Identification and Quantification of Polar Nitroaromatic Compounds in Explosive-Contaminated Waters by means of HPLC-ESI-MS-MS and HPLC-UV

In the area of former ammunition plants, contaminations caused by explosives and their degradation products are of great environmental relevance because of the immediate vicinity of ground- and drinking water reservoirs. Beside the determination of selected explosive-related compounds by means of HPLC with UV detection, a LC-MS-MS coupling utilizing electrospray ionisation was developed, which is particularly suited for the determination of highly polar compounds. Therewith, 12 different explosive-related compounds were identified and quantified on the basis of specific precursor-/ product-ion traces using the high selectivity and sensitivity of multiple reaction monitoring mode (MRM) of a triple quadrupole mass spectrometer. The LC-MS-MS-technique was applied to water samples from the area of a former ammunition plant. In addition to dinitrophenols and aminodinitrotoluenes which could be determined also by HPLC-UV, some highly polar compounds were found in the contaminated water, for example 3,5-dinitrobenzoic acid and 2-amino-4,6-dinitrobenzoic acid. The highest concentrations (14–40 μg L⁻¹) were found for two isomers of dinitrotoluenesulfonic acids. In order to assure the quantitative determination of polar substances in real samples with different composition, external calibration and standard addition method were compared. The presented LC-MS-MS-method is suited for screening and quantification of polar and hydrophilic explosive-related compounds from different classes of substances in a single analytical protocol.     

Low temperature purification method for the determination of abamectin and ivermectin in edible oils by liquid chromatographytandem mass spectrometry

In this study,a method based on low temperature purification(LTP) coupled with liquid chromatography-tandem mass spectrometry(LC-MS/MS) was developed for the determination of abamectin(ABA) and ivermectin(IVR) in edible oils.ABA and IVR were extracted using conventional liquid-liquid extraction followed by purification via precipitation of interfering fatty components at low temperature without an additional cleanup step.LTP is simple,easy to use,labour-saving and cost effective,and requires reduced amounts of organic solvent.The linear ranges of ABA and IVR were 5-1000 μg/L using matrix-matched standards.Limits of detection(LOD) and limits of quantification(LOQ)were in the range of 0.1-0.4 μg/kg and 0.3-1.3 μg/kg,respectively.The LOQs were below the strictest maximum residue limits established by Codex Alimentarius Commission.Recoveries at three spiked levels of 10,20 and 100 μg/kg in peanut oil,corn oil,olive oil,soybean oil and lard ranged from 71.1%to119.3%with relative standard deviations of 3.2%-10.3%,which were in agreement with those obtained by the solid phase extraction method.The proposed method was utilized in the analysis of 10 edible oil samples from local market and neither ABA nor IVR was detected.As far as we know,this is the first time that LTP is applied to the determination of avermectins in edible oils.     

Analysis of Trace-Level Volatile Compounds in Fresh Turf Crop （Lolium perenne L.） by Gas Chromatography Quadrupole Time-of-Flight Mass Spectrometry

In the traditional research of volatile compounds, some trace-level compounds could not be identified by gas chromatography-mass spectrometry. Target and post-targeted methods were applied in the investigation of trace-level volatile compounds in fresh turf crop （Lolium perenne L.） based on gas chromatography in combination with hybrid quadrupole time-of-flight mass spectrometry. According to literatures published, a target analysis was performed by using retention index, accurate masses of characteristic ions and second-stage mass spectra （MS2 spectra）. And a series of experiments showed that low electron impact energy was beneficial to the improvement of the abundances of low abundance molecular ion peak. peak was beneficial to qualitative analysis. Totally, 60 Enhancing the abundances of low abundance molecular ion volatile compounds were identified, the great majority cornpounds of which were benzeneacetaldehyde （14.8%）, 2,5-dimethyl-pyrazine （9.6%）, and hexanal （9.3%）. Identification was complied by mass spectral search, retention index and accurate masses of characteristic ions.     

