Assessment of total arsenic and arsenic species stability in alga samples and their aqueous extracts

In order to achieve reliable information on speciation analysis, it is necessary to assess previously the species stability in the sample to analyse. Furthermore, in those cases where the sample treatment for species extraction is time-consuming, an assessment of the species integrity in the extracts is of paramount importance. Thus, the present paper reports total arsenic and arsenic species stability in alga samples (Sargassum fulvellum and Hizikia fusiformis), as well as in their aqueous extracts, which were stored in amber glass and polystyrene containers at different temperatures. Total arsenic determination was carried out by inductively coupled plasma atomic emission spectroscopy (ICP-AES), after sample acid digestion in a microwave oven, while arsenic speciation was conducted by anion exchange high performance liquid chromatography on-line coupled to ICP-AES, with and without sample introduction by hydride generation (HPLC-ICP-AES and HPLC-HG-ICP-AES), after aqueous microwave-assisted extraction. The results obtained for solid alga samples showed that total arsenic (for Hijiki alga) and arsenic species present (As(V) for Hijiki and NIES No. 9 Sargasso) are stable for at least 12 months when samples are stored in polystyrene containers at +20 degrees C. On the other hand, a different behaviour was observed in the stability of total arsenic and As(V) species in aqueous extracts for both samples, being the best storage conditions for Sargasso extracts a temperature of -18 degrees C and polystyrene containers, under which they are stable for at least 15 days, while Hijiki extracts must be stored in polystyrene containers at +4 degrees C in order to ensure the stability for 10 days.     

Systematic Errors in the Determination of Trace Metals by GFAAS Technique,Part I

The behaviour of solutions containing 7 metals in trace range (pH=2) prepared in borosilicate glass and polyethylene containers and transferred into commercial polyethylene–polypropylene and home-made quartz autosampler cups for measurements were studied using graphite furnace atomic absorption spectrometry. The different interactions between metal solution and vessel material were observed for the metals studied. The most significant losses of chromium and nickel occurred on a polyethylene surface, while the highest absorbance signals were registered from quartz containers. Higher absorbance signals from quartz containers were also obtained for cadmium and copper solutions. Contrary to these results, the absorbance signals for lead solutions were lowest when measured from quartz vessels. The container material had no influence on the analytical signals of cobalt and manganese.Received January 15, 2003; accepted April 15, 2003 published online August 22, 2003     

Losses of silver,arsenic, cadmium,selenium and zinc traces from distilled water and artificial sea-water by sorption on various container surfaces

Sorption losses were studied for Ag. As, Cd, Se, and Zn at a concentration level of 10^-7 M from distilled water and artificial sea-water during storage in containers made of borosilicate glass, high-pressure polyethylene, or polytetrafluoroetbylene. Apart from pH (1, 2, 4, and 8.5) and storage time (1 min to 28 days), special attention was paid to the effect of the ratio of inner container surface to sample volume. The results are compared with literature data. In addition, a survey is given of literature references on sorption of 41 elements from aqueous solutions under different experimental conditions.     

The rate of loss of mercury from aqueous solution when stored in various containers

Solutions of natural water and distilled water were spiked with mercury(II) (25 p.p.b.) and stored in polyethylene, polyvinyl chloride, and soft glass containers. Losses of mercury at different pH values were monitored by flameless atomic absorption for a total of 17 days. Severe losses of mercury were observed at pH 2 and 7. Mercury loss from solution followed first-order kinetics; the half-lives of mercury loss under various conditions were calculated. Acidification of the solutions to pH 0.5 with nitric acid curtailed mercury loss substantially. Possible ways of reducing the loss of mercury from environmental water samples are discussed.     

A container adsorption study of cadmium using109Cd spiking and liquid scintillation counting

¹⁰⁹Cd may be used as a radiolabel in tracer studies of Cd(II) because of the ease and efficiency with which it may be counted by liquid scintillation counting. It has been found that ppm solutions of Cd²⁺, spiked with¹⁰⁹Cd, may be stored for at least 200 d, in either amber glass or polypropylene containers, without measurable container adsorption, at pH's of 5 or less. At pH's above 5, there is some evidence of container adsorption, particularly in the case of polypropylene containers. Amber glass is recommended if pH's between 5 and 7 must be used for storage.     

