Analytical Methods (v.5, #2)
Front cover (293-293).
Inside front cover (294-294).
Contents list (295-308).
Cosmetic ingredients: from the cosmetic to the human body and the environment by Alberto Chisvert; Amparo Salvador (309-310).
Extractive electrospray ionization mass spectrometry for direct characterization of cosmetic products by Xinglei Zhang; Nannan Wang; Yafei Zhou; Yan Liu; Jinghua Zhang; Huanwen Chen (311-315).
As daily necessities in large populations, quality control is mandatory for cosmetic products in order to guarantee their efficacy and safety. Traditionally, analysis of cosmetics is slow due to the dedicated sample pretreatment steps required. With neutral desorption extractive electrospray ionization mass spectrometry (ND-EESI-MS), trace illicit additives including sunscreens, hormones, and antibiotics etc. in many types of cosmetics can be quantitatively detected at sub-low-ppb levels, requiring no sample pretreatment. This review briefly summarizes the technique development and application of ND-EESI-MS for the rapid analysis of cosmetic products. The future trend of ND-EESI-MS for cosmetic analysis is also concisely discussed.
Fragrances: from essential oils to the human body and atmospheric aerosols by Lai-Hao Wang (316-322).
An overview of the extraction methods is given by comparing headspace, liquid extraction, solid-phase extraction, solid-phase microextraction, sorptive tape extraction, ultrasound-assisted extraction, pressurized-liquid extraction and matrix solid-phase dispersion extraction (MSPD) for determination of 26 fragrance allergens in essential oils, cosmetics, indoor air and environmental water samples. I also present a description of allergic contact dermatitis caused by fragrances, and an assessment of percutaneous absorption or inhalation of fragrance allergens in cosmetics and indoor air is presented.
Current trends in liquid–liquid and solid–liquid extraction for cosmetic analysis: a review by N. Cabaleiro; I. de la Calle; C. Bendicho; I. Lavilla (323-340).
The aim of this review is to discuss and compare the current trends in liquid–liquid and solid–liquid extraction procedures applied to the analysis of cosmetics. Although classical sample preparation procedures are mostly used in labs, the new trends in sample preparation that provide more effective analyte extractions from these complex matrices are gradually being introduced. Drawbacks inherent to conventional or classical extraction procedures in cosmetic samples are also considered. A detailed revision in the period January 1992 to March 2012 about current sample preparation techniques such as liquid-phase microextraction (LPME), microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), accelerated solvent extraction (ASE) and supercritical fluid extraction (SFE) applied to cosmetics is given. In general, these procedures have given rise to faster, greener and more effective extraction techniques for cosmetic analysis with regard to conventional procedures.
Analytical methods for the characterization and determination of nonionic surfactants in cosmetics and environmental matrices by M. Beneito-Cambra; J. M. Herrero-Martínez; G. Ramis-Ramos (341-354).
Nonionic synthetic surfactants, constituted of an assortment of classes, are common ingredients of industrial, household and body-care products. Alone or in combination with anionic surfactants, they perform a variety of functions including cleaning action, emulsification, skin conditioning, appearance and consistency modification, solubilization and dispersing agents. By far fatty alcohol ethoxylates (AEs) and alkylphenol ethoxylates (APEs) are more extensively used than any other nonionic surfactant class; however, works appearing in the literature making reference to the analysis of other nonionic surfactant classes have also been collected in this review. The production volume worldwide of AEs and APEs, and consequently their environmental impact, is very high. Although readily biodegraded, stable non-ethoxylated lipophilic residues remain for long periods in the aquatic environment and sediments. In addition to its harmful impact on the food chain, there is also concern on landscape spoiling, particularly in coastal areas. The analytical methods used for quality control of nonionic surfactants in industrial products and in environmental samples are revised and commented upon here. The fundamentals and characteristics of the methods, including their most relevant operative and statistical aspects, are briefly presented. Attention is also paid to the techniques used to extract and preconcentrate the analytes from liquid and solid environmental samples.
Liquid chromatography-tandem mass spectrometry for the multi-residue analysis of organic UV filters and their transformation products in the aquatic environment by Pablo Gago-Ferrero; M. Silvia Díaz-Cruz; Damià Barceló (355-366).
UV-absorbing compounds are environmental pollutants of recent concern and the requirements for analytical methods are mainly driven by the low concentrations found in aqueous and solid environmental samples. In the current article, a review of the liquid chromatography-tandem mass spectrometry (LC-MS/MS) based methods published so far for the determination of organic UV filters in the environment is presented. UV filters included in this overview belong to different families and are benzophenones, camphor derivatives, cinnamates, crylenes, benzimidazole derivatives, p-aminobenzoic acid and derivatives, dibenzoyl methane derivatives, salicylates and triazines, as well as their main transformation products. Advanced aspects of current LC-MS/MS methodology, including sample preparation and matrix effects, for the analysis of water, sludge, sediments and biota samples are discussed.
A solid-phase extraction liquid chromatography-tandem mass spectrometry method for the percutaneous absorption assessment of 3-(4′-methylbenzylidene)camphor via human urine analysis by Zacarías León-González; Alberto Chisvert; Isabel Fernández; Amparo Salvador (367-375).
