Determination of lincomycin and tylosin residues in honey using solid-phase extraction and liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

An analytical method for the determination of residues of the antibiotic drugs lincomycin and tylosin in honey was developed. The procedure employed a solid-phase extraction for the isolation of lincomycin and tylosin from diluted honey samples. The antibiotic residues were subsequently analyzed by reversed-phase HPLC with atmospheric pressure chemical ionization mass spectrometric detection. Average analyte recoveries for lincomycin and tylosin ranged from 84 to 107% in replicate sets of honey samples fortified with drug concentrations of 0.01, 0.5, and 10 microg/g. The method detection limits were determined to be 0.007 and 0.01 microg/g for lincomycin and tylosin, respectively.     

Monitoring of antifouling agents in water samples by on-line solid-phase extraction-liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

An automatic method for determining diuron, irgarol 1051, folpet and dichlofluanid in seawater samples have been developed. This method is based on the on-line coupling of solid-phase extraction (SPE) with a highly crosslinked polymeric sorbent, LiChrolut EN, to liquid chromatography followed by atmospheric pressure chemical ionization (APCI) and mass spectrometry. The operational parameters affecting the APCI interface have been studied in both positive and negative ionization modes. The use of LiChrolut EN in the SPE produced recoveries of over 85% for all the compounds when 100 ml of seawater sample was preconcentrated. Calibration was carried out in both ionization modes and in full-scan and selected-ion monitoring (SIM). The method allowed all the analytes to be detected at 5 ng l(-1) in SIM acquisition mode except folpet, which, because of its low response, could only be detected at 250 ng l(-1). The method was used to analyse water samples taken from five different marina and fishing ports along the coast of Tarragona, Catalonia (Spain), over a 5-month period. Diuron and irgarol 1051 were detected and quantified in most samples at concentration levels ranging from 27 to 420 ng l(-1) for diuron and from 15 to 511 ng l(-1) for irgarol 1051.     

Part-per-trillion level determination of antifouling pesticides and their byproducts in seawater samples by off-line solid-phase extraction followed by high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

A new method for the simultaneous determination of antifouling pesticides and some of their byproducts such as dichlofluanid, diuron and its byproducts [demethyldiuron and 1-(3,4-dichlorophenyl)urea], (2-thiocyanomethylthio)ben: zothiazole, chlorothalonil, Sea-nine 211, Irgarol 1051 and one of its byproducts (2-methylthio-4-tert.-butylamino-s-triazine) in seawater was developed. The extraction of these compounds from the filtered seawater samples was performed off-line with different solid-phase extraction sorbents using (I) a 500 mg graphitized carbon black cartridge (ENVI-Carb) and (II) 200 mg polymeric cartridges (LiChrolut EN and Isolute ENV+) and passing 500 ml of the sample through these cartridges. The detection was carried out by reversed-phase high-performance liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometry both in the negative and positive ion modes. The recovery ranged from 76 to 96% for the whole antifouling group with the ENVI-Carb cartridges and the detection limit was at the part-per-trillion level except for TCMTB. The method utilizing the polymeric cartridge proved to be very useful, time saving and with good recoveries when only Irgarol and its byproduct, Sea-nine 211 and diuron and its byproducts, have to be analyzed. The different cartridges were applied to the analysis of these pesticides in different marinas of the Catalan coast; diuron, dichlofluanid, Sea-nine 211, Irgarol as well as demethyldiuron and the Irgarol byproduct being the must ubiquitous pollutants. Maximum concentration levels were 2-3.5 microg/l of diuron and Sea-nine 211, respectively.     

Screening of organophosphorus pesticides using liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

Screening and identification of organophosphorus pesticides in blood from patients suffering from acute agricultural chemical toxicity were established by a liquid chromatography-atmospheric pressure chemical ionization mass spectrometric method. To determine 21 pesticides, it was necessary to monitor both positive and negative ions. This method could easily screen for 21 organophosphorus pesticides in less than 30 min. By comparison with a gas chromatographic-mass spectrometric method, the chemicals indicated a similar extent of specificity and within equivalent detection limits, thus satisfying clinical requirements completely.     

