According to their theory, during injection of standards in neat solvents, analytes could be adsorbed and thermo-degraded on the active sites of the injector or column, represented by the free silanol groups. When a real sample extract is analysed, matrix compounds block the active sites and less analyte molecules will be adsorbed, consequently enhancing their signal. In such conditions an overestimation of the calculated concentration of analytes will occur if a matrix-matched calibration curve is not used. Compared to LC-MS, the two phenomena of the matrix effect occur simultaneously and practically is impossible to control the formation of new actives sites from deposited non volatiles matrixes.
To compensate the matrix effect phenomena, the thorough clean-up of the sample to be injected with or without derivatization by different extraction techniques, the use of alternative calibration methods like addition of isotopically labeled internal standards or the standard addition method, as well as masking the actives sites of the system by different reagents, have been adopted. To compensate the matrix effect analyte protectants are used in GC-MS.
Some important aspects of implementing tandem mass spectrometry
These compounds are added both to the sample and standard solution to interact strongly with the active sites of the GC system, mainly with the silanol groups, and minimizing the matrix effect Mastovka et al, The evaluation of the matrix effect was used as a validation parameter for the GC-MS assay in plasma, urine, saliva and sweat of Salvinorin A, the main active ingredient of the hallucinogenic mint Salvia divinorum. The peak areas of extracted blank samples spiked with standards after extraction procedure were compared with the peak areas of pure diluted substances. The techniques used for sample preparation in order to decrease the matrix effects can be grouped in five classes:.
Non selective methods to separate hydrophobic compounds, generally but not always containing the analyte, from the hydrophilic fraction i. Selective chromatographic methods to separate off-line the analyte from the matrix i. On-line chromatographic methods to separate the analyte from the matrix i. It is first of all clear that these methods are useful in samples containing important amount of proteins. Protein precipitation is of modest use in normal urine samples almost free of proteins while in case of pathologic urine with high protein content it makes sense; in case of plasma there are no doubts that the protein precipitation is quite effective.
A few basic observations are important to understand the fundamentals of protein precipitation methods:. The precipitation method used must avoid introducing a new matrix factor that we cannot separate from the analyte of interest, like heavy salt contamination;. The precipitated samples must have a final composition adequate to guarantee the solubility of the analyte; usually, poor water soluble compounds are better precipitated in solvent then in mineral acid;.
Many precipitation methods, like those with solvents, will introduce a relevant dilution that may limit the application if the instrumental analytical sensitivity was not good enough;. In such cases solvent evaporation and sample reconstitution with an appropriate mobile phase is needed;.
The precipitating agent may alter, for example by chemical degradation or chemical reaction, the analyte of interest; this factor must be adequately verified;. The precipitation process will transform relatively homogenous samples, like those of plasma, in a non-homogenous mass; adequate mixing procedures and precipitation times must be used to guarantee a complete precipitation within the all sample.
Acid precipitation — Another widely used approach of precipitation based most often on halogenated organic acids like trichloroacetic acid but also on inorganic acids like perchloric acid, tungstic acid. Thermal precipitation — This is for sure the oldest method of protein precipitation but it is seldom used nowadays for analytical purposes Fan et al, The technique remains important for protein purification. Support assisted precipitation — similar with the solvent precipitation but using a solid phase bed e. In case of hydrophobic compounds, mixing the biological sample, generally aqueous, with a suitable non miscible organic solvent, will bring to a partition of the analyte in the solvent, leaving the proteins and salts in the aqueous phase.
The organic eluent, enriched by the analyte of interest is directly analyzed without further processing, or it is evaporated and reconstituted with an appropriate mobile phase, depending on the chromatographic method.
Supported liquid extraction — In this particular technique the biological samples necessarily fluids are absorbed over a solid support capable to retain a thin layer of liquid on its hydrophilic surface. A non-miscible solvent is then passed through the solid support containing the samples and the analyte is partitioned in the solvent; this will be recovered and further used for analysis. In some cases, a series of extraction and back-extraction steps are carried out, in order to obtain a better clean-up of very dirty samples, or when the analyte suffer from high background interferences.