Analysis of nitrobenzene compounds in water and soil samples by graphene composite-based solid-phase microextraction coupled with gas chromatography–mass spectrometry

In this work, solid-phase microextraction coupled with gas chromatography–mass spectrometry was developed to determine trace levels of nitrobenzene compounds in water and soil samples. Graphene was chosen as the extraction material and its composite was coated on a stainless steel wire through sol–gel technique for the solid phase microextraction. The key parameters influencing the extraction efficiency were optimized. Under the optimal conditions, the linearity for the compounds was observed in the range of 0.02–15.0 mg/L for water samples, and 0.2–60.0 mg/kg for soil samples, with the correlation coefficients（r） of 0.9966–0.9987. The limits of detection of the method were 0.0025–0.005 mg/L for water samples, and 0.02–0.04 mg/kg for soil samples. The recoveries for the spiked samples were in the range of 72.0%–113.2%, and the precision, expressed as the relative standard deviations, was less than 12.1%.     

电渗流与缓冲液浓度之间数学关系的线性表达

It was believed that electroosmotic mobility μeo is inversely proportional to the square root of the ionic strength L But the linear relationship for regression analysis was expressed differently in different papers. The paper studied the linear expression of the mathematical relationship between μeo and c （background buffer concentration） by mathematical transform and real experimental data.μeo values of fused silica capillary were determined in four buffer systems. Their experimental conditions were controlled carefully for decreasing temperature difference AT and pH difference ApH in 50 μm ID capillary, in which no double layer overlap existed. The linear relationship between the reciprocal of electroosmotic mobility and the square root of concentration （or ionic strength） was derived by mathematical method. The regression analysis of experimental data was shown to well correspond to the relationship. The constants in regression equation could be well defined and the calculated results were acceptable.     

Reliable screening of pesticide residues in maternal and umbilical cord sera by gas chromatography-quadrupole time of flight mass spectrometry

The widespread use of pesticides induces heavy adverse effects on human health,especially for the pregnant women and the newborns.In this study,a screening method has been developed for the determination of multi-pesticides in maternal and umbilical cord sera.All pesticides in sera were collected using solid phase extraction(SPE),and analyzed by gas chromatography-quadrupole time of flight mass spectrometry(GC-QTOF MS).To set up the quality criteria,a database of 50 pesticides was created and the accurate masses of 3 up to 5 representative ions with their intensity ratios were included for each pesticide.In addition,a novel"identification points"(IPs)system relying on the accurate MS1 and MS2 spectra was used to interpret the data for each suspected pesticide.The methodology was then applied to a pair of maternal and umbilical cord sera.A total of six pesticide residues were screened out successfully.In conclusion,GC-QTOF MS combined with an accurate mass database seemed to be one of the most efficient tools for systematic pesticide analysis.     

FLAME ATOMIC ABSORPTION DETERMINATION OF COPPER IN CEREALS FOOD SAMPLES WITH THE PRECONCENTRATION OF POTASSIUM TETRATITANATE WHISKER

A simple and reliable method has been developed for separation and preconcentration of trace amounts of copper ions in cereals food for subsequent measurement by flame atomic absorption spectrometry （FAAS）. The Cu^2＋ ions are adsorbed selectively and quantitatively during the passage. The retained copper ions were desorbed from the potassium tetratitanate whisker with 10.0mL of 2mol/L sulphuric acid solutions as eluent and were determined by FAAS. The linear range was 0.05μg/mL-0.20μg/mL in the original solution with a correlation coefficient of 0.9998. The detection limit of the proposed method is 2. lng/mL in the original solution （3σ, n=9）. Determination of copper in standard ions showed that the proposed method has good accuracy （recovery was more than 95%）. The method was successfully applied for recovery and determination of copper in cereals food samples     

Determination of Trace Amounts of Vanadium by Kinetic-Catalytic Spectrophotometric Methods

Kinetic-catalytic spectrophotometric methods were proposed for the determination of trace amounts of vanadium element as vanadium（Ⅳ） and/or V（Ⅴ） ions. The vanadium（Ⅳ） as VO^2＋ ion and/or vanadium（Ⅴ） as VO3^- ion showed a catalytic effect on the kinetic reactions between a color reagent such as methylthymol blue （MTB） or SPADNS and bromate in acidic media. The rate of decrease in the absorbance of the reagent MTB at 440 nm or SPADNS at 510 nm was proportional to concentration of V（Ⅳ） and/or V（Ⅴ） ions in the solution. The linear ranges for determination of vanadium were obtained in the range of 1.0-150 and 5.0-100.0 μg/L by the fixed-time and slope methods, respectively, with using MTB as reagent. In the presence of SPADNS as reagent, the calibration curves were made in the amplitude 1.0-200.0 and 5.0-150 μg/L of vanadium ion by the fixed-time and slope methods, respectively. Using fixed-time method, the limits of detection were obtained to be 0.5 and 0.7 μg/L of vanadium in the presence of MTB and SPADNS as reagents, respectively. Detection limits of vanadium by slope method and reagents of SPADNS and MTB were obtained to be 3.5 and 3.8 μg/L of vanadium, respectively. The proposed methods were applied successfully to determination of vanadium in synthetic and real samples.     

