Acid Extraction Method Research Articles

Health risk assessment of lead ingestion exposure by particle sizes in crumb rubber on artificial turf considering bioavailability.

ObjectivesThe purpose of this study was to assess the risk of ingestion exposure of lead by particle sizes of crumb rubber in artificial turf filling material with consideration of bioavailability.MethodsThis study estimated the ingestion exposure by particle sizes (more than 250 um or less than 250 um) focusing on recyclable ethylene propylene diene monomer crumb rubber being used as artificial turf filling. Analysis on crumb rubber was conducted using body ingestion exposure estimate method in which total content test method, acid extraction method and digestion extraction method are reflected. Bioavailability which is a calibrating factor was reflected in ingestion exposure estimate method and applied in exposure assessment and risk assessment. Two methods using acid extraction and digestion extraction concentration were compared and evaluated.ResultsAs a result of the ingestion exposure of crumb rubber material, the average lead exposure amount to the digestion extraction result among crumb rubber was calculated to be 1.56×10-4 mg/kg-day for low grade elementary school students and 4.87×10-5 mg/kg-day for middle and high school students in 250 um or less particle size, and that to the acid extraction result was higher than the digestion extraction result. Results of digestion extraction and acid extraction showed that the hazard quotient was estimated by about over 2 times more in particle size of lower than 250 um than in higher than 250 um. There was a case of an elementary school student in which the hazard quotient exceeded 0.1.ConclusionsResults of this study confirm that the exposure of lead ingestion and risk level increases as the particle size of crumb rubber gets smaller.

Rapid detection of Salmonella in pet food: design and evaluation of integrated methods based on real-time PCR detection.

Reducing the risk of Salmonella contamination in pet food is critical for both companion animals and humans, and its importance is reflected by the substantial increase in the demand for pathogen testing. Accurate and rapid detection of foodborne pathogens improves food safety, protects the public health, and benefits food producers by assuring product quality while facilitating product release in a timely manner. Traditional culture-based methods for Salmonella screening are laborious and can take 5 to 7 days to obtain definitive results. In this study, we developed two methods for the detection of low levels of Salmonella in pet food using real-time PCR: (i) detection of Salmonella in 25 g of dried pet food in less than 14 h with an automated magnetic bead-based nucleic acid extraction method and (ii) detection of Salmonella in 375 g of composite dry pet food matrix in less than 24 h with a manual centrifugation-based nucleic acid preparation method. Both methods included a preclarification step using a novel protocol that removes food matrix-associated debris and PCR inhibitors and improves the sensitivity of detection. Validation studies revealed no significant differences between the two real-time PCR methods and the standard U.S. Food and Drug Administration Bacteriological Analytical Manual (chapter 5) culture confirmation method.

Validation of high throughput methods for tissue disruption and nucleic acid extraction for ranaviruses (family Iridoviridae)

Viruses in the family Iridoviridae cause severe disease and economic loss in a wide range of cultured, wild and ornamental fish species in many countries, justifying the development and validation of diagnostic tests. In an effort to improve the efficiency of test protocols, in this study manual and high throughput semi-automated methods for tissue homogenisation and nucleic acid purification were compared for the detection of Epizootic Haematopoeitic Necrosis Virus (EHNV). The effectiveness of these methods at releasing EHNV particles and obtaining DNA was evaluated by virus isolation in bluegill fry (BF-2) cells, enzyme-linked immunosorbent assay (ELISA) and quantitative polymerase chain reaction (qPCR). Samples were prepared using tissue from infected redfin perch (Perca fluviatilis). Antigen and DNA yield were greater after homogenisation by bead-beating than by manual grinding of tissues from experimentally infected fish, which contained low quantities of virus. Bead-beating was compatible with virus isolation. There was no difference between the manual and semi-automated methods using samples from naturally infected fish which contained large amounts of virus. There was no difference in DNA yield between manual and semi-automated nucleic acid extraction for experimentally infected fish, however nucleic acid yields were greater after manual extraction for samples from naturally infected fish. Semi-automated tissue homogenisation and nucleic acid extraction required the least amount of time and were the most cost effective. The results of this study can be used as a guide to the selection of sample preparation procedures for other ranaviruses and probably more widely.

