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Analytical Methods (v.4, #3)
Front cover (pp. 583-583).
Among various metal oxides, cerium oxide (CeO2 ) shows the highest catalytic activity for transamidation of picolinamide with n -octylamine. CeO2 acts as a reusable and effective heterogeneous catalyst for transamidation under solvent-free conditions. Transamidation of a variety of amides and amines produced the corresponding N-alkyl amides in high yields. This method provides the first example of a heterogeneous catalyst for transamidation using aliphatic amines as substrates. Characterization of acid–base properties and kinetic studies suggest that the cooperation of the weak Lewis acid sites and adjacent strong base sites play important roles in the transamidation reaction.
Inside front cover (pp. 584-584).
Clay-intercalated Sn catalysts were prepared by a conventional cation-exchange method and used for the Baeyer–Villiger oxidation of various ketones with hydrogen peroxide as an oxidant. The intercalation of monomeric Sn species into the clay interlayer was monitored by solid-state 7Li MAS NMR. Solid-state 119Sn MAS NMR and Sn K-edge XAFS analysis revealed that an isolated Sn species, such as [SnIV(OH)x 2 O)5−x ](4−x )+ (x = 0–3), was formed in the clay interlayers. Our clay-intercalated Sn catalysts showed extremely high performance in Bayer–Villiger oxidation and were also reusable without any significant loss of activity or selectivity.
Contents list (pp. 585-598).
Many active pharmaceutical ingredients (APIs) are bitter and the bitterness intensity is usually in direct proportion to the treatment efficacy of APIs. However, the bitterness of some APIs induces an unpleasant taste or odor that has been a hurdle to their commercialization. One potential solution to address this is to mask the unpleasant taste, the success of which depends on the precise evaluation of bitterness. Currently, various methods have been developed for bitterness evaluation, such as the human gustatory test, the animal gustatory test, calcium imaging and electronic tongues (taste sensors). In this paper, we review state-of-the-art bitterness evaluation methods and discuss their distinctive advantages and potential challenges for use in the pharmaceutical and food industries.
Recent advances in bitterness evaluation methods by Zhaobin Chen; Jinhui Wu; Yang Zhao; Feng Xu; Yiqiao Hu (pp. 599-608).
Many active pharmaceutical ingredients (APIs) are bitter and the bitterness intensity is usually in direct proportion to the treatment efficacy of APIs. However, the bitterness of some APIs induces an unpleasant taste or odor that has been a hurdle to their commercialization. One potential solution to address this is to mask the unpleasant taste, the success of which depends on the precise evaluation of bitterness. Currently, various methods have been developed for bitterness evaluation, such as the human gustatory test, the animal gustatory test, calcium imaging and electronic tongues (taste sensors). In this paper, we review state-of-the-art bitterness evaluation methods and discuss their distinctive advantages and potential challenges for use in the pharmaceutical and food industries.
Discrimination of dopamine from ascorbic acid and uric acid on thioglycolic acid modified gold electrode by Guangming Liu; Jingjing Li; Li Wang; Nana Zong; Shipeng Yu; Feng Li (pp. 609-611).
A highly selective electrochemical sensor for dopamine (DA) has been successfully prepared, which can effectively eliminate the interferences from ascorbic acid and uric acid. The detection limit for DA is obtained as 0.5 μM in aqueous solution.
Visual detection of copper(
A novel, highly sensitive and selective colorimetric method for copper(ii ) detection through copper(i ) catalyzed alkyne–azide cycloaddition reaction (CuAAC) has been developed. Copper(i ) is produced by the electrochemical reduction of copper(ii ) via Bulk Electrolysis (BE) with coulometry. The azide- and alkyne-functionalized Au nanoparticles (AuNPs) can aggregate quickly (10 min) through CuAAC reaction, resulting in the color of the solution changing from red to purple. Furthermore, the change of color is closely related to the concentration of copper(ii ), and 1 nM copper(ii ) could be detected by the naked eye. Additionally, the proposed method has good selectivity to copper(ii ) in the presence of other common metal ions.
Highly sensitive fluorescent chemosensor for hypochlorite anion based on a novel irreversible ring-opening strategy by Fangfang Wei; Yan Lu; Song He; Liancheng Zhao; Xianshun Zeng (pp. 616-618).
A novel strategy to design a fluorescent chemosensor for OCl− which can be used over a pH span of 6–11 by integrating the reactive phenylhydrazo group within rhodamine 6G has been achieved. Upon the reaction with OCl−, a significant fluorescence enhancement was triggered with a detection limit down to the 10−9 M range.
Anatase TiO
Anatase TiO2 nanoparticle–graphene nanocomposites with enhanced direct electrochemistry of hemoglobin and biosensing for H2 O2 were synthesized via a facile, one-step approach in aqueous solution at room temperature.
Monitoring passive transport of redox mediators across a confluent cell monolayer with single-cell resolution by means of scanning electrochemical microscopy by Stefan Bergner; Joachim Wegener; Frank-Michael Matysik (pp. 623-629).
Scanning electrochemical microscopy (SECM) was used for time-resolved studies of passive transport of redox active substances across cell monolayers with sub-cellular resolution. Platinum disk ultramicroelectrodes (UMEs) with effective electrode radii in the sub μm range were operated in the constant-height mode. Monolayers of normal rat kidney (NRK) or Madin Darby canine kidney strain II (MDCK II) epithelial cells served as model cell lines and were grown to confluence on permeable membrane filters to investigate the transport of redox mediators across epithelial barriers. A novel electrochemical cell was developed ensuring reliable mechanical fixation of the growth substrate and preventing membrane vibrations during the SECM operation. The detection of different redox mediators was enabled by potential switching at the UME. This concept proved to be an attractive alternative to the use of dual-microelectrodes or micropipette-microelectrode combinations. The various cell lines were investigated regarding their barrier functions with respect to different redox mediators. Para- and/or trans-cellular transport mechanisms could be distinguished using either hydrophilic ruthenium hexamine chloride or lipophilic ferrocene methanol as redox mediators.
Mercury determination in soil by CVG-ICP-MS after volatilization using microwave-induced combustion by Rochele S. Picoloto; Helmar Wiltsche; Günter Knapp; Juliano S. Barin; Erico M. M. Flores (pp. 630-636).
