Evaluation of two portable lead-monitoring methods at mining sites

Two methods for measuring airborne lead using field-portable instruments have been developed by the National Institute for Occupational Safety and Health (NIOSH): Method 7702 uses X-ray fluorescence (XRF), and Method 7701 employs ultrasonic extraction (UE) followed by anodic stripping voltammetry (ASV). The two portable methods were evaluated at mining sites. Area air samples were collected throughout two mills where ore from nearby mines was processed; the primary constituent of the ore was lead sulfide (galena). The air samples were collected on 37 mm mixed cellulose ester membrane filters housed within plastic filter cassettes. At the end of the work shift, the cassettes were collected and taken to a room off-site for analysis by the two portable methods. The filter samples were first analyzed by XRF and then by UE/ASV. Calibration was verified on both instruments according to standard procedures. The samples were then sent for confirmatory analysis via flame atomic absorption spectrometry (FAAS) according to NIOSH Method 7082. Pairwise comparisons between the methods using the paired t-test showed no statistically significant differences between ASV and FAAS (P>0.05); however, the comparison between XRF and FAAS was statistically significant (P<0.05). The elevated lead concentrations reported by XRF relative to FAAS were likely the result of the ability of XRF to report total lead, including lead silicates. This form of lead is not liberated in the digestion process prior to FAAS analysis, and is therefore not detected by this method. Despite this discrepancy, lead concentrations measured by both portable technologies were found to be highly correlated with the laboratory method (R2>0.96), suggesting that they are suitable as screening methods for airborne lead at mining sites.     

Separation,preconcentration and inductively coupled plasma-mass spectrometric (ICP-MS) determination of thorium(IV), titanium(IV), iron(III), lead(II) and chromium(III) on 2-nitroso-1-naphthol impregnated MCI GEL CHP20P resin

A simple and effective method is presented for the separation and preconcentration of Th(IV), Ti(IV), Fe(III), Pb(II) and Cr(III) by solid phase extraction on 2-nitroso-1-naphthol impregnated MCI GEL CHP20P resin prior to their inductively coupled plasma-mass spectrometric determinations. The influence of analytical parameters including pH of the aqueous solution, flow rates of sample and eluent solutions and sample volume on the quantitative recoveries of analyte ions was investigated. Matrix effects caused by the presence of alkali, earth alkali and some metal ions in the analyzed solutions were investigated. The presented solid phase extraction method was applied to BCR-144R Sewage Sludge (domestic origin), BCR-141R Calcareous Loam Soil, NIST 1568a Rice Flour and NIST 1577b Bovine Liver certified reference materials (CRMs) for the determination of analyte ions and the results were in good agreement with the certified values. The separation procedure presented was also applied to the various natural water samples collected from Turkey with satisfactory results.     

GB/T 229-2007金属材料夏比摆锤冲击试验方法简介

介绍了新修订的GB/T 229—2007规定的金属材料夏比摆锤冲击试验方法,并与ASTM E23—2007进行了比较,分别从适用范围、试样要求、设备要求、试验过程及试验结果评定等主要技术要求方面进行了对比说明。结果表明:GB/T 229—2007较修订前的旧版本与ASTME23—2007的差异有所缩小,但两标准仍存在较大的差别。     

Evaluation of an ultrasonic acid digestion procedure for total heavy metals determination in environmental and biological samples

In this study, a sample preparation method based on ultrasonic assisted acid digestion (UAD) has been evaluated for total heavy metals (Cd, Cr, Ni and Pb) determination in different environmental (soil, sediment and sewage sludge), and biological (fish muscles, vegetables and grains) samples, using electrothermal atomic absorption spectrometry (ETAAS). The investigated parameters influencing UAD such as presonication time, sonication time, temperature of ultrasonic bath, and different acid mixtures were fully optimized, whereas power was maintained constant at 100% of nominal power of ultrasonic bath. Six different sets of above parameters were applied on six certified reference materials (CRMs) having different matrices. The accuracy of the method was also tested by comparing the results with those obtained from conventional hot plate assisted acid digestion method on same CRMs. Analytical results for HMs by both methods showed no significant difference at 95% confidence limit (p<0.05). Recoveries of HMs ranging from 96.2% to 102% and 96.3% to 98.6% were obtained from biological and environmental samples, respectively. The average relative standard deviation of UAD method varied between 3.5% and 8.2%, depending on the analyte.     

