Results obtained from the years 2012 to 2021 for the headquarters and all the branches. Table 1 shows all the results of the Z-score. In general, results were obtained based on 2 sets of samples in each batch, which differentiate by numbers 1 and 2. The provider will send the same sample to calculate the within labs Z-score to make sure the sample was homogenous, and a different batch of sample to calculate the between labs Z-score. Table 1 shows the Z-score between labs.
For the year 2021, the Terengganu branch did not submit the result due to the instrument breakdown. While the other three branches such as Perak, Pahang, and Sibu have a choice whether to participate or not within three years. A minimum requirement for participating in the PT scheme was valid for one accreditation cycle in 3 years. However, starting in the year 2023, Standard Malaysia will implement a five-year accreditation cycle [2]. That was an option for the lab to choose the PT scheme alternately. Nevertheless, the lab shall maintain the competency internally if they are not joining the PT program.
Over 10 years of results, only the year 2012 faced the outlier results, which one sample from the Malacca branch and two questionable results from Bintulu and Sibu branches for the year 2016. After investigation, it was found that the outlier was due to a careless mistake done by the officer. The officer keyed in the data wrongly. This scheme came with 2 parameters BA and SA, the officer keyed in the SA result to the BA column and the BA result to the SA column. The main reason is working at the last minute and not having time for the supervisor to check and review the results. After that, instructions are made for all branches not to postpone work. Turnaround time of the task needs to report weekly.
For the questionable results in the year 2016, no investigation was done. Referring to the old version of the department's policy, no action should be taken for questionable results, only outlier results should be investigated. Therefore, further improvements were made to add a policy to view questionable results in 2017, for preventive action. Started 2017 onward, all the laboratories took preventive action for all questionable results including the quality control data and PT schemes.
According to Eurachem [3], when a laboratory's results in a PT scheme are not satisfactory, management might investigate potential improvement areas for future testing. There are several possibilities, including adding more operator training, using new or altered testing methodologies, enhancing data quality control, and upgrading, calibrating, or replacing equipment. Consistently look into the error using the following 4 categories: manpower, method, material, and machinery (4M).
Referring to Figure 3 shows all the trends of PT performance from the years 2012 to 2021; the discussion was based on 4M which covers manpower, method, machine, and material.
i. Manpower:
The personnel attitude was the most concerning part. Even though the competency was done but still might happen a random error which unexpectedly. Thus, carelessness and cheating might happen if the personnel mindset was out of quality. Continuously training and awareness were the main activities to cultivate a quality attitude. The provider’s instruction mentioned the responsibility of the participating laboratories to avoid collusion or falsification of the results. Caution is also very important to avoid mistakes, any alteration of results by participants after the closing date will not be accepted and entertained. Such as wrongly placing the decimal points or calculation errors; key in the result mistakenly. Some participants would blame the software problem such as corrupt drivers or Malware attacks but the provider did not accept this accusation. Any result submitted was the final decision. The investigation outlier result was the response by the participant after receiving the final report from the PT provider. Calculation errors are an additional example of human error. It addresses incorrect formula entry, which is classified as a human error rather than a software problem [4].
ii. Method:
The method used for determining the BA was referred to the Journal of Association of Official Analytical Chemists (JAOAC) Volume 70, Issue 5, 1987: Reverse-phase liquid chromatographic determination of benzoic and sorbic acids in foods [5]; laboratory applied together with the steam distillation technique and further improved by direct extraction. The lab used both methods until 2010 and maintained the direct extraction until now. Analysed the BA by high-performance liquid chromatography (HPLC) using an isocratic reverse phase liquid chromatography for the simultaneous determination of BA & SA. It applies to a wide variety of foods at a level up to 8000 mg/kg for SA and 15 000 mg/kg for BA. Based on the performance of the PT, the method used for BA determination is not an issue, validation is done to ensure the characteristic performance achieved. Add on verified periodically by different personnel and still obtained the results within the acceptance range is sufficient to prove this method fit for intense purpose. Communication with the customer for method declaration is added value to support the method.
iii. Machine:
The machine covers measuring equipment such as balance and analytical equipment such as HPLC. Calibration of the measuring equipment was done by the competent and certified laboratory; the chemistry department has its calibration team which runs through HQ and all branches follow the schedule. The scope that covered by the team is mass, heat, and temperature.
As mentioned in the Method, the analytical instrument used by the lab was the HPLC which consists of the solvent delivery system, autosampler injector, data station, and multiwavelength detector completed with the reverse-phase C18 columns and protected by the pre-column which the lab was using the Guard-Pak holder. Sample preparation for the steam distillation method used the distillation unit whereas, for the direct extraction, the lab uses the vortex mixer. A maintenance program was established and the lab complied with the clause of ISO 17025. Permanent and thorough maintenance is needed for an old version of the instrument, especially the old lab which no extra money allocation for a new version of the instrument, thus continuous monitoring is important until the spare part is out of stock or not worth repair then need to allocate a new version of the instrument. So far, the instrument is more than 20 years will propose to dispose of it and purchase a new unit. Anyhow the condition of the instrument will be considered and justified whether to replace it or not. For anything involving budget allocation, top management emphasized the need for it. Especially the government laboratory which uses the people’s money.
iv. Material:
For the early version of ISO 17025, the measurement traceability is not as thorough as the new version 2017, which includes Annex A as the extension elaboration for the metrological traceability. Meaning that the metrological traceability of its measurement results by a documented unbroken chain of calibrations, each contributing to the measurement uncertainty, linking them to an appropriate reference is much more important now. The lab was encouraged to use the certified reference material for metrological traceability. The clarity provided that traceability to SI may be achieved through the use of certified reference materials. The practice of using RM to comply with ISO started in the year 2006 when all the RM distribute by HQ. All the branches were requested and updated their list of RM and stored the RM following the instruction. Expired RM shall be disposed of or resend back to HQ for reverified.
For the normal distribution, the results curve oscillates in a random way around the target value, in which the Z-score =0 and within the control limit (< 2) as shown in Figure 4. It means that the process is under control. The results are reliable and accurate. For the other nine branches show the same trends as the HQ, such as the Penang branch shown in Figure 5.
Based on figure 6, Z-score for the Sarawak branch tends to be over 0 which all the points falling on the upper side, which shows that systematic error occurred. To improve the accuracy of the lab, the investigation needed in various aspects: the lab needs to check on the temperature used, tolerance of the equipment especially the automated pipette used for the sample sub-sampling; autosampler errors and peak integration by the analytical instrument.
The relationship between the 4M is always mutually beneficial, lacking one will not guarantee high quality. Exploring these 4M provides the lab with a structured framework for root cause analysis by helping the lab to understand how each one may have contributed to a particular issue. The structure brings in identifying sources of variation, root causes of problems, or improvement opportunities is invaluable as a core element of problem-solving.
