Selective solid-phase extraction using molecularly imprinted polymer for analysis of methamidophos in water and soil samples.

An analytical methodology for the analysis of methamidophos in water and soil samples incorporating a molecularly imprinted solid-phase extraction process using methamidophos-imprinted polymer was developed. Binding study demonstrated that the polymer exhibited excellent affinity and high selectivity to the methamidophos. Evidence was also found by FT-IR analysis that hydrogen bonding between the CO(2)H in the polymer cavities and the NH(2) and P=O of the template was the origin of methamidophos recognition. The use of molecularly imprinted solid-phase extraction improved the accuracy and precision of the GC method and lowered the limit of detection. The recovery of methamidophos extracted from a 10.0 g soil sample at the 100 ng/g spike level was 95.4%. The limit of detection was 3.8 ng/g. The recovery of methamidophos extracted from 100 mL tap and river water at 1 ng/mL spike level was 96.1% and 95.8%, and the limits of detection were 10 and 13 ng/L respectively. These molecularly imprinted solid-phase extraction procedures enabled selective extraction of polar methamidophos successfully from water and soil samples, demonstrating the potential of molecularly imprinted solid-phase extraction for rapid, selective, and cost-effective sample pretreatment.

[Spectroscopy study of binding mechanisms and molecular recognition of methamidophos-specific moleculary imprinted polymer].

A new methamidophos-specific molecularly imprinted polymer (MIP) was synthesized based on non-covalent interaction. The complexes formed between MAP and MAA were evaluated by 1H NMR, FTIR and UV spectrometry. The MAP-MAA complexes of 1 : 2 mole ratio were obtained by cooperative hydrogen bonding and the complexes possessed better stabilization (K = 2.894 x 10(6) L2 x mol(-2). The Infrared spectrometry differences of the MIPs before and after saturated with MAP further indicated that there were carboxyl functional groups in the MIP, which could interact with the template by cooperative hydrogen bonding specifically.

[Determination of cadmium in tobacco using thermospray-chemical vapor generation-AAS system].

A new and sensitive method for the determination of cadmium was developed using thermospray chemical vapor generation AAS system. The sample and KBH4 solutions were introduced into two separate thermospray tubes by peristaltic pumps and then thermosprayed into a reaction tube. The aerosol of the sample and KBH4 were mixed and reacted in the reaction tube, and after gas-liquid separation in a cyclonic spray chamber, the water vapor was removed by a desolvating unit, while the analyte was transferred into the quartz T-cell and determined by AAS. This design improved the stability and sensitivity by thermospray chemical vapor sample introducing technique. The effect of several experimental parameters of the proposed system was optimized. Under the optimized experimental conditions, the detection limits of 18 ng x L(-1) with RSD of 2.1% was obtained for cadmium determination. This method has been successfully applied to the determination of cadmium in tobacco with the recoveries of 94%-103%.

[Study of thermal diffusivity by piezoelectric photoacoustic phase].

Piezoelectric photoacoustic phase information can be applied to determine the thermal diffusivity of sample. In actual experiments, the results of phase versus modulation frequency deviate from the theory heavily because of the disturbance of instrumental contribution from the whole detecting system. Considering that the instrumental contribution of phase from PA cell can be ignored reasonably, there will be no additional phase contribution after the piezoelectric PA cell has been replaced by microphone PA cell while the other experimental conditions have been kept invariable. Based on this hypothesis, the conventional photoacoustic cell with microphone is employed to determine the instrumental contribution of whole detecting system by studying the PA phase of solid rare earth complexes. The instrumental contribution of phase was considered to be constant for that the same detecting system was used in both the microphone PA method and piezoelectric PA method. This method has been proved by detecting the thermal diffusivity of aluminium sample. The corrected results of experiments match the theory well, showing that the method of subtracting the instrumental contribution from the original experimental phase can be applied reasonably in relevant chopping frequency region. While in lower chopping frequency region, there will be a little deviation from the theoretical results. The method has been also employed to the photoacoustic detection of leaf, and the thermal diffusivity of leaf can be acquired by studying the piezoelectric photoacoustic phase.

