Comparison of gas chromatographic hyphenated techniques for mercury speciation analysis

In this study, we evaluate advantages and disadvantages of three hyphenated techniques for mercury speciation analysis in different sample matrices using gas chromatography (GC) with mass spectrometry (GC-MS), inductively coupled plasma mass spectrometry (GC-ICP-MS) and pyrolysis atomic fluorescence (GC-pyro-AFS) detection. Aqueous ethylation with NaBEt(4) was required in all cases. All systems were validated with respect to precision, with repeatability and reproducibility <5% RSD, confirmed by the Snedecor F-test. All methods proved to be robust according to a Plackett-Burnham design for 7 factors and 15 experiments, and calculations were carried out using the procedures described by Youden and Steiner. In order to evaluate accuracy, certified reference materials (DORM-2 and DOLT-3) were analyzed after closed-vessel microwave extraction with tetramethylammonium hydroxide (TMAH). No statistically significant differences were found to the certified values (p=0.05). The suitability for water samples analysis with different organic matter and chloride contents was evaluated by recovery experiments in synthetic spiked waters. Absolute detection and quantification limits were in the range of 2-6 pg for GC-pyro-AFS, 1-4 pg for GC-MS, with 0.05-0.21 pg for GC-ICP-MS showing the best limits of detection for the three systems employed. However, all systems are sufficiently sensitive for mercury speciation in environmental samples, with GC-MS and GC-ICP-MS offering isotope analysis capabilities for the use of species-specific isotope dilution analysis, and GC-pyro-AFS being the most cost effective alternative.     

固相萃取-GC-MS法测定饲料中的沙丁胺醇

沙丁胺醇(salbutamol),化学名称1-(4-羟基-3-羟甲基苯基)-2-(叔丁氨基)乙醇(结构式如图1所示),俗称舒喘宁,属于β-兴奋剂类药物的一种,临床上用于治疗支气管哮喘。同时沙丁胺醇同克伦特罗(瘦肉精)一样还具有提高饲料的转化率,促进动物生长的作用。但是,这种药物容易在动物内     

Polymer architectures via mass spectrometry and hyphenated techniques: A review

This review covers the application of mass spectrometry (MS) and its hyphenated techniques to synthetic polymers of varying architectural complexities. The synthetic polymers are discussed as according to their architectural complexity from linear homopolymers and copolymers to stars, dendrimers, cyclic copolymers and other polymers. MS and tandem MS (MS/MS) has been extensively used for the analysis of synthetic polymers. However, the increase in structural or architectural complexity can result in analytical challenges that MS or MS/MS cannot overcome alone. Hyphenation to MS with different chromatographic techniques (2D × LC, SEC, HPLC etc.), utilization of other ionization methods (APCI, DESI etc.) and various mass analyzers (FT-ICR, quadrupole, time-of-flight, ion trap etc.) are applied to overcome these challenges and achieve more detailed structural characterizations of complex polymeric systems. In addition, computational methods (software: MassChrom2D, COCONUT, 2D maps etc.) have also reached polymer science to facilitate and accelerate data interpretation. Developments in technology and the comprehension of different polymer classes with diverse architectures have significantly improved, which allow for smart polymer designs to be examined and advanced. We present specific examples covering diverse analytical aspects as well as forthcoming prospects in polymer science.     

Detection in urine of efaproxiral (RSR13), a potential doping agent, by a routine screening procedure based on methylation followed by gas chromatography/mass spectrometry

Efaproxiral (also known as RSR13) is a synthetic allosteric modifier of hemoglobin. The ability to increase maximal muscle oxygen uptake makes RSR13 a potential performance-enhancing agent for athletes and, therefore, a new agent to be taken into account by the antidoping control laboratories. In this work, a new method for the detection of efaproxiral in urine by gas chromatography/mass spectrometry is described.     

Optimization of capillary SFC-MS for the determination of additives in polymers

A standard direct introduction capillary interface is used for the SFC-MS analysis of polymer additives. The system is optimized with respect to the position of the restrictor, probe tip temperature, and ion source temperature. El-like charge-exchange spectra are obtained. Cl using ammonia as the reagent gas is used for the quantitative analysis of a real world sample. The experimental capillary SFC-MS spectra obtained show a good similarity with those recorded using the direct insertion probe. The influence of the experimental conditions on the mass spectra obtained is evaluated statistically.     

