Production and Control of Reference Materials for Water Microbiology

1991 ◽  
Vol 24 (2) ◽  
pp. 53-56 ◽  
Author(s):  
K. A. Mooijman ◽  
A. H. Havelaar ◽  
J. A. Hoekstra ◽  
N. G. W. N. van Strijp-Lockefeer
Keyword(s):  
Reference Materials ◽  
Milk Powder ◽  
Contamination Level ◽  
Long Term Stability ◽  
Collaborative Studies ◽  
Water Microbiology ◽  
Challenge Tests ◽  
Short Time ◽  
And Control

Reference materials for water microbiology were prepared by spray-drying milk, artificially contaminated with a known test strain. The resulting highly contaminated milk powder was mixed with sterile milk powder to a contamination level of 2000-3000 cfu/g. Gelatin capsules were filled with the mixture (0.2 g/capsule) to produce the reference materials. Test strains used were: WR1 Escherichia coli, WR3 Enterobacter cloacae, WR63 Enterococcus faecium and WR51 Staphylococcus spec. Optimalization of the mixing procedure and aging of the highly contaminated milk powder resulted in relatively homogeneous and stable reference materials. Short-time challenge tests at “high” temperatures (30 and 37 °C) may be predictive for long-term stability at “low” temperatures (4-6 °C). Reference materials with strain WR3 were stable for one week at 30 °C and for at least 6 months at 4-6 °C. Possible applications of the reference materials are: quality control of routine measurements, comparison of the efficiency of different culturing methods and as a standardized sample in collaborative studies.

scholarly journals Pakatan Harapan dan Senario Politik Kelantan: Analisis Pengajaran Politik Pasca PRU 14 (2018-2020)

2021 ◽  
Vol 8 (1) ◽  
pp. 25-55
Author(s):  
Saiyid Radzuwan Syed Sopi
Keyword(s):  
Qualitative Study ◽  
Reference Materials ◽  
Education System ◽  
The State ◽  
Political Strategy ◽  
State Administration ◽  
Set Up ◽  
And Control ◽  
Ruling Party

The 14th general election (GE 14) reveals that Pakatan Harapan (PH) had become a ruling party (2018-2020), but they failed to get any parliamentary or state assembly seats in Kelantan. The failure of PH to expand their influence in Kelantan is due to several traditional factors that are difficult for PH to break it out. This study is a qualitative study and reference materials that are physical and online are used as reference sources. In addition, information regarding political scenario in Kelantan also obtained through interviews with some respondents live in Kelantan. Therefore, this research found that the desire of PH to expand their influence in Kelantan was blurred. This is because PAS wisely set up a long-term political strategy by strengthening the education system under YIK, producing many hardcore supporters or fanatic followers, controlling the ‘surau’ and the mosques according to their needs and control of the state administration. Furthermore, PH needs to make concrete reformations to the party’s management such as producing talented young leaders and fostering a spirit of cooperation among members of the PH coalition if they are still interested in power in Kelantan.

scholarly journals An updated protocol based on CLSI document C37 for preparation of off-the-clot serum from individual units for use alone or to prepare commutable pooled serum reference materials

2020 ◽  
Vol 58 (3) ◽  
pp. 368-374 ◽  
Author(s):  
Uliana Danilenko ◽  
Hubert W. Vesper ◽  
Gary L. Myers ◽  
Patric A. Clapshaw ◽  
Johanna E. Camara ◽  
...  
Keyword(s):  
Human Serum ◽  
Reference Materials ◽  
Frozen Storage ◽  
Metrological Traceability ◽  
Medical Laboratory ◽  
Serum Samples ◽  
Long Term Stability ◽  
Individual Human

AbstractManufacturers of in vitro diagnostic medical devices, clinical laboratories, research laboratories and calibration laboratories require commutable reference materials that can be used in the calibration hierarchies of medical laboratory measurement procedures used for human specimens to establish metrological traceability to higher order reference systems. Commutable materials are also useful in external quality assessment surveys. In order to achieve these goals, matrix-based reference materials with long-term stability, appropriate measurand concentrations and commutability with individual human specimens are required. The Clinical and Laboratory Standards Institute (CLSI) guideline C37-A (now archived) provided guidance to prepare commutable pooled serum reference materials for use in the calibration hierarchies of cholesterol measurement procedures. Experience using the C37-A guideline has identified a number of technical enhancements as well as applications to measurands other than cholesterol. This experience is incorporated into this updated protocol to ensure the procedure will continue to meet the needs of the medical laboratory. The updated protocol describes a procedure for preparing frozen human serum units or pools with minimal matrix alterations that are likely to be commutable with individual human serum samples. The protocol provides step-by-step guidance for the planning phase, collection of individual serum units, processing the units, qualifying the units for use in a pool and frozen storage of aliquots of pooled sera to manufacture frozen serum pools. Guidance on how to perform quality control of the final product and suggestions on documentation are also provided.