The UV filter 3-(4′-methylbenzylidene)camphor (MBC) is a common ingredient in sunscreen cosmetic products. However, different in vitro and in vivo studies suggest that MBC can cause endocrine disrupting effects. This report focuses on the development of an analytical method based on solid-phase extraction (SPE) prior to liquid chromatography tandem mass spectrometry (LC-MS/MS) for the determination of MBC and its main phase I metabolite, named 3-(4′-carboxybenzylidene)camphor (CBC), in urine from users of sunscreen cosmetic products containing MBC. The formation of phase II metabolites (i.e., glucuronide and sulphate conjugates) was also considered by carrying out an enzymatic hydrolysis of the urine samples. The standard addition calibration method was used to quantify the target analytes in order to correct the matrix effects observed. In this way, statistically accurate results were obtained when the developed SPE-LC-MS/MS method was applied to the analysis of fortified analytes-free urine samples. The limits of detection were 6 ± 2 ng mL−1 for MBC and 6 ± 1 ng mL−1 for CBC, and the intra- and inter-day variability of the method, expressed as relative standard deviation, were in the range of 1.3–2.0% and 4.5–7.7%, respectively, depending on the analyte. The analytical method was satisfactorily applied to the analysis of real urine samples from a volunteer that was subjected to repeated applications of a sunscreen cosmetic containing MBC, showing that the major contribution to the excretion of MBC corresponded to the glucuronide conjugated species of CBC. Furthermore, the second main phase I metabolite of MBC, named 3-(4′-carboxybenzylidene)hydroxycamphor (CBC-OH), which also predominates in its glucuronide conjugate species in urine samples, was identified and detected.
Measurement of iodide and caffeine content in cellulite reduction cosmetic products sold in the European market by Emilia Marchei; Daniela De Orsi; Carmine Guarino; Stefano Dorato; Roberta Pacifici; Simona Pichini (376-383).
Two simple liquid chromatography (LC) separation methods coupled with ultraviolet diode array (UV-DAD) and an electrospray ionisation mass spectrometry (ESI-MS) detection have been developed for the determination of caffeine and iodide content in cellulite reduction cosmetic products. The presence of these substances in cosmetics available in the market should be taken into account in order not to exceed the limits allowed when co-administered with drugs, dietary supplements in order to avoid eventual acute or chronic intoxications. The compounds were separated by reversed phase chromatography with water (0.02% trifluoroacetic acid) and acetonitrile gradient elution and detected by UV-DAD at 254 nm and by ESI-MS ionization mode positive for caffeine and negative for iodide. Paracetamol was used as internal standard. Linearity was studied with UV-DAD in the 5 (10 for iodide) to 200 μg g−1 range, and with ESI-MS in the 0.1 (0.2 for iodide) to 2 μg g−1 range. Good determination coefficients (r2 = 0.99) were found in both UV-DAD and ESI-MS detection. At three concentrations spanning the linear dynamic ranges of both UV-DAD and ESI-MS assays, mean recoveries were always higher than 90% for the different analytes and intra-assay and inter-assay precisions were always better than 15%. This method was successfully applied to the analysis of substances under investigation in cellulite reduction cosmetic products freely sold in European herbalist shops, perfumeries and supermarkets.
A novel outlook on detecting microbial contamination in cosmetic products: analysis of biomarker volatile compounds by solid-phase microextraction gas chromatography-mass spectrometry by Gerardo Alvarez-Rivera; Trinidad De Miguel; Maria Llompart; Carmen Garcia-Jares; Tomas Gonzalez Villa; Marta Lores (384-393).
Cosmetic companies are required to control the optimal preservation of their commercial products, since microbial contamination in cosmetics represents an important risk for consumer health. Fast methods for cosmetic microbiological testing are of great industrial importance, facilitating the rapid release of products into the market. In this work, a novel approach based on microbial volatile organic compound (MVOC) analysis was proposed, for the first time, as an alternative method for the rapid detection of microbial contamination in cosmetics by SPME-GC/MS. Microbial volatiles from typical contaminants of cosmetic products were sampled above the headspace of standard cultures and from incubated samples. The volatile fraction analysis revealed, amongst other compounds, the presence of several odd-numbered carbon (C9–C15) methyl ketones and alkanols, which have been reported as characteristic compounds of bacterial origin. Some of them were found both in pure bacterial cultures and in the samples. However, other compounds not seen in cultures were seen in the cosmetics, suggesting that substrate is a very influential factor. These results also suggest that it could be clearly feasible to qualitatively identify viable microorganisms in cosmetics or even specific strains by detecting their volatile biomarkers, which would be a rewarding complement for other rapid methods. The results of the kinetic study performed on real samples further suggest the possibility of monitoring the contamination progress.
Screening of cosmetic ingredients from authentic formulations and environmental samples with desorption electrospray ionization mass spectrometry by Jamie L. Nizzia; Adam E. O'Leary; Alain T. Ton; Christopher C. Mulligan (394-401).