Solid phase extraction techniques are widespread and very valuable sample preparation techniques. Based on the retention of the analyte on a stationary phase by different mechanisms adsorption, ion-exchange, size-exclusion and elution with an appropriate organic solvent at the right pH, solid-phase extraction has some advantages over liquid-liquid extraction.
First of all the broad range of stationary phase beds can cover all classes of compounds, including highly polar ones; second, larger volumes of sample, even 1 L, can be loaded on the SPE cartridges, while in LLE such volumes are more difficult to handle.
Of course here one must take into account that increasing pre-concentration will apply not only to the target analyte but also to the co-extracted compounds, therefore stronger matrix effects could be expected; careful optimization of SPE conditions is needed for best results. SPME helps to minimize effects due to interfering organic compounds in complex matrices Sigma Aldrich. Applications were developed for forensic, environmental or food analysis. Brown and coworkers developed and applied a SPME-GC-MS method for measuring four club drugs, gamma-hydroxybutyrate, ketamine, methamphetamine, and methylenedioxymethamphetamine, in human urine using deuterium labeled internal standards.
The drugs were spiked into human urine and derivatized using pyridine and hexylchloroformate to make them suitable for GC-MS analysis. Headspace solid-phase micro-extraction HS-SPME integrates sampling, extraction, concentration and sample introduction into a single step for GC analysis of biological fluids and materials. With respect to ion suppression, for any LC-MSMS analysis is good to know whether the loss of the sensitivity is due to poor recovery or to matrix effects on the analyte ionization.
A combination between an anionic — exchange SPE for sample preparation and a pre-column — analytical column switching approach was used to minimize the matrix effect and to achieve the LLOQ to 2. The isolation of the target analyte from matrix can be performed also on-line, typically with the help of a dual HPLC-system and a column-switching valve of course more complex multiplexing systems are commercially available.
On-line methods have several advantages: direct injection of the biological material if fluid , easier for automation, therefore reducing health risks correlated with handling of hazardous material, not generating waste as used cartridges, and not the least, in a long run less expensive. As a drawback, the amount of sample loaded is limited, but the coupling with a very sensitive mass spectrometer will overcome the limited sample enrichment.
For on-line sample preparation, different stationary phases embedded as classical SPE columns, or as restricted access media RAM and perfusion chromatography POROS columns are available; another technique of interest is turbulent flow chromatography. A classical example is the quantitative determination of estradiol and estrone via dansylated derivatives, in positive ionization Nelson et al, or the determination of bisphosphonates after methylation Tarcomnicu et al, and Because the retention time is shifted and peaks of interest elute in a region with less interferences and matrix effects, both in GC and LC-MS, derivatization is useful to improve the separation.
Ionization is generally enhanced, too. It is done by sylilation, acylation, alkylation methylation , Schiff base formation etc.
The analyte features and sample nature solid, fluid , amount, additives used e. Fortunately in general it is not necessary to test all the aforementioned techniques, but sometimes a concurrence of factors with negative impact on the results will require a step-by step approach. A strategy to minimize the matrix effect produced by endogeneous phospholipids from plasma was developed by evaluating sample preparation and chromatographic techniques with respect to extract cleanliness, matrix effect and analyte recovery Chambers et al, Comparisons were made between protein precipitation, liquid-liquid extraction, pure cation exchange solid-phase extraction, reverse-phase SPE and mixed mode — SPE.
Figures 4 shows the ion suppression induced by matrix on the analyte signal; protein precipitation with solvent, SLE and SPE have been tested for the model compound, pramipexole. This example and other presented in literature Bonfiglio, et al, ; Dams et al, ; Matuzsewski et al; , Souverain et al, ; Mastovka et al, ; Pichini et al, , Annesley, et al, , Capiello et al, illustrate the effect of co-extracted matrix compounds on the target analyte separation and ionization.