[Spectroscopy and XPS studies on molecular recognition of a molecularly imprinted cotinine-specific polymer].

In the present study, molecular imprinting technique was used to develop a method based on noncovalent interaction for the systhesis of a cotinine-specific polymer. The molecular recognition characteristics of the template polymer were evaluated by UV, IR, XPS and 1H NMR. The results indicated that the interactions should be cooperative hydrogen bonds produced by self-assembling of the template and the monomer. The stoichiometric mole ratio of COT-MAA complex is 1 : 2. Furthermore, nitrogen atom of the pyridine ring and oxygen atom of the lactam group in cotinine molecular are hydrogen-bond acceptors, being the predominant binding sites interacting with the functional monomer.

On-line sample digestion using an electromagnetic heating column for the determination of zinc and manganese in tea leaf by flame atomic absorption spectrometry.

A new on-line sample digestion system using electromagnetic induction heating technique was developed for the determination of zinc and manganese in tea leaf by flame atomic absorption spectrometry (FAAS). The homemade electromagnetic heating column (EMHC), whose effective diameter was about 1mm, was composed of a polytetrafluoroethylene (PTFE) outer tube and seven compactly packed PTFE coil-coated iron wires. The pre-digested sample solution was pumped through EMHC and then transferred directly to FAAS for determination. An analytical throughput of 72samplesh(-1) was obtained in the present system. Under optimal condition, the detection limits (3sigma) of zinc and manganese were 4.2mugL(-1) and 3.0mugL(-1), along with relative standard deviations (R.S.D.) of 3.2% and 3.6% respectively for zinc and manganese. Certified reference materials GBW 07602, GBW 07605 and GBW 08505 were analyzed to validate the proposed method, good agreement was achieved between the certified values and the obtained results.

[Spectroscopic characterization of structure of cerium incorporated MCM-48 mesoporous molecular sieve].

Cerium incorporated MCM-48 molecular sieves have been hydrothermally synthesized using a mixed template and pH adjusting route. The samples were characterized by various physicochemical methods, including X-ray diffraction, diffuse reflectance UV-Vis spectroscopy, FTIR spectroscopy, XRF spectroscopy, and nitrogen adsorption. These results reveal that cerium is incorporated in MCM-48 and it is in the form of well-dispersed tetra-coodinated cerium ion. The proper concentration of cerium and adjusting pH can keep Ce-MCM-48 with higher specific surface area , larger unit-cell parameter, narrower pore-size distribution, and thicker pore wall than those of MCM-48. These deduce higher activity, and better selectivity, thermal stability and hydrothermal stability than those of MCM-48. The concentration of Ce incorporated in MCM-48 affects the vibration of the framewoke Si of molecular sieves.

A new molecularly imprinted polymer for selective extraction of cotinine from urine samples by solid-phase extraction.

Cotinine, the main metabolite of nicotine in human body, is widely used as a biomarker for assessment of direct or passive exposure to tobacco smoke. A method for molecularly imprinted solid-phase extraction (MISPE) of cotinine from human urine has been investigated. The molecularly imprinted polymer (MIP) with good selectivity and affinity for cotinine was synthesized using cotinine as the template molecule, methacrylic acid as the functional monomer, and ethylene glycol dimethacrylate as the cross-linker. The imprinted polymer was evaluated for use as a SPE sorbent, in tests with aqueous standards, by comparing recovery data obtained using the imprinted form of the polymer and a non-imprinted form (NIP). Extraction from the aqueous solutions resulted in more than 80% recovery. A range of linearity for cotinine between 0.05 and 5 microg mL-1 was obtained by loading 1 mL blank urine samples spiked with cotinine at different concentrations in acetate buffer of pH 9.0, and by using double basic washing and acidic elution. The intra-day coefficient of variation (CV) was below 7% and inter-day CV was below 10%. This investigation has provided a reliable MISPE-HPLC method for determination of cotinine in human urine from both active smokers and passive smokers.

[Spectroscopy study of molecular recognition of a molecular imprinted monocrotophos-specific polymer].

