Flow injection analysis (FIA) determination of lead by hydride generation in banded coral skeletons /

A flow injection hydride generation direct current plasma atomic emission spectrometric (FI-HG-DCP-AES) method was developed for the determination of lead at ng.ml-l level. Potassium ferricyanide (K3Fe(CN)6) was used along with sodium tetrahydroborate(III) (NaBH4) to produce plumbane (PbH4) in an acid medium. The design of a gas-liquid separator (hydride generator) was tested and the parameters of the flow injection system were optimized to achieve a good detection limit and sample throughput. The technique developed gave a detection limit of 0.7 ng.ml-l(3ob). The precision at 20 ng.ml"* level was 1.6 % RSD with 1 1 measurements (n=l 1). Volume of sample loop was 500 |J.l. A sample throughput of 120 h"^ was achieved. The transition elements, Fe(II), FeOH), Cd(n), Co(II), Mn(n), Ni(II) and Zn(n) do not interfere in this method but 1 mg,l'l Cu(II) will suppress 50 % of the signal from a sample containing 20 ng.ml'l Pb. This method was successfully applied to determine lead in a calcium carbonate (CaC03) matrix of banded coral skeletons from Si-Chang Island in Thailand.

Arsenic speciation by ion-exchange chromatography with on- line determination by hydride generation: electronic modification of the D.C. plasma by photon counting

A method using L-cysteine for the determination of arsenous acid (As(III)), arsenic acid (As(V)), monomethylarsonic acid (MMAA), and dimethylarsinic acid (DMAA) by hydride generation was demonstrated. The instrument used was a d.c. plasma atomic emission spectrometer (OCP-AES). Complete recovery was reported for As(III), As(V), and DMAA while 86% recovery was reported for MMAA. Detection limits were determined, as arsenic for the species listed previously, to be 1.2, 0.8, 1.1, and 1.0 ngemL-l, respectively. Precision values, at 50 ngemL-1 arsenic concentration, were f.80/0, 2.50/0, 2.6% and 2.6% relative standard deviation, respectively. The L-cysteine reagent was compared directly with the conventional hydride generation technique which uses a potassium iodide-hydrochloric acid medium. Recoveries using L-cysteine when compared with the conventional method provided the following results: similar recoveries were obtained for As(III), slightly better recoveries were obtained for As(V) and MMAA, and significantly better recoveries for DMAA. In addition, tall and sharp peak shapes were observed for all four species when using L-cysteine. The arsenic speciation method involved separation by ion exchange .. high perfonnance liquid chromatography (HPLC) with on-line hydride generation using the L.. cysteine reagent and measurement byOCP-AES. Total analysis time per sample was 12 min while the time between the start of subsequent runs was approximately 20 min. A binary . gradient elution program, which incorporated the following two eluents: 0.01 and 0.5 mM tri.. sodium citrate both containing 5% methanol (v/v) and both at a pH of approximately 9, was used during the separation by HPLC. Recoveries of the four species which were measured as peak area, and were normalized against As(III), were 880/0, 290/0, and 40% for DMAA, MMAA and As(V), respectively. Resolution factors between adjacent analyte peaks of As(III) and DMAA was 1.1; DMAA and MMAA was 1.3; and MMAA and As(V) was 8.6. During the arsenic speciation study, signals from the d.c. plasma optical system were measured using a new photon-signal integrating device. The_new photon integrator developed and built in this laboratory was based on a previously published design which was further modified to reflect current available hardware. This photon integrator was interfaced to a personal computer through an AID convertor. The .photon integrator has adjustable threshold settings and an adjustable post-gain device.

Investigation into the determination of arsenic by direct current plasma atomic emission spectrometer