Microwave-induced combustion (MIC) was applied for mercury volatilization from soil with subsequent determination by cold vapor generation coupled with inductively coupled plasma mass spectrometry (CVG-ICP-MS). Samples of soil were mixed with microcrystalline cellulose (300 mg), pressed as pellets and combusted in closed quartz vessels pressurized with 20 bar of oxygen. Mercury was volatilized from the sample matrix during combustion and quantitatively absorbed in a suitable solution. The type and concentration of absorbing solution (diluted or concentrated nitric or hydrochloric acids, or even water) as well as the use of a reflux step after combustion were studied. Accuracy was evaluated using soil certified reference materials. Using 0.25 mol L−1 HNO3 as absorbing solution with a reflux step of 5 min the agreement with reference values was better than 95%. The limit of detection was 0.006 μg g−1 Hg (using 300 mg of sample mass) and the residual carbon content for MIC digests was always below 1%. The main advantage of the proposed method is related to the complete separation of the analyte from the sample matrix. Up to eight samples could be simultaneously combusted in only 25 min. Taking into account that only 6 ml of very diluted nitric acid solution (0.25 mol L−1) were used, the proposed MIC method coupled with CVG-ICP-MS can be considered in good agreement with green analytical chemistry recommendations.
Development of aged fingermarks using antibody-magnetic particle conjugates by Amanda M. Boddis; David A. Russell (pp. 637-641).
Aged fingermarks are difficult to develop using traditional fingermark methods. Here we use anti-cotinine magnetic particle conjugates combined with fluorescently tagged secondary antibody fragments to develop fingermarks, deposited on glass by a smoker volunteer, that have been aged under four different conditions: at room temperature in the light; room temperature in the dark; at an elevated temperature in the dark (55 °C); and stored within a freezer (−20 °C) in the dark. The anti-cotinine magnetic particle conjugates bound to the ridges of the latent fingermarks of the smoker to produce high resolution brightfield and fluorescence images that were suitable for identification purposes. The antibody-particle conjugates were used to develop fingermarks aged for up to 4 weeks stored under the 4 environmental conditions. The best quality images were obtained when the fingermarks were aged at an elevated temperature of 55 °C. This successful development of aged fingermarks using anti-cotinine magnetic particle conjugates suggests that this method is an excellent alternative to powders or cyanoacrylate (superglue) fuming that are typically used for the development of aged fingermarks.
Multivariate analyses of UV-Vis absorption spectral data from cachaça wood extracts: a model to classify aged Brazilian cachaças according to the wood species used by Alexandre Ataide da Silva; Denis De Keukeleire; Daniel Rodrigues Cardoso; Douglas Wagner Franco (pp. 642-646).
Multivariate analyses of UV-Vis spectral data from cachaça wood extracts provide a simple and robust model to classify aged Brazilian cachaças according to the wood species used in the maturation barrels. The model is based on inspection of 93 extracts of oak and different Brazilian wood species by a non-aged cachaça used as an extraction solvent. Application of PCA (Principal Components Analysis) and HCA (Hierarchical Cluster Analysis) leads to identification of 6 clusters of cachaça wood extracts (amburana, amendoim, bálsamo, castanheira, jatobá, and oak). LDA (Linear Discriminant Analysis) affords classification of 10 different wood species used in the cachaça extracts (amburana, amendoim, bálsamo, cabreúva-parda, canela-sassáfras, castanheira, jatobá, jequitibá-rosa, louro-canela, and oak) with an accuracy ranging from 80% (amendoim and castanheira) to 100% (bálsamo and jequitibá-rosa). The methodology provides a low-cost alternative to methods based on liquid chromatography and mass spectrometry to classify cachaças aged in barrels that are composed of different wood species.
Exploration of a coordination polymer as a novel sorbent for the solid-phase extraction of benzo[a]pyrene in edible oils by Guan-Hua Wang; Yong-Qian Lei; Hua-Can Song (pp. 647-651).
In this paper, a zinc(ii ) coordination polymer, [Zn(BTA)2 ]n
Qualitative and quantitative analysis of phosphopeptides with immobilized metal ion affinity chromatography enrichment, stable isotope labeling by amino acids in cell culture and nano-liquid chromatography-tandem mass spectrometry by Bo Zhang; Xinghua Liu; Qinfang Shi; Qi Liang; Changyao Wu; Jianying Chen (pp. 652-658).
The progression of the cell cycle in eukaryote cells is tightly regulated by protein phosphorylation in order to ensure genetic integrity. Quantitative evaluation of phosphorylation changes during the cell cycle is obtained with titanium dioxide (TiO2 ) enrichment coupled with stable isotope labeling and mass spectrometry (MS). However, information about multiply phosphorylated peptides is insufficient because of the low recovery of multiply phosphorylated peptides enriched and quantified with this strategy. In this study, simultaneous identification and quantitation of phosphopeptides, especially multiply phosphorylated peptides, were performed based on immobilized metal ion affinity chromatography (IMAC), stable isotope labeling by amino acids in cell culture (SILAC) and nano-liquid chromatography-tandem mass spectrometry (nano-LC-MS/MS). Direct nano-ESI-MS/MS and nano-LC-MS/MS demonstrated complementary properties for phosphopeptide detection. A total of 355 phosphorylation sites from 268 phosphopeptides were identified and quantified. More than 30% of phosphopeptides were multiply phosphorylated ones. Up to 40 phosphopeptides were up-regulated and 24 phosphopeptides were down-regulated during the cell cycle. The method demonstrated itself as a feasible tool for quantitative analysis of phosphopeptides, especially multiply phosphorylated peptides from complex samples.
Characterization of the binding medium used in Roman encaustic paintings on wall and wood by Jorge Cuní; Pedro Cuní; Brielle Eisen; Rubén Savizky; John Bové (pp. 659-669).
The characterization by means of Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy and Gas Chromatography-Mass Spectrometry of the binding medium present in eight samples of Roman wall paintings coming from three archaeological sites in Spain and a sample of a Roman-Egyptian mummy portrait on wood showed strong evidence that the medium in all the studied samples was composed of beeswax and soap. These results suggest for the first time that Roman artists used in wall and easel paintings a water soluble encaustic paint of beeswax and soap. Experimental studies with a wax-and-soap technique showed that this painting technique allows reproduction of the physical characteristics of many Roman-Egyptian encaustic mummy portraits with greater accuracy than the hot wax encaustic paint and the alkali-treated encaustic paint often considered to be the painting techniques used in these portraits. Wax-and-soap encaustic also showed greater accuracy in reproducing the physical characteristics of Roman wall paintings than the fresco painting technique, generally thought to be the technique used to execute such paintings. This study suggests that wax-and-soap encaustic could be a common painting technique among Roman artists, and its composition could correspond to a lost ancient encaustic formulation searched for the last five centuries by many artists and researchers dissatisfied with the former reconstructions of the ancient encaustic painting technique.
