The quality of food is an increasingly important matter of concern in Europe. The feeding stuffs poisoning episode that occurred in Belgium in May 1999 pointed out the vulnerability of the food chain and the lack of appropriate monitoring. Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorobiphenyls (PCBs) were the key contaminants involved. This has triggered new EU legislation, including maximum and action limits for relevant food and feed products as well as requirements for analytical method used to verify compliance. Large monitoring programs to test food and feed have been launched and, in many countries, efforts to monitor dioxins and related compounds strongly increased. To cope with the large number of samples statistically required for monitoring, the recommanded strategy involves the use of screening methods based on low resolution mass spectrometry (LRMS) and/or bio-assays, and high resolution mass spectrometry (HRMS) method, used to bear out their presence. Major analytical challenges had to be met to face with the large number of samples including the authoritys requests on developing screening and alternative methods for monitoring programs of PCDD/Fs and PCBs in food and feed. The first part of this document is devoted to the development of an alternative LRMS-based method for PCDD/Fs and PCBs measurement in food and feed. The second part of this thesis is an answer to the basic questions commonly addressed to all analytical chemists developing method but here in a particular context due to very specific family of compounds involved: How to make sure that my method is able to achieve sufficient accuracy on results? Are there any analytical benchmarks available for validation purposes? How to evaluate measurement uncertainty expressed in toxic equivalent (TEQ) units? How to report results right? How can the proficiency of my laboratory be measured? To ensure the quality of data obtained, laboratories in charge of the food control on PCDD/Fs and dioxin-like PCBs encounter a number of severe problems. One has to mention the lack of sufficient and reliable certified reference materials that are necessary to validate methods, too scarce data available on current analytical method performances, and the absence of quality criteria approach for analytical method. During the course of this work, I contributed to answer these questions to the general analytical effort by providing useful tools and methodologies. At that time, straightforward answers could not be found in the scientific literature. One of the reasons was the scarce data of dioxins in food and feed available. One can also mention the unusual part the dioxins play in chemical analysis. Indeed, the main features that characterize a dioxin measurement are the low levels at which these compounds occur in biological samples (sub parts-per-trillion), levels that are currently not explored by any other applications in chemical analysis in the food sector and therefore the difficulty to cope with precision models available; the reporting of results expressed in total tetrachloro dibenzo-p-dioxin (TCDD) toxic equivalent concentration for compliance assessment with statutory limits; and, what necessarily follows from the decision-making: the statement of the uncertainty interval also expressed in toxic units. To answer the foregoing questions in an international frame, notions such as validation of analytical procedures, fitness for purpose, internal quality control, interlaboratory studies, proficiency testing, measurement uncertainty, traceability had to be introduced. They are all encompassed in the analytical quality assurance management a laboratory should implement. These concepts are strongly connected to statistical techniques. This branch of analytical chemistry that consists in extracting relevant information from data using statistical and mathematical methods adapted to the specific needs for the chemists is called chemometrics. Quality is an essential preoccupation of chemometrics but it cannot be only limited to these aspects. Chemometrics relates also to other topics such as experiments and experimental design methodologies, (new) knowledge about chemical systems. Chemometrics and quality This thesis treats several aspects and new approaches of quality assurance for an ultra-trace contaminant laboratory: external method validation through interlaboratory studies and estimation of repeatability, reproducibility and trueness using simple statistics based on normal distributions (ISO 5725) but also more complex statistical tests for heavily tailed, skewed or even bimodal distributions; the production and the use of a reference material for internal validation and internal quality control (QC) purposes; advanced statistics in quality control chart and multi-level control charts for sensitive detection of bias; proposal of quality criteria for assessment of proficiency of dioxin laboratories; proposal of benchmark precision for internal validation purposes; estimation of measurement uncertainty. The thesis is divided in the following chapters: Chapter 1 is a general introduction for dioxins and related compounds. It consists of a brief introduction to general characterization, mechanism of toxicity, human exposure and European legislation in food and feed. Chapter 2 provides an overview of the analytical procedures for mass spectrometry based methods. It gives a brief summary of the most frequently