Optimum Sample Volume Research Articles

Assessment of metals and anions in tap, river, wastewater, and sludge: comparison of hotplate- and microwave-assisted digestion

In this study, the analysis of metals in tap, river, wastewater, and sludge samples was conducted using ICP−OES after hotplate- or microwave-assisted digestion. Both digestion methods produced a good degree of accuracy, indicating their suitability for the analysis of the studied metals in water samples. From method development studies, 100 mL of HNO3 was found to be the optimum sample volume and acid type for digestion. The average concentrations obtained ranged from 4.9–410.8 µg/L, 5.9–465.0 µg/L, 3.6–425.4 µg/L, 16.1–647 µg/L and 9.7–784 µg/L in tap water, river, influent, effluent, and sludge samples, respectively. All metals were below their maximum permissible limits, with the exception of Mn in all sludge samples and Pb in all tap water, Umhlathuzana River, and Northern Works influent samples. Comparable recoveries and metal concentrations were obtained by microwave and hotplate methods, suggesting that the cheaper hotplate method can be used as an effective digestion method for daily analysis. Common anion concentrations obtained ranged from 0.03–23.5 mg/L, 0.02–3 064.67 mg/L, and 0.32–175.67 mg/L for tap, river, and wastewater samples, respectively. The anion concentrations were found to be below the maximum acceptable limits indicating no negative health effect on human and aquatic life, with the exception of Cl− and SO42− in Amanzimtoti and Northern River water, respectively.

Green Surfactant Assisted-Solidified Floating Organic Drop Micro-Extraction (SA-SFODME) for the Preconcentration of Trace Lead with Determination by Flame Atomic Absorption Spectrometry (FAAS)

Determination of trace lead from environmental samples was carried out by solidified floating organic drop microextraction for preconcentration before analysis by flame atomic absorption spectrometry. The determination of lead from environmental samples, even at trace levels, was possible with an ordinary flame atomic absorption spectrometer (FAAS). The lead formed a hydrophobic complex with the anionic surfactant sodium dodecyl benzene sulfonate (SDBS), and this hydrophobic complex was extracted into the 1-dodecanol drop. Parameters affecting analytical performance have been studied. The optimum pH value was 3.5. The optimum sample volume, SDBS concentration, and extraction solvent volume were 75 mL, 50 mM in dodecanol, and 75 µL, respectively. The optimum extraction time was determined as 30 min, the optimum extraction temperature was 45 °C, the optimum mixing speed was 650 rpm and the ideal extraction phase volume was 0.50 mL. Methanol has been shown to be effective when used as a diluent. Using the optimum conditions, the enhancement factor was 106, and the limit of detection (3s) and precision were 3.3 ng/mL and 2.3% (n = 9,15 ng/mL), respectively. The limit of quantification (LOQ) (10s) was 10 ng/mL and the linear working range was 15-100 ng/mL. The accuracy was evaluated by certified reference material analysis. The optimized method was applied to the determination of Pb(II) from environmental water samples. This method follows the principles of green analytical chemistry.

Chemometric Optimization of SPE for the Determination of Multiclass Pesticides in Portable Water Samples by UHPLC-MS/MS

This study aimed on the development of a SPE-UHPLC-MS/MS method for the simultaneous determination of pesticide residues in drinking water samples. A chemometric approach was applied to optimize the efficiency of the SPE pretreatment procedure. This study involved (i) the application of a Full Factorial Design for the screening of the significant factors, (ii) the application of a Central Composite Design for the determination of the optimal conditions and (iii) the evaluation and validation of the significance of the statistically proposed models. Oasis HLB cartridges were used for the extraction. The optimum sample volume was 300 mL and the elution solvent 3 mL of the mixture of methanol:ethylacetate 70:30 v/v. The method was validated according to the international guidelines. Recoveries were ranged from 63 to 116% and the detection limits were between 0.1 and 1.5 pg mL− 1. The validated method could be used in routine analysis for pesticides screening.

