Development of single‐drop microextraction and simultaneous derivatization followed by GC‐MS for the determination of aliphatic amines in tobacco

In this work, for the first time, headspace (HS) single‐drop microextraction and simultaneous derivatization followed by GC‐MS was developed to determine the aliphatic amines in tobacco samples. In the HS extraction procedure, the mixture of derivatization reagent and organic solvent was employed as the extraction solvent for HS single‐drop microextraction and in situ derivatization of aliphatic amine in the samples. Fast extraction and simultaneous derivatization of the analytes were performed in a single step, and the obtained derivatives in the microdrop extraction solvent were analyzed by GC‐MS. The optimized experiment conditions were: sample preparation temperature of 80°C and time of 30 min, HS extraction solvent (the mixture of benzyl alcohol and 2,3,4,5,6‐pentafluorobenzaldehyde) volume of 2.0 μL, extraction time of 90 s. With the optimal conditions, the method validations were also studied. The method has good linearity (R² more than 0.99), accepted precision (RSD less than 13%), good recovery (98–104%) and low limit of detection (0.11–0.97 μg/g). Finally, the proposed technique was successfully applied to the analyses of aliphatic amines in tobacco samples of seven different brands. It was further demonstrated that the proposed method offered a simple, low‐cost and reliable approach to determine aliphatic amines in tobacco samples.     

LC-MS在体内药物分析方法学研究中常见的问题及其对策

液相色谱-质谱联用技术(liquid chromatography-mass spectrometry,LC-MS)已成为体内药物分析及其相关研究领域中不可或缺的工具.虽然该技术具有高选择性、高灵敏度以及高通量等特点,但在体内药物分析方法学研究中,仍然会面临诸如待测物需衍生化、复方制剂体内多组分同时测定时高浓度组分的质谱响应饱和、方法专属性误判、基质效应、残留效应等一系列挑战和问题,本文综述了这些常见问题的相应对策.     

黄金蝉若虫体蛋白水解液的荧光标记及电喷雾质谱鉴定

采用2-[2-(7H-二苯并[a,g]咔唑-乙氧基)-乙基]氯甲酸酯(DBCEC-Cl)作为柱前衍生试剂, 于室温下,在硼酸钠缓冲液(pH 9.0)中,金蝉若虫体蛋白水解液中氨基酸的完全衍生化在5 min即可完成.在Hypersil BDS C18色谱柱 (200 mm×4.6 mm, 5 μm) 上, 采用梯度洗脱实现了各衍生物的完全基线分离.最佳荧光检测为λex/λem=300/395 nm.在线串联的ESI/MS正离子质谱数据显示:所有衍生物均给出m/z 338 5,294.5的特征碎片离子峰.荧光条件下的线性回归系数大于0.9992; 检出限为2.6～24 fmol.本方法灵敏、可靠、重现性好.对实际黄金蝉若虫体蛋白水解液中氨基酸的测定,结果满意.     

Enhancing the detection sensitivity of trace analysis of pharmaceutical genotoxic impurities by chemical derivatization and coordination ion spray-mass spectrometry

Many pharmaceutical genotoxic impurities are neutral molecules. Trace level analysis of these neutral analytes is hampered by their poor ionization efficiency in mass spectrometry (MS). Two analytical approaches including chemical derivatization and coordination ion spray-MS were developed to enhance neutral analyte detection sensitivity. The chemical derivatization approach converts analytes into highly ionizable or permanently charged derivatives, which become readily detectable by MS. The coordination ion spray-MS method, on the other hand, improves ionization by forming neutral-ion adducts with metal ions such as Na⁺, K⁺, or NH₄⁺ which are introduced into the electrospray ionization source. Both approaches have been proven to be able to enhance the detection sensitivity of neutral pharmaceuticals dramatically. This article demonstrates the successful applications of the two approaches in the analysis of four pharmaceutical genotoxic impurities identified in a single drug development program, of which two are non-volatile alkyl chlorides and the other two are epoxides.     

Application of sugaring-out extraction for the determination of sulfonamides in honey by high-performance liquid chromatography with fluorescence detection

A simple sugaring-out assisted liquid-liquid extraction method combined with high-performance liquid-chromatography with fluorescence detection (HPLC-FL) was developed for the extraction and determination of sulfonamides in honey. Sample preparation consisted of acid hydrolysis to release sugar-bound sulfonamides. After derivatization with fluorescamine, the derivatives were partitioned into the organic layer under the honey (sugar)/water/acetonitrile system. The clear organic extract obtained by centrifugation could be injected into the HPLC system either directly or after dilution. Linearity was obtained with the coefficient of determination (R(2)) higher than 0.998 from 2 to 200 ng/mL. Under the optimal conditions, recoveries were determined for honey fortified at three levels (5, 20, and 100 ng/g) were 80.9-99.6% with coefficients of variation of 0.3-4.4%. Limits of detection for the sulfonamides studied were found to range from 0.6 to 0.9 ng/g.     