Evaluation of a Rapid PCR-Based Method for Species Identification of Raw and Processed Fish and Shrimps

The increase of mislabeled seafood and illegal fisheries demands rapid methods to control fishery products. We have tested a rapid deoxyribonucleic acid (DNA) extraction and amplification method to identify raw and processed fish and shrimp using polymerase chain reaction (PCR)-based techniques. The KAPA Express Extract Kit delivered DNA from raw, cooked, canned, and marinated products that was suitable for mutation detection. Segments of mitochondrial genes, sized from 123 to 464 base pairs (bp), were amplified by PCR kits from two vendors. Amplicons of raw fish fillets were differentiated by single strand conformation polymorphism (SSCP) analysis, raw or cooked shrimps were analyzed by restriction fragment length polymorphism (RFLP), and the PCR product obtained for marinated herring was sequenced. The extracted DNA was not degraded during storage in the refrigerator for about 1 week or in the freezer-cabinet for 1 month.

Modular Ultrasonic Lysis System for Rapid Nucleic Acid Extraction and Sample Transfer of Bacillus Spores

This paper describes the design, functioning and use of an ultrasonic modular system intended for rapid extraction and fragmentation of DNA from microbial organisms following sample collection in the field. PCR assessment of the DNA extracts revealed that the system can disrupt Bacillus atrophaeus spores, a simulant for Bacillus anthracis, in less than 1 min, providing a DNA yield equivalent to that of a commercial nucleic acid extraction method. Simulation of the transfer from a contaminated to a secure area confirmed that the sample remained confined within the module while the exterior surface can be decontaminated through immersion in a disinfectant solution.

A cost-effective and rapid microwave-assisted acid extraction method for the multi-elemental analysis of sediments by ICP-AES and ICP-MS

A very simple, cost-effective and rapid single-step microwave-assisted leaching procedure using screw-capped polypropylene (PP) tubes and a domestic microwave oven has been developed for the extraction of elements from sediments followed by their analysis using inductively coupled plasma spectrometric techniques (ICP-AES/ICP-MS). Parameters affecting the microwave-assisted extraction such as extractant concentration, microwave irradiation time, microwave power and sample amount were optimized to get quantitative recovery of elements by taking two certified reference materials: stream sediment GBW-7312 and marine sediment IAEA-433. The supernatant obtained upon centrifugation was used for analysis of various elements: Na, K, Ca, Mg, Fe, Al, Li, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, As, Sr, Mo, Ag, Cd, Sn, Sb, Cs, Ba, Tl, Pb and Bi. Quantitative recoveries of elements of interest were obtained using a mixture of 30% HNO3 + 5% HF with 30 s irradiation time at a microwave power of 640 W for <500 mg sample weight. The results obtained here were in good agreement with the certified values with an overall precision of better than 10%. The obtained results showed that the present method of microwave assisted leaching (employing 30% HNO3 + 5% HF) of sediment reference materials without resorting to total digestion produced an efficient attack of the most important metal bearing mineral phases and the quantitative recoveries obtained here showed complete leaching of the elements of interest. The procedure is especially attractive as it requires a microwave irradiation time of less than a minute and is thus extremely rapid.

Effects of Solid-Medium Type on Routine Identification of Bacterial Isolates by Use of Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) is a rapid method for the identification of bacteria. Factors that may alter protein profiles, including growth conditions and presence of exogenous substances, could hinder identification. Bacterial isolates identified by conventional methods were grown on various media and identified using the MALDI Biotyper (Bruker Daltonics, Billerica, MA) using a direct smear method and an acid extraction method. Specimens included 23 Pseudomonas isolates grown on blood agar, Pseudocel (CET), and MacConkey agar (MAC); 20 Staphylococcus isolates grown on blood agar, colistin-nalidixic acid agar (CNA), and mannitol salt agar (MSA); and 25 enteric isolates grown on blood agar, xylose lysine deoxycholate agar (XLD), Hektoen enteric agar (HE), salmonella-shigella agar (SS), and MAC. For Pseudomonas spp., the identification rate to genus using the direct method was 83% from blood, 78% from MAC, and 94% from CET. For Staphylococcus isolates, the identification rate to genus using the direct method was 95% from blood, 75% from CNA, and 95% from MSA. For enteric isolates, the identification rate to genus using the direct method was 100% from blood, 100% from MAC, 100% from XLD, 92% from HE, and 87% from SS. Extraction enhanced identification rates. The direct method of MALDI-TOF analysis of bacteria from selective and differential media yields identifications of varied confidence. Notably, Staphylococci spp. from CNA exhibit low identification rates. Extraction enhances identification rates and is recommended for colonies from this medium.

