Search

There is an increasing need for laboratory capacity building through the organisation of proficiency testing programmes with metrologically traceable reference values in the Asia-Pacific region. Stakeholders such as the regional metrology organisation, metrology institutes, and accreditation bodies are increasingly aware that consensus values of proficiency testing programmes could sometimes be significantly biased if the participating laboratories do not have clear understanding of their measurement capabilities and measurement uncertainties. In this article, we provide a review of the effectiveness of the use of reference values obtained from international comparisons among metrology institutes for performance evaluation in associated proficiency testing programmes. Important issues are discussed including determination of assigned values, the main methods employed by national metrology institutes/designated institutes and field analytical laboratories for analysis, estimation of measurement uncertainty, and guidance on analytical challenges presented by these studies. Application of measures such as appropriate matrix reference materials, particularly from incurred sources, for assessing extraction efficiencies and other measurement procedural issues, and proper knowledge of the uncertainty budgets are essential tools leading to effective and reliable measurements.

APMP.QM-S10 was coordinated by Government Laboratory, Hong Kong SAR (GLHK) under the auspices of the Inorganic Analysis Working Group (IAWG) of the Comité Consultatif pour la Quantité de Matière (CCQM). Fourteen national metrology institutes (NMIs) or designated institutes (DIs) registered for the examination of zinc, manganese, calcium and magnesium. All institutes submitted the results for zinc and manganese, and twelve institutes submitted the results for calcium and magnesium. The supplementary comparison was designed to enable participating institutes to demonstrate their measurement capabilities in measuring the mass fractions of the analytes at mg/kg levels in a test sample of food supplement by various analytical techniques. For examination of zinc, manganese, calcium and magnesium, most of the participants used microwave-assisted acid digestion methods for sample dissolution. A variety of instrumental techniques including inductively coupled plasmas mass spectrometry (ICP-MS), isotope dilution inductively coupled plasmas mass spectrometry (ID-ICP-MS), inductively coupled plasmas optical emission spectrometry (ICP-OES), flame atomic absorption spectrometry (FAAS), and instrumental neutron action analysis (INAA) were employed by the participants for determination. For this supplementary comparison, inorganic core capabilities have been demonstrated by the concerned participants with respect to methods including ICP-MS (without isotope dilution), ID-ICP-MS, ICP-OES, FAAS and INAA on the determination of elements (zinc, manganese, calcium and magnesium) in a food matrix of food supplement. Generally, the participants' results of APMP.QM-S10 were found to be consistent for all measurands according to their equivalence statements. Except with some extreme values, most of the participants obtained the values of d i/U(d i) within ± 1 for the measurands. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

This paper compares reference values assigned by isotope dilution mass spectrometry with participants’ consensus values in a small-scale proficiency test (PT) on the determination of residues of organochlorine pesticides (α-endosulfan, β-endosulfan and endosulfan sulfate) in a tea sample. The PT was specifically organized to benchmark the technical capability among the local participating laboratories in Hong Kong providing pesticide testing service to their customers and to identify possible areas for further improvement. Participant’s performance, based on z-score, was evaluated using consensus values and standard deviation that was estimated from the Horwitz function. Two out of the seven participating laboratories were identified to produce either questionable or unsatisfactory results (in terms of z-scores), showing that the performance of the majority was satisfactory. However, the number of questionable or unsatisfactory results increased to three if the consensus values were replaced by assigned reference values derived from gas spectrometry-isotope dilution mass spectrometry with higher metrological traceability than those used in obtaining the consensus values. Though the said PT program was fit for its intended purposes at that point of time, revisiting the program explicitly demonstrates the significant importance of assigned reference values in achieving reliable assessment in reality. Unless the bias of consensus values is known with metrological traceability, PT scheme providers should be cautious in assessing the competence of participating laboratories using consensus values particularly in small-scale inter-comparison programs. The importance of pre-wetting dry tea samples to improve recovery of pesticide residues is also noted.

Food authenticity such as illegal substitution of frozen meats for fresh meats is one of the public concerns within the food authorities, industry, and consumer groups. An enzymatic method based on the activity of β-hydroxyacyl-CoA-dehydrogenase was used aiming to differentiate between fresh/chilled and frozen pork meats. The β-hydroxyacyl-CoA-dehydrogenase activity for meat samples was respectively determined as received (X0) and after a frozen (for 72 h at –18°C) and thawed cycle (X1). A database of the R1 values (X0/X1) was established from the measurement of β-hydroxyacyl-CoA-dehydrogenase activity of authentic fresh, chilled and frozen meats. Results showed that the R1 values were normally distributed after taking a natural logarithm and were independent on the positions where the porcine samples were taken from the carcasses. The R1 values were significantly higher for frozen meats than others due to the increased release of β-hydroxyacyl-CoA-dehydrogenase from damaged cells. When the literature R1 ...