Stability studies of propoxur herbicide in environmental water samples by liquid chromatography-atmospheric pressure chemical ionization ion-trap mass spectrometry

Liquid chromatography-atmospheric pressure ionization ion-trap mass spectrometry has been investigated for the analysis of polar pesticides in water. The degradation behavior of propoxur, selected as a model pesticide belonging to the N-methylcarbamate group, in various aqueous matrices (Milli-Q water, drinking water, rain water, seawater and river water) was investigated. Two interfaces of atmospheric pressure ionization, atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI), were compared during the study. Propoxur and its transformation product (N-methylformamide) were best ionized as positive ions with both APCI and ESI, while another transformation product (2-isopropoxyphenol) yielded stronger signals as negative ions only with APCI. In addition, the effects of various pH, matrix type and irradiation sources (sunlight, darkness, indoor lighting and artificial UV lamp) on the chemical degradation (hydrolysis) were also assessed. From the kinetic studies of degradation, it was found that the half-life of propoxur was reduced from 327 to 161 h in Milli-Q water with variation of irradiation conditions from dark to sunlight exposure. Degradation rates largely increased with increasing pH. The half-life of the target compound dissolved in Milli-Q water under darkness decreased from 407 to 3 h when the pH of Milli-Q water was increased from 5 to 8.5. These suggest that hydrolysis of propoxur is light-intensity and pH-dependent. In order to mimic contaminated natural environmental waters, propoxur was spiked into real water samples at 30 microg/l. The degradation of propoxur in such water samples under various conditions were studied in detail and compared. With the ion trap run in a time-scheduled single ion monitoring mode, typical limits of detection of the instrument were in the range of 1-10 microg/l.     

Monitoring of priority pesticides and other organic pollutants in river water from portugal by gas chromatography-mass spectrometry and liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

Gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (LC-APCI-MS) were optimized and applied for the trace-level determination of 42 priority pesticides and 33 priority organic pollutants from European Union Directive EC 76/464. First, off-line solid-phase extraction of 200 ml of river water using an OASIS solid-phase extraction cartridge, followed by GC-MS was used. Next, selected samples that were positive to GC-MS were analyzed by LC-APCI-MS in order to detect further polar byproducts or to improve the determination of previously detected polar analytes. The transformation products of triazine pesticides like deethylatrazine (DEA) and deisopropylatrazine (DIA) and compounds such as diuron and several chlorophenols were positively identified by LC-APCI-MS. The present methodology has also been used for searching for new analytes not included in the EC 76/464 list, like Irgarol, DEA and DIA. In addition it was applied to target pollutants in 43 river water samples from Portugal during a pilot survey from April to July 1999. Atrazine followed by simazine and 2,4,6-trichlorophenol were the most ubiquitous compounds detected in this area. The levels detected of the different compounds were in the range of: 0.01-2.73 microg/l, 0.05-0.74 microg/l, 0.02-1.65 microg/l, 0.02-5.43 microg/l, 0.01-0.40 microg/l, 0.01-0.26 microg/l, 0.02-0.61 microg/l, 0.01-3.90 microg/l, 0.01-1.24 microg/l, 0.02-2.3 microg/l, 0.01-0.13 microg/l and 0.01-0.5 microg/l for atrazine, simazine, terbuthylazine, alachlor, metolachlor, Irgarol, propanil; tributhylphosphate, diuron, 2,4,6-trichlorophenol, deisopropylatrazine and deethylatrazine, respectively.     

Determination of patulin in apple juice by high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

An HPLC-MS-MS method with selected reaction monitoring (SRM) for the determination of patulin in apple juice samples is described. Mass spectrometric detection was accomplished following atmospheric pressure chemical ionization (APCI) in both positive and negative ion modes. Collision induced dissociation (CID) of the protonated molecular ion led initially to the loss of H2O (fragment m/z 137). At higher energies CO is lost from both the protonated parent molecule (fragment m/z 127) and the dehydrated molecular ion (fragment m/z 109). In contrast, CID of the deprotonated molecular ion led initially to the fragment at m/z 109 corresponding to the loss of either CO2 or acetaldehyde, followed at higher CID energy by the loss of H2O (fragment m/z 135) and CO (fragment m/z 125) from the deprotonated molecular ion. Detection in the negative ion mode proved superior and a linear response was observed over the injected range from 6 to 200 ng patulin. Apple juice samples spiked with patulin between 10 and 135 microg/l were analyzed following liquid-liquid extraction with ethyl acetate and clean up with sodium carbonate. Utilizing reversed-phase HPLC with acetonitrile-water (10:90) at 0.5 ml/min, levels down to 10 microg/l were readily quantified and a detection limit of 4 microg/l was attainable at a signal-to-noise (SIN) ratio of 4. The MS data for the spiked samples compared well to the UV data and when plotted against each other displayed a correlation coefficient (R) of 0.99.     