Ligand-assisted extraction for separation and preconcentration of gold nanoparticles from waters

A new two-step extraction procedure is proposed for separation and preconcentration of gold nanoparticles (Au-NPs) from aqueous samples. First, Au-NPs are loaded onto a reversed phase C-18 (RP-C18) column, and then ligand-assisted extraction into chloroform is performed. 1-Dodecanethiol (1-DDT, 5 mM) was used as selective ligand for quantitative extraction under ultrasonic condition. Parameters of the extraction procedure, such as sample volume, organic solvent, concentration and nature of the ligand, ultrasonication time, pH of the sample, and different coating as well as sizes of Au-NPs were investigated in regard to the extraction efficiency of Au-NPs. The optimized procedure allows separation and preconcentration of the Au-NPs with an enrichment factor of up to 250 assuring no changes in size and/or shape of the NPs. This was proved by investigation of the particles by UV-vis spectrometry and transmission electron microscopy (TEM). Furthermore, the presence of potentially interfering other metal nanoparticles (M-NPs) and dissolved organic matter (DOM) was studied. Observed minor recoveries of Au-NPs in DOM model solutions were overcome by hydrogen peroxide pretreatment up to a DOM concentration of about 4 mg/L. Feasibility of the proposed method was proved by application of the optimized procedure to 5 real water samples. Recoveries of Au-NPs in the real waters spiked in a concentration range from 0.15 to 5100 μg/L obtained by this method varied from 68.4% to 99.4%. Consequently, the proposed approach has great potential for the analysis of M-NPs in environmental waters.     

Design of newly fabricated tribological machine for wear and frictional experiments under dry/wet condition

Nowadays, there is demand to evaluate tribological performance of new engineering materials using different techniques. Various laboratory tribo-machines have been designed and fabricated such as Pin-on-Disc (POD), ASTM G99, Block-on-Ring (BOR), ASTM G77 or G137-953, Dry Sand Rubber Wheel (DSRW), ASTM G655, Wet Sand Rubber Wheel (WSRW), ASTM G105, and sand/steel wheel test under wet/dry conditions (ASTM B611). A concept of integrating more than one tribo-technique at different contact mechanisms (line or area) working simultaneously under same test condition against same material is introduced in a current designed machine. Different wear modes (adhesive, two-body-abrasive, three-body-abrasive, under dry, lubricated, or slurry conditions) can be conducted on the same machine. Results of adhesive wear, friction and interface temperature of glass fibre reinforced polyester composite under wet/dry contact condition are reported at 50 N load for different sliding speeds (2.8–7.8 m/s) using the new machine. Weight loss and friction coefficient of the composite were substantially influenced by introducing water as lubricant. Additionally, the contact condition has the high influence key on the wear and frictional performance of the composite.     

Mineral phases of weathered and recent electric arc furnace dust

A weathered and a recent sample of electric arc furnace dust (EAFD), generated in a southern Brazilian steel industry, were characterized by X-ray fluorescence spectroscopy (XFA), powder X-ray diffraction (XRD), thermogravimetric analysis (TG), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) probe and Fourier transform infrared spectroscopy (FTIR). A quantitative phase composition model, that accounts for the observed data and for the physico-chemical conditions of formation, was postulated for each material. One sample, in the form of a wet paste, was collected from the lowest part of a landfill and corresponds to a weathered material whereas the other sample was collected from the top portion of the landfill and corresponds to a recently produced material. The dominant cations present in both samples are iron, zinc and lead with minor amounts of manganese, calcium and silicon. The dominant mineralogical phases identified in both materials are Magnetite, Franklinite and Zincite. The recent sample has Laurionite whereas the weathered sample has Hydrocerussite and Hydrozincite.     

