Alkaline Digestion Method Research Articles

Factors Affecting the Detection of Hexavalent Chromium in Cr-Contaminated Soil

The alkali digestion pretreatment method in the United States Environmental Protection Agency (USEPA) Method 3060A could underestimate the content of Cr(VI) in Cr-contaminated soils, especially for soils mixed with chromite ore processing residue (COPR), which leads to a misjudgment of the Cr(VI) level in soils after remediation, causing secondary pollution to the environment. In this study, a new pretreatment method to analyze Cr(VI) concentration in contaminated soils was established. The impacts of soil quality, particle size, alkali digestion time and the rounds of alkali digestion on Cr(VI) detection in contaminated soils was explored and the alkali digestion method was optimized. Compared with USEPA Method 3060A, the alkaline digestion time was prolonged to 6 h and multiple alkali digestion was employed until the amount of Cr(VI) in the last extraction was less than 10% of the total amount of Cr(VI). Because Cr(VI) in COPR is usually embedded in the mineral phase structure, the hydration products were dissolved and Cr(VI) was released gradually during the alkaline digestion process. The amount of Cr(VI) detected showed high correlation coefficients with the percentage of F1 (mild acid-soluble fraction), F2 (reducible fraction) and F4 (residual fraction). The Cr(VI) contents detected by the new alkaline digestion method and USEPA Method 3060A showed significant differences for soil samples mixed with COPR due to their high percentage of residual fraction. This new pretreatment method could quantify more than 90% of Cr(VI) in Cr-contaminated soils, especially those mixed with COPR, which proved to be a promising method for Cr(VI) analysis in soils, before and after remediation.

Extraction of Stingray Liver Oil (Dasyatis Sp) with Alkaline Digestion Method

Stingray liver oil extraction method (Dasyatis sp) using alkaline digestion method with the addition of 2% concentrated NaOH reagent and HCL to maintain pH 8-9 by heating at 50°C for 3 hours can produce a yield of 35.74±0.38%. then with the addition of 3% magnesol XL adsorbent and centrifuged for 15 minutes at a speed of 5000 rpm can improve the quality of stingray liver oil (Dasyatis sp) by producing an FFA value of 0.40%±0.02, PV of 2.37±0, 05 mEq/kg, p-anisidin 5.72±1.95 mEq/kg, TOTOX 8.27±1.80 mEq/kg, AV 1.74±0.01 mg NaOH/kg, clarity 75, 19±1.7%.

Determination and characterization of metal nanoparticles in clams and oysters.

With the extensive application of nanotechnology, metal nanoparticles (MNPs) have been widely used, thus are universally detected in the environment. This has caused increasingly concerns due to their toxicity and the potential health risks they pose to humans. In this work, the concentrations and particle size distributions of MNPs and concentrations of associated metal ionic species in shellfish seafood (clams and oysters) were investigated using single particle inductively coupled plasma mass spectrometry (sp-ICP-MS) and inductively coupled plasma mass spectrometry (ICP-MS). The MNPs in the clam and oyster tissues were extracted via an alkaline digestion method with a recovery rate of 95.9% (for gold nanoparticles (AuNPs)). Then total concentrations of 41 metal elements were measured in the two types of seafood, of which 20 were selected for sp-ICP-MS analysis. The results showed that 5 types of MNPs were detectable in clams (Y, La, Ce, Pr, Gd) and 5 types of MNPs were detectable in oysters (Y, La, Ce, Pr, Nd). Size distributions of MNPs in clams and oysters were in the range of 35-55nm and 30-65nm, respectively. Nanoparticle concentrations in clams and oysters ranged from 0.6 to 37.7ng/g and 4.2-19.7ng/g, and accounted for 3.4%-50% and 5.5%-46% of the total metal content, respectively. Based on this analysis, the health risks of metals in the two kinds of seafood were evaluated by comparing the Provisional Tolerable Weekly Intake (PTWI) with limits recommended by the World Health Organization (WHO)/Food and Agriculture Organization (FAO). These results provide important information about the presence of metal nanoparticles in seafood and, to the best of our knowledge, this is the first time that the nanoparticles of rare earth elements have been detected and reported in bivalve mollusc tissues.