Accelerated solvent extraction combined with capillary electrophoresis as an improved methodology for simultaneous determination of residual fluoroquinolones and sulfonamides in aquatic products by Hanwen Sun; Yanli Zuo; Haijing Qi; Yunkai Lv (pp. 670-675).
A rapid and effective accelerated solvent extraction (ASE)–capillary electrophoretic method was developed for the determination of fluoroquinolone and sulfonamide residues in aquatic products. Seven residues were extracted with acetonitrile at 80 °C under 10.3 MPa pressure in less than 25 min. The standard curves for the determination of seven residues by the capillary electrophoretic method have good linearity (r 2 > 0.999). The method limits of quantification (LOQs) were 70–100 μg kg−1. Their average recoveries with three spiked levels ranged from 83% to 106%. Intra- and inter-day precision (RSD) were 2.3–4.9% and 3.1–6.5%, respectively. The method provides a rapid and simple extraction procedure with high recoveries, and has been applied for the determination of 4 fluoroquinolone and 4 sulfonamide residues in aquatic products with satisfactory results.
Practical comparison of multivariate chemometric techniques for pattern recognition used in environmental monitoring by A. Gredilla; J. M. Amigo; S. Fdez-Ortiz de Vallejuelo; A. de Diego; R. Bro; J. M. Madariaga (pp. 676-684).
Environmental datasets usually contain multiple and highly correlated variables. The use of multivariate techniques in this case has experienced a significant development. This paper provides a feasible comparison among several methods for pattern recognition: Principal Component Analysis (PCA), Multivariate Curve Resolution (MCR), Parallel Factor Analysis (PARAFAC) and Tucker3. They have been systematically applied on the same dataset, consisting of the concentration of trace elements measured in sediments of the estuary of the Nerbioi-Ibaizabal river (Basque Country). The results obtained have been critically discussed in terms of ease of use, interpretation of the results, and amount of information provided. The most popular PCA is probably enough for a correct and overall interpretation of the results. MCR, however, may lead to slightly different results due to the non-perceptive orthogonality of the principal components. Both PARAFAC and Tucker3 provide simplified graphical outputs that make easier interpretation of the results.
Simultaneous determination of pre-emergence herbicides in environmental samples using HPLC-DAD combined with second-order calibration based on self-weighted alternating trilinear decomposition algorithm by Xiang-Dong Qing; Hai-Long Wu; Yuan-Na Li; Chong-Chong Nie; Jian-Yao Wang; Shao-Hua Zhu; Ru-Qin Yu (pp. 685-692).
This work presents a novel strategy for simultaneous and rapid quantitative analysis of three pre-emergence herbicides in environmental samples using HPLC-DAD combined with second-order calibration based on the self-weighted alternating trilinear decomposition (SWATLD) algorithm. The sample preparation procedure was simplified only by using water as solvent and methanol as extractant and data were measured in less than 4.2 min by applying an isocratic mode. Although the elution and spectral profiles of the analytes, prometryne (PRO), napropamide (NAP) and alachlor (ALA), are heavily overlapped with each other and with matrix constitutes, the method not only extracts the profiles of the analytes, but also simultaneously determines the concentrations of them in actual complex systems, i.e. , river sediment and wastewater samples. In the analysis of river sediment and wastewater samples, the obtained average recoveries were 99 ± 6% and 98 ± 5% for PRO, 108 ± 6% and 100 ± 4% for NAP and 98 ± 5% and 97 ± 4% for ALA, respectively. Furthermore, the accuracy and precision of the proposed method was also evaluated through elliptical joint confidence region tests as well as figures of merit. Such a chemometrics-based protocol may be a very promising tool for more analytical applications in environment monitoring, due to its advantages of easy sample pretreatment, green, sufficient spectral resolution and concentration prediction even in the presence of unknown interferences.
Early diagnosis of urinary lithiasis
An elemental analysis method was established to monitor the element levels in serum samples of 38 healthy controls and 38 stone patients. Based on the optimized platform combined with multivariate analysis, satisfactory results can be obtained for urinary lithiasis diagnosis with the concentrations of 9 elements, in which Ba, Ga, Sb, and Na are the top 4 elements of statistical significance. The patients could be subdivided into calcareous and non-calcareous stone patients by metallomic profiling; and it is found that Se plays the major role in this classification. This study indicates that serum elementary analysis gives an insight into the possibility of diagnosis of urinary lithiasis, subsequently it may allow estimation of the content subtype of stones. By means of this simple method of elemental profiling in serum, it might allow early prognosis and treatment guide to urinary lithiasis.
Detection of formaldehyde in food samples by enhanced chemiluminescence by Uchangi Satyaprasad Akshath; L. Sagaya Selvakumar; Munna Singh Thakur (pp. 699-704).
In this study, chemiluminescence (CL) from oxidation of formaldehyde and luminol was investigated under alkaline conditions to develop a sensitive analytical tool for formaldehyde detection. The developed method was successfully applied for detection of formaldehyde in spiked soft drinks, wine, and raw fish storing solution. CL enhancement by optimized conditions of luminol, urea–H2 O2 , pH, and sequence of addition was investigated, which was not explored previously. The limit of detection was 10 pg ml−1 and linear range 10 pg ml−1 to 100 μg ml−1 with a regression coefficient of R 2 = 0.998. The importance of these experimental parameters is discussed based on knowledge of oxidation of luminol by urea–H2 O2 and further enhancement of CL by formaldehyde oxidation. Formaldehyde was spiked and recovered with 95–99.9%. The results obtained were compared with those of high-performance liquid chromatography (HPLC) and were well correlated.