Investigations into matrix components affecting the performance of the official bioassay reference method for quantitation of paralytic shellfish poisoning toxins in oysters

Significant differences previously observed in the determination of paralytic shellfish poisoning toxins (PSTs) in oysters using official method AOAC 2005.06 and 959.08 were investigated in detail with regard to possible matrix effects. Method AOAC 2005.06 gave results 2–3 times higher than the mouse bioassay method, 959.08, differences thought to be due to underestimation of PSTs by the mouse bioassay. In order to prove the cause of these large differences, work was conducted here to examine the presence and effects of matrix components on the performance of each of the two assays. A range of oyster, cockle and mussel samples were extracted using the AOAC 959.08 hydrochloric acid (HCl) extraction method and analysed for PSP by both MBA and LC-FLD. In addition, extracts were analysed by Inductively Coupled Plasma Mass Spectrometry (ICP–MS) for metals as well as being subjected to a range of nutritional testing methods. Whilst there was no evidence for effect of nutritional components on either assay, ICP–MS analysis revealed a relationship between samples exhibiting the largest differences in relative method performance, specifically those with the largest LC-FLD/MBA toxicity ratio, and samples containing the highest concentrations of zinc and manganese. In order to prove the potential effect of the metals on either the LC-FLD and/or MBA assays, HCl extracts of a range of shellfish were subjected to a number of matrix modifications. Firstly, a number of PSP-positive oyster samples were processed to reduce the concentrations of metals within the extracts, without significantly reducing the concentrations of PSTs. Secondly, a range of mussel and cockle extracts, plus a standard solution of saxitoxin di-hydrochloride were spiked at variable concentrations of zinc. All treated and non-treated extracts, plus a number of controls were subjected to ICP–MS, LC-FLD and MBA testing. Results proved the absence of any effect of metals on the performance of the LC-FLD, whilst showing a large suppressive effect of the metals on the MBA. As such, the results show the performance of the official MBA is potentially unsafe for application to the routine monitoring of PSP toxicity in oysters or in any other shellfish found to contain high concentrations of metal ions.

Bitumen biomarkers in the Mid-Proterozoic Ilímaussaq intrusion, Southwest Greenland – A challenge to the mantle gas theory

