A sensitive, robust method for quantification of sodium picosulfate in food
Using the SCIEX Triple Quad™ 3500 LC-MS/MS System
Chen Xi, Zhao Xianglong, Li Lijun, Guo Lihai
SCIEX, China
Abstract
Here, the SCIEX Triple Quad 3500 LC-MS/MS System was used to establish a high throughput 4 minute quantitative method for sodium picosulfate in food. This method has high sensitivity, good repeatability, and a wide linear dynamic range of 0.4 to 1000 ng/mL. No matrix effect in 5 different food matrices was observed.
Introduction
Sodium picosulfate, also known as 4,4'-(pyridin-2-ylmethylene) bisphenol-based bissulfate sodium salt, is a special laxative, which has a mild laxative effect on the large intestine mucosa. It is sometimes used clinically for patients experiencing constipation following surgery and barium meal.
Recently, in accordance with the relevant requirements of the "Food Supplementary Inspection Method Work Regulations", the State Administration for Market Supervision has approved the release of the "Determination of Sodium Picosulfate in Food" food supplementary inspection method.1 This standard mainly describes the LC-MS/MS quantitative detection method of sodium picosulfate in foods (including jelly, preserves, candies, beverages, health foods, etc.).
Here the above-mentioned measurement method was established using the SCIEX Triple Quad 3500 LC-MS/MS System to establish a fast and sensitive MRM quantitative method. The linearity, recovery and repeatability of the method was verified. This general method can be applied across different SCIEX Triple Quad systems.
Figure 1. Chromatogram of the compound at the lower limit of quantification (0.4 ng/mL).
Key advantages
- Fast and sensitive: A liquid-phase elution time only needs 4 minutes, and the quantification limit of sodium picosulfate is as low as 0.4 ng/mL (Figure 1), providing sensitivity which meets the standard requirement (5 ng/mL).1
- Wide linear range: Assay provided wide linear dynamic range for sodium picosulfate, across a concentration range of 0.4~1000 ng/mL (Figure 3).
- Wide application range: This method verifies the recovery rates of the five substrates mentioned in the standard (Table 1) with minimal interferences.
Table 1. The recovery rate of sodium picosulfate in five different matrices.
Methods
Sample and standard preparation: According to the sample preparation process in the food supplement inspection method of "Determination of sodium picosulfate in food", pre-treatment of a certain tablet health product, candy, solid beverage, plum and jelly was carried out.1
The standard curve samples were diluted with pure water and prepared into solutions with concentrations of 0.4, 1, 2, 6, 20, 60, 200, 600, and 1000 ng/mL, with a total of 9 concentration points.
LC Conditions: SCIEX ExionLC™ AD System was used with Phenomenex Kinetex C18, 2.6 µm, 2.1 mm × 50 mm analytical column. A gradient elution was used with flow rate of 0.6 mL/min, injection volume of 5 μL, and column temperature of 40 ºC (Table 2).
Table 2. LC conditions.
Mass Spectrometry: SCIEX Triple Quad 3500 LC-MS/MS System was operated using the ESI source in positive ion mode.
Ion source parameters were:
- IS voltage: 5500 V
- Curtain gas: 35 psi
- Atomizing gas GS1: 50 psi
- Auxiliary gas GS2: 55 psi
- Source temperature (TEM): 500 ℃
- Collision gas CAD: 7
Two ion pairs were monitored for the sodium picosulfate; both using the precursor ion of 438 m/z; the quantifier product ion was 183.9 m/z and the qualifier product ion was 277.9 m/z.
Sensitivity and linear range
The detection concentration of this method is as low as 0.4 ng/mL (Figure 2), and it has a good linear dynamic range across a concentration range of 0.4~1000 ng/mL, with a correlation coefficient is r>0.999 (Figure 3). There is no residual signal found in a blank injection performed right after an injection of the 1000 ng/mL high concentration point.
Figure 2. Typical chromatogram of sodium picosulfate. Signal obtained in sweet plum matrix for sodium picosulfate at 60 ng/mL concentration.
Figure 3. Standard curve of sodium picosulfate. Good linear dynamic range was obtained, from 0.4~1000 ng/mL with good correlation coefficient r>0.999.
Recovery
Taking the plum matrix as an example, the repeatability of the compound at three different concentration points of 6, 60 and 600 ng/mL was investigated. The results are shown in Table 3. Three spiked samples with different concentrations were injected for 6 consecutive times. The peak area RSD was within 2% except for the low concentration point of 6 ng/mL, which was 4.78%.
Table 3. Repeatability of sodium picosulfate in plum matrix.
Figure 4. Chromatograms of five sample extracts. No peaks for sodium picosulfate were detected in the five food samples tested, plum, candy, solid beverage, Huamei and jelly.
Conclusions
Here, the SCIEX Triple Quad 3500 LC-MS/MS System was used to establish a quantitative method for sodium picosulfate in food. This method has high sensitivity, good repeatability, and a wide linear dynamic range of 0.4~1000 ng/mL. The test substance has no obvious matrix effect in 5 different food matrices. The elution time of the method is only 4 min, which is very suitable for high throughput analysis of food samples.
References
- Announcement of the General Administration of Market Supervision on Issuing the Supplementary Inspection Method of Food for the Determination of Sodium Picosulfate in Food. BJS 201911.