This paper presents the results of a multinational joint proficiency testing (PT) programme on four pesticide residues (cypermethrin, α-endosulfan, β-endosulphan and bifenthrin) in two tea samples. The objectives were to evaluate the performance and to improve the testing capability of field laboratories in the Asia Pacific region for analysis of pesticide residues in tea. A total of 42 laboratories registered for the programme and 32 laboratories from 12 economies returned the results to the organizers. The assigned values of the pesticides were agreed to be the respective weighted mean determined by the three metrology institutes — the National Measurement Institute, Australia (NMIA), the National Institute of Metrology, China (NIM) and the Government Laboratory, Hong Kong (GLHK) in an Asia Pacific Metrology Programme (APMP) pilot study programme (APMP.QM-P15) using the same test materials. The performance of participating laboratories was expressed using the numerical indicators of z-scores and E n -scores. Amongst the reported data, only 35.3% and 35.0% achieved satisfactory z-scores (|z| ≤ 2) and E n -scores (|E n | ≤ 1) respectively. Only two laboratories achieved satisfactory z-scores and E n -scores for all the analytes. The results demonstrated that the performance of the majority of the laboratories participating in this study on the analysis of pesticide residues in tea was not satisfactory, and more capability building is required for further improvement.

A method for the determination of Pb in Chinese herbs based on “approximate matching” isotope dilution inductively coupled plasma mass spectrometry was developed. The method was validated using NIST SRM 1547 (Peach Leaves). Satisfactory analytical figures of merit were achieved, including good sample recovery (∼99%) and low relative expanded uncertainty (less than ±2%). The validated method was applied to the analysis of a herbal sample for the international comparison CCQM-P97. Measurement uncertainty was evaluated according to three approaches, namely Kragten’s spreadsheet approach, GUM Workbench and Monte Carlo method (MCM). A practical way was established for the evaluation of measurement uncertainty based on the propagation of distributions using MCM. The validated method was also employed for the provision of SI-traceable mass fraction of Pb in an in-house herbal reference material and the assignment of a reference value to a proficiency testing programme.

An accurate and precise method for the determination of total 19-norandrosterone (19-NA), a major metabolite of nandrolone, in human urine was developed based on isotope dilution gas chromatography-high resolution mass spectrometry (ID GC-HRMS). The 19-NA glucuronide, together with deuterated 19-NA (d4-19-NA) (as the internal standard, IS), was subjected to enzymatic hydrolysis using β-glucuronidase, followed by solid phase extraction (XtractT, mixed-mode column) and liquid–liquid extraction cleanup. The native and deuterated analogues of 19-NA were then derivatised to the corresponding bis(trimethylsilyl) derivatives using N-methyl-N-trimethylsilyltrifluoroacteamide (MSTFA):NH4I:Dithiothretitol (1,000:2:3 w/w). Identification was achieved under selected ion monitoring of the respective trimethylsilyl derivatives at ion masses m/z 405.26450 and 420.28800 for 19-NA and m/z 409.28920 and 424.31270 for d4-19-NA within the specific time windows (±1% of the relative retention time to the calibration standard). A linear calibration curve (r 2 > 0.9995) was obtained based on seven calibration points (five replicates at each level) in the range 0.05–10 ng/g. The detection limit for 19-NA was found to be 4 pg/g. The method has been applied for the determination of 19-NA by fortifying 19-NA glucuronide at three concentrations (0.2, 2.1 and 7.2 ng/g) in blank urine samples with excellent accuracy and reproducibility. To circumvent the iterative process of exacting matching, a single-point calibration procedure was adopted, where the acceptance criteria for the isotopic ratio in the sample (RF s) and calibration blends (RF c) was set close to unity (0.95–1.05). This method was successfully applied in a pilot inter-comparison study, with results in good agreement with the fortified value and other participants’ results (relative standard deviation, RSD

Under the auspices of the Comite Consultatif pour la Quantite de Matiere (CCQM) a laboratory intercomparison, CCQM-P68, was co-ordinated by the National Measurement Institute of Australia (NMIA) in 2005 involving the analysis of the steroid 19-norandrosterone (19-NA) in human urine. 19-NA is the major metabolite of nandrolone, a commonly abused anabolic agent. It is routinely tested by many sports drug testing laboratories and several national metrology institutes have developed reference methods to provide reference values for the certification of reference materials. The material distributed for the intercomparison was a freeze-dried human urine candidate reference material containing 19-NA at a level close to the allowed World Anti-Doping Agency (WADA) cut-off for this anabolic agent, i.e. 2 ng/ml. Four national/designated metrology institutes participated in the intercomparison and their results for this complex analysis were in excellent agreement, with a relative standard deviation (RSD) of only 1.7%. The expanded uncertainties at the 95% level of confidence for the reported results ranged from 3.7 to 7.0% at the 2.15 ng/g level.

An interlaboratory comparison study for the determination of 5 residual organochlorine pesticides (hexachlorobenzene and 4 hexachlorocyclohexane isomers) in ginseng root was performed. This program [Asia Pacific Laboratory Accreditation Cooperation (APLAC) T049] was the first of its kind for an herbal matrix and involved the participation of 70 laboratories from 26 countries worldwide. Consensus mean values were computed statistically from the reported results, which were eventually used to assess the performance of individual laboratories in terms of the z-scores. The distribution of analytical data was found to be widespread, with standard deviation ranging from 43.9 to 55.9%, and the result patterns obtained were similar to those residue pesticide programs using other matrixes. Although the estimation of measurement uncertainty is a crucial requirement for all quantitative tests for laboratories that meet the requirements of International Organization for Standardization/International Electrotechnical Commisssion (ISO/IEC) 17025, some laboratories in this program had difficulties and showed unfamiliarity with respect to that quality criterion. It was recommended that laboratories review and rectify the situation promptly so that they would have a better understanding of measurement uncertainty or the test service provided.

