Validation and quantification of neonicotinoid insecticide residues in rice whole grain and rice straw using LC-MS/MS

An efficient analytical method was developed and validated using a modified QuEChERS method and LC-MS/MS for the detection and quantification of neonicotinoid insecticide residues in rice whole grain and rice straw. The samples were extracted using acetonitrile and cleaned up by dispersive solid-phase extraction. Validation based on five fortification levels showed good recoveries of neonicotinoids ranging from 75% to 116 % and 60% to 105 % for rice whole grain and straw, respectively. The precision ranged between 3% and 17 %, and 2% and 10 % for grain and straw, respectively. The limit of detection was from 0.007 to 0.0084 mg kg^?1 and 0.005 to 0.15 mg kg^?1 and the limit of quantification was in the range of 0.024–0.028 mg kg^?1 and 0.016–0.051 mg kg^?1 for rice whole grain and rice straw, respectively. Monitoring of farm gate samples indicated that, out of 24 samples, 1 rice whole grain sample was contaminated with thiamethoxam residues (0.07 mg kg^?1).     

Mass spectrometry and the cellular surfaceome

The collection of exposed plasma membrane proteins, collectively termed the surfaceome, is involved in multiple vital cellular processes, such as the communication of cells with their surroundings and the regulation of transport across the lipid bilayer. The surfaceome also plays key roles in the immune system by recognizing and presenting antigens, with its possible malfunctioning linked to disease. Surface proteins have long been explored as potential cell markers, disease biomarkers, and therapeutic drug targets. Despite its importance, a detailed study of the surfaceome continues to pose major challenges for mass spectrometry-driven proteomics due to the inherent biophysical characteristics of surface proteins. Their inefficient extraction from hydrophobic membranes to an aqueous medium and their lower abundance compared to intracellular proteins hamper the analysis of surface proteins, which are therefore usually underrepresented in proteomic datasets. To tackle such problems, several innovative analytical methodologies have been developed. This review aims at providing an extensive overview of the different methods for surfaceome analysis, with respective considerations for downstream mass spectrometry-based proteomics.     

高效液相色谱-串联质谱法测定动物组织中14种 β-内酰胺类兽药残留量的研究

A multiresidue method for the detection of 14 important β-lactam antibiotics (Amoxicyllin, Ampicillin, Cloxacillin, Dicloxacillin, Nafcillin, Oxacillin, Penicillin G, Penicillin V, Azlocillin, Methicillin, Phenethicillin, Cefalexin, Cefapirin, Cefazolin) in muscle, liver and kidney of pigs is presented .The method use CH₃CN/water during the extraction procedure and cleanup step over a waters oasis HLB SPE cartridge. The analytes are separated and detected by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-MS/MS) using external standard method . The recoveries for all 14 β-lactam antibiotics in muscle, liver and kidney of pigs ranged from 62.2%-96.8% at the fortification level ranged from 0.1 to 1 000 mg/kg.     

Analysis of four tobacco-specific nitrosamines in mainstream cigarette smoke of Virginia cigarettes by LC-MS/MS

An improved method was developed for the determination of the four major tobacco-specific nitrosamines（TSNAs） in mainstream cigarette smoke. The new method offers decreased sample preparation and analysis time as compared to traditional methods. This method uses isotope dilution liquid chromatography coupled with a tandem mass spectrometer with electrospray ionization and is significantly more sensitive than traditional methods. It also shows no evidence of artifactual formation of TSNAs. Sample concentrations were determined for four TSNAs in mainstream smoke using two isotopically labeled TSNAs analogues as internal standards. Mainstream smoke was collected on an industry standard 44-ram Cambridge filter pad, extracted with 0.1 mol/L ammonium acetate, purified by solid-phase extraction, and analyzed without further sample cleanup. The analytical column is a 3.9 mm×150 mm Waters Symmertry Shield RP18 column and volume fraction of the mobile phase is 50% methanol, 50% water containing 0.1% acetic acid. The results show that the linear range is 0.5-100.0 mg/L except for N-nitrosoanabasine （NAB） from 0.25 to 50.0 mg/L. The limits of detection are 0.1 mg/L for N-nitrosonornicotine （NNN）, 0.08 mg/L for 4-（methylnitrosamino）-1- （3-py-ridyl）-1-butanone （NNK）, 0.05 mg/L for N-nitrosoanatabine （NAT） and 0.06 mg/L for NAB. The recoveries of the four TSNAs are from 90.2% to 105.7%.     