In the present study, molecular imprinting was used to develop a method based on noncovalent interaction for the synthesis of a monocrotophos-specific polymer. The selective binding characteristics of the template polymer were evaluated by 1H NMR and ultraviolet spectrometry. The polymer obtained was found to interact specifically with monocrotophos by cooperative hydrogen bonding. The infrared spectrometry of the polymer further indicated that there were some functional groups in the moleculary imprinted polymer which could interact on the template.

[Analysis of multi-component sugar aqueous solution in low-concentration by near-infrared spectrometry].

Near infrared spectrophotometry was used to determine the concentrations of one, two and three-component sugar aqueous solutions. However, this method was always applied to dry or low moisture products and was not practicable for fresh fruits and vegetables because of the strong absorption of water in near infrared region. In this paper, the authors applied NIR method to aqueous solutions and discussed how to enhance the sensitivity. In aqueous solution systems, concentration of each individual sugar was in range of 0.01-0.25 mol x L(-1). Different calibrations and predicted results were gotten and compared to each other when full spectra or significant spectra regions were considered. By selecting relevant spectra regions due to important structural information to overcome the disturbance from absorption of water, calculations could be optimized and predicted results of concentrations were more accurate regarding the standard error of calibration (SEC) and standard error of prediction (SEP).

[Determination of cadmium and mercury in tobacco leaves samples by CVAAS].

A new and sensitive method for the determination of cadmium and mercury was developed using nebulous phase reaction, cold vapor atomic absorption spectrometry (CVAAS). This design effectively reduces the loss of cadmium and volatile mercury species in aqueous solution and transfer process. The effects of several experimental parameters of the proposed system were optimized. Using the optimized experimental conditions, detection limits of 21 and 8 ng x L(-1) with RSD of 3.2% and 2.9% (n = 11) were obtained for cadmium and mercury, respectively. This method has been successfully applied to the determination of cadmium and mercury in tobacco leaves samples with the recoveries over 92%.

Reversed-phase electrochromatography with a monolithic microcolumn prepared in a 2.2-mm-inner diameter fused-silica tube.

Capillary electrochromatography possesses advantages of high separation efficiency and velocity, but it also has its disadvantages due to its small inner diameter, such as poor detection sensitivity, low sample capacity, and some trouble in its column preparation. To overcome these shortcomings, a monolithic microcolumn with a surface area larger than 200 m2/g was prepared by sol-gel polycondensation of tetraethoxysilane-hydrochloric acid-poly(ethylene glycol) and filling with fine quartz sand in a 2.2-mm-i.d. fused-silica tube. The prepared microcolumn was used in the separation of aromatic compounds by reversed-phase electrochromatography. Some factors that affected electroosmotic flow were explored, such as electric field strength, buffer concentration, and buffer pH. Acetonitrile concentration in the mobile phase was investigated for phenol, benzene, and naphthalene separation. The separation results were satisfying with the electrochromatographic microcolumns. The detection limits of phenol, benzene, and naphthalene were 0.07, 0.26, and 0.04 mg/L, respectively.

Multivariate calibration analysis for metal porphyrin mixtures by an ant colony algorithm.

A new biomimetic algorithm, Chemical Ant Colony Algorithm, has been developed, which has the characteristics of intelligent search, global optimization, robustness, distributed computation and easy combination with other heuristic. The proposed method has been successfully applied to the spectroscopy analysis of the Zn2+, Cd2+, Pb(2+)-porphyin tribasic color system with supramolecular properties; the errors are within +/-8.0%.

[Analysis of essential oil components by GC/FTIR and GC/MS].

The volatile components of clary sage (Salvia sclarea L.) oil were identified by gas chromatography-Fourier transform infrared spectroscopy (GC/FTIR) and gas chromatography-mass spectrometry (GC/MS). The application of GC/FTIR in analysis of essential oil was mainly discussed. The accuracy of qualitative analysis for essential oil was improved by such technique asthe reconstruction of different spectra regions Gram-Schmidt Fourier transforms infrared spectroscopy, and the application of subtracting of Fourier transforms infrared spectroscopy, and the mass spectrometry.