A rapid and sensitive method based on desorption electrospray ionization mass spectrometry (DESI-MS) has been utilized for the detection of chemicals related to cosmetic products without prior preparation. DESI-MS was used to rapidly screen target compounds at ambient conditions, allowing the investigation of surface-bound residues, complex chemical matrices, and components of authentic cosmetic formulations. This high-throughput method routinely achieved low nanogram detection limits, and quantitative ability was demonstrated with decent linearity and precision. Continuous, direct analysis of cosmetic impurities in drinking water matrices was also validated, implementing thermal assistance into the ionization source design to increase overall sensitivity.
Heavy metals in powder-based cosmetics quantified by ICP-MS: an approach for estimating measurement uncertainty by Beatrice Bocca; Giovanni Forte; Anna Pino; Alessandro Alimonti (402-408).
A method based on microwave digestion and high resolution mass spectrometry was developed for the determination of Cd, Co, Cr, Ni and Pb in powder cosmetic samples. The procedure was validated in-house at the native concentration found in the cosmetic and at three fortification levels. Measurement uncertainties were calculated using data generated from repeatability, recovery and calibration linearity studies. The mean repeatability estimates were ≤11% for Cd, Co, Ni and Pb and ≤25% for Cr. The average recoveries ranged between 70% (Cr) and 112% (Pb). The expanded uncertainties (k = 2) of the method were between 34% (Cd) and 63% (Cr) at the native concentration and from 14% (Cd and Pb) to 34% (Cr) at the highest fortification level. The results accompanied by their uncertainty statements in the powder cosmetic were as follows (in mg kg−1): Cd, 0.026 ± 0.009; Co, 1.61 ± 0.60; Cr, 3.00 ± 1.88; Ni, 6.87 ± 2.53; Pb, 0.25 ± 0.09.
A rapid and sensitive gas chromatography-mass spectrometry method for the quality control of perfumes: simultaneous determination of phthalates by M. López-Nogueroles; J. L. Benedé; A. Chisvert; A. Salvador (409-415).
A rapid and sensitive analytical gas chromatography-mass spectrometry (GC-MS) method for perfume analysis to determine the phthalates banned by the European Union Regulation on cosmetic samples is presented. This method has been tested in commercial alcoholic perfume samples for the determination of the following seven phthalates: dibutyl phthalate, bis(2-ethylhexyl) phthalate, bis(2-methoxyethyl) phthalate, n-pentyl-isopentylphthalate, di-n-pentyl phthalate, diisopentylphthalate and benzyl butyl phthalate. Sample evaporation and redissolution in ethanol is carried out before GC-MS analysis, with no dilution of the sample. External calibration and standard addition calibration are compared to detect possible matrix effects. External calibration could provide good results in some cases but standard addition calibration is recommended as matrix effects are observed in many cases in the determination of the target phthalates. The accuracy of the method has been proven by the analysis of quality control samples prepared from commercial free phthalate perfumes after spiking with known concentrations of the analytes. Accurate results were obtained with limits of detection in the ng mL−1 range and good repeatability (relative standard deviations lower than 6%). The method was satisfactorily applied to the analysis of commercial perfume samples, and the results revealed considerable amounts of dibutyl phthalate and bis(2-ethylhexyl) phthalate in some of the analyzed samples.
Content of suspected allergens and preservatives in marketed baby and child care products by Lucia Sanchez-Prado; Gerardo Alvarez-Rivera; J. Pablo Lamas; Maria Llompart; Marta Lores; Carmen Garcia-Jares (416-427).
Baby hygiene and care products are daily used cosmetics intended to cleanse and protect the delicate skin of babies. However, the formulation of this kind of product may contain a highly complex mixture of chemicals such as fragrances and preservatives, some of which have been shown to act as strong sensitizers and allergens. As a result of the widespread use of these compounds in baby care products, there is an increasing social concern about the possible harmful consequences that the exposure to some of these ingredients could have on babies' health. To ensure a high level of protection, in the European framework, both preservatives and suspected fragrance allergens are subject to restrictions according to the EU Cosmetic Directive. Due to the special sensitivity of infants, further restrictions and conditions are applied to these substances in cosmetics intended to be used for children under three. In this work a wide analytical screening of a great variety of rinse-off and leave-on products and personal care products (PCPs) targeted for infant care was accomplished. Matrix-solid phase dispersion (MSPD) and pressurized liquid extraction (PLE) procedures followed by gas chromatography-mass spectrometry (GC-MS) were successfully applied for the determination of 38 targets (25 suspected allergen fragrances and 13 preservatives). Although compliance with the current EU Cosmetic Regulation was fulfilled regarding the fragrances and preservatives limits, the results reveal the high allergenic content in some products intended to be in prolonged contact with the baby's skin. The results further highlight that some of the target compounds have been omitted in the label.
Emerging pollutants in aquatic environments: monitoring of UV filters in urban wastewater treatment plants by Emanuele Magi; Carlo Scapolla; Marina Di Carro; Paola Rivaro; Kieu Thi Ngoc Nguyen (428-433).