超高效液相色谱-大气压化学电离-串联质谱法测定烘焙咖啡中丙烯酰胺

建立了烘焙咖啡中丙烯酰胺的超高效液相色谱-大气压化学电离-串联质谱（UHPLC-APCI-MS/MS）分析方法。样品经甲醇提取，HLB固相萃取（SPE）小柱净化，Brownlee validated AQ C18色谱柱分离，采用大气压化学电离（APCI）源，正离子扫描和多反应监测（MRM）模式对丙烯酰胺进行检测，内标法定量。结果表明，丙烯酰胺在0.5~100.0 μg/L范围内具有良好的线性关系，相关系数（r²）为0.999，方法检出限为5.0 μg/kg，定量限为10.0 μg/kg。在100.0、200.0和1000.0 μg/kg添加水平下，丙烯酰胺的回收率为94.6%~115.0%，相对标准偏差（RSD）值为2.8%~3.6%（n=6）。本方法采用APCI源作为离子化方式，能有效地减少咖啡基质对丙烯酰胺的基质干扰，前处理简单，灵敏度高，适用于咖啡中丙烯酰胺的日常检测。     

Comparative analysis of different plant oils by high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

This work focused on the way several electrolyte components could affect the electroosmotic flow and the capillary electrophoretic migration of aliphatic or aromatic (hydroxy)carboxylic acids. The effects exerted by the electroosmotic flow modifier, hexadecyltrimethylammonium bromide, the addition of metal salt to the electrolyte and the absorbance provider (chromophore) used for indirect detection were investigated. A retention of the organic acids was demonstrated. Its magnitude was shown to depend on the amount of cationic surfactant adsorbed onto the capillary walls. The addition of sodium nitrate led to a remobilization of all the acids except glycolic acid. Moreover, the presence of the chromophore was shown to influence mainly the migration of the glycolic acid.     

Determination of azolic fungicides in wine by solid-phase extraction and high-performance liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry

A method for simultaneous analysis of eight azolic fungicides: cyproconazole, diniconazole, tetraconazole, thiabendazole, flusilazole, triadimenol, triadimefon, carbendazim and the degradation product 2-aminobenzimidazole in wine samples is described. The compounds are isolated from the samples and concentrated by solid-phase extraction on polymeric cartridges. The determination is carried out by liquid chromatography with mass spectrometric detection in positive ionization and selected ion monitoring modes. The influence of parameters such as the mobile phase composition, column temperature, corona current and fragmentor voltage is studied and the proposed method is validated. Recoveries of the nine compounds added to wine samples range from 83 to 109%, with relative standard deviations below 10%. The quantitation limits are between 9 and 31 microg/L. Real wine samples are analyzed by the proposed method, also.     

银离子高效液相色谱-质谱法分析血清中甘油三酯类化合物的组成

针对甘油三酯(TAG)类化合物的复杂性,建立了分析小鼠血清中TAG类化合物的方法。采用经典的氯仿-甲醇溶剂体系对血中的TAG类化合物进行提取。脂质提取物经Varian ChromSpher 5 Lipids柱分离,在0.75 mL/min的流速下以乙腈-正己烷(1:99, v/v)为流动相进行等度洗脱,采用大气压化学电离源正离子模式电离,质谱增强型全扫描、增强型子离子扫描和中性丢失扫描模式检测。根据银离子色谱对双键的保留规律以及质谱所给出的碎片离子信息,对血清中TAG类化合物进行了结构鉴定。结果表明采用该方法可以从小鼠血清中鉴定到66个TAG类化合物以及5个胆固醇酯。该方法简单,重现性好,可通用于其他样品中TAG类化合物的检测。     

Quantitative determination of four nitrofuran metabolites in meat by isotope dilution liquid chromatography-electrospray ionisation-tandem mass spectrometry

A confirmatory method based on isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed for the low-level determination of residues of four nitrofuran veterinary drugs in meat, e.g., furazolidone, furaltadone, nitrofurantoin, and nitrofurazone. The procedure entails an acid-catalysed release of protein-bound metabolites, followed by their in situ conversion into the 2-nitrobenzaldehyde (NBA) imine-type derivatives. Liquid-liquid extraction and clean-up on a polymeric solid phase extraction cartridge are then performed before LC-MS/MS analysis by positive electrospray ionisation (ESI) applying multiple reaction monitoring of three transition reactions for each compound. Reliable quantitation is obtained by using one deuterated analogue per analyte (d4-NBA derivative) as internal standard (IS). Validation of the method in chicken meat was conducted following the European Union (EU) criteria for the analysis of veterinary drug residues in foods. The decision limits (CCalpha) were 0.11-0.21 microg/kg, and the detection capabilities (CCbeta) 0.19-0.36 microg/kg, thus below the minimum required performance limit (MRPL) set at 1 microg/kg by the EU. The method is robust and suitable for routine quality control operations, and more than 200 sample injections were performed without excessive pollution of the mass spectrometer or loss of LC column performance.     

