The Evidence Guide describes the underpinning knowledge and skills that must be demonstrated to prove competence.
Critical aspects of competency
Competency must be demonstrated in the ability to perform consistently at the required standard. In particular, the assessor should look to see that the candidate can:
use balances and volumetric glassware appropriately
select and use primary and secondary standards appropriately
select and use indicators appropriately
select and care for electrodes appropriately
perform QA checks for solution performance (for example, enzyme activity, ferric chloride for phenolic solutions, isotonicity for saline)
perform titrations using laboratory procedures with required accuracy and precision and within required timelines
calculate the concentration of the solution given the chemical reaction for the titration
recognise control results that are not within acceptable range
record results to enterprise standards
label and store solutions in accordance with enterprise procedures
interpret and follow enterprise standard operating procedures (SOPs)
interpret and use safety information, such as that provided by material safety data sheets (MSDSs) and follow relevant safety procedures.
Underpinning knowledge
Competency includes the ability to apply and explain:
solution terminology, chemistry of acids, bases, buffers, redox reactions and complexometric reactions
grades of glassware, reagents and their use
reactions used for standardisation and desirable characteristics
determination of equivalence points using indicators and graphical methods
calculation methods, including appropriate units, uncertainties and balancing equations
enterprise communication and reporting procedures
OHS procedures, including those for using corrosive materials
relevant health, safety and environment requirements.
Assessment context and methods
This unit of competency is to be assessed in the workplace or simulated workplace environment.
The following assessment methods are suggested:
inspection and/or testing of solutions prepared by the candidate
review of records and workplace documentation completed by candidate
review of work outputs by the candidate over time to ensure accuracy, consistency and timeliness
feedback from peers and supervisors
observation of the candidate preparing, standardising and using a range of solutions
oral or written questioning.
In all cases, practical assessment should be supported by questions to assess underpinning knowledge and those aspects of competency which are difficult to assess directly. Questioning techniques should suit the language and literacy levels of the candidate.
Interdependent assessment of unit
This unit of competency may be assessed with:
PMLTEST400 and PMLTEST500 series units dealing with sampling, tests and measurements.
Resource implications
Resources may include:
standard laboratory equipped with appropriate volumetric equipment
laboratory reagents and equipment
standard operating procedures (SOPs) and testing methods.
This competency in practice
Manufacturing
A standard solution is used to determine the concentration of unknown solutions. The quality of these analyses is critically related to the accuracy with which the concentration of the standard solution is known. Therefore, laboratory technicians spend considerable effort to ensure that the materials and methods used for the preparation and standardisation will lead to a solution of accurately known concentration. For example, anhydrous sodium carbonate is often used to prepare solutions to determine the concentrations of acids. The sodium carbonate is heated at a suitable temperature to remove any trace of moisture and cooled in a dessicator. An appropriate quantity is dissolved in distilled water and made up to volume in a volumetric flask. This solution of known concentration is then titrated with acids of unknown concentration and the concentration of the acids determined.
Biotechnology
A technical officer arrived at work on Monday morning and discovered that the freezer had been turned off over the weekend and the restriction nucleases had thawed. These enzymes were to be used that morning. The technician needed to check the enzyme activity to determine whether the enzymes had been denatured by the rise in temperature. The technician quickly set up a digestion mix of affected enzyme with some viral DNA of known sequence. The digest produced DNA fragments of expected length, showing the enzyme still had activity. The technician reported the incident along with the results to the supervisor, who decided that the enzymes could be used for that day.
Environmental
A laboratory technician was required to determine the total acidity of a water sample as part of a quality control program. The total acidity was measured by titrating the water sample with sodium hydroxide of known concentration using an appropriate indicator. The concentration of the sodium hydroxide was determined via a volumetric titration against a primary standard of potassium hydrogen phthalate.
The value of the total acidity was determined by multiplying the volume of sodium hydroxide used with a numerical 'factor' which had been determined by the laboratory supervisor in order to save time. The value of the 'factor' was displayed on the titration equipment. However, a new technical assistant did the full calculation and found that his/her result differed slightly from that obtained using the 'factor'. After discussion with the laboratory supervisor it was agreed that the error was in the 'factor' and the assumption that each new batch of sodium hydroxide prepared was exactly the same concentration as all previous batches. This was incorrect as the concentration of each batch differed slightly and its actual concentration was determined accurate, using the primary standard. The procedure was changed so that the full calculation was required for all tests.
Key Competencies
The seven key competencies represent generic skills considered for effective work participation. The bracketed numbering against each of the key competencies indicates the performance level required in this unit. These are stand-alone levels and do not correspond to the Australian Qualifications Framework (AQF).
Level (1) represents the competence to undertake tasks effectively
Level (2) represents the competence to manage tasks
Level (3) represents the competence to use concepts for evaluating and reshaping tasks.
Collecting, analysing and organising information | Communicating ideas and information | Planning and organising activities | Working with others and in teams | Using mathematical ideas and techniques | Solving problems | Using technology |
Level 2 | Level 2 | Level 2 | Level 2 | Level 2 | Level 2 | Level 2 |