used techniques to extract and purify PCDDs, PCDFs and dioxin-like PCBs (DL-PCBs) from food and feed matrices. Regarding detection, special attention of the principles of detection and quantification by HRMS in selected ion monitoring mode (SIM) and the quadrupole ion storage low resolution mass spectrometer in MS/MS mode is addressed. Chapter 3 discusses the development and optimization of a large volume injection (LVI)-gas chromatography (GC)-ion trap MS/MS method as an alternative to GC-HRMS for the measurement of PCDD/Fs in food and feed. Instrumental detection limits were lowered by a factor 2 to 3 with the development, in collaboration with the manufacturer, of a system of damping gas pressure inside the trap that improves precursor ions trapping efficiency. We achieved 5:1 signal to noise with the injection of 200 fg of 2,3,7,8 TCDD. With slight adjustments to sample size and final extract volume, we demonstrated on QC samples the good agreement between this method and the reference GC/HRMS method for PCDD/Fs and DL-PCBs in food and feed. In chapter 4, the first European inter-laboratory study on dioxins, furans and dioxin-like PCBs using the HRGC/HRMS method in animal feed samples is described with two main objectives. The first objective was to produce a reference material for internal validation and QC purposes. The second objective was to assess the analytical performances of the GC-HRMS method close to maximum levels as no data were available at that time and to check whether EU directives requirements were met. Chapter 5 is a general discussion on the capability of the state-of-the-art HRGC/HRMS method to provide reliable results at decreasing maximum levels. Levels have to decrease according to EU policy regarding human exposure to those contaminants. In this case, we present the issue from a different angle, i.e. the analytical point of view for the future establishment of target levels. Based on the results of PCDD/Fs and DL-PCBs interlaboratory study in animal feedingstuffs described in chapter 4, we demonstrated for the sum of the 17 PCCD/Fs toxic congeners that reliable results can be easily provided up to a value of 0.17 ng WHO-TEQ/kg. The ability to reliably quantify a minute trace of these contaminants has been pointed out with the aim of providing an analytical benchmark for the future establishment of target dioxin levels in animal feedingstuffs. Hence, both analytical and toxicological aspects should be examined together to set realistic target levels achievable for most dioxin laboratories involved in monitoring programs. One of the central themes of this thesis is the establishment of an empirical relationship between reproducibility standard deviation and the dioxin congeners level in food and feed. Chapter 6 deals with raw data from numerous performances interlaboratory studies of PCDD/Fs and DL-PCBs in food and feed. Striking linear functions in log scale between reproducibility standard deviation and congeners level over a concentration range of 10-8 to 10-14 g per g fresh weight were observed. The data fit very well to a Horwitz-type function of the form sR = 0.153c0.904, where sR and c are dimensionless mass ratios expressed in pg/g on fresh weight, regardless of the nature of the toxic congeners, food and feed matrices, or sample preparation methods. I called this relationship the dioxin function. One of the main features of the dioxin function could be its use as a suitable fitness-for-purpose criterion for dioxins and related compounds in proficiency testing (PT) exercises. We illustrated its use with practical example with data from the largest international PT in this field. Another application is its use as benchmark precision criteria for internal validation. Chapter 7 discusses the role of internal quality control (IQC) to monitor analytical processes. Introducing new QC methods derived from the industrial practice to analytical chemistry, improving data evaluation and allowing to detect shifts or trends, are elements that are difficult to point out with classical approach (Shewhart chart). The importance of ARL (average run length) as a key-criteria of the efficiency of a quality control procedure will be emphasized. The introduction of the multivariate approach of multilevel control with the Hotelling's T2-test will lead to a better detection of random errors than the independently managed conventional Shewhart charts. Moreover, the Exponentially Weighted Moving Average (EWMA) will offer a flexible tool for detecting the inacurracy of a method, especially where small shifts or bias are of interest. All these concepts, recently introduced in clinical chemistry, were applied here for the monitoring of PCDD/Fs and DL-PCBs in food and feed. Chapter 8 introduces the concept of measurement uncertainty (MU). Three top-down approaches for uncertainty estimation are proposed on the example of the GC-HRMS method for PCDD/Fs and DL-PCBs in various food and feed matrices: the approach which combines long-term precision and trueness data to obtain an estimate of MU (Barwick and Ellision method); the approach which uses the reproducibility estimate from interlaboratory-studies as uncertainty estimate; the concept of accuracy profile used in the context of validation and internal quality control to assess MU. Chapter 9 presents a general conclusion

