Improvement Of Detection Power Research Articles

Determination of Silver in Metal Plating Wastewater by Slotted Quartz Tube Flame Atomic Absorption Spectrometry (SQT-FAAS) after Preconcentration with Stearic Acid-Coated Magnetite Nanoparticle-Based Solid-Phase Microextraction (SA-MNP-SPME)

Here is reported the determination of silver at ultratrace levels by slotted quartz tube-flame atomic absorption spectrometry (SQT-FAAS) following stearic acid coated magnetic nanoparticle based solid phase microextraction (SA-MNP-SPME). The parameters affecting silver extraction were optimized to obtain high efficiency. In addition to the magnetic property of iron oxide (Fe3O4) nanoparticles, they were coated with stearic acid to increase the surface area and the capacity for the analyte. An external magnetic field was used to separate the silver from the liquid phase. To obtain the highest efficiency, the mass of magnetic nanoparticles, pH and volume of buffer solution, mixing type and period, volume of eluent and volume of sample were optimized univariately. Under the optimum conditions, the limits of detection and quantitation were determined to be 40 and 130 ng L−1, respectively. Recovery experiments were performed to investigate matrix effects on the developed method by spiking real samples. Recoveries were between 96.3 and 105.1% with low standard deviations by the matrix matching calibration. The developed MNP-SPME-SQT-FAAS method achieved 305-fold improvement in detection power. These results demonstrated the method’s applicability for the determination of trace silver in complex samples with good accuracy and precision.

A Simple and Efficient Extraction Method for the Preconcentration of Copper in Tap Water and Linden Tea Samples Prior to FAAS Measurement

AbstractIn this study, a simple, low‐cost and eco‐friendly analytical method namely syringe assisted pipette tip dispersive solid phase extraction (SA‐PT‐DSPE) combined with slotted quartz tube‐flame atomic absorption spectrometry (SQT‐FAAS) system was presented for the determination of copper at trace levels in linden tea and tap water samples. Under the optimal experimental conditions, limit of detection (LOD) and quantification (LOQ) values obtained for the SA‐PT‐DSPE‐SQT‐FAAS system were calculated as 3.7 and 12.5 μg/L, respectively. The SA‐PT‐DSPE‐SQT‐FAAS system provided a 44.0‐folds improvement in detection power of the conventional FAAS. The recovery results for tap water samples were calculated close to 100 % via external calibration strategy. Negative matrix effects on the analyte were observed for linden tea samples. Therefore, recovery studies were performed by matrix matching calibration strategy and percentage recoveries were found to be between 88.0–102.0 % with low standard deviation values.

Development of sensitive analytical methods for the determination of thallium at trace levels by slotted quartz tube flame atomic absorption spectrometry

A simple, sensitive and economical technique is needed for the determination of thallium and this study demonstrates the different analytical strategies were developed using atomic absorption spectrometry (AAS). In order to improve the sensitivity of flame atomic absorption spectrometry (FAAS), a basic slotted quartz tube (SQT) was used for the thallium determination. In the first strategy, mixing propanol (100 μL) and Tl standard solution (500 μL) under the optimum conditions, namely solvent assisted SQT-FAAS, provided 4.49 folds enhancement in detection power with the help of better nebulization efficiency and/or atomization of analytes. Furthermore, SQT was used as an atom trap, AT as the second strategy. In this method, analyte atoms were trapped for 5.0 min on the SQT inner surface under the lean flame. In addition, a novel analytical method was developed using an inner surface coated SQT with metals with low volatility (palladium, tungsten, molybdenum, zirconium, tantalum, osmium and titanium). Under the all optimum conditions, limit of detection values were found to be 38 ng mL−1 and 3.5 ng mL−1 for SQT-AT-FAAS and Os-Coated-SQT-AT-FAAS methods, respectively. 319 folds improvement in detection power was obtained by Os-Coated-SQT-AT-FAAS method with respect to conventional FAAS.

Multiobjective design of an S control chart for monitoring process variability

Optimally determining parameters of the control chart is a critical task for control chart designer to improve the processes. However, difficulty in an accurate estimation of various cost and process parameters is one of the barriers while someone desire to determine these parameters by means of economic approach. In order to reduce cost penalties for not knowing the true values of the parameters and to study the impact of further improvement in detection power of the chart on the economic performance of the S control chart, this paper aims to develop a multiobjective model of the economic-statistical design of the S control chart to minimise the mean hourly loss cost as well as minimising average time to signal and maintaining reasonable in-control average run length. We show that the proposed model gives more practical outcomes in comparison with the existing economic design models.

