The analytical determination of polyphosphates in food: A point-to-point comparison between direct ion chromatography and indirect photometry

Squaraine dye as a fluorescent probe for highly sensitive detection of pyrophosphate and alkaline phosphatase

We synthesized a squaraine dye (F-0) to develop a method for detecting pyrophosphate (PPi) and alkaline phosphatase (ALP) by modulating the fluorescence of F-0. The fluorescence intensity of the F-0 system was quenched upon the addition of Cu2+ ions; however, it was restored when PPi was introduced due to the formation of a complex between PPi and Cu2+. Since ALP can hydrolyze PPi, the fluorescence of the system was quenched again upon the addition of ALP. Based on these principles, we established a fluorescent probe that exhibits an "off-on-off" fluorescence response. The detection limits of this method for PPi and ALP were 103 nmol dm-3 and 0.18 U dm-3, respectively. Moreover, this method demonstrates good selectivity and specificity and can be applied to the detection of PPi in actual samples.

Simple, fast, and simultaneous determination of orthophosphate, pyrophosphate, and tripolyphosphate by capillary electrophoresis with capacitively coupled contactless conductivity detection

This work describes a novel analytical method using capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C4D) for simultaneous, simple, and rapid determination of three inorganic phosphates (orthophosphate, pyrophosphate, and tripolyphosphate) widely used as food additives and in pharmaceutical formulations. A background electrolyte composed of 0.5 mol L-1 acetic acid provided fast separation (around 3.0 min) and good separation efficiency and peak resolution. Linearity in the concentration range of 10-500 mg L-1 was confirmed by the coefficients of determination (R2) higher than 0.99. The limits of detection varied from 0.41 to 0.58 mg L-1. The accuracy of the proposed method was assessed by recovery tests conducted at three concentration levels in tap water samples, food, and personal hygiene products. Recovery values varying from 81% to 118% were achieved, indicating an acceptable accuracy. The proposed CE-C4D successfully determined the three inorganic phosphates in the analyzed samples.

Dicationic imidazole ionic liquid stationary phase for preservative detection and its application under mixed mode of HILIC/RPLC/IEC

BACKGROUND

Food safety has always been a great concern, and the detection of additives is vital to ensuring food safety. Therefore, there is a necessity to develop a method that can quickly and efficiently separate and detect additives in food. High performance liquid chromatography is widely used in the analysis and testing of food additives. Ionic liquids have attracted wide attention in the preparation of high performance liquid chromatography stationary phases owing to their high stability, low vapor pressure and adjustable structure.

RESULTS

We developed a novel dicationic imidazole ionic liquid stationary phase for the simultaneous determination of organic preservatives (sodium benzoate, potassium sorbate) and inorganic preservatives (nitrate and nitrite) in foodstuffs under mixed-mode chromatography. The method had the advantages of easy operation, high reproducibility, good linearity and precision. In the detection of these four preservatives, the limit of detection ≤0.4740 mg⋅L-1 and the limit of quantification ≤1.5800 mg⋅L-1. The intra-day and inter-day precision were less than 4.02%, and the recovery rate was 95.90∼100.19 %. At the same time, we also characterized the stationary phase, explored the mechanism and evaluated the chromatographic performance. The stationary phase was able to operate under the mixed mode of reversed phase/hydrophilic interaction/ion exchange chromatography, and it was capable of separating hydrophilic substances, hydrophobic substances, acids, and inorganic anionic substances with good separation efficiency and had high column efficiency.

SIGNIFICANCE

In summary, the stationary phase has a promising application in the routine analysis of organic and inorganic preservatives in food. In addition, the stationary phase has good separation ability for hydrophilic, hydrophobic, ionic substances and complex samples, making it a prospective material for chromatographic separation.

