Final Determination Step Research Articles

Development of a vortex-assisted switchable-hydrophilicity solvent-based liquid phase microextraction for fast and reliable extraction of Zn (II), Fe (II), Pb (II), and Cd (II) from various baby food products

This manuscript describes the development of a novel liquid phase microextraction (LPME) method for the extraction and determination of Zn (II), Fe (II), Pb (II), and Cd (II) in various infant/baby food and supplements products. The method is based on vortex-assisted extraction combined with a switchable-hydrophilicity solvent (SHS) sample preparation. The SHS, which undergoes reversible phase changes triggered by pH change, enables selective extraction and easy phase separation. A flame atomic absorption spectroscopy was used in the final determination step. Optimization studies revealed, that the optimal pH of the sample solution (after digestion) during analytes extraction is 5.5. A l-proline is added to the sample (375 mM) to ensure the complexation of the target metal cations. After the complexation step, 750 µL of SHS - a N, N-Dimethylcyclohexylamine along with 0.9 mL of 2 M of acetic acid solution is added (hydrophilicity switch-on stage) and mixed manually to obtain a homogeneous solution. In the last stage, 0.45 mL of 10 M NaOH solution (hydrophilicity switch-off stage) is added to the sample solution and a vortex for 100 s is applied to ensure the effective extraction and separation of the complex containing the analytes. At this stage, a cloudy solution is immediately obtained. Finally, the effective phase separation is obtained at the centrifugation step (4000 rpm for 2 mins). The method limit of detection was as 0.03, 0.009, 0.6, and 0.2 ng/L for Zn (II), Fe (II), Cd (II), and Pb (II) respectively with RSD% below 2.0 %. The analysis of certified reference materials and real samples proved the full applicability of the method for routine analysis, contributing to the field of heavy metal analysis and ensuring the safety of baby products. According to the AGREE methodology, this method can be named as green analytical chemistry method with a score of 0.77.

Synthesis, characterization and application of cross-linked functional terpolymer through epoxy group as sorbent for extraction of cadmium from waters and foods: Multivariate optimization

The purpose of this study was to develop a selective sorbent for cadmium ions (Cd(II)) enrichment in orbital shaker assisted solid phase microextraction (OS-SPME) from different aqueous and food samples. A maleic anhydride-styrene-glycidyl methacrylate (MA-St-GMA) terpolymer was synthesized and characterized in detail. Experimental variables of sample preparation step were optimized using a central composite design (CCD). The final determination step was performed using flame atomic absorption spectroscopy (FAAS). The MA-St-GMA sorbent exhibited a high adsorption capacity (195.9 mg g−1) for the Cd(II) ion. The developed method under optimal conditions provides satisfactory performance and a significant improvement compared to other protocols available in the literature. The linear range and detection limit of the method is 0.1–130 ng mL−1 and 0.03 ng mL−1, respectively. The robustness, intraday/interday precision, selectivity, and accuracy of the method were investigated. To further validate the method, a dedicated series of analysis was performed using certified reference materials (CRMs). This part of the study confirmed the applicability of the method for routine analysis. The OS-SPME-FAAS method was validated using water and food samples. Relative standard deviations and recovery for real-world samples were in ranges 1.7–2.2 % and 95.5–98.5 %, respectively. As a result, the MA-St-GMA sorbent showed that it could quantitatively extract Cd(II) ions from aqueous solution.

Evaluating the Relationship Between Performance on a Multiple-Choice Examination and Common ABA-Based Procedures

To ensure the quality of training, skills developed and maintained, and expected standards for behavior analysts, several systems have been put into place across the years. Of these systems, perhaps the most widespread was the development of the Behavior Analyst Certification Board in 1998. Once all requirements are met, the final determinative step in obtaining certification is a multiple-choice examination. The use of a multiple-choice examination as the final determinative step in obtaining behavior analytic certification may create some concerns for behavior analysts. Identification of a positive correlation between the multiple-choice examination and performance may help ameliorate these concerns. The purpose of this study was to evaluate any potential correlations between scores on a popular commercially available prep examination and basic applied behavior analysis (ABA)–based autism intervention procedures with 25 professionals. Overall, the results indicated that multiple-choice examination scores were not significantly correlated with any assessments of performance.