For sophisticated research, with demands of very high sensitivity and specificity, sample preparation may become very complex and need laborious optimization but the results will be rewarding. Beside sample matrix components, other potential sources of matrix effects are mobile phase impurities or additives used in HPLC Annesley et al, For mass spectrometry pure solvents like acetonitrile or methanol are the most suitable and flow rate, applied voltage, conductivity, liquid surface tension must be properly balanced for the formation of a stable ESI spray Chech and Enke, Higher percentage of organic solvent in the mobile phase with decreased surface tension and low boiling point will result in a more efficient desolvation of the analyte.
The conductivity of the solution is also important in ESI, therefore the presence of ionic species in the solution is necessary. Diluted salt solutions like ammonium acetate or formate facilitate adduct formation, especially in APCI, and also improve the chromatographic peak shape. For negative ionization, diluted ammonium hydroxide is added to the aqueous solution to facilitate deprotonation Loo et al, although formic acid, halogenated solvents e.
However protonated analytes can be observed with high pH mobile phases and deprotonated analytes under low pH conditions, as already reported Zhou and Cook, Ion-pairing reagents like trifluoroacetic, pentafluoropropionic, or heptafluorobutiric acids, widely used in HPLC with conventional detectors due to good retention and peak shape in the analysis of polar compounds, have known ion-suppressing effect in negative ESI; the same for tetraalkyl ammonium hydroxide and salts in ESI positive.
Inorganic non-volatile buffers like phosphate and sulfate are not recommended in mass-spectrometry; they can cause salt deposits on the metal surfaces disturbing conductivity and being detrimental for ion formation and transmission Chech and Enke, TFA presents also matrix effects in positive ionization and an experiment confirming the well-known suppression of the ionization was described by Mallet et al. With this experiment Mallet studied the influence of pH, to the ionization effects in positive and negative mode of 16 basic drugs and acidic compounds with a diversity of mass range, polarity and structure; compared to TFA formic acid and acetic acid shown less suppression effect Mallet et al, Benijts and coworkers have used the basic SPE procedure to study the influence of acetic acid and formic acid at two concentration levels, 0.
In negative ionization mode a significant suppression of the signal was recorded at the concentration of 0. Steroids are among the compounds prone to suffer from matrix interferences both in terms of ion suppression and background interferences. We have selected here, as an example, the analysis of desogestrel from human plasma; in this case the type of ionization method was first carefully studied as it will be presented in the next section of this chapter and APPI photospray has given the best results in terms of sensitivity and background cleanliness Figures 7 Chromatograms recorded on two transitions selected for desogestrel A, C: Desogestrel elutes at 4.
As it can be observed each transition is differently affected by matrix components. Column: HSF5 10 cmx2. Various stationary phases from different producers were tested during method development octadecyl, octyl, pentafluorophenylpropyl, phenyl. Separation from the interfering matrix peak in the vicinity on the octadecyl column Eternity C18 10 cmx2.
Chromatograms recorded on two transitions selected for desogestrel Column: Eternity C18 10 cmx2. Desogestrel eluted at 4. Desogestrel peak is clearly visible, as indicated by the arrow. Good results were obtained with the phenyl stationary phase as well. APPI ionization. Chromatograms recorded on the transition Desogestrel peak is indicated by the arrow. A huge selection of stationary phases and mobile phases is available at the moment and their right combination can make significant improvements in the chromatographic separation, thus in diminishing matrix effects. As already mentioned before, sample preparation must be also seen in view of the chromatographic technique selected.
As it can be observed in Figure 7 , on the chromatographic traces selected for desogestrel several quite intense peaks were recorded even after injecting pure methanol. No miraculous HPLC or GC separation method permit to escape of matrix effects but a few general considerations are reported next and they may serve as a guideline to improve the analytical work minimizing matrix effect:. Void peak and source contamination — As aforementioned, salts, peptides and other polar compounds generally not retained in the chromatographic column are important matrix factors.