Cobalt-based orthopaedic alloys: Relationship between forming route,microstructure and tribological performance

The average longevity of hip replacement devices is approximately 10–15 years, which generally depends on many factors. But for younger generation patients this would mean that revisions may be required at some stage in order to maintain functional activity. Therefore, research is required to increase the longevity to around 25–30 years; a target that was initially set by John Charnley. The main issues related to metal-on-metal (MoM) hip replacement devices are the high wear rates when malpositioned and the release of metallic ions into the blood stream and surrounding tissues. Work is required to reduce the wear rates and limit the amount of metallic ions being leached out of the current MoM materials, to be able to produce an ideal hip replacement material. The most commonly used MoM material is the cobalt-based alloys, more specifically ASTM F75, due to their excellent wear and corrosion resistance. They are either fabricated using the cast or wrought method, however powder processing of these alloys has been shown to improve the properties. One powder processing technique used is spark plasma sintering, which utilises electric current Joule heating to produce high heating rates to sinter powders to form an alloy. Two conventionally manufactured alloys (ASTM F75 and ASTM F1537) and a spark plasma sintered (SPS) alloy were evaluated for their microstructure, hardness, tribological performance and the release of metallic content. The SPS alloy with oxides and not carbides in its microstructure had the higher hardness, which resulted in the lowest wear and friction coefficient, with lower amounts of chromium and molybdenum detected from the wear debris compared to the ASTM F75 and ASTM F1537. In addition the wear debris size and size distribution of the SPS alloy generated were considerably small, indicating a material that exhibits excellent performance and more favourable compared to the current conventional cobalt based alloys used in orthopaedics.     

Development, validation, and application of a method for quantification of methylmercury in biological marine materials using gas chromatography atomic emission detection

A gas chromatographic method was developed for the quantification of alkylmercury species using microwave-induced plasma atomic emission detection (GC-AED). The column conditioning and analyte derivatization required for previous methods were found to be unnecessary for stable, accurate, and sensitive element-specific detection using GC-AED. Chromatographic and detection parameters such as stationary phase type, stationary phase film thickness, GC column dimensions, helium mobile phase column head pressure, detector makeup gas flow rate, and detector reagent gas type and flow rate were found to significantly affect analyte response. The detection limit for the optimized GC-AED conditions was 0.8 pg (0.1 pg/s) of methylmercury chloride (as mercury). A solid-liquid extraction procedure with preparative gel permeation chromatography cleanup and GC-AED analysis was used to quantify methylmercury in a variety of complex matrix marine materials. The methylmercury quantification method was validated with four marine certified reference materials (CRMs). The method was then applied to 13 standard reference materials, CRMs, and control materials for which no certified reference values for methylmercury have been determined. Four National Institute of Standards and Technology Standard Reference Materials and one control material, which were analyzed using the GC-AED method, were also analyzed by two other laboratories using independent methods to further validate the method.     

基于GC-MS法测定纸质包装中4种二苯甲酮类物质

目的 利用气相色谱-质谱联用(GC-MS)法进行纸质包装中4种二苯甲酮类物质的测定.方法 优化超声提取纸质包装材料中二苯甲酮类光引发剂的方法,提取液使用GC-MS进行分析,采用全扫描和离子扫描方式确认每个物质的定性和定量离子.验证该方法的检出限、定量限、线性范围、相对标准偏差和回收率后用于实际样品的分析.结果 得到优化后的超声提取条件,乙腈作为提取溶剂,超声提取2次,每次提取时间为20 min.4种二苯甲酮类物质的检出限为0.01～0.05 mg/L,定量限为0.02～0.10 mg/L,标准添加实验的结果显示,相对标准偏差为2.0％～2.6％,回收率为98％～105％.结论 该方法检出限和定量限均较低,精密度和准确度较高,适合于实际纸质包装样品中4种二苯甲酮类物质的分析.     

Determination of methylmercury and butyltin compounds in marine biota and sediments using microwave-assisted acid extraction,solid-phase microextraction,and gas chromatography with microwave-induced plasma atomic emission spectrometric detection

A method is described for the determination of methylmercury and butyltin compounds in marine sediment and tissue using microwave-assisted acid extraction or digestion and solid-phase microextraction (SPME) followed by analysis using gas chromatography with microwave-induced plasma atomic emission spectrometric detection (GC-MIP-AES). Using the SPME-GC-MIP-AES method, enrichment factors for methylmercury and butyltin compounds of 50-100 were achieved, as compared to the typical hexane extraction, and measurements in marine tissue and sediment matrixes were possible at 1-2 microg/kg (methylmercury) and 10-100 ng/kg (butyltins). The SPME-GC-MIP-AES method was validated using several marine sediment and tissue matrix certified reference materials (CRMs) with certified values for methylmercury and butyltin compounds. The SPME-GC-MIP-AES method was used to measure methylmercury in four marine tissue CRMs ranging from oyster tissue at 13.0 +/- 1.0 microg/kg to fish tissue at 397 +/- 13 microg/kg (as Hg dry mass). Results from the SPME-GC-MIP-AES method were used in conjunction with results from other techniques to assign certified values for methylmercury in oyster, mussel, and fish tissue CRMs. Mono-, di-, and tributyltin were measured in three sediment CRMs at concentration levels of (0.08 +/- 0.03)-(0.35 +/- 0.05) mg/kg (as Sn dry mass).     