Development and validation of a multi-pollutant method for the analysis of polycyclic aromatic hydrocarbons, synthetic musk compounds and plasticizers in atmospheric particulate matter (PM2.5)

Exposure to atmospheric particulate matter (PM) associated pollutants is a global concern due to the risk posed in human health after inhalation. In this study, a simple and sensitive multi-residue method is developed for the analysis of 50 organic pollutants, comprising 18 polycyclic aromatic hydrocarbons (PAHs), 12 phthalate esters (PAEs), 12 organophosphorus flame retardants (OPFRs), 6 synthetic musk compounds (SMCs) and 2 bisphenols in PM2.5 samples. The method consists of three cycles of ultrasonic assisted solvent extraction and vortex (UASE + vortex), followed by a vortex-assisted dispersive solid phase extraction (d-SPE) clean-up and a final determination step by using programmed temperature vaporization-gas chromatography-tandem mass spectrometry (PTV-GC-MS/MS). Experimental conditions concerning clean-up adsorbents (alumina, silica gel and Florisil®) and filters (glass fibre, PTFE and nylon), as well as PTV-GC-MS/MS conditions were studied. In addition, the use of SRM (selected reaction monitoring) mode in MS-MS, as well as matrix-matched calibration together with labelled subrogate standards, resulted in successfully validation results for most of the compounds due to the high sensitivity, minimization of matrix effects and recovering losses compensation. The proposed method was validated in terms of linearity, limits of detection and quantification (LODs and LOQs), analytical recoveries by analysing a spiked composite sample (PM2.5) at three spiking levels and intra-day and inter-day precision. Moreover, an urban particulate matter standard reference material (SRM 1648a) was analysed to assess PAHs determination accuracy. Furthermore, applicability of the method was proved by analysing 12 PM2.5 samples from an industrial area. Among all studied pollutants, bisphenol A (BPA) was the most predominant with an average concentration of 5000 pg m−3, followed by bis(2-ethylhexyl) phthalate (DEHP) and diisobutyl phthtalate (DiBP) with 1990 pg m−3 and 632 pg m-3, respectively. Concerning OPFRs, average concentrations between 345 – 253 pg m−3 were found for triphenyl phosphine oxide (TPPO), tris(chloropropyl) phosphate (TCPP), tri-iso-butyl phosphate (TiBP) and tris(2-butoxyethyl) phosphate (TBOEP). Finally, the highest PAHs levels were found for 5-6 ring-number PAHs (Σ5-6 rings PAHs) with an average concentration of 2680 pg m−3, while only 2 SMCs were quantitated accounting for 17.5 pg m−3 by average.

An advanced workflow for single-particle imaging with the limited data at an X-ray free-electron laser.

An improved analysis for single-particle imaging (SPI) experiments, using the limited data, is presented here. Results are based on a study of bacteriophage PR772 performed at the Atomic, Molecular and Optical Science instrument at the Linac Coherent Light Source as part of the SPI initiative. Existing methods were modified to cope with the shortcomings of the experimental data: inaccessibility of information from half of the detector and a small fraction of single hits. The general SPI analysis workflow was upgraded with the expectation-maximization based classification of diffraction patterns and mode decomposition on the final virus-structure determination step. The presented processing pipeline allowed us to determine the 3D structure of bacteriophage PR772 without symmetry constraints with a spatial resolution of 6.9 nm. The obtained resolution was limited by the scattering intensity during the experiment and the relatively small number of single hits.

A review of available analytical technologies for qualitative and quantitative determination of nitramines.