基于液相色谱-串联质谱法检测多种食品中的16种合成着色剂

针对多种食品基质(葡萄酒、汽水、黄酒、植物蛋白饮料、乳饮料、花生酱、芝麻酱和糕点)建立了同时测定赤藓红、亮蓝、诱惑红、日落黄、靛蓝、柠檬黄、苏丹红Ⅰ、苏丹红Ⅱ、苏丹红Ⅲ、苏丹红Ⅳ、酸性红1、酸性红4、酸性红8、酸性红14、酸性红88和酸性红97这16种合成着色剂的高效液相色谱-质谱联用分析方法.根据样品种类和所含成分的差别,建立了不同的样品预处理方法,并且通过对提取溶剂的讨论,采用混合溶剂V(甲醇)∶V(乙腈)=2∶3作为提取试剂,比单一溶剂的提取效率更高.萃取液经Kromasil 100-5型色谱柱(150 mm×2.1 mm×5.0 μm)分离,外标法定量.结果表明,16种合成着色剂呈现良好的线性关系(r2 =0.998 9～0.9998),方法的检测限为0.10或0.010 mg/kg,进行低、中、高3个浓度水平添加实验的平均回收率为86.5％ ～97.3％,相对标准偏差＜4.9％(n=6).该方法重现性好,适合于多种食品中上述16种合成着色剂的检测.     

Determination of melamine in infant formulas by fluorescence quenching based on the functionalized Au nanoclusters

An environmentally benign and cost-effective assay was developed for the fast determination of melamine (MA) with tiopronin-stabilized gold nanoclusters (TPN-AuNCs) as a fluorophore. The TPN-protected gold nanoclusters which exhibit strong fluorescence emission were prepared by a simple one-vessel procedure. Upon addition of melamine to TPN-AuNCs, a dramatic decrease in their fluorescence intensity was observed, attributing to the electrostatic attraction between the MA and the surface of the TPN-AuNCs which induces the aggregation of TPN-AuNCs. Parameters affecting the detection of MA were investigated including pH, amount of TPN-AuNCs, temperature as well as reaction time. Under the optimized experimental conditions, trace amounts of MA could be analyzed based on the reduction in the fluorescence intensity of TPN-AuNCs. A linear relationship was established at concentrations ranging from 0.09 μM to 100 μM. The detection limit at 32 nM was achieved for this method. The developed method has been successfully applied to the determination of MA in several spiked infant formulas samples purchased from a local supermarket. Excellent recoveries at 92.0–102.2% and precision (RSD: 1.14–2.80%) were attained, respectively, which confirmed the great potential of tiopronin-stabilized gold nanoclusters toward practical measurement of melamine in infant formulas of samples.     

Scope extension validation of a LC-MS method for the inspection of preservatives in butter