Baseline survey of micro and mesoplastics in the gastro-intestinal tract of commercial fish from Southeast coast of the Bay of Bengal

Plastics pollution is ubiquitous. Microplastics (<5 mm in diameter) and mesoplastics (5–20 mm in diameter) are emerging as the most common plastic particulates found in the marine environment. In this study, the occurrence of microplastics and mesoplastics in the gastrointestinal tract (GI) of some commercially important fish collected from Chennai and Nagapattinam of Tamil Nadu, Southeast coast of Bay of Bengal was assessed. A new and improved alkaline digestion method, using alcoholic potassium hydroxide (KOH) was carried out to destroy the organic matter. Following this method, twenty plastic particulates were isolated from the GI tract of 17 individual fish. Fourier Transform Infrared Radiation analysis (FTIR) showed that polymers found in GI tracts were of Polyethylene, Polyamide and Polyester types. Given the dry fish is India's biggest market and popular delicacy, the presence of microplastics in the fish gut is a potential serious human health concern, as they are directly consumed.

Gold Nanoparticle Uptake in Tumor Cells: Quantification and Size Distribution by sp-ICPMS

Gold nanoparticles (AuNPs) are increasingly studied for cancer treatment purposes, as they can potentially improve both control and efficiency of the treatment. Intensive research is conducted in vitro on rodent and human cell lines to objectify the gain of combining AuNPs with cancer treatment and to understand their mechanisms of action. However, using nanoparticles in such studies requires thorough knowledge of their cellular uptake. In this study, we optimized single particle ICPMS (sp-ICPMS) analysis to qualify and quantify intracellular AuNP content after exposure of in vitro human breast cancer cell lines. To this aim, cells were treated with an alkaline digestion method with 5% TMAH, allowing the detection of gold with a yield of 97% on average. Results showed that under our experimental conditions, the AuNP size distribution appeared to be unchanged after internalization and that the uptake of particles depended on the cell line and on the exposure duration. Finally, the comparison of the particle numbers per cell with the estimates based on the gold masses showed excellent agreement, confirming the validity of the sp-ICPMS particle measurements in such complex samples.

Extraction of Nanohydroxyapatite from Waste Bovine Bone Using Alkaline Digestion Method

Bovine bones from food waste are discarded without any effort to reclaim its potential as calcium sources. This study reports the preparation and characterization of nano hydroxyapatite from bovine bone waste (BvHAp) collected from local restaurant using alkaline digestion method. Fourier transformed infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses were used to verify the presence of hydroxyapatite in the bovine bone waste. Scanning electron microscopy (SEM) was also used to study the morphology of the apatite obtained. The SEM analysis revealed that the diameter size of nanoparticles BvHAp were around 20-30 nm. The energy dispersive X-ray (EDX) result indicated the calcium/phosphorous (Ca/P) ratio of obtained BvHAp after sintering at 1200 °C is 1.75 which is very closed to the theoretical value. The natural BvHAp produced has a potential source for biomaterials and food supplement applications.

Determination of perfluoroalkyl acid isomers in biosolids, biosolids-amended soils and plants using ultra-high performance liquid chromatography tandem mass spectrometry.

Isomer-specific analysis of perfluoroalkyl acids (PFAAs) is important to accurately assess their environmental source, fate, and human risks. In this study, a method was developed for the determination of perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), and perfluorohexane sulfonate (PFHxS) isomers in biosolids, biosolids-amended soils and plants using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The separation efficiencies of two chromatographic columns and extraction capacities of different methods were tested. Compared with the C18 column (ACQUITY UPLC BEH Shield RP18 column), the column with an alkyl perfluorinated C8 stationary phase (Epic FO LB column), in combination with the distinct MS/MS transitions of analytes, allowed better separation of most isomers. The ion-pair extraction method showed more effective matrix separation than that of the alkaline digestion method, with recoveries ranging from 79.6-105% for biosolids, 80.4-116% for soils, and 68.0-114% for plant tissues. The method detection limits ranged from 10 to 55, 3-13, and 8-58pg/g dry weight for biosolids, soil, and plants, respectively. This method was applied successfully to quantify individual isomers in biosolids, biosolids-amended soils and plants. Six PFOA, eight PFOS, and two PFHxS isomers were found in the samples, with linear isomers being the dominant species. Further analysis revealed that the translocation potentials of branched isomers within plants were higher than those of linear isomers.