Increased mercury contamination of distilled and natural water samples caused by oxidizing preservatives

The passage of mercury vapor from ambient air through the walls of conventional polyethylene (CPE), linear polyethylene (LPE), and Teflon (FEP) containers can seriously contaminate solutions of distilled and natural water stored in these containers. The rate of mercury contamination is dramatically increased when the sample solution contains oxidizing agents such as nitric acid or potassium permanganate, which are commonly used as preservatives to prevent loss of mercury(II) ion. The rate of contamination also depends on container material and decreases in the order CPE> LPE> FEP> glass. Freezing the samples in plastic containers is an effective way to prevent mercury contamination. When freezing is not practical, storage in glass containers minimizes sample contamination from ambient mercury vapor.     

Investigation by automated differential pulse anodic-stripping voltammetry of the problem of storage of dilute solutions

The storage of dilute solutions of metal ions before their laboratory analysis presents a difficult problem in the examination of many environmental samples. By utilizing the solution container as an electrochemical cell and employing the method of differential pulse anodic-stripping voltammetry at a hanging mercury drop electrode, it is shown that an automated read-out system in an enclosed environment can be developed for monitoring the solution-container interactions that occur over short or extended periods of time. In the present work, interactions of dilute solutions (1-10 mug/l.) of cadmium(II), lead(II), copper(II), zinc(II), and thallium(I) in glass, polyethylene and Teflon containers have been investigated at various pH values and in different ionic environments. The results demonstrate the importance of factors other than pH.     

Comparison of dry and wet ashing procedures for cadmium and iron determination in biological material by atomic-absorption spectrophotometry

A possible loss of cadmium and iron from the sample during dry ashing of the kidney, liver or carcase was examined by the radioactive isotope labelling technique. Cadmium-115 m or iron-59 was administered to rats 4-7 days before the rats were killed and samples collected. Dry ashing in different types of dishes and wet digestion with nitric acid were compared. There was no loss of cadmium or iron by volatilization during dry ashing at 600 degrees or 450 degrees respectively, but a significant amount of iron was bound on glass or porcelain crucibles. Storage of ashed and dissolved samples (in 10 nitric acid) did not show any change of cadmium or iron concentration up to 9 days.     

A study of adsorption characteristics of traces of chromium(III) and (VI) on selected surfaces

The adsorption losses of chromium(III) or (VI) on the walls of Pyrex, flint glass and polyethylene beakers have been investigated. Chromium(III) or (VI) solutions were stored in beakers at different hydrogen ion concentrations, and losses due to adsorption were measured at various contact times by counting the γ-ray activity from chromium-51 radiotracer. At pH 6.95, chromium(III) solutions showed the greatest instability, particularly in polyethylene beakers, where losses up to 25% were observed at the end of the 15-day contact period. Chromium(VI) showed a completely different pattern; losses less than 1% were observed at the end of 15 days on all the three types of containers.     

Tensammetry with accumulation on the hanging mercury drop electrode: Part 6. Errors of determination caused by adsorption of non-ionic surfactants on the material of the measuring cell

The adosorptive loss of oxyethylated alkylphenols (Triton X-100 and Rokafenol N-3), oxyethylated alcohols (Brij-35, Marlipal 1618/40 and surfactant 18-10) and poly(ethylene glycol) of MW 9000 on cells constructed from quartz, glass, glassy carbon, PTFE, polyethylene, polypropylene, polystyrene and aluminium during the measuring process was investigated. In all instances very substantial losses were found, which completely changed the results of the determination. Apart from the vessel itself, very important losses on the ceramic frit located at the end of the salt bridge were found.The loss of all the surfactants tested on the quartz vessel is not very substantial and, after protection of the ceramic frit, a cell with such a construction gives minimum losses. The glass cell is very sensitivie to the manner of preparation of its surface. Cells constructed from PTFE and glassy carbon adsorb more specifically than others and can be used for the determination of oxyethylated alcohols but not for the determination of oxyethylated alkylphenols. Other materials used gave substantial losses of almost all the surfactants tested. Particularly bad results were obtained with polystyrene and aluminium cells.     