Effects of groundwater sample volume on identified microplastics in groundwater of an agricultural area in Korea

Groundwater serves various purposes worldwide, including agricultural, drinking, domestic, and industrial uses. In the Republic of Korea, groundwater is used primarily for agricultural purpose. Understanding the quality of groundwater is crucial because microplastics (MPs) can enter groundwater through agricultural activities and potentially pose harm to humans. Therefore, groundwater sampling plays a vital role in determining the presence of MPs. However, the optimal volume of groundwater sampling required for accurate MP assessment remains uncertain. This study examined the optimal sample size for collecting MPs from groundwater in the heavy agricultural area of the Haean Basin, Korea. Groundwater sampling and MP analyses were conducted during the wet and dry seasons of 2022. A total of 500 L of groundwater was continuously sampled in increments of 100 L to 500 L (100, 200, 300, 400, and 500 L). Additionally, we investigated the land use surrounding the sampling wells and the predominant types of plastics used in agriculture. To ensure reliable MP analysis, precautions were taken to minimize plastic contact during sampling, pretreatment, and μ-FTIR analysis. The concentration of MPs in groundwater ranged from 0.04 to 17.77 particles/L during the wet season and from 0 to 0.56 particles/L during the dry season. The highest concentration of MPs was observed at the first 100 L sample volume, with concentrations decreasing as the sampling volume increased. Fragmented particles accounted for 86.3 % during the wet season and 91.5 % during the dry season, whereas fibers constituted 13.7 and 8.5 %, respectively. MPs in the size range of 20–100 μm were predominant in both seasons. The polymers identified in both seasons were polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), and polyamide (PA). While some studies suggest that 500 L is the optimal sample volume for assessing MPs in groundwater, the findings of this study indicate that a larger sample volume may be necessary. This study was the first attempt to determine the optimum sample volume required to collect MPs from groundwater, emphasizing the importance of conducting further research to validate these findings.

Determination of organophosphorus pesticides based on graphene oxide aerogel solid phase extraction column

以氧化石墨烯气凝胶三维纳米材料作为固相萃取的吸附剂,结合高效液相色谱,对食品中的有机磷农药(辛硫磷、双硫磷、倍硫磷、杀螟硫磷)进行检测分析。首先,利用冷冻干燥的方式制备得到氧化石墨烯气凝胶,通过扫描电镜、红外光谱、比表面积吸附等一系列的实验手段对其形貌及物理特性进行了表征,证明其成功合成。从扫描电镜中可见石墨烯的层状褶皱结构,其表面积为740.51 m2/g。然后,将氧化石墨烯气凝胶直接填充于固相萃取柱中,在未借助任何硅胶等基体的条件下进行萃取研究;通过单因素实验,系统研究了萃取和洗脱条件对有机磷农药萃取回收率的影响。结果显示,在上样体积15 mL、样品溶液pH值4、上样速率1.0 mL/min、洗脱剂1.0 mL乙腈的条件下萃取回收率最高。与商用的萃取材料进行比较,包括碳十八硅胶柱(C18)、阴离子交换柱(SAX)、氨基柱(-NH2)和硅酸镁柱(Florisil),氧化石墨烯气凝胶填充的固相萃取柱的萃取回收率有明显提高。实验考察了氧化石墨烯气凝胶直接填充的萃取柱的寿命,结果显示该萃取柱可以重复使用15次,可见解决了分散无基体支撑的石墨烯纳米片容易破碎、堵塞筛板的问题。与液相色谱联用建立分析方法,4种有机磷农药的线性范围较宽,辛硫磷、双硫磷和倍硫磷的线性范围为1~200 μg/L,杀螟硫磷的线性范围为2~200 μg/L,线性拟合良好(线性相关系数r2≥0.9949),检出限为0.2~0.5 μg/L,满足于我国和其他国家限定标准的检测。将该方法应用于实际样品,在苹果皮中未检测到有机磷农药,对其进行加标,回收率为70.5%~93.6%,相对标准偏差≤10.4%。

Separation of injectable salidroside by column chromatography of macroporous resins for treating myocardial ischemia

The objective of the present study is to develop a method for large-scale separating and purifying salidroside from rhodiola kirilowii roots and for preparing injectable medicinal ingredient. Crude extract of salidroside was prepared by water-ethanol system, and purified by column chromatography of macroporous resins. Static adsorption and desorption studies were performed on six kinds of macroporous resins, and SP825 resin was chosen, followed by optimizing process parameters. The optimum sample volume, feed concentration, ratio of diameter to height, and feeding flow rate were 1.5 bed volumes (BV), 15 mg/mL, 1:10 and 1 BV/h, respectively. Dynamic desorption was performed consecutively with 8 BV of distilled water, 3 BV of 5% ethanol and 8 BV of 10% ethanol at a flow rate of 2 BV/h. After three cycles in separating 3.5 tons of rhodiola kirilowii roots, salidroside purity was increased from 3.4% in the crude extract to 93.6% in purified salidroside product. This study provides a novel method to separate salidroside for injectable use.

