Ml-1 Level Research Articles

EFFECT OF SOME HERBICIDES ON SORGHUM SEEDLING CHARACTERS, WEED CONTROL AND SEED BORNE FUNGI

Two field experiments were conducted at Sakha Agriculture Research Station, Agriculture Research Center, Kafr El-sheikh Governorate, Egypt during 2012 and 2013 seasons to determine the effect of some herbicides on seedlings characters and its reflection on plant growth and yield of sorghum. Each experiment included seven treatments in a complete randomized block design. Results revealed that five herbicides i.e. acetochlor at 900 g a.i/fed (Vern 90% EC), acetochlor at 840 g a.i/fed (Harness 84% EC), pendimthalin at 773.5 g a.i./fed (Stomp Extra 45.5% CS), butralin at 1200 g a.i./fed (Amex 48% EC) and metribuzin at 210 g a.i./fed (Metribuzin El-Nasr 70% WG) increased germination percentage and seedlings growth of sorghum. These herbicides gave satisfactory effect in controlling both annual broadleaf and grassy weeds and had wide spectrum for controlling weed species grown with sorghum plants at more than 80 % which reflected on increasing plant growth and yield, and was superior than hand hoeing (twice) during the two growing seasons. Therefore, such herbicides can be applied in sorghum field. The above mentioned herbicides at 0, 1000 and 2000 μg ml-1 were used to treat sorghum grains after harvest. The results showed also that acetochlor at 900 g a.i./fed (Vern 90%), acetochlor at 840 g a.i./fed (Harness 84%), pendimethalin at 773.5 g a.i./fed (Stomp Extra 45.5%) at 2000 μg ml-1 level, were very effective in inhibiting the growth of grain-born fungi.

Atropisomeric determination of chiral hydroxylated metabolites of polychlorinated biphenyls using HPLC-MS

BackgroundPolychlorinated biphenyls (PCBs) are a group of environmental persistent organic pollutants, which can be metabolized into a series of metabolites, including hydroxylated metabolites (OH-PCBs) in biota. Nineteen of 209 PCB congeners can form chiral stable isomers. However, atropisomeric determination of the hydroxylated metabolites of these chiral PCBs has never been reported by LC methods. In this work, a novel HPLC-MS method was developed to detect five chiral OH-PCBs (4OH-PCB91, 5OH-PCB91, 4OH-PCB95, 5OH-PCB95 and 5OH-PCB149) using HPLC-MS without a derivatization step.ResultsThe influences of column-type, column temperature, flow rate and ratio of the mobile phase on the atropisomeric separation were investigated in detail. In the final method, calibration curves, based on peak areas against concentration, were linear in a range of 1–100 ng mL-1 of five chiral OH-PCBs with correlation coefficients ranging from 0.9996 to 0.9999 for all atropisomers of OH-PCBs. The relative standard deviations measured at the 10.0 ng mL-1 level for atropisomers of five chiral OH-PCBs were in the range of 0.60-7.55% (n = 5). Calculated detection limits (S/N = 3) of five chiral OH-PCBs were between 0.31 and 0.60 ng mL-1 for all OH-PCB atropisomers.ConclusionThis HPLC-MS method was developed to detect chiral OH-PCBs and further successfully applied to measure OH-PCB atropisomer levels and enantiomeric fractions (EFs) in rat liver microsomal samples. The results from LC-MS method were highly consistent with those from GC-ECD method. It is the first time to report these OH-PCB atropisomers detected in microsomes by HPLC-MS. The proposed method might be applied also to detect chiral OH-PCBs in environmental samples and for metabolites of PCBs in vivo.