Butters are considered as “natural products” by many consumers, once they are obtained from milkfat without adding of any additive, except sodium chloride, starter cultures and natural dyes. The main goals of this study were to extend the scope of a previously developed method, including a new analyte (benzoic acid) and new matrices (butter and margarine), and thus evaluate the content of preservatives in national and imported butters traded in Brazil. Samples (n = 51) from inspected establishments in Argentina (n = 2), Brazil (n = 40), France (n = 7) and Uruguay (n = 2) were assessed by liquid chromatography-tandem mass spectrometry. Two screening inspection rounds were carried out between November, 2015 and January, 2016. Non-compliance rates were 36.4% in 2015 and 22.2% in 2016 for Brazilian butters. It was shown that preservatives are irregularly added to butters by many factories, contrary to regulation, and without proper declaration on labeling. The limits of quantitation (LOQ) were set to 25.00 mg kg⁻¹ (benzoic acid), 1.25 mg kg⁻¹ (natamycin), 3.13 mg kg⁻¹ (nisin) and 2.50 mg kg⁻¹ (sorbic acid). Except nisin, any of the researched preservatives was detected in a total of 12 samples, in concentrations that ranged from <LOQ–235.67 mg kg⁻¹ (benzoic acid), 8.26–35.60 mg kg⁻¹ (natamycin) and 4.52–1007.17 mg kg⁻¹ (sorbic acid). The method was also checked on margarine samples, revealing concentrations that ranged from 43.72 to 359.17 mg kg⁻¹ (benzoic acid) and from 509.00 to 1102.67 mg kg⁻¹ (sorbic acid), respectively. Our findings demonstrate that there is a need for stricter control in butter processing, with the aim to ensure food safety and to safeguard consumers.     

Electrospray mass spectrometry for characterizing polyglycerols and the effects of adduct ion and cone voltage

Polyglycerol intermediates have been characterized by liquid chromatography-mass spectrometry (LC-MS) with electrospray ionization (ESI). Linear and cyclic components from n=2–23 in a sample of decaglycerol, for example, have been resolved in the second dimension or mass axis. Molecular weight (MW) distributions for tri-, hexa-, and decaglycerol products have been analyzed as a function of cone voltage and adduct ion (H⁺, Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, and NH₄ ⁺). A different combination is required to obtain a reliable MW distribution for each polyglycerol intermediate. The best distribution obtained by ESI/MS is determined by comparing the calculated hydroxyl number and cyclic content to that obtained by wet chemistry and gas chromatography, respectively. Once ESI/MS conditions are established, the distribution can be used, for the first time in polyglycerol analysis, to calculate important parameters such as number average MW, weight average MW, polydispersity, % cyclics, hydroxyl number, wt% above n=6, etc.     

液相色谱-串联质谱法测定腐乳中的生物胺

建立了一种使用液相色谱-串联质谱（LC-MS/MS）技术检测腐乳中9种生物胺的方法。样品经5%三氯乙酸水溶液提取后,进行液相色谱-串联质谱法测定,采用外标法定量。对检测方法进行方法学验证,9种生物胺在质量浓度为10～200 ng/mL范围内线性相关系数R2＞0.999,方法检出限为0.03 mg/kg,定量限为0.1 mg/kg,回收率在85%～101%之间,相对标准偏差（RSD）在0.9%～4.8%之间。该方法结果精密、准确、重复性好、操作简单,适用于腐乳中9种生物胺的测定。     

液相色谱-串联质谱法测定畜禽肌肉和表皮组织中松香酸、脱氢松香酸和胡椒酸

目的 建立了畜禽肌肉和表皮组织中松香酸、脱氢松香酸和胡椒酸的液相色谱-四极杆/串联质谱(LC-MS/MS)的检测方法。方法 均质样品中加入乙腈和水分别提取目标物,经涡旋分散、震荡提取、离心和固相萃取柱净化。提取液以乙酸铵-甲醇为流动相梯度洗脱C18色谱柱分离,5 mmol的乙酸铵和甲醇为流动相进行梯度洗脱,三重四级杆质谱ESI+/ESI-切换模式检测,以特征离子峰和保留时间定性,定量离子峰面积定量。结果 松香酸、脱氢松香酸的测定低限为5.0 μg/kg、胡椒酸20.0 μg/kg,线性范围分别为5.0~200.0 μg/kg和20.0~500.0 μg/kg,相关系数(r)在0.999以上。分别添加定量限1、2、4倍的浓度验证加标回收率,三个浓度水平的回收率为68.5% ~ 107.6%,相对标准偏差(RSD)为6.8%~14.2%(n=6)。结论 该方法快速、准确、灵敏,适用于监管部门对市售畜禽食品中工业松香残留的检测。