This review aims to summarize the available analytical methods in the open literature for the determination of some aliphatic and cyclic nitramines. Nitramines covered in this review are the ones that can be formed from the use of amines in post-combustion CO2 capture (PCC) plants and end up in the environment. Since the literature is quite scarce regarding the determination of nitramines in aqueous and soil samples, methods for determination of nitramines in other matrices have also been included. Since the nitramines are found in complex matrices and/or in very low concentration, an extraction step is often necessary before their determination. Liquid-liquid extraction (LLE) using dichloromethane and solid phase extraction (SPE) with an activated carbon based material have been the two most common extraction methods. Gas chromatography (GC) or reversed phase liquid chromatography (RPLC) has been used often combined with mass spectrometry (MS) in the final determination step. Presently there is no comprehensive method available that can be used for determination of all nitramines included in this review. The lowest concentration limit of quantification (cLOQ) is in the ng L(-1) range, however, most methods appear to have a cLOQ in the μg L(-1) range, if the cLOQ has been given.

Determination of Surfactants in Environmental Samples. Part III. Non-Ionic Compounds

Abstract Non-ionic surface active agents are a diverse group of chemicals which have an uncharged polar head and a non-polar tail. They have different properties due to amphiphilic structure of their molecules. Commercial available non-ionic surfactants consist of the broadest spectrum of compounds in comparison with other types of such agents. Typically, non-ionic compounds found applications in households and industry during formulation of cleaning products, cosmetics, paints, preservative coatings, resins, textiles, pulp and paper, petroleum products or pesticides. Their are one of the most common use class of surfactants which can be potential pollution sources of the different compartment of environment (because of they widely application or discharging treated wastewaters to surface water and sludge in agricultural). It is important to investigate the behavior, environmental fate of non-ionic surfactants and their impact on living organisms (they are toxic and/or can disrupt endocrine functions). To solve such problems should be applied appropriated analytical tools. Sample preparation step is one of the most critical part of analytical procedures in determination of different compounds in environmental matrices. Traditional extraction techniques (LLE - for liquid samples; SLE - for solid samples) are time and solvent-consuming. Developments in this field result in improving isolation efficiency and decreasing solvent consumption (eg SPE and SPME - liquid samples or PLE, SFE and MAE - solid samples). At final determination step can be applied spectrophotometric technique, potentiometric titrametration or tensammetry (determination total concentration of non-ionic surfactants) or chromatographic techniques coupled with appropriated detection techniques (individual analytes). The literature data concerning the concentrations of non-ionic surfactants in the different compartments of the environment can give general view that various ecosystems are polluted by those compounds.

Determination of Surfactants in Environmental Samples. Part I. Cationic Compounds / Oznaczanie Surfaktantów W Próbkach Środowiskowych. Część I. Związki Kationowe

Abstract Compounds from the group of cationic surfactants are widely applied in household, industrial, cleaning, disinfectant, cosmetic and pharmaceutical products as their specific properties (antimicrobial, emulsifying, anticorrosion, softening). After use, cationic surfactants are disposed to wastewater-treatment plants and finally with effluent water to surface waters due to their incomplete degradation. Moreover, they can freely circulate in different environmental compartments including living organisms. It becomes indispensable to recognize in more detail behavior, fate and biological effects of cationic surfactants. This analytical problem can be solved with use sensitive and reliable analytical techniques at sample preparation step and final determination step. In recent years, during isolation analytes from environmental samples mainly were used liquid-liquid extraction (LLE) - liquid matrices or solid-liquid extraction (SLE) - solid matrices. This technique involves application of toxic solvents (chloroform), is time-consuming and interferences are co-extracted. Nowadays, in scientific centers are carried out research to replace this traditional technique. So far, the following techniques were applied: solid-phase extraction (SPE) or it modification (HF-LPME) - liquid samples; accelerated solvent extraction (ASE) and supercritical fluid extraction (SFE) - solid samples. During the determination of total content of cationic surface active agents in environmental samples were used a traditional spectrophotometry technique and potentiometric titration technique. But those techniques are susceptible of interferences on analysis results (anionic and non-ionic compounds). The chromatographic technique (liquid chromatography) applied at the final determination step gives possibility to determine individual cationic surfactants in solvent extracts of environmental samples. The LC systems coupled with mass spectrometers are most powerful tools during such analysis.