A study on the solid phase extraction of CO(II)-IIDE chelate with C18 disk and its application to the determination of trace cobalt

A sensitive, selective and rapid method has been developed for the determination of µg l-1 level of cobalt based on the rapid reaction of cobalt(II) with isopropyl 2-[(isopropoxy carbothioyl) disulfanyl] ethanethioate chelate (IIDE) and the solid phase extraction (SPE) of the colored chelate with Waters Porapak Sep-Park C18 disk. The isopropyl 2-[(isopropoxy carbothioyl) disulfanyl]ethanethioate chelate can react with Co(II) in the presence of pH 4.2 acetic acid /sodium acetate buffer solution and cetyl trimethylammonium bromide (CTMAB) medium to form a violet chelate of a molar ratio of 1:2 (cobalt to Isopropyl 2-[(isopropoxy carbothioyl) disulfanyl]ethanethioate chelate. This chelate can be retained on Waters Porapak Sep-Park C18 disk quantitatively when they passed the disk as aqueous solution. At the end of the enrichment, the retained chelate can be eluted from the disk by 2.5 ml of ethanol (contain 5% acetic acid). In the measured solution, the molar absorptivity of the chelate was 1.58 ×/105 1 mol -1 cm-1at 635 nm, and Beer’s law was obeyed in the range of 0.01-/0.4 µg ml-1. The relative standard deviation for 11 replicate sample of 0.01 µg.ml-1 level was 2.54%. The detection limit was 0.01 µg ml-1 (in original samples). This method can be applied for the determination of µg ml-1 level of cobalt in drinking water with satisfactory results. Key words: Cobalt, solid phase extraction spectrophotometry, isopropyl 2-[(isopropoxy carbothioyl) disulfanyl] ethanethioate chelate (IIDE).

Voltammetric determination of the neonicotinoid insecticide thiamethoxam using a tricresyl phosphate-based carbon paste electrode

The objective of the work was to investigate the possibility of using a tricresyl phosphate-based carbon paste electrode for the direct voltammetric determination of the neonicotinoid insecticide thiamethoxam. The analyte was determined by differential pulse voltammetry in Britton-Robinson buffer pH 7.0 in the concentration range of 3.72 - 41.5 ?g mL-1. The reproducibility of the analytical signal at the 7.29 ?g mL-1 level was characterized by a relative standard deviation of 1.3 %. The applicability of the developed method was evaluated by determining thiamethoxam in a river water sample and a commercial formulation Actara 25 WG.

Surface Plasmon Resonance (SPR) based Immunosensor for Sensitive Detection of Thyroxine

Surface plasmon resonance (SPR) based immunosensor for rapid and sensitive determination of thyroxine (T4), which is one of major thyroid hormones, has been investigated. Here, a mixed self-assembled monolayer (SAM) of poly(ethylene) glycols (PEG) aromatic dialkanethiols was employed for fabricating sensor surface. As a methodology for low-molecular-weight (lmw) compounds, indirect inhibition that assures the detection of lmw analytes was used for sensitive detection of T4. With these methodologies, T4 could be detected down to 1 ppb (ng ml-1) level with the present SAM-based SPR immunosensor.

Hyphenating Multisyringe Flow Injection Lab-on-Valve Analysis with Atomic Fluorescence Spectrometry for On-Line Bead Injection Preconcentration and Determination of Trace Levels of Hydride-Forming Elements in Environmental Samples