Gas chromatographic-mass spectrometric determination of polycyclic aromatic hydrocarbons formed during the pyrolysis of phenylalanine.

The formation of polycyclic aromatic hydrocarbons (PAHs) during pyrolysis process of phenylalanine had been studied. Ten PAHs, including fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[k]fluoranthene, benzo[e]pyrene, and benzo[a]pyrene were analyzed by gas chromatography-mass spectrometry using selective ion monitoring mode. This technique offers the capability to analyze trace amounts of PAHs in phenylalanine pyrolyzates. The pyrolysis was carried out in a micro-furnace with quartz furnace liner. The injection was conducted with glass pelletizer syringe to avoid metal contamination. Qualitative results were obtained at 900 degrees C and quantitative analysis of 10 PAHs was done for 700 and 900 degrees C.

[A novel method for the determination of inorganic ions in complex plant samples by near infrared spectroscopy].

Inorganic ions in plant samples can be determined by near-infrared (NIR) spectral technique, because they are combined with organic groups with NIR absorption. A method for the determination of inorganic ions in complex plant samples was established based on the combination of discrete wavelet transform (DWT) and NIR technique. In the proposed method, the raw NIR data and their wavelet coefficients are used for modeling and prediction of the contents of potassium in tobaccos by partial least square method (PLS). It is shown that there is almost no loss of spectral information with the NIR data compressed to 3.3% of its original size. The model based on wavelet coefficients is better than that based on the full NIR spectral range. With the improved method, accurate prediction can be achieved.

[Determination of lead in human hair using flame atomic absorption spectrometry and nebulization assisted with hydride generation].

Lead in human hair was determined using flame atomic absorption spectrometry and nebulization assisted with hydride generation and K3Fe(CN)6-HCl system. The method is simple and rapid for operation. The performance of the method was compared with conventional flame atomic absorption spectrometry for direct determination of lead. An improved sensitivity by 13.4 fold was obtained compared to the conventional FAAS for direct determination of lead. The effects of several experimental parameters on the lead determination were optimized, and the influences of interference ions on the determination were investigated. The limit of detection (3sigma) of the proposed method was 2.8 microg x L(-1). The method has been applied to the determination of human hair sample satisfactorily with a recovery of 96%-99%.

[Research on the nonlinear model of near infrared spectroscopy and the total sugar of tobacco samples].

Near infrared spectroscopy (NIR) is an instrumental method applied for rapidly measuring the NIR spectra of pulverized tobacco samples and computing the chemical compositions from the spectral data. In the present paper, a mixed algorithm was employed for building the nonlinear model of NIR and the total sugar of tobacco samples. The mixed algorithm was combined with Partial Least Squares (PLS) method and Artificial Neural Network (ANN). The model based on the mixed algorithm was divided into two parts: linear part and nonlinear part, and the corresponding model of each part was built respectively. Compared with the classical multivariate calibration methods such as Principle Component Regression (PCR), PLS and nonlinear PLS (NPLS), the proposed procedure performed much better. The results showed that the mixed algorithm could be used for the quantitative analysis of the total sugar in tobacco samples.

[The separation of overlapping peaks of lanthanide complex by photoacoustic phase-resolved method].

Photoacoustic(PA) phase-resolved method is used to separate the overlapping peaks of lanthanide complex for the first time. PA peaks of Nd3+ are covered completely by the PA absorption of tryptophan(Trp) for Nd(Trp)3Cl3.H2O within 300-400 nm. The patterns of PA phase spectrum depend on the ligand and lanthanide ion, and the phase angles are associated with the lifetime of the excited states and the optical absorption coefficient. Different phase angles of the ligand and lanthanide ion bring the possibility to separate their overlapping peaks by PA phase-resolved method. The phase angle of Trp(106 degrees) is calculated according to the in-phase and out-of-phase signals. In the PA amplitude spectrum, only the contribution of Nd3+ can be observed when the phase angle varies 90 degrees. PA peaks of Nd(Trp)3Cl3.H2O are separated well and assigned. PA phase-resolved method has the advantage to interpreted the spectrum based on different phase angles, and is free from the overlapping of different absorption bands.