Solid-phase microextraction combined with surface-enhanced laser desorption/ionization introduction for ion mobility spectrometry and mass spectrometry using polypyrrole coatings

The successful application of polypyrrole (PPY) solid-phase microextraction (SPME) coatings as both an extraction phase and a surface to enhance laser desorption/ionization (SELDI) of analytes is reported. This SPME/SELDI fiber integrates sample preparation and sample introduction on the tip of a coated optical fiber, as well as acting as the transmission medium for the UV laser light. Using ion mobility spectrometry (IMS) detection, the signal intensity was examined as a function of extraction surface area and concentration of analyte. The linear relationship between concentration and signal intensity shows potential applicability of this detection method for quantitative analysis. Extraction time profiles for the fiber, using tetraoctylammonium bromide as test analyte, illustrated that equilibrium can be reached in less than one minute. To investigate the performance of the PPY coating, the laser desorption profile was studied. The fiber was also tested using a quadrupole time-of-flight (Q-TOF) mass spectrometer with leucine enkephalin as test analyte. Since no matrix was used, mass spectra free from matrix background were obtained. This novel SPME/SELDI fiber is easy to manufacture, and is suitable for studying low-mass analytes because of the intrinsic low background. These findings suggest that other types of conductive polymers could also be used as an extraction phase and surface to enhance laser desorption/ionization in mass spectrometry.     

Determination of stimulants in human urine and hair samples by polypyrrole coated capillary in-tube solid phase microextraction coupled with liquid chromatography-electrospray mass spectrometry

A simple and sensitive method for the determination of amphetamine, methamphetamine and their methylenedioxy derivatives in urine and hair samples was developed by coupling automated in-tube solid phase microextraction (SPME) to high performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ES-MS). To achieve optimum performance, the conditions for both the in-tube SPME and the ES-MS detection were investigated. ES-MS detection conditions were studied by flow injection analysis (FIA) with direct liquid injection. In-tube SPME conditions were optimized by selecting the appropriate extraction parameters, including capillary stationary phases and sample pH. For the compounds studied, a custom-made polypyrrole (PPY) coated capillary showed superior extraction efficiency as compared to commercial capillaries. Therefore, the PPY coated capillary was selected for in-tube SPME in this study. The calibration curves of stimulants were linear in the range from 0.1 to 100 ng ml(-1) with detection limits (S/N=3) of 8-56 ng l(-1). This method was successfully applied to the analysis of the stimulants in spiked human urine and hair samples.     

固相微萃取/气相色谱/质谱联用测定水中的2,4-二硝基苯酚

研究了水中痕量2,4-二硝基苯酚的固相微萃取（SPME）方法,得到了2,4-二硝基苯酚的SPME最佳萃取条件：水溶液调pH2,并用NaCl他和,在室温下直接萃取30min,气相色谱／质谱分析时,纤维探针在270℃下脱附3min。所建立的方法适于快速、方便地测定水中2,4-二硝基苯酚,不需浓缩和预处理。     

Automated solid phase dynamic extraction--extraction of organics using a wall coated syringe needle

Extractions of liquid samples were carried out using wall coated needles prepared from stainless steel capillary columns instead of syringe needles. This micro extraction technique was applied to the analysis of pesticides in water. Important parameters influencing the extraction such as sample velocity, extraction time and also the desorption parameters were investigated and optimized. Automation of this technique was realized using a conventional automatic sampler. Limits of detection were improved using the multiple extraction/desorption technique. Chromatographic data and limits of detection were compared with those obtained by solid phase micro extraction (SPME). Using a needle with a 7 microns film yielded limits of detection varying from 0.001-0.1 microgram/L and were in the same range as those resulting from the extraction using a 100 microns polydimethylsiloxane (PDMS) SPME fiber. The main advantages of the needle extraction technique were the significantly higher extraction speed and the practical aspects of a stable steel needle compared to those of a fragile fiber. The extraction speed using a needle with a 7 microns film was up to five times higher than the speed of SPME using a 100 microns PDMS fiber. The steel needle could be stressed mechanically in a higher extent than a SPME fiber. Sample volumes and aliquots of liquid media could be handled and moved from one bottle to another using the automatic sampler.     