GC and GC/MS/MS analysis on rock extracts has shown that the bitumen in the peralkaline Ilímaussaq intrusion, previously assumed to be abiogenic, is biotic in origin. A biotic origin is in accordance with previously published stable carbon isotopic data on bituminous matter in the rocks. The biomarker distribution in the bitumen, including the less common bicadinanes, resembles that of oil seeps on the central West Greenland coast 2200 km farther north, whose source rocks and migration history are relatively well established. We use a recent re-construction of the subsidence and later exhumation of the West Greenland coastal region during the Mesozoic-Cenozoic ( Japsen et al., 2006a, b) to anticipate that hydrocarbons migrated from deeper parts of the basin offshore west of Greenland. The rocks of Ilímaussaq were probably more deeply invaded than the surrounding granites due to their higher proportion of corroded minerals, which may explain why bitumen has not been observed elsewhere in the area. Hydrocarbon gases (C1–C5) present in fluid inclusions were also analysed, after having been released by treatment with hydrochloric acid that resulted in an almost complete disintegration of the Ilímaussaq intrusion rocks. The acid extraction method proved generally more efficient than the crushing procedure applied by others, but gave similar results for the chemical composition of the gas (CH 4: 88–97%) and isotopic ratios (δ 13 C CH 4 : −1.6 to −5.0‰; δ 13 C C 2 H 6 : −9.2 to −12.5‰), with the exception of hydrocarbons hosted in quartz, which showed significantly lower isotopic values for methane ( Graser et al., 2008). Previous researchers have suggested an abiotic origin for these hydrocarbon gases, but we suggest a biotic origin for the majority of them, not just those in quartz, assuming that the isotopic ratio of the constituents have changed due to loss of gas by diffusion. The assumption of gas loss via diffusion is supported by published studies on micro-fissures in minerals typical of the Ilímaussaq and field investigations showing diffusive loss of gas from the peralkaline Khibina and Lovozero massifs on the Kola Peninsula, Russia, which are, in many respects of mineralogy and hydrocarbon content, similar to the Ilímaussaq intrusion. Both the hydrocarbon gases and bitumen in the Khibina and Lovozero massifs have been cited as prime examples of a deep mantle source, although the carbon isotopic ratio of the bitumen clearly pointed to an organic origin. The trends in carbon isotopic ratio of methane released with time from freshly exposed rocks also supports our hypothesis of 13C enrichment of the methane remaining within the rock. Thus, there is good evidence that the hydrocarbons in the Kola alkaline massifs are mostly biotic in origin, in which case the probability of finding economic hydrocarbon accumulations from a deep mantle source seems exceedingly small.

Relevance of Radiocaesium Interception Potential (RIP) on a worldwide scale to assess soil vulnerability to 137Cs contamination

The extent of radiocaesium retention in soil is important to quantify the risk of further foodchain contamination. The Radiocaesium Interception Potential (RIP – Cremers et al., 1988, Nature 335, 247–249) is an intrinsic soil parameter which can be used to categorize soils or minerals in terms of their capacity to selectively adsorb radiocaesium. In this study, we measured RIP for a large soil collection (88 soil samples) representative of major FAO soil reference groups on a worldwide scale and tested the possibility to predict the RIP on the basis of other easily accessible or measurable soil data. We also compared RIP values with those obtained from separate chemical extraction experiments. The range of measured RIP values (1.8–13300 mmol kg −1) was shown to include nearly all possible cases of agricultural soil contamination. Only Podzols, Andosols and Ferralsols were clearly characterized by a very low RIP (<2000 mmol kg −1). On a worldwide scale, RIP was in fact slightly related to soil reference type or other simple major physicochemical parameters such as clay percentage or organic matter. Conversely our results indicated a link between the RIP and radiocaesium extractability across very different soils. We showed that, with the proposed scale of RIP values, a simple acid extraction method can provide an operational result highly predictive of potential RIP despite very contrasting soil properties. The RIP could be estimated from the empirical equation: RIP = (−31.701 ∗ log(AER) + 58.886) 2 where AER is the fraction of acid-extractable radiocaesium.

Homogenization with heat treatment: A cost effective alternative to nucleic acid extraction for herpes simplex virus real-time PCR from viral swabs

Most laboratories use expensive commercial kits to purify nucleic acids and remove PCR inhibitors that may be present in clinical specimens. In this study a simple homogenization with heat treatment of herpes simplex virus types 1 and 2 (HSV-1/2) was shown to be equivalent to commercial kit-based nucleic acid extraction methods. With a cost of less than $1 USD per extraction, this method provides an economical, rapid, and effective method to recover HSV-1/2 DNA from swabs suitable for real-time HSV PCR.