Florfenicol (FFC) residues in foods are regulated as the sum of florfenicol and its metabolites measured as florfenicol amine (FFA). An isotope dilution LC-MS/MS method utilizing phenylboronic acid (PBA) SPE cleanup is established for the accurate determination of FFA in fish muscles (i.e., salmon and tilapia) after acid catalyzed hydrolysis. Comparisons of the PBA SPE cleanup procedure with other cleanup procedures such as mixed-mode cationic (MCX) SPE and solid supported liquid–liquid extraction were performed. Quantification of FFA in fish muscles was accomplished by using matrix-matched calibration with FFA-D3 as the internal standard. The method was validated with FFA fortified fish muscles at three different levels (50, 100, and 200 μg/kg). Conversion of FFC to FFA by acid catalyzed hydrolysis was evaluated and found to be ≥88%. The recoveries of FFA in fish muscles at the three fortification levels ranged from 89 to 106%, and RSDs were ≤9% in all cases. The LOD values in salmon and tilapia muscles were 0.13 and 1.64 μg/kg, respectively. The LOQ values in salmon and tilapia muscles were 0.29 and 4.13 μg/kg, respectively. This method is suitable for the application in routine control of FFC in fishes according to its residue definition.

Liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-MS/MS) was applied to the determination of residual bacitracin A, colistin A, and colistin B in milk and animal tissue samples. Prior to instrumental analysis, samples were subjected to acid extraction followed by solid-phase cleanup using Strata-X cartridges. Mass spectral acquisitions were performed under selective multiple reaction monitoring (MRM) mode at m/z 199 and 670 from triply charged precursors of bacitracin A (m/z 475); m/z 385 and 379 from triply charged precursors of colistin A (m/z 391); and m/z 380 and 374 from triply charged precursors of colistin B (m/z 386). Method precision was evaluated from spike recovery of samples fortified at concentrations corresponding to 2/5 of the maximum residue limits (MRLs) for each of the analytes under study. Intra-day and inter-day variations were found to range from 90.9 to 104% with relative standard deviation (RSD)6.5%, and from 90.1 to 106% with RSD9.1%, respectively. Limits of quantification (LOQs) were defined as the spiking concentrations at 2/5 MRL, and limits of detection (LODs) were 10-47 microg kg(-1) for bacitracin A, 1-16 microg kg(-1) for colistin A, and 6-14 microg kg(-1) for colistin B in milk and animal tissues. The presented method has good precision and high sensitivity and was applied as a fast screening protocol and a quantitative tool for monitoring of the concerned polypeptides in foods as part of a surveillance program.

A headspace solid-phase microextraction and gas chromatography–mass spectrometric (HS-SPME-GC-MS) method was developed to monitor methylamine (MA), dimethylamine (DMA) and trimethylamine (TMA) in fish. The alkylamines were extracted using carboxen/divinylbenzene/polydimethylsiloxane (CAR/DVB/ PDMS) fibres at 25 °C and exposure time of 5 min. Calibration curves showed good linearity in the concentration range of 0.5–10 μg ml−1 and the corresponding coefficients of correlation were all above 0.99. Detection limits were estimated to be 0.10 μg ml−1 for MA and DMA; and 0.15 μg ml−1 for TMA. Intra-day and inter-day variation of spike samples at 2.0 μg g−1 were 4.3–6.2% and 5.4–10%, respectively. Recovery of the method for TMA was found to be comparable to that of a standard titration method with the mean deviation of the two methods being 6.7%. The validated method was applied to study the decay profiles of the concerned alkylamines in two fish species that were stored at 0 and −20 °C; and the results obtained were compared with that obtained by using the classical parameter of total volatile basic nitrogen (TVBN).

A sensitive and reliable method for detection of irradiated chicken, pork and mangoes is described. The method involved a derivatisation treatment of irradiation markers—2-dodecylcyclobutanone (2-dDCB) and 2-tetradecylcyclobutanone (2-tDCB) with pentafluorophenyl hydrazine (PFPH) and detection by gas chromatography-mass spectrometry (GC-MS). Samples were first subjected to Soxhlet extraction with n-hexane and purified by passing through Florisil columns according to EN1785 method. Then, the extracted 2-dDCB and 2-tDCB were derivatised with PFPH in acidic buffer for 60 min at ambient temperature (∼25 °C). Identification of the derivatives was confirmed by the presence of two characteristic and dominant ion fragments at m/z 249 and [M-54], each within the specified retention time windows, and matching of the relative intensities of these ions with those of the standards under SIM mode. The relative standard deviation (%RSD) of the ion ratios of m/z 249 to that of [M-54] for all the food matrices under study (2.96–3.06 for PFPH-dDCB; and 2.69–2.83 for PFPH-tDCB, respectively) were ≤10%. Mean spike recovery of the derivatization process, with %RSD ≤20%, ranged from 68.6% to 71.4% and 57.9% to 70.8% for PFPH-dDCB and PFPH-tDCB respectively. The limits of detection (LODs) were estimated to be 0.01 μg/g. The present method was applicable to detect food samples that had received irradiation doses at 1–5 kGy. The quantity of equivalent 2-dDCB and 2-tDCB in the concerned foods was found to be proportional to the irradiated dose received.