<p>The online adaptive radiation therapy for prostate cancer based on re-optimization has been shown to provide better daily target coverage through the treatment course, especially in treatment sessions with large anatomical deformation. However, the clinical implementation of such technique is still limited primarily due to two major challenges: the low efficiency of re-optimization and the lack of online quality assurance technique to verify delivery accuracy. This project aims at developing new techniques and understandings to address these two challenges. </p><p>The study was based on retrospective study on patient data following IRB-approved protocol, including both planning Computer Tomography (CT) and daily Cone-Beam Computer Tomography (CBCT) images. The project is divided in to three parts. The first two parts address primarily the efficiency challenge; and the third part of this project aims at validating the deliverability of the online re-optimized plans and developing an online delivery monitoring system. </p><p><bold>I. Overall implementation scheme.</bold> In this part, an evidence-based scheme, named Adaptive Image-Guided Radiation Therapy (AIGRT), was developed to integrate the re-optimization technique with the current IGRT technique. The AIGRT process first searches for a best plan for the daily target from a plan pool, which consists the original CT plan and all previous re-optimized plans. If successful, the selected plan is used for the daily treatment with translational shifts. Otherwise, the AIGRT invokes re-optimization process of the CT plan for the anatomy-of-the-day, which is added to the plan pool afterwards as a candidate plan for future fractions. The AIGRT scheme is evaluated by comparisons with daily re-optimization and online repositioning techniques based on daily target coverage, Organ-at-Risk (OAR) sparing and implementation efficiency. Simulated treatment courses for 18 patients with re-optimization alone, re-positioning alone and AIGRT shows that AIGRT offers reliable daily target coverage that is highly comparable to re-optimization everyday and significantly improves compared to re-positioning. AIGRT is also seen to provide improved organs-at-risk (OARs) sparing compared to re-positioning. Apart from dosimetric benefits, AIGRT in addition offers an efficient scheme to integrate re-optimization to current re-positioning-based IGRT workflow.</p><p><bold>II. Strategies for automatic re-optimization.</bold> This part aims at improving the efficiency of re-optimization through automation and strategic selections of optimization parameters. It investigates the strategies for performing fast (~2 min) automatic online re-optimization with a clinical treatment planning system; and explores the performance with different input parameters settings: the DVH objective settings, starting stage and iteration number (in the context of real time planning). Simulated treatments of 10 patients were re-optimized daily for the first week of treatment (5 fractions) using 12 different combinations of optimization strategies. Options for objective settings included guideline-based RTOG objectives, patient-specific objectives based on anatomy on the planning CT, and daily-CBCT anatomy-based objectives adapted from planning CT objectives. Options for starting stages involved starting re-optimization with and without the original plan's fluence map. Options for iteration numbers were 50 and 100. The adapted plans were then analysed by statistical modelling, and compared both in terms of dosimetry and delivery efficiency. The results show that all fast online re-optimized plans provide consistent coverage and conformity to the daily target. For OAR sparing however, different planning parameters led to different optimization results. The 3 input parameters, i.e. DVH objectives, starting stages and iteration numbers, contributed to the outcome of optimization nearly independently. Patient-specific objectives generally provided better OAR sparing compared to guideline-based objectives. The benefit in high-dose sparing from incorporating daily anatomy into objective settings was positively correlated with the relative change in OAR volumes from planning CT to daily CBCT. The use of the original plan fluence map as the starting stage reduced OAR dose at the mid-dose region, but increased 17% more monitor units. Only < 2cc differences in OAR V50% / V70Gy / V76Gy were observed between 100 and 50 iterations. Based on these results, it is feasible to perform automatic online re-optimization in ~2 min using a clinical treatment planning system. Selecting optimal sets of input parameters is the key to achieving high quality re-optimized plans, and should be based on the individual patient's daily anatomy, delivery efficiency and time allowed for plan adaptation. </p><p><bold>III. Delivery accuracy evaluation and monitoring.