In this work the third generation of flow injection analysis, that is, the so-called micro-lab-on-valve (microLOV) approach, is proposed for the first time for the separation, preconcentration, and monitoring of metalloids as hyphenated with atomic fluorescence spectrometry (AFS). This was made feasible by interfacing the micromachined LOV-module with AFS by a multisyringe flowing stream network for on-line postcolumn derivatization of the eluate aimed at generation of hydride species. The potential of this new hyphenated technique for environmental assays was ascertained via determination of ultratrace level concentrations of total inorganic arsenic in freshwater. Employing quantitative preoxidation of As(III) to As(V) in the samples by means of permanganate, the method involves preconcentration of arsenate at pH 10 on a renewable anion exchanger, namely, Q-Sepharose, packed in a LOV microcolumn. The analyte species is afterward stripped out and concurrently prereduced by a 300 microL eluent plug containing 6 mol L(-)1 HCl and 10% KI. The eluate is downstream merged with a metered volume of sodium tetrahydroborate (0.3% w/v) for generation of arsine, which is subsequently quantified by AFS. The flow system facilitates on-column reduction of the retained arsenic with no need for application of programmable stopped flow. Yet, the high concentration of reductant and extreme pH conditions for elution hinder the sorbent to be reused due to gradual deactivation of the functional moieties, so that maximum benefit can be taken from the application of the bead renewable strategy. The proposed procedure is characterized by a high tolerance to metal species and interfering hydride-forming elements. In fact, ratios of Se(IV) to As < or = 5000 and Sb(V) to As < or = 500 are tolerated at the 10% interference level. Under the optimized experimental conditions, a detection limit (3sigma) of 0.02 ng mL(-1) As, a dynamic linear range of 0.05-2.0 ng mL(-1) As (by tailoring the AFS gain), an enrichment factor of 8.8 for arsenate, and a precision better than 6.0% at the 0.1 ng mL-1 level were obtained for the bead-injection mode whenever the loading sample volume was affixed at 3.0 mL. The reliability and accuracy of the automated procedure was ascertained by determining total inorganic arsenic in both spiked environmental waters and certified reference materials of variable matrix complexity (TMDA-54.3 and ERM-CA010) at the low ng mL(-1) level. No significant differences were found between the experimental results and the certified values at a significance level of 0.05.

Solid phase extraction and spectrophotometric determination of mercury in tobacco and tobacco additives with 5-(p-aminobenzylidene)-thiothiorhodanine

A highly sensitive, selective and rapid method for the determination of mercury based on the rapid reaction of mercury(II) with 5-(p-aminobenzylidene)-thiorhodanine (ABTR) and the solid phase extraction of the colored chelate with C18 disks has been developed. At pH 3.5 and in the presence of emulsifier-OP medium, ABTR reacts with mercury(II) to form a red chelate of a 1:2 (mercury to ABTR) molar ratio. This chelate was enriched by solid phase extraction with C18 disks and the retained chelate eluted form the disks with dimethyl formamide (DMF). An enrichment factor of 50 was achieved. In the DMF medium, the molar absorptivity of the chelate is 1.21´105 L mol-1 cm-1 at 545 nm, and Beer's law is obeyed in the 0.01~3 µg mL-1 range in the measured solution. The relative standard deviation for eleven sample replicate measurements at the 0.01 µg mL-1 level is 1.7%. This method was applied to the determination of mercury in tobacco and tobacco additives and good preconcentration was found between proposed and comparative methods results.

A new analytical procedure for assay of lysozyme in human tear and saliva with immobilized reagents in flow injection chemiluminescence system.

A novel analytical procedure based on chemiluminescence (CL) detection was described for the determination of lysozyme at ng ml(-1) level by using controlled-reagent-release technology in a flow injection system. The analytical reagents involved in the CL reaction, including luminol and periodate, were both immobilized on the anion-exchange resins in the flow injection system. Through water injection, luminol and periodate were eluted from the anion-exchange column to generate the chemiluminescence, which was inhibited in the presence of lysozyme. By measuring the decrease of CL intensity, one could analyze the lysozyme quantitatively. The decrement of CL emission was linear over the logarithm of lysozyme concentration in the range of 30-1000 ng ml(-1). A typical analytical procedure, including sampling and washing, could be performed in 0.5 min at a flow rate of 2.0 ml min(-1), giving a throughput of 120 h(-1), with a relative standard deviation of less than 3.0%. The proposed method was applied successfully to the determination of lysozyme in human tear and saliva samples, and the recovery was from 92.0% to 105.7%.

Electrochemical reduction and cathodic stripping voltammetric determination of clotrimazole

The reduction of clotrimazole at a mercury electrode, in phosphate buffer, pH>6, involves a reversible one-electron process. The electrochemical process presents a large contribution from adsorption effects. For the differential pulse polarographic determination the addition of Triton X-100 is recommended. Clotrimazole can be determined by cathodic stripping voltammetry at 50 ng mL-1 level when pre-accumulated for 3 min at an accumulation potential of -0.20 V. The proposed method is applied successfully for the determination of clotrimazole in a commercial formulation.

