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Soil Testing Statutory Fertiliser Analysis


Kent Scientific Services, a Public Analyst Laboratory, selected a Stuart STR4 rotator from Bibby Scientific (UK) to meet the requirements of its fertiliser enforcement analysis work. The prescribed analysis methods for checking the nitrogen and phosphorus content in fertiliser samples require flasks to be mixed end-over-end at 35–40rpm, faster than many other rotators can achieve.


Nitrogen (N), Phosphorus (P) and Potassium (K) are the three primary nutrients needed in large quantities by plants. Manufactured fertilisers, used to supply crops with nutrients the soil lacks, have to be labelled with three figures indicating their NPK content. The Fertilisers (Sampling and Analysis) Regulations 1996 require the figures to be checked by standardised analysis techniques. Kent Scientific Services, one of 18 Public Analyst Laboratories in England, provides scientific and calibration services for local authority enforcement agencies, including analysis of fertiliser samples collected by local Trading Standards officers from manufacturers’ premises or at the point of sale.


David Heath, Quality Manager/Toxicology Manager at Kent Scientific Services, commented on the role played by the Stuart STR4 rotator in the laboratory’s fertiliser analysis work: ‘When our old rotator broke down we needed to find a new one capable of providing the rotation speed specified by the regulations. The prescribed analysis methods for soluble N and P require fertiliser samples to be mixed with 400ml of water in a volumetric flask and mixed by end-over-end rotation at 35–40rpm. The speed we needed was well within the range offered by the STR4. The Bibby Scientific engineering department were very helpful to us, adjusting the bracket on the rotator so that it would work with the large 500ml flasks we need to use. They also extended the length of the bar so that we can mix four rather than two 500ml flasks at once, enabling a control to be processed alongside three samples.


The STR4 incorporates a useful timer, which we set in order to mix the fertiliser samples for precisely 30 minutes, as specified in the regulations.’


The Stuart STR4 drive unit is highly versatile, accepting a choice of five drums designed to take test-tube holders, plates, racks of microcentrifuge tubes, conical flasks, reagent bottles, or jars and paint tins up to 200mm in length and 120mm diameter. The rotation speed is variable from 6 to 60rpm for a range of mixing applications, and the unit can be run in continuous operation mode or with the analogue timer set for 10 to 60 minutes.


Reader Reply Card no 90 New Molecular Tools to Assess Water and Soil Quality With the Water Framework Directive imposing its goal of “good ecological status” and the government pushing for a “sustainable” environment, EnPrint® Ltd is perfectly


placed to provide a solution to these challenges. EnPrint, a spin out company from the Scottish Crop Research Institute (SCRI) in Invergowrie near Dundee, is developing novel molecular tools to assess water and soil quality. By applying a molecular approach, the EnPrint diagnostics identify key target microorganisms in water that enable the classification of water bodies. The technology is state-of-the-art and offers high throughput, accurate and sensitivity advantages over the current, more traditional microscopic methods of identification and classification.


By working closely with industry partners including environment agencies, the EnPrint tools are currently being tested for their suitability as part of the Water Framework ecological monitoring toolkit.


Being a platform technology, these diagnostic tools are applicable to any situation where microorganism or pathogen populations require detection, identification and/or quantification. An area of current interest is as a screening methodology for detection of pathogens in water treatment facilities.


Reader Reply Card no 91 Measuring Particle Size in Marine Sediments


Thanks to its versatility, the Mastersizer 2000 particle size analyser from Malvern Instruments (UK) installed in the School of Natural Sciences at Trinity College Dublin (Ireland) is proving to be an essential tool for a number of different research groups whose projects range from particle sizing in marine sediments to the investigation of storm drains - and even analysing dust from the university library.


Dr Robin Edwards, Senior Lecturer in Earth Sciences, feels that a major advantage of the Mastersizer 2000 is that it provides a readily reproducible and automated approach to particle sizing.


“We chose the Mastersizer 2000 because of its good reputation, its broad measurement range and the fact that it is


used internationally by many institutions, which assists sample comparability,” said Dr Edwards. “For example, before purchasing our own system, we ran samples on a Mastersizer 2000 at the National Oceanography Centre in Southampton. When we analysed the same samples on our own system we found excellent agreement with the original data.”


“Automation is also a key factor,” continued Dr Edwards, “and we use the system’s autosampler for virtually every run.” Reader Reply Card no 92


For most of the sediment-based applications, the research teams are interested in broad classifications, and in some marine applications particular size classes are diagnostic. A number of projects are nearing completion with publications in the pipeline.


Irrigation NewSM300 Soil Moisture Sensor


Research grade sensor for soil moisture and temperature


• Dependable accuracy + 2.5% • Minimal soil disturbance • Good temperature and salinity stability


Delta-T Devices Ltd www.delta-t.co.uk


Reader Reply Card no 94 New Purge and Trap Autosampler


EST Analytical (USA) is proud to offer the EST CenturionWS 100 position water/soilpurge and trap autosampler. Designed for high throughput environmental and municipal laboratories, the Centurion was developed to give maximum sampling flexibility at an affordable price.The ability to process and deliver samples to two different concentrators and the unique and precise Internal Standard delivery system make the Centurion WS the most technically advanced purge and trap autosampler. The Centurion’s hot water rinse capability and PEEK™ sample pathway provides superior analytical performance and productivity.


Reader Reply Card no 95


Mastersizer systems from Malvern Instruments are the laser diffraction systems of choice for a wide range of research and industry applications. With a broad measurement range (0.02 to 2000 microns), easily interchanged dispersion units for wet and dry analysis, and a unique user-configurable software interface, it is simple to operate and highly productive. Standard operating procedure (SOP) driven analysis provides full automation, facilitates method transfer and sets the benchmark for instrument-to-instrument reproducibility.


Reader Reply Card no 93


IET November/December 2010


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