Optimising sample volume and replicates using the Bou-Rouch method for the rapid assessment of hyporheic fauna

Despite the widespread use of the Bou-Rouch method in obtaining hyporheic samples in ecological studies, problems persist in comparing data because of differences in volume and number of samples taken in various studies. Towards standardising this method, we conducted a study in the Delour River, Ireland, between March and September 2006. The hyporheic habitat was divided into three lateral zones: the flowing stream (SS); the stream–terrestrial ecotone (EC); and the terrestrial margin (TM). Between 3 and 6 random insertions of the stand pipe were made into the hyporheic habitat at 0.2 m and 0.5 m in each zone. Ten consecutive 1-L samples were pumped at each point to determine an optimum sample volume and replicates needed to estimate taxon richness and abundance. The optimum sample combinations range between 6 and 15 3- to 10-L samples depending on depth and habitat zone. Our results show that both spatial and temporal scales are important factors in considering the optimum combinations of sample volume and number of independent spatial replicates needed to sample stream hyporheos, with the zone closer to the flowing stream requiring many small-volume samples whereas areas further away towards the alluvial groundwater need larger volumes with small numbers of replicates.

Determining the Optimum Sample Volume for Environmental Airborne Radioactivity Monitoring

A methodology to determine the optimum air sample volume for environmental airborne radioactivity monitoring is described. For environmental airborne radioactivity measurements at the Hanford Site, the optimum sample volume was determined to be approximately 1,000 m3. At this volume the counting statistics advantage with increasing flow rate and sampling time levels off, and above this volume the potential for particulate fall-off from filters, alpha attenuation during gross radioactivity counting, and stress on the sampling pumps become limiting considerations.

A comparison of discrete and continuous sample introduction for flame atomic absorption spectrometry

The continuous aspiration and discrete volume sampling techniques in flame atomic absorption spectrometry were compared. Continuous sample introduction of a properly diluted sample can provide for lower absolute determination limits than the injection sampling technique for the same but pre-concentrated sample. In the analysis of a sample solution with a given absolute analyte amount there is an optimum dilution of the sample solution and an optimum sample volume to be taken for analysis, which ensures the most precise results. Theoretical assumptions were checked with the determination of iron in aqueous solutions.

Properties, in theory and practice, of novel gel filtration media for standard liquid chromatography

The influence of experimental parameters on the separation result in gel filtration may readily be predicted from a few basic equations, as demonstrated with the aid of experimental observations on Sephacryl ® HR. Excellent agreement between the predicted resolution and that determined experimentally was found for parameters such as temperature, particle size, column length, flow velocity, sample volume and gel porosity. The theoretical prediction of an optimum sample volume for a constant proceeding rate was also experimentally verified. An exhaustive investigation of the physical, chemical and functional properties of Sephacryl HR was undertaken to facilitate the interpretation of experimental observations.

Quantitative analysis of trace amounts of estrogenic steroids in pregnancy urine by column liquid-liquid chromatography with ultraviolet detection

The influence of the sample volume on peak height and resolution in elution column chromatography was studied. Graphs which enable the choice of the optimum sample volume are given. The quantitative analysis of estrogens by column liquid–liquid chromatography with ultraviolet detection was investigated. The method has been applied to the rapid quantitative determination of estriol in urine. After preparing the urine sample for chromatography, the quantitative information can be obtained in 20 min with a precision of 5″6 for a concentration of 3 mg l. The noise of the sample-free detector corresponds to 60 ng of estriol.

LengthenedH102cavity for electron spin resonance studies of aqueous samples

An H102 cavity, constructed from waveguide size 16 for use with an X-band electron spin resonance spectrometer, may be increased in length to 12 cm by reducing the larger waveguide side. This allows the use of a flat sample cell 1 mm thick which is easier to make and to align than the flat cells in normal length H102 cavities. If the empty cavity has been critically coupled, the minimum voltage standing wave ratio with a cell in position is obtained when the cell coincides with the electric field node. The voltage standing wave ratio in this case should be 1.5 for optimum sample volume.