Properties of controlled low-strength material made using industrial waste incineration bottom ash and quarry dust

Industrial waste incineration bottom ash and quarry dust are waste materials which, if reused, will contribute to sustainability. One of the potential uses of these materials in bulk quantities is in controlled low-strength material (CLSM). This paper evaluates the properties of controlled low-strength material (CLSM) made using industrial waste incineration bottom ash and quarry dust. Various mix proportions of CLSM containing bottom ash and quarry dust were developed and the properties evaluated. Tests were performed on the CLSM in fresh and hardened states involving flowability, stability, setting time, segregation resistance, California bearing ratio (CBR), and corrosivity and the results discussed. Results indicated that the setting time of the CLSM mixtures tested ranged from 3.7 to 8 h, the fresh density from 1539 to 2100 kg/m³, strength values from 0.22 to 11.42 MPa, mixtures were stable and no corrosivity. It is shown that addition of quarry dust enhanced the performance of CLSM made using bottom ash with regard to stability, strength, and CBR and hence both the industrial waste incineration bottom ash and quarry dust are potential materials for use in CLSM.     

Comparison of ASE and SFE with Soxhlet, Sonication, and Methanolic Saponification Extractions for the Determination of Organic Micropollutants in Marine Particulate Matter

The methods of accelerated solvent extraction (ASE) and supercritical fluid extraction (SFE) of polycyclic aromatic hydrocarbons (PAHs), aliphatic hydrocarbons, and chlorinated hydrocarbons from marine samples were investigated. The results of extractions of a certified sediment and four samples of suspended particulate matter (SPM) were compared to classical Soxhlet (SOX), ultrasonication (USE), and methanolic saponification extraction (MSE) methods. The recovery data, including precision and systematic deviations of each method, were evaluated statistically. It was found that recoveries and precision of ASE and SFE compared well with the other methods investigated. Using SFE, the average recoveries of PAHs in three different samples ranged from 96 to 105%, for ASE the recoveries were in the range of 97-108% compared to the reference methods. Compared to the certified values of sediment HS-6, the average recoveries of SFE and ASE were 87 and 88%, most compounds being within the limits of confidence. Also, for alkanes the average recoveries by SFE and ASE were equal to the results obtained by SOX, USE, and MSE. In the case of SFE, the recoveries were in the range 93-115%, and ASE achieved recoveries of 94-107% as compared to the other methods. For ASE and SFE, the influence of water on the extraction efficiency was examined. While the natural water content of the SPM sample (56 wt %) led to insufficient recoveries in ASE and SFE, quantitative extractions were achieved in SFE after addition of anhydrous sodium sulfate to the sample. Finally, ASE was applied to SPM-loaded filter candles whereby a mixture of n-hexane/acetone as extraction solvent allowed the simultaneous determination of PAHs, alkanes, and chlorinated hydrocarbons.     

Mode-I fracture toughness testing of thick section FRP composites using the ESE(T) specimen

Experimental and numerical analyses are performed to determine the translayer mode-I fracture toughness of a thick-section fiber reinforced polymeric composite using the eccentrically loaded, single-edge-notch tension, ESE(T) specimen. Finite element analyses using the virtual crack closure technique were performed to assess the effect of material orthotropy on the mode-I stress intensity factors in the ESE(T) specimen. The stress intensity factors for the proposed ESE(T) geometry, are calculated as a function of the material orthotropic parameters. The formula is validated for a class of thick composite materials. The thick composite tested in this study is a pultruded composite material that consists of roving and continuous filament mat layers with E-glass fiber and polyester matrix materials. Data reduction from the fracture tests was performed using two methods based on existing metallic and composite ASTM [ASTM E 1922, Standard Test Method for Translaminar Fracture Toughness of Laminated Polymer Matrix Composites, Annual Book of ASTM Standards, 1997; ASTM E 399, Standard Test Method for Plane-Strain Fracture Toughness of Metallic Materials, Annual Book of ASTM Standards, 1997] fracture testing standards. Criteria for assessing test validity and for determining the critical load used in calculating the fracture toughness were examined. Crack growth measurements were performed to determine the amount of stable crack growth before reaching critical load. The load versus notch mouth opening displacement, for different crack length to width ratios is affected by material orthotropy, nonlinearity, and stable crack propagation. The mode-I translayer fracture toughness and response during crack growth is reported for ESE(T) specimen with roving layers oriented both, transverse and parallel to the loading direction.     