Automated in-tube solid phase microextraction coupled with HPLC-ES-MS for the determination of catechins and caffeine in tea

A polypyrrole (PPY) coated capillary and several commercially available capillaries (capillary GC columns) were used to evaluate their extraction efficiencies for catechins and caffeine. Compared with commercial capillaries that were currently used for in-tube solid phase microextraction (SPME), the PPY coated capillary showed better extraction efficiency for all of the compounds studied. Electrospray mass spectrometric (ES-MS) detection conditions were also investigated. After optimization of the extraction and detection conditions, a method for the sensitive and selective determination of catechins and caffeine was developed by coupling the PPY coated capillary in-tube SPME with HPLC-ES-MS. Catechins could be determined in both positive and negative ion detection modes. The detection limit (S/N = 3) for each of the studied catechins was < 0.5 ng mL-1. Caffeine could only be determined under positive ES-MS detection conditions and its detection limit was 0.01 ng mL-1. Caffeine and the five catechins in several tea samples were determined using the developed method. Small amounts of catechins were also detected in grape juice and wine samples.     

Automated solid phase dynamic extraction – Extraction of organics using a wall coated syringe needle

Extractions of liquid samples were carried out using wall coated needles prepared from stainless steel capillary columns instead of syringe needles. This micro extraction technique was applied to the analysis of pesticides in water. Important parameters influencing the extraction such as sample velocity, extraction time and also the desorption parameters were investigated and optimized. Automation of this technique was realized using a conventional automatic sampler. Limits of detection were improved using the multiple extraction / desorption technique. Chromatographic data and limits of detection were compared with those obtained by solid phase micro extraction (SPME). Using a needle with a 7 μm film yielded limits of detection varying from 0.001–0.1 μg/L and were in the same range as those resulting from the extraction using a 100 μm polydimethylsiloxane (PDMS) SPME fiber. The main advantages of the needle extraction technique were the significantly higher extraction speed and the practical aspects of a stable steel needle compared to those of a fragile fiber. The extraction speed using a needle with a ¶7 μm film was up to five times higher than the speed of SPME using a 100 μm PDMS fiber. The steel needle could be stressed mechanically in a higher extent than a SPME fiber. Sample volumes and aliquots of liquid media could be handled and moved from one bottle to another using the automatic sampler.     

Solid phase micro-extraction coupled with ion mobility spectrometry for the analysis of ephedrine in urine

Quantitative solid phase micro-extraction (SPME) coupled with ion mobility spectrometry is demonstrated using the analysis of ephedrine in urine. Since its inception in the 1970's ion mobility spectrometry (IMS) has evolved into a useful technique for laboratories to detect explosives, chemical warfare agents, environment pollutants and, increasingly, for detecting drugs of abuse. Ephedrine is extracted directly from urine samples using SPME and the analyte on the fiber is heated by the IMS desorber unit and vaporized into the drift tube. The analytical procedure was optimized for fiber coating selection, extraction temperature, extraction time, sample pH, and analyte desorption temperature. The carryover effects, ion fragmentation characteristics, peak shapes, and drift times of ephedrine were also evaluated based on the direct interfacing of SPME to IMS. A limit of detection of 50 ng/mL of ephedrine in urine and a linear range of 3 orders of magnitude were obtained, showing that SPME-IMS compares well to other techniques for ephedrine and drug analysis presented in the literature.     

Solid-phase microextraction based on polypyrrole films with different counter ions

Solid-phase microextraction (SPME) fiber coatings based on polypyrrole (PPY) films were prepared by electrochemical deposition of PPY films on platinum wires. To evaluate the effects of counter ions in PPY films on their performance in SPME, PPY films with different counter ions were prepared using different electrolytes during the polymerization processes. The results showed that these PPY films had different extraction properties to the compounds studied due to the different functional groups introduced into the films by the counter ions. Unlike the PPY films formed with small counter ions (such as perchlorate ion) that had anion exchange property, the PPY films having large counter ions such as poly(styrenesulfonate) (PSS) ion showed cation exchange property. Compared with the PPY films having small inorganic counter ions, the PPY films having large organic counter ions, such as dodecylsulphate (DS) ion, showed better extraction efficiency towards nonpolar compounds due to the increased hydrophobic interactions between the compounds and the films. In addition, PPY films formed with large aromatic counter ions had better mechanical stability compared with PPY films with small inorganic counter ions. These films could be applied for SPME of a range of analytes.     