The application of electron paramagnetic resonance (EPR) spectroscopy to the detection of irradiation treatment of bones of chicken, pork, beef, lamb, fish and mollusk shells was described. Induced radicals in irradiated samples gave distinguishable EPR patterns for differentiation from the unirradiated samples. The EPR signals were found to be relatively stable in mammalian bones and mollusk shells; but significant loss was observed in fish samples. Dose–response relationships of the samples were found to be linear at 0–5 kGy range (r2>0.95). Using calibration curve method, the irradiation status of all the 64 blind samples (14 unirradiated and 50 irradiated) was correctly identified. The estimation of irradiation doses was satisfactory with mean values ranging from 86 to 116% of those of the nominal values, and precision (%RSD) ranged from 15 to 29%. The validated analytical procedure was applied in the surveillance monitoring of about 400 food samples during the period of 2001–2004.

A selective and sensitive liquid chromatography tandem mass spectrometric (LC–MS/MS) method has been developed for simultaneous determination of residual bacitracin and colistin in bovine milk samples. Milk samples were deproteinized and extracted with a mixture of trichloroacetic/formic acid. After centrifugation, bacitracin and colistin in the extracts were separated on a reversed phase Alltima BDS C 18 column (250 mm × 2.1 mm, 5 μm) using a gradient elution programme of ammonium formate buffer (saturated ammonium formate:formic acid:acetonitrile:water, 1:5:50:950, v/v/v/v) and 0.1% formic acid in acetonitrile at 0.2 ml min −1 . Using electrospray LC–MS/MS with time-scheduled multiple reaction monitoring (MRM), identification and quantification of the major components of the two polypeptides were performed based upon the intensities of mass fragments from the respective doubly charged precursor ions: bacitracin A at 712 → 199 amu and 712 → 227 amu, and colistin A at 586 → 101 amu, 586 → 202 amu and 586 → 241 amu, respectively, at the defined retention time windows and the matching of the specific tolerance of the relative abundance of the monitored ions. Polymyxin B, a polypeptide of colistin family, was employed as the internal standard. With an additional solid phase extraction procedure, the analytical method was applicable to the analysis of the two polypeptide antibiotics in animal's liver and tissue samples. The practical quantification limits of bacitracin A and colistin A were 100 and 50 μg kg −1 ; and mean intra-day ( n = 7) and inter-day ( n = 4) recoveries were in the range of 89.2–110% (R.S.D.

A sensitive and selective method using gas chromatography–electron capture negative ionization mass spectrometry (GC–ECNI-MS) for analysis of dimetridazole (DMZ) and metronidazole (MNZ) in poultry muscles, porcine kidney and liver, and chicken liver, was developed and validated for the purpose of food surveillance testing of the residues of these two nitroimidazoles in various types of animal tissues in the Hong Kong Special Administrative Region. Before homogenization and extraction with toluene, [2H3]dimetridazole-(DMZ-d3) and secnidazole (SNZ) were added to tissue samples as internal standards. The organic extracts were mixed with n-hexane and subject to solid-phase extraction cleanup by amine extraction columns. MNZ and SNZ were derivatized with BSA prior to GC–ECNI-MS determination. Good recovery and precision were obtained and the limit of detection was below parts per billion levels for poultry and porcine tissues. The method could also be applied for the detection of the hydroxylated metabolite of DMZ.

A simple, selective and sensitive method for simultaneous determination of lincomycin (LCM) and virginiamycin M 1 (VGM) in swine muscle and organs using liquid chromatography with electrospray ionization tandem mass spectrometry is presented. Acetonitrile was used to extract the analytes from the samples. Lipids in the extracts were removed by liquid–liquid partition with n -hexane. Analytes in the purified acetonitrile extracts were separated by liquid chromatography with a reversed-phase Hypersil BDS C 18 column (250 mm × 2.1 mm, 5 μm) under gradient elution of an ammonium formate buffer (saturated ammonium formate:formic acid:acetonitrile:water, 1:5:50:950, v/v) and 0.1% formic acid in acetonitrile at 0.2 mL min −1 . Identification was performed by monitoring two pairs of multiple reaction monitoring ions from the parent ions ( m / z 407.2→126.1 and 407.2→359.2 for LCM, respectively, and m / z 526.3→508.3 and 526.3→355.1 for VGM, respectively) at the defined retention time windows and by matching of the specific tolerance of relative abundance of major ions as stated in the European Union Commission Decision 2002/657/EC. Quantification was based on the relative ratios of the sum of peak areas of major ions of the analytes to those of clindamycin (internal standard) with reference to the respective ratios of the calibration standards. The method was validated by determining and evaluating the accuracy and precision of the intra-day and inter-day repeatability at two independent spike levels and the trueness of measurements on analysis of quality check samples. The limits of detection in different matrices were found ranging from 0.6 to 1.5 μg kg −1 and 1.9 to 4.3 μg kg −1 for LCM and VGM, respectively.