Adsorption characteristics of traces of silver on selected surfaces

A study of materials used for the storage of dilute aqueous solutions of silver established the adsorption characteristics of Teflon, Vycor, polypropylene, polystyrene and coatings of paraffin, acrylic spray, and Tygon paint. None of these materials or coatings was found satisfactory for prolonged storage of water samples containing trace quantities of silver. As in an earlier study, it was necessary to complex the silver in the sample with sufficient sodium thiosulfate to insure less than 1 % adsorption to containers over a 30-day contact period.     

Effect of alkali and ultraviolet aging on physical,thermal, and mechanical properties of fibers for potential use as reinforcing elements in glass/silicate composites

This work reports the effect of an alkaline environment and ultraviolet (UV) radiation on the physical, thermal, and tensile properties of different fibers selected as potential reinforcing elements to enhance the impact properties of brittle glass/silicate composites. The fibers, which included regenerated cellulosic (viscose and rayon), synthetic (ultrahigh molecular weight polyethylene, polypropylene, polyamide, acrylic), glass, ceramic, and steel, were aged in different alkaline solutions with pH ranging from 11.1 to 13.6 at 70°C for different periods of time and exposed to UV radiation for 330 h. The physical and thermal properties of aged fibers were studied using tensile testing, scanning electron microscopy, and simultaneous differential and thermogravimetric analysis. Results showed that the regenerated cellulosic fibers, acrylic, E‐glass, and A‐glass fibers could not withstand the highly alkaline environment. Overall, ultrahigh molecular weight polyethylene, UV‐stable polypropylene, polyamide 6.6, AR‐glass, ceramic (alumino borosilicate), and steel fibers performed very well under all conditions, indicating that they have the potential to be used as reinforcing elements in glass/silicate composites. Copyright © 2011 John Wiley & Sons, Ltd.     

Chemical stability of midazolam injection by high performance liquid chromatography

The chemical stability of midazolam hydrochloride injection, undiluted or diluted with dextrose sterile solution, was studied at different storage conditions by LC. The study was performed at room temperature (23 +/- 2 degrees C) under light exposure and light protection, +8 +/- 1 degrees C and -20 +/- 0.5 degrees C, in glass and plastic containers over 14 days with midazolam hydrochloride injection, undiluted or diluted with 5% dextrose sterile solution. Chromatographic separation was carried out on a RP-18(e) column, using a mobile phase consisting of ACN-phosphate buffer (pH 3.3; 0.1 M) (30:70 v/v) at a flow rate of 1.0 mL/min and UV detection at 220 nm. The concentrations of all samples remained greater than 90% of the original concentration. The chromatographic assay exhibited an adequate linearity (r(2) >0.999), selectivity, precision (RSD <3.1), and accuracy (recoveries from 100.46 to 101.40%). Injectable midazolam hydrochloride was chemically stable in all conditions that were studied.     

The stability of non-ionic surfactants and linear alkylbenzene sulfonates in a water matrix and on solid-phase extraction cartridges

The stability of nonylphenol ethoxylates (NPEO), alcohol ethoxylates (AEO), coconut diethanol amides (CDEA) and linear alkylbenzene sulfonates (LAS) in a water matrix and preconcentrated on SPE cartridges was studied. A stability study was carried out in a water matrix (spiked ground water and real-world waste water) comparing different pretreatment procedures (addition of sulfuric acid to pH = 3, preservation with 1% and 3% of formaldehyde). When stored in a water matrix serious qualitative and quantitative changes occurred in waste water during the period of time studied (30 days). The losses of C12-C14 alcohol ethoxylates ranged from 72% to 88% when the sample was preserved with acid and from 17% to 86% when the sample was preserved with formaldehyde (3%). Simultaneously, an enrichment of the shorter alkyl chain homologues (C7EO and C10EO) was observed. The losses of NPEO were from 45% (sample preserved by acidification or by addition of 3% of formaldehyde) to 85% (sample preserved with 1% of formaldehyde). Additionally, an increase in concentration of polyethylene glycols (PEGs) and formation of different acidic forms, such as monocarboxylated (MCPEGs) and dicarboxylated polyethylene glycols (DCPEGs) were observed. The stability of surfactants preconcentrated on SPE cartridges was studied as a function of storage time and storage conditions (room temperature, 4 degrees C and -20 degrees C). The results indicate that disposable SPE cartridges can be recommended for the stabilization of non-ionic surfactants and LAS. Storage at -20 degrees C is feasible for long periods (up to 3 months for ground water and up to 2 months for waste water), while storage at 4 C can be recommended for a maximum of 1 month. When cartridges were kept at -20 degrees C the losses of AEOs (n = 12, 13 and 14), preconcentrated from waste water, ranged from 17 to 29% (after 60 days) and other compounds suffered small losses (maximum of 14% for C13LAS). At room temperature, after 7 days, the losses were less than 11%, indicating that shipping of samples by mail can be done without any special requirements.     