A reproducible method for the extraction, identification and quantification of the Arctic sea ice proxy IP
IP25 is a highly branched isoprenoid lipid biomarker that is produced by some Arctic sea ice diatoms in the spring. The presence of IP25 in marine sediments has previously been used as a proxy measure of past spring sea ice occurrence in the Arctic. Here, a reliable analytical procedure for the reproducible extraction, identification and quantification of IP25 from marine sediments is presented for the first time. This protocol represents a Standard Operating Procedure (SOP) that should be straightforward to adopt by other researchers in the future. This paper also explains the significance of individual components and steps, including the internal standards used for quantification of IP25 , the purification of sediment extracts to simplify the subsequent analysis and some key analytical considerations, especially when mass spectrometric methods are used for detection and quantification. The application of the SOP is illustrated with the analysis of IP25 in sediment material obtained from two nearby locations in the western region of the Canadian Arctic Archipelago (CAA). In the first case (Franklin Bay), sediment material was homogenised and aliquots used to demonstrate the reproducibility of the SOP and to provide a suitable reference material when studying other cores. In the second case (central Amundsen Gulf), IP25 concentrations were shown to be quite variable, consistent with observations reported previously for sediment cores from other regions of the CAA. Further experimental considerations are presented that permit the conversion of sedimentary IP25 concentrations into temporal fluxes that are probably more useful for palaeo sea ice studies.
A mass spectrometric assay for the quantification of neuropeptide PYY in plasma by Li Xi; Yaping Jin; Peter Josh; Edward A. Parker; Herbert Herzog; Michelle Colgrave (pp. 714-720).
A multiple reaction monitoring mass spectrometric assay for the quantification of PYY in human plasma has been developed. A two stage sample preparation protocol was employed in which plasma containing the full length neuropeptide was first digested using trypsin, followed by solid-phase extraction to extract the digested peptide from the complex plasma matrix. The peptide extracts were analysed by LC-MS using multiple reaction monitoring to detect and quantify PYY. The method has been validated for plasma samples, yielding linear responses over the range 5–1,000 ng mL−1. The method is rapid, robust and specific for plasma PYY detection.
Crime scene investigation III: Exploring the effects of drugs of abuse and neurotransmitters on Bloodstain Pattern Analysis by Bethany A. J. Larkin; Meerna El-Sayed; Dale A. C. Brownson; Craig E. Banks (pp. 721-729).
The possible misinterpretation of Bloodstain Pattern Analysis (BPA) is explored with regards to the variability in blood viscosity and surface tension values that may result from the presence of a variety of chemical additives, such as cocaine and its prominent metabolite benzoylecgonine hydrate in addition to frequently encountered neurotransmitters, namely dopamine, serotonin and epinephrine. Defibrinated horse blood was spiked with the chemicals of interest over appropriate concentration ranges and subsequent viscosity and surface tension measurements were both conducted utilising a capillary tube viscometer and a tensiometer. In the case of cocaine and its metabolite, concentrations of which encompassed therapeutic to potentially fatal levels, 10−6 to 10−4 M respectively, were employed and found to result in an alteration in the dynamic viscosity of defibrinated horse blood of between 1.1 to 7.8% (±0.72 and ±0.77, N = 3) and 6.4 to 9.5% (±0.78 and ±1.52, N = 3) respectively. Furthermore with the addition of variable concentrations of cocaine or its metabolite the surface tension of defibrinated horse blood was found to deviate from that of its unadulterated value of 51.0 mN m−1 (±0.92, N = 3) where for the highest concentration explored a decreased value of either 43.8 or 44.2 mN m−1 (±0.47 and ±0.77, N = 3) was measured respectively. Interestingly, in the case of the neurotransmitters, spiked into defibrinated horse blood over the range of 10−6 to 10−3 M, we find there to be no change or significant deviation in the respective viscosity values measured with regards to that of the unmodified blood. A possible explanation for this differing behaviour is given and where alterations in the viscosity and surface tension values of blood are noted we incorporate such variables into applicable BPA equations in order to ascertain the implications that this may induce within the Forensic interpretation of bloodstains. Consequently, through probing these equations and the employment of bloodstain spatter experiments (commonly employed within BPA) it is found that the addition of drugs of abuse and the presence of common neurotransmitters have no significant implications towards the misinterpretation of BPA.
Development of a novel direct-infusion atmospheric pressure chemical ionization mass spectrometry method for the analysis of heavy hydrocarbons in light shredder waste by Nadim Hourani; Nikolai Kuhnert (pp. 730-735).
A novel direct-infusion atmospheric pressure chemical ionization mass spectrometry method to identify saturated straight-chain hydrocarbons in light shredder waste fraction has been developed. Ionization of alkanes under nitrogen gas source favored hydrogen abstraction producing mostly (M–H)+ ions, which strictly correspond to their respective series of n -alkanes between n -decane (C10 ) and n -tetra-contane (C40 ). The method is shown to produce intact gas phase ions of n -alkane in both reference and real life waste samples. APCI-MS2 fragmentation data assisted in the structural verification of the n -alkanes investigated in both standard and waste mixtures.
Electrochemical behavior of 6-benzylaminopurine and its detection based on Pt/ordered mesoporous carbons modified electrode by Yufan Zhang; Xiangjie Bo; Liping Guo (pp. 736-741).
In the present work, a novel amperometric sensor of 6-benzylaminopurine (6-BA) was developed, which based on Pt nanoparticles/ordered mesoporous carbons (Pt/OMCs) modified glass carbon (GC) electrode. The mechanisms for 6-BA oxidation at the Pt/OMCs electrode were investigated, which is an adsorption-controlled process and the standard rate constant of electrochemical reaction (k s ) is 0.51s−1. The 6-BAH+ and neutral 6-BA molecule may be the electroactive substances in the pH range of 2.0–6.0 and 6.0–11.0, respectively. The Pt/OMCs electrode shows a wider linear range (0.05 to 24 μM) and low detection limit (5 nM) for detecting 6-BA. Compared with the other modified electrode, the Pt/OMCs nanocomposites exhibit a good electrocatalytic activity, excellent stability and repeatability towards 6-BA. Moreover, it was successfully applied to the determination of 6-BA in real samples.
