Development and validation of an HPTLC method for simultaneous determination of gliclazide and sitagliptin phosphate monohydrate in tablets

In the world of medicine, managing blood sugar levels for people with type 2 diabetes often requires a team approach. Just as a single tool might not fix a complex machine, a single medication sometimes cannot keep blood sugar in check. Doctors frequently prescribe a combination of two different drugs to tackle the problem from two angles at once. One drug, called gliclazide, is a sulfonylurea antidiabetic used in the management of type 2 diabetes mellitus. The other, sitagliptin, is a dipeptidyl peptidase-4 (DPP-4) inhibitor. When these two medicines are mixed into a single pill, it makes treatment easier for patients, but it creates a new challenge for the scientists who make sure the pills are safe and effective. They must be able to prove that every tablet contains exactly the right amount of both drugs, with no extra or missing ingredients. To do this, they need a way to separate the two substances and measure them precisely, even when they are mixed together in a complex tablet.

Researchers at Laxminarayandev College of Pharmacy in Gujarat, India, set out to create a better way to perform this check. They developed a new testing method that uses a technique called high-performance thin-layer chromatography. Imagine a flat, smooth board coated with a special layer of silica gel, similar to the material found in the desiccant packets that keep shoes dry. The scientists placed tiny amounts of the drug mixture onto this board. They then let a liquid mixture, acting as a mobile carrier, travel up the board. As the liquid moved, it carried the two drugs with it. Because the two drugs interact with the board and the liquid in slightly different ways, they traveled at different speeds and stopped at different distances. This separation allowed the researchers to see the two drugs as distinct, separate bands on the board rather than a single, blurry mixture.

The team carefully adjusted the ingredients of the liquid carrier, mixing methanol, ethyl acetate, toluene, and a small amount of ammonia in specific proportions. They found that this particular blend allowed the drugs to separate cleanly. One drug stopped near the bottom third of the board, while the other traveled much further up, leaving a clear gap between them. Once separated, the scientists used a special scanner to measure how much light the drugs absorbed at a specific color of light. This measurement told them exactly how much of each drug was present in the sample. The method proved to be highly sensitive, capable of detecting even the tiniest traces of the medicines, down to amounts as small as thirty-two nanograms for one drug and sixty-nine nanograms for the other. A nanogram is a billionth of a gram, a scale so small that it is difficult to visualize without a reference point; it is roughly equivalent to the weight of a single grain of dust compared to the weight of a large truck.

To ensure their new method was trustworthy, the researchers put it through a series of rigorous tests. They checked if the results were consistent by running the same sample multiple times and found that the numbers stayed very close together every time. They tested the method on different days and with different operators to make sure it worked reliably under normal laboratory conditions. They also checked the accuracy by adding known amounts of the drugs to the samples and seeing if the method could find them. The results showed that the method could recover between ninety-nine and one hundred and two percent of the drugs, which is an excellent level of precision. They even tested the method's durability by making small, deliberate changes to the liquid mixture and the timing of the experiment, and the results remained stable, proving the method was robust against minor variations.

Finally, the team applied their new technique to a real-world product: a tablet on the market called Cyblex S 60 XR. This tablet is supposed to contain a specific amount of both gliclazide and sitagliptin. When the researchers analyzed these tablets, they found that the actual amounts of medicine inside matched the labels almost perfectly. The test showed that the tablets contained ninety-nine point four three percent of the labeled amount of gliclazide and ninety-nine point nine zero percent of the labeled amount of sitagliptin. These findings confirmed that the new method is not only scientifically sound but also practical for everyday use in quality control labs. It offers a fast, reliable, and cost-effective way to ensure that patients receive the correct dosage of their life-saving medication, providing a solid foundation for the safety of this common diabetes treatment.