</bold> This part of the project aims at validating the deliverability of the online re-optimized plans and developing an online delivery monitoring system. This system is based on input from Dynamic Machine Information (DMI), which continuously reports actual multi-leaf collimator (MLC) positions and machine monitor units (MUs) at 50ms intervals. Based on these DMI inputs, the QA system performed three levels of monitoring/verification on the plan delivery process: (1) Following each input, actual and expected fluence maps delivered up to the current MLC position were dynamically updated using corresponding MLC positions in the DMI. The difference between actual and expected fluence maps creates a fluence error map (FEM), which is used to assess the delivery accuracy. (2) At each control point, actual MLC positions were verified against the treatment plan for potential errors in data transfer between the treatment planning system (TPS) and the MLC controller. (3) After treatment, delivered dose was reconstructed in the treatment planning system based on DMI data during delivery, and compared to planned dose. FEMs from 210 prostate IMRT beams were evaluated for error magnitude and patterns. In addition, systematic MLC errors of ±0.5 and ±1 mm for both banks were simulated to understand error patterns in resulted FEMs. Applying clinical IMRT QA standard to the online re-optimized plans suggests the deliverability of online re-optimized plans are similar to regular IMRT plans. Applying the proposed QA system to online re-optimized plans also reveals excellent delivery accuracy: over 99% leaf position differences are < 0.5 mm, and the majority of pixels in FEMs are < 0.5 MU with errors exceeding 0.5 MU primarily located on the edge of the fields. All clinical FEMs observed in this study have positive errors on the left edges, and negative errors on the right. Analysis on a typical FEM reveals positive correlation between the magnitude of fluence errors and the corresponding leaf speed. FEMs of simulated erroneous delivery exhibit distinct patterns for different MLC error magnitudes and directions, indicating the proposed QA system is highly specific in detecting the source of errors. Based on these results, it can be concluded that the proposed online delivery monitoring system is very sensitive to leaf position errors, highly specific of the error types, and therefore meets the purpose for online delivery accuracy verification. Post-treatment dosimetric verification shows minimal difference between planned and actual delivered DVH, further confirming that the online re-optimized plans can be accurately delivered.</p><p>In summary, this project addressed two most important challenges for clinical implementation of online ART, efficiency and quality assurance, through innovative system design, technique development and validation with clinical data. The efficiencies of the overall treatment scheme and the re-optimization process have been improved significantly; and the proposed online quality assurance system is found to be effective in catching and differentiating leaf motion errors.</p> / Dissertation

The performance of Internet-based services depends on many server-side, client-side, and network related factors. Often, the interaction among the factors or their effect on service performance is not known or well-understood. The complexity of these services makes it difficult to develop analytical models. Lack of models impedes network management tasks, such as predicting performance while planning for changes to service infrastructure, or diagnosing causes of poor performance. We posit that we can use statistical causal methods to model performance for Internet-based services and facilitate performance related network management tasks. Internet-based services are well-suited for statistical learning because the inherent variability in many factors that affect performance allows us to collect comprehensive datasets that cover service performance under a wide variety of conditions. These conditional distributions represent the functions that govern service performance and dependencies that are inherent in the service infrastructure. These functions and dependencies are accurate and can be used in lieu of analytical models to reason about system performance, such as predicting performance of a service when changing some factors, finding causes of poor performance, or isolating contribution of individual factors in observed performance. We present three systems, What-if Scenario Evaluator (WISE), How to Improve Performance (HIP), and Network Access Neutrality Observatory (NANO), that use statistical causal methods to facilitate network management tasks. WISE predicts performance for what-if configurations and deployment questions for content distribution networks. For this, WISE learns the causal dependency structure among the latency-causing factors, and when one or more factors is changed, WISE estimates effect on other factors using the dependency structure. HIP extends WISE and uses the causal dependency structure to invert the performance function, find causes of poor performance, and help answers questions about how to improve performance or achieve performance goals. NANO uses causal inference to quantify the impact of discrimination policies of ISPs on service performance. NANO is the only tool to date for detecting destination-based discrimination techniques that ISPs may use. We have evaluated these tools by application to large-scale Internet-based services and by experiments on wide-area Internet. WISE is actively used at Google for predicting network-level and browser-level response time for Web search for new datacenter deployments. We have used HIP to find causes of high-latency Web search transactions in Google, and identified many cases where high-latency transactions can be significantly mitigated with simple infrastructure changes. We have evaluated NANO using experiments on wide-area Internet and also made the tool publicly available to recruit users and deploy NANO at a global scale.