Application of liquid chromatography-atmospheric pressure chemical ionization mass spectrometry to the differentiation of stereoisomeric diterpenoid alkaloids

High-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (HPLC-APCI-MS) was successfully applied to seven stereoisomeric diterpenoid alkaloids at position 1 or 12. Comparison of the breakdown curves, observed by changing the potential difference between the first electrode and the second electrode of the APCI ion source, revealed stereochemical dependence of different fragmentations. The APCI spectra of alkaloids were predominantly the [M+H]+ ion and the major fragment ion, corresponding to the [M+H-H2O]+ ion or the [M+H-CH3COOH]+ ion, and comparison of the APCI spectra showed that the abundance of fragment ions was significantly higher for C-1 beta-form alkaloids than for C-1 alpha-form alkaloids, and for C-12 beta-form alkaloids than for C-12 alpha-form alkaloids. The characteristic fragment ions were formed due to the loss of an acetic acid or a water molecule at position 12. The fragmentation mechanisms depending on the stereochemistry of the precursor ion could be discerned by recording the spectra in a deuterated solvent system of 0.05 M ammonium acetate in D2O-acetonitrile-tetrahydrofuran. Loss of CH3COOD or D2O from the precursor ion gave the fragment ion. This result indicated that the proton of protonation was included in the leaving acetic acid and water molecule, respectively. The peak intensity ratio for R=[M+H]+/[M+ H-H2O]+ + [M + H-CH3COOH] + manifested the stereochemical differentiation of alkaloids at position 1 or 12.     

A fast method for determining low-molecular-mass aliphatic carboxylic acids by high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

A fast quantitative high-performance liquid chromatographic separation method with atmospheric pressure chemical ionization mass spectrometric detection (HPLC-APCI-MS) was developed for the determination of low-molecular-mass aliphatic mono- and dicarboxylic acids typically present in different industrial process waters. A mixture of glycolic, lactic, a-glucoisosaccharinic, oxalic, maleic, fumaric, succinic, malic, glutaric, methylsuccinic, and adipic acids was separated using an RP chromatographic system. Adipic acid was used as an internal standard to calculate correlation coefficients for the acids studied. The chromatographic analysis of these acids was primarily carried out by means of gradient elution with an aqueous formic acid solution (0.15%, pH 2.5) and methanol using a modified C18 stationary phase. Good acid separation could be obtained for all acids by optimizing the chromatographic conditions. The method provides a simple sample preparation and faster analysis time compared to the traditional gas chromatographic methods, thus enabling almost real-time monitoring of these acids. Finally, the method developed was applied to the analysis of a complex mixture of aliphatic hydroxy carboxylic acids, which are formed as alkaline degradation products of carbohydrates during wood delignification and are present in the cooking spent liquor (black liquor).     

Identification of ubiquinones and menaquinones in activated sludge by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

A sensitive analytical method has been developed for identification of ubiquinones (UQ-n(Hx)) and menaquinones (MK-n(Hx)) in activated sludge by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry in negative mode (LC-NI-APCI-MS). Extraction and clean-up of samples were carried out on Sep-Pak Plus Silica solid-phase extraction cartridges. Complete separation of quinones was achieved with an ODS analytical column and using isopropyl ether-methanol (17:83, v/v) as the mobile phase. The compositions of ubiquinones and menaquinones were determined directly using combined information on retention time, the molecular ion mass and fragment ion masses. The lowest instrument quantitative detection limits (LODinst) for UQ-6, UQ-10, and Vitamin K1 were estimated to be 0.4, 4 and 0.12 ng (S/N = 10) using LC-NI-APCI-MS in SIM mode, and the lowest method detection limits (LODmeth) achieved by spiking experiment were estimated to be 0.2, 2 and 0.06 microg/g for UQ-6, UQ-10 and Vitamin K1, respectively. On the other hand, the LODinst for UQ-6, UQ-10, and Vitamin K1 were estimated to be 10, 100 and 2 ng (S/N = 10) using LC-NI-APCI-MS in full-scan mode, and the LODmeth were estimated to be 7, 60 and 1.2 microg/g for UQ-6, UQ-10, and Vitamin K1, respectively. Both LC-NI-APCI-MS and LC-UV/DAD were applied in the analysis of an activated sludge extract. UQ-n (n = 6-10), MK-n (n = 6-10), MK-n(H2) (n = 7-10), MK-n(H4) (n = 8-9) and MK-8(H6) were detected by LC-NI-APCI-MS, while UQ-6, UQ-7, MK-7(H), MK-9 and MK-10(H2) were not found by LC-UV/DAD. These results suggest that LC-NI-APCI-MS is more sensitive than LC-UV/DAD for the analysis of quinones in environmental samples such as sediment, activated sludge and bio-film in biological processes and other aquatic environments.     