Determination of carbamate, urea, and thiourea pesticides and herbicides in water

Microbore liquid chromatography and positive ion electrospray mass spectrometry are applied to the determination of 16 carbamate, urea, and thiourea pesticides and herbicides in water. The electrospray mass spectra of the analytes were measured and are discussed and mobile-phase matrix effects were evaluated. Analyte positive ion abundances are generally inversely related to the concentration of acetic acid in the acetonitrile-water mobile phase in the range of 0.001-0.1% (v/v) acetic acid. Using an internal standard for quantitative analyses and no acid in the mobile phase, retention time precision, peak width precision, concentration measurement precision, mean recoveries, and instrument detection limits were determined in reagent water. The 16 analytes were also measured in fortified environmental water samples from a recreational lake, a groundwater well, a cistern, a farm pond, and drinking water. These measurements were at 5 ng/mL of each analyte, which is within the range expected for environmental pesticide and herbicide contaminants. The analytes were separated from the environmental water matrixes with an on-line extraction and concentration to provide rapid sample analyses without a slow off-line liquid-liquid or liquid-solid-liquid extraction and extract concentration. Recoveries of 12 of the analytes from 4 environmental water samples were in the range of 75-124% with relative standard deviations in the range of 11-16%.     

A study on the failure of pump casings made of ductile Ni-resist cast irons used in desalination plants

There have been cases of the corrosion failure of pressure parts of brine pumps in a desalination plant located on Arabian Gulf. The materials of the construction of failed parts are Ni-Resist Ductile Irons (NDI) and the environment is brine, which is concentrated seawater. Two brands of pumps had different lives to total failure; one lived 18 years while the other lasted only five years. The failed parts of former pumps were made out of NDI material as per ASTM A439 D2, whereas, the latter pumps were made out of NDI material as per BS 3468 S2W, which has better weldability. In this work, the material factor, as one of the possible factors that could have contributed to this different behavior has been evaluated. Metallurgical, mechanical and electrochemical tests were used to compare between the two alloys. Results have shown variations in the microstructure, tensile strength and hardness values of both alloys. However, electrochemical tests have shown similar corrosion rates between 0.20 and 0.25 mmpy in brine at room temperature, whereas, potentiodynamic sweeps have shown comparable Tafel plots.     

On the need to decompose fatigue strain signals associated to fatigue life assessment of the AISI 1045 carbon steel

The evaluation of a new statistical-based analysis is discussed in this paper, leading to the fatigue life assessment at three different applied stresses during the cyclic testing procedure. Fatigue tests were performed following the standard ASTM: E466-07. These tests involve a strain gauge being attached to the specimen. For this test, AISI 1045 carbon steel was used as material due to its wide application in automotive and machinery industries. Fatigue tests were performed at three different stress levels of 305 MPa, 325 MPa, and 345 MPa with the testing frequency of 8 Hz, and the strain signals were collected accordingly. The Integrated Kurtosis-based Algorithm for Z-filter (I-kaz) approach, which provides its coefficient and three dimensional graphics, was utilised to define a statistically-based fatigue behaviour pattern. The I-kaz technique was used to extract strain signal patterns at the respective low, medium, and high frequency ranges for each signal at specific applied testing stress level. Results showed that highest strain amplitude occur at the low frequency range, suggesting the capability of I-kaz to identify fatigue damage pattern of metallic materials using statistical representation.     