Storage and stability of inorganic and methylmercury solutions

Summary The storage behaviour of mercurychloride and methylmercury chloride solutions in deionized water and in seawater stored in polyethylene (PE), pyrex glass and teflon (PTFE) containers at various concentration levels (4 ppb, 50 ppt, natural seawater concentrations) was studied using various preservatives and container pretreament procedures. For PE bottles, the best results are obtained, after pretreatment of the bottles with an acidified KMnO₄ solution, with a 0.05% (v/v) H₂SO₄+0.02% (w/v) KMnO₄ preservative. However, the solution becomes heterogeneous rather fast, due to the formation of a MnO₂ precipitate. Acidified (pH 1 with HNO₃) deionized or seawater samples stored in pyrex glass BOD-bottles (analyses are carried out in these bottles too) or teflon containers are stable with respect to inorganic mercury for at least 1 month. Instead of acidification an oxidant such as BrCl can also be used to stabilize the solution. Methylmercury solutions (80 ppt) in deionized water (pH 6) and stored in teflon containers are stable for at least 1 month. In glass bottles, the solution should be acidified to pH 1. Methylmercury seems to be unstable in acidified seawater samples (pH 1 with HNO₃); after 2 weeks about 60% of the methylmercury is converted into inorganic mercury.     

Screening method for determining the presence of N-nitrosodiethanolamine in cosmetics by open-tubular capillary electrochromatography

The presence of the carcinogenic N-nitrosodiethanolamine (NDELA; CAS No. 1116-54-7) in cosmetic samples was determined using an etched, C18 modified capillary in the open-tubular capillary electrochromatography technique. A very simple extraction procedure leads to a sample matrix free from interferences. The calibration curve was created using UV detection at 214 nm. The detector response was linear in the range of 5-120 ppm total amount injected. Minimum detection limits (1 ppm NDELA injected on capillary) are suitable for screening a large number of cosmetic samples. Diethanolamine and triethanolamine precursors of nitrosamines are not detected at the wavelength used. Cosmetic samples were analyzed unspiked and after addition of 60 ppm of NDELA. In spiked samples recoveries varied from 94% (hand and body lotion) to 55% (lipstick sample). NDELA was found in unspiked samples of old (5-15 years old) cosmetics at concentrations of 14.0 ppm and 35.0 ppm.     

Development and validation of a highly sensitive gas chromatographic-mass spectrometric screening method for the simultaneous determination of nanogram levels of fentanyl, sufentanil and alfentanil in air and surface contamination wipes