Solid phase microextraction with matrix assisted laser desorption/ionization introduction to mass spectrometry and ion mobility spectrometry

Solid phase microextraction (SPME) with matrix assisted laser desorption/ionization (MALDI) introduction was coupled to mass spectrometry and ion mobility spectrometry. Nicotine and myoglobin in matrix 2,5-dihydroxybenzonic acid (DHB), enkephalin and substance P in alpha-cyano-4-hydroxy cinnaminic acid were investigated as the target compounds. The tip of an optical fiber was silanized for extraction of the analytes of interest from solution. The optical fiber thus served as the sample extraction surface, the support for the sample plus matrix, and the optical pipe to transfer the laser energy from the laser to the sample. The MALDI worked under atmospheric pressure, and both an ion mobility spectrometer and a quadrupole/time-of-flight mass spectrometer were used for the detection of the SPME/MALDI signal. The spectra obtained demonstrate the feasibility of the SPME with MALDI introduction to mass spectrometry instrumentation.     

Polypyrrole/hexagonally ordered silica nanocomposite as a novel fiber coating for solid-phase microextraction

A highly porous fiber coated polypyrrole/hexagonally ordered silica (PPy/SBA15) materials were prepared for solid-phase microextraction (SPME). The PPy/SBA15 nanocomposite was synthesized by an in situ polymerization technique. The resulting material was characterized by the scanning electron microscopy, thermogravimetric analysis and differential thermal analysis. The prepared nanomaterial was immobilized onto a stainless steel wire for fabrication of the SPME fiber. The fiber was evaluated for the extraction of some polycyclic aromatic hydrocarbons (PAHs) from aqueous sample solutions in combination with gas chromatography-mass spectrometry (GC-MS). A one at-the-time optimization strategy was applied for optimizing the important extraction parameters such as extraction temperature, extraction time, ionic strength, stirring rate, desorption time and desorption temperature. In optimum conditions (extraction temperature 70°C, extraction time 20 min, ionic strength 20% (WV(-1)), stirring rate 500 rpm, desorption temperature 270°C, desorption time 5 min) the repeatability for one fiber (n=3), expressed as relative standard deviation (R.S.D. %), was between 5.0% and 9.3% for the tested compounds. The quantitation limit for the studied compounds were between 13.3 and 66.6 pg mL(-1). The life span and stability of the PPy/SBA15 fiber are good, and it can be used more than 50 times at 260°C without any significant change in sorption properties. The developed method offers the advantage of being simple to use, with shorter analysis times, lower cost of equipment, thermal stability of fiber and high relative recovery in comparison to conventional methods of analysis.     

Solid-phase microextraction coupled with capillary electrophoresis for the determination of propranolol enantiomers in urine using a sol-gel derived calix[4]arene fiber

A new type of diglycidyloxy-calix[4]arene coated fiber made by sol-gel method was initially prepared for capillary electrophoresis (CE) sample pretreatment. By using headspace solid-phase microextraction (SPME) combined with a novel back-extraction facility coupled off-line to capillary zone electrophoresis (CZE), the simultaneous determination of propranolol enantiomers in human urine was achieved. The clean up effect and preconcentration effect were realized for the first time without derivatization during the SPME process in terms of these strong polarity and thermal stable compounds. Ultrasonic back-extraction and field amplified sample injection (FASI) technologies were employed. Extraction and back-extraction parameters were optimized. Preconcentration of the sample by calix[4]arene fiber based SPME and FASI increased the sensitivity, yielding a limit of detection (LOD) of 0.01microg/ml by CZE-diode array detection (DAD). Method repeatability (RSD<6.5%) and fiber reusability (>150 extraction procedures) were observed over a linear range (0.05-10microg/ml) in urine samples. Based on the superior thermal stability, high alkali- and solvent-resistant ability, marvelous repeatability and long lifetime of the novel fiber, this SPME-FASI-CZE procedure could meet the demand of minimum required performance limit (MRPL) set by the World Anti-doping Agency (WADA) for the detection of propranolol in urine samples.     

Polypyrrole/montmorillonite nanocomposite as a new solid phase microextraction fiber combined with gas chromatography–corona discharge ion mobility spectrometry for the simultaneous determination of diazinon and fenthion organophosphorus pesticides