Nucleic acid quantity and quality from paraffin blocks: Defining optimal fixation, processing and DNA/RNA extraction techniques

Although the extraction and analysis of nucleic acids from formalin-fixed paraffin-embedded tissues is a routine and growing part of pathology practice, no generally accepted recommendations exist to guide laboratories in their selection of tissue fixation, processing and DNA/RNA extraction techniques. The aim of this study was to determine how fixation method and length, paraffin embedding, processing conditions and nucleic acid extraction methods affect quality and quantity of DNA and RNA, and their performance in downstream applications. Nine tissue samples were subjected to freezing, fixation in formalin for <24h and 7days followed by conventional processing, and fixation in molecular fixative for <24h and 7days followed by rapid processing. DNA and RNA were isolated using in-house extraction and commercial kits, and assessed by PCR reactions for amplicons with varying sizes ranging from 268 to 1327bp and one-step RT-PCR for 621bp and 816bp amplicons of housekeeping genes. Molecular fixative (MF) appeared to perform well under nearly all circumstances (extraction methods, fixation lengths and longer amplicons), often performing as well as frozen samples. Formalin fixation generally performed well only for shorter length amplicons and short fixation (<24h). WaxFree kit showed consistently higher success rates for DNA and poorer rates for RNA. RecoverAll kit generally performed suboptimally in combination with prolonged formalin fixation. In conclusion, the Molecular Fixative regardless of fixation length, and the rapid tissue processing system were able to preserve large DNA and RNA fragments in paraffin blocks, making these techniques preferable for use in downstream molecular diagnostic assays.

Evaluation of Two Magnetic-Bead-Based Viral Nucleic Acid Purification Kits and Three Real-Time Reverse Transcription-PCR Reagent Systems in Two TaqMan Assays for Equine Arteritis Virus Detection in Semen

This study showed that under specifically defined conditions with respect to nucleic acid extraction method and testing reagents, a previously described real-time reverse transcription-PCR (rRT-PCR) assay (T1 assay) provides sensitivity equal to or higher than that of virus isolation for the detection of equine arteritis virus in semen.

Development of a Real-time RT-PCR Assay for Squash Mosaic Virus Useful for Broad Spectrum Detection of Various Serotypes and its Incorporation into a Multiplex Seed Health Assay

Seed-borne pathogens pose a serious threat to modern agricultural cropping systems, as they can be disseminated to many geographical regions around the world. With trends of increasing global seed production and trade, seed-health testing is an important quality control step to prevent the introduction of harmful pathogens into agricultural production systems. An effective seed-health assay depends on a test that can provide timely, sensitive and broad-spectrum detection of all genetic variants of a pathogen, or in some cases, of several different pathogens. Previously, we developed a real-time PCR (qPCR) assay that would permit the simultaneous detection of two major seed-borne pathogens of cucurbits, the bacterium Acidovorax avenae subsp. citrulli (AAC, the causal agent of bacterial fruit blotch) and a fungus Didymella bryoniae (DB, the causal agent of gummy stem blight). The objective of the present study was to develop a sensitive, reverse transcriptase (RT)-based, qRT-PCR for broad spectrum detection of both serotypes of Squash mosaic virus (SqMV), that could be incorporated into a simultaneous detection of three pathogen types in a single PCR reaction. Converting SqMV RNA to cDNA prior to multiplexing stabilized the viral template that was then mixed with two other DNA templates (AAC and DB). To facilitate seed health testing, a generic plant nucleic acid extraction method was developed for cucurbit seeds. Using this method, nucleic acids extracted from seeds yielded strong signals for each target pathogen in multiplex qPCR. The ability to use a general nucleic acid extraction technique with subsequent PCR to detect bacterial, fungal and viral plant pathogens lends itself to a universal system for cucurbit seed health testing.

Comparative evaluation and selection of a method for lipid and fatty acid extraction from macroalgae

A comparative evaluation of Bligh and Dyer, Folch, and Cequier-Sánchez methods for quantitative determination of total lipids (TLs) and fatty acids (FAs) was accomplished in selective green ( Ulva fasciata), red ( Gracilaria corticata), and brown algae ( Sargassum tenerrimum) using a full factorial categorical design. Applications of sonication and buffer individually on lipid extraction solvent systems were also evaluated. The FA recoveries obtained from the aforementioned methods were compared with those of direct transesterification (DT) methods to identify the best extraction methods. The experimental design showed that macroalgal matrix, extraction method, and buffer were key determinants for TL and FA recoveries ( P ⩽ 0.05), exhibiting significant interactions. But sonication gave erratic results with no interaction with any of the factors investigated. The buffered solvent system of Folch rendered the highest TL yield in U. fasciata and G. corticata while the buffered system of Bligh and Dyer gave the highest yield in S. tenerrimum. DT methods were more convenient and accurate for FA quantification and rendered 1.5–2 times higher yields when compared with the best conventional method, minimizing the use of chlorinated solvents, their cost of analysis, and disposal. The buffered solvent system was found to be the most appropriate for lipid research in macroalgae.