Six UV filters – benzophenone-3 (BP-3), octocrylene (OC), ethylhexyl dimethyl p-aminobenzoate (OD-PABA), ethylhexyl methoxycinnamate (EHMC), ethylhexyl salicylate (EHS) and homosalate (HMS) – with endocrine disrupting potential were monitored in different wastewater treatment plants (WWTPs) located in Genoa, Italy. The influent and effluent samples were collected once a month from April to September 2011. The analytes were determined by stir bar sorptive extraction followed by liquid desorption (SBSE-LD) combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Quantitative analysis was performed in triggered MRM (tMRM), which allowed improvement of specificity without compromising sensitivity. In the inlet samples four analytes were detected; in particular BP-3, OC, EHMC, and OD-PABA were in the range of 4–163, 12–390, 23–68, and 2–4 ng L−1, respectively. Measured concentrations indicated variability of UV filter inputs to WWTPs, with higher loads during the warmer months. A highly positive correlation was found between air temperature and the measured concentration of OC and BP-3. Only BP-3 and OC were detected in some effluent samples, with considerably lower concentrations. The removal efficiencies of the plants were in the range of 64 to >99% and 94 to >99% for BP-3 and OC, respectively.
A simple and sensitive intramolecular charge transfer fluorescent probe to detect CN− in aqueous media and living cells by Mohammad Shahid; Arvind Misra (434-437).
The optical behavior of a simple intramolecular charge transfer (ICT) fluorescent probe 1 has been described to detect cyanide (CN−) selectively for the first time in solution and living cells. The strong emission displayed by 1 is attributed to a decrease in ICT from anthracene to dicyanovinyl group. The change in color of the solution was visible to the naked eye. Probe 1 forms a 1:1 adduct with CN− with detection limit of 26 ppb.
Label-free fluorescence turn-on detection of Pb2+ based on AIE-active quaternary ammonium salt of 9,10-distyrylanthracene by Xing Li; Bin Xu; Hongguang Lu; Zilong Wang; Jibo Zhang; Yan Zhang; Yujie Dong; Ke Ma; Shanpeng Wen; Wenjing Tian (438-441).
A label-free fluorescence turn-on approach for the selective sensing of Pb2+ based on quaternary ammonium salt of 9,10-distyrylanthracene with aggregation-induced emission (AIE) property was developed through Pb2+-induced allosteric G-quadruplex (G4). The method is simple, easy to operate, cost-effective, and provides good sensitivity and selectivity.
A rhodamine–naphthalene conjugate as a FRET based sensor for Cr3+ and Fe3+ with cell staining application by Sisir Lohar; Arnab Banerjee; Animesh Sahana; Avishek Banik; Subhra Kanti Mukhopadhyay; Debasis Das (442-445).
A FRET based fluorescent probe (RDENAPH) containing a 2-hydroxynaphthalene unit as a donor and rhodamine B as an acceptor can discriminate Cr3+ and Fe3+ from other common metal ions through ratiometric sensing. The FRET process has been established from absorption, emission and lifetime decay studies. The probe can stain intracellular Cr3+ and Fe3+ in contaminated living cells.
TanA: a fluorogenic probe for thiaminase activity by Wanjun Zhu; James L. Zajicek; Donald E. Tillitt; Timothy E. Glass (446-448).
A fluorogenic thiamine analogue is presented as a fluorescent probe for thiaminase activity. The emission of the fluorophore is quenched by photoinduced electron transfer (PET) to the N-substituted pyridinium portion of the probe. Action of the enzyme releases the free pyridine group causing a substantial increase in fluorescence.
Release of iodine from organic matter in natural water by K2S2O8 oxidation for 129I determination by Haijun Dang; Xiaolin Hou; Per Roos; Sven P. Nielsen (449-456).
Accelerator mass spectrometry is the only method for measuring 129I in low level environmental samples. In this method, it is essential to convert organic associated iodine into inorganic form for the determination of total 129I or organic 129I because AgI is usually adopted as a target for AMS measurement of 129I. The chemical oxidative method to release iodine from organic matter in natural water was investigated using anion exchange chromatography and CHCl3 extraction methods. K2S2O8 was confirmed to be an ideal oxidative reagent for decomposing organic matters and converting organic iodine to inorganic form. More than 95% of iodine in natural water can be separated by solvent extraction after oxidation under optimal conditions, and the isotopic exchange of iodine in inorganic and organic forms was well completed during the oxidation, being able to result in an identical 129I/127I ratio as in the original water. Our works indicate that the reported chemical oxidation method is a suitable approach for releasing organic associated iodine in natural water to allow separation of iodine and preparation of the AgI target for AMS measurement.
Aqueous synthesis of Ag+ doped CdS quantum dots and its application in H2O2 sensing by Lin Lin; Yaqiong Wen; Yanxia Liang; Na Zhang; Dan Xiao (457-464).