Rapid detection of Staphylococcus aureus using bioluminescent enzyme immunoassay.

A bioluminescent enzyme immunoassay (BLEIA) method for detecting protein A-bearing Staphylococcus aureus was developed using biotinylated firefly luciferase. The BLEIA was able to detect protein A at one pg ml-1 and 103 cfu ml-1 level of Staph. aureus. The BLEIA showed significant signals with overnight cultures of all 24 Staph. aureus strains, and the BLEIA did not show any significant signals with overnight cultures of all 44 strains of coagulase-negative staphylococci and the other genus bacteria. After 5 h cultivation beginning at approximately 50 cfu ml-1, the BLEIA was able to detect all 35 Staph. aureus strains isolated from healthy humans.

Determination of thyreostatics in animal feed by micellar electrokinetic chromatography.

The determination of the thyreostatics 2-thiouracil, its derivatives (4-methyl-2-thiouracil, 4-propyl-2-thiouracil and 4-phenyl-2-thiouracil) and methimazole in manufactured dried animal feed by micellar electrokinetic chromatography (MEKC) is described. A 99 +/- 5% extraction yield at the 20 micrograms g-1 level (n = 8) was achieved by shaking the milled fodder with methanol-1 M NaOH (80 + 20). Aliquots of the supernatant were injected in a 75 microns x 33.5 cm uncoated silica capillary using pressure; separation was performed at 23 degrees C with 15 kV (positive polarity) in a background electrolyte (BGE) containing 40 mM sodium dihydrogenphosphate, 50 mM sodium dodecyl sulfate and 15 mM Tween 20 at pH 9. When the surfactants were added to the BGE, all the thyreostatics were well resolved and the fodder extracts showed lower backgrounds. The peaks appeared within the 2.25-5.2 min range with efficiencies in the 2.5 x 10(4)-8 x 10(4) range; methimazole appeared in the vicinity of the electroosmotic migration time. Calibration curves were linear within the studied range (20-200 micrograms ml-1, r2 > 0.998). Limits of detection in the extracts of spiked fodder samples ranged from 0.25 to 0.4 microgram ml-1, which corresponded to 0.6-1.0 microgram of drug per gram of fodder. Peak area repeatabilities were about 4% at the 20 micrograms ml-1 level.

Enhanced recovery of chlorophenols from surface waters using polymer based extraction cartridges

The effectiveness of a new polymer based solid phase extraction cartridge (SDB 1) to recover phenolic compounds from aqueous samples has been evaluated by comparison of performance against conventional silica based cartridges. The polymer based material is found to be much more retentive, requiring a larger volume of solvent to achieve maximum recovery. Recovery efficiency is enhanced if the recovery solvent (methanol) is acidified to 0.1% with trifluoroacetic acid. The optimised extraction procedure has been applied to surface water samples and yields quantitative recovery at the 10 ng ml-1 level of all nine phenols studied.

Room-temperature phosphorimetric method for the determination of the drug naphazoline in pharmaceutical preparations.

A selective and sensitive micelle-stabilized room-temperature phosphorimetric (MS-RTP) method for the determination of naphazoline in pharmaceutical preparations is described. The method is based on obtaining a phosphorescence signal from naphazoline using a micellar agent (sodium dodecyl sulfate), a heavy atom salt (TINO3) and a deoxygenation agent (Na2SO3). Optimization of the various conditions permitted the establishment of an MS-RTP method for naphazoline determination with a detection limit of 64.2 ng ml-1 and a relative standard deviation of 3.74% at the 500 ng ml-1 level. The method was applied to the analysis of pharmaceutical preparations.

Determinação de elementos-traço: relatório de dois exercícios interlaboratoriais

Results of two intercomparison exercises are reported. In the first one, the participants were asked to determine Cd, Cu, Pb and Zn, at the sub mg mL-1 level, in an acidified aqueous solution. In the second one, the participants were asked to determine mercury (total) in two homogeneous biological samples, hair and fish. The exercises were considered satisfactory and few reported results were discharged (3s criteria).