Determination of phosphate in food based on molybdenum yellow derivatization coupled with resonance Rayleigh scattering method

This paper proposed a rapid, selective and sensitive molybdenum yellow derivatization coupled with Resonance Rayleigh scattering (MYD-RRS) method for detection of phosphate. Under the acidic condition, phosphate can be selectively transformed to Keggin type of phosphomolybdic acid (PMA, i.e., PMo12O403-) through molybdenum yellow derivatization reaction prior to RRS detection. The PMA can further react with cationic methyl violet (MV) to form larger PMA-MV ion association complexes, generating significant RRS signal. The concentration of phosphate was linearly related to the RRS signal in the range of 8-200 ng/mL, with the determining coefficient (R2) of 0.9973 and the detection limit of 4 ng/mL. The analytical procedure can be completed within 10 min and the RRS signal intensity can remain stable more than 4 h. The method showed good stability toward temperature and time, and good anti-interference capability. The method was applied to the determination of phosphate in real food samples with the recovery of 85-117% and RSD of 1-5.2%. With the advantages of rapidness, high sensitivity and good selectivity, the MYD-RRS method exhibits great potential to the determination of phosphate in food. It also provides an instructive strategy for detection of analytes with weak RRS signal.

Monitoring of polyphosphate levels in animal source products collected in Italy by means of ion chromatography with suppressed conductivity detection

Polyphosphates (PPs) constitute a class of food additives widely used due to their ability to exercise different useful activities. The food safety concern about the use of PPs in food is both the possible non-declared addition and some health effects, such as bile duct stones, decrease in oligo-element absorption, and allergic reactions in susceptible people. In this study, an analytical method based on ion chromatography with conductivity detection was applied for the detection and quantification of PPs in 238 samples of animal-derived products such as meat, dairy, and fish products. A contribution to risk assessment was also included. The monitoring confirmed the absence of non-compliant results. All concentrations of PPs were indeed lower than the legal limits set in European Regulation No. 1333/2008. Moreover, no residue of PPs was detected (> limit of quantification: 0.09 g kg-1) in samples where it was not reported on the product label. No PPs were detected in mollusks, meat-based preparations, semi-ripened, unripened, and spun paste cheese, while they are widely used in surimi, with concentrations in the range of 0.1-0.5 g kg-1. The highest concentrations were quantified in a würstel sample (4.7±0.3 g kg-1) and a spreadable cheese sample (8.9±0.7 g kg-1). Considering that the high exposure scenario together with a very susceptible population group (toddlers) were taken into account for this risk exposure study and that the highest admissible daily intake obtained was equal to 10.4%, the assessment demonstrated that the actual use of PPs in food does not pose a risk for food safety.

Cobalt-Based Metal-Organic Framework Nanoparticles with Peroxidase-like Catalytic Activity for Sensitive Colorimetric Detection of Phosphate

Appropriate addition of phosphate salt in food can improve the food quality and taste. However, extensive intake of phosphate salt may lead to some human diseases such as hyperphosphatemia and renal insufficiency. Thus, it is essential to establish a cost-effective, convenient, sensitive, and selective method for monitoring phosphate ion (Pi) to ensure food quality control. In this work, a Co-based metal-organic frameworks (Co-MOF) nanomaterial with dual functions (peroxidase-like activity and specific recognition) was designed for acting as a catalytic chromogenic platform for sensitive detection of Pi. The Co2+ nodes not only provide high enzyme-like activity to catalyze the 3,3′,5,5′--tetramethylbenzidine (TMB) substrate to blue oxTMB (652 nm) but also act as selective sites for Pi recognition. The use of cationic organic ligands (2-methylimidazole) and cationic metal ions (Co2+) endows the Co-MOF with a strong positive surface charge, which is beneficial to the capture of negative-charged Pi and the dramatically suppressed TMB oxidation. When Pi exists, it specifically adsorbs onto the Co-MOF through the Co-O-P bond and the strong electrostatic interaction, leading to the change of surface charge on Co-MOF. The peroxidase-like catalytic activity of Co-MOF is thus restrained, causing a different catalytic effect on TMB oxidation from that without Pi. Based on this principle, a colorimetric assay was established for rapid and sensitive detection of Pi. A good linear relationship was obtained between Pi concentration and the absorbance at 652 nm, with a linear range of 0.009–0.144 mg/L and a detection limit of 5.4 μg/L. The proposed assay was applied to the determination of Pi in actual food samples with recoveries of 92.2–108% and relative standard deviations (RSDs) of 2.7–7.3%, illustrating the promising practicality for actual samples analysis.