Monitoring and analytics of semivolatile organic compounds (SVOCs) in indoor air

This paper reviews literature information on the behaviour of semivolatile organic compounds (SVOCs) in the indoor environment, as well as the most likely emission sources. The consecutive stages of analytical procedures used for monitoring SVOCs in indoor environments are described. The most common approaches used for collecting samples from the gas and particulate phases are mentioned. The paper discusses and compares various types of sorbents and filters applied in dynamic, passive and denudational techniques, as well as the techniques used to liberate the SVOCs, including Soxhlet, sonication and microwave extraction. The main advantages and disadvantages of each technique are discussed, together with possible future trends. The approaches commonly used during the final determination step, such as gas chromatography and liquid chromatography, are presented together with their possible drawbacks, and ways of eliminating them are suggested. The review makes brief reference to the effects of human exposure to SVOCs in house dust and discusses the main aspects of the analytical procedures used to monitor the presence of SVOCs in this medium.

Pesticide Analysis of Bee and Bee Product Samples

Bee products possess therapeutic properties and are the source of many essential trace elements, which is why they are regarded as valuable food products. Honey bees may bring to the hive numerous contaminants deposited on the plants they visit, including pesticide without xenobiotics. The large-scale application of pesticides in agriculture and horticulture can lead to mass mortality among bees, and the chemicals find their way into bee products. The presence of xenobiotics in these products can lower their quality and cause their properties to deteriorate, which in consequence may endanger human health. All this means that the analysis of bees, honey and other bee products is becoming a matter of increasing urgency. In this context new analytical methodologies are needed, enabling a wide spectrum of analytes to be assayed in a single sample and during one analytical run. Attention is focused on new techniques of sample preparation and extract cleanup prior to the final determination step. Besides characterizing the honey bee and bee products, the article analyzes the literature data on the latest methodological developments for determining levels of a wide range of pesticides.

Biological Fluids as a Source of Information on the Exposure of Man to Environmental Chemical Agents

The human body is exposed to a variety of environmental pollutants. Many chemical compounds, including volatile organochlorine compounds and metals, have a harmful effect on the tissues and organs of the human body, in many cases causing irreversible damage and illnesses. In order to assess the degree of occupational hazard, it has become more and more common to determine the concentrations of chemical substances or their metabolites in biological fluids (i.e., in urine, blood, or less often, in human milk, bile, saliva, and sperm). However, in order to determine concentrations levels of trace components in biological fluids such as urine, blood, milk, bile, saliva, or sperm, the samples collected have to be prepared for the final analysis because their matrix is so complex as to preclude direct determination of the analytes by any analytical method available. This article contains the literature data on: analyte isolation and/or enrichment techniques from samples of biological fluids prior to the final determination step; and final determination techniques for a variety of compounds, both organic and inorganic, being determined in the above samples. The data include both the primary pollutants that found their way into the human body as a result of environmental and occupational exposure and the products of their conversion (metabolism) in the organism.

Comparison of two clean-up principles for determination of trichothecenes in grain extract

Two clean-up principles for the multi-determination of seven trichothecene toxins, deoxynivalenol, nivalenol, diacetoxyscirpenol, fusarenon-X, T-2 tetraol, HT-2 toxin and T-2 toxin in wheat extract are described. For clean-up of acetonitrile–water (84:16, v/v) extract either gel permeation chromatography (Bio-Beads S-X3 gel) or solid-phase extraction (combination of Florisil and C 18-silica gel SPE cartridges or a Romer Labs. MycoSep 225 column) were used. The MycoSep 225 column was chosen as the best alternative for clean-up of grain samples. Recovery of this procedure was tested on certified material. Derivatisation of analytes prior to the final determinative step was carried out by trifluoroacetic acid anhydride. Trifluoroacyl derivatives of the trichothecenes were separated by high-resolution capillary gas chromatography with electron-capture detection.