A novel detection system based on the fluorescence quenching of CdS–Ag2S quantum dots (QDs) was designed for the direct measurement of hydrogen peroxide (H2O2). Experimental results showed that an excellent response to the concentrations of H2O2 was found within the range from 1.0 × 10−6 to 1.0 × 10−2 M with a detection limit of 3.0 × 10−7 M. The CdS–Ag2S QDs have been synthesized at room temperature in an aqueous solution using thioglycollic acid as stabilizing agents, which were spectra-tunable and water-soluble. Different influencing factors including pH, variable ratio of [Cd2+]/[S2−], dopant concentration, precursor concentration, and aging time of CdS–Ag2S QDs were studied. It was found that the emission colors of the prepared CdS–Ag2S QDs could be readily tuned from green to red by varying pH. Furthermore, the CdS–Ag2S QDs were characterized by fluorescence and time-resolved emission spectroscopy, TEM, EDX, XRD, XPS, ESR. The long decay times, large surface area, and good chemical stability of the CdS–Ag2S QDs have made this material suitable as a fluorescence probe.
Multivariate analysis based on chromatographic fingerprinting for the evaluation of batch-to-batch reproducibility in traditional Chinese medicinal production by Haoshu Xiong; Xueyong Qi; Haibin Qu (465-473).
In traditional Chinese medicinal production, a high degree of batch-to-batch reproducibility is required to achieve successful batches that meet the quality standard of traditional Chinese medicinal preparations (TCMPs). In this paper, multivariate statistical process monitoring (MSPM) based on chromatographic fingerprinting has been introduced to evaluate the batch-to-batch reproducibility of TCMPs. A commonly used TCMP product, Sheng-Mai-Yin (SMY) oral liquid, is selected as a typical example to demonstrate the feasibility of this approach. A number of batches are prepared through normal operation procedures to simulate the common-cause variations induced by preparation days, herb materials, and operators. Another number of abnormal batches are designed to simulate different types of deviations, including the changes of herb material quality attributes and abnormal operation conditions. The high-performance liquid chromatographic fingerprinting is used to construct the integrative pattern of SMY products. A principle component analysis model is established of the fingerprint data of the normal batches. Multivariate (Hotelling T2 and DModX) control charts are successfully applied to monitor the abnormal batches. As an effective multivariate analysis method in this study, MSPM based on chromatographic fingerprinting promises great applications in batch monitoring and evaluation for the production of TCMPs.
A comparative fingerprint study using high-performance liquid chromatography, ultraviolet, and near-infrared spectroscopy to evaluate the quality consistency of Danshen injections produced by different manufacturers by Hongxia Huang; Haibin Qu (474-482).
Very few efforts have been directed toward interpreting the differences between chromatographic and spectroscopic fingerprints for the purpose of quality control, although similarity analysis based on fingerprints is commonly applied to quality consistency evaluation of herbal medicines (HM). In the current study, comparative evaluation of high-performance liquid chromatography (HPLC), ultraviolet (UV), and near-infrared (NIR) fingerprint techniques combined with chemometric methods has been conducted to control the quality of Chinese herbal injections. A set of Danshen injections (DSI) are chosen as an example of the relevance to contemporary HM. Similarity analysis by principal component analysis, identification using linear discriminant analysis and k nearest neighbor classifiers, and control charts based on Hotelling's T2 and DModX statistics are employed to evaluate the quality consistency of the DSI samples from three different manufacturers. The results in this study demonstrate that the UV spectroscopy technique combined with chemometric methods is useful for the identity and consistency evaluation of DSI. Such an approach is believed to be equally applicable to other HM.
Platinum/graphene functionalized by PDDA as a novel enzyme carrier for hydrogen peroxide biosensor by Zonghua Wang; Jianfei Xia; Xinmei Guo; Yanzhi Xia; Shuyan Yao; Feifei Zhang; Yanhui Li; Linhua Xia (483-488).
In this work, we fabricated platinum nanoparticles/graphene nanohybrids (Pt/G) via in situ reduction of PtCl62− in the presence of poly(diallyldimethylammonium chloride)-modified G, and used them as a support for the immobilization of horseradish peroxidase to construct a biosensor (HRP/Pt/G/glassy carbon (GC)) for H2O2. Poly(diallyldimethylammonium chloride) (PDDA), a positively charged polyelectrolyte, created a net positive charge on the carbon atoms in the all-carbon graphene plane via intermolecular charge transfer. Then the resultant positively charged PDDA-modified G was used for sequential self-assembly with negatively charged PtCl62− which could be reduced in situ. The Pt/G hybrid provides an effective atmosphere for maintaining the bioactivity of HRP, and also acts as a bridge for the transfer of electrons between the active center of HRP and the electrode surface, thereby resulting in a more rapid transmission of electrons. The HRP/Pt/G/GC showed high sensitivity and fast response for electrocatalytic reduction towards H2O2, revealing that Pt/G effectively reinforced the immobilization of HRP and enhanced the utilization of HRP. The linear range for H2O2 was estimated to be from 3.0 × 10−6 mol L−1 to 5.2 × 10−3 mol L−1 with a detection limit of 5.0 × 10−9 mol L−1. Moreover, the biosensor exhibited good reproducibility and long-term stability.
An environmentally friendly photometric procedure for ammonium determination in rainwater employing a multicommutation approach by Gláucia P. Vieira; Carla C. Crispino; Sheila R. W. Perdigão; Boaventura F. Reis (489-495).