电化学衍生-高效液相色谱和荧光光度法检测花生酱中的黄曲霉毒素

建立了免疫亲和柱净化-柱后电化学衍生-高效液相色谱结合荧光光度法检测花生酱中4种黄曲霉毒素(B1、B2、G1和G2)的方法。样品经过体积分数为60%的甲醇提取,通过免疫亲和柱净化后,以KobraCell装置柱后衍生,高效液相色谱法分离定量。黄曲霉毒素B1、B2、G1和G2能达到完全的基线分离,检测限分别为0.5、0.15、0.5和0.15μg/kg,线性相关系数0.999,回收率可达74.2%～96.5%,相对标准偏差低于11%。该方法能够满足花生酱中黄曲霉毒素检测的需要。     

Dried blood spot on‐card derivatization: an alternative form of sample handling to overcome the instability of thiorphan in biological matrix

Thiorphan, the active metabolite of racecadotril, can undergo oxidation in biological matrices such as blood and plasma. In bioanalysis, a general approach for the stabilization of such a molecule is to derivatize the thiol group to a more stable thioether, often requiring complex handling procedures at the clinical site. In this research, the concept of dried blood spot (DBS) on‐card derivatization was evaluated to stabilize thiorphan. DBS cards were in‐house pre‐treated with 2‐bromo‐3′‐methoxyacetophenone and left to dry prior to blood spotting. Thiorphan was shown to be effectively derivatized to thiorphan–methoxyacetophenone once applied on the in‐house pre‐treated cards. Thiorphan–methoxyacetophenone was extracted by soaking a 6 mm DBS punch in methanol containing the internal standard (thiorphan–methoxyacetophenone‐D₅). Chromatographic separation was achieved on a Waters XBridge C₁₈ column with a gradient elution of 5 m m NH₄HCO₃ and methanol in 2.5 min and detection by ESI(+)/MS/MS. A linear (weighted 1/x²) relationship was obtained over a concentration range of 5.00–600.00 ng/mL. The assay met regulatory guidelines acceptance criteria for sensitivity, selectivity, precision and accuracy, matrix effect, recovery, dilution integrity and multiple stability evaluations. The DBS on‐card derivatization has shown to be an easy and reliable alternative form of sample collection for the quantification of thiorphan. Copyright © 2012 John Wiley & Sons, Ltd.     

Compounds having thiourea moiety as derivatization reagents in liquid chromatography/electrospray ionization–tandem mass spectrometry (LC/ESI‐MS/MS): synthesis of derivatization reagents for carboxylic acids

The derivatization reagents for carboxylic acids, N‐(Pyridin‐3‐yl)hydrazinecarbothioamide, N‐[4‐(dimethylamino)phenyl]hydrazinecarbothioamide, 1‐(2‐aminoethyl)‐3‐(pyridin‐3‐yl)thiourea, 1‐(2‐aminoethyl)‐3‐[4‐(dimethylamino)phenyl]thiourea and 4‐(2‐aminoethyl)‐N‐phenylpiperazine‐1‐carbothioamide were synthesized. These reagents reacted with carboxylic acids at 60°C for 45 min in the presence of the condensation reagents. The generated derivatives were favorably separated on the reversed‐phase column and sensitively detected by electrospray ionization tandem mass spectrometry. These reagents enhanced the electrospray ionization response of the analyte and generated a particular product ion efficiently by collision‐induced dissociation, and thus they were suitable for MS/MS detection. Copyright © 2010 John Wiley & Sons, Ltd.     

HPLC determination of colistin and aminoglycoside antibiotics in feeds by post-column derivatization and fluorescence detection

Summary Reversed-phase, HPLC methods employing post-column derivatization and fluorescence detection were developed for the determination of the peptide colistin and four aminoglycoside antibiotics in feeds. Extraction of the analytes was by sonication and shaking with dilute hydrochloric acid. Post-column derivatization was performed using orthophtaldialdehyde-2-mercaptoethanol chemistry. Assay of colistin was by using an acetonitrile-aqueous sodium sulphate-triethylammonium phosphate (pH 2.8) eluent. Aminoglycoside antibiotics:amikacin, kanamycin, gentamycin and neomycin were analyzed using a tetrahydrofuran-aqueous sodium sulphate-sodium pentanesulphonate-acetic acid mobile phase. The method was also applied to some pharmaceutical preparations. Preliminary results showed that the method can be adapted for the assay of the above antibiotics in meat and animal serum for residue and pharmacokinetic studies. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997.     

Chemical derivatization technique in ToF-SIMS for quantification analysis of surface amine groups

A chemical derivatization technique in ToF-SIMS along with principal component analysis (PCA) were used to perform a quantitative study of the surface amine density of the plasma-polymerized ethylenediamine (PPEDA) thin film. We used the scores on principal component (PC) 1 from a PCA of ToF-SIMS data for the PPEDA films and their chemical-derivatized surfaces for comparison with the surface amine densities. These surface amine densities were independently determined by UV-visible spectroscopy. Our work found a good linear relationship between the surface amine densities and the scores on PC 1 from a PCA of the ToF-SIMS data for the chemical-derivatized PPEDA surfaces, but not for the PPEDA thin films themselves. In addition to quantification, our PCA results provided insights into the surface chemical composition of each surface.