A Study on the Possibility of Using HPLC for the Determination of 2,4-D in Tomatoes

Abstract An HPLC method for the determination of 2,4-D in tomatoes has been studied. Tomato samples were extracted with acetone-dichloromethane (2:1) after hydrolysis. The extract was cleaned up with acid-base partition and furthermore eluting through XAD-2 column. Then, it was analyzed using reverse phase HPLC. Four different mobile phase mixtures, at two different flow rates of 1.0 and 1.5 mL/min, were tried, to choose the best conditions in the final HPLC determination step. The best results were obtained using the mixture of acetonitrile:water, containing 2% of acetic acid (50:50, v/v), at a flow rate of 1.0 mL/min for the separation of 2,4-D standard solutions, but the baseline separation of 2,4-D in the final solution of sample extract could not be achieved due to interferences causing poor resolution as well as low recovery.

Solvent-Efficient Thin-Layer Chromatographic Method for the Determination of Aflatoxins B1, B2, G1, and G2 in Corn and Peanut Products: Collaborative Study

An interlaboratory study of a solvent-efficient thin-layer chromatographic (TLC) method for the determination of aflatoxins B1, B2, G1, and G2 was conducted in laboratories located in the United States, France, Tunisia, and Denmark. Eighteen artificially contaminated samples plus blanks of raw peanuts and peanut butter and corn containing varying amounts of aflatoxins B1, B2, G1, and G2 were distributed to participating laboratories. The method consists of elements of the U.S. Food and Drug Administration (FDA), Contaminants Branch (CB) (AOAC Method 968.22) and FDA, Best Foods (BF) (AOAC Method 970.45) methods with reduced requirements for solvents. Participating laboratories used either visual or densitometric techniques during the final determinative step. Statistical analysis of the data was performed to determine or confirm outliers and to compute repeatability and reproducibility of the method using either visual or densitometric techniques for the determinative step. Reported results from laboratories using a densitometer showed that, for corn, the relative standard deviation for repeatability (RSDr) for aflatoxin B1 ranged from 56.6 to 41.7% for contamination levels ranging from 5 to 50 ng/g. For raw peanuts and peanut butter, the RSDr values for aflatoxin B1 ranged from 21.3 to 37.3% and 65.9 to 42.1%, respectively, for the contamination levels ranging from 5 to 25 ng/g. RSDr ranges for aflatoxins B2, G1, and G2 were similar. For reproducibility (R), the RSDR ranges for aflatoxin B1 were 41.7-56.6%, 56.6-84.8%, and 26.4-37.3% for corn, peanut butter, and raw peanuts, respectively. Average recoveries for all aflatoxins at all levels were 95.3, 139.0, and 95.6% for corn, peanut butter, and raw peanuts, respectively. When analysts determined aflatoxin concentrations in corn by visual comparison to standards, the RSDr values for aflatoxin B1 were 47.8-11.4% for contamination levels ranging from 5 to 50 ng/g. For raw peanuts and peanut butter, the RSDr values for aflatoxin B1 were 76.3-12.6% and 33.4-8.8%, respectively, for the contamination levels ranging from 5 to 25 ng/g. RSDr values for aflatoxins B2, G1, and G2 were similar. The RSDR values for aflatoxin B1 were 34.6-90.2%, 45.5-59.3%, and 31.8-78.3% for corn, peanut butter, and raw peanuts, respectively. Average recoveries for all aflatoxins at all levels were 111.0, 157.6, and 92.3% for corn, peanut butter, and raw peanuts, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

A review of sulphites in foods: Analytical methodology and reported findings

Sulphites in various forms have been added to foods for centuries. Their use became an issue of concern when certain sensitive individuals exhibited adverse reactions to sulphite residues in foods. Analytical methods were developed to monitor these compounds at the regulatory limit of 10 ppm. In this report, analytical methods for determining sulphites in foods are reviewed, along with a critique of their chemistry and procedural schemes. An assessment of the key features of each method category is presented together with some comparative data. The classification scheme used is based upon the fact that determination of the sulphite content of a food is influenced more by the treatment and cleanup of the test solution than by the final determinative step. Based on a 60-year database, the Monier-Williams procedure still remains the method of choice.