The recovery of nucleic acid from biomining and acid mine drainage microorganisms

The cornerstone of biological molecular techniques is the extraction of the intra- or extra-cellular component of interest. However, inefficiencies in the extraction method can lead to results that are not representative of the microbial population under investigation. It is particularly difficult to extract clean and pure samples of the cellular component of interest from the microbial inhabitants of low-pH, sulfidic environments, such as those found in biomining or acid mine drainage (AMD). A number of nucleic acid (NA) extraction methods were tested using microorganisms commonly found in biomining and AMD environments, including archaea and Gram-negative and Gram-positive bacteria. The different stages in the methods of NA extraction were investigated separately, including the: (i) removal of cells from pyrite, (ii) cell lysis and nucleic acid extraction, (iii) nucleic acid precipitation and (iv) RNA purification using, as appropriate, microscopy, spectrophotometry, agarose gel electrophoresis of NA, PCR, quantitative-PCR and quantitative reverse transcriptase-PCR to assess the quality and quantity of the DNA and RNA. The relative percentage of NA recovered from each microorganism using the optimised method discussed in this paper returned the following percentage of NA per cell: At. ferrooxidans 91% ± 1.4%; At. caldus 91% ± 2.7%; L. ferriphilum 98% ± 1.2%; F. acidiphilum 83% ± 2.9%; and S. thermosulfidooxidans 79% ± 0.7%. Differences in lysis methods and NA precipitation greatly impacted the quality and quantity of the extracted NA. A method for the reliable, representative and reproducible extraction of NA from five strains of biomining and AMD microorganisms from pyrite and from liquid culture is described.

폐자원을 이용한 사격장 토양내 중금속(Pb, Cu) 안정화 처리

In this study, a heavy metal stabilization treatment using waste resource stabilizing agents was utilized on army firing range soil contaminated with Pb and Cu. Both calcined oyster shells (COS; 5% w/w) and waste cow bone (WCB; 3% w/w) were applied for a wet-curing duration of 28 days. Following the stabilization treatment, the process efficiency was evaluated by various extraction methods for Pb and Cu. Neutral and weak acid extraction methods, such as water soluble extraction and SPLP, did not show positive results for heavy metal stabilization with very low leachability. On the other hand, TCLP and 0.1 N HCl extraction showed that the stabilizing agents significantly reduced the amount of the heavy metals leached from the soil, which strongly supports that the treatment efficiency is positively evaluated in acidic leaching conditions. Specifically, in the 0.1 N HCl extraction, the reduction efficiencies of Pb and Cu leaching were 99.9% and 83.9%, respectively. From the sequential extraction results, a difference between Pb and Cu stabilization was observed, which supports that Pb stabilization is more effective due to the formation of insoluble Pb complexes. This study demonstrates that the application of waste resources for the stabilization of heavy metals is feasible.

Evaluation of Spectrophotometric and HPLC Methods for Shikimic Acid Determination in Plants: Models in Glyphosate-Resistant and -Susceptible Crops