Studies on Fragmentation Regularity of 5-Methoxycarbonyl-4-substit uted-6-methyl-3,4-dihydropyrimidin-2（1H）-ones by Time-of-flight Mass Spectrometry

The electron impact time-of-flight(TOF) mass spectra of the title compounds were studied to establish their fragmentation processes. With the high resolution of the TOF instrument, the exact mass for each fragment was determined. These data were used to infer the molecular formulas and the elemental compositions for all the molecular ions and fragments through software interpretation. By further applying the fragmentation regularity, the majority of ions were fully assigned. The main fragmentation pathways of the title compounds include the formation of molecular ions by the loss of R^1 groups in the 4-position and the ester groups in the 5-position. The formed ion can be further fragmented by the elimination of MeOH.     

Determination of multiple phenolic compounds in infant textile products by derivatization gas chromatography-mass spectrometryEI北大核心CSCD

A method for the simultaneous determination of 17 phenolic compounds in infant textile products， including phenol，o-phenylphenol，alkylphenols and bisphenols，was established using gas chromatography-mass spectrometry（GC-MS）. The samples were extracted by 0.1 mol/L KOH solution，derived with acetic anhydride. The derivatives were extracted with ethyl acetate，separated by HP-5MS column，and determined by gas chromatography-mass spectrometry with ion mode scanning. Under the optimized conditions，the method had a good linear relationship in the range of 0.5-6.25 mg/L（R2>0.9990），the recoveries ranged from 80% to 110%， the relative standard deviations were 1.0%-8.6%，and the limit of quantification was 1.0 mg/kg. The method can achieve the simultaneous detection of 17 phenolic compounds in infant textile products. © 2023, Youke Publishing Co., Ltd. All rights reserved.     

Determination of eugenol and isoeugenol in aquaculture water by ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometryEI北大核心CSCD

An analytical method was established for the determination of eugenol and isoeugenol in aquaculture water by ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry UPLC-Q-TOF-MS. Water samples were derivatized with dansyl chloride. The derivatization products were separated on a ThermoAccucore C18 column100 mm×2.1 mm2.6 μµm under gradient elution condition utilizing acetonitrile and 0.1% formic acid as mobile phases. Q-TOF-MS operating in mass data using alternating collision cell energyMSEmode with positive electrospray ionization was used for the identification of analytes. The results showed that the calibration curves for eugenol and isoeugenol were linear in the range of 0.1-20 μµg/L with the correlation coefficientsrhigher than 0.995. Their recoveries in aquaculture water were 83.2%-102% and 91.8%-104%respectivelywith relative standard deviationsRSDsless than 15%. The limits of detection were 0.02 and 0.05 μµg/L and the limits of quantitation were 0.05 and 0.1 μµg/Lrespectively. The method can be applied to the determination of eugenol and isoeugenol in real water samples. © 2022, Youke Publishing Co.,Ltd. All rights reserved.     

Determination of Tetracyclines in Honey Using Liquid Chromatography with Ultraviolet Absorbance Detection and Residue Confirmation by Mass Spectrometry