High-performance liquid chromatographic determination of the myucotoxins patulin, penicillic acid, zearalenone and stegimatocystin in artificially contaminated cocoa beans

A high-performance liquid chromatographic (HPLC) method has been developed to allow the determination of patulin, penicillic acid, sterigmatocystin and zearalenone in samples of cocoa beans. When this method is combined with a method that was reported earlier for the determination of ochratoxin A[W.J. Hurst and R. A. Martin, Jr., J. Chromatogr., 265 (1983) 353], it allows for the determination of five mycotoxins. Samples were extracted with an acidic acetonitrile solution, partitioned with hexane to remove fat interferences and the partitioned with chloroform to remove the toxin containing fraction. Interferences were removed by the use of a bonded phase column followed by the final HPLC determination step, which uses a cyano column with a hexane—1-propanol—acetic acid mobile phase with dual chanel UV detection at 245 adn 280 nm. The method exhibits good linearity, accuracy and precision.

Accurate determination of the noble metals II. Determination methods

As was shown in the first part of this contribution, accurate analytical determination of the noble metals in rocks, ores and alloys needs a sophisticated sample pretreatment prior to the final determination step of the preconcentrated elements. For this many instrumental and classical methods are available, the choice of which is usually dictated by levels of precious metal to be handled, nature of sample matrix and availability of the instruments. For trace levels (μg/g range) flame atomic absorption and inductively coupled plasma (ICP) emission spectrometry can be used. ICP emission is favoured because of ease of multi-element operation. At the sub-μg/g level furnace atomic absorption and nuclear techniques (mainly neutron activation) are favoured. Minor and % concentrations are best handled by X-ray fluorescence. The use of standard reference samples and internal and external laboratory control schemes are essential to the accurate determination of precious metals.

Development of a sensitive high-performance liquid chromatographic method for detection of aflatoxins in pistachio nuts

A very sensitive method is described for the detection of aflatoxins in pistachio nuts. The method employs the extraction procedure used in the BF method (described in the Association of Official Analytical Chemist' Book of Methods) followed by an acid alumina column clean-up to remove sample components which would otherwise interfere in the final determinative step. The quantitation of the afiatoxins is carried out by high-performance liquid chromatography on a C 18 reversed-phase column after conversion of aflatoxins B 1 and G 1 to their more fluorescent derivatives, B 2a and G 2a. The limit of detection was found to be 0.5 μ/kg. The chromatograms were found to be free of interfering peaks and multiple injections showed excellent reproducibility.

Spectrophotometric estimation of sennosides and rhein glycosides in senna and its preparations.

A spectrophotometric method is presented for assaying Senna and its preparations, for both total sennosides and total rhein glycosides content. The method ensures complete elimination of other minor non-carboxylic anthracene derivatives, as well as flavonoidal contaminants. The proposed method quantitates the actual total sennosides content, through the elimination of these contaminants, and through correction for the interference due to the coexistence of rhein with sennidins, in the final determinative step. This would eliminate false high figures for total sennosides by earlier procedures and reflects, perspectively, the actual potency of the assayed samples.

Separation and Ultraviolet Absorbance Techniques for Determining Dihydrotachysterol in Pharmaceutical Preparations

Three separation techniques and ultraviolet (UV) spectrophotometry are described for dihydrotachysterol (DHT). The absorbance procedure eliminates the necessity of establishing a regular baseline, which is advantageous in certain cases. The relative absorbance values obey Beer's law in the range of 1-10 mug DHT/ml ethanol. An absorbance ratio check ensures the applicability of the method with respect to the degree of allowable interference present. The absorbance ratio values at the indicated wave-lengths at this concentration range and in the absence of any interferences are relativiely constant. The UV absorbance could serve as the common final determinative step for the other techniques, either singly or in combination, for quantitating DHT in preparations that require varying degrees of cleanup through extraction, saponification, and thin layer chromatography. The respective mean per cent recoveries and their relative standard deviations for a 50 mug DHT standard sample treated by the 3 techniques are 99.6 -+/ 0.5, 98.5 -+/ 1.1, and 97.3 -+/ 3.3%. Content uniformity determination of DHT in tablets and in soft gelatin capsules is also presented, and precautions are discussed.