Endogenous shikimic acid determinations are routinely used to assess the efficacy of glyphosate in plants. Numerous analytical methods exist in the public domain for the detection of shikimic acid, yet the most commonly cited comprise spectrophotometric and high-pressure liquid chromatography (HPLC) methods. This paper compares an HPLC and two spectrophotometric methods (Spec 1 and Spec 2) and assesses the effectiveness in the detection of shikimic acid in the tissues of glyphosate-treated plants. Furthermore, the study evaluates the versatility of two acid-based shikimic acid extraction methods and assesses the longevity of plant extract samples under different storage conditions. Finally, Spec 1 and Spec 2 are further characterized with respect to (1) the capacity to discern between shikimic acid and chemically related alicyclic hydroxy acids, (2) the stability of the chromophore (t1/2), (3) the detection limits, and (4) the cost and simplicity of undertaking the analytical procedure. Overall, spectrophotometric methods were more cost-effective and simpler to execute yet provided a narrower detection limit compared to HPLC. All three methods were specific to shikimic acid and detected the compound in the tissues of glyphosate-susceptible crops, increasing exponentially in concentration within 24 h of glyphosate application and plateauing at approximately 72 h. Spec 1 estimated more shikimic acid in identical plant extract samples compared to Spec 2 and, likewise, HPLC detection was more effective than spectrophotometric determinations. Given the unprecedented global adoption of glyphosate-resistant crops and concomitant use of glyphosate, an effective and accurate assessment of glyphosate efficacy is important. Endogenous shikimic acid determinations are instrumental in corroborating the efficacy of glyphosate and therefore have numerous applications in herbicide research and related areas of science as well as resolving many commercial issues as a consequence of glyphosate utilization.

Development and evaluation of a method for hexavalent chromium in ambient air using IC-ICP-MS

The challenge to quantify ambient airborne Cr(VI) comes from three interrelated issues: sensitivity, selectivity, and stability. In this study, we developed a sensitive and reliable method to measure Cr(VI) in ambient air by optimizing each step involved in measurement. The enriched isotope was employed to determine the recovery and inter-conversion between Cr species (valences) during sampling, sample storage and chemical analysis. Specifically, ambient particles were collected on a 47-mm mixed cellulose ester (MCE) filter that was pre-cleaned by HNO3 (10% v/v) and pre-treated with NaHCO3 (2 g L−1). 53Cr(VI) and 50Cr(III) isotopes (4 ng each) were spiked on the filter either before or after sampling. Samples were subsequently sonicated in 5 mL HNO3 (pH 4) solution at 60 °C for 40 min, and separated and analyzed for Cr(VI) and Cr(III) by IC-ICP-MS. The method detection limit was 0.08 ng m−3 and the percent difference was <25% for the collocated samples. The recovery of the spiked Cr(VI) and the conversions between Cr(III) and Cr(VI) varied with matrix (clean filter, NIST 1648 PM, and ambient PM), and lower recoveries and higher inter-conversions were found for Cr species spiked before sampling than the post-sampling spikes. These results showed the effects of sampling process and particle matrix on the stability of Cr species. The effects of co-existing PM elements on Cr(VI) recovery and conversion were also examined and discussed. The acid extraction method developed in this study was compared to the ERG carbonate buffer extraction method using 53Cr(VI) isotope spiked NIST 1648 PM. The recoveries of 53Cr(VI) were 90.9% ± 8.8% (N = 11) for our acid extraction method and 89.8% ± 10% (N = 10) for the ERG carbonate buffer extraction, respectively. The ambient Cr(VI) concentrations in an urban area in NJ measured with the developed method are also reported in the manuscript.

Giardia intestinalis: DNA extraction approaches to improve PCR results

Difficulty in disrupting cysts of Giardia intestinalis, a cosmopolitan protozoan parasite, decreases the yield of DNA extracted and reduces the effectiveness of the polymerase chain reaction (PCR). To improve the detection of the Giardia Glutamate Dehydrogenase (gdh) gene, we re-evaluated the effects of deoxyribonucleic acid (DNA) extraction methods. Purified and concentrated cysts from 33 fecal samples were disrupted using conventional methods, and DNA extraction was conducted using two protocols: the QIAamp Stool Mini Kit and phenol/chloroform/isoamyl alcohol (PCI). PCR amplification was successful for 12 extracted DNA samples (36%) using PCI following a glass bead and freeze/thaw pretreatment and for all 33 samples (100%) using the QIAamp Stool Mini Kit following the aforementioned pretreatment. Consequently, the pretreatment of cysts with glass beads and freeze/thaw cycles followed by extraction of DNA with the QIAamp Stool Mini kit was the more effective protocol.