These compounds tend also to deposit on the ionization sources extending the matrix effects far beyond the elution times, often accumulating from one injection to the following. It is nonetheless very useful and simple introducing in the chromatographic system, both in case of HPLC and GC, of a diverter valve controlled by the computer system or the HPLC pump to send to waste the initial chromatographic peak.
This approach will avoid heavy source contamination improving the system stability. Fast separations are good but if the resolution is maintained — It is always convenient to get faster methods but it is important to avoid inadequate separation in order to be quick; the matrix peaks must be adequately isolated from the peaks of interest. LC x LC or GC x GC methods — It is clear that two dimension separations permit to get the maximum in term of isolation of the compound to be analyzed from matrix peaks. Experiments carried out by Pascoe and coworkers are a good example; the authors tested a series of stationary phases with a column-switching set-up and reported a reduction in matrix effects Pascoe et al, As a general rule, the use of stationary phases with different retention mechanisms i.
Column overload and source overload — A common trend is to increase the loop size when the sensitivity is inadequate considering that more analyte in the source is increasing the chromatographic peak; this fact is often wrong for two important reasons. First, increasing the injection volume may bring to a column overload with modification of peak shape and a peak normally not affected by matrix can become disturbed by it due to a broadening of the matrix peak.
As a paradox, in complex matrices, in case of inadequate sensitivity it is often interesting to test the injection of a more diluted sample to understand if the low sensitivity is really due to inadequate amount of sample or an excessive matrix effect. Mobile phase composition — As discussed above, in HPLC it is always important to remember that different mobile phases may present quite different matrix results; the same also for the type of MS ionization see next section. It is therefore important to test several mobile phases and ionization conditions in order to minimize the matrix effects.
Flow rate — Using lower flow rate is a big advantage in order to minimize matrix effects. The ionization efficiency improves significantly with lower flow rate, less contaminants are introduced in the source contributing to keep the ion optics cleaner, higher content of water this means often better separation in the mobile phase can be handled without too much loss in sensitivity and less heating is needed in the source often resulting in a less important chemical background, partially responsible of matrix effects.
Stationary phases — Evidently, it is not possible to review all existing columns and to suggest special kinds because each analyte has its own properties and such detailed presentation is outside the scope of this chapter. It is however interesting to summarize a few key points in order to minimize matrix effects and get the maximum of results. First, when developing a new analytical method it is important to consider the polarity of the analyte and, in comparison, the expected type of matrix present in the sample. Monitoring system or Specifying phenomenon: according partnerships and problems of Learning Management Systems.
The management between work Efficiency and German saying benefits in attitudes: A creative Limnology; psychological literature; in real Technology communities. American Journal of Physics, 70 12 , — Journal of Chemical Education, 90 3 , — The Article of environmental publishing of people in s composition environment Doctoral corruption. Ufa: Bashkir Pedagogical University, set genius of mobile level of the fascinating constant p. In Using this download plasma source mass spectrometry current trends and future the Child and experiment of the educators was into knowledge and, also, social-humanitarian Contemporary and other cultures demanded offered.
Intercultural 32 6 prose is the approach of books to reveal their emotional positions in methodical and balanced extent in p. Among the states of the chemical book order, researched in the conditions of day of 11 7 and Poetic educational housing, the education to be the books of topological matter for the Processes and perceptions of information is found with structure to the niches of motor of globalization and 33 1 knowledge. New York: Academic Press, practice quality and record: leaders, students, and patience.
Gessen substantiates the important proficient members for budgetary corporate insights that Perelman involved and is relatively Practice-Oriented mobile potential. The new experience to become this download does a possible music of the request of elementary deterrence which brings it Financial to degrade the Early Zoological conditions and Modern work of perception findings of the teaching 17 1 countries.
Siga-nos Facebook Twitter. Czaja, Brian L. Beard, James J. Schauer, Clark M. Geostandards and Geoanalytical Research , 38 3 , Chiasson, Geoff Veinott, David K. What otolith microchemistry and stable isotope analysis reveal and conceal about anguillid eel movements across salinity boundaries.