Ultra-trace determination of beryllium in occupational hygiene samples by ammonium bifluoride extraction and fluorescence detection using hydroxybenzoquinoline sulfonate

A highly sensitive molecular fluorescence method for measuring ultra-trace levels of beryllium has been previously described. The method entails extraction of beryllium workplace samples by 1% ammonium bifluoride (NH 4HF 2, aqueous), followed by fluorescence detection using hydroxybenzoquinoline sulfonate (HBQS). In this work, modification of the existing procedure resulted in a significant improvement in detection power, thereby enabling ultra-trace determination of beryllium in air filter and surface wipe samples. Such low detection limits may be necessary in view of expected decreases in applicable occupational exposure limits (OELs) for beryllium. Attributes of the modified NH 4HF 2 extraction/HBQS fluorescence method include method detection limits (MDLs) of <0.8 ng to ≈2 ng Be per sample (depending on the fluorometer used), quantitative recoveries from beryllium oxide, a dynamic range of several orders of magnitude, and freedom from interferences. Other key advantages of the technique are field portability, relatively low cost, and high sample throughput. The method performance compares favorably with that of inductively coupled plasma-mass spectrometry (ICP-MS).

Determination of Cd and Pb at μg/L levels by HHPN-beam injection flame furnace-AAS

Flame-heated tubes are widespread in flame-AAS, mainly for the determination of hydride-forming elements. Instead of the introduction of gaseous compounds liquids can also be introduced continuously in such an absorption cell. With the aid of an HPLC pump the liquid is forced through a very fine nozzle, generating an aerosol beam less than 0.5 mm in diameter. This beam travels a distance of 10cm as a "free-flying aerosol jet" into the sample introduction hole of a metal tube furnace placed in the flame. Both introduction of the entire sample and the long residence time lead to a considerable improvement in power of detection. The detection limit for 100 microL samples amounts to 7 microg/L (Pb) and to 0.2 microg/L (Cd), which means an increase in power of detection of between one and two orders of magnitude compared to conventional flame-AAS. The relative standard deviation (100 microL sample volume, N = 10) was found to be 1.3% (signal area) for 600 microg/L Pb and to be 1.5% (signal-area) for 15 microg/L Cd. RSD values from measurements in peak-height amounted to 2.2% (Pb) and to 1.7% (Cd).

Beam injection flame furnace atomic absorption spectrometry: a new flame method.

A new flame method of atomic absorption spectrometry is described. The liquid sample to be analyzed is transported as a high-speed liquid jet into a heated tube which is positioned in an air/acetylene flame. The jet is generated by means of an HPLC pump which feeds a smooth jet nozzle having a diameter of 50 microns or smaller. After traveling a distance of 10 cm, the liquid jet enters a small sample introduction hole, impacts onto the opposite inner wall of the tube furnace, and immediately vaporizes (jet impact vaporization, JIV). Both the complete introduction of the entire sample and the extended residence time inside the absorption volume result in an improvement in power of detection from 6- to 202-fold for 17 elements (Ag, As, Au, Bi, Cd, Cu, Hg, In, K, Pb, Pd, Rb, Sb, Se, Te, Tl, Zn). A standard deviation of 1.7-4.0% (n = 12, 50 microL) was achieved. Sample volumes between 10 microL and 1 mL have been investigated. For 50 microL sample volumes, the sampling frequency is 4/min. The new method can also be considered a simple, effective interface between HPLC and flame AAS.

Arsenic determination in the ultratrace range by atomic absorption spectrometry after preconcentration of the hydride

A method for the determination of extremely low levels of arsenic by hydride AAS is presented. It is based on hydride preconcentration in a quartz tube at liquid nitrogen temperatures under carefully evaluated and optimized experimental conditions, followed by rapid heating up to 100° C and measurement in a heated quartz cell. Under the given experimental conditions an absolute detection limit of 0.05 ng and a linear range up to 6 ng could be achieved, representing a 6.5-fold improvement of detection power in comparison to commercially available hydride systems.