A novel solid phase microextraction (SPME) fiber was prepared and coupled with gas chromatography corona discharge ion mobility spectrometry (GC–CD–IMS) based on polypyrrole/montmorillonite nanocomposites for the simultaneous determination of diazinon and fenthion. The nanocomposite polymer was coated using a three-electrode electrochemical system and directly deposited on a Ni–Cr wire by applying a constant potential. The scanning electron microscopy images revealed that the new fiber exhibited a rather porous and homogenous surface. The thermal stability of the fabricated fiber was investigated by thermogravimetric analysis. The effects of different parameters influencing the extraction efficiency such as extraction temperature and time, salt addition, stirring rate, the amount of nanoclay, and desorption temperature were investigated and optimized. The method was exhaustively evaluated in terms of sensitivity, recovery, and reproducibility. The linearity ranges of 0.05–10 and 0.08–10 μg L⁻¹, and the detection limits of 0.020 and 0.035 μg L⁻¹ were obtained for diazinon and fenthion, respectively. The relative standard deviation values were calculated to be lower than 5% and 8% for intra-day and inter-day, respectively. Finally, the developed method was applied to determine the diazinon and fenthion (as model compounds) in cucumber, lettuce, apple, tap and river water samples. The satisfactory recoveries revealed the capability of the two-dimensional separation technique (retention time in GC and drift time in IMS) for the analysis of complex matrices extracted by SPME.     

Rapid screening of methamphetamines in human serum by headspace solid-phase microextraction using a dodecylsulfate-doped polypyrrole film coupled to ion mobility spectrometry

A simple, rapid and highly sensitive method for simultaneous analysis of methamphetamine (MA) and 3,4-methylenedioxy methamphetamine (MDMA) in human serum was developed using the solid-phase microextraction (SPME) combined with ion mobility spectrometry (IMS). A dodecylsulfate-doped polypyrrole (PPy-DS) was applied as a new fiber for SPME. Electrochemically polymerized PPy is formed on the surface of a platinum wire and will contain charge-compensating anion (dodecylsulfate) incorporated during synthesis using cyclic voltammetry (CV) technique. The extraction properties of the fiber to MA and MDMA were examined, using a headspace-SPME (HS-SPME) device and thermal desorption in injection port of IMS. The results show that PPy-DS as a SPME fiber coating is suitable for the successful extraction of these compounds. This method is suitable for the identification and determination of MAs, is not time-consuming, requires small quantities of sample and does not require any derivatization. Parameters like pH, extraction time, ionic strength, and temperature of the sample were studied and optimized to obtain the best extraction results. The HS-SPME-IMS method provided good repeatability (RSDs<7.8 %) for spiked serum samples. The calibration graphs were linear in the range of 20-4000 ng ml(-1) (R(2)>0.99) and detection limits for MDMA and MA were 5 and 8 ng ml(-1), respectively. HS-SPME-IMS of non-spiked serum sample provided a spectrum without any peak from the matrix, supporting an effective sample clean-up. Finally, the proposed method was applied for analysis one of the ecstasy tablet.     

Preparation of A New Fiber by Sol-gel Technology in Solid-phase Microextraction （SPME）

The sol-gel technology is applied for the preparation of solid-phase microextraction (SPME) fiber. The fiber demonstrates high thermal stability, efficient extraction rate and the selectivity for non-polar or low-polar analytes. Efficient SPME-GC-FID analyses of benzenetoluene-ethylbenzene-xylenes (BTEXs) and low-polar halocarbon were achieved by the sol-gel coated DSDA-DDBT-TiO2 fiber. Some parameters of the SPME fiber for the determination of halocarbon in aqueous sample were investigated.     

Quality assessment of Flos Chrysanthemi Indici from different growing areas in China by solid-phase microextraction-gas chromatography-mass spectrometry

Flos Chrysanthemi Indici is a common traditional Chinese medicine (TCM). In this paper, headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was developed for quality assessment of Flos Chrysanthemi Indici from different growing areas in China. SPME parameters such as extraction fibers, extraction temperature, extraction time and sample mass were investigated to achieve identical results to those obtained by the steam distillation (SD). The selected SPME conditions were as follows: SPME fiber coated with 65-microm PDMS/DVB, extraction temperature of 60 degrees C, extraction time of 30 min and sample mass of 1.0 g. Furthermore, four active compounds (eucalyptol, camphor, borneol and bornyl acetate) presented in the TCM were applied to evaluating the quality of Flos Chrysanthemi Indici from 20 various areas. The quality assessment was successfully performed to compare the similarity value (S) between different sample vector of Flos Chrysanthemi Indici and the standard profile vector (SPV). The results showed that the proposed HS-SPME-GC-MS was an alternative technique for quality assessment of Flos Chrysanthemi Indici samples.     