In the present work, an automated procedure for photometric ammonium determination in rainwater using a multicommuted flow analysis approach is proposed. A homemade LED based photometer was designed to couple a flow cell with a path length of 100 mm in order to improve sensitivity. After establishing the adequate operational conditions, the proposed procedure was applied for the determination of ammonium in rainwater samples. The assessment of accuracy, by applying the paired t-test between these results and the results obtained using a reference method, showed that there is no significant difference at a 95% confidence level. Other useful features such as a linear response ranging from 0.05 to 1.20 mg L−1 NH4+; a detection limit of 19 μg L−1 NH4+; a blank relative standard deviation (n = 15) of 2.9%; a reagent consumption of 1.5 mg sodium salicylate and 0.15 mg sodium nitroprusside; a waste generation of 3.1 mL per determination; and a sampling throughput of 38 determinations per hour were also achieved.
Flow injection liquid-liquid microextraction of CL-15 explosive and its fluorimetry determination in water samples by Mojtaba Shamsipur; Mir Mahdi Zahedi; Seied Mahdi Pourmortazavi; Iraj Kohsari (496-502).
CL-15 or 1,4,5,8-tetranitro-1,4,5,8,tetraazadifurazano-[3,4-c][3,4-H] decalin, is a high energetic explosive. This investigation showed that this compound due to the elimination of an H+ from its structure converts to have a sensitive and unique fluorophore center which changes color as pH changes. This behavior introduces a rapid and simple way for its detection. In the present study, a flow injection liquid-liquid microextraction method was developed to preconcentrate and determine by fluorimetry CL-15 explosive. After optimization of the main parameters affecting the FI-LLME process efficiency, the proposed method had a linear range of 0.28–12.06 μg mL−1 with R2 = 0.9987, LOD = 0.066 μg mL−1, Ef = 27.8 and %RSD = 5.12%; while optical conditions were: Ex 380 nm, Em 480 nm, medium sensitivity. Other operational conditions such as time of separation, separation coil diameter and organic solvent volume were 1 min, 3 m and 150 μL, respectively. In comparison with conventional analysis methods, this method provides some advantages such as rapidity, cleanliness, and uses only a small volume of organic solvent. Finally, the performance of the method for efficient extraction of analyte from real aqueous samples in the presence of some similar explosives was investigated.
Fragmentation of chromophore labelled oligosaccharides induced by photodissociation with visible light by Andrea Hahn; Jürgen Grotemeyer (503-507).
Photodissociation with visible light (Vis-PD) has been applied to chromophore labelled oligosaccharide ions produced by electrospray in a Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer. As chromophores four aromatic dyes, such as Rhodamine 110, have been attached to maltopentaose, lacto-N-fucopentaose I (LNFP I) and lacto-N-fucopentaose II (LNFP II). While in the positive ion mode the Vis-PD mass spectra show predominantly glycosidic cleavages and fragments from the reducing end of the carbohydrate, the negative ion spectra result in cross-ring cleavages and also glycosidic fragments mainly from the non-reducing end of the carbohydrate. It will be shown that Vis-PD mass spectrometry leads to sequence specific fragmentation.
Screening of fragrances in scented toys: a comparative study of different headspace techniques coupled to GC-MS by I. Masuck; C. Hutzler; A. Luch (508-515).
Fragrances capable of inducing contact allergy in skin potentially can be present in toys. These chemicals can migrate or emit from toys and can become available to children via oral ingestion, dermal contact or inhalation. For estimation of exposure of children to fragrances in scented toys time-consuming migration and inhalation testing is required. To distinguish between toys with and without fragrance allergens a sensitive screening method without complex sample preparation is needed. To pursue this goal, we have used headspace solid-phase microextraction (HS-SPME), dynamic headspace (DHS) and full evaporation DHS (FE-DHS), all coupled to GC-MS, to determine the released amounts of 24 fragrance allergens from scented toys. The compounds were quantified by calibration resulting in good linearity (r2 > 0.990). The limits of detection were up to 8800 ng ml−1 for HS-SPME sampling, up to 3710 ng ml−1 for DHS sampling and up to 19.2 ng ml−1 for FE-DHS sampling, respectively. All methods were subsequently applied to five real toys purchased from the market. Applying HS-SPME and DHS sampling we measured the released amounts in the range of nanograms per gram material. Conversely, applying FE-DHS sampling the released amounts were found in the range of micrograms per gram material. With DHS and FE-DHS we detected fragrances in the headspace which could not be analyzed by HS-SPME sampling and by a developed quantification method for fragrances in scented toys. Altogether, FE-DHS sampling was revealed as a sensitive screening method for the detection of fragrance allergens in scented toys.
Field evaluation of the Analyst® passive sampler for the determination of formaldehyde and acetaldehyde in indoor and outdoor ambient air by Florentina Villanueva; Inmaculada Colmenar; Rosanna Mabilia; Chiara Scipioni; Beatriz Cabañas (516-524).
