Green microsaponification-based method for gas chromatography determination of sterol and squalene in cyanobacterial biomass.

Sterol analysis of complex matrices can be very laborious. To minimize the existing drawbacks, a new micro-method of sterols and squalene determination in cyanobacteria was developed and applied to monitor their production of Phormidium autumnale cultured heterotrophically. Sample extraction/saponification and GC analysis of the target compounds were optimized separately using Plackett-Burman design (PB) followed by a central composite rotational design (CCRD). The most influential variables were identified to maximize compound recovery. Chloroform presented the highest capability to extract all target compounds with a horizontal shaker table (HST) for homogenization in the saponification step. For the pretreatment, a small amount of chloroform was used for 90 min at 50 °C and 6 min for the saponification time. The sample introduction in the GC injector was studied by evaluating pressure and injector temperature. High response for sterols and squalene were obtained between 19 and 23 psi and at 310 °C of injection temperature. The new method was able to determine different sterol concentrations: 0.2-0.6 mg kg-1 of squalene, 5-18 mg kg-1 of stigmasterol, 6 mg kg-1 of cholesterol, and 3 mg kg-1 of ß-sitosterol, showing high analytical performance and fulfilling all steps, thus proving to be a promising technique.

Combining In-Tip Reaction and Infrared Thermal Imaging for Fast and Portable Enthalpimetric Analysis.

In this work, the in-tip thermal infrared enthalpimetry (in-tip TIE) method is proposed for fast enthalpimetric analysis. In this method, the reactions inside the tips of a multichannel pipette were combined with temperature monitoring by an infrared camera. The filter paper was used inside the tips to retain reagents as solutions (wetted paper mode) or as solids (dried paper mode) to perform neutralization, redox, or precipitation reactions. The dried reagents inside the tips were obtained by oven drying a solution retained in the filter paper. The determination of the total acidity of the vinegar, ascorbic acid in vitamin C tablets, and chloride in soy sauces and saline inhalation solutions was performed as examples of the application of the proposed method. The agreement with reference methods ranged from 98 to 107%. The use of reagents dried inside the tip was feasible, leading to a simple aspiration of sample solution within the 12 tips of the pipette to perform a rapid analysis (1 min). Therefore, up to 720 measurements in 1 h were feasible for in-tip TIE over up to 12 measurements for the reference methods. Moreover, miniaturization reduced reagent consumption and residue generation. For example, for in-tip TIE, only 3.6 mL of residues was generated (n = 12) over 60-240 mL in reference methods (n = 3). Contrarily to other TIE methods, no microplates or stirring was required, opening possibilities for field analysis since the multichannel pipette and the infrared camera are both operated with batteries.

Open source, low-cost device for thermometric titration with non-contact temperature measurement.

This work proposes a simple device for thermometric titration using a contactless sensor. A low-cost infrared sensor (around $5) was adapted in a disposable, polystyrene vessel for monitoring the temperature to determine the endpoint of neutralization, redox, and complexation titrations, using a homemade syringe pump to titration control. Open-source software was developed to control the device using the Raspberry Pi platform and to perform automatic endpoint determination. The influence of sample volume, the flow rate of titrant, and sensor distance from the solution were evaluated to lower the variation among measurements. The parameters chosen in this regard were 10 mL of sample, 0.8 mL min-1 of titrant solution flow rate, and 3 cm of distance from the sensor to the solution. Results for the determination of the acidity of sauces and the ascorbic acid and calcium content of pharmaceutical products were compared with those from official compendia. The performance of the sensor also was compared with an infrared camera. The proposed method agreed with conventional ones to an extent ranging from 93% to 106%. The robust analytical performance and low cost of the system are essential features that could broaden the use of enthalpimetric analysis in several laboratories.

Rapid, Noninvasive, and Nondestructive Method for Biofilm Imaging on Metallic Surfaces Using Active Thermography.

A simple, rapid, low-cost method was proposed for the imaging of Pseudomonas aeruginosa biofilms on metallic surfaces using an infrared camera. Stainless steel coupons were cooled to generate a thermal gradient in relation to biofilm for active thermography (AT). Both cooling and image acquisition times were optimized and the images obtained with AT were compared with those from scanning electron microscopy. A free software (Thermofilm) was developed for image processing and the results were compared with the software ImageJ, with good agreement (from 87.7 to 103.8%). Images of coupons treated with sanitizer (peracetic acid) were obtained to show the applicability of the proposed method for biofilm studies. All analytical steps could be performed in 3 min in a noncontact, nondestructive, low-cost, portable, and easy-to-use way.

Is it possible to reduce the cooking time of mortadellas using ultrasound without affecting their oxidative and microbiological quality?

This study evaluated the reduction of cooking time of mortadellas using ultrasound (US, 25 kHz) and the effects on the oxidative and microbiological quality of the product. Three cooking conditions were studied: control, cooking time traditionally adopted by the meat industry; TUS and TWUS: cooking with and without US application and 50% reduction of the traditional cooking time, respectively. The application of US did not increase the peroxide, conjugated dienes, and TBARS indices and did not accelerate the protein oxidation. In addition, no significant changes were observed in the color of the mortadellas subjected to ultrasonic-assisted cooking. TUS and control presented a similar mesophilic, psychrotrophic and lactic acid bacteria counts during storage. The ultrasonic-assisted cooking provided a faster increase and higher homogeneity in the internal temperature of the mortadellas. Therefore, the US can be considered a promising technology to improve the cooking process of mortadellas.