Determination of traces of uranium and thorium in (Ba, Sr) TiO3 ferroelectrics by inductively coupled plasma mass spectrometry

Traces of uranium and thorium in barium(II), strontium(II) titanate ((Ba, Sr)TiO3) ferroelectric materials were determined by inductively coupled plasma mass spectrometry (ICP-MS). Samples were completely dissolved by a mixture of 1.4% H2O2 and 1.0 mol⋅l-1 HNO3. For a complete separation of the analytes from the matrix elements, a two step separation technique involving leaching and anion-exchange was applied. By the leaching step with HNO3 more than 90% of the matrix can be removed whereas the analytes completely remained in the solution. The anion-exchange step was carried out on a BIO⋅RAD AG1-X8 column with a mixture of 1.0 mol⋅l-1 HF and 0.5 mol⋅l-1 HNO3 as eluent. The content of uranium and thorium was subsequently measured by ICP-MS. The detection limits (D.L.) obtained were 0.043 ng g-1 and 0.035 ng g-1 for U and Th, respectively. The reproducibility was satisfactory with a relative standard deviation of less than 3% (at the 1 ng g-1 level, n=5). The matrix concentrations in the final solution were reduced to the sub-μg ml-1 level which is in the range of the detection limits of USN-ICP-AES (ultrasonic nebulization-ICP-atomic emission spectroscopy). The method was successfully applied to the determination of uranium and thorium in three synthetic (Ba, Sr)TiO3 samples spiked with the analytes at levels of 1, 5 and 10 ng g-1 and three (Ba, Sr)TiO3 ferroelectric samples containing sub-ng g-1 levels of the analytes.

Flow injection photometric determination of zinc and copper with zincon based on the variation of the stability of the complexes with pH.

A flow injection photometric method for the sequential determination of zinc and copper in mixtures was developed based on the variation of the stability of the chromogenic complexes between the analytes and the reagent zincon with pH. At pH 5.0 only the Cu-zincon complex exists, whereas at pH 9.0 the copper and zinc chelates co-exist. A three-channel manifold was implemented containing two alternating buffer streams (pH 5 and 9) which permit the colored reaction products to be formed sequentially at both pH values, and consequently the mixtures can be resolved. A continuous preconcentration unit (Chelex-100) was used in order to increase the sensitivity of the method, thus allowing the analysis of water samples in which the analytes are present at the ng ml-1 level. On the other hand, preconcentration was not required when the analytes were determined in brass. Under the optimum conditions and using a preconcentration time of 2 min, the detection limits (3 sigma) were found to be 0.35 and 0.80 ng ml-1 for zinc and copper, respectively. The repeatability of the method, expressed as the RSD, was in all instances less than 3.1%. Considering the sequential determination of both species, a sampling rate of 70 h-1 was obtained if preconcentration of the samples was not required.

Immunomagnetic separation of Erwinia carotovora subsp. atroseptica from potato peel extracts to improve detection sensitivity on a crystal violet pectate medium or by PCR