The performance of the Analyst® passive sampler for the measurement of formaldehyde and acetaldehyde was assessed in a series of field experiments. It consists of a polyethylene cylinder filled with silica gel or a Florisil® adsorbent and a stainless steel or a silver anti-turbulence net which works as an ozone scrubber. Indoor and outdoor formaldehyde and acetaldehyde concentrations were measured in different locations (offices and rooms of a public building, a car, laboratories and private homes) of Ciudad Real (Spain) and Rome (Italy). In some cases, Radiello® passive samplers were used along with Analyst®, in order to compare and validate the results. The performance of the Analyst® device was also assessed by checking some parameters such as the diffusive sampling rate of acetaldehyde and the storage stability after collection and the self-consistency for both formaldehyde and acetaldehyde. From this work, it can be concluded that the Analyst® sampler is suitable for measuring formaldehyde and acetaldehyde in indoor and outdoor air.
Microwave-assisted acid digestion protocol for the determination of methionine and selenomethionine in selenium-enriched yeast by species specific isotope dilution GC-MS by Lu Yang; Paulette Maxwell; Zoltán Mester (525-529).
A quantitative and fast microwave assisted protein digestion method is described for the simultaneous determination of methionine (Met) and selenomethionine (SeMet) in yeast. Extraction of Met and SeMet from the selenized yeast was performed in a focused microwave system using methanesulfonic acid (MSA). The effects of parameters such as extraction time, temperature, power and sample mass on the extraction efficiencies of Met and SeMet were investigated. Species specific isotope dilution (ID) calibration using 13C enriched Met and SeMet spikes was employed to obtain accurate results. Analytes were derivatized with methyl chloroformate and extracted into chloroform prior to species specific ID GC-MS analysis. Using a 20 minute extraction time at 165 °C and 6 ml of 4 M MSA was found to be efficient for both analytes based on a 50 mg sample mass. Under these conditions, concentrations of 5862 ± 32 and 3366 ± 60 μg g−1 (one standard deviation, n = 3) for Met and SeMet, respectively, were obtained in SELM-1 yeast certified reference material (CRM). The obtained results are in good agreement with the certified values of 5758 ± 277 and 3448 ± 146 μg g−1 (expanded uncertainty, k = 2). Compared to previous MSA reflux digestion, this newly proposed method offers dramatic reduction in extraction time from 8–16 hours of the conventional MSA reflux to 20 minutes by microwave extraction, significantly improving the sample throughput. Additionally, the microwave extraction is fully automated and uses 75% less reagent (MSA) than the conventional acid reflux setup. The developed method is suitable for quasi real time production monitoring of Met and SeMet in Se enriched yeast and other food products.
Cloud point extraction for the determination of trace amounts of Pt(iv) by graphite furnace atomic absorption spectrometry by Wael I. Mortada; Mohammed M. Hassanien; Ahmed A. El-Asmy (530-535).
A cloud point extraction (CPE) system for the graphite furnace atomic absorption spectrometric (GFAAS) determination of Pt(iv) has been developed. The procedure is based on the complexation of Pt(iv) with 4-(p-chlorophenyl)-1-(pyridin-2-yl)thiosemicarbazide (HCPTS) in the presence of Triton X-114 as a non-ionic surfactant. The optimum conditions for the procedure were investigated with respect to several experimental parameters such as pH of the solution, Triton X-114 and HCPTS concentrations, incubation time and temperature, and centrifugation rate and time. Under the optimum experimental conditions, the calibration curve was linear up to 50 ng mL−1 with a detection limit of 0.25 ng mL−1 and the enrichment factor was 47. No considerable interference was observed due to the presence of coexisting anions and cations. The accuracy of the results was verified by analyzing the spiked water from different sources (tap, river, brackish, sea and industrial waste water). The proposed method has been applied for the determination of Pt(iv) in some real samples such as food and geological samples with satisfactory results.
Dispersive solid phase extraction coupled with HPLC-UV for simultaneous determination of chlorpyrifos and 3,5,6-trichloro-2-pyridinol in soil samples by Jianfei Xiong; Xiangyu Tang; Guangming Zhou; Zhuo Guan; Limin Wu (536-540).
A simple method was proposed for simultaneous determination of chlorpyrifos and its hydrolysis and biodegradation product 3,5,6-trichloro-2-pyridinol (TCP) in soil samples. The analytes were extracted with ethyl acetate (EtOAc) under optimized pretreatment conditions such as the type, volume and pH of extraction solvent. Clean-up of the extract from soil was conducted by dispersive solid phase extraction (DSPE) using activated carbon as the adsorbent. High performance liquid chromatography with ultraviolet detection (HPLC-UV) was used for simultaneous determination of the two analytes. Under the optimized HPLC conditions, the limits of detection (LOD), obtained on signal-to-noise ratio (S/N) of 3, for chlorpyrifos and TCP were 0.0080 mg kg−1 and 0.0120 mg kg−1, respectively. Linear calibration curves were obtained in the range of 0.05–2.00 mg kg−1 and 0.03–2.00 mg kg−1 for chlorpyrifos and TCP, respectively. The spike recoveries from soil ranged from 89.4% to 114%, and the relative standard deviation (RSD) was in the range of 0.80%–14%.
Validated stability indicating RP-HPLC method for determination of paracetamol, methocarbamol and their related substances by Eglal A. Abdelaleem; Nada S. Abdelwahab (541-545).