Comparative studies on carbon paste electrodes based on three dithiocarbamate podands as ionophore in Ag(
Three dithiocarbamate podands, [N,N′(bis[(1-oxoethyl) morpholine-2-carbodithioate])-2,6- diaminopyridine] (P1 ), [N,N′(bis [(1-oxoethyl)piperidine-2-carbodithioate])-2,6-diaminopyridine] (P2 ) and [N,N′(bis[(1-oxoethyl)diethylamine-2-carbodithioate])-2,6-diaminopyridine] (P3 ) have been synthesized and used as ionophores for Ag+-selective carbon paste electrodes. The construction, response characteristic and application of the silver ISEs are investigated. Potentiometric responses reveal that the flexibility of the ligands has a great effect on the selectivity and sensitivity toward Ag+ ions. Among the podands, the best performance was achieved with the sensor using P1 as ionophore. The proposed sensor exhibits Nernstian response with the slope of 58.6 ± 0.6 mV/decade in the concentration range of 8.2 × 10−8–1.5 × 10−2 mol L−1 of Ag+ and a lower detection limit of 6.3 × 10−8 mol L−1. The linear concentration range of the electrodes modified with P2 and P3 were also 2.5 × 10−6–1.2 × 10−2 and 6.3 × 10−7–1.2 × 10−2 mol L−1, respectively. The response time of the electrode based on p1 was 8 s and its potential was independent of pH in the range of 2.9–8.2. The electrodes were highly selective to Ag+ ions over a large number of mono, bi, and tri-valent cations which make them unique in the analysis of real samples.
A novel amperometric sensor based on intercalated montmorillonite modified carbon paste electrode for hydroquinone determination by Yong Kong; Mengjie Ma; Huihui Mao; Jiangquan Ma; Chao Yao (pp. 748-752).
A simple and reliable amperometric sensor for hydroquinone (HQ) determination is developed based on an intercalated montmorillonite (MMT) modified carbon paste electrode (CPE). The modified CPE significantly enhances the peak current of HQ on cyclic voltammograms and differential pulse voltammograms. The electro-catalytic properties of the intercalated MMT can be attributed to the remarkably increased specific surface area of MMT after the intercalation process, which leads to a higher accumulation efficiency for HQ at this modified CPE. The modified CPE shows a linear range between 5 and 2000 μM HQ with a correlation coefficient of 0.9997, and the detection limit is as low as 0.57 μM (S/N = 3).
A straightforward quantification of triacylglycerols (and fatty acids) in monovarietal extra virgin olive oils by high-temperature GC by Cristina Ruiz-Samblás; Luis Cuadros-Rodríguez; Antonio González-Casado; Francisco P. Rodríguez-García (pp. 753-758).
The analytical characterization of the triacylglycerol (TAG) profile of samples which include ten Spanish monovarietal extra virgin olive oils (“Hojiblanca”, “Manzanilla”, “Picual”, “Picudo”, “Cornicabra”, “Lechin”, “Verdial”, “Empeltre”, “Blanqueta” and “Arbequina”) is reported. High temperature gas chromatography-(ionic trap)mass spectrometry, HTGC-(IT)MS, was employed for TAG profiling in olive oils. No sample treatment was required. For quantification purposes, a standard calibrant mixture, including all the previously identified TAGs in olive oils, was used. Results showed that triolein (27–50%) and 1,2-olein-3-palmitin (19–38%) were the most abundant TAGs in the analyzed samples, though their relative proportion changed between samples which corresponded to different varieties of olive oils. An estimation of the composition of main fatty acids (FAs) was also enabled in a simple approach from the TAG profiles. This analytical methodology for FA profiling in olive oil was validated by using two external olive oil reference materials. The results were found to constitute an approach, in a fast and easy way without using any derivatization reactions, to a conventional fatty acid methyl ester (FAME) gas chromatography method, when no high analytical performances are mandatory.
Highly selective determination of trace quantities of Hg(
A cloud-point extraction method for preconcentration of ultra-trace quantities of mercury ions as a prior step to its determination by spectrophotometry is presented and discussed. Cloud-point extraction was carried out using [1-(2-ethoxy phenyl)-3-(2-chloro phenyl)] triazene (EOCT) as the chelating agent and Triton X-114 as the non-ionic surfactant. The preconcentrated mercury was then determined spectrophotometrically by measuring the absorbance of the surfactant rich phase at 366 nm and also by measuring the emission intensities in the ICP-OES signals at 253.7 nm. Linearity was obeyed in the range of 8.0–150.0 ng mL−1 and 20–200 ng mL−1 by ICP-OES and spectrophotometry, respectively. The variable affecting the combined preconcentration-emission and absorption methods have been evaluated and optimized. Under the optimum condition, the detection limit of 1.03 ng mL−1 and 5.46 ng mL−1 were achieved using ICP-OES and UV-vis, respectively. The results in this paper will show using spectrophotometric method after cloud-point extraction can be an appropriate method for determining of mercury concentration at the ppb level in place of ICP-OES which is too costly a method. The interference effect of some anions and cations was also tested. Finally, the proposed method was successfully used for determination of Hg(ii ) in some real samples.
Extraction of neonicotinoid insecticides from environmental water samples with magnetic graphene nanoparticles as adsorbent followed by determination with HPLC by Weina Wang; Yunpeng Li; Qiuhua Wu; Chun Wang; Xiaohuan Zang; Zhi Wang (pp. 766-772).
In this paper, a kind of graphene magnetic nanoparticle (G–Fe3 O4 ) was prepared and used as the adsorbent for the preconcentration of the four neonicotinoid insecticides (thiamethoxam, imidacloprid, acetamiprid and thiacloprid) from environmental water samples. The properties of the magnetic adsorbent were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. After preconcentration, the adsorbent can be conveniently separated from the aqueous samples by an external magnet, and the analytes desorbed were determined by high performance liquid chromatography-ultraviolet detection (HPLC-UV). Various parameters affecting the extraction efficiencies such as the concentration of G–Fe3 O4 , the extraction time, the pH of the sample solution, the salinity and the desorption conditions were investigated. Under the optimum conditions, the concentration factors for the analytes ranged between 3325 and 4644. The linearity of the method was in the range from 0.05 to 50 ng mL−1 with the correlation coefficients (r ) ranging from 0.9990 to 0.9995. The limits of detection (S /N = 3) of the method for thiamethoxam, imidacloprid, acetamiprid and thiacloprid were 0.01, 0.006, 0.004 and 0.006 ng ml−1, respectively. The relative standard deviations (RSDs) varied from 4.3% to 7.4% (n = 6), and the recoveries of the method for the compounds at spiking levels of 0.5 and 5 ng mL−1 were in the range of 86%–110%. The method has been successfully applied to the analysis of the neonicotinoid insecticides in real water samples.