A determination method has been optimized and validated for the simultaneous analysis of tetracycline （TC）, oxytetracycline （OTC）, chlortetracycline （CTC） and doxycycline （DC） in honey. Tetracyclines （TCs） were removed from honey samples by chelation with metal ions bound to small Chelating Sepharose Fast Flow columns and eluted with Na2EDTA-Mcllvaine pH 4.0 buffers. Extracts were further cleaned up by Oasis HLB solid-phase extraction （SPE）, while other solid-phase extraction cartridges were compared. Chromatographic separation was achieved using a polar end-capped C 18 column with an isocratic mobile phase consisting of oxalic acid, acetonitrile and methanol. LC with ultraviolet absorbance at 355 nm resulted in the quantitation of all four tetracycline residues from honey samples fortified at 15, 50, and 100 ng/g, with liner ranges for tetracyclines of 0.05 to 2 μg/mL. Mean recoveries for tetracyclines were greater than 50% with R.S.D. values less than 10% （n= 18）. Detection limits of 5, 5, 10, 10 ng/g for oxytetracycline, tetracycline, chlortetracycline and doxycycline, respectively and quantitation limits of 15 ng/g for all the four tetracyclines were determined. Direct confirmation of the four residues in honey （2-50 ng/g） was realized by liquid chromatography-tandem mass spectrometry （LC/MS/MS）. The linear ranges of tetracyclines determined by LC/MS/MS were between 5 to 300 ng/mL, with the linear correlation coefficient r〉 0.995. The limits of detection of 1 to 2 ng/g were obtained for the analysis of the TCs in honey.     

Analysis of volatile compounds in Herba Asari by single-drop micro-extraction gas chromatography mass spectrometry

A rapid headspace single-drop micro-extraction(mix) gas chromatography mass spectrometry(SDMEGC -MS) for the analysis of the volatile compounds in Herba Asari was developed in this study.A mixed solvent of n-tridecane and butyl acetate(1:1) was finally used for the extraction at 70 C for 15 min with sample amount of 0.750 g and 100 mesh particle size.Under the determined conditions,the pound samples of Herba Asari were directly applied for the analysis.SDME-GC-MS,SPME-GC-MS and SD-GCMS methods were compared and the results showed that SDME-GC-MS method was a simple, inexpensive and effective way to measure the volatile compounds in Herba Asari and could be used for the analysis of volatile compounds in complex samples.     

Magnetic nanoparticles used in headspace extraction coupled with DSI-GC-IT/MS for analysis of VOCs in dry Traditional Chinese Medicine

A novel magnetic method using polystyrene modified magnetic nanoparticles to perform thermoheadspace extraction was successfully developed for extraction and preconcentration of volatile organic components in dry Traditional Chinese Medicine(TCM) based on gas chromatography-ion trap/mass spectrometry with a Chromato Probe direct sample introduction device. The dried fruit of Amomum testaceum Ridl. was used as the object TCM. The optimum parameters of headspace magnetic solid-phase extraction were investigated, in which desorption solvent ethyl acetate played a key role in this method,and the headspace extraction temperature of 90℃ and the headspace extraction time of 15 min finally decided. Headspace solid-phase microextraction method was also used to analyze volatile compounds in the TCM to compare with the proposed method. The results show that 60 components were identified totally by two methods; most of the low boiling point chemical compounds are isolated by this new method. In this work, an environmental-friendly and cheap analytical method was established, and a new approach to analyze volatile compounds in dry Traditional Chinese Medicine was also provided.     

Qualitative and Quantitative Analysis for the Quality Control of Rhizoma Coptidis by HPLC-DAD and HPLC-ESI-MS

For quality control purpose, an approach of fingerprinting and simultaneous quantification of five major bioactive constituents of Rhizoma Coptidis was established via a high-performance liquid chromatograph coupled with a photodiode array UV detector(HPLC-DAD) and an electrospray ionization mass spectrometer(HPLC-ESI/MS). The compounds were identified on the basis of the comparison of their mass spectra with literature data and those of standard samples and quantified by the HPLC-DAD method. Baseline separation was achieved on an XTerra C 18 column(5 μm, 250 mm×4.6 mm i. d.) with linear gradient elution of formate buffer(consisting of 0.5% formic acid, adjusted to pH=4.5 with ammonia) and acetonitrile(consisting of 0.2% formic acid and 0.2% triethylamine). The me-thod was validated for linearity(r 2 0.9995), repeatability(RSD3.1%), intra-and inter-day precision(RSD1.8%) with recovery(99.9%―105.1%), limits of detection(0.15―0.35 μg/mL), and limits of quantification(0.53―0.82 μg/mL). The similarities of 32 batches of Rhizoma Coptidis and their classification according to their manufacturers were based on the retention time and peak areas of the characteristic compounds. The five compounds were selected for quality assessment of Rhizoma coptidis via partial least squares analysis(PLS).     