Hybrid flow analyzer for automatic hollow-fiber-assisted ionic liquid-based liquid-phase microextraction with in-line membrane regeneration

The proof-of-concept of a new methodology for in-line hollow-fiber (HF)-assisted three-phase liquid-phase microextraction (LPME) allowing for handling of the feed and acceptor aqueous solutions and of minute volumes of the organic extracting phase in a programmable flow mode is reported in this paper. The flow analyzer fosters in-line anchoring of ionic-liquid-laden extracting solution (10 % (v/v) methyltrioctyl ammonium chloride in kerosene) in the pores of a single-strand microporous polypropylene HF, and regeneration of the liquid-phase membrane itself for each individual analysis cycle in a fully automated mode. Using hexavalent chromium as a model analyte and 1,5-diphenylcarbazide as a chromogenic probe in the acceptor solution, the flow-based HF-LPME hyphenated system was harnessed to the clean-up of troublesome samples (viz., domestic wastewater and soil leachates) with concomitant enrichment of target species. Distinct extraction modes and chemistries were assessed for enhanced Cr(VI) permeability. A single sample plug was subjected to a twofold backward-forward flow extraction so as to decrease the thickness of the boundary layer at the HF shell side for improved extraction efficiency. Under the optimized physicochemical variables, a limit of detection of 4.6 μg L(-1) Cr(VI), a dynamic linear range of up to 500 μg L(-1) and intermediate precision better than 10 % were obtained for a sample volume of 2.8 mL buffered at pH 4 and a volume of organic extractant of 120 μL, with an enrichment factor of ca. 11 for a sample residence time in the donor compartment of merely 4.5 min. Analyte recoveries in domestic wastewaters were ≥83 % using external calibration with relative standard deviations better than 14 %, thereby demonstrating the expedient clean-up of samples with elevated content of dissolved organic carbon. The automatic HF-LPME method was validated in terms of bias against the SRM 2701 (NIST soil) preceded by the EPA alkaline digestion method 3060A. No significant differences between Cr(VI) concentration as obtained with the automatic HF-LPME system (546 ± 57 mg kg(-1)) and the certified value (551.2 ± 17.2 mg kg(-1), expressed as mean ± combined uncertainty) were encountered at the 0.05 significance level.

Amorphous silica analysis in terrestrial runoff samples

The correct analysis of amorphous silica concentration (C ASi) in natural waters is crucial if one wants to correctly quantify terrestrial and/or riverine ASi fluxes. Soil ASi measurements are conducted with a constant solid to solution ratio (σ). As the suspended particulate matter concentration (C SPM), and therefore σ, cannot be exactly known a priori in river samples. It is important to understand how variations in σ effect analysed C ASi. The objectives of this paper are (i) to investigate whether and how variations in σ values affect measured C ASi in river runoff samples and (ii) to investigate whether or not it is possible to define a range of σ within which C ASi in runoff and/or soil samples can be accurately measured. For the laboratory experiment 30 runoff samples with a wide range of C SPM, typical for the Belgian Loam Belt, were prepared and analysed using the alkaline digestion method (0.1 M Na 2CO 3). Our study confirmed that the alkaline digestion method proposed by DeMaster can be used for runoff samples provided that σ is within certain limits: at very low σ (< 0.1 kg m −3), subsample heterogeneity results in high variability of measured C ASi while at higher σ values (> 0.8 kg m −3) incomplete dissolution of ASi as well as the reduction of mineral dissolution rates results in underestimated C ASi. As both errors compensate one another, the range of applicable σ-values can be extended above the theoretically correct limit (1.6 kg m −3). The finding that reliable measurements can be made within a relatively wide range of σ values (0.1 ≤ σ ≤ 1.6 kg m −3) is important. It is now possible to propose a method for the measurement of ASi in runoff samples. We make recommendations for ASi analysis distinguishing samples with a low and high C SPM. For samples with a low C SPM (≤ 1.6 kg m −3) the standard procedure is proposed while for samples with a high C SPM (> 1.6 kg m −3) an adapted procedure is proposed, analogue to that for soil samples. However, one should be aware that the range and limits for σ proposed here may depend on the type of sediment to be analysed: it is therefore recommended to evaluate the performance of the method again before it is used in other environments.

