Rapid, sensitive, and reproducible screening of liquid milk for adulterants using a portable Raman spectrometer and a simple, optimized sample well

Abstract

We have developed a powerful general spectroscopic method for rapidly screening liquid milk for adulterants by combining reflective focusing wells simply fabricated in aluminum with a small, portable Raman spectrometer with a focusing fiber optic probe. Hemispherical aluminum sample wells were specially designed to optimize internal reflection and sampling volume by matching the focal length of the mirror to the depth of focus of the laser probe. The technique was tested on milk adulterated with 4 different nitrogen-rich compounds (melamine, urea, dicyandiamide, and ammonium sulfate) and sucrose. No sample preparation of the milk was needed, and the total analysis time was 4min. Reliable sample presentation enabled average reproducibility of 8% residual standard deviation. The limit of detection interval measured from partial least squares calibrations ranged between 140 and 520mg/L for the 4 N-rich compounds and between 7,000 and 36,000mg/L (0.7-3.6%) for sucrose. The portability of the system and the reliability and reproducibility of this technique open opportunities for general, reagentless screening of milk for adulterants at the point of collection.

Technical note: Nontargeted detection of adulterated plant proteins in raw milk by UPLC-quadrupole time-of-flight mass spectrometric proteomics combined with chemometrics

“…Lu et al (2015) successfully applied a UPLC AA fingerprinting technique in differentiating milk and nonmilk proteins in our previous study. Near-infrared and Raman spectroscopy combined with principal component analysis (PCA) and partial least-squares-discriminant analysis (PLS-DA) were used to detect possible adulteration in liquid and powdered milk (Botros et al, 2013;Yang et al, 2013;Alves da Rocha et al, 2015;Nieuwoudt et al, 2016). However, these methods often offered little information about the identities of adulterated proteins, which limited the final precision for the identification of adulterated proteins.…”

Natural Deposition Strategy for Interfacial, Self‐Assembled, Large‐Scale, Densely Packed, Monolayer Film with Ligand‐Exchanged Gold Nanorods for In Situ Surface‐Enhanced Raman Scattering Drug Detection

“…2018, 24,4094 -4102 www.chemeurj.org 2018 Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim 7.8 %, whereas the film transferredw ith tweezers has an average signal intensity of only 1379.6 counts with an RSD as large as 86.3 %. [27] Herein, ap ortable Raman spectrometer was used to verify the practicality of the 2D self-assembled interfacial SERS platform. The signals of SERS spectra for differentc oncentrationso fC Vf rom 10 À7 to 10 À9 m with the self-assembled 2D array and dry AuNRsw ere recorded ( Figure S5 in the Supporting Information).…”

“…SERS as a reliable molecular vibrational detection methodh olds great promise foru se on complex biological systems due to high sensitivity and selectivity.O wing to miniaturization, portability, and large spot area, ap ortable Raman spectrometer has been widely applied to drug abuse, [24] pollutants, [25] explosives, [26] and food safety. [27] Herein, ap ortable Raman spectrometer was used to verify the practicality of the 2D self-assembled interfacial SERS platform. To examine the reliability and sensitivity of the SERS platform, characteristicS ERS spectra of methamphetamine (MA) extracted from human urine at different concentrations from 100 ppb to 100 ppm were recorded ( Figure 4A).…”

Nontargeted Analytical Methods as a Powerful Tool for the Authentication of Spices and Herbs: A Review

“…However, although the demand for portable devices has increased (Bouyé & d'Humières, 2017), its focus has been the evaluation of food quality and composition, especially in meat, dairy products, and fruits and vegetables (Abasi et al, 2018;Capitani, Sobolev, Di Tullio, Mannina, & Proietti, 2017;Porep, Kammerer, & Carle, 2015). In addition, there are works based on portable/handheld spectrometer for food authentication (Basri et al, 2017;Correia et al, 2018;Grassi & Alamprese, 2018;Limm, Karunathilaka, Yakes, & Mossoba, 2018;Liu et al, 2018;Manfredi et al, 2018;Nieuwoudt, Holroyd, McGoverin, Simpson, & Williams, 2016;Picouet, Gou, Hyypiö, & Castellari, 2018;Schmutzler, Beganovic, Böhler, & Huck, 2015;Shotts, Plans Pujolras, Rossell, & Rodriguez-Saona, 2018;Vargas Jentzsch, Torrico-Vallejos, Mendieta-Brito, Ramos, & Ciobotȃ, 2016).…”