Improvements have been made on the currently available hydride generator system manufactured by SpectraMetrics Incorporated, because the system was found to be unsatisfactory with respect to the following: 1. the drying agent, anhydrous calcium chloride, 2. the special sample tube, 3. the direction of argon flow through the Buchner funnel when it came to dealing with real sample, that is, with reference only to aqueous extracts of soil samples. Changes that were made on the system included the replacement of anhydrous calcium chloride with anhydrous calcium sulphate and the replacement of the special sample tube with a modified one made from silica. Re-directing the flow of argon through the top of the Buchner funnel appeared to make the system compatible with aqueous extracts of soil samples. The interferences from 1000 ~g/mL of nickel(II) , cobalt(II), iron(III), copper(II) have been eliminated with the aid of 1.4 M hydrochloric acid and 1% (weight/volume) L-cystine. Greater than 90% recovery of 0.3 ~g/mL arsenic signal was achieved in each case. Furthermore, 103% of arsenic signal was accomplished in the presence of 1000 ~g/mL cadmium with 5 M Hel. tVhen each of the interferents was present in solution at 1000 ppm, a recovery of 85% was achieved by using 5 M hydrochloric acid and 3% (weight/volume) L-cystine. Without L-cystine and when 1.4 M hydrochloric acid was used, the recoveries were 0% (Ni), 0% (Co), 88% (Fe), 15% (Cu), 18% (Cd). Similarly, a solution containing 1000 ppm of each interferent gave a zero percent recovery of arsenic. The reduction of trivalent and pentavalent arsenic at a pH less than one has also been investigated and shown to be quantitative if peak areas are measured. The reproducibility determination of a 0.3 Vg/mL standard arsenic solution by hydride generation shows a relative standard deviation of 3.4%. The detection limits with and without Porapak Q have been found to be 0.6 ng/mL and 1.0 ng/mL, respectively.

Locating home : the diverse experiences of recent newcomer youth and first generation youth within Ontario's education system

This study has found that youth who or whose parents had left their home country for fear-based reasons were less involved within their school and wider community than youth who left or whose parents left for reasons concerning their social mobility. Many existing studies focus on the challenges newcomer youth experience within the education system (see Anisef, Brown, Phythian, & Sweet, 2010), however through the use of qualitative methodologies this study expanded on the current literature by further examining why it is some youth are successful in overcoming such challenges, while others are not. This study supported what has been demonstrated in the literature regarding challenges faced by newcomer youth and resources to address such challenges. Despite challenges experienced within the education system, youth planned to complete secondary school and attend a postsecondary institution. However, not all youth anticipated remaining in Canada upon completion of their education, with youth or youth whose parents left their home country for fear-based reasons frequently discussing the possibility of returning to their or their parents' home country. Thus, perhaps these youth were less involved within their school, as their goal was not necessarily to establish or maintain connections within their community as they may have viewed residing in Canada as temporary. This finding has important implications, as there are benefits to involvement in extracurricular activities, which may assist youth in overcoming challenges encountered within the education system. Therefore, it would seem that youth who had or whose parents had left their home country for reasons concerning their social mobility may have be at an advantage within the education system with respect to their involvement in school. Perhaps then this differential involvement may at least partially explain why it is some newcomer youth are able to overcome challenges they experience in the education system, while others are not. Both policy and theoretical implications are discussed.

Creating a Generation of Upstanders: Curriculum Resource to Help Ontario Educators Build Safe Schools

This project focuses on the bullying found in the 21st century elementary classrooms, more specifically in grades 4-8. These grades were found to have high levels of bullying because of major shifts in a student’s life that may place a student of this age at risk for problems with their peer relationships (Totura et al., 2009). Supporting the findings in the literature review, this handbook was created for Ontario grade 4-8 classroom teachers. The resource educates teachers on current knowledge of classroom bullying, and provides them with information and resources to share with their students so that they can create a culture of upstanders. Upstanders are students who stand up for the victims of bullying, and have the self-esteem and strategies to stand up to classroom bullies. These upstanders, with the support of their classroom teachers and their peers, will be a force strong enough to build the government-mandated Safe School environment.

Creating a Generation of Upstanders: Curriculum Resource to Help Ontario Educators Build Safe Schools

This project focuses on the bullying found in the 21st century elementary classrooms, more specifically in grades 4-8. These grades were found to have high levels of bullying because of major shifts in a student’s life that may place a student of this age at risk for problems with their peer relationships (Totura et al., 2009). Supporting the findings in the literature review, this handbook was created for an Ontario grade 4-8 classroom teachers. The resource educates teachers on current knowledge of classroom bullying, and provides them with information and resources to share with their students so that they can create a culture of upstanders. Upstanders are students who stand up for the victims of bullying, and have the self-esteem and strategies to stand up to classroom bullies. These upstanders, with the support of their classroom teachers and their peers, will be a force strong enough to build the government-mandated Safe School environment.