Durability of mixtures containing calcium nitrite based corrosion inhibitor

The influence of calcium nitrite based corrosion inhibitor on the corrosion of reinforcing steel embedded in 14 different mortars is experimentally investigated in this work. Two Portland cements, NPC and SR (type I and V according to ASTM Standards) and 12 blended cements were used. The pozzolanic materials used were three lignite fly ashes, silica fume and one natural pozzolan (Milos' Earth). All blended cements were produced in the laboratory by grinding Portland clinker, gypsum and the appropriate pozzolanic material. One commercially available blended cement (CEM II/A-M 32.5N) was also used in this research. Mortar specimens (cylinders 100 × 40 mm) were prepared, according to DIN 1164 with and without calcium nitrite and used for measurements of carbonation and chloride-induced corrosion for a time period of 2 years. Chloride resistance was monitored according to ASTM C876 on specimens immersed in a 5% NaCl solution after an initial curing of 28 days. The carbonation depth was measured on cylinders cured in a severe environment using a spray indicator enabling the estimation of different pH values.Results show that calcium nitrite has a beneficial effect in shifting the corrosion potential towards electropositive direction especially in the case of NPC and SR cements. The corrosion potential of blended mixtures was also shifted towards electropositive direction, but since the pozzolanic materials had a beneficial effect by themselves, the reduction was comparative smaller. The beneficial effect of calcium nitrite was also confirmed by the gravimetric weight loss measurements performed after 2 years of immersion in the 5% NaCl solution.Carbonation depth of all mixtures was reduced or remained the same when calcium nitrite was used. Chloride permeability was not seriously influenced by the addition of calcium nitrite, as it is indicated by the total chloride measurements performed after 2 years of immersion in the 5% NaCl solution.     

Chevronproben zur näherungsweisen Bestimmung der Bruchzähigkeit

Chevron Specimen for the Estimation of Fracture Toughness Fracture toughness is a material property which is presently used in many industrial areas, either as material selection criteria or as material quality requirement. In some areas, nuclear power plants and aerospace, it is also a design parameter for design against catastrophic failures. Determination of the fracture toughness in accordance with ASTM E 399 is relatively elaborate. Depending on the material concerned, a certain minimum material cross section is required to obtain the necessary size of the specimen. Many semi-finished product forms of the different materials can not be tested for fracture toughness due to the specimen size requirements. For these reasons, alternative test methods were sought of which testing of chevron-notched specimens is one method. In the work to be presented, the test method to determine fracture toughness via chevron-notched specimens is briefly described. The most frequently used chevron-notched specimens are shown together with loading grips to be used in conjunctions with universal testing machines. Certain effects associated with some of the chevronnotched specimens are pointed out which result in a large difference between the fracture toughness determined in accordance with ASTM E 399 and that obtained via chevron-notched specimens. The aim of our research effort is to develop a chevron-notched specimen geometry which furnishes fracture toughness values compatible with K_Ic values without complicating the test method. Such a chevronnotched specimen is presented and the fracture toughness values obtained from these specimens of 7475-T 7351 and different Ti-alloys are compared to the K_Ic values obtained in accordance with ASTM E 399 for the same materials.     

Accelerated solvent extraction (ASE) of environmental organic compounds in soils using a modified supercritical fluid extractor

Accelerated solvent extraction (ASE) has been applied to the quantitative extraction of a selected list of semi-volatiles, which include polycyclic aromatic hydrocarbons (PAHs), phenols, polychlorinated biphenyls (PCBs) and total petroleum hydrocarbons. Two conventional supercritical fluid extraction (SFE) systems, the Suprex Prep Master and SFE/50 systems have been modified to function as ASE systems. Using solvent instead of supercritical fluid, extraction in an enclosed system proceeded under high pressure and temperature. Parameters such as extraction temperature and effect of modifiers were investigated. Although limited by a 150 degrees C maximum oven temperature, effective extraction could be carried out in less than 25 min for all the compounds studied. The technique was applied to a variety of real matrices contaminated with hydrocarbons, PAHs and phenols. Validations of the technique were performed using standard reference materials. Recoveries for these matrices were good (>75%) and precision (R.S.D.) was generally less than 10%. Primarily a rapid field extraction technique, comparison with other rapid extraction such as sonication and microwave assisted extraction (MAP) were made. Recoveries were found to be comparable to MAP and superior to sonication. On the present ASE system, only sequential extraction can be carried out but given the rapid nature of the process, about 15 samples can be carried out in a working day.