Experience with Certified Reference Material Proficiency Testing for Quality Control of Wheat

1998 ◽  
Vol 6 (A) ◽  
pp. A53-A61
Author(s):  
Judit Budai ◽  
Judit Fükó
Keyword(s):  
Quality Control ◽  
Reference Material ◽  
Proficiency Testing ◽  
Reference Materials ◽  
Certified Reference Material ◽  
Certified Reference Materials ◽  
Long Term Stability ◽  
Determining Factors ◽  
Chemical Section

The Chemical Section of OMH1,2 embarked on the preparation of a series of wheat samples as Certified Reference Materials (CRMs) in 1992. The certification processes were carried out according to the recommendations of ISO. Since then we have developed a series of flour samples as well. The investigations of the long-term stability and the application of wheat and flour CRMs are continuous. Wheat is one of the most widely grown crops in Hungary and it is one of the major determining factors of the economy. Its uniform and objective qualification is of great importance. There are well-equipped laboratories available with sufficient experience but, as the proficiency testing regularly showed, certified samples need to be used to achieve exact and uniform measuring results.

Use of Reference Materials (Spray-Dried Milk Artificially Contaminated with Salmonella typhimurium) to Validate Detection Methods for Salmonella

1992 ◽  
Vol 55 (11) ◽  
pp. 855-858 ◽  
Author(s):  
PAUL H. IN ‘T VELD ◽  
SERVÉ NOTERMANS
Keyword(s):  
Salmonella Typhimurium ◽  
Reference Materials ◽  
Milk Powder ◽  
Rapid Test ◽  
Poultry Meat ◽  
Detection Methods ◽  
Contamination Level ◽  
Recovery Rates ◽  
Minced Meat ◽  
Spray Dried

Reference materials consisting of 0.28 g of spray-dried milk artificially contaminated with Salmonella typhimurium and contained in gelatin capsules (mean contamination level 4.2 salmonellae per capsule) were used to validate detection of Salmonella species in food. For this, 10 samples of 25 g of mayonnaise, milk powder, minced meat, or poultry meat were spiked with reference materials without repair and with reference materials after repair, respectively. It was found that the physiological condition of Salmonella present in the reference material had no influence on the recovery rate of the organism. The recovery rates of Salmonella were tested by applying various methods [ISO-6579 method, SALMONELLA-TEK™ (Organon Teknika), the modified semisolid Rappaport Vassiliadis agar (MSRV), and the Salmonella rapid test (Oxoid)]. The recovery rates found (averaged on the types of foods tested) were 67% for the Salmonella rapid test, 83% for the MSRV, 86% for the ISO-6579, and 91% for the SALMONELLA-TEK. The use of reference materials is recommended to validate detection of Salmonella species.

scholarly journals Amphiphilic azopolymers capable to generate photo-sensitive micelles

2011 ◽  
Vol 9 (6) ◽  
pp. 1117-1125 ◽  
Author(s):  
Ioana Moleavin ◽  
Constanta Ibanescu ◽  
Anca Hodorog-Rusu ◽  
Ecaterina Peptu ◽  
Florica Doroftei ◽  
...  
Keyword(s):  
Targeted Delivery ◽  
Critical Concentration ◽  
Fluorescence Emission ◽  
Good Control ◽  
Fluorescence Emission Spectrum ◽  
Long Term Stability ◽  
Micellar Aggregates ◽  
Preliminary Study ◽  
And Control

AbstractAmphiphilic macromolecular micelles are advantageous for drug delivery applications due to the decrease of side-effects, ease of screening drugs against degradation, long-term stability, targeted delivery and control of the amount of the released drug. A series of amphiphilic azo-polymers having a flexible or rigid main-chain were synthesized and characterized. The presence of chlorobenzyl side-groups allowed both the easy bonding of photo-sensitive or hydrophilic groups and good control of the degree of substitution. The chemical structure was confirmed by 1H-NMR. The critical concentration of aggregation (CCA) was calculated using the fluorescence emission spectrum of pyrene. The interest was focused on a preliminary study concerning the disaggregation capacity of micelles under UV irradiation. The presence of micellar aggregates was confirmed by DLS and SEM and different organization of the amphiphilic polymers was evidenced depending on polymers concentration and polymers structure. In low polymer concentrations in water predominantly globular aggregates were formed. The increase in concentration increased the polydispersity index due to the fusion of micelles and formation of associates of globular aggregates, inter-micellar associates (clusters) and vesicles.

scholarly journals The importance of cylinder passivation chemistry for preparation and long-term stability of multicomponent monoterpene primary reference materials