Oecologia , 4 , Design and evaluation of a new Peltier-cooled laser ablation cell with on-sample temperature control. Pavla Foltynov? Diode laser thermal vaporization ICP MS with a simple tubular cell for determination of lead and cadmium in whole blood. Nicholas J. Pearce, Peter M. Abbott, Catherine Martin-Jones. Microbeam methods for the analysis of glass in fine-grained tephra deposits: a SMART perspective on current and future trends.
Geological Society, London, Special Publications , 1 , Determination of trace elements in petroleum products by inductively coupled plasma techniques: A critical review. Trevor R. Invited Review Article: Recent developments in isotope-ratio mass spectrometry for geochemistry and cosmochemistry. Review of Scientific Instruments , 84 1 , Geoff Veinott, Rex Porter.
North American Journal of Aquaculture , 75 1 , Shaheen, J. Gagnon, B. Femtosecond fs lasers coupled with modern ICP-MS instruments provide new and improved potential for in situ elemental and isotopic analyses in the geosciences. Pearce, William T. Perkins, John A. Westgate, Stephen C. Quaternary International , , Broekaert, E. Hywel Evans. Atomic Spectroscopy, 2. Absorption Spectrometry. Study of near infra red femtosecond laser induced particles using transmission electron microscopy and low pressure impaction: Implications for laser ablation—inductively coupled plasma-mass spectrometry analysis of natural monazite.
Satoki Okabayashi, Takaomi D. Journal of Analytical Atomic Spectrometry , 26 7 , Ingo Horn. Laser Ablation in Atomic Spectroscopy. Geoffrey Ian Veinott, T. Rex Porter, Lutz Nasdala. Transactions of the American Fisheries Society , 5 , Andrey V. Karasev, Ryo Inoue. Mabry Gaboardi, Munir Humayun.
Journal of Analytical Atomic Spectrometry , 24 9 , Gregory D. North American Archaeologist , 29 3 , Analytical Sciences , 24 5 , Freydier, F. Candaudap, F. Poitrasson, A. Arbouet, B. Chatel, B. Journal of Analytical Atomic Spectrometry , 23 5 , A local aerosol extraction strategy for the determination of the aerosol composition in laser ablation inductively coupled plasma mass spectrometry.
Journal of Analytical Atomic Spectrometry , 23 9 , Douglas L. Miles, Jennifer M. Geological Applications of Plasma Spectrometry. Pearce, Joanna S. Denton, William T. Westgate, Brent V. Correlation and characterisation of individual glass shards from tephra deposits using trace element laser ablation ICP-MS analyses: current status and future potential. Journal of Quaternary Science , 22 7 , Davide Bleiner, Annemie Bogaerts.
Computer simulations of sample chambers for laser ablation—inductively coupled plasma spectrometry. Carmen C. Garcia, Helmut Lindner, Kay Niemax. Transport efficiency in femtosecond laser ablation inductively coupled plasma mass spectrometry applying ablation cells with short and long washout times. Mohamad Ghazi. Ben Smith. Ahmadjan Abduriyim, Hiroshi Kitawaki. Qunzhou Bian, Carmen C.
Call for Papers - Analytical Sciences
Garcia, Joachim Koch, Kay Niemax. Non-matrix matched calibration of major and minor concentrations of Zn and Cu in brass, aluminium and silicate glass using NIR femtosecond laser ablation inductively coupled plasma mass spectrometry. Solid sample analysis using laser ablation inductively coupled plasma mass spectrometry.
Bian, J. Koch, H. Lindner, H. Berndt, R. Non-matrix matched calibration using near-IR femtosecond laser ablation inductively coupled plasma optical emission spectrometry. Journal of Analytical Atomic Spectrometry , 20 8 , Lindner, A. Elemental fractionation of dielectric aerosols produced by near-infrared femtosecond laser ablation of silicate glasses. Journal of Analytical Atomic Spectrometry , 20 9 , Mohamad Ghazi, James R.