高效液相色谱对聚醚砜低聚物及其单体组分的分离与测定

In this work, the condition for the analysis of title compounds by HPLC was chosen.The componentcontent and average molecular weight of some kinds of poly(ether-sulfone)s oligomers were determined suc-cessfully. The optimum condition for the partial hydrolysis reaction from 4,4'-dichlorodiphenylsulfone to 4-chloro-4'-hydroxyldiphenylsulfone was obtained.In addition,the constituent changes of the oligomer can beobserved and determined by this method in the polymerization process.     

Determination of macrolides in livestock excreta by syringe purification coupled with liquid chromatography tandem mass spectrometryEI北大核心CSCD

A method of syringe-dispersive solid-phase extraction combined with ultrahigh performance liquid chromatography with tandem mass spectrometry for the simultanous determination of 10 macrolides in manurebased fertilizers was developed. After extraction with methanol and acetonitrile,the extracts were purified by insyringe dispersion solid-phase extraction in syringes pre-filled with 60 mg PSA and 30 mg C18. The resulted extracts were further separated by a BEH C18 column,detected by multiple reaction monitoring in electrospray positive ion mode,and quantified by matrix-matched external standard method. The results showed that the recoveries of the target compounds ranged from 70% to 110% at three spiked levels（10,30,and 50 μµg/kg）with the relative standard deviations ranged from 1.4% to 12%. The limits of detection and quantification were 0.57 1.75 and 2.77-5.40 μµg/kg,respectively. This method was suitable for the simultaneous determination of residual macrolides in organic fertilizers. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

On-Fiber Derivatization of SPME Extracts of Phenol, Hydroquinone and Catechol with GC-MS Detection

A gas chromatography-mass spectrometry (GC-MS) method for the simultaneous determination of phenol (PHE), hydroquinone (HQ) and catechol (CAT) in urine was developed and validated. The method was based on the acidic hydrolysis of conjugated phenolic compounds and further extraction of analytes using solid-phase microextraction (SPME). Analytes were extracted by submersing the polar polyacrylate coated fiber (85 μm) into urine (adjusted to pH 3.0 with glacial acetic acid) for 20 min with magnetic stirring. The extracted compounds on the fiber were exposed to hexamethyldisilazane reagent in the vapor phase for 20 min to yield the corresponding trimethysililylated derivates. This on-fiber derivatization procedure allowed the formation of more amenable compounds for GC analysis, without adversely affecting the lifetime of the fiber. The MS was operated in the selected ion monitoring mode (SIM). The limits of detection were 0.3 μg mL⁻¹ for PHE, 0.15 μg mL⁻¹ for HQ and 0.02 μg mL⁻¹ for CAT. Inter and intra-assay precisions were also verified (coefficient of variation < 8%) with the use of deuterated internal standards. This method of GC-MS analysis can be readily utilized to monitor PHE and its metabolites (HQ and CAT) in urine samples.     

LC-MS analysis of the formed peptides from N-(O,O-diiso-propyl)phosphoryl aspartic acid

LC-ESI-MS method was used to analyze the formed di-and tri-peptide hi the reaction system of N-(O,O-diisopropyl)phosphoryl aspartic acid and adenosine.Ouster ions of the peptides were given hi the ESI-MS.The structures of these small peptides were confirmed by LC-MS-MS analysis.Compared with the traditional HPLC-UV detection,this method showed good sensitivity and selectivity for peptide in the presence of compounds with strong UV absorption,such as nucle-oside and nucleotide.     

Determination of captopril in pharmaceutical preparation and biological fluids using two- and three-way chemometrics methods

Spectrophotometric method has been developed for the direct quantitative determination of captopril in pharmaceuticalpreparation and biological fluids(human plasma and urine)samples.The method was accomplished based on parallel factoranalysis(PARAFAC)and partial least squares(PLS).The study was carried out in the pH range from 2.0 to 12.8 and with aconcentration from 0.70 to 61.50 μg mL~(-1)of captopril.Multivariate calibration models such as PLS at various pH and PARAFACwere elaborated from ultraviolet spectra deconvolution and captopril determination.The best models for this system were obtainedwith PARAFAC and PLS at pH 2.0.The applications of the method for determination of real samples were evaluated by analysis ofcaptopril in pharmaceutical preparations and biological fluids with satisfactory results.The accuracy of the method,evaluatedthrough the RMSEP,was 0.5801 for captopril with best calibration curve by PARAFAC and 0.6168 for captopril with PLS at pH 2.0model.