Preparation and applications of polypyrrole films in solid-phase microextraction

Polypyrrole (PPY) and poly-N-phenylpyrrole (PPPY) films were prepared and applied for solid-phase microextraction (SPME). The extraction properties of the new films to volatile organic compounds were examined using an SPME device coupled with GC-flame ionization detection. A PPY-coated capillary was applied for in-tube SPME to evaluate its extraction efficiency towards less volatile compounds and ionic species. The porous surface structures of the films, revealed by scanning electron microscopy, provided high surface areas and allowed for high extraction efficiency. Compared with commercial SPME stationary phases, the new phases showed better selectivity and sensitivity toward polar, aromatic, basic and anionic compounds, due to their inherent multifunctional properties. In addition, PPY and PPPY films showed different selectivity to various groups of compounds studied, indicating that the selectivity of the films could be modified by introducing a new functional group (phenyl in PPPY) into the polymer. For in-tube SPME, the PPY-coated capillary showed superior extraction efficiency to commercial capillaries for a variety of compounds, demonstrating its potential applications for a wide range of analytes when coupled with HPLC. The sensitivity and selectivity of the films for SPME could be tuned by changing the film thickness. These results are in line with both the theoretical expectations and the results obtained by other methods, which indicate not only that PPY films can be used as new stationary phases for SPME. but also that SPME method may provide an alternative tool for studying materials like polypyrrole.     

Preparation and evaluation of solid-phase microextraction fiber based on molecularly imprinted polymers for trace analysis of tetracyclines in complicated samples

Molecularly imprinted polymer (MIP) is widely used in many fields because of its characteristics of high selectivity, chemical stability and easy preparation. To enhance the selectivity and applicability of solid-phase microextraction (SPME), a novel MIP-coated SPME fiber was firstly prepared by multiple co-polymerization method with tetracycline as template. It could be coupled directly to high-performance liquid chromatography (HPLC) and used for trace analysis of tetracyclines (TCs) in complicated samples. The characteristics and application of the fibers were investigated. The electron microscope provided a crosslinked and porous surface, and the average thickness of the MIP coating was 19.5 microm. Compared with the non-imprinted polymer (NIP) coated fibers, the special selectivity to tetracycline and structure-similar oxytetracycline, doxycycline, chlortetracycline were discovered with the MIP-coated fibers. The adsorption and desorption of TCs with the MIP-coated fiber could be achieved quickly. A method for the fluorimetric determination of four TCs by the MIP-coated SPME coupled with HPLC was developed. The optimized extraction conditions such as extraction solvent, desorption solvent, and stirring speed were studied. Linear ranges for the four TCs were 5.00-200 microg/L and detection limits were within the range of 1.0-2.3 microg/L. The method was applied to simultaneous multi-residue analysis of four TCs in the spiked chicken feed, chicken muscle, and milk samples with the satisfactory recoveries.     

Modified Polypyrrole with Tetrasulfonated Nickel Phthalocyanine as a Fiber for Solid-Phase Microextraction. Application to the Extraction of BTEX Compounds from Water Samples

Gold wire was coated with polypyrrole (PPY) by electropolymerization and used as a solid-phase microextraction (SPME) fiber. The adsorptive property of the coating was modified by doping with tetrasulfonated nickel phthalocyanine (NiPcTS). The efficiency and reliability of this fiber was investigated for the extraction of BTEX compounds from the headspace of water samples. Monitoring of extraction efficiency was performed by capillary GC-FID. Effects of several factors such as electropolymerization time, salt addition, exposure time and stirring speed on extraction efficiency were studied. The calibration graphs were linear in the range of 0.06 to 50 ng mL^?1 and the detection limits for BTEX compounds were 20–50 pg mL^?1. Comparing the results obtained using these fibers with results reported in the literature with polydimethylsiloxane (PDMS) fibers shows that under optimum conditions, the detection limits are comparable.     

Molecularly Imprinted Polymer Coated on Stainless Steel Fiber

With characteristics of specific selectivity,good chemical stability and easy preparation,molecularly imprinted polymer (MIP) has been used as the recognition materials m various fields ~([1,2]).Recently,the application of MIP in the sample pre-treatment techniques such as SPME was attractive ~([3,4]).For analysis of complicated samples,the interference matrix would be reduced obviously with the MIP-coated SPME fiber~([5-7]).Because MIPs were coated on the surface of silica fiber through chemical bonding,those fibers could be used for over 80 times without obvious losing of surface quality and extraction performance of MIP coatings.     

新一代萃取分离技术──固相微萃取

介绍了一种新型样品制备法——固相做萃取（SPME）的原理及其应用。与其它样品制备技术相比,SPME法具有操作时间短、样品量小、无需萃取溶剂、适于分析挥发性与非挥发性物质、重视性好等优点。