As web applications occupy an increasingly important role in the day-to-day lives of millions of people, testing and analysis techniques that ensure that these applications function with a high level of quality are becoming even more essential. However, many software quality assurance techniques are not directly applicable to modern web applications. Certain characteristics, such as the use of HTTP and generated object programs, can make it difficult to identify software abstractions used by traditional quality assurance techniques. More generally, many of these abstractions are implemented differently in web applications, and the lack of techniques to identify them complicates the application of existing quality assurance techniques to web applications. This dissertation describes the development of program analysis techniques for modern web applications and shows that these techniques can be used to improve quality assurance. The first part of the research focuses on the development of a suite of program analysis techniques that identifies useful abstractions in web applications. The second part of the research evaluates whether these program analysis techniques can be used to successfully adapt traditional quality assurance techniques to web applications, improve existing web application quality assurance techniques, and develop new techniques focused on web application-specific issues. The work in quality assurance techniques focuses on improving three different areas: generating test inputs, verifying interface invocations, and detecting vulnerabilities. The evaluations of the resulting techniques show that the use of the program analyses results in significant improvements in existing quality assurance techniques and facilitates the development of new useful techniques.

Engineering education reform has been a topic of discussion for the last twenty years. The concern has only intensified in recent years as stakeholders strive to improve quality in engineering education. Today, stakeholders are recognizing that one of the keys to successful engineering education reform is in taking a systems view of higher education. Academic departments within the higher education system are organized around academic disciplines for the purpose of creating, transferring, and applying knowledge in three principal areas: teaching, research and service. This study addresses the need for quality improvement in the engineering higher education system by first completing a literature review in order to identify recurring themes on the issue. A proposed systems view is presented. The thesis builds a case for viewing students as the primary stakeholder based on stakeholder theory concepts. The application of a systems view is then used to identify the impacts of the recurring issues on the identified stakeholders of the system. Recommendations are made to address the system’s issues.

published_or_final_version / Housing Management / Master / Master of Housing Management

M. Tech. Business Administration / This study was conducted at UNISA Library in 2012 in order to assess the perceptions regarding the process mapping exercise that was conducted by UNISA Library as a means of improving performance based on a random sample of 43 employees of UNISA Library. The study also focused on the implementation of continuous improvement at the UNISA Library.

Η παρούσα εργασία ασχολείται με την καταμέτρηση και αποτύπωση της ποιότητας σε μία μεγάλη εταιρεία, την ΑΒ Βασιλόπουλος. Ως επί το πλείστον, η αποτύπωση της ποιότητας στις διάφορες εταιρίες πραγματοποιείται με τη χρήση ποικιλίας πιστοποιήσεων μέσω διαφόρων οργανισμών. Η συγκεκριμένη εργασία επιχειρεί να πραγματοποιήσει μια καταγραφή σχετικά με τα επίπεδα της υφιστάμενης ποιότητας βάσει της άποψης των εργαζομένων στην συγκεκριμένη εταιρεία. Παράλληλα, έγινε προσπάθεια να αποτυπωθούν οι σημαντικότεροι παράγοντες που, βάσει των απόψεων των εργαζομένων, επηρεάζουν την ποιότητα αυτή. Βάσει των αποτελεσμάτων της έρευνας προέκυψε το ότι οι εργαζόμενοι κατά κύριο λόγο συμφωνούν πολύ, ότι εκτελούν όλες τις αναγνωρισμένες οδηγίες εργασίας και διαδικασίες ποιότητας και δήλωσαν ότι είναι έτοιμοι για κάθε αλλαγή που μπορεί να προκύψει κατά την εφαρμογή ISO 9001/22000. Επιπλέον δήλωσαν ότι είναι έτοιμοι να ελεγχθούν ανά πάσα στιγμή και πως η ιδέα για συμμετοχή στις δραστηριότητες συνεχής βελτίωσης και ποιότητας τους αρέσει. Τέλος οι περισσότεροι είναι ευτυχείς που επιλέξανε αυτή την εταιρεία να εργαστούν και ένα μεγάλο ποσοστό δήλωσε πως θα παραμείνει στην εν λόγω εταιρεία για τα επόμενα χρόνια. Η πρωτογενής έρευνα (μέσω της συμπλήρωσης των ερωτηματολογίων) πραγματοποιήθηκε τον Σεπτέμβριο του 2013). / This paper deals with the counting and recording quality in a large company, AB Vassilopoulos. Mostly, printing quality in various companies through the use of a variety of certifications through various organizations. This paper attempts to make a record of the levels of the existing quality under the view of workers in a particular company. There was also attempt to identify the most important factors that, based on the views of employees, affecting such quality. Based on the results of the survey revealed that workers largely agree too that perform all identified work instructions and quality procedures and said they were ready for any changes that may arise in implementing ISO 9001/22000. ALSO said it is ready to be tested at any time and that the idea to participate in continuous improvement activities and quality they like. Finally most are glad they chose this company to work and a large percentage said they would remain in the company for years. The primary research (through the completion of questionnaires) took place in September 2013.