Towards an ideal method for analysis of lisinopril in pharmaceutical formulations using a tris(2,2′-bipyridyl)-ruthenium(
A novel, rapid, selective and sensitive method has been developed for analysis of lisinopril (LIS) in pharmaceutical formulations using a tris(2,2′-bipyridyl)-ruthenium(ii ) (Ru(bipy)3 2+) peroxydisulfate chemiluminescence (CL) system in a two chip device. The parameters that influence the CL signal intensity were carefully optimized. These include pH, flow rates and concentration of reagents used. Under optimum conditions, a linear calibration curve between 0.25 and 50.0 μg mL−1 was obtained. About 180 samples were analyzed per hour while the detection limit was found to be 0.067 μg mL−1. The method was applied for analysis of LIS in pharmaceutical products and was found to be free from interferences of acid-induced degradation (AID) products and other ingredients usually present in these preparations.
The use of CIM-DEAE monolithic chromatography coupled to ICP-MS to study the distribution of cisplatin in human serum by Anze Martincic; Radmila Milacic; Maja Cemazar; Gregor Sersa; Janez Scancar (pp. 780-790).
Among platinum (Pt) containing chemotherapeutics, cisplatin (CDDP) is the most widely used. Its distribution in spiked human serum and serum of cancer patients was studied by liquid chromatography with UV and ICP-MS detection. Rapid Pt fractionation was performed by SEC on a HiTrap desalting column. The CIM DEAE-1 fast monolithic column was used in speciation analysis of CDDP for the first time. Complementary to monolithic chromatography, Pt speciation was also performed by FPLC on a strong anion-exchange Mono Q particle packed column. To study CDDP interactions with proteins, synthetic solutions of single standard proteins (albumin (HSA), transferrin (Tf) and γ-globulins (IgG)) or their mixtures, and human serum samples were spiked with CDDP and incubated at 37 °C for 24 h. Results of fractionation showed that more than 80% of Pt in serum was eluted with proteins and the remaining portion as low molecular mass species. Serum proteins were efficiently separated by anion-exchange chromatography on FPLC Mono Q or CIM DEAE-1 columns. Both complementary speciation procedures gave statistically comparable results. In spiked serum samples about 83 to 87% of Pt was eluted with HSA, 3 to 4.5% with Tf and the remaining 8.5 to 14%, which represents unbound CDDP, with a solvent front. The developed CIM-DEAE-1 fast monolithic chromatography procedure was applied to Pt speciation in serum of cancer patients receiving CDDP-based chemotherapy. In these samples Pt was found to be bound as follows: 87 to 93% to HSA, 2.6 to 6.4% to Tf, and 4.2 to 6.6% as unbound CDDP species.
Separation of all-
A selective, sensitive and high throughput liquid chromatography-tandem mass spectrometry (LC-ESI-MS/MS) method has been developed and validated for the chromatographic separation and quantitation of all-trans -acitretin and 13-cis -acitretin in human plasma. Sample clean-up involved solid phase extraction of both the isomers and their deuterated analogs (all-trans -acitretin-d3 and 13-cis -acitretin-d3) used as internal standards from 300 μL human plasma. Both the analytes were chromatographically separated with a resolution factor of 2.3 on a Gemini C18 (50 × 2.0 mm, 3 μ) analytical column using 10 mM ammonium acetate and acetonitrile (60 : 40, v/v) as the mobile phase. The selectivity factor (α ) of the column for the separation was 1.28, based on the capacity factors of 4.56 and 5.84 for (all-trans ) and (13-cis )-isomers respectively. The parent → product ion transitions for both the isomers (m /z 325.2 → 266.0) and IS (m /z 328.0 → 266.0) were monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring (MRM) and negative ion mode. The method was validated over the concentration range of 0.3–500 ng mL−1 for both the analytes. Stability studies were conducted in plasma to check the extent of photoisomerization under different conditions. Quantitative and consistent recovery (>92%) was obtained in the presence of l -ascorbic acid and yellow light (589 nm) for both the analytes. The matrix effect was assessed by post-column analyte infusion and the precision value (% CV) for a relative matrix effect in six different lots of plasma samples was ≤3.9% at the LLOQ levels for both the analytes. The method was successfully applied to a pivotal bioequivalence study in 48 healthy Indian subjects after oral administration of 25 mg acitretin tablet formulation under fasting conditions. To demonstrate the reproducibility in the measurement of study data, an incurred sample reanalysis was done with 270 subject samples and the % change in concentration from the initial analysis was within ±15%.
An enantioselective polyaniline-coated membrane electrode based on chiral salen Mn(
A novel ion-selective electrode for chiral determination of mandelic acid (MA) is constructed of a poly(vinyl chloride) (PVC) membrane doped with a chiral salen Mn(iii ) compound as chiral selector and coated with a chemically generated film of polyaniline (PANI). The developed sensor displays a linear response towards l -MA over a wide concentration range of 1.0 × 10−1 to 1.0 × 10−6 M with Nernstian slope of 57.6 mV per decade and the detection limit of 2.1 × 10−7 M. Ascribed to the hydration of PANI, it demonstrates a better potentiometric characteristic (especially, linear range, detective limit, response time) in contrast to the uncoated membrane based sensor.
Electro-oxidation and adsorptive stripping voltammetric determination of ephedrine and pseudoephedrine at carboxylated multi-walled carbon nanotube-modified electrode by Hamid Ahmar; Ali Reza Fakhari (pp. 812-818).
Carboxylated multi-walled carbon nanotubes (MWCNTs) were directly cast onto a glassy carbon electrode to fabricate a MWCNT-modified electrode. The modified electrode exhibited good promotion towards the electrochemical oxidation of ephedrine and pseudoephedrine with greatly enhanced peak currents. Adsorptive stripping voltammetry (AdSV) with accumulation at open circuit potential has been used for quantification of these alkaloids. The method was validated and linear over the concentration range of 1–100 μM for both ephedrine and pseudoephedrine. Under optimal experimental conditions, the limits of detection (based on 3σ) for ephedrine and pseudoephedrine were determined as 0.75 μM and 0.82 μM respectively. The proposed method was successfully applied to pseudoephedrine determination in the presence of acetaminophen or cetirizine. This method has also been used for the determination of pseudoephedrine in some pharmaceutical preparations. In addition the proposed method has been successfully used for determination of ephedrine in diluted urine as a real sample.
Laser-induced breakdown spectroscopy for determination of trace metals in aqueous solution using bamboo charcoal as a solid-phase extraction adsorbent by Dehua Zhu; Jianping Chen; Jian Lu; Xiaowu Ni (pp. 819-823).