Analysis of added phosphates in hake fillets by ion-exchange chromatography: A case study of false positives induced by nucleotides coelution

This study aimed to optimize an ion-exchange chromatography method for an accurate quantification of phosphates. Coelution of nucleotides was detected following the quantification of small amounts of di- and trimetaphosphates in hake fillets. In some samples, triphosphates were added to the glaze ice, therefore, defrosting waters (glaze ice + drip loss of fillets) should be analyzed for an effective assessment of the use of phosphates in seafood. Even low amounts of adenosine 5'-diphosphate (ADP) and inosine 5'-monophosphate (IMP) triggered false positive results for P₂O₇^4- and P₃O₉^3-. Keeping the initial isocratic conditions for longer was crucial for the separation of ADP from P₂O₇^4- and of IMP from P₃O₉^3-. The improved method showed that in general, hake fillets did not have diphosphates, and trimetaphosphates were residual. Triphosphates were clearly added in only four defrosting waters, and in most of the remaining ones, diphosphates and trimetaphosphates contents corresponded to false positive results.

Undeclared (Poly)phosphates Detection in Food of Animal Origin as a Potential Tool toward Fraud Prevention

(Poly)phosphates are approved as water-preserving and emulsifying agents that improve the appearance and consistency of many food products. The labelling of added (poly)phosphates is essential for protecting vulnerable population groups and to prevent unfair trade practices resulting in economic fraud. The problems with (poly)phosphates' utilisation concerns both analytical and legislative issues, such as: (1) their straightforward detection; (2) excessive addition altering freshness perception and misleading consumers; (3) uncontrolled usage increasing foodstuff weight; (4) application in products where they are not permitted; and (5) no indication on the label. Bearing all these issues in mind, the main purpose of this study was the quantification and screening of the (poly)phosphates profile in meat, marine and dairy products (160 samples), of which 43 were without declared (poly)phosphate treatment. Analysis was completed by high-performance ion-exchange chromatography either with conductometric detection or coupled to Q-Exactive Orbitrap high-resolution mass spectrometry. Although the (poly)phosphates profiles varied greatly according to species and processing type, the following criteria for detection of illicit treatment were established: high orthophosphate level, quantified short-chain (poly)phosphate anions and the presence of long-chain forms. In conclusion, the instrumental platforms used in this study can be recommended to inspection bodies as reliable methods for the detection of food adulteration with (poly)phosphates.

A review of the design of packing materials for ion chromatography

The development of ion chromatography has made remarkable progress in the past few decades, and it is now widely used for the analysis of common ions and organic compounds. Ion chromatography has many advantages, such as fast, high sensitivity, good selectivity and support for simultaneous analysis of multiple ionic compounds. In order to meet the high requirements of material analysis, new packing materials for ion chromatography with higher sensitivity and selectivity have been developed. In this paper, a lot of knowledge of ion chromatography is reviewed, and the development of ion chromatographic packings in recent years, especially in the last five years, is summarized.

ELISA and UPLC/FLD as Screening and Confirmatory Techniques for T-2/HT-2 Mycotoxin Determination in Cereals

T-2 and HT-2 toxins are secondary metabolites of various species of Fusarium. These molecules can have high potential toxic effects for human and animal health. In this work, ELISA and ultra performance liquid chromatography with fluorescence detection (UPLC/FLD) were implemented and validated as screening and confirmatory tests for the detection of these two toxins in cereal samples. The developed methods were tested by analyzing 100 samples of cereals by ELISA screening for reducing costs and analysis time and then using UPLC/FLD for confirmation purposes. Both methods met the performance criteria for sensitivity, linearity, selectivity, precision, and ruggedness, as reported in the European Decision No. 2002/657/EC and in Regulation (EC) No. 401/2006. The correlation between ELISA and UPLC/FLD approaches showed good results (r = 0.9056), confirming that these two techniques should be considered to be complementary in the official control activities of cereal and derived products.