Tyrimo problema, aktualumas ir naujumas Nuolat tobulinant kirpėjų profesijos mokytojų profesines kompetencijas, kurių dėka būtų kartu gerinami mokinių praktiniai įgūdžiai ir žinios, parengsime kūrybingus, kompetentingus, aukštos kvalifikacijos kirpėjus, gebančius taikyti naujas darbo technikas ir technologijas, turinčius puikias galimybes Europos darbo rinkose. Svarbu, kad patys profesijos mokytojai siektų tobulėti. Todėl profesinių kompetencijų tobulinimas yra aktuali problema, nuo kurios priklauso praktinio mokymo kokybė. Lietuvoje yra atlikta tyrimų apie įvairių profesijų atstovų požiūrį į profesines kompetencijas, jų raišką bei tobulinimo/si poreikius. Tad akivaizdu, kad kompetencijoms skiriamas didelis dėmesys, tačiau mažai tyrinėta kirpėjų profesijos mokytojų tobulnimąsi, kaip prielaida praktinio mokymo kokybei gerinti. Todėl šiame darbe, bus siekiama atskleisti kirpėjų profesijos mokytojų požiūrį ir socialinių dalininkų nuomonę į profesinių kompetencijų tobulinimo svarbą, gerinant praktinio mokymo kokybę. Tyrimo tikslas – Pristatyti kirpėjų profesijos mokytojų profesinių kompetencijų tobulinimą kaip prielaidą praktinio mokymo kokybei gerinti. Tyrimo uždaviniai: 1. Pristatyti praktinio mokymo kokybės užtikrinimo sampratą. 2. Teoriškai pagrįsti profesijos mokytojų profesinių kompetencijų tobulinimo aktualumą praktinio mokymo kokybei gerinti. 3. Atskleisti kirpėjų profesijos mokytojų požiūrį į jų profesinių kompetencijų tobulinimo svarbą siekiant gerinti praktinio mokymo... [toliau žr. visą tekstą] / The problem, relevance and novelty of research. Consequently, the development of professional competency is closely linked not only with the quality of the practical training but it may cause great changes in the education system as well. So, only the constant development of Hairdresser‘s professional competency can help to give a propper training for young professionals having great possibilities in European labor market. That is why the Professional competency development is a key problem which says greatly on the quality of practical training. The research of different specialits‘ attitude towards professional competence as well as the needs of it among the learners was carried out in Lithuania. It is obvious that competency is highlighted greatly but little research is done in the field of competency development as the assumption to improve the quality of practical training. Following the situation, the main objective of the work is to reveal both, the attitudes of Hairdressers’ professional trainers and stakeholders' towards the importance of professional competency development with the aim to improve the quality of practical training. The aim of the research – to present the professional competency development of Hairdressers’ trainers as the assumption to improve the quality of practical training. The tasks of the research: 1. To deliver the assurance concept of practical training quality. 2. To stimulate theoretically the development of professional... [to full text]

<p>In South Africa, it is estimated that approximately 70% of the population frequently make use of traditional medicinal plants for their health care needs. The use of Lessertia frutescens by the&nbsp / various cultural groups in South Africa dates back to the earlier civilizations and continues to be used today to treat a multitude of ailments. To get the best results from a medicinal plant, one&nbsp / &nbsp / would need to ensure that the crude material is of good quality through interventions like being properly grown, well dried and correctly processed. This would add a measure of quality&nbsp / assurance, which will contribute towards the safety and efficacy aspect of herbal medicine. The aim of this study was to investigate what impact a particular season of harvest and the time in&nbsp / storage would have on the flavonoid and triterpenoid marker levels of Lessertia frutescens. To achieve this, the following was investigated: (1) storage variation of Lessertia frutescens leaves&nbsp / by comparing the results obtained from the High Performance Liquid Chromatography (HPLC) analysis of the flavonoids