Assessment of chromium biostabilization in contaminated soils using standard leaching and sequential extraction techniques

The iron reducing microorganism Desulfuromonas palmitatis was evaluated as potential biostabilization agent for the remediation of chromate contaminated soils. D. palmitatis were used for the treatment of soil samples artificially contaminated with Cr(VI) at two levels, i.e. 200 and 500 mg kg − 1 . The efficiency of the treatment was evaluated by applying several standard extraction techniques on the soil samples before and after treatment, such as the EN12457 standard leaching test, the US EPA 3060A alkaline digestion method and the BCR sequential extraction procedure. The water soluble chromium as evaluated with the EN leaching test, was found to decrease after the biostabilization treatment from 13 to less than 0.5 mg kg − 1 and from 120 to 5.6 mg kg − 1 for the soil samples contaminated with 200 and 500 mg Cr(VI) per kg soil respectively. The BCR sequential extraction scheme, although not providing accurate estimates about the initial chromium speciation in contaminated soils, proved to be a useful tool for monitoring the relative changes in element partitioning, as a consequence of the stabilization treatment. After bioreduction, the percentage of chromium retained in the two least soluble BCR fractions, i.e. the “oxidizable” and “residual” fractions, increased from 54 and 73% to more than 96% in both soils.

Microwave enhanced alkaline digestion of silicate samples for determination of Fe 2O 3

A novel approach to the study of microwave enhanced alkaline digestion was developed for rapid digestion of silicate samples. By using alkali metal hydroxide solution as microwave digestion solvent, the feasibility and principle of digestion were discussed for the determination of Fe 2O 3 contents in quartz, kaolin, feldspar and soda-lime-silica glass. The results obtained from four standard samples and six real world samples are in good agreement with the certified values, and are comparable to the predicted results from traditional alkaline digestion method. All the above demonstrates that this new proposed method is precise, accurate and can provide a simple, fast and energy saving procedure for the determination of components in silicate samples.

Alkaline Digestion and Solid Phase Extraction Method for Perfluorinated Compounds in Mussels and Oysters from South China and Japan

Perfluorinated compounds (PFCs), such as perfluorooctane sulfonate (PFOS), have been identified in the coastal waters of China and Japan. An alkaline digestion method, coupled with solid-phase extraction (SPE), and high-performance liquid chromatography interfaced with high-resolution electrospray tandem mass spectrometry was developed to determine PFCs in mussel and oyster samples from coastal waters of South China and Japan. These techniques produced adequate recoveries and reporting limits with small quantities of PFCs. Concentrations of individual PFCs in mussels and oysters from South China and Japan ranged from 113.6 to 586.0 pg/g, wet weight (ww) for PFOS, 63.1 to 511.6 pg/g, ww for perfluorohexane sulfonate, 9.3 to 30.1 pg/g, ww for perfluorobutane sulfonate and 37.8 to 2957.0 pg/g, ww for perfluorooctane sulfonamide. The quantification of perfluorinated carboxylates was compromised by interferences from carboxylates in the procedural blanks. Perfluoroundecanoate and perfluorononanoate had relatively great blank interferences, which resulted in relatively poor limits of quantification for these compounds. Some PFCs were only identified in a limited number of samples: perfluorododecanoate in samples from Tokyo Bay, Japan (195.9 pg/g, ww); and perfluorodecanoate in Fuzhou, China (131.7 pg/g, ww) and Tokyo Bay (118.6 pg/g, ww). The greatest concentrations of perfluorooctanoate, perfluoroheptanoate, and perfluorohexanoate were observed in samples from Tokyo Bay and Bei Hai, South China.

Fast matrix digestion with hot ethanolic alkali plus pyrogallol for polychlorinated dibenzo- p-dioxins, polychlorinated dibenzofurans and coplanar polychlorinated biphenyls analysis in biological samples

The efficiency of hot alkaline digestion of a sample matrix was investigated for determination of polychlorinated dibenzo- p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (CoPCBs) in biological samples. Results of recovery tests of octachlorodibenzofuran (OCDF) after spiking into lean tuna showed degradation of OCDF and the production of a large quantity of lower-chlorinated dibenzofurans (LoCDFs) when the sample was digested with hot ethanolic KOH. However, it was also confirmed that pyrogallol (PG) prevented dechlorination of OCDF. The accuracy of the hot alkaline digestion method with PG was demonstrated by analyzing PCDD/Fs-spiked lean tuna. The proposed method is more suitable than conventional versions for the determination of dioxins in biological samples in terms of savings in time, adequate digestion of matrix and high degree of recovery of internal standards.