Paracetamol (PAR) and methocarbamol (MET) are co-formulated together in Methorelax® tablets which are widely used as a muscle relaxant and in the treatment of muscle-skeletal pain. On the other hand, 4-aminophenol (4-AP) and guaifenesine (GU) have been reported to be related substances and degradation products of PAR and MET, respectively. The target of this work was to develop and validate a simple, sensitive and selective stability indicating RP-HPLC method for the determination of PAR, MET, 4-AP and GU in their bulk powders and laboratory prepared mixtures. Chromatographic separation was achieved within 10 minutes with the required asymmetry, accuracy and precision on ODS column using 0.05 M KH2PO4 buffer : acetonitrile (72.5 : 27.5, v/v, pH = 6) as the mobile phase at a flow rate of 1 mL min−1 with UV detection at 225 nm. The developed method has been validated as per ICH guidelines and the calibration plots were linear over the concentration ranges of 3–20, 4–25, 0.6–8 and 0.6–8 μg mL−1 for PAR, MET, 4-AP and GU, respectively. The method has been successfully applied in the analysis of Methorelax® tablets and good results were obtained. Moreover, its results have been compared to a previously reported RP-HPLC method and no significant difference was found between the two methods.
An improved method for the discrimination of oils and fats by Thalia Dourtoglou; Vassilis Dourtoglou; Vassiliki Diamadopoulou; Stavros Lalas (546-553).
An improved method for the discrimination of oils and fats is being proposed. The method is based on the principal component analysis and discrimination analysis of the results obtained by determination of the mole percentage of total fatty acids (fatty acid methyl esters analysis by GC) and regiospecific distribution of the same fatty acids in positions 1 and 3 of triglycerides (using a regiospecific lipase and analysis by GC of the produced butyl esters). Various samples (pure olive oils, various seed oils, mixtures of pure olive oils with seed oils, commercially available foods containing animal fats and/or vegetable oils and, finally, local pure olive oils from different areas of Greece) were subjected to two transesterification treatments. It was proved that the proposed method has a global discriminating ability of identifying (at a level of 5%) olive oil adulteration with various seed oils, discriminating animal fats from vegetable oils and animal fat adulteration with seed oils and, finally, discriminating olive oils on the basis of their geographical origin, in a small area like south Greece. Additionally, the introduced method includes a complete database (as a demonstration tool, mainly for olive oil) in order to be used by any concerned laboratory.
Application of microwave digestion and ICP-MS to simultaneous analysis of major and trace elements in aerosol samples collected on quartz filters by J. Aldabe; C. Santamaría; D. Elustondo; E. Lasheras; J. M. Santamaría (554-559).
A microwave digestion method in a closed vessel was developed for the simultaneous determination of trace and major elements, with the highest possible recoveries, in atmospheric aerosols using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). This method was developed to quantify the concentration of Na, Mg, Al, P, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Cd, Sb, Cs, Ba, La, Ce and Pb present in quartz filters containing particulate matter (PM10). The performance of the procedure was evaluated by analysis of the standard reference material NIST 1633b and CTA-FFA-1. Different combinations of nitric acid (HNO3), hydrogen peroxide (H2O2), hydrofluoric acid (HF) and hydrochloric acid (HCl) were tested to improve the recovery factors for the studied elements. The addition of a large amount (3 mL) of HF was required to fully dissolve the quartz filters. This fact made difficult the obtention of high recoveries for alkali (Rb, Cs), alkaline earth (Mg, Ca, Ba), and rare earth (La, Ce) elements, which showed the lowest recoveries. In this study three different digestion methods were assessed using a closed evaporation system, the addition of boric acid and a mixture of both procedures to minimize the effects of residual fluoride.
Colorimetric determination of hexavalent chromium with ascorbic acid capped silver nanoparticles by Xiaoyan Wu; Yunbo Xu; Yangjun Dong; Xue Jiang; Ningning Zhu (560-565).
A simple and sensitive colorimetric detection method for hexavalent chromium (Cr(vi)) was described based on ascorbic acid (AA)-capped silver nanoparticles (AgNPs). The cross-linking between AA and Cr(iii), the reductive product of Cr(vi), resulted in the aggregation of AA-capped AgNPs, and the color change from yellow to red. Control experiments with the addition of over 15 other metal ions (Cr3+, Pb2+, Zn2+, Hg2+, Cd2+, Co2+, Cu2+, Al3+, Ni2+, Ag+, Mn2+, Ba2+, Fe3+, Na+, K+, Ca2+, Mg2+) did not result in a distinct change in the color or in the spectrum of the suspension, indicating that these ions do not interfere with the colorimetric determination of Cr(vi). The detection concentration of Cr(vi) ranged from 7.0 × 10−8 to 1.84 × 10−6 M, and the detection limit was 5 × 10−8 M (3δ). The performance of the sensor was successfully evaluated with water samples spiked with Cr(vi), indicating that this convenient and sensitive technique offers great promise for onsite environmental monitoring of Cr(vi).
Back matter (566-566).
Back cover (567-568).