and triterpenoids, (2) seasonal variation of Lessertia frutescens&nbsp / leaves by comparing the results obtained from the HPLC analysis of the flavonoids and triterpenoids, (3) leaf and stem variation of Lessertia frutescens by comparing the results obtained from HPLC analysis of the flavonoids and triterpenoids. The hypotheses were: (1) the stored sample would indicate the same level of the biomarkers for the flavonoids and triterpenoids, as that of&nbsp / the freshly prepared sample, (2) the sample that was harvested during the summer season would indicate higher levels of the biomarkers of&nbsp / flavonoids and triterpenoids than the other three&nbsp / seasons, (3) the leaf sample would indicate the same level of the biomarkers for the flavonoids and triterpenoids, as that of the stem sample. An Agilent 1200 series HPLC was used for the&nbsp / determination of the flavonoids sutherlandin A and sutherlandin D as well as the triterpenoids sutherlandioside B and sutherlandioside D. Results show that for both sutherlandin A (summer:&nbsp / 3.67 &plusmn / 2.88 mg/ml / storage: 4.07 &plusmn / 2.88 mg/ml) and D (summer: 4.10 &plusmn / 1.06 mg/ml / storage: 4.25 &plusmn / 1.06 mg/ml) show significantly (P &lt / 0.0001) higher concentrations in the case of the storage&nbsp / amples. For both sutherlandioside B (summer: 3.01 &plusmn / 0.39 mg/ml / storage: 2.82 &plusmn / 0.39 mg/ml) and D (summer: 5.82 &plusmn / 0.42 mg/ml / storage: 4.66 &plusmn / 0.42 mg/ml) show significantly (P &lt / &nbsp / .0001)&nbsp / higher concentrations in the case of the fresh summer samples.For the seasonal comparison, results show that for sutherlandin A (summer: 3.67 &plusmn / 12.49 mg/ml / autumn: 4.75 &plusmn / &nbsp / 12.49 mg/ml / winter: 4.23 &plusmn / 12.49 mg/ml / spring: 6.56 &plusmn / 12.49 mg/ml) show significantly (P &lt / 0.0001) higher concentrations in the case of the spring sample. For sutherlandin D (summer: 4.10&nbsp / &nbsp / 10.32 mg/ml / autumn: 6.37 &plusmn / 10.32 mg/ml / winter: 5.25 &plusmn / 10.32 mg/ml / spring / 6.08 &plusmn / 10.32 mg/ml) show significantly (P &lt / 0.0001) higher concentrations in the case of the autumn sample. For both sutherlandioside B (summer: 3.01 &plusmn / 7.19 mg/ml / autumn: 2.15 &plusmn / 7.19 mg/ml / winter: 2.89 &plusmn / 7.19 mg/ml / spring: 1.47 &plusmn / 7.19 mg/ml) and D (summer: 5.82 &plusmn / 14.48 mg/ml / autumn: 3.33 &plusmn / 14.48 mg/ml / winter: 4.23 &plusmn / 14.48 mg/ml / spring: 2.50 &plusmn / 14.48 mg/ml) show significantly (P &lt / 0.0001) higher concentrations in the case of the autumn sample. For the summer&nbsp / leaf/stem comparison, results show that for sutherlandin A (leaf: 3.67 &plusmn / 8.18 mg/ml / stem: 4.67 &plusmn / 8.18 mg/ml) show significantly (P &lt / 0.0001) higher concentrations in the case of the stem&nbsp / sample. For the sutherlandin D (leaf: 4.10 &plusmn / 4.81 mg/ml / stem: 3.31 &plusmn / 4.81 mg/ml) show significantly (P &lt / 0.0001) higher concentrations in the case of the summer leaf sample. For both the&nbsp / sutherlandioside B (leaf: 3.01 &plusmn / 4.24 mg/ml / stem: 3.62 &plusmn / 4.24 mg/ml) and D (leaf: 5.82 &plusmn / 0.42 mg/ml / stem: 5.80 &plusmn / 0.42 mg/ml) show significantly (P &lt / 0.0001) higher concentrations in the&nbsp / case of the stem samples. Results demonstrate that the production of secondary metabolites are influenced by&nbsp / &nbsp / environmental factors like seasonal harvesting, as indicated by the variation in the chemical constituent composition of Lessertia frutescens depending on the season collected in. Moreover, the storage of Lessertia frutescens for a period of one year resulted in an&nbsp / increase of two of the four constituents being monitored. There was slight variations in the chemical constituents, depending on whether the leaf or stem material of Lessertia frutescens was being used. Finally, the type of chemical constituent being monitored was also important in the consideration of this study. Therefore, this study can be seen as a starting point to further&nbsp / &nbsp / investigations of these aspects, which are of clinical, pharmacological and economic</p>