A fully validated method for the determination of lacosamide in human plasma using gas chromatography with mass spectrometry: Application for therapeutic drug monitoring

A simple gas chromatographic method with mass spectrometry detection was developed and validated for the determination of lacosamide in human plasma. Lacosamide and the internal standard, levetiracetam‐d₆, were extracted from 200 μL plasma, by a solid‐phase extraction through HF Bond Elut C₁₈ columns, and derivatized using N‐methyl‐N‐tert‐butyldimethylsilyltrifluoroacetamide with 1% tert‐butyldimethylsilylchloride in acetonitrile. The limit of quantification was found to be 0.20 μg/mL and the assay was linear up to 20.0 μg/mL with correlation coefficient ≥0.994. The intra‐ and interday precision values were <4.1% in terms of relative standard deviation (%) and the values of intra‐ and interday accuracy were found to be within –7.2 and 5.3% in terms of relative error (%). Absolute recovery of the method for lacosamide was determined at three concentration levels and ranged from 92.5 to 97.6%. The developed method uses small volumes of plasma and proved to be simple, rapid, and sensitive for the determination of lacosamide in plasma. This method can be used in routine every day analysis of plasma samples obtained from patients who follow respective antiepileptic treatment and for the investigation of clinical and forensic cases where lacosamide is involved.     

Nano-liquid chromatography and capillary electrochromatography hyphenated with mass spectrometry for tryptic digest protein analysis: A comparison

Nano-LC and CEC were studied for the separation of cytochrome c tryptic digest. The peptides mixture was analyzed using either a nano-LC commercial or a laboratory assembled instrumentation coupled with an IT-ESI-MS by using a nanospray interface. CEC experiments were carried out with a CE apparatus coupled with the IT-ESI-MS through a liquid junction interface. Analytes were separated utilizing C18 silica based stationary phases, of different properties and origin, silica derivatized with cyano groups and C18 monolithic material. The last column, just because the chemical composition (absence of charged/chargeable groups) was tested only using nano-LC. Best results mainly related to the highest number of peptides separated and column equilibration time were obtained by nano-LC employing the C18 stationary phase (detection of 20 peptides, coverage of 88%). Similar results were achieved using both commercial and laboratory assembled instrumentation. The use of CEC revealed a higher separation efficiency and shorter analysis time. However, the number of separated peptides were lower than those observed in nano-LC. In CEC the use of capillaries packed with cyanosilica particles offered better results; however, less satisfactory than those observed in the miniaturized LC technique. Provided the use of the same stationary phase and taking into account the driving forces, the two techniques can be considered complementary, offering different information related to the retention times of the studied peptides.     

Development and validation of a gas chromatography-mass spectrometric method for the determination of sildenafil and desmethyl-sildenafil in whole blood

Sildenafil (SDL) is a phosphodiesterase type 5 inhibitor and it is approved for the treatment of erectile dysfunction and pulmonary hypertension. SDL is extensively metabolized to its pharmacologically active metabolite, desmethyl‐sildenafil (DSDL). A sensitive and specific GC/MS method for the determination of SDL and DSDL in whole blood was developed and validated to support therapeutic drug monitoring of SDL patients. The combination of solid‐phase extraction with derivatization using BSTFA with 1% TMCS in acetonitrile efficiently reduced matrix effect and improved sensitivity of the method. In this assay, protriptyline was used as internal standard for both analytes. The LODs were 1.50 and 5.00 ng/mL for SDL and DSDL, respectively, whereas the respective LOQs were 5.00 and 15.0 ng/mL. The calibration curves were linear up to 500.0 ng/mL (SDL: R² 0.992, DSDL: R² 0.990). Absolute recovery values for both analytes ranged from 83.1 to 93.2%. Within‐ and between‐batch accuracy was less than 11.8 and 10.2%, respectively, whereas within‐ and between‐batch precision was less than 8.1 and 10.8%, correspondingly. The developed method is suitable for the determination of SDL and DSDL concentrations in blood samples obtained from patients under Viagra^® treatment, for pharmacokinetic studies or for the investigation of related forensic cases.     

Validation of a confirmatory method for the determination of melamine in egg by gas chromatography-mass spectrometry and ultra-performance liquid chromatography-tandem mass spectrometry

A sensitive and reliable method was developed and validated for detection and confirmation of melamine in egg based on gas chromatography-mass spectrometry (GC-MS) and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Trichloroacetic acid solution was used for sample extraction and precipitation of proteins. The aqueous extracts were subjected to solid-phase extraction by mixed-mode reversed-phase/strong cation-exchange cartridges. Using ultra-performance liquid chromatography and electrospray ionization in the positive ion mode, melamine was determined by LC-MS/MS, which was completed in 5 min for each injection. For the GC-MS analysis, extracted melamine was derivatized with N,O-bis(trimethylsilyl)trifluoracetamide prior to selected ion monitoring detection in electron impact mode. The average recovery of melamine from fortified samples ranged from 85.2% to 103.2%, with coefficients of variation lower than 12%. The limit of detection obtained by GC-MS and UPLC-MS/MS was 10 and 5 μg kg⁻¹, respectively. This validated method was successfully applied to the determination of melamine in real samples from market.     