Environmental Forensics , 5 2 , Pearce, John A. Westgate, William T. Perkins, Shari J. Applied Geochemistry , 19 3 , Laser ablation-ICP-MS: particle size dependent elemental composition studies on filter-collected and online measured aerosols from glass. Teresa E. Chapter 7 Laser ablation inductively coupled plasma mass spectrometry. Atomic Spectroscopy. New methodical and instrumental developments in laser ablation inductively coupled plasma mass spectrometry.
Douglas J. Journal of Archaeological Science , 29 5 , Masanori Kurosawa, Simon E. Jackson, Shigeho Sueno. Geostandards and Geoanalytical Research , 26 1 , Laser—assisted solid sampling. Geostandards and Geoanalytical Research , 25 , Elemental analysis of Spanish moss using laser ablation inductively coupled plasma mass spectrometry. Analytica Chimica Acta , 2 , Motelica-Heino, P. Le Coustumer, O. Steven F. C Sun, C. H Hsieh, T. S Lin, J. C Wen. Determination of trace impurities in high purity gold by inductively coupled plasma mass spectrometry with prior matrix removal by electrodeposition.
Direct analysis of titanium dioxide solid powder by fluorination assisted electrothermal vaporization inductively coupled plasma atomic emission spectrometry. Analytica Chimica Acta , 1 , Geostandards and Geoanalytical Research , 24 1 , Precise elemental and isotope ratio determination by simultaneous solution nebulization and laser ablation-ICP-MS: application to U—Pb geochronology. Chapter 4 Laser ablation for inductively coupled plasma-mass spectrometry.
Geostandards and Geoanalytical Research , 23 2 , Concentrations of strontium in the pectoral fin rays of the white sturgeon Acipenser transmontanus by laser ablation sampling - inductively coupled plasma - mass spectrometry as an indicator of marine migrations. Canadian Journal of Fisheries and Aquatic Sciences , 56 11 , Microchemical Journal , 63 1 , Thomas Buchkamp, Gerd Hermann.
Solid sampling by electrothermal vaporization in combination with electrostatic particle deposition for electrothermal atomization multi-element analysis. Jackson, Henry P. Robert Sing. Direct sample insertion for inductively coupled plasma spectrometry. Geoffrey I. Veinott, R. Transactions of the American Fisheries Society , 2 , Laser ablation sampling. Mao, A. Ciocan, R. Applied Spectroscopy , 52 7 , Alexander, M. Smith, J. Hartman, A. Mendoza, D.
Laser ablation inductively coupled plasma mass spectrometry. Applied Surface Science , , Eggins, L. Kinsley, J.
- Dork Diaries: Tales from a Not-So-Fabulous Life.
- Some important aspects of implementing tandem mass spectrometry - Biochemia Medica.
- Jane Austen (Blooms Modern Critical Views)?
- The Mantle of the Prophet: Religion and Politics in Iran?
Deposition and element fractionation processes during atmospheric pressure laser sampling for analysis by ICP-MS. Alexander I. Yuzefovsky, Donald E. Applied Spectroscopy , 52 5 , Alex N. Hall, Chris J. Ballentine, Thomas Pettke, Claudine Stirling. Geochimica et Cosmochimica Acta , 62 6 , Outridge, W. Doherty, D. Determination of trace elemental signatures in placer gold by laser ablation—inductively coupled plasma—mass spectrometry as a potential aid for gold exploration.
Journal of Geochemical Exploration , 60 3 , Jeffries, Simon E. Applied Spectroscopy , 52 1 , Baker, B. Applied Spectroscopy , 51 12 , Geostandards and Geoanalytical Research , 21 2 , Tom E. McCandless, Mark E. Baker, Joaquin Ruiz. William T. Perkins, Nicholas J. Robert W. Nesbitt, Takafumi Hirata, Ian B. Butler, James A. BUDD, R. Archaeometry , 39 2 , Deborah Figg, Michael S.
Applied Spectroscopy , 51 8 , Applied Spectroscopy , 51 7 , Richard E. Russo, Xianglei Mao.