Infrared thermal imaging combined with paper microzone plates and natural reagent extracts for simple, fast, and green enthalpimetric analysis.

Paper microzone plates and thermal infrared enthalpimetry (TIE) were combined with potato juice as natural reagent extract to perform the determination of hydrogen peroxide in pharmaceutical, bleaching, and toiletry products. A multichannel pipette was used for reagent addition simultaneously in multiple zones of paper devices, and the temperature rise was determined using an infrared camera. In order to provide suitable measurements, some parameters were optimized such as pH, volume of reagents, and stability of the extract. Results for the hydrogen peroxide were compared with those obtained using methods from official compendia (United States Pharmacopeia and ASTM D2180-17), with agreements ranging from 96 to 103%. The green analytical procedure index was used to compare the greenness of the proposed method with official ones, with clear advantages for TIE. Only microliters of samples and natural reagent extracts were required for analysis, and it was found that waste generation could be greatly reduced. After analysis, the paper device could be directly disposed since the final products of the reaction were O2 and water. According to these features, the proposed method could be considered a promising alternative to routine analysis in agreement with green analytical chemistry principles.

A new approach to calibration and determination of selected trace elements in food contact polymers by LA-ICP-MS.

A calibration strategy using porous nylon disks and reference solutions is proposed for the first time for matrix matching and determination of As, Ba, Cd, Cr, Pb, Sr and Zn in polymers by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS). Polymer samples commonly used in contact with food were analyzed. The procedure consists on the use of porous nylon disks as support for a dried droplet reference solution. Calibration in the range of 0.50-190µgg-1 for Ba, Cd, Cr, Pb, Sr and Zn and from 0.30-9.0µgg-1 for As was used. Laser and ICP-MS instrument conditions were evaluated in order to achieve the best signal-to-background ratio. The radiofrequency power and carrier gas flow rate were fixed at 1300W and 1.25Lmin-1, respectively. Spot size, repetition rate, scan line speed and laser fluency were set to 100µm, 20Hz, 100µms-1 and 17.9Jcm-2, respectively, as the established conditions for analysis of standards and samples. By using these conditions, limits of detection, estimated considering B+3s (where B is the value of the blank and s is the standard deviation of 10 measurements of the blank), ranged from 0.09µgg-1 (208Pb) to 1.09 (53Cr) and 0.05µgg-1 (208Pb) to 2.10 (53Cr) for calibration with and without 13C as internal standard (IS). In spite to the use of nylon for matrix matching of different polymeric matrices, the normalization with 13C as IS was also evaluated. The precision of the method is relatively good (RSD<20%), and the accuracy of the method, evaluated by analysis of certified reference materials (CRM) and by comparison with results obtained from solution analysis by ICP-MS after sample decomposition by microwave induced combustion (MIC) is relatively good. The suitability of the proposed method resulted in direct and reliable analyses of polymer samples with a simplified or unnecessary sample preparation step. In addition, the calibration with dried droplet reference solutions may be considered a promising procedure in view of its advantages to other forms of calibration, as the use of CRM or the preparation of synthetic standards. The use of porous nylon disks spiked with reference solutions for calibration is the main advantage of the present work.

External calibration strategy for trace element quantification in botanical samples by LA-ICP-MS using filter paper.

The use of reference solutions dispersed on filter paper discs is proposed for the first time as an external calibration strategy for matrix matching and determination of As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sr, V and Zn in plants by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS). The procedure is based on the use of filter paper discs as support for aqueous reference solutions, which are further evaporated, resulting in solid standards with concentrations up to 250 µg g(-1) of each element. The use of filter paper for calibration is proposed as matrix matched standards due to the similarities of this material with botanical samples, regarding to carbon concentration and its distribution through both matrices. These characteristics allowed the use of (13)C as internal standard (IS) during the analysis by LA-ICP-MS. In this way, parameters as analyte signal normalization with (13)C, carrier gas flow rate, laser energy, spot size, and calibration range were monitored. The calibration procedure using solution deposition on filter paper discs resulted in precision improvement when (13)C was used as IS. The method precision was calculated by the analysis of a certified reference material (CRM) of botanical matrix, considering the RSD obtained for 5 line scans and was lower than 20%. Accuracy of LA-ICP-MS determinations were evaluated by analysis of four CRM pellets of botanical composition, as well as by comparison with results obtained by ICP-MS using solution nebulization after microwave assisted digestion. Plant samples of unknown elemental composition were analyzed by the proposed LA method and good agreement were obtained with results of solution analysis. Limits of detection (LOD) established for LA-ICP-MS were obtained by the ablation of 10 lines on the filter paper disc containing 40 µL of 5% HNO3 (v v(-1)) as calibration blank. Values ranged from 0.05 to 0.81  µg g(-1). Overall, the use of filter paper as support for dried aqueous standards showed to be a useful strategy for calibration and plant analysis by LA-ICP-MS.