A high throughput thermal gravimetric method was developed to measure the carbonaceous aerosols and particulates collected on filters. Representative portions or the whole piece of a loaded or blank filter was sampled and conditioned at 105±5 °C for 4 h to drive away water moisture. The sample was then treated at 550±10 °C for 4 h. After each of the heat treatment steps, the sample was conditioned in a humidity and temperature-controlled cabinet for 12 h till constant weight. The weight of the filter before and after the heated treatment was measured and the weight difference between the treatment at 550 and 105 °C was calculated as the weight of the carbon containing substances (CCS). Reference chemical standards and certified reference materials SRM 1649a and 1650a were used to validate the method. CCS concentrations of real aerosol samples collected in the city of Hong Kong during the summer of 2001 were also measured, compared and correlated with the concentrations of total carbon (TC), elemental carbon (EC) and organic carbon (OC) of the samples determined using a thermal optical transmittance (TOT) method as specified in NIOSH method 5040. The weight of organic compounds in airborne particulate matters is usually estimated by multiplying the weight of TC, which is determined by thermal/thermal optical methods, by a factor of 1.2 or 1.4. To this end, a correction factor of approximately 1.6 was found to relate TC to the measured values of CCS in aerosol samples collected in the urban atmosphere of Hong Kong. The proposed procedure for measurement of CCS is simple, easy to follow and requires simple laboratory instrumentation. Typically, the analysis of more than 100 filter samples can be completed within three working days with minimal attention.

A sensitive and robust method using isotope dilution gas chromatography–electron capture negative chemical ionization mass spectrometry (GC–ECNI-MS) was developed and validated for the analysis of quinoxaline-2-carboxylic acid (QCA) in porcine liver. [ 2 H 4 ]QCA was added to liver samples which were then deproteinated with 2% metaphosphoric acid in 20% methanol. Followed by sequential extraction with water-saturated ethyl acetate and phosphate buffer, the buffer extracts were subject to solid-phase extraction clean-up by mixed mode anion-exchange columns. QCA was derivatized with N -methyl- N - tert -butyldimethylsilyltrifluoroacetamide (MTBSTFA) prior to GC–ECNI-MS determination. For unambiguous identification, a second GC–ECNI-MS experiment was performed on suspected positive samples which were derivatized independently with another derivatization agent, trimethylsilyldiazomethane. Excellent recovery and precision were obtained and the limit of quantitation was 0.7 μg/kg (S/N>60). Method ruggedness by Taguchi orthogonal array technique is also presented.

This article discusses the development of various analytical methods for identification and quantification of residues of antibiotics in meeting international regulatory requirements, and, as an example, overviews the screening, purification, fractionation and analytical assays of bacitracin, a commonly applied polypeptide antibiotic mixture. Attention is focused on the development of chemical methods, as they provide extraordinary performance, in terms of sensitivity and selectivity, for measuring residual levels of the various components of bacitracin in food and other matrices; the non-compound specific biological assay is discussed only briefly. Because of its advantages, state-of-the-art high-performance liquid chromatography (HPLC) coupled with various detection techniques, in particular mass spectrometry (MS), has recently gained in popularity in confirming and quantifying drug residues. In this article, the authors also outline the latest results on the application of highly sensitive and selective LC-MS in analysis of bacitracin residues in milk and animal tissues. LC-MS is suggested as the technique of choice for confirmation of polar polypeptide antibiotics and the like at trace concentrations.

A comparative survey of indoor and outdoor air quality (AQ) for an enclosed (GL1) and a semi-enclosed (UST1) car park in Hong Kong was conducted from August to December 2000. Seventy-two canister samples were col lected and analysed for one hundred C3-C12 volatile organic compounds (VOCs) by gas chromatography/ mass spectrometry. Carbon monoxide (CO), carbon dioxide, temperature, relative humidity and particulate matter were also measured. The CO levels at GL1 com plied with local AQ objectives for Indoor Car Parks and ASHRAE guidelines, but were more than double those of the outdoor air. The PM10 and PM2.5 concentrations were also found to be higher in the indoor environments. High mass fractions of aliphatic and aromatic compounds detected at GL1 showed that fuel evaporation and motor vehicular exhaust were the major contributors to the VOCs. In addition, the number and abundance of VOC species were higher in the enclosed environment than outdoors. The high indoor/outdoor (I/O) AQ ratios and poor I/O correlations at GL sites showed that the existing ventilation system at the site was inefficient. Enclosed car parks with their intrinsic source emissions are unlike other indoor public places. The CO and VOC pollution coupled with insufficient ventilation, as in this study, make them potentially hazardous to users. The composi tion of gasoline on sale locally was studied to shed light on the VOC composition in the car park environments. In addition, the sources of isoprene in the enclosed car parks were explored in a correlation study.

The key comparison CCQM-K126 low polarity organic in water: carbamazepine in surface water was coordinated by Government Laboratory Hong Kong under the auspices of the Organic Analysis Working Group (OAWG) of the Comité Consultatif pour la Quantité de Matière (CCQM). Eight National Metrology institutes or Designated Institutes participated and participants were requested to report the mass fraction of carbamazepine in surface water study material. The surface water sample was collected in Hong Kong and was gravimetrically spiked with standard solution. This study provided the means for assessing measurement capabilities for determination of low molecular weight analytes (mass range 100-500) and low polarity (pKOW ⩽ −2) in aqueous matrix. Nine NMIs/DIs registered for the KC and one withdrew before results were submitted. Nine results were submitted by the eight participants. Eight results applied the LC-MS/MS method and Isotope Dilution Mass Spectrometry approach for quantification. BAM additionally submitted a result from ELISA that was not included in the key comparison reference values (KCRV) calculation as is provided in the report for information. One further result was not included as the participant withdrew their result from the calculation after further analysis. The assigned KCRV was the median of the seven results and was assigned a KCRV of 250.2 ng/kg with a combined standard uncertainty of 3.6 ng/kg, The k-factor for the estimation of the expanded uncertainty of the KCRVs was chosen as k = 2. The degree of equivalence (with the KCRV) and its uncertainty was calculated for each result. Seven of the participants were able to demonstrate the ability to quantitatively determine low-polarity analyte in aqueous matrix by applying LC-MS/MS technique at a very low level. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

This paper presents the certification of alpha-endosulfan, beta-endosulfan, and endosulfan sulfate in a candidate tea certified reference material (code: GLHK-11-03) according to the requirements of the ISO Guide 30 series. Certification of GLHK-11-03 was based on an analytical method purposely developed for the accurate measurement of the mass fraction of the target analytes in the material. An isotope dilution mass spectrometry (IDMS) method involving determination by (i) gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS) and (ii) gas chromatography-electron ionization-high-resolution mass spectrometry (GC-EI-HRMS) techniques was employed. The performance of the described method was demonstrated through participation in the key comparison CCQM-K95 "Mid-Polarity Analytes in Food Matrix: Mid-Polarity Pesticides in Tea" organized by the Consultative Committee for Amount of Substance-Metrology in Chemistry in 2012, where the study material was the same as the certified reference material (CRM). The values reported by using the developed method were in good agreement with the key comparison reference value (KCRV) assigned for beta-endosulfan (727 ± 14 μg kg(-1)) and endosulfan sulfate (505 ± 11 μg kg(-1)), where the degree of equivalence (DoE) values were 0.41 and 0.40, respectively. The certified values of alpha-endosulfan, beta-endosulfan, and endosulfan sulfate in dry mass fraction in GLHK-11-03 were 350, 730, and 502 μg kg(-1), respectively, and the respective expanded uncertainties, due to sample inhomogeneity, long-term and short-term stability, and variability in the characterization procedure, were 27 μg kg(-1) (7.8 %), 48 μg kg(-1) (6.6 %), and 33 μg kg(-1) (6.6 %).

The Government Laboratory has been involved in the provision of analytical and advisory services since its formal establishment in 1913 in support of the needs of the community and the commitments of the Government of Hong Kong Special Administrative Region, China. One of the earliest areas of work involves the testing of food samples for maintenance of public health and food safety. Remarkable advances in technology in recent years coupled with the introduction of new policies and regulations, the launching of new international standards and requirements have all contributed to significant and ever-rising demand of accurate, specific, comparable and traceable measurements using the latest technologies for a wide variety of additives, contaminants, residues and genetically modified ingredients in food.

This paper describes a metrological approach to evaluate the measurement capability of laboratories participating in two proficiency testing (PT) programmes involving the analysis of five polycyclic aromatic hydrocarbons (PAHs) in sediment samples. Reference values of PAHs in the programmes for performance assessment were obtained from an accurate isotope dilution gas chromatography mass spectrometry (ID-GCMS) method which was thoroughly validated and verified. Isotope dilution mass spectrometry (IDMS) technique usually has a well-defined measurement uncertainty budget and a traceability link to an International System of Units. Provision of the metrological reference values in PT enables the establishment of a technical platform to assess the actual competence of the participating laboratories in sediment PAHs analysis. Results of the PT programmes showed that about 80 % of the laboratories employed gas chromatography in their analyses and the remaining used liquid chromatography. Irrespective of the techniques being used, however, the majority of the participating laboratories were observed to underestimate values in which the mean values of the five reported PAHs were less than those of the ID-GCMS-derived reference values by 13–20 %. Only 41–44 % of the participating laboratories were able to achieve satisfactory z-scores. The present study revealed that the reinforcement of the capability for accurate measurement of PAHs in sediment samples in laboratories worldwide should be addressed.

This paper presents the preparation of a candidate certified reference material (CRM) of cypermethrin in green tea, GLHK-11-01a according to the requirements of ISO Guide 34 and 35. Certification of the material was performed using a newly developed isotope dilution mass spectrometry (IDMS) approach, with gas chromatography high resolution mass spectrometry (GC-HRMS) and gas chromatography-tandem mass spectrometry (GC-MS/MS). Statistical analysis (one-way ANOVA) showed excellent agreement of the analytical data sets generated from the two mass spectrometric detections. The characterization methods have also been satisfactorily applied in an Asia-Pacific Metrology Program (APMP) interlaboratory comparison study. Both the GC-HRIDMS and GC-IDMS/MS methods proved to be sufficiently reliable and accurate for certification purpose. The certified value of cypermethrin in dry mass fraction was 148 μg kg(-1) and the associated expanded uncertainty was 14μg kg(-1). The uncertainty budget was evaluated from sample in homogeneity, long-term and short-term stability and variability in the characterization procedure. GLHK-11-01a is primarily developed to support the local and wider testing community on need basis in quality assurance work and in seeking accreditation.

At the Paris meeting in April 2011, the CCQM Working Group on Organic Analysis (OAWG) agreed on a suite of Track A studies meant to support the assessment of measurement capabilities needed for the delivery of measurement services within the scope of the OAWG Terms of Reference. One of the studies discussed and agreed upon for the suite of ten Track A studies that support the 5-year plan of the CCQM Core Competence assessment was CCQM-K95 'Mid-Polarity Analytes in Food Matrix: Mid-Polarity Pesticides in Tea'. This key comparison was co-organized by the Government Laboratory of Hong Kong Special Administrative Region (GL) and the National Institute of Metrology, China (NIM). To allow wider participation, a pilot study, CCQM-P136, was run in parallel. Participants' capabilities in measuring mid-polarity analytes in food matrix were demonstrated through this key comparison. Most of the participating NMIs/DIs successfully measured beta-endosulfan and endosulfan sulphate in the sample, however, there is room for further improvement for some participants. This key comparison involved not only extraction, clean-up, analytical separation and selective detection of the analytes in a complex food matrix, but also the pre-treatment procedures of the material before the extraction process. The problem of incomplete extraction of the incurred analytes from the sample matrix may not be observed simply by using spike recovery. The relative standard deviations for the data included in the KCRV calculation in this key comparison were less than 7 % which was acceptable given the complexity of the matrix, the level of the analytes and the complexity of the analytical procedure. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

A study of single-laboratory validation (SLV) of a reversed-phase liquid chromatography (RP-LC) method was conducted for the determination of diester-diterpene Aconitum alkaloids, viz., aconitine, mesaconitine, and hypaconitine, in a variety of dietary supplements, including single-and multiple-ingredient dry powder extracts, pills, capsules, and raw materials. The Aconitum alkaloids in the samples were extracted by diethyl ether in the presence of ammonia. After cleanup with solid-phase extraction to remove the matrix interferences, the alkaloids were determined by RP-LC with UV detection at 235 nm, and the results were confirmed by tandem mass spectrometry. The linear responses for aconitine, mesaconitine, and hypaconitine based on the present LC system ranged from 0.5 to 200 μg/mL. Relative standard deviations of 2.0 to 6.9% were obtained from duplicate analysis of 6 test materials of different matrixes for the 3 Aconitum alkaloids performed by 2 analysts on 5 different days. The recoveries determined for supplements and raw materials spiked with 3 Aconitum alkaloids at levels of 2.5-10 μg/g were in the range of 86-99%. In view of the attainment of satisfactory results for accuracy, precision, and recovery in the SLV study, it is recommended that the method validation process proceed to a collaborative study.

A simple, cost-effective, and high throughput method using on-line column-switching liquid chromatography fluorescence detection was developed and validated for analysing five (fluoro)quinolones (FQs)—enrofloxacin (ENRO), ciprofloxacin (CIPR), sarafloxacin (SARA), oxolinic acid (OXOL), and flumequine (FLUM) in bovine milk. Norfloxacin (NORF) and nalixidic acid (NALI) were used as internal standards. After simple deproteination of milk sample with 5% (w/v) metaphosphoric acid, the supernatant was subject to on-line column clean-up and direct analysis by LC–FLD. The extraction cartridge was prepared in-house by slurry packing with hydrophilic–lipophilic polymer sorbent. The accuracy of measurement for each (fluoro)quinolone at different maximum residue limits (MRL) was 101–103% (ENRO), 92.8–97.4% (CIPR), 89.8–92.8% (SARA), 116–121% (OXOL), and 81.3–85.5% (FLUM), whilst the precision was 2.9–6.1% (ENRO), 2.5–5.1% (CIPR), 2.3–5.0% (SARA), 3.1–5.9% (OXOL), and 5.6–6.5% (FLUM). The decision limits, detection capabilities, specificity and analytes stability during storage were also investigated.

A sensitive method for determining lincomycin in bovine milk, animal muscles and organs using liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI/MS/MS) is presented. Milk and homogenized animal tissues were extracted with acetonitrile twice after addition of an appropriate amount of clindamycin, a lincosamide analogue as the internal standard. The combined extracts were finally made up to 10 ml with distilled water and partitioned with hexane to remove the animal fats prior to analysis. Analytes in the extracts were separated on a reversed phase C18 column (250 mm x 2.1 mm, 5 microm) using a mobile phase of a 3:7 (v/v) mixture of 0.1% formic acid in acetonitrile and an ammonium formate buffer (ammonium formate:formic acid:acetonitrile:water, 1:5:50:950, v/v/v/v) running at a flow rate of 0.2 ml min(-1). Presence of lincomycin was confirmed by the presence of two characteristic product ions at m/z 126.1 and 359.2 within a defined retention time window from the precursor ion at m/z 407.2, whilst quantification was based on the relative ratio of the sum of the peak areas at m/z 126.1 and 359.2 for lincomycin to that of the internal standard (peaks at m/z 126.1 and 377.2) with reference to the respective ratios of the calibration standards. The validated method that was found to have linear responses in the calibration range from 25 to 3000 microg kg(-1) and satisfactory intra-day and inter-day accuracy (94.4-107.8%) and precision (1.3-7.8%) at concentrations ranging from 100 to 1500 microg kg(-1) has been applied to real samples and matrix spiked samples. It is considered robust and suitable for analysis of lincomycin in milk and animal tissues.

A solvent extraction–gas chromatographic method was developed for the measurement of four classes of solvent-extractable organic compounds (SEOC), viz., aliphatic hydrocarbons, polynuclear aromatic hydrocarbons, fatty acids and alkanols, in ambient carbonaceous aerosols. The selectivity and recovery of the method using different solvents commonly used in the analysis of SEOC was evaluated. The composition of SEOC in aerosol and urban dust samples was found to vary with the choice of solvent. Such variation was not observed in filters spiked with standards of SEOC. The developed method was validated by the analysis of reference urban dust SRM 1649a from the National Institute of Standards and Technology. The concentrations of selected polynuclear aromatic hydrocarbons in the reference dust were found to fall within the certified and reference concentrations. The thermal characteristics of aerosol samples collected in an urban area of Hong Kong and the four classes of identified SEOC were also studied using a thermal optical transmittance (TOT) method as specified in NIOSH Method 5040. Correlations were made to compare the method-dependent SEOC content obtained by the solvent extraction method and the results for total carbon, organic carbon and elemental carbon obtained by the TOT method.

A technique using Summa canisters with cryogenic preconcentration and gas chromatographic-mass spectrometric (GC-MS) detection was developed to determine 143 C3-C12 volatile organic compounds (VOCs) including alkanes, alkenes, aromatics and halohydrocarbons in ambient and indoor air. The method detection limits and practical quantification limits were sensitive at 0.02 and 0.10 ppbv, respectively, and the method precision and accuracy were also satisfactory. The stability of C3-C12 VOC standards at ppbv levels under elevated pressure in canisters was assessed over various time intervals (from 1 week to 4 months after preparation) and most of the compounds were found to be acceptably stable with a mean recovery of 85.6 +/- 9.9% during the course of a 4-month study. However, a small fraction (approximately 6%) of the compounds, including two halohydrocarbons (bromotrichloromethane and benzyl chloride) and six alkenes (2-methylbuta-1,3-diene (isoprene), cis-4-methylpent-2-ene, cis-3-methylpent-2-ene, hept-1-ene, oct-1-ene and styrene) displayed relatively low recoveries in the range 34.6-67.9%. The loss of these compounds is most probably caused by their physical adherence to the active sites of the canister surface, chemical decomposition and/or reactions with other species. The results indicated that one must be cautious in attempting to measure these compounds owing to their instability in canisters. Overall, this analytical technique, which has been used for the determination of the VOCs under study in the toxic air pollutant monitoring network administered by the HKSAR Government, was amenable to the measurement of airborne VOCs collected both outside and inside a semi-confined car park in the present study.

The key comparison CCQM-K89 was undertaken to demonstrate the capability of participating NMIs and DIs in measuring the contents of incurred trace elements (total arsenic, cadmium and lead) and essential elements (calcium and zinc) at ?g/g (for arsenic, cadmium, lead and zinc) and mg/g (for calcium) levels in a herb matrix sample by various analytical techniques. This key comparison was organized by the Government Laboratory of the Hong Kong Special Administrative Region (GLHK) and agreed at the Inorganic Analysis Working Group Meeting in Hind?s, Sweden in October 2010 as a benchmarking exercise with arsenic (a trace element) and calcium (an essential element) chosen as the 'exemplary' elements. It was also agreed that a pilot study CCQM-P126 would be run in parallel with this key comparison. The key comparison serves to facilitate claims by participants on the Calibration and Measurement Capabilities (CMCs) as listed in Appendix C of the Key Comparison Database (KCDB) under the Mutual Recognition Arrangement of the International Committee for Weights and Measures (CIPM MRA). A total of 20 NMIs/DIs registered for this programme and 18 of them submitted their results. Most of the participants used microwave acid digestion methods for sample dissolution. For the instrumental determination, a variety of techniques like ICP-MS, AAS, INAA, ICP-AES were employed by the participants. For this key comparison, inorganic core capabilities have been demonstrated by concerned participants with respect to methods including ICP-MS (without isotope dilution), ID-ICP-MS, ICP-AES, INAA, AAS and ion chromatography with iteratively matrix-matched calibration on the determination of total arsenic, calcium, cadmium, lead and zinc in a matrix of herb. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

The supplementary comparison APMP.QM-S5 was undertaken to demonstrate the capability of participating national metrology institutes (NMIs) and designated institutes (DIs) in measuring the contents of the incurred essential elements (iron and zinc) and toxic elements (total arsenic and cadmium) at ?g/g levels in a test sample of dried shrimp by various analytical techniques. At the APMP TCQM Meeting held in Pattaya, Thailand in November 2010, Government Laboratory of the Government of the Hong Kong Special Administrative Region (GLHK) proposed this APMP supplementary comparison. The proposal was further discussed and agreed upon at the CCQM Inorganic Analysis Working Group Meeting held in Paris in April 2011. GLHK was the coordinating laboratory for the supplementary comparison. For enhancing the collaboration amongst specialized regional bodies in Asia-Pacific and to help build the laboratory capacity of NMIs/DIs from developing economies, the reference values of the supplementary comparison are used for evaluation of performance of participants of an APMP proficiency testing programme (APMP PT 11-01), an Asia-Pacific Laboratory Accreditation Cooperation proficiency testing programme (APLAC T082) and an Asia-Pacific Economic Co-operation proficiency testing programme (APEC PT), which were concurrently run using the same testing material as in APMP.QM-S5. The supplementary comparison serves to facilitate claims by participants on the Calibration and Measurement Capabilities (CMCs) as listed in Appendix C of the Key Comparison Database (KCDB) under the Mutual Recognition Arrangement of the International Committee for Weights and Measures (CIPM MRA). A total of 18 institutes registered for the supplementary comparison and all of them submitted their results. Most of the participants used microwave acid digestion methods for sample dissolution. For the instrumental determination, a variety of techniques like ICP-MS, ICP-OES, INAA and AAS were employed by the participants. For this supplementary comparison, inorganic core capabilities have been demonstrated by concerned participants with respect to methods including ICP-MS (without isotope dilution), ID-ICP-MS, ICP-OES, INAA and AAS on the determination of total arsenic, cadmium, iron and zinc in a matrix of seafood. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the APMP, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).