A highly sensitive gas chromatographic-mass spectrometric (GC-MS) analytical method for the determination of the opioid narcotics fentanyl, alfentanil, and sufentanil in industrial hygiene personal air samples and surface contamination wipes was developed and comprehensively validated. Sample preparation involved a single step extraction of the samples with methanol, fortified with a fixed amount of the penta-deuterated analogues of the opioid narcotics as internal standard. The GC-MS analytical procedure using selected ion monitoring (SIM) was shown to be highly selective. Linearity was shown for levels of extracted wipe and air samples corresponding to at least 0.1-2 times their surface contamination limit (SCL) and accordingly to 0.1-2 times their time weighted average occupational exposure limit (OEL-TWA) based on a full shift 9601 air sample. Extraction recoveries were determined for spiked air samples and surface wipes and were found to be quantitative for both sampling media in the entire range studied. The air sampling method's limit of detection (LOD) was determined to be 0.4 ng per sample for fentanyl and sufentanil and 1.6 ng per sample for alfentanil, corresponding to less than 1% of their individual OEL for a full shift air sample (9601). The limit of quantification (LOQ) was found to be 1.4, 1.2, and 5.0 ng per filter for fentanyl, sufentanil, and alfentanil, respectively. The wipe sampling method had LODs of 4 ng per wipe for fentanyl and sufentanil and 16 ng per wipe for alfentanil and LOQs of respectively, 14, 12, and 50 ng per wipe. The analytical intra-assay precision of the air sampling and wipe sampling method, defined as the coefficient of variation on the analytical result of six replicate spiked media was below 10 and 5%, respectively, for all opioids at all spike levels. Accuracy expressed as relative error was determined to be below 10%, except for alfentanil at the lowest spike level (-13.1%). The stability of the opioids during simulated air sampling was investigated. For fentanyl and sufentanil a quantitative recovery was observed at all spike levels, while for alfentanil recoveries ranged from 60.3 to 85.4%. When spiked air samples were stored at ambient temperature and at -15 degrees C quantitative recovery was found for fentanyl and sufentanil after 7 and 14 days. For alfentanil a slight loss seemed to occur upon storage during 7 days, being more explicit after 14 days. Ambient storage of spiked wipes seemed to lead to significant losses of all opioids studied, yielding recoveries of 37.7-88.3%. Upon storage of similar wipes at -15 degrees C a significantly higher recovery was found ranging from 77.3 to 88.3%. The developed analytical and sampling procedures have been recently applied in an explorative field study of which the results of surface contamination wipe sampling are presented in this paper. To our knowledge, this is the first study addressing the development and validation of analytical procedures for the assessment of external occupational exposure to potent opioid narcotics.     

An evaluation of analytical techniques for determination of lead, cadmium, chromium, and mercury in food-packaging materials

Closed microwave digestion and a high-pressure asher have been evaluated for wet-oxidation and extraction of lead, cadmium, chromium, and mercury from a range of typical packaging materials used for food products. For the high-pressure asher a combination of nitric and sulfuric acids was efficient for destruction of a range of packaging materials; for polystyrene, however, nitric acid alone was more efficient. For microwave digestion, a reagent containing nitric acid, sulfuric acid, and hydrogen peroxide was used for all materials except polystyrene. Use of the high-pressure asher resulted in the highest recoveries of spiked lead (median 92%), cadmium (median 92%), chromium (median 97%), and mercury (median 83%). All samples were spiked before digestion with 40 microg L(-1) Cd, Cr, and Pb and 8 microg L(-1) Hg in solution. The use of indium as internal standard improved the accuracy of results from both ICP-MS and ICP-AES. Average recovery of the four elements from spiked packaging materials was 92 +/- 14% by ICP-MS and 87 +/- 15% (except for mercury) by ICP-AES. For mercury analysis by CVAAS, use of tin(II) chloride as reducing agent resulted in considerably better accuracy than use of sodium borohydride reagent.     

The role of210Pb in evaluating container adsorption of Pb(II) from dilute aqueous solutions

Solutions of Pb²⁺ at ppb to ppm levels were tagged with²¹⁰Pb and then counted from time to time over a period of one year to measure the extent of container adsorption. All count rates for samples which were acidified with HNO₃ were at least 90% of their initial values, even after one year of storage. Amber glass containers proved to be superior to polypropylene for 0.1 and 1.0 ppm Pb²⁺ solutions; but below 0.1 ppm, polypropylene was superior. For non-acidified samples, the count rate dropped rapidly within the first two months, and then declined more gradually thereafter, with polypropylene generally superior.     

Prevention of loss of mercury(II) during storage of dilute solutions in various containers

Summary Losses of ionic mercury from various solutions of 30 ng Hg/ml and 1 g Hg/ml concentration stored in polyethylene, polypropylene, quartz and glass were studied for storage periods up to 57 days by means of the radiotracer technique. Distilled water solutions and solutions treated with HCl and HNO₃ lost substantial fractions of their mercury, whereby both adsorption and volatilization were involved. The largest losses (of up to 98%) occurred after the storage of water and nitric acid solutions in polyethylene. A combination of hydrochloric acid and hydrogen peroxide, also in the presence of nitric acid, proved to be excellently suited for preventing the loss of mercury. No detectable changes of mercury concentration were observed for solutions treated with 2% HCl + 2% H₂O₂ and stored in polyethylene for up to two months. After this storage period, the losses were < 2.5% for quartz, < 5% for glass and < 7% for polypropylene.

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Verhinderung von Quecksilber(II)-Verlusten bei der Lagerung verdünnter Lösungen in verschiedenen Behältern