Immunomagnetic separation (IMS) procedures for the selective separation of Erwinia carotovora subsp. atroseptica from potato peel extract were optimized for the recovery of target and removal of non-target bacteria. A streptomycin-resistant strain of Erw. carotovora subsp. atroseptica was used in combination with a crystal violet pectate (CVP) medium supplemented with 100 micrograms ml-1 of streptomycin to determine the recovery level of the target bacterium. Recovery obtained with a polyclonal antiserum against Erw. carotovora subsp. atroseptica at a concentration of 6 micrograms IgG ml-1 was greater than that obtained with two monoclonal antibodies against lipopolysaccharides of Erw. carotovora subsp. atroseptica at a concentration of 10 micrograms IgG ml-1. A linear relationship was found between particle concentration ranging from 12 to 200 micrograms ml-1 and recovery level. When the Advanced Magnetics (AM) protein A and anti-rabbit IgG particles in the AM separation system and the Dynal anti-rabbit IgG particles in the Dynal separation system were examined, the highest recovery level per microgram of particles (66%) was obtained with the Advanced Magnetics protein A particles, followed by AM anti-rabbit particles (37%). Without IMS, detection of Erw. carotovora subsp. atroseptica in tuber peel extracts on a CVP-medium without streptomycin was impossible when the ratio of Erw. carotovora subsp. carotovora to Erw. carotovora subsp. atroseptica was greater than 100 or when large numbers of other saprophytic bacteria were present, because of overcrowding. IMS, using the AM anti-rabbit IgG particles, ensured that Erw. carotovora subsp. atroseptica could be enumerated in tuber peel extract consistently, to a detection level of 100 cells ml-1. Similarly, the IMS procedure lowered the detection level of Erw. carotovora subsp. atroseptica in a twofold diluted peel extract by PCR to ca 2.0 x 10(3) cells ml-1 or 50 cells per reaction tube. In contrast, positive results in PCR without IMS were obtained only when the peel extract was diluted 100 times and when the concentration of Erw. carotovora subsp. atroseptica was at least 10(5) cell ml-1.

Direct Determination of Zinc in Human Serum by Flow-Injection Spectrophotometric Analysis

Flow-injection spectrophotometric analysis has been established for the determination of zinc at 1μg ml-1 level in serum using 5-Br-PAPS(2-(5-bromo-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol, disodium salt) as a chromogenic reagent. A 100μl portion of serum is directly injected into the carrier stream containing 5%(v/v) TMAH (tetramethylammonium hydroxide) and 0.5M trisodium citrate. After mixing with 0.01%(w/v) 5-Br-PAPS-0.5M ammonium acetate-7.2×10-3M salicylaldehyde oxime-1%(v/v) Triton X-100-0.5M hydrochloric acid solution, the absorbance of Zn-5-Br-PAPS complex is measured at 560nm. The proposed flow-injection system is fully controlled with a personal computer and permits 60 samples to be measured per hour. The relative standard deviation (n=50) for 1.2μgZn ml-1 solution is 3.3%.

Cathodic Stripping Voltammetry of Sulfide with a Silver Disk Electrode

Direct current (DC) and differential pulse (DP) stripping voltammograms of sulfide at the low ng ml-1 level in 0.2 M sodium hydroxide solutions with a silver electrode have several peaks, all of which should be considered for quantification. The sum of the heights of all the stripping peaks is proportional to the sulfide concentration in the DP mode, but is not so in the DC mode. When the peak-area sum is used instead of the peak-height sum, a proportional relationship exists in both modes. To obtain reproducible voltammograms, the silver electrode is electrochemically treated before the electrodeposition of sulfide to remove the oxide film on it.

Determination of Sodium Nitroprusside by Flow Injection Analysis Based on Its Catalyzed Reaction of Azo Dye with Titanium(III)

A sensitive flow-injection spectrophotometric method has been developed for the determination of sodium nitroprusside (SNP). The method is based on the catalytic effect of SNP on the reaction between titanium(III) chloride and an azo dye. The azo dye is formed in a 200-cm reaction coil (0.5mm i.d.) by diazotizing sulfanilamide and coupling with N-(1-naphthyl)ethylenediamine and then mixing with an SNP solution. Titanium(III) chloride solution is injected into a stream of water and merged with an SNP-dye mixture. A decolorizing reaction takes place in a 50cm coil (0.8mm i.d.) and the decrease in absorbance (ΔA), which is proportional to the SNP concentration is measured continuously at 530nm. The RSD is 0.45% (n=10) and 0.6% (n=10) for 5×10-7M and 1×10-6M SNP solutions, respectively. The limit of detection (twice the blank standard deviation) is 5×10-8M (14.9ng ml-1) SNP. EDTA interferes even at 1μg ml-1 level on the determination of SNP.