Analysis of fragrances in cosmetics by gas chromatography–mass spectrometry

A gas chromatographic (GC)-mass spectrometric (GC-MS) method has been developed for the routine analysis of 11 fragrance substances in cosmetics: cinnamic alcohol, cinnamic aldehyde, eugenol, hydroxy citronellal, α-amyl cinnamic aldehyde, geraniol, isoeugenol, coumarin, dihydrocoumarin, citronellal and citral. Methods for sample preparation of various types of cosmetic products, prior to GC analysis, have also been developed and proved to be rugged. Detection limits of all of target fragrance substances were approximately 1 ppm. Calibration curves of the target fragrance substances analyzed by GC were found to be linear in the investigated concentration range, 0.005% – 0.50%. The recoveries of the target fragrances from various types of cosmetic products were 80% – 116% and the relative standard deviations of the quantitative analysis of the target fragrance substances were within 5%.     

GC-MS法分析肼类燃料中的杂质成分及氧化产物

应用气相色谱-质谱联用法对肼类燃料进行了定性分析,确定了3种肼类燃料的杂质和氧化产物,并对偏二甲肼氧化产物的产生及发黄机理进行了初步探讨。     

Cost effective,robust, and reliable coupled separation techniques for the identification and quantification of phospholipids in complex biological matrices: Application to insects

The quantification of phospholipid classes and the determination of their molecular structures are crucial in physiological and medical studies. This paper's target analytes are cell membrane phospholipids, which play an important role in the seasonal acclimation processes of poikilothermic organisms. We introduce a set of simple and cost‐effective analytical methods that enable efficient characterization and quantification of particular phospholipid classes and the identification and relative distribution of the individual phospholipid species. The analytical approach involves solid‐phase extraction and high‐performance thin‐layer chromatography, which facilitate the separation of particular lipid classes. The obtained fractions are further transesterified to fatty acid methyl esters and subjected to gas chromatography coupled to flame ionization detection, which enables the determination of the position of double bonds. Phospholipid species separation is achieved by high‐performance liquid chromatography with mass spectrometry, which gives information about the headgroup moiety and attached fatty acids. The total content of each phospholipids class is assessed by phosphorus determination by UV spectrophotometry. The simultaneous analysis of phosphorus, fatty acid residues, and phospholipid species provides detailed information about phospholipid composition. Evaluation of these coupled methods was achieved by application to an insect model, Pyrrhocoris apterus. High correlation was observed between fatty acid compositions as determined by gas chromatography and high‐performance liquid chromatography analysis.     

测定饲料中喹乙醇含量的反相高效液相色谱法

建立了高效液相色谱法测定饲料中喹乙醇含量的方法 ;饲料用甲醇 -水提取 ,在380nm波长下检测 ,色谱柱为NOVA_PakC18(3.9mm×150mm ,4μm) ,流动相为甲醇 -水 (体积比为10∶90) ,流速为1.0mL/min ,喹乙醇质量浓度在2.5～20.0mg/L范围内与峰面积呈良好线性关系 ,相对标准偏差为1.2 %～1.6 % ,回收率为97 %～101%。     

灰化法气相色谱/质谱法测定奶粉中碘的研究

采用气相色谱-质谱联用技术建立了一个快速、高灵敏测定奶粉中碘的新方法.用碱灰化法处理样品,丁酮衍生后用正己烷提取,无水硫酸钠脱水,HP-5MS柱气相色谱分离后用质谱在选择离子模式下测定,外标法定量.该方法的回收率在77%～110%之间,相对标准偏差小于10%,检出限为0.1 mg/kg.实验表明氯离子、溴离子都不干扰测定,方法的选择性好.     

Evolution of hyphenated techniques for mineral oil analysis in food

The occurrence of mineral oil in food is known since the early 1990s, and it was discovered by chance in one of the first applications using the hyphenated LC–GC system. Since then, the relationship between hyphenated techniques and mineral oil analysis has been tightly interrelated and successful. This review aims to show and explain how this mutual interaction has driven the development of the hyphenated techniques on one side and has supported the increase of knowledge on the other, supporting the complex task of mineral oil determination in food. The paper presents the background of the mineral oil problem in food (a brief history of its finding, toxicology, and occurrence), moving then toward the analytical determination. The development of different hyphenated techniques in relation to mineral oil determination is discussed, focusing mainly on 2D techniques, such as LC–GC. The necessity of additional dimensions, such as LC–LC–GC and comprehensive approaches, such as GC × GC and LC × GC, is also discussed. Finally, the role of the hyphenation with MS is presented.