Extraction and cleanup methods of dioxins in house dust from two cities in Japan using accelerated solvent extraction and a disposable multi-layer silica-gel cartridge

A simple and rapid method for the extraction and cleanup of dioxins from house dust was developed using an accelerated solvent extraction (ASE) method and a multi-layer silica-gel cartridge. It was found that the WHO-TEQ levels of dioxins extracted from the house dust obtained by both a conventional soxhlet extraction and the ASE were almost equal, when the data obtained by both methods were compared. As for the cleanup method, a multi-layer silica-gel cartridge yielded higher dioxin recoveries than the alkaline digestion method. The average values of the dioxins in house dust from Kumagaya city and Sendai city in Japan (Sendai city is bigger than Kumagaya city with respect to the population and industry), were 15.6 pg TEQ/g (8.6–26.0 pg TEQ/g, n=5, Kumagaya city) and 16.0 pg TEQ/g (5.9–30.5 pg TEQ/g, n=5, Sendai city), respectively.

Hexavalent Chromium Extraction from Soils: Evaluation of an Alkaline Digestion Method

AbstractThe accurate quantification of total Cr(VI) in soils is relevant to human health concerns because Cr(VI) is significantly more toxic than Cr(III). Hot alkaline solution has been shown to extract soluble and insoluble forms of Cr(VI) from soils, but incomplete recovery of Cr(VI) spikes and the oxidation of soluble Cr(III) spikes in certain soils have been suggested as method deficiencies. A laboratory method study was performed to (i) test the method's accuracy, (ii) understand the soil chemical processes responsible for poor Cr(VI) spike recoveries, and (iii) develop definitive interpretations for Cr(VI) spike recovery data. Test results for &gt;1500 field soil samples and the method study of eight diverse soil materials demonstrated dissolution of soluble and insoluble Cr(VI) spikes and the method's reliability for Cr(VI) characterization. Complete dissolution of K2CrO4, BaCrO4, and PbCrO4 spikes confirmed the extraction of soluble and insoluble Cr(VI) forms. Ancillary soil chemical parameters, including oxidation‐reduction potential (ORP) (reported herein as Eh), pH, S2−, and total organic C were quantified and interpreted to explain poor Cr(VI) spike recoveries. Highly reducing samples yielded 0% Cr(VI) spike recoveries, as predicted from Eh‐pH relationships, and unspiked soil samples contained no detectable Cr(VI). In soils containing Cr(VI) and in most aerobic soils without native Cr(VI), acceptable Cr(VI) spike recoveries were obtained. Ancillary parameter characterization demonstrated that strongly reducing samples cannot maintain Cr(VI) laboratory matrix spikes. Correct interpretation of poor Cr(VI) spike recovery data should avoid labeling these data as unacceptable method results without ancillary parameter characterization of such samples.

Determination of biogenic silica in coastal waters: applicability and limits of the alkaline digestion method

The NaOH/HF digestion method, used for the determination of particulate biogenic silica (BSi) and of particulate lithogenic silica (LSi) in oceanic waters, has been applied to coastal waters. In the course of one year, 275 samples of suspended matter were collected at two stations located in the Bay of Brest and in the English Channel (Western Europe). In contrast to previous studies, significant leaching of silicic acid from lithogenic material during the NaOH attack is demonstrated, both for natural samples and for laboratory experiments with suspension of quartz, illite, and kaolinite (usual components of clay in suspended matter of those coastal waters); the interference of lithogenic material on biogenic silica determination averaged 15%. For samples collected during the period of low biological activity, plots of apparent biogenic silica concentrations vs. apparent lithogenic silica concentrations, show linear relationships for both study sites. These relationships are used to calculate corrected biogenic silica concentrations, BSi c. During the period of active diatom production, the precision for BSi c determination is better than 10%.

Elastin content of the human lung.

Summary1. An alkaline digestion method for quantitative determination of elastin has been adapted for study of lung parenchyma. 2. Concentration of elastin in the adult human lung has been determined over a wide age span, and has been found to increase with age. 3. Concentration of elastin in lung parenchyma subjacent to areas of bulla formation is significantly reduced.