trace elements determined simultaneously detection limits ranging from 300 ng L(-1) ((58)Ni) to 500 ng L(-1) ((66)Zn, (55)Mn) were achieved. For quantification of sulfur and cadmium in a commercially available MT preparation under hyphenated conditions the use of external calibration is suggested. Finally, the need for proper sample-preparation technique will be discussed.

Determination of phosphorus in phosphorylated deoxyribonucleotides using capillary electrophoresis and high performance liquid chromatography hyphenated to inductively coupled plasma mass spectrometry with an octopole reaction cell

The determination of phosphorus in a biologically relevant sample matrix such as DNA is described. The analytical methodology used is based on a robust on-line coupling of capillary electrophoresis (CE) or high performance liquid chromatography (HPLC) with inductively coupled plasma mass spectrometry, equipped with an octopole reaction system (ORS-ICP-MS). Polyatomic ions formed in the plasma and the interface region of the ICP-MS that interfere with the determination of P at mass 31 were minimised by the addition of helium to the collision cell. Instrumental detection limits of 125 ng L−1 for 31P, and in the range of 18 to 49 ng L−1 for the other trace elements, were achieved under the conditions described. In order to demonstrate the high separation and detection efficiency of the system, the method developed has been applied to the element specific detection of phosphorus in monophosphorylated deoxynucleotides and to enzymatically digested calf thymus DNA after CE and HPLC separation, respectively. Both hyphenated techniques provide baseline separation of the four deoxynucleotide monophosphates (dNMP), which are present in the DNA chain. With CE-ICP-MS, detection limits for phosphorus down to 53 µg L−1 (2′-deoxyguanosin-5′-monophosphate, dAMP) (corresponding to 0.6 pg P absolute) have been achieved. RSDs of the migration times were about 5%. Using HPLC-ICP-MS, detection limits down to 3 µg L−1 (2′-deoxythymidine-5′-monophosphate, dTMP) (corresponding to 0.03 ng P absolute) were obtained. The migration/elution order of the deoxynucleotides investigated was obtained by comparison with the migration/retention times of commercially available dNMP's. Furthermore it was checked if HPLC-ESI-MS can be operated under the same chromatographic conditions for the confirmation of the elution order and for the characterisation of unknown peaks. Finally, flow injection analysis (FIA) was used for the quantification of the phosphorus content in the dNMP samples. Using FIA, detection limits for phosphorus of 2.5 µg L−1 corresponding to 25 pg phosphorus absolute were achieved.