2018 ◽  
Author(s):  
Nicholas D. C. Allen ◽  
David R. Worton ◽  
Paul J. Brewer ◽  
Céline Pascale ◽  
Bernhard Niederhauser
Keyword(s):  
Reference Materials ◽  
Chemical Reactivity ◽  
International System ◽  
High Chemical ◽  
Term Stability ◽  
Long Term Stability ◽  
System Of Units ◽  
Primary Reference ◽  
High Chemical Reactivity

Abstract. Monoterpenes play an important role in atmospheric chemistry due to their large anthropogenic and biogenic emission sources and high chemical reactivity. As a consequence, measurements are required to assess how changes in emissions of monoterpenes impact air quality. Accurate and comparable measurements of monoterpenes in indoor and outdoor environments require gaseous primary reference materials (PRMs) that are traceable to the international system of units (SI). PRMs of monoterpenes are challenging to produce due to the high chemical reactivity and low vapour pressures of monoterpenes and also their propensity to convert into other compounds, including other terpenes. In this paper, the long-term stability of gravimetrically prepared static monoterpene PRMs produced in differently passivated cylinders, including sampling canisters, was assessed. We demonstrate that static PRMs of multiple monoterpenes can be prepared and used as a suitable long-term standard. For the first time the effect of cylinder pressure and decanting from one cylinder to another on the chemical composition and amount fraction of monoterpenes was also studied. Gravimetrically prepared PRMs of limonene in high pressure cylinders were compared to a novel portable dynamic reference gas generator based on dilution of pure limonene vapour emitted from a permeation tube.

Analytical performance and comparability of the determination of cholesterol by 12 Lipid-Research Clinics.

1977 ◽  
Vol 23 (9) ◽  
pp. 1744-1752 ◽  
Author(s):  
K Lippel ◽  
S Ahmed ◽  
J J Albers ◽  
P Bachorik ◽  
G Cooper ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Lipid Research Clinic ◽  
Cholesterol Concentration ◽  
Entire Group ◽  
Lipid Research ◽  
Collaborative Studies ◽  
Control Serum ◽  
Control Procedures ◽  
And Control

Abstract Twelve Lipid-Research Clinic laboratories performed automated cholesterol analyses on four control-serum pools of known cholesterol concentration, using the Liebermann-Burchard reaction. The analyses were done during a two-year period, with the same standards, methodology, and quality-control procedures. Estimates of analytical bias, variability, and short- and long-term trends for each instrument and for the entire group of LRC instruments are presented. High accuracy, precision, and interlaboratory comparability were achieved through the rigorous standardization and control of the entire analytical procedure. The significance of these results for long-term collaborative studies is discussed. Individual laboratory biases averaged from 0.5 to 2.0% below Abell-Kendall reference values. Between-run variability was about equal to within-run variability and inter-laboratory variation was substantially less than intra-laboratory variation. The total standard deviation for all instruments was about 0.04 g/liter. Only 8-15% of this variation was due to differences between instruments. The between-instrument standard deviation ranged from 0.011 to 0.015 g/liter; the between-run, within-instrument standard deviation ranged from 0.023 to 0.030 g/liter; and within-run standard deviation ranged from 0.023 to 0.028 g/liter. The significance of the achieved results for long-term collaborative studies is discussed.

A Few Aspects on Lubricant Selection for Stepless Chain Coverters: Efficiency and Service Life

1992 ◽  
Author(s):  
G. Schönnenbeck
Keyword(s):  
Friction Coefficient ◽  
Service Life ◽  
Standardized Test ◽  
Test Methods ◽  
Long Term Stability ◽  
Friction Disk ◽  
The Individual ◽  
And Control ◽  
Selection Of

Abstract Stepless vehicle drives will assume their place next to automatic switching units throughout the world if they meet their expected fuel-saving potential. This necessitates optimizing the individual components of the CVT as regards their efficiency. The main source of losses are the hydraulic supply units and the losses which result specifically from non-positive transmission. In the case of stepless chain conveners, these result mainly from friction disk deformation. These losses account for 50 to 70 % of total CVT losses. Both loss components are influenced by the lubricant to a significantly greater extent than it would appear at first sight: In the case of fully-hydraulic clamping and control systems, the viscosity and its long-term stability determines the degree of leakage losses and therefore the size of the pump or pump combinations. This applies to pressure levels between 20 and 40 bar. This in turn is directly proportional to the hydraulic losses on the CVT. The friction coefficient of the lubricant determines the level of the necessary clamping forces. These are responsible for friction-disk deformation. Also of importance as far as the selection of lubricant is concerned is its influence on the CVT service life. The critical service life limits for chain converters are chain breakage (not the subject of this report) and evidence of wear, i.e. grey staining, sheave-grooving, pitting, scoring and rocker pin wear. Standardized test methods exist at P.I.V. for both wear manifestations and for the friction coefficient, these tests allowing a targeted selection of lubricants.

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