Bamboo charcoal, a renewable material with special microporous and biological characteristics, has been widely used to remove heavy metals from liquid solution due to its excellent adsorption properties. In this paper, laser-induced breakdown spectroscopy (LIBS) has been performed to detect trace metal elements (Pb) in aqueous solution by using bamboo charcoal as a solid-phase extraction adsorbent. With this method, the liquid analysis was transformed to solid surface analysis which could overcome the sensitivity drawbacks in liquid sample analysis. The calibration curve was constructed by using the standard solution with variable concentrations and the limit of detection (LOD) was estimated for Pb. The influence of adsorption capacity of bamboo charcoal on the calibration curve was discussed. Finally this system has also been used for quantitative analysis of wastewater. Then the results were compared with ICP-AES and showed a good correlation.
Optimization of a vanillin assay for determination of anthocyanins using D-optimal design by Mohammad Reza Khoshayand; Tahmineh Roohi; Ghazaleh Moghaddam; Feryar Khoshayand; Parviz Shahbazikhah; Mohammad Reza Oveisi; Mannan Hajimahmoodi (pp. 824-829).
The vanillin assay is a spectrophotometric method for anthocyanin determination that is simple, quick and inexpensive. The method is preferred because of its high sensitivity, specificity and simplicity; however, the results of this test are influenced by several factors. Hence, a D-optimal experimental design approach was investigated to simultaneously, without loss of information, optimize five factors that influence the vanillin assay: acid normality, vanillin concentration, temperature, time and acid type. Further optimization with a D-optimal design and response surface analysis (RSM) showed that a second-order polynomial model fit the experimental data appropriately. The optimum conditions were determined as follows: the optimal acid type was H2 SO4 with a normality of 7.00, vanillin concentration of 1.50% w/v, temperature of 22.0 °C, and reaction duration of 21.0 min. Using these conditions, the absorbance maximum predicted using the model was calculated to be 0.71. Good agreement between the observed values and the values predicted by the model confirmed the statistical significance of the model and the model's ability to predict the optimum conditions.
Application of ultrasound-assisted emulsification microextraction followed by gas chromatography for determination of organophosphorus pesticides in water and soil samples by Yaser Abdollahzadeh; Yadollah Yamini; Ali Jabbari; Ali Esrafili; Mohammad Rezaee (pp. 830-837).
In the present study a fast, simple and efficient method for determination of organophosphorus pesticides (OPPs) in water and soil samples was developed by using ultrasound assisted emulsification microextraction (USAEME) based on applying low density organic solvents. Fourteen microlitres of toluene was injected slowly into a 12 mL home-designed centrifuge glass vial containing an aqueous sample that was located inside the ultrasonic water bath. The formed emulsion was centrifuged and 2 μL of separated toluene (about 4 μL) was injected into a gas chromatographic instrument equipped with a flame ionization detector for analysis. Under the optimum conditions, preconcentration factors of 2390 and 1390 were obtained for diazinon and chlorpyrifos respectively. The method performance was studied in terms of linear dynamic range (LDRs from 0.01 μg L−1 to 100 μg L−1), linearity (r 2
Separation of lipopolysaccharides containing different fatty acid chains using hydrophobic interaction chromatography by Ke Ren; Ye Li; Feng Shi; Xiaoyuan Wang (pp. 838-843).
Lipopolysaccharides, known as endotoxins, are major components in the outer membrane of most Gram-negative bacteria. Because of their amphipathic property, it is difficult to separate lipopolysaccharides. In this study, hydrophobic interaction chromatography was used for the separation of lipopolysaccharides containing different numbers of fatty acid chains. Three species of lipopolysaccharides were extracted from Escherichia coli W3110, MLK1067, and MKV15b, respectively. Their interactions with three types of hydrophobic matrixes Butyl-Sepharose, Phenyl-Sepharose and Octyl-Sepharose were investigated. Several organic solvents were used to elute the bound lipopolysaccharides from different matrixes. Butyl-Sepharose, propyl alcohol and 0.8 mol l−1 sodium acetate (pH 4.5) loading buffer were chosen for the best separation system, and lipopolysaccharides containing different fatty acid chains were separated. This system might be useful for removing the contaminated lipopolysaccharides from proteins produced by E. coli , or separating different species of lipopolysaccharides.
Comparison of subcritical water extraction and microwave-assisted water extraction for the determination of chlorophenols in polluted lake sediments by Li Wang; Linling Wang; Zhu Miao; Xiumei Shao; Jing Chen; Xiaohua Lu (pp. 844-848).
Two environmentally friendly sample preparation methods, subcritical water extraction (SWE) and microwave-assisted water extraction (MAWE) coupled to the gas chromatography with electron capture detector (GC-ECD), were evaluated and optimized for the sensitive, selective and solvent-free determination of four chlorophenols (2-chlorophenol, 2,4-dichlorophenol, 4-chlorophenol and pentachlorophenol) in polluted Ya-Er Lake sediments. An orthogonal array design L9 (33) was applied to select the optimum conditions for SWE. The best results as regards sensitivity, repeatability and analyte recovery were obtained using SWE with 9 mL of sodium hydroxide solution (pH 9), at 150 °C for 80 min. The best extraction conditions for MAWE were obtained by using the same extractant as SWE at 900 W and 0.2 MPa for 6 min. Under final working conditions, satisfactory recoveries of individual chlorophenols (CPs) were obtained in the range of 77.7–113.0% and 83.5–104.7% for SWE and MAWE respectively. The effectiveness of the extraction conditions proposed in both methods was evaluated for the extraction of 2,4-DCP in lake sediments with different sample characteristics such as organic carbon and water content. The results indicated that sediments containing relatively low amounts of organic carbon can be quantitatively extracted by both extraction methods. For sediments with larger amounts of organic carbon, the MAWE-based method showed a little better result for analyte recovery than SWE.
Simultaneous cyclic voltammetric determination of norepinephrine, ascorbic acid and uric acid using TX-100 modified carbon paste electrode by B. N. Chandrashekar; B. E. Kumara Swamy (pp. 849-854).