Determination of fungicide residues in fruits and vegetables by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

A liquid chromatography (LC) method for the quantitative determination of five fungicide residues (dichloran, flutriafol, o-phenylphenol, prochloraz and tolclofos methyl) in oranges, lemons, bananas, peppers, chards and onions is described. The residues were extracted by matrix solid-phase dispersion (MSPD) using C8. Quantitative analysis was performed by isocratic LC coupled to quadrupole mass spectrometer using atmospheric pressure chemical ionization in the negative ionization mode. The limit of quantification was 0.01 mg kgmicro for flutriafol, o-phenylphenol and dichloran, and 0.1 mg kg(-1) for prochloraz and tolclofos methyl. The MSPD method is also suitable for LC-UV analysis but higher limits of quantification (between 1 and 5 mg kg(-1)) were obtained. Validation of the method was performed between 0.01 and 25 mg kg(-1). Recoveries for fungicides ranged from 52.5 to 91.1% with relative standard deviations between 6.1 and 11.9%. The method was applied to the determination of residues in samples taken from agricultural cooperatives. The fungicides most often detected were o-phenylphenol and prochloraz.     

液相色谱-大气压化学电离串联质谱法测定婴幼儿配方奶粉中的维生素D

建立了婴幼儿配方奶粉中维生素D的液相色谱-大气压化学电离串联质谱(LC-APCI-MS/MS)分析方法。样品经正己烷和甲基叔丁基醚混合溶液提取,ProElut VDC固相萃取柱净化,Kinetex C_(18)色谱柱分离,采用大气压化学电离(APCI)源、正离子扫描和多反应监测(MRM)模式对维生素D_2和维生素D_3进行检测,内标法定量。结果表明维生素D_2和维生素D_3在5~5 000μg/L范围内均具有良好的线性关系,检出限为2μg/kg,定量限为5μg/kg。在5、10和100μg/kg添加水平下,维生素D_2和维生素D_3的回收率为85.2%~105.3%,相对标准偏差为4.7%~8.1%。该方法简便准确,灵敏度高,适用于婴幼儿奶粉中维生素D的测定。     

Ion chromatography-atmospheric pressure chemical ionization mass spectrometry for the determination of trace chlorophenols in clam tissues

A novel analytical method has been developed for the determination of 14 trace chlorophenols in clam tissues by ion chromatography (IC) coupled with atmospheric pressure chemical ionization mass spectrometry (APCI-MS) in the negative mode. The method comprised a fast ultrasound-assisted extraction using a mixture of methanol/water (4:1v/v) containing 5% triethylamine (TEA) as extraction solvent, solid-phase extraction with an Oasis HLB cartridge and gradient separation using KOH/acetonitrile at a flow rate of 1.0 mL/min on an IonPac AG11 guard column (50 mm x 4.0 mm I.D.) and an IonPac AS11 analytical column (250 mm x 4.0 mm I.D.). The molecular ions m/z [M-H](-) 127, 129; 161, 163; 195, 197 and 263, 265, 267 were selected for quantification in the selected ion monitoring (SIM) mode for monochlorophenols (MCPs), dichlorophenols (DCPs), trichlorophenols (TCPs) and pentachlorophenol (PCP), respectively. The average recoveries of the objective compounds spiked in clam tissues were between 80.2% and 98.2%. Within-day and day-to-day relative standard deviations were less than 12.6% and 13.2%, respectively. The optimum IC-APCI-MS conditions were successfully applied to the analyses of 14 trace chlorophenols in clam tissues.     

Assay of nicergoline and three metabolites in human plasma and urine by high-performance liquid chromatography-atmospheric pressure ionization mass spectrometry.

A method for the simultaneous determination of nicergoline and three of its metabolites in human plasma and urine has been developed using high-performance liquid chromatography-atmospheric pressure ionization mass spectrometry. Nicergoline and its metabolites were extracted from the plasma and urine samples with chloroform and separated on a reversed-phase ODS column. The eluents were led to the atmospheric pressure ionization interface and then analysed in the selected-ion monitoring mode. The detection limits of nicergoline and three of its metabolites were ca. 2 ng/ml in plasma and ca. 10 ng/ml in urine, at a signal-to-noise ratio of 4.