Journal of Chemical Metrology

The process by which clay influences the preservation and retention of absorbed lipids in archaeological pottery is not well understood. Although properties such as porosity and calcium content are frequently suggested as primary factors in lipid retention, their exact influence remains unclear. To investigate this, replicate clay ceramics were manufactured using varying proportions of illitic/illite-smectitic clay, mixed with two different tempers (sand and chalk), and fired at 800°C in an oxidizing atmosphere. This study aimed to assess the impact of these compositional variations on the preservation and retention of selected fatty acids, palmitic acid (C16:0) and oleic acid (C18:1), often discovered in archaeological lipid residue analysis, in both heat-degraded (100°C for 14 h) and undegraded forms. Gas chromatography-mass spectrometry (GC-MS) was used for quantification, employing calibration curves generated from standard solutions of fatty acid methyl esters (FAME). Two methylation techniques were utilized: acid-catalyzed methylation (ACM) and solvent extraction using a mixture of dichloromethane (DCM) and methanol (MeOH), followed by m-(trifluoromethyl)phenyltrimethylammonium hydroxide (TMTFTH) methylation. A comparison of the two techniques revealed that prior solvent extraction using a combination of DCM-MeOH may have limited the amount of C16:0 and C18:1 methylated by TMTFTH, causing inconsistent results in quantification compared to ACM. From the ACM technique, results showed that sand-tempered briquettes, whether degraded (for C16:0) or non-degraded (for C16:0 and C18:1), have minimal influence on fatty acid yield while degradation significantly affects the yield of C18:1. In contrast, C16:0 and C18:1 recovery from chalk-tempered briquettes is proportional to clay content and inversely proportional to the chalk content. This holds both for degraded and non-degraded briquettes. This work highlights the importance of considering and investigating the mineralogical composition of clay and non-clay minerals for predicting the lipid yield from ancient ceramics.

              This study involves the characterization of a new shortwave NIR wavelength standard solution to address the current limitations of shortwave near infrared (NIR) standard materials and to expand the spectral wavelength range of standard materials. Herein, an innovative use of a solution of dysprosium oxide and ytterbium oxide compounds dissolved in perchloric acid solution to calibrate and verify the NIR wavelength of a high-sensitivity ultraviolet-visible-near infrared spectrophotometer is reported. This standard material enables the near infrared wavelength to be accurately traced to the theoretical emission wavelength of the elements. In the study, cubic spline interpolation was performed on the SI traceable and validated instrument for the determination of peak wavelengths. The wavelength standard values ​​of this standard material cover the shortwave near infrared region (700~1200 nm) with an uncertainty of 0.12 nm at a 95% confidence interval.

Patulin, a mycotoxin commonly found in contaminated food products, is a significant health concern and its accurate determination is of fundamental importance. The availability of a patulin reference material (RM) is a key tool for the confidence in analytical results. In this paper, a batch of patulin in 0.1% acidified acetonitrile RM was gravimetrically prepared. The prepared RM was ampouled and subjected to homogeneity, short-term, long-term stability and characterization studies by high-performance liquid chromatography with ultraviolet detection (HPLC-UV). The chromatographic separation was carried on a C-18 column using a mobile phase of ultra-pure water and acetonitrile (80:20 %) and the detection was made at 276 nm. These studies were carried out in accordance with ISO 17034 and ISO 33405. The prepared patulin reference material was found to be homogeneous and stable enough, as demonstrated by the results of the analysis of variance (ANOVA) and the regression analysis. The value assignment was based on combing data obtained by gravimetry and HPLC-UV as weighted mean and uncertainty and was found to be 26.78±1.66 mg/kg. The gravimetric preparation and value assignment of the patulin RM were validated by successful participation of the patulin RM producer, SASO/NMMC in the key comparison CCQM-K154. d. This produced patulin certified reference material (CRM) will be useful as a calibrant and as quality control sample in food safety analysis.

Wheat germ oil has the highest tocopherol content of all-natural vegetable oil. It’s used in cosmetics, pharmaceuticals, food, and dietary supplement products due to its high tocopherol content. Thus, the high marketing and nutritional values have led to an adulteration of this valuable oil. The quality and authentication control of wheat germ oil is based mainly on the quantitative determination of tocopherol concentration. Therefore, NIS has developed new candidate reference material for tocopherols in wheat germ oil to support regulatory authorities and food testing laboratories in their efforts to control oil quality and authenticity. The certification was carried out using two independent sample preparation methods in accordance with ISO 17034 and ISO Guide 35 requirements. The results indicate a sufficient homogeneity and stability of CRM for up to 12 months at 4 ℃.  The traceability of the CRM to SI units was established using the direct primary method. The certified value of α-tocopherol and β-tocopherol and their corresponding expanded uncertainties (k=2.0) were found to be (2033.9±49.8 mg/kg) and (625.4±38.1 mg/kg), respectively.