A sensitive and selective electrochemical method for the determination of norepinephrine (NE) using TX-100 modified carbon paste electrode was developed. The TX-100 modified carbon paste electrode shows excellent electrocatalytic activity towards the oxidation of NE in phosphate buffer solution (pH 7.0). The linear range of 0.5 × 10−4 to 2.0 × 10−4 M and detection limit of 5 × 10−6 M were observed at pH 7.0 phosphate buffer solution. The interference studies showed that the modified electrode exhibits excellent selectivity in the presence of large excess of ascorbic acid (AA) and uric acid (UA). The separation of the oxidation peak potentials for NE–AA and NE–UA were about 0.16 V and 0.11 V, respectively. The differences were large enough to determine AA, NE and UA individually and simultaneously. This work provides a simple and easy approach to selectively detect norepinephrine in the presence of ascorbic acid and uric acid in physiological samples.
Photo-oxidation using UV radiation as a sample preparation procedure for the determination of copper in fruit juices by flame atomic absorption spectrometry by Geovani C. Brandão; Márcio de O. Aureliano; Maria Celeste da Silva Sauthier; Walter N. L. dos Santos (pp. 855-858).
The present work proposes the photo-oxidation using UV radiation/H2 O2 as an alternative procedure for pretreatment of industrialized fruit juice samples for determination of copper by flame atomic absorption spectrometry (FAAS). For optimization of the photo-oxidation procedure the following variables were studied: pH and volume of buffer solution, volume of concentrated hydrogen peroxide and irradiation time. The sample degradation was monitored by molecular absorption spectrometry in the spectral range of 200–800 nm. The established conditions were: pH 10, volume of buffer of 1.0 mL, volume of concentrated hydrogen peroxide of 1.5 mL and irradiation time of 90 min, for a 5 mL volume of the photo-digested sample. An external calibration technique with aqueous standard was used for copper quantification. Under these conditions, the method allows the copper determination with limits of detection and quantification of 7 and 22 μg L−1, respectively. The precision, expressed as relative standard deviation (RSD), was 1.43 and 0.27% for copper concentrations of 0.2 and 2.0 μg mL−1, respectively. The accuracy of the method was evaluated for five industrialized fruit juice samples (orange, grape, mango, passion fruit and peach) and the results compared with those obtained after acid digestion of the samples and determination by FAAS. No significant difference was observed between the results obtained by both procedures, applying a paired t -test at the 95% confidence level.
Analysis of mequindox and its two metabolites in swine liver by UPLC-MS/MS by Kaili Liu; Xingyuan Cao; Zhanhui Wang; Linxia Li; Jianzhong Shen; Linli Cheng; Suxia Zhang (pp. 859-863).
A new ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was developed for the determination of mequindox (MEQ) and its two metabolites (1-desoxymequindox and 1, 4-bisdesoxymequindox, 1-DMEQ and BDMEQ) in swine liver. This method was validated on the basis of Commission Decision 2002/657/EC. Target analytes were extracted from swine liver with acid acetonitrile, purified by an Oasis MAX cartridge, and separated by UPLC. The chromatography total time was less than 8 min with gradient elution of 0.1% formic acid in methanol. Data acquisition was carried out by electrospray ionization tandem mass spectrometry (ESI/MS/MS) operated in a multiple reaction monitoring mode. At fortified levels from 2 to 100 μg kg−1 in swine liver, recoveries of target analytes ranged from 80% to 85% with the intra-day coefficient of variation (CV) being ≤ 14.48% and inter-day CV ≤ 14.53%, respectively. The limit of detection (LOD) ranged from 0.58 to 1.02 μg kg−1 and the limit of quantification (LOQ) range was 1.93 to 3.40 μg kg−1 for each analyte. The result indicated that this method was specific, sensitive, and suitable for the quantification and conformation of MEQ and its two metabolites in swine liver.
Repeated capillary electrophoresis separations conducted on a commercial DNA chip by Wilson Chim; Paul C. H. Li (pp. 864-868).
Multi-sample microchip capillary electrophoresis separations of a DNA sample (i.e. pUC18 DNA Hae III restriction digest) have been conducted on a commercial bioanalyzer. According to the vendor's specifications, a new chip must be used and the gel–dye mix must be used within 2 weeks for the best possible results. However, such a requirement of new chips and fresh reagents is quite costly, especially during preliminary research work, or instructional experiments in teaching labs. Therefore, we have developed a method to clean the microchip, so that the same DNA chip can be inspected and re-used. Our experimental data show that the CE separations conducted on a new chip and on a cleaned chip are comparable without loss in sizing accuracy and reproducibility. The gel–dye mix can also be used many times, longer than 2 weeks as specified by the vendor until the gel–dye changes color. This method will provide cost-saving advantage to laboratories during training and preliminary research work.
Problems and improvements of the regulated analyses method on GC for nonyl phenol isomers by Atsushi Kobayashi; Yusuke Kitahara; Kunitaka Toyota; Shigeru Suzuki; Takuya Kubo; Ken Hosoya (pp. 869-872).
We report problems and improvements of a regulated analytical GC method supported by ISO/DIS 24293 for nonyl phenol isomers (NPs). The variations of peak area and recovery of NPs were found on a regulated GC method which 4-n-nonyl phenol-2,3,5,6-d4 (4-np-d) and phenanthrene-d10 (fnt-d) were utilized as surrogate compounds with syringe spiking. Furthermore, we investigated the relative recovery by the continuous injection of NPs, 4-np-d, and fnt-d, then the decrease rate of peak area of each compound was different although all peaks were gradually decreased. Consequently, the decrease rates of NPs and 4-np-d were higher, and the relative recovery of NPs were also decreased. After cutting off the GC column (about 50 cm) and replacement of an injection insert, the peak areas of compounds were completely recovered. Therefore, we anticipate that the problem was caused by adsorption or degradation of NPs in the inlet area. Additionally, a similar decrease of peak area was observed on the pretreated real samples by the effect of matrix.
Back cover (pp. 873-874).
This feature review provides an overview of the state-of the art and recent developments in tip-enhanced Raman spectroscopy (TERS), in-depth information about the different available types of instruments including their (dis-)advantages and capabilities as well as a short glance at a number of samples that have recently been investigated using TERS. Issues concerning the progression of TERS from point spectroscopy to an imaging technique are discussed, as well as problems arising from background and contamination signals. This review is concluded with a short TERS ‘user guideline’, trying to aid researchers new in the field to properly align and test their own TERS setups. Finally, a short outlook is given and some critical issues are raised that need to be solved by the community sooner or later, in order to promote TERS towards a ‘push-button’ operation.