Abstract
The total petrol hydrocarbon (TPH) content in soil is determined by gas chromatographic separation and flame ionisation detection according to ISO 16703 in routine laboratories for about 20 years. The development of the interlaboratory variability observed with this analytical procedure over 15 years in a proficiency testing scheme conducted annually with more than 170 participants is evaluated in detail. A significant improvement of the reproducibility standard deviation among participants is observed over the years and attributed to an increasing familiarity with the procedure. Nevertheless, the determination of TPH in the environmentally relevant mass fraction range between 500 mg/kg and 10 000 mg/kg in soils or sediments is far from reaching the reproducibility standard deviations predicted by the Horwitz curve. It is seen that laboratories with sporadic participation tend to report higher bias, while a core group of laboratories participating on a regular basis arrived at reproducibility standard deviations below 20 %. Results from a given laboratory obtained on two different samples tend to be highly correlated in the same PT round indicating a sound repeatability. Expectedly, the within-laboratory correlation between results from consecutive rounds was considerably lower. However, results from consecutive rounds with a temporal distance of 1, 2 or 3 years revealed largely similar correlations which suggests that the within-laboratory reproducibility adjusts to a constant level at least after a period of 1 year.
References
Taverniers I, De Loose M, Van Bockstaele E (2004) Trends in quality in the analytical laboratory. II. Analytical method validation and quality assurance. Trac-Trend Anal Chem 23:535–552
Hund E, Massart DL, Smeyers-Verbeke J (2000) Inter-laboratory studies in analytical chemistry. Anal Chim Acta 423:145–165
European Proficiency Testing Information System EPTIS. www.eptis.bam.de
Becker R, Koch M, Wachholz S, Win T (2002) Quantification of total petrol hydrocarbons (TPH) in soil by IR-spectrometry and gas chromatography—conclusions from three proficiency testing rounds. Accred Qual Assur 7:286–289
Becker R, Buge HG, Nehls I (2007) The determination of adsorbable organically bound halogens (AOX) in soil: interlaboratory comparisons and reference materials. Accred Qual Assur 12:647–651
ISO 16703 (2004) Soil quality—determination of content of hydrocarbon in the range C10 to C40 by gas chromatography
ISO/TR 11046 (1994) Soil quality—determination of mineral oil content—method by infrared spectrometry and gas chromatographic method
ISO/IEC 17043 (2010) Conformity assessment—general requirements for proficiency testing
ISO 13528 (2015) Statistical methods for use in proficiency testing by interlaboratory comparison
DIN 38402-45 (2014-06) German standard methods for the examination of water, waste water and sludge—general information (group A)—Part 45: interlaboratory comparisons for proficiency testing of laboratories (A 45)
Becker R, Buge HG, Bremser W, Nehls I (2006) Mineral oil content in sediments and soils: comparability, traceability and a certified reference material for quality assurance. Anal Bioanal Chem 385:645–651
Wilrich PT (2007) Robust estimates of the theoretical standard deviation to be used in interlaboratory precision experiments. Accred Qual Assur 12:231–240
Uhlig S, Henschel P (1997) Limits of tolerance and z-scores in ring tests. Fresenius J Anal Chem 358:761–766
Zhong K, Zhao Y, Xiao YL, Wang W, He FL, Wang ZG (2015) 8-year review of laboratory performance on blood lead level external quality control assessment surveys 2006–2013 in China: continual improvement. Accred Qual Assur 20:25–28
Generali T, Stefanelli P, Girolimetti S, Barbini DA (2015) Proficiency tests on olive oil organized by the Italian National Reference Laboratory for pesticides: long-term performance of laboratories. Accred Qual Assur 20:247–253
Horwitz W (1982) Evaluation of analytical methods used for regulations of food and drugs. Anal Chem 54:67A–76A
Thompson M, Lowthian PJ (1998) The frequency of rounds in a proficiency test: does it affect the performance of participants? Analyst 123:2809–2812
Dorgerloh U, Becker R, Lutz A, Bremser W, Hilbert S, Nehls I (2012) How to improve reliability in groundwater analysis: over a decade of experience with external quality control in field campaigns on volatile halogenated compounds. J Environ Monit 14:217–223
Whetton M, Finch H (2009) Analytical performance is improved by regular participation in proficiency testing: an analysis of data from the Aquacheck proficiency testing scheme. Accred Qual Assur 14:445–448
Author information
Authors and Affiliations
Corresponding author
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Electronic supplementary material
Below is the link to the electronic supplementary material.
Rights and permissions
About this article
Cite this article
Becker, R., Sauer, A. & Bremser, W. Fifteen years of proficiency testing of total petrol hydrocarbon determination in soil: a story of success. Accred Qual Assur 24, 289–296 (2019). https://doi